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Benefits and pitfalls of secondary antibodies: why choosing the right secondary is of primary importance.
Simultaneous labeling of multiple targets in a single sample, or multiplexing, is a powerful approach to directly compare the amount, localization and/or molecular properties of different targets in the same sample. Here we highlight the robust reliability of the simultaneous use of multiple mouse monoclonal antibodies (mAbs) of different immunoglobulin G (IgG) subclasses in a wide variety of multiplexing applications employing anti-mouse IgG subclass-specific secondary antibodies (2°Abs). We also describe the unexpected finding that IgG subclass-specific 2°Abs are superior to general anti-mouse IgG 2 °Abs in every tested application in which mouse mAbs were used. This was due to a detection bias of general anti-mouse IgG-specific 2°Abs against mAbs of the most common mouse IgG subclass, IgG1, and to a lesser extent IgG2b mAbs. Thus, when using any of numerous mouse mAbs available through commercial and non-profit sources, for cleaner and more robust results each mAb should be detected with its respective IgG subclass-specific 2°Ab and not a general anti-mouse IgG-specific 2°Ab.
Authors: Maria Chiara G. Monaco, Dragan Maric, Alexandra Bandeian, Emily Leibovitch, Wan Yang, Eugene O. Major.
Published: 12-20-2012
Differentiation of human neural progenitors into neuronal and glial cell types offers a model to study and compare molecular regulation of neural cell lineage development. In vitro expansion of neural progenitors from fetal CNS tissue has been well characterized. Despite the identification and isolation of glial progenitors from adult human sub-cortical white matter and development of various culture conditions to direct differentiation of fetal neural progenitors into myelin producing oligodendrocytes, acquiring sufficient human oligodendrocytes for in vitro experimentation remains difficult. Differentiation of galactocerebroside+ (GalC) and O4+ oligodendrocyte precursor or progenitor cells (OPC) from neural precursor cells has been reported using second trimester fetal brain. However, these cells do not proliferate in the absence of support cells including astrocytes and neurons, and are lost quickly over time in culture. The need remains for a culture system to produce cells of the oligodendrocyte lineage suitable for in vitro experimentation. Culture of primary human oligodendrocytes could, for example, be a useful model to study the pathogenesis of neurotropic infectious agents like the human polyomavirus, JCV, that in vivo infects those cells. These cultured cells could also provide models of other demyelinating diseases of the central nervous system (CNS). Primary, human fetal brain-derived, multipotential neural progenitor cells proliferate in vitro while maintaining the capacity to differentiate into neurons (progenitor-derived neurons, PDN) and astrocytes (progenitor-derived astrocytes, PDA) This study shows that neural progenitors can be induced to differentiate through many of the stages of oligodendrocytic lineage development (progenitor-derived oligodendrocytes, PDO). We culture neural progenitor cells in DMEM-F12 serum-free media supplemented with basic fibroblast growth factor (bFGF), platelet derived growth factor (PDGF-AA), Sonic hedgehog (Shh), neurotrophic factor 3 (NT-3), N-2 and triiodothyronine (T3). The cultured cells are passaged at 2.5e6 cells per 75cm flasks approximately every seven days. Using these conditions, the majority of the cells in culture maintain a morphology characterized by few processes and express markers of pre-oligodendrocyte cells, such as A2B5 and O-4. When we remove the four growth factors (GF) (bFGF, PDGF-AA, Shh, NT-3) and add conditioned media from PDN, the cells start to acquire more processes and express markers specific of oligodendrocyte differentiation, such as GalC and myelin basic protein (MBP). We performed phenotypic characterization using multicolor flow cytometry to identify unique markers of oligodendrocyte.
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Methods for Quantitative Detection of Antibody-induced Complement Activation on Red Blood Cells
Authors: Elisabeth M. Meulenbroek, Diana Wouters, Sacha Zeerleder.
Institutions: University of Amsterdam, University of Amsterdam.
Antibodies against red blood cells (RBCs) can lead to complement activation resulting in an accelerated clearance via complement receptors in the liver (extravascular hemolysis) or leading to intravascular lysis of RBCs. Alloantibodies (e.g. ABO) or autoantibodies to RBC antigens (as seen in autoimmune hemolytic anemia, AIHA) leading to complement activation are potentially harmful and can be - especially when leading to intravascular lysis - fatal1. Currently, complement activation due to (auto)-antibodies on RBCs is assessed in vitro by using the Coombs test reflecting complement deposition on RBC or by a nonquantitative hemolytic assay reflecting RBC lysis1-4. However, to assess the efficacy of complement inhibitors, it is mandatory to have quantitative techniques. Here we describe two such techniques. First, an assay to detect C3 and C4 deposition on red blood cells that is induced by antibodies in patient serum is presented. For this, FACS analysis is used with fluorescently labeled anti-C3 or anti-C4 antibodies. Next, a quantitative hemolytic assay is described. In this assay, complement-mediated hemolysis induced by patient serum is measured making use of spectrophotometric detection of the released hemoglobin. Both of these assays are very reproducible and quantitative, facilitating studies of antibody-induced complement activation.
Immunology, Issue 83, Complement, red blood cells, auto-immune hemolytic anemia, hemolytic assay, FACS, antibodies, C1-inhibitor
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Measurement of Antibody Effects on Cellular Function of Isolated Cardiomyocytes
Authors: Lars G. Eckerle, Stephan B. Felix, Lars R. Herda.
Institutions: University Medicine Greifswald.
Dilated cardiomyopathy (DCM) is one of the main causes for heart failure in younger adults1. Although genetic disposition and exposition to toxic substances are known causes for this disease in about one third of the patients, the origin of DCM remains largely unclear. In a substantial number of these patients, autoantibodies against cardiac epitopes have been detected and are suspected to play a pivotal role in the onset and progression of the disease2,3. The importance of cardiac autoantibodies is underlined by a hemodynamic improvement observed in DCM patients after elimination of autoantibodies by immunoadsorption3-5. A variety of specific antigens have already been identified2,3 and antibodies against these targets may be detected by immunoassays. However, these assays cannot discriminate between stimulating (and therefore functionally effective) and blocking autoantibodies. There is increasing evidence that this distinction is crucial6,7. It can also be assumed that the targets for a number of cardiotropic antibodies are still unidentified and therefore cannot be detected by immunoassays. Therefore, we established a method for the detection of functionally active cardiotropic antibodies, independent of their respective antigen. The background for the method is the high homology usually observed for functional regions of cardiac proteins in between mammals8,9. This suggests that cardiac antibodies directed against human antigens will cross-react with non-human target cells, which allows testing of IgG from DCM patients on adult rat cardiomyocytes. Our method consists of 3 steps: first, IgG is isolated from patient plasma using sepharose coupled anti-IgG antibodies obtained from immunoadsorption columns (PlasmaSelect, Teterow, Germany). Second, adult cardiomyocytes are isolated by collagenase perfusion in a Langendorff perfusion apparatus using a protocol modified from previous works10,11. The obtained cardiomyocytes are attached to laminin-coated chambered coverglasses and stained with Fura-2, a calcium-selective fluorescent dye which can be easily brought into the cell to observe intracellular calcium (Ca2+) contents12. In the last step, the effect of patient IgG on the cell shortening and Ca2+ transients of field stimulated cardiomyocytes is monitored online using a commercial myocyte calcium and contractility monitoring system (IonOptix, Milton, MA, USA) connected to a standard inverse fluorescent microscope.
Immunology, Issue 73, Medicine, Cellular Biology, Molecular Biology, Biomedical Engineering, Physiology, Anatomy, Cardiology, cardiomyocytes, cell shortening, intracellular Ca2+, Fura-2, antibodies, dilated cardiomyopathy, DCM, IgG, cardiac proteins, Langendorff perfusion, electrode, immunoassay, assay, cell culture, animal model
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Immuno-fluorescence Assay of Leptospiral Surface-exposed Proteins
Authors: Marija Pinne, David Haake.
Institutions: University of California, Los Angeles, Veterans Affairs Greater Los Angeles Healthcare System, University of California Los Angeles (UCLA), Veterans Affairs Greater Los Angeles Health Care System.
Bacterial surface proteins are involved in direct contact with host cells and in uptake of nutrients from the environment 1. For this reason, cellular localization can provide insights into the functional role of bacterial proteins. Surface localization of bacterial proteins is a key step towards identification of virulence factors involved in mechanisms of pathogenicity. Methods for fractionating leptospiral membranes 2-5 may be selective for a certain class of outer-membrane proteins (OMPs), such as lipoproteins vs. transmembrane OMPs, and therefore lead to misclassification. This likely is due to structural differences and how they are associated to the outer membrane. Lipoproteins are associated with membranes via a hydrophobic interaction between the N-terminal lipid moiety (three fatty acids) and the lipid bilayer phospholipids 6, 7. In contrast, transmembrane OMPs are typically integrated into the lipid bilayer by amphipathic β-sheets arranged in a barrel-like structure 8, 9. In addition, presence of a protein in the outer-membrane does not necessarily guarantee that the protein or its domains are exposed on the surface. Spirochetal outer membranes are known to be fragile and therefore necessitate methods involving gentle manipulation of cells and inclusion of sub-surface protein controls to assess the integrity of the outer membrane. Here, we present an immunofluorescence assay (IFA) method to directly assess surface exposure of proteins on intact leptospires. This method is based on recognition of leptospiral surface proteins by antigen-specific antibodies. Herein, antibodies specific for OmpL5410 are detetcted aftero binding to native, surface exposed epitopes. Comparison of antibody reactivity to intact versus permeabilized cells enables evaluation of cellular distribution and whether or not a protein is selectively present on leptospiral surface. The integrity of outer membrane should be assessed using antibody to one or more subsurface proteins, preferably located in the periplasm. The surface IFA method can be used to analyze surface exposure of any leptospiral protein to which specific antibodies are available. Both the usefulness and limitation of the method depends on whether the antibodies employed are able to bind to native epitopes. Since antibodies often are raised against recombinant proteins, epitopes of native, surface-exposed proteins may not be recognized. Nevertheless, the surface IFA method is a valuable tool for studying components of intact bacterial surfaces. This method can be applied not only for leptospires but also other spirochetes and gram-negative bacteria. For stronger conclusions regarding surface-exposure of OMPs, a comprehensive approach involving several cell localization methods is recommended 10.
Immunology, Issue 53, Molecular Biology, Leptospira, intact cells, outer membrane, surface-exposed proteins, surface immuno-fluorescence
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Conformational Evaluation of HIV-1 Trimeric Envelope Glycoproteins Using a Cell-based ELISA Assay
Authors: Maxime Veillette, Mathieu Coutu, Jonathan Richard, Laurie-Anne Batraville, Anik Désormeaux, Michel Roger, Andrés Finzi.
Institutions: Université de Montréal.
HIV-1 envelope glycoproteins (Env) mediate viral entry into target cells and are essential to the infectious cycle. Understanding how those glycoproteins are able to fuel the fusion process through their conformational changes could lead to the design of better, more effective immunogens for vaccine strategies. Here we describe a cell-based ELISA assay that allows studying the recognition of trimeric HIV-1 Env by monoclonal antibodies. Following expression of HIV-1 trimeric Env at the surface of transfected cells, conformation specific anti-Env antibodies are incubated with the cells. A horseradish peroxidase-conjugated secondary antibody and a simple chemiluminescence reaction are then used to detect bound antibodies. This system is highly flexible and can detect Env conformational changes induced by soluble CD4 or cellular proteins. It requires minimal amount of material and no highly-specialized equipment or know-how. Thus, this technique can be established for medium to high throughput screening of antigens and antibodies, such as newly-isolated antibodies.
Infectious Diseases, Issue 91, HIV-1, envelope glycoproteins, gp120, gp41, neutralizing antibodies, non-neutralizing antibodies, CD4, cell-based ELISA
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A Guide to Modern Quantitative Fluorescent Western Blotting with Troubleshooting Strategies
Authors: Samantha L. Eaton, Maica Llavero Hurtado, Karla J. Oldknow, Laura C. Graham, Thomas W. Marchant, Thomas H. Gillingwater, Colin Farquharson, Thomas M. Wishart.
Institutions: University of Edinburgh, University of Edinburgh, University of Edinburgh, University of Edinburgh.
The late 1970s saw the first publicly reported use of the western blot, a technique for assessing the presence and relative abundance of specific proteins within complex biological samples. Since then, western blotting methodology has become a common component of the molecular biologists experimental repertoire. A cursory search of PubMed using the term “western blot” suggests that in excess of two hundred and twenty thousand published manuscripts have made use of this technique by the year 2014. Importantly, the last ten years have seen technical imaging advances coupled with the development of sensitive fluorescent labels which have improved sensitivity and yielded even greater ranges of linear detection. The result is a now truly Quantifiable Fluorescence based Western Blot (QFWB) that allows biologists to carry out comparative expression analysis with greater sensitivity and accuracy than ever before. Many “optimized” western blotting methodologies exist and are utilized in different laboratories. These often prove difficult to implement due to the requirement of subtle but undocumented procedural amendments. This protocol provides a comprehensive description of an established and robust QFWB method, complete with troubleshooting strategies.
Basic Protocols, Issue 93, western blotting, fluorescent, LI-COR, protein, quantitative analysis, loading control
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Visualizing Neuroblast Cytokinesis During C. elegans Embryogenesis
Authors: Denise Wernike, Chloe van Oostende, Alisa Piekny.
Institutions: Concordia University.
This protocol describes the use of fluorescence microscopy to image dividing cells within developing Caenorhabditis elegans embryos. In particular, this protocol focuses on how to image dividing neuroblasts, which are found underneath the epidermal cells and may be important for epidermal morphogenesis. Tissue formation is crucial for metazoan development and relies on external cues from neighboring tissues. C. elegans is an excellent model organism to study tissue morphogenesis in vivo due to its transparency and simple organization, making its tissues easy to study via microscopy. Ventral enclosure is the process where the ventral surface of the embryo is covered by a single layer of epithelial cells. This event is thought to be facilitated by the underlying neuroblasts, which provide chemical guidance cues to mediate migration of the overlying epithelial cells. However, the neuroblasts are highly proliferative and also may act as a mechanical substrate for the ventral epidermal cells. Studies using this experimental protocol could uncover the importance of intercellular communication during tissue formation, and could be used to reveal the roles of genes involved in cell division within developing tissues.
Neuroscience, Issue 85, C. elegans, morphogenesis, cytokinesis, neuroblasts, anillin, microscopy, cell division
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Polymerase Chain Reaction: Basic Protocol Plus Troubleshooting and Optimization Strategies
Authors: Todd C. Lorenz.
Institutions: University of California, Los Angeles .
In the biological sciences there have been technological advances that catapult the discipline into golden ages of discovery. For example, the field of microbiology was transformed with the advent of Anton van Leeuwenhoek's microscope, which allowed scientists to visualize prokaryotes for the first time. The development of the polymerase chain reaction (PCR) is one of those innovations that changed the course of molecular science with its impact spanning countless subdisciplines in biology. The theoretical process was outlined by Keppe and coworkers in 1971; however, it was another 14 years until the complete PCR procedure was described and experimentally applied by Kary Mullis while at Cetus Corporation in 1985. Automation and refinement of this technique progressed with the introduction of a thermal stable DNA polymerase from the bacterium Thermus aquaticus, consequently the name Taq DNA polymerase. PCR is a powerful amplification technique that can generate an ample supply of a specific segment of DNA (i.e., an amplicon) from only a small amount of starting material (i.e., DNA template or target sequence). While straightforward and generally trouble-free, there are pitfalls that complicate the reaction producing spurious results. When PCR fails it can lead to many non-specific DNA products of varying sizes that appear as a ladder or smear of bands on agarose gels. Sometimes no products form at all. Another potential problem occurs when mutations are unintentionally introduced in the amplicons, resulting in a heterogeneous population of PCR products. PCR failures can become frustrating unless patience and careful troubleshooting are employed to sort out and solve the problem(s). This protocol outlines the basic principles of PCR, provides a methodology that will result in amplification of most target sequences, and presents strategies for optimizing a reaction. By following this PCR guide, students should be able to: ● Set up reactions and thermal cycling conditions for a conventional PCR experiment ● Understand the function of various reaction components and their overall effect on a PCR experiment ● Design and optimize a PCR experiment for any DNA template ● Troubleshoot failed PCR experiments
Basic Protocols, Issue 63, PCR, optimization, primer design, melting temperature, Tm, troubleshooting, additives, enhancers, template DNA quantification, thermal cycler, molecular biology, genetics
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Analysis of the Epithelial Damage Produced by Entamoeba histolytica Infection
Authors: Abigail Betanzos, Michael Schnoor, Rosario Javier-Reyna, Guillermina García-Rivera, Cecilia Bañuelos, Jonnatan Pais-Morales, Esther Orozco.
Institutions: Center for Research and Advanced Studies of the National Polytechnic Institute, Center for Research and Advanced Studies of the National Polytechnic Institute, Center for Research and Advanced Studies of the National Polytechnic Institute.
Entamoeba histolytica is the causative agent of human amoebiasis, a major cause of diarrhea and hepatic abscess in tropical countries. Infection is initiated by interaction of the pathogen with intestinal epithelial cells. This interaction leads to disruption of intercellular structures such as tight junctions (TJ). TJ ensure sealing of the epithelial layer to separate host tissue from gut lumen. Recent studies provide evidence that disruption of TJ by the parasitic protein EhCPADH112 is a prerequisite for E. histolytica invasion that is accompanied by epithelial barrier dysfunction. Thus, the analysis of molecular mechanisms involved in TJ disassembly during E. histolytica invasion is of paramount importance to improve our understanding of amoebiasis pathogenesis. This article presents an easy model that allows the assessment of initial host-pathogen interactions and the parasite invasion potential. Parameters to be analyzed include transepithelial electrical resistance, interaction of EhCPADH112 with epithelial surface receptors, changes in expression and localization of epithelial junctional markers and localization of parasite molecules within epithelial cells.
Immunology, Issue 88, Entamoeba histolytica, EhCPADH112, cell adhesion, MDCK, Caco-2, tight junction disruption, amoebiasis, host-pathogen interaction, infection model, actin cytoskeleton
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Quantifying Synapses: an Immunocytochemistry-based Assay to Quantify Synapse Number
Authors: Dominic M. Ippolito, Cagla Eroglu.
Institutions: Duke University, Duke University.
One of the most important goals in neuroscience is to understand the molecular cues that instruct early stages of synapse formation. As such it has become imperative to develop objective approaches to quantify changes in synaptic connectivity. Starting from sample fixation, this protocol details how to quantify synapse number both in dissociated neuronal culture and in brain sections using immunocytochemistry. Using compartment-specific antibodies, we label presynaptic terminals as well as sites of postsynaptic specialization. We define synapses as points of colocalization between the signals generated by these markers. The number of these colocalizations is quantified using a plug in Puncta Analyzer (written by Bary Wark, available upon request, under the ImageJ analysis software platform. The synapse assay described in this protocol can be applied to any neural tissue or culture preparation for which you have selective pre- and postsynaptic markers. This synapse assay is a valuable tool that can be widely utilized in the study of synaptic development.
Neuroscience, Issue 45, synapse, immunocytochemistry, brain, neuron, astrocyte
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Aseptic Laboratory Techniques: Plating Methods
Authors: Erin R. Sanders.
Institutions: University of California, Los Angeles .
Microorganisms are present on all inanimate surfaces creating ubiquitous sources of possible contamination in the laboratory. Experimental success relies on the ability of a scientist to sterilize work surfaces and equipment as well as prevent contact of sterile instruments and solutions with non-sterile surfaces. Here we present the steps for several plating methods routinely used in the laboratory to isolate, propagate, or enumerate microorganisms such as bacteria and phage. All five methods incorporate aseptic technique, or procedures that maintain the sterility of experimental materials. Procedures described include (1) streak-plating bacterial cultures to isolate single colonies, (2) pour-plating and (3) spread-plating to enumerate viable bacterial colonies, (4) soft agar overlays to isolate phage and enumerate plaques, and (5) replica-plating to transfer cells from one plate to another in an identical spatial pattern. These procedures can be performed at the laboratory bench, provided they involve non-pathogenic strains of microorganisms (Biosafety Level 1, BSL-1). If working with BSL-2 organisms, then these manipulations must take place in a biosafety cabinet. Consult the most current edition of the Biosafety in Microbiological and Biomedical Laboratories (BMBL) as well as Material Safety Data Sheets (MSDS) for Infectious Substances to determine the biohazard classification as well as the safety precautions and containment facilities required for the microorganism in question. Bacterial strains and phage stocks can be obtained from research investigators, companies, and collections maintained by particular organizations such as the American Type Culture Collection (ATCC). It is recommended that non-pathogenic strains be used when learning the various plating methods. By following the procedures described in this protocol, students should be able to: ● Perform plating procedures without contaminating media. ● Isolate single bacterial colonies by the streak-plating method. ● Use pour-plating and spread-plating methods to determine the concentration of bacteria. ● Perform soft agar overlays when working with phage. ● Transfer bacterial cells from one plate to another using the replica-plating procedure. ● Given an experimental task, select the appropriate plating method.
Basic Protocols, Issue 63, Streak plates, pour plates, soft agar overlays, spread plates, replica plates, bacteria, colonies, phage, plaques, dilutions
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The Fastest Western in Town: A Contemporary Twist on the Classic Western Blot Analysis
Authors: Jillian M. Silva, Martin McMahon.
Institutions: University of California, San Francisco.
The Western blot techniques that were originally established in the late 1970s are still actively utilized today. However, this traditional method of Western blotting has several drawbacks that include low quality resolution, spurious bands, decreased sensitivity, and poor protein integrity. Recent advances have drastically improved numerous aspects of the standard Western blot protocol to produce higher qualitative and quantitative data. The Bis-Tris gel system, an alternative to the conventional Laemmli system, generates better protein separation and resolution, maintains protein integrity, and reduces electrophoresis to a 35 min run time. Moreover, the iBlot dry blotting system, dramatically improves the efficacy and speed of protein transfer to the membrane in 7 min, which is in contrast to the traditional protein transfer methods that are often more inefficient with lengthy transfer times. In combination with these highly innovative modifications, protein detection using infrared fluorescent imaging results in higher-quality, more accurate and consistent data compared to the standard Western blotting technique of chemiluminescence. This technology can simultaneously detect two different antigens on the same membrane by utilizing two-color near-infrared dyes that are visualized in different fluorescent channels. Furthermore, the linearity and broad dynamic range of fluorescent imaging allows for the precise quantification of both strong and weak protein bands. Thus, this protocol describes the key improvements to the classic Western blotting method, in which these advancements significantly increase the quality of data while greatly reducing the performance time of this experiment.
Basic Protocol, Issue 84, Western blot, Bis-Tris, electrophoresis, dry blotting, protein transfer, infrared, Fluorescence, quantification, Antibody, Protein
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The Use of Reverse Phase Protein Arrays (RPPA) to Explore Protein Expression Variation within Individual Renal Cell Cancers
Authors: Fiach C. O'Mahony, Jyoti Nanda, Alexander Laird, Peter Mullen, Helen Caldwell, Ian M. Overton, Lel Eory, Marie O'Donnell, Dana Faratian, Thomas Powles, David J. Harrison, Grant D. Stewart.
Institutions: University of Edinburgh, University of St Andrews, University of Edinburgh, University of Edinburgh, Western General Hospital, University of Edinburgh, Queen Mary University of London.
Currently there is no curative treatment for metastatic clear cell renal cell cancer, the commonest variant of the disease. A key factor in this treatment resistance is thought to be the molecular complexity of the disease 1. Targeted therapy such as the tyrosine kinase inhibitor (TKI)-sunitinib have been utilized, but only 40% of patients will respond, with the overwhelming majority of these patients relapsing within 1 year 2. As such the question of intrinsic and acquired resistance in renal cell cancer patients is highly relevant 3. In order to study resistance to TKIs, with the ultimate goal of developing effective, personalized treatments, sequential tissue after a specific period of targeted therapy is required, an approach which had proved successful in chronic myeloid leukaemia 4. However the application of such a strategy in renal cell carcinoma is complicated by the high level of both inter- and intratumoral heterogeneity, which is a feature of renal cell carcinoma5,6 as well as other solid tumors 7. Intertumoral heterogeneity due to transcriptomic and genetic differences is well established even in patients with similar presentation, stage and grade of tumor. In addition it is clear that there is great morphological (intratumoral) heterogeneity in RCC, which is likely to represent even greater molecular heterogeneity. Detailed mapping and categorization of RCC tumors by combined morphological analysis and Fuhrman grading allows the selection of representative areas for proteomic analysis. Protein based analysis of RCC8 is attractive due to its widespread availability in pathology laboratories; however, its application can be problematic due to the limited availability of specific antibodies 9. Due to the dot blot nature of the Reverse Phase Protein Arrays (RPPA), antibody specificity must be pre-validated; as such strict quality control of antibodies used is of paramount importance. Despite this limitation the dot blot format does allow assay miniaturization, allowing for the printing of hundreds of samples onto a single nitrocellulose slide. Printed slides can then be analyzed in a similar fashion to Western analysis with the use of target specific primary antibodies and fluorescently labelled secondary antibodies, allowing for multiplexing. Differential protein expression across all the samples on a slide can then be analyzed simultaneously by comparing the relative level of fluorescence in a more cost-effective and high-throughput manner.
Cancer Biology, Issue 71, Bioengineering, Medicine, Biomedical Engineering, Cellular Biology, Molecular Biology, Genetics, Pathology, Oncology, Proteins, Early Detection of Cancer, Translational Medical Research, RPPA, RCC, Heterogeneity, Proteomics, Tumor Grade, intertumoral, tumor, metastatic, carcinoma, renal cancer, clear cell renal cell cancer, cancer, assay
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Polymalic Acid-based Nano Biopolymers for Targeting of Multiple Tumor Markers: An Opportunity for Personalized Medicine?
Authors: Julia Y. Ljubimova, Hui Ding, Jose Portilla-Arias, Rameshwar Patil, Pallavi R. Gangalum, Alexandra Chesnokova, Satoshi Inoue, Arthur Rekechenetskiy, Tala Nassoura, Keith L. Black, Eggehard Holler.
Institutions: Cedars-Sinai Medical Center.
Tumors with similar grade and morphology often respond differently to the same treatment because of variations in molecular profiling. To account for this diversity, personalized medicine is developed for silencing malignancy associated genes. Nano drugs fit these needs by targeting tumor and delivering antisense oligonucleotides for silencing of genes. As drugs for the treatment are often administered repeatedly, absence of toxicity and negligible immune response are desirable. In the example presented here, a nano medicine is synthesized from the biodegradable, non-toxic and non-immunogenic platform polymalic acid by controlled chemical ligation of antisense oligonucleotides and tumor targeting molecules. The synthesis and treatment is exemplified for human Her2-positive breast cancer using an experimental mouse model. The case can be translated towards synthesis and treatment of other tumors.
Chemistry, Issue 88, Cancer treatment, personalized medicine, polymalic acid, nanodrug, biopolymer, targeting, host compatibility, biodegradability
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High-throughput Flow Cytometry Cell-based Assay to Detect Antibodies to N-Methyl-D-aspartate Receptor or Dopamine-2 Receptor in Human Serum
Authors: Mazen Amatoury, Vera Merheb, Jessica Langer, Xin Maggie Wang, Russell Clive Dale, Fabienne Brilot.
Institutions: The University of Sydney, Westmead Millennium Institute for Medical Research.
Over the recent years, antibodies against surface and conformational proteins involved in neurotransmission have been detected in autoimmune CNS diseases in children and adults. These antibodies have been used to guide diagnosis and treatment. Cell-based assays have improved the detection of antibodies in patient serum. They are based on the surface expression of brain antigens on eukaryotic cells, which are then incubated with diluted patient sera followed by fluorochrome-conjugated secondary antibodies. After washing, secondary antibody binding is then analyzed by flow cytometry. Our group has developed a high-throughput flow cytometry live cell-based assay to reliably detect antibodies against specific neurotransmitter receptors. This flow cytometry method is straight forward, quantitative, efficient, and the use of a high-throughput sampler system allows for large patient cohorts to be easily assayed in a short space of time. Additionally, this cell-based assay can be easily adapted to detect antibodies to many different antigenic targets, both from the central nervous system and periphery. Discovering additional novel antibody biomarkers will enable prompt and accurate diagnosis and improve treatment of immune-mediated disorders.
Medicine, Issue 81, Flow cytometry, cell-based assay, autoantibody, high-throughput sampler, autoimmune CNS disease
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Optimized Negative Staining: a High-throughput Protocol for Examining Small and Asymmetric Protein Structure by Electron Microscopy
Authors: Matthew Rames, Yadong Yu, Gang Ren.
Institutions: The Molecular Foundry.
Structural determination of proteins is rather challenging for proteins with molecular masses between 40 - 200 kDa. Considering that more than half of natural proteins have a molecular mass between 40 - 200 kDa1,2, a robust and high-throughput method with a nanometer resolution capability is needed. Negative staining (NS) electron microscopy (EM) is an easy, rapid, and qualitative approach which has frequently been used in research laboratories to examine protein structure and protein-protein interactions. Unfortunately, conventional NS protocols often generate structural artifacts on proteins, especially with lipoproteins that usually form presenting rouleaux artifacts. By using images of lipoproteins from cryo-electron microscopy (cryo-EM) as a standard, the key parameters in NS specimen preparation conditions were recently screened and reported as the optimized NS protocol (OpNS), a modified conventional NS protocol 3 . Artifacts like rouleaux can be greatly limited by OpNS, additionally providing high contrast along with reasonably high‐resolution (near 1 nm) images of small and asymmetric proteins. These high-resolution and high contrast images are even favorable for an individual protein (a single object, no average) 3D reconstruction, such as a 160 kDa antibody, through the method of electron tomography4,5. Moreover, OpNS can be a high‐throughput tool to examine hundreds of samples of small proteins. For example, the previously published mechanism of 53 kDa cholesteryl ester transfer protein (CETP) involved the screening and imaging of hundreds of samples 6. Considering cryo-EM rarely successfully images proteins less than 200 kDa has yet to publish any study involving screening over one hundred sample conditions, it is fair to call OpNS a high-throughput method for studying small proteins. Hopefully the OpNS protocol presented here can be a useful tool to push the boundaries of EM and accelerate EM studies into small protein structure, dynamics and mechanisms.
Environmental Sciences, Issue 90, small and asymmetric protein structure, electron microscopy, optimized negative staining
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Viability Assays for Cells in Culture
Authors: Jessica M. Posimo, Ajay S. Unnithan, Amanda M. Gleixner, Hailey J. Choi, Yiran Jiang, Sree H. Pulugulla, Rehana K. Leak.
Institutions: Duquesne University.
Manual cell counts on a microscope are a sensitive means of assessing cellular viability but are time-consuming and therefore expensive. Computerized viability assays are expensive in terms of equipment but can be faster and more objective than manual cell counts. The present report describes the use of three such viability assays. Two of these assays are infrared and one is luminescent. Both infrared assays rely on a 16 bit Odyssey Imager. One infrared assay uses the DRAQ5 stain for nuclei combined with the Sapphire stain for cytosol and is visualized in the 700 nm channel. The other infrared assay, an In-Cell Western, uses antibodies against cytoskeletal proteins (α-tubulin or microtubule associated protein 2) and labels them in the 800 nm channel. The third viability assay is a commonly used luminescent assay for ATP, but we use a quarter of the recommended volume to save on cost. These measurements are all linear and correlate with the number of cells plated, but vary in sensitivity. All three assays circumvent time-consuming microscopy and sample the entire well, thereby reducing sampling error. Finally, all of the assays can easily be completed within one day of the end of the experiment, allowing greater numbers of experiments to be performed within short timeframes. However, they all rely on the assumption that cell numbers remain in proportion to signal strength after treatments, an assumption that is sometimes not met, especially for cellular ATP. Furthermore, if cells increase or decrease in size after treatment, this might affect signal strength without affecting cell number. We conclude that all viability assays, including manual counts, suffer from a number of caveats, but that computerized viability assays are well worth the initial investment. Using all three assays together yields a comprehensive view of cellular structure and function.
Cellular Biology, Issue 83, In-cell Western, DRAQ5, Sapphire, Cell Titer Glo, ATP, primary cortical neurons, toxicity, protection, N-acetyl cysteine, hormesis
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Systematic Analysis of In Vitro Cell Rolling Using a Multi-well Plate Microfluidic System
Authors: Oren Levy, Priya Anandakumaran, Jessica Ngai, Rohit Karnik, Jeffrey M. Karp.
Institutions: Brigham and Women's Hospital, Brigham and Women's Hospital, Harvard University, Harvard University, Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology.
A major challenge for cell-based therapy is the inability to systemically target a large quantity of viable cells with high efficiency to tissues of interest following intravenous or intraarterial infusion. Consequently, increasing cell homing is currently studied as a strategy to improve cell therapy. Cell rolling on the vascular endothelium is an important step in the process of cell homing and can be probed in-vitro using a parallel plate flow chamber (PPFC). However, this is an extremely tedious, low throughput assay, with poorly controlled flow conditions. Instead, we used a multi-well plate microfluidic system that enables study of cellular rolling properties in a higher throughput under precisely controlled, physiologically relevant shear flow1,2. In this paper, we show how the rolling properties of HL-60 (human promyelocytic leukemia) cells on P- and E-selectin-coated surfaces as well as on cell monolayer-coated surfaces can be readily examined. To better simulate inflammatory conditions, the microfluidic channel surface was coated with endothelial cells (ECs), which were then activated with tumor necrosis factor-α (TNF-α), significantly increasing interactions with HL-60 cells under dynamic conditions. The enhanced throughput and integrated multi-parameter software analysis platform, that permits rapid analysis of parameters such as rolling velocities and rolling path, are important advantages for assessing cell rolling properties in-vitro. Allowing rapid and accurate analysis of engineering approaches designed to impact cell rolling and homing, this platform may help advance exogenous cell-based therapy.
Bioengineering, Issue 80, Microfluidics, Endothelial Cells, Leukocyte Rolling, HL-60 cells, TNF-α, P-selectin, E-selectin
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Optimized Staining and Proliferation Modeling Methods for Cell Division Monitoring using Cell Tracking Dyes
Authors: Joseph D. Tario Jr., Kristen Humphrey, Andrew D. Bantly, Katharine A. Muirhead, Jonni S. Moore, Paul K. Wallace.
Institutions: Roswell Park Cancer Institute, University of Pennsylvania , SciGro, Inc., University of Pennsylvania .
Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of different cell types in vitro and in vivo.1-5 Although there are literally thousands of publications using such dyes, some of the most commonly encountered cell tracking applications include monitoring of: stem and progenitor cell quiescence, proliferation and/or differentiation6-8 antigen-driven membrane transfer9 and/or precursor cell proliferation3,4,10-18 and immune regulatory and effector cell function1,18-21. Commercially available cell tracking dyes vary widely in their chemistries and fluorescence properties but the great majority fall into one of two classes based on their mechanism of cell labeling. "Membrane dyes", typified by PKH26, are highly lipophilic dyes that partition stably but non-covalently into cell membranes1,2,11. "Protein dyes", typified by CFSE, are amino-reactive dyes that form stable covalent bonds with cell proteins4,16,18. Each class has its own advantages and limitations. The key to their successful use, particularly in multicolor studies where multiple dyes are used to track different cell types, is therefore to understand the critical issues enabling optimal use of each class2-4,16,18,24. The protocols included here highlight three common causes of poor or variable results when using cell-tracking dyes. These are: Failure to achieve bright, uniform, reproducible labeling. This is a necessary starting point for any cell tracking study but requires attention to different variables when using membrane dyes than when using protein dyes or equilibrium binding reagents such as antibodies. Suboptimal fluorochrome combinations and/or failure to include critical compensation controls. Tracking dye fluorescence is typically 102 - 103 times brighter than antibody fluorescence. It is therefore essential to verify that the presence of tracking dye does not compromise the ability to detect other probes being used. Failure to obtain a good fit with peak modeling software. Such software allows quantitative comparison of proliferative responses across different populations or stimuli based on precursor frequency or other metrics. Obtaining a good fit, however, requires exclusion of dead/dying cells that can distort dye dilution profiles and matching of the assumptions underlying the model with characteristics of the observed dye dilution profile. Examples given here illustrate how these variables can affect results when using membrane and/or protein dyes to monitor cell proliferation.
Cellular Biology, Issue 70, Molecular Biology, Cell tracking, PKH26, CFSE, membrane dyes, dye dilution, proliferation modeling, lymphocytes
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High Efficiency Differentiation of Human Pluripotent Stem Cells to Cardiomyocytes and Characterization by Flow Cytometry
Authors: Subarna Bhattacharya, Paul W. Burridge, Erin M. Kropp, Sandra L. Chuppa, Wai-Meng Kwok, Joseph C. Wu, Kenneth R. Boheler, Rebekah L. Gundry.
Institutions: Medical College of Wisconsin, Stanford University School of Medicine, Medical College of Wisconsin, Hong Kong University, Johns Hopkins University School of Medicine, Medical College of Wisconsin.
There is an urgent need to develop approaches for repairing the damaged heart, discovering new therapeutic drugs that do not have toxic effects on the heart, and improving strategies to accurately model heart disease. The potential of exploiting human induced pluripotent stem cell (hiPSC) technology to generate cardiac muscle “in a dish” for these applications continues to generate high enthusiasm. In recent years, the ability to efficiently generate cardiomyogenic cells from human pluripotent stem cells (hPSCs) has greatly improved, offering us new opportunities to model very early stages of human cardiac development not otherwise accessible. In contrast to many previous methods, the cardiomyocyte differentiation protocol described here does not require cell aggregation or the addition of Activin A or BMP4 and robustly generates cultures of cells that are highly positive for cardiac troponin I and T (TNNI3, TNNT2), iroquois-class homeodomain protein IRX-4 (IRX4), myosin regulatory light chain 2, ventricular/cardiac muscle isoform (MLC2v) and myosin regulatory light chain 2, atrial isoform (MLC2a) by day 10 across all human embryonic stem cell (hESC) and hiPSC lines tested to date. Cells can be passaged and maintained for more than 90 days in culture. The strategy is technically simple to implement and cost-effective. Characterization of cardiomyocytes derived from pluripotent cells often includes the analysis of reference markers, both at the mRNA and protein level. For protein analysis, flow cytometry is a powerful analytical tool for assessing quality of cells in culture and determining subpopulation homogeneity. However, technical variation in sample preparation can significantly affect quality of flow cytometry data. Thus, standardization of staining protocols should facilitate comparisons among various differentiation strategies. Accordingly, optimized staining protocols for the analysis of IRX4, MLC2v, MLC2a, TNNI3, and TNNT2 by flow cytometry are described.
Cellular Biology, Issue 91, human induced pluripotent stem cell, flow cytometry, directed differentiation, cardiomyocyte, IRX4, TNNI3, TNNT2, MCL2v, MLC2a
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Inhibitory Synapse Formation in a Co-culture Model Incorporating GABAergic Medium Spiny Neurons and HEK293 Cells Stably Expressing GABAA Receptors
Authors: Laura E. Brown, Celine Fuchs, Martin W. Nicholson, F. Anne Stephenson, Alex M. Thomson, Jasmina N. Jovanovic.
Institutions: University College London.
Inhibitory neurons act in the central nervous system to regulate the dynamics and spatio-temporal co-ordination of neuronal networks. GABA (γ-aminobutyric acid) is the predominant inhibitory neurotransmitter in the brain. It is released from the presynaptic terminals of inhibitory neurons within highly specialized intercellular junctions known as synapses, where it binds to GABAA receptors (GABAARs) present at the plasma membrane of the synapse-receiving, postsynaptic neurons. Activation of these GABA-gated ion channels leads to influx of chloride resulting in postsynaptic potential changes that decrease the probability that these neurons will generate action potentials. During development, diverse types of inhibitory neurons with distinct morphological, electrophysiological and neurochemical characteristics have the ability to recognize their target neurons and form synapses which incorporate specific GABAARs subtypes. This principle of selective innervation of neuronal targets raises the question as to how the appropriate synaptic partners identify each other. To elucidate the underlying molecular mechanisms, a novel in vitro co-culture model system was established, in which medium spiny GABAergic neurons, a highly homogenous population of neurons isolated from the embryonic striatum, were cultured with stably transfected HEK293 cell lines that express different GABAAR subtypes. Synapses form rapidly, efficiently and selectively in this system, and are easily accessible for quantification. Our results indicate that various GABAAR subtypes differ in their ability to promote synapse formation, suggesting that this reduced in vitro model system can be used to reproduce, at least in part, the in vivo conditions required for the recognition of the appropriate synaptic partners and formation of specific synapses. Here the protocols for culturing the medium spiny neurons and generating HEK293 cells lines expressing GABAARs are first described, followed by detailed instructions on how to combine these two cell types in co-culture and analyze the formation of synaptic contacts.
Neuroscience, Issue 93, Developmental neuroscience, synaptogenesis, synaptic inhibition, co-culture, stable cell lines, GABAergic, medium spiny neurons, HEK 293 cell line
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Passive Administration of Monoclonal Antibodies Against H. capsulatum and Others Fungal Pathogens
Authors: Allan J. Guimarães, Luis R. Martinez, Joshua D. Nosanchuk.
Institutions: Albert Einstein College of Medicine.
The purpose of the use of this methodology is 1) to advance our capacity to protect individuals with antibody or vaccine for preventing or treating histoplasmosis caused by the fungus Histoplasma capsulatum and 2) to examine the role of virulence factors as target for therapy. To generate mAbs, mice are immunized, the immune responses are assessed using a solid phase ELISA system developed in our laboratory, and the best responder mice are selected for isolation of splenocytes for fusion with hybridoma cells. C57BL/6 mice have been extensively used to study H. capsulatum pathogenesis and provide the best model for obtaining the data required. In order to assess the role of the mAbs in infection, mice are intraperitoneally administered with either mAb to H. capsulatum or isotype matched control mAb and then infected by either intravenous (i.v.), intraperitoneal (i.p.), or intranasal (i.n.) routes. In the scientific literature, efficacy of mAbs for fungal infections in mice relies on mortality as an end point, in conjunction with colony formin units (CFU) assessments at earlier time points. Survival (time to death) studies are necessary as they best represent human disease. Thus, efficacy of our intervention would not adequately be established without survival curves. This is also true for establishing efficacy of vaccine or testing of mutants for virulence. With histoplasmosis, the mice often go from being energetic to dead over several hours. The capacity of an intervention such as the administration of a mAb may initially protect an animal from disease, but the disease can relapse which would not be realized in short CFU experiments. In addition to survival and fungal burden assays, we examine the inflammatory responses to infection (histology, cellular recruitment, cytokine responses). For survival/time to death experiments, the mice are infected and monitored at least twice daily for signs of morbidity. To assess fungal burden, histopathology, and cytokine responses, the mice are euthanized at various times after infection. Animal experiments are performed according to the guidelines of the Institute for Animal Studies of the Albert Einstein College of Medicine.
Infection, Issue 48, Fungal pathogens, monoclonal antibodies, protection, passive administration
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Determining the Phagocytic Activity of Clinical Antibody Samples
Authors: Elizabeth G. McAndrew, Anne-Sophie Dugast, Anna F. Licht, Justin R. Eusebio, Galit Alter, Margaret E. Ackerman.
Institutions: Ragon Institute of MGH, MIT, and Harvard, Dartmouth College.
Antibody-driven phagocytosis is induced via the engagement of Fc receptors on professional phagocytes, and can contribute to both clearance as well as pathology of disease. While the properties of the variable domains of antibodies have long been considered critical to in vivo function, the ability of antibodies to recruit innate immune cells via their Fc domains has become increasingly appreciated as a major factor in their efficacy, both in the setting of recombinant monoclonal antibody therapy, as well as in the course of natural infection or vaccination1-3. Importantly, despite its nomenclature as a constant domain, the antibody Fc domain does not have constant function, and is strongly modulated by IgG subclass (IgG1-4) and glycosylation at Asparagine 2974-6. Thus, this method to study functional differences of antigen-specific antibodies in clinical samples will facilitate correlation of the phagocytic potential of antibodies to disease state, susceptibility to infection, progression, or clinical outcome. Furthermore, this effector function is particularly important in light of the documented ability of antibodies to enhance infection by providing pathogens access into host cells via Fc receptor-driven phagocytosis7. Additionally, there is some evidence that phagocytic uptake of immune complexes can impact the Th1/Th2 polarization of the immune response8. Here, we describe an assay designed to detect differences in antibody-induced phagocytosis, which may be caused by differential IgG subclass, glycan structure at Asn297, as well as the ability to form immune complexes of antigen-specific antibodies in a high-throughput fashion. To this end, 1 μm fluorescent beads are coated with antigen, then incubated with clinical antibody samples, generating fluorescent antigen specific immune complexes. These antibody-opsonized beads are then incubated with a monocytic cell line expressing multiple FcγRs, including both inhibitory and activating. Assay output can include phagocytic activity, cytokine secretion, and patterns of FcγRs usage, and are determined in a standardized manner, making this a highly useful system for parsing differences in this antibody-dependent effector function in both infection and vaccine-mediated protection9.
Immunology, Issue 57, Phagocytosis, Antibody, ADCC, Effector Function, Fc receptor, antibody-dependent phagocytosis, monocytes
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Chemically-blocked Antibody Microarray for Multiplexed High-throughput Profiling of Specific Protein Glycosylation in Complex Samples
Authors: Chen Lu, Joshua L. Wonsidler, Jianwei Li, Yanming Du, Timothy Block, Brian Haab, Songming Chen.
Institutions: Institute for Hepatitis and Virus Research, Thomas Jefferson University , Drexel University College of Medicine, Van Andel Research Institute, Serome Biosciences Inc..
In this study, we describe an effective protocol for use in a multiplexed high-throughput antibody microarray with glycan binding protein detection that allows for the glycosylation profiling of specific proteins. Glycosylation of proteins is the most prevalent post-translational modification found on proteins, and leads diversified modifications of the physical, chemical, and biological properties of proteins. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases. However, current methods to study protein glycosylation typically are too complicated or expensive for use in most normal laboratory or clinical settings and a more practical method to study protein glycosylation is needed. The new protocol described in this study makes use of a chemically blocked antibody microarray with glycan-binding protein (GBP) detection and significantly reduces the time, cost, and lab equipment requirements needed to study protein glycosylation. In this method, multiple immobilized glycoprotein-specific antibodies are printed directly onto the microarray slides and the N-glycans on the antibodies are blocked. The blocked, immobilized glycoprotein-specific antibodies are able to capture and isolate glycoproteins from a complex sample that is applied directly onto the microarray slides. Glycan detection then can be performed by the application of biotinylated lectins and other GBPs to the microarray slide, while binding levels can be determined using Dylight 549-Streptavidin. Through the use of an antibody panel and probing with multiple biotinylated lectins, this method allows for an effective glycosylation profile of the different proteins found in a given human or animal sample to be developed. Introduction Glycosylation of protein, which is the most ubiquitous post-translational modification on proteins, modifies the physical, chemical, and biological properties of a protein, and plays a fundamental role in various biological processes1-6. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases 7-12. In fact, most current cancer biomarkers, such as the L3 fraction of α-1 fetoprotein (AFP) for hepatocellular carcinoma 13-15, and CA199 for pancreatic cancer 16, 17 are all aberrant glycan moieties on glycoproteins. However, methods to study protein glycosylation have been complicated, and not suitable for routine laboratory and clinical settings. Chen et al. has recently invented a chemically blocked antibody microarray with a glycan-binding protein (GBP) detection method for high-throughput and multiplexed profile glycosylation of native glycoproteins in a complex sample 18. In this affinity based microarray method, multiple immobilized glycoprotein-specific antibodies capture and isolate glycoproteins from the complex mixture directly on the microarray slide, and the glycans on each individual captured protein are measured by GBPs. Because all normal antibodies contain N-glycans which could be recognized by most GBPs, the critical step of this method is to chemically block the glycans on the antibodies from binding to GBP. In the procedure, the cis-diol groups of the glycans on the antibodies were first oxidized to aldehyde groups by using NaIO4 in sodium acetate buffer avoiding light. The aldehyde groups were then conjugated to the hydrazide group of a cross-linker, 4-(4-N-MaleimidoPhenyl)butyric acid Hydrazide HCl (MPBH), followed by the conjugation of a dipeptide, Cys-Gly, to the maleimide group of the MPBH. Thus, the cis-diol groups on glycans of antibodies were converted into bulky none hydroxyl groups, which hindered the lectins and other GBPs bindings to the capture antibodies. This blocking procedure makes the GBPs and lectins bind only to the glycans of captured proteins. After this chemically blocking, serum samples were incubated with the antibody microarray, followed by the glycans detection by using different biotinylated lectins and GBPs, and visualized with Cy3-streptavidin. The parallel use of an antibody panel and multiple lectin probing provides discrete glycosylation profiles of multiple proteins in a given sample 18-20. This method has been used successfully in multiple different labs 1, 7, 13, 19-31. However, stability of MPBH and Cys-Gly, complicated and extended procedure in this method affect the reproducibility, effectiveness and efficiency of the method. In this new protocol, we replaced both MPBH and Cys-Gly with one much more stable reagent glutamic acid hydrazide (Glu-hydrazide), which significantly improved the reproducibility of the method, simplified and shorten the whole procedure so that the it can be completed within one working day. In this new protocol, we describe the detailed procedure of the protocol which can be readily adopted by normal labs for routine protein glycosylation study and techniques which are necessary to obtain reproducible and repeatable results.
Molecular Biology, Issue 63, Glycoproteins, glycan-binding protein, specific protein glycosylation, multiplexed high-throughput glycan blocked antibody microarray
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CD4+ T-Lymphocyte Capture Using a Disposable Microfluidic Chip for HIV
Authors: Sang Jun Moon, Richard Lin, Utkan Demirci.
Institutions: Brigham and Women's Hospital, Massachusetts Institute of Technology.
Cellular Biology, Issue 8, microfluidic, blood, diagnostics, bioengineering, HIV, Translational Research
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Plastic Embedding and Sectioning of Xenopus laevis Embryos
Authors: Souichi Ogata, Shimako Kawauchi, Anne Calof, Ken W.Y. Cho.
Institutions: University of California, Irvine (UCI), University of California, Irvine (UCI).
Developmental Biology, Issue 3, embryo, Xenopus, dissection
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Depletion of Specific Cell Populations by Complement Depletion
Authors: Bonnie N. Dittel.
Institutions: Blood Research Institute.
The purification of immune cell populations is often required in order to study their unique functions. In particular, molecular approaches such as real-time PCR and microarray analysis require the isolation of cell populations with high purity. Commonly used purification strategies include fluorescent activated cell sorting (FACS), magnetic bead separation and complement depletion. Of the three strategies, complement depletion offers the advantages of being fast, inexpensive, gentle on the cells and a high cell yield. The complement system is composed of a large number of plasma proteins that when activated initiate a proteolytic cascade culminating in the formation of a membrane-attack complex that forms a pore on a cell surface resulting in cell death1. The classical pathway is activated by IgM and IgG antibodies and was first described as a mechanism for killing bacteria. With the generation of monoclonal antibodies (mAb), the complement cascade can be used to lyse any cell population in an antigen-specific manner. Depletion of cells by the complement cascade is achieved by the addition of complement fixing antigen-specific antibodies and rabbit complement to the starting cell population. The cells are incubated for one hour at 37°C and the lysed cells are subsequently removed by two rounds of washing. MAb with a high efficiency for complement fixation typically deplete 95-100% of the targeted cell population. Depending on the purification strategy for the targeted cell population, complement depletion can be used for cell purification or for the enrichment of cell populations that then can be further purified by a subsequent method.
JoVE Immunology, Issue 36, rabbit, complement, cell isolation, cell depletion
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