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Amino Acids, Basic: Amino acids with side chains that are positively charged at physiological pH.

Photometric Protein Determination

JoVE 5688

Measuring the concentration is a fundamental step of many biochemical assays. Photometric protein determination takes advantage of the fact that the more a sample contains light-absorbing substances, the less the light will transmit through it. Since the relationship between concentration and absorption is linear, this phenomenon can be used to measure the concentration in samples where it is unknown. This video describes the basics of photometric protein determination and introduces the Bradford Assay and the Lowry Method. The procedure in the video will cover a typical Bradford assay. Applications covered include direct measurement of very small volumes of nucleic acids to characterize concentration and purity, determination of coupling efficiency of a biomimetic material, and another variation of photometric protein determination using Remazol dye. Determining the concentration of a protein in samples is a fundamental step in many biochemical assays. Photometric determination can be done with small sample sizes. The more a sample contains light-absorbing substances, the less the light will transmit through it. This provides a quantitative measurement of the absorbing substances. These concepts are so fundamental to science that the articles that introduced two of the techniques are in the three most cited papers of


Introduction to the Spectrophotometer

JoVE 5038

The spectrophotometer is a routinely used instrument in scientific research. Spectrophotometry is the quantitative measurement of how much a chemical substance absorbs light by passing a beam of light through the sample using a spectrophotometer. In this video, basic concepts in spectrophotometry, including transmittance, absorbance and the Beer-Lambert Law are reviewed in addition to the components of the spectrophotometer. These concepts provide a foundation for how to determine the concentration of a solute in solution that is capable of absorbing light in the ultraviolet and visible range. Furthermore, a procedure for how to operate the spectrophotometer is demonstrated, including instructions on how to blank and measure the absorbance of a sample at the desired wavelength. The video also covers how to make a standard curve for determination of analyte concentration. Several applications of the spectrophotometer in biological research are discussed, such as measurement of cell density and determination of chemical reaction rates. Finally, the microvolume spectrophotometer is introduced, as well as its advantage in measuring the quality and quantity of protein and nucleic acids.

 General Laboratory Techniques

Yeast Maintenance

JoVE 5095

Research performed in the yeast Saccharomyces cerevisiae has significantly improved our understanding of important cellular phenomona such as regulation of the cell cycle, aging, and cell death. The many benefits of working with S. cerevisiae include the facts that they are inexpensive to grow in the lab and that many ready-to-use strains are now commercially available. Nevertheless, proper maintenance of this organism is critical for successful experiments. This video will provide an overview of how to grow and maintain S. cerevisiae in the lab. Basic concepts required for monitoring the proliferation of a yeast population, such as how to generate a growth curve using a spectrophotometer, are explained. This video also demonstrates the hands-on techniques required to maintain S. cerevisiae in the lab, including preparation of media, how to start a new culture of yeast cells, and how to store those cultures. Finally, the video shows off some of the ways these handling and maintenance techniques are applied in scientific research.

 Biology I

An Introduction to Cell Metabolism

JoVE 5652

In cells, critical molecules are either built by joining together individual units like amino acids or nucleotides, or broken down into smaller components. Respectively, the reactions responsible for this are referred to as anabolic and catabolic. These reactions require or produce energy typically in the form of a “high-energy” molecule called ATP. Together, these processes make up “Cell Metabolism,” and are hallmarks of healthy, living cells.JoVE’s introduction to cell metabolism briefly reviews the rich history of this field, ranging from early studies on photosynthesis to more recent discoveries pertaining to energy production in all cells. This is followed by a discussion of some key questions asked by scientists studying metabolism, and common methods that they apply to answer these questions. Finally, we’ll explore how current researchers are studying alterations in metabolism that accompany metabolic disorders, or that occur following exposure to environmental stressors.

 Cell Biology

Yeast Transformation and Cloning

JoVE 5083

S. cerevisiae are unicellular eukaryotes that are a commonly-used model organism in biological research. In the course of their work, yeast researchers rely upon the fundamental technique of transformation (the uptake of foreign DNA by the cell) to control gene expression, induce genetic deletions, express recombinant proteins, and label subcellular structures.

This video provides an overview of how and why yeast transformation is carried out in the lab. The important features of yeast plasmids will be presented, along with the procedure required to prepare yeast cells to incorporate new plasmids. The presentation also includes a step-by-step protocol for the lithium acetate method of yeast transformation. Finally, examples of the many applications of this essential technique will be provided.

 Biology I

Use of Interferon-γ Enzyme-linked Immunospot Assay to Characterize Novel T-cell Epitopes of Human Papillomavirus

1Department of Microbiology and Parasitology, College of Basic Medical Sciences, China Medical University, 2Department of Obstetrics and Gynecology, College of Medicine, University of Arkansas for Medical Sciences, 3Department of Pathology, College of Medicine, University of Arkansas for Medical Sciences

JoVE 3657

 Immunology and Infection

Engineering 'Golden' Fluorescence by Selective Pressure Incorporation of Non-canonical Amino Acids and Protein Analysis by Mass Spectrometry and Fluorescence

1Institute of Chemistry L 1, Department of Biocatalysis, Technical University of Berlin, 2Institute of Chemistry PC 14, Department of Bioenergetics, Technical University of Berlin, 3Institute of Chemistry TC 7, Department of Physical Chemistry/Molecular Material Sciences, Technical University of Berlin

JoVE 57017


Antimicrobial Peptides Produced by Selective Pressure Incorporation of Non-canonical Amino Acids

1Department of Biocatalysis, Institute of Chemistry, Technische Universität Berlin, 2Department of Bioenergetics, Institute of Chemistry, Technische Universität Berlin, 3Molecular Genetics Group, Groningen Biomolecular Sciences and Biotechnology Institute, Department of Molecular Genetics, University of Groningen

JoVE 57551


Quantitative Analyses of all Influenza Type A Viral Hemagglutinins and Neuraminidases using Universal Antibodies in Simple Slot Blot Assays

1Centre for Vaccine Evaluation, Biologics and Genetic Therapies Directorate, HPFB, Health canada, 2National Institute for the Control of Pharmaceutical and Biological Products, The State Food and Drug Administration, Beijing, 3Department of Biochemistry, Microbiology and Immunology, University of Ottawa, 4Microbiology Department, Faculty of Medicine, King Abdulaziz University, 5National Microbiology Laboratory, Public Health Agency of Canada

JoVE 2784

 Immunology and Infection

Protocols for Implementing an Escherichia coli Based TX-TL Cell-Free Expression System for Synthetic Biology

1Department of Biology, California Institute of Technology, 2Department of Bioengineering, California Institute of Technology, 3Synthetic Biology Center, Department of Bioengineering, Massachusetts Institute of Technology, 4School of Physics and Astronomy, University of Minnesota

JoVE 50762


Crystallization of Salicylic Acid via Chemical Modification

JoVE 10407

Source: Kerry M. Dooley and Michael G. Benton, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA

Processing of biochemicals involves unit operations such as crystallization, ultracentrifugation, membrane filtration, and preparative chromatography, all of which have in common the need to separate large from small molecules, or solid from liquid. Of these, crystallization is the most important from a tonnage standpoint. For that reason, it is commonly employed in the pharmaceutical, chemical and food processing industries. Important biochemical examples include chiral separations,1 purification of antibiotics,2 separation of amino acids from precursors,3 and many other pharmaceutical,4-5 food additive,6-7 and agrochemical purifications.8 The control of crystal morphology and size distribution is critical to process economics, as these factors affect the costs of downstream processing operations such as drying, filtration, and solids conveying. For more information about crystallization, consult a specialized textbook or a Unit Operations textbook.9 The crystallizer unit (Figure 1) enables study of: (a)

 Chemical Engineering

A Fast and Quantitative Method for Post-translational Modification and Variant Enabled Mapping of Peptides to Genomes

1Department of Neurobiology, F. M. Kirby Neurobiology Center, Boston Children's Hospital, Harvard Medical School, 2Proteomic Mass Spectrometry, Wellcome Trust Sanger Institute, Wellcome Genome Campus, 3Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, 4Functional Proteomics Group, Chester Beatty Laboratories, Institute of Cancer Research

JoVE 57633


High-Performance Liquid Chromatography (HPLC)

JoVE 10156

Source: Dr. Paul Bower - Purdue University

High-performance liquid chromatography (HPLC) is an important analytical method commonly used to separate and quantify components of liquid samples. In this technique, a solution (first phase) is pumped through a column that contains a packing of small porous particles with a second phase bound to the surface. The different solubilities of the sample components in the two phases cause the components to move through the column with different average velocities, thus creating a separation of these components. The pumped solution is called the mobile phase, while the phase in the column is called the stationary phase. There are several modes of liquid chromatography, depending upon the type of stationary and/or mobile phase employed. This experiment uses reversed-phase chromatography, where the stationary phase is non-polar, and the mobile phase is polar. The stationary phase to be employed is C18 hydrocarbon groups bonded to 3-µm silica particles, while the mobile phase is an aqueous buffer with a polar organic modifier (acetonitrile) added to vary its eluting strength. In this form, the silica can be used for samples that are water-soluble, providing a broad range of applications. In this experiment, the mixtures of three components frequently found

 Analytical Chemistry

Gram Staining of Bacteria from Environmental Sources

JoVE 10092

Source: Laboratories of Dr. Ian Pepper and Dr. Charles Gerba - Arizona University
Demonstrating Author: Luisa Ikner

The spectrum of research in environmental microbiology is broad in scope and application potential. Whether the work is bench-scale with known bacterial isolates, or in the field collecting soil or water samples containing unknown bacterial isolates, the ability to quickly and visually discern culturable populations of interest remains of great import to environmental microbiologists even today with the abundance of molecular techniques available for use. This video will demonstrate one such technique, known as Gram staining.

 Environmental Microbiology

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