Show Advanced Search


Containing Text
- - -
Filter by author or institution
Filter by publication date
October, 2006
Filter by journal section

Filter by science education

Molecular Weight: The sum of the weight of all the atoms in a molecule.

Molecular Cloning

JoVE 5074

Molecular cloning is a set of methods, which are used to insert recombinant DNA into a vector - a carrier of DNA molecules that will replicate recombinant DNA fragments in host organisms. The DNA fragment, which may be a gene, can be isolated from a prokaryotic or eukaryotic specimen. Following isolation of the fragment of interest, or insert, both the vector and insert must be cut with…

 Basic Methods in Cellular and Molecular Biology

Kinetics of Addition Polymerization to Polydimethylsiloxane

JoVE 10369

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

Polymers are molecules consisting of many repeating monomer units that are chemically bonded into long chains. They exhibit a broad range of physical properties, which are affected by their chemical structure,…

 Chemical Engineering

Dialysis: Diffusion Based Separation

JoVE 5684

Dialysis is a common technique used in biochemistry for separating molecules based on diffusion. In this procedure, a semipermeable membrane allows the movement of certain molecules based on size. This method can be applied to the removal of buffer, known as desalting, or exchanging buffer molecules or ions from a protein solution.

This video covers the principles of dialysis…


Freezing-Point Depression to Determine an Unknown Compound

JoVE 10137

Source: Laboratory of Lynne O' Connell — Boston College

When a solid compound is dissolved in a solvent, the freezing point of the resulting solution is lower than that of the pure solvent. This phenomenon is known as freezing-point depression, and the change in temperature is directly related to the molecular weight of the…

 General Chemistry

Chromatography-based Biomolecule Purification Methods

JoVE 5683

In biochemistry, chromatography-based purification methods are employed to isolate compounds from a complex mixture. Two such methods used commonly by biochemists are size-exclusion chromatography and affinity chromatography. In size-exclusion chromatography, a column packed with porous beads separates components of a mixture based on size. On the other hand, affinity chromatography allows for …


Two-Dimensional Gel Electrophoresis

JoVE 5686

Two-dimensional gel electrophoresis (2DGE) is a technique that can resolve thousands of biomolecules from a mixture. This technique involves two distinct separation methods that have been coupled together: isoelectric focusing (IEF) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). This physically separates compounds across two axes of a gel by their isoelectric points…


Gas Chromatography (GC) with Flame-Ionization Detection

JoVE 10187

Source: Laboratory of Dr. B. Jill Venton - University of Virginia

Gas chromatography (GC) is used to separate and detect small molecular weight compounds in the gas phase. The sample is either a gas or a liquid that is vaporized in the injection port. Typically, the compounds analyzed are less than 1,000 Da, because it is difficult to…

 Analytical Chemistry

Preparing Anhydrous Reagents and Equipment

JoVE 10227

Source: Laboratory of Dr. Dana Lashley - College of William and Mary
Demonstrated by: Timothy Beck and Lucas Arney

Many reactions in organic chemistry are moisture-sensitive and must be carried out under careful exclusion of water. In these cases the reagents have a high affinity to react with water from the atmosphere and if left…

 Organic Chemistry

Understanding Concentration and Measuring Volumes

JoVE 5026

Solutions are utilized to some degree in almost all biological research applications. Therefore understanding how to measure and manipulate them is imperative to any experiment. In this video, concepts in preparing solutions are introduced.

Solutions consist of a solute dissolved in solvent to yield a homogeneous mixture of molecular substances. …

 General Laboratory Techniques

What is Glycolysis?

JoVE 10737

Cells make energy by breaking down macromolecules. Cellular respiration is the biochemical process that converts “food energy” (from the chemical bonds of macromolecules) into chemical energy in the form of adenosine triphosphate (ATP). The first step of this tightly regulated and intricate process is glycolysis. The word glycolysis originates from Latin glyco (sugar) and lysis (breakdown). Glycolysis serves two main intracellular functions: generate ATP and intermediate metabolites to feed into other pathways. The glycolytic pathway converts one hexose (six-carbon carbohydrate such as glucose), into two triose molecules (three-carbon carbohydrate) such as pyruvate, and a net of two molecules of ATP (four produced, two consumed) and two molecules of nicotinamide adenine dinucleotide (NADH). Did you know that glycolysis was the first biochemical pathway discovered? In the mid-1800s, Louis Pasteur determined that microorganisms cause the breakdown of glucose in the absence of oxygen (fermentation). In 1897, Eduard Buchner found that fermentation reactions can still be carried out in cell-free yeast extracts, achieved by breaking open the cell and collecting the cytoplasm which contains the soluble molecules and organelles. Shortly thereafter in 1905, Arthur Harden and William Young discovered that the rate of fermentation decreases wit

 Core: Biology

Yeast Signaling

JoVE 10714

Yeasts are single-celled organisms, but unlike bacteria, they are eukaryotes—cells that have a nucleus. Cell signaling in yeast is similar to signaling in other eukaryotic cells. A ligand, such as a protein or a small molecule outside the yeast cell, attaches to a receptor on the cell surface. The binding stimulates second-messenger kinases (enzymes that phosphorylate specific substrates) to activate or inactivate transcription factors that regulate gene expression. Many of the yeast intracellular signaling cascades have similar counterparts in Homo sapiens, making yeast a convenient model for studying intracellular signaling in humans. Yeasts are members of the fungus kingdom. They use signaling for various functions, especially for reproduction. Yeasts can undergo “sexual” reproduction using mating pheromones, which are peptides—short chains of amino acids. Yeast colonies consist of both diploid and haploid cells. Both types of cells can undergo mitosis, but only diploid cells can undergo meiosis. When diploid cells undergo meiosis, the four resulting haploid cells, called spores, are not identical. In fact, the division of one diploid cell into four spores creates two “sexes” of yeast cells, each two cells of the type MAT-a and MAT-alpha. MAT-a cells secrete mating

 Core: Biology

Metabolic Labeling

JoVE 5687

Metabolic labeling is used to probe the biochemical transformations and modifications that occur in a cell. This is accomplished by using chemical analogs that mimic the structure of natural biomolecules. Cells utilize analogs in their endogenous biochemical processes, producing compounds that are labeled. The label allows for the incorporation of detection and affinity tags, which can then be …


Ideal Gas Law

JoVE 5537

Source: Laboratory of Dr. Andreas Züttel - Swiss Federal Laboratories for Materials Science and Technology

The ideal gas law describes the behavior of most common gases at near-ambient conditions and the tendency of all chemical matter in the dilute limit. It is a fundamental relationship between three measurable macroscopic system…

 General Chemistry

Transformation of E. coli Cells Using an Adapted Calcium Chloride Procedure

JoVE 10515

Source: Natalia Martin1, Andrew J. Van Alst1, Rhiannon M. LeVeque1, and Victor J. DiRita1
1 Department of Microbiology and Molecular Genetics, Michigan State University

Bacteria have the ability to exchange genetic material (DeoxyriboNucleic Acid, DNA) in a process known as horizontal gene transfer. Incorporating exogenous DNA…


DNA Ligation Reactions

JoVE 5069

In molecular biology, ligation refers to the joining of two DNA fragments through the formation of a phosphodiester bond. An enzyme known as a ligase catalyzes the ligation reaction. In the cell, ligases repair single and double strand breaks that occur during DNA replication. In the laboratory, DNA ligase is used during molecular cloning to join DNA fragments of inserts with vectors…

 Basic Methods in Cellular and Molecular Biology

Tension Tests of Polymers

JoVE 10418

Source: Roberto Leon, Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA

Polymeric materials are widely used in civil structures, with uses ranging from very soft sealants to more rigid pipes in water and wastewater systems. The most basic definition of a polymer is a molecular structure with repeating…

 Structural Engineering

Testing For Genetically Modified Foods

JoVE 10044

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

Genetic modification of foods has been a controversial issue due to debated concerns over health and environmental safety. This experiment demonstrates technical understanding of how food DNA is genetically identified, allowing for educated decision making about …

 Environmental Science

Introduction to Mass Spectrometry

JoVE 5634

Source: Laboratory of Dr. Khuloud Al-Jamal - King's College London

Mass spectrometry is an analytical chemistry technique that enables the identification of unknown compounds within a sample, the quantification of known materials, the determination of the structure, and chemical properties of different molecules.

 Analytical Chemistry

Electric Potential

JoVE 10329

Source: Yong P. Chen, PhD, Department of Physics & Astronomy, College of Science, Purdue University, West Lafayette, IN

Electric potential, also known as "voltage", measures the electric potential energy per unit charge. Electric field is a scalar quantity and is fundamental to many electrical effects. Like potential energy,…

 Physics II


JoVE 10357

Source: Vy M. Dong and Jan Riedel, Department of Chemistry, University of California, Irvine, CA

Polymers are made from macromolecules, which are composed of repeating units (the so called monomeric units). In our modern world, polymers play an important role. One of the first important polymers was nylon, which is a polyamide. It found…

 Organic Chemistry II

Sample Preparation for Analytical Characterization

JoVE 10205

Source: Laboratory of Dr. B. Jill Venton - University of Virginia

Sample preparation is the way in which a sample is treated to prepare for analysis. Careful sample preparation is critical in analytical chemistry to accurately generate either a standard or unknown sample for a chemical measurement. Errors in analytical chemistry…

 Analytical Chemistry

Nutrients in Aquatic Ecosystems

JoVE 10023

Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University

Nitrogen and phosphorus are essential plant nutrients found in aquatic ecosystems and both are monitored as a part of water quality testing because in excess amounts they can cause significant water quality problems. 

 Environmental Science

Plasmid Purification

JoVE 5062

Plasmid purification is a technique used to isolate and purify plasmid DNA from genomic DNA, proteins, ribosomes, and the bacterial cell wall. A plasmid is a small, circular, double-stranded DNA that is used as a carrier of specific DNA molecules. When introduced into a host organism via transformation, a plasmid will be replicated, creating numerous copies of the DNA fragment under…

 Basic Methods in Cellular and Molecular Biology

Internal Standards

JoVE 10225

Source: Laboratory of Dr. B. Jill Venton - University of Virginia

The goal of many chemical analyses is a quantitative analysis, where the amount of a substance in a sample is determined. In order to accurately calculate the concentration of an unknown from a sample, careful sample preparation is key. Every time a sample is…

 Analytical Chemistry

Gel Purification

JoVE 5063

Gel purification is used to recover DNA fragments after electrophoretic separation. DNA recovery from an agarose gel includes three basic steps: binding, washing and eluting from a silica column. DNA is believed to bind to silica in the presence of high salt via a salt bridge. Following binding, DNA is washed of impurities and eluted under low salt conditions disrupting this…

 Basic Methods in Cellular and Molecular Biology

DNA Gel Electrophoresis

JoVE 5057

DNA gel electrophoresis is a technique used for the detection and separation of DNA molecules. An electric field is applied to a gel matrix comprised of agarose, and within the gel, charge particles will migrate and separate based on size. The negatively charged phosphates of the DNA backbone cause DNA fragments to move toward the anode - a positively charged electrode.

The video…

 Basic Methods in Cellular and Molecular Biology

Introduction to Titration

JoVE 5699

Source: Laboratory of Dr. Yee Nee Tan — Agency for Science, Technology, and Research

Titration is a common technique used to quantitatively determine the unknown concentration of an identified analyte.1-4 It is also called volumetric analysis, as the measurement of volumes is critical in titration. There are many types of titrations…

 General Chemistry

Separating Protein with SDS-PAGE

JoVE 5058

Sodium Dodecyl Sulfate Poly-Acrylamide Gel Electrophoresis, or SDS-PAGE, is a widely-used technique for separating mixtures of proteins based on their size and nothing else. SDS, an anionic detergent, is used to produce an even charge across the length of proteins that have been linearized. By first loading them into a gel made of polyacrylamide and then applying an electric field to the gel,…

 Basic Methods in Cellular and Molecular Biology

Making Solutions in the Laboratory

JoVE 5030

The ability to successfully make solutions is a basic laboratory skill performed in virtually all biological and chemical experiments. A solution is a homogenous mixture of solute dissolved in bulk liquid known as the solvent. Solutions can be described by their solute concentration, a measure of how much solute is present per unit of solution.

In this…

 General Laboratory Techniques

Tissue Collection of Bats for -Omics Analyses and Primary Cell Culture

1Department of Geology & Geophysics, Yale University, 2Department of Ecology & Evolution, Stony Brook University, 3Neurogenetics of Vocal Communication, Max Planck Institute for Psycholinguistics, 4School of Biological and Chemical Sciences, Queen Mary University of London, 5School of Biology & Environmental Science, University College Dublin, 6Donders Institute for Brain, Cognition and Behavior, 7Consortium for Inter-Disciplinary Environmental Research, Stony Brook University

JoVE 59505


Purification and Analytics of a Monoclonal Antibody from Chinese Hamster Ovary Cells Using an Automated Microbioreactor System

1Center for Drug Evaluation and Research, Office of Product Quality, Office of Biotechnology Products, Division of Biotechnology Review and Research II, U.S. Food and Drug Administration

JoVE 58947

More Results...