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 Science Education: Basic Methods in Cellular and Molecular Biology

Separating Protein with SDS-PAGE

JoVE Science Education

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., SDS-coated proteins are then separated. The electric field acts as the driving force, drawing the SDS coated proteins towards the anode with larger proteins moving more slowly than small proteins. In order to identify proteins by size, protein standards of a known size are loaded along with samples and run under the same conditions. This video presents an introduction to SDS-PAGE by first explaining the theory behind it and later demonstrating its step-by-step procedure. Various experimental parameters, such as the polyacrylamide concentration and voltage applied to the gel are discussed. Downstream staining methods like Coomassie and silver stains are introduced, and variations of the method, like 2D gel electrophoresis are presented.

 JoVE Immunology and Infection

A Semi-automated Approach to Preparing Antibody Cocktails for Immunophenotypic Analysis of Human Peripheral Blood

1Human Immune Monitoring Laboratory, Earle A. Chiles Research Institute, Providence Cancer Center, Providence Portland Medical Center, 2Sony Biotechnology, 3Beckman Coulter, Inc. Life Sciences, 4Bristol-Myers Squibb


JoVE 53485

 Science Education: Essentials of Cognitive Psychology

Mental Rotation

JoVE Science Education

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

Visual mental imagery refers to the ability to conjure images in one’s mind’s eye. This allows people to process visual material above and beyond the constraints of a current point-of-view; for example, a person could imagine, using their mind’s eye, how something might look in a different color, or what it would look like if it were made from a different material or rotated and seen from a different perspective. Mental imagery seems to support important human behaviors in many contexts. For example, people report visualizing routes and maps when planning a route or giving directions. They report visualizing movements, such as swinging a bat, to prepare for an actual action. They also report the mental rotation of objects in order to consider how an object might fit into a receptacle or clear a barrier. This video demonstrates how to use the mental rotation procedure in order to investigate visual mental imagery.

 Science Education: Essentials of General Chemistry

Spectrophotometric Determination of an Equilibrium Constant

JoVE Science Education

Source: Laboratory of Dr. Michael Evans — Georgia Institute of Technology

The equilibrium constant, K, for a chemical system is the ratio of product concentrations to reactant concentrations at equilibrium, each raised to the power of their respective stoichiometric coefficients. Measurement of K involves determination of these concentrations for systems in chemical equilibrium. Reaction systems containing a single colored component can be studied spectrophotometrically. The relation between absorbance and concentration for the colored component is measured and used to determine its concentration in the reaction system of interest. Concentrations of the colorless components can be calculated indirectly using the balanced chemical equation and the measured concentration of the colored component. In this video, the Beer's law curve for Fe(SCN)2+ is determined empirically and applied to the measurement of K for the following reaction: Four reaction systems with different initial concentrations of reactants are investigated to illustrate that K remains constant irrespective of initial concentration

 JoVE Chemistry

CN-GELFrEE - Clear Native Gel-eluted Liquid Fraction Entrapment Electrophoresis

1Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, Proteomics Center of Excellence, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, 2Institute of Chemistry, Proteomics Unit, Federal University of Rio de Janeiro, 3Department of Cell Biology, Brazilian Center for Protein Research, Laboratory of Biochemistry and Protein Chemistry, University of Brasilia


JoVE 53597

 Science Education: Essentials of Environmental Science

Tree Identification: How To Use a Dichotomous Key

JoVE Science Education

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

A dichotomous key is a tool that identifies items in nature, such as leaves. This method is based on the idea of choosing between two characteristics. The word dichotomous comes from two Greek words that mean “to divide into two parts.” In a dichotomous key for leaf identification, each pair of phrases describes different features of the leaf. Only one of the phrases correctly applies to the leaf being keyed out. The correct phrase leads to the next pair of phrases, or states the name of the tree from which the leaf came. Using a field guide to trees and the iTree National Tree Benefits Calculator helps to identify trees in a field investigation, which shows the significance of trees in terms of their environmental benefits, such as storm water management, increasing property value, energy efficiency, air quality, and carbon sequestration.

 JoVE Medicine

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS

1iC42 Clinical Research and Development, University of Colorado, Anschutz Medical Campus, 2Division of Clinical Pharmacology, Cincinnati Children's Hospital Medical Center, 3Food and Drug Administration (FDA), Center of Drug Evaluation Research - Office of Generic Drugs, 4Transplant Clinical Research, University of Cincinnati


JoVE 52424

 Science Education: Essentials of General Chemistry

Le Châtelier's Principle

JoVE Science Education

Source: Laboratory of Dr. Lynne O'Connell — Boston College

When the conditions of a system at equilibrium are altered, the system responds in such a way as to maintain the equilibrium. In 1888, Henri-Lewis Le Châtelier described this phenomenon in a principle that states, "When a change in temperature, pressure, or concentration disturbs a system in chemical equilibrium, the change will be counteracted by an alteration in the equilibrium composition." This experiment demonstrates Le Châtelier's principle at work in a reversible reaction between iron(III) ion and thiocyanate ion, which produces iron(III) thiocyante ion: Fe3+(aq) + SCN- (aq) FeSCN2+ (aq) The concentration of one of the ions is altered either by directly adding a quantity of one ion to the solution or by selectively removing an ion from the solution through formation of an insoluble salt. Observations of color changes indicate whether the equilibrium has shifted to favor formation of the products or the reactants. In addition, the effect of a temperature change on the solution at equilibrium can be obs

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