Undergraduate Biochemistry Laboratory Experiment Research Articles

Analyzing Exonuclease-Induced Hyperchromicity by UV Spectroscopy: An Undergraduate Biochemistry Laboratory Experiment

An undergraduate biochemistry laboratory experiment is described that utilizes free online bioinformatics tools along with readily available exonucleases to study the effects of base stacking and hydrogen bonding on the UV absorbance of DNA samples. UV absorbance of double-stranded DNA at the λmax is decreased when the DNA bases are involved in hydrogen bonding and formation of secondary structure. When an exonuclease is added to the solution containing the DNA, the strand is digested and the interactions disappear, leading to an increase in the absorbance called hyperchromicity. This experiment utilizes exonuclease digestion of DNA to show students how base interactions and secondary structure can alter the spectroscopic properties of a sample and, by extension, how apparent concentration as calculated with Beer–Lambert’s law is not necessarily representative of the true concentration of DNA in solution. Teaching applications of this laboratory experiment include enzyme kinetics and activity, secondary s...

Purification and Characterisation of Lactate Dehydrogenase: An Undergraduate Biochemistry Laboratory Experiment

The practical work described here was designed in the aim of combining several periods that were previously carried-out independently during the academic year and to more appropriately mimic a "research" environment. It illustrates several fundamental biochemical principles as well as experimental aspects and important techniques including spectrophotometry, chromatography, centrifugation, and electrophoresis. Lactate dehydrogenase (LDH) is an enzyme of choice for a student laboratory experiment. This enzyme has many advantages, namely its relative high abundance, high specific activity and high stability. In the first part, the purification scheme starting from pig heart includes ammonium sulphate fractionation, desalting by size exclusion chromatography, anion exchange chromatography and pseudo-affinity chromatography. In the second part of the work the obtained fractions are accessed for protein and activity content in order to evaluate the efficiency of the different purification steps, and are also characterised by electrophoresis using non-denaturing and denaturing conditions. Finally, in the third part, the purified enzyme is subjected to comprehensive analysis of its kinetic properties and compared to those of a commercial skeletal muscle LDH preparation. The results presented thereafter are representative of the data-sets obtained by the student-pairs and are comparable to those obtained by the instructors and the reference publications. This multistep purification of an enzyme from its source material, where students perform different purification techniques over successive laboratory days, the characterisation of the purified enzyme, and the extensive approach of enzyme kinetics, naturally fits into a project-based biochemistry learning process.

Using electrophoretic mobility shift assays to measure equilibrium dissociation constants: GAL4‐p53 binding DNA as a model system

An undergraduate biochemistry laboratory experiment is described that will teach students the practical and theoretical considerations for measuring the equilibrium dissociation constant (K(D) ) for a protein/DNA interaction using electrophoretic mobility shift assays (EMSAs). An EMSA monitors the migration of DNA through a native gel; the DNA migrates more slowly when bound to a protein. To determine a K(D) the amount of unbound and protein-bound DNA in the gel is measured as the protein concentration increases. By performing this experiment, students will be introduced to making affinity measurements and gain experience in performing quantitative EMSAs. The experiment describes measuring the K(D) for the interaction between the chimeric protein GAL4-p53 and its DNA recognition site; however, the techniques are adaptable to other DNA binding proteins. In addition, the basic experiment described can be easily expanded to include additional inquiry-driven experimentation. © 2012 by The International Union of Biochemistry and Molecular Biology.

Optical biosensing: Kinetics of protein A‐IGG binding using biolayer interferometry

An undergraduate biochemistry laboratory experiment has been developed using biolayer interferometry (BLI), an optical biosensing technique similar to surface plasmon resonance (SPR), in which students obtain and analyze kinetic data for a protein-protein interaction. Optical biosensing is a technique of choice to determine kinetic and affinity constants for biomolecular interactions. Measurements can be made in real-time without labels, making biosensing particularly appropriate for the teaching laboratory. In the described exercise, students investigate the kinetics of Protein A-human Immunoglobin G binding under conditions that mimic simple 1:1 binding. Students prepare appropriate serial dilutions of IgG and set up a microplate for the experiment by aliquotting biotinylated Protein A, buffer, and IgG solutions. A commercial BLI sensor, the FortéBio Octet QK, is used to measure binding. While data are collected students prepare a spreadsheet with which they will simulate the data to determine k(on) , k(off) , and K(D) . Raw data from the sensor are then exported to the spreadsheets for analysis. Optimized experiment timing, regeneration methods and other parameters are described to increase throughput and reduce cost. The experiment is readily adaptable to other biosensing platforms such as SPR instruments.

Using FRET to measure the angle at which a protein bends DNA

An undergraduate biochemistry laboratory experiment that will teach the technique of fluorescence resonance energy transfer (FRET) while analyzing protein-induced DNA bending is described. The experiment uses the protein TATA binding protein (TBP), which is a general transcription factor that recognizes and binds specific DNA sequences known as TATA boxes. When TBP binds to a TATA box, it bends the DNA. Such bending will be detected using FRET to measure the distance between two fluorophores located on the ends of the DNA. When TBP binds and bends the DNA, the fluorophores move closer together, reflected by an increase in FRET. At the completion of the experiment, three parameters will be determined: 1) the efficiency of the FRET, 2) the end-to-end distance between the fluorophores, and 3) the angle at which TBP bends the DNA. In performing this experiment, students will be introduced to FRET, gain experience in quantitative biophysical measurements, and appreciate how a protein can induce a dramatic change in DNA conformation.

Immunoprecipitation and characterization of membrane protein complexes from yeast*S

AbstractIn this undergraduate biochemistry laboratory experiment, the vacuolar ATPase protein complex is purified from yeast cell extracts by doing immunoprecipitations under nondenaturing conditions. Immunoprecipitations are performed using monoclonal antibodies to facilitate data interpretation, and subunits are separated on the basis of their molecular size by SDS‐PAGE. Both integral membrane and peripheral subunits are detected in Coomassie Blue‐stained gels, and the identity of several subunits are confirmed by Western blots. Western blots serve to illustrate reproducibility and authenticity of the results and help students understand that they could use immunoblotting to detect subunits that are not visualized by Coomassie stain. The molecular mass of the subunits is estimated by their migration relative to molecular marker proteins in the same gel and used to estimate the size of the entire complex. Just like in biochemistry research, students learn to integrate several techniques to solve the subunit composition of a protein complex. These experiments are an alternative to classical protein purification techniques and can be adapted to study most protein complexes composed of membrane‐bound and peripheral subunits from yeast. Instructors can use this approach to teaching proteomics and introduce students to systems biology. Because numerous yeast proteins are epitope tagged, instructors could use commercially available antibodies to study a protein complex of interest.

Purification of Bovine Carbonic Anhydrase by Affinity Chromatography: An Undergraduate Biochemistry Laboratory Experiment

We have developed a rapid and inexpensive experiment utilizing affinity chromatography to isolate carbonic anhydrase (CA) from bovine blood. The more specific an affinity gel is the better the purification, but the greater the cost. Some costs would be prohibitive in the undergraduate biochemistry laboratory. Less specific resins may be more affordable but may bind a number of closely related proteins. One alternative would be to couple a specific ligand to an inexpensive resin such as an ion exchanger. We describe a simple procedure for preparing a sulfonamide-coupled resin which specifically binds CA from a blood hemolysate. The CA is eluted and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). It was found that only a single band of 31 kD was obtained. The instructor can readily prepare the affinity gel prior to the lab, and the students, beginning with packed red blood cells can carry out the lysis, binding to the gel, elution, enzymatic assays, and electrophoresis.

An Analysis of the Involvement of Purine Ribonucleotides in Eukaryotic Protein Synthesis: An Undergraduate Biochemistry Laboratory Experiment

This article presents an interesting and timely experiment that allows students in junior/senior level biochemistry to investigate the purine nucleotide requirements for protein synthesis in a relatively short time frame. The methods do not require any unusual equipment, though the use of radionucleotides (entirely warranted by the nature of the experiment) does require special care.

Separation of glycohemoglobins by ion exchange chromatography: An undergraduate biochemistry laboratory experiment

In this experiment, students determine the glycohemoglobin level of whole blood samples by separation of the glycohemoglobins from the nonglycosylated hemoglobins using cation exchange chromatography.

The determination of vitamin D-dependent calcium binding protein in chick intestine: An undergraduate biochemistry laboratory experiment

The determination of vitamin D-dependent calcium binding protein in chick intestine: An undergraduate biochemistry laboratory experiment

Acid phosphatase characterization: An undergraduate biochemistry laboratory experiment

By systematically varying the general assaying procedure, students can observe reaction velocity as a function of enzyme concentration, reaction velocity as a function of pH, enzyme activity as a function of temperature, and reaction velocity as a function of substrate concentration.