Often when a protein has been gently denatured and then is returned to normal physiological conditions of temperature, pH, salt concentration, etc., it spontaneously regains its function (e.g. A denatured antibody no longer can bind its antigen.When a protein is denatured, it loses its function. None of these agents breaks peptide bonds, so the primary structure of a protein remains intact when it is denatured. presence of reducing agents (break S-S bonds between cysteines).changes in temperature (higher temperatures reduce the strength of hydrogen bonds).changes in salt concentration (does the same).changes in pH (alters electrostatic interactions between charged amino acids).A number of agents can disrupt this structure thus denaturing the protein. The function of a protein (except when it is serving as food) is absolutely dependent on its three-dimensional structure. The sequence of amino acids in a protein is determined by the sequence of nucleotides in the gene (DNA) encoding it.The shape of a protein is determined by its primary structure (sequence of amino acids).
The function of a protein is determined by its shape.A chemical chaperone just might be the difference between a failed experiment and a successful one.Rules of Protein Structure The Rules of Protein Structure The best chaperones are usually found experimentally, so I encourage you to experiment with them. What kind of chemical chaperone you choose is up to you. upregulation of endogenous folding systems using chemicals or heat, which in turn promote global protein folding.pharmacological chaperones, which are designed to promote the folding of a specific protein or to lock them into a stable form.In addition to chemical chaperones, there are several other methods and manipulations to promote protein folding. So bear this in mind if you do decide to use a chemical chaperone. Some argue that the use of chemical chaperones alters native protein structure, thereby compromising the biologic relevancy of your experiment. So, as with anything, there is a downside to using chemical chaperone. When You Should NOT Use Chemical Chaperones In vitro enzymatic reactions (restriction enzyme digests, phosphorylations, etc).Īnd of course you may need to use a chemical chaperone as a control if you are studying protein folding and/or chaperone functions.You should consider giving a chemical chaperone a whirl if things just aren’t working out with your… But apparently BSA may be doing more than that! BSA has a propensity to non-specifically promote protein folding and reduce protein aggregation. I used to think excess BSA was added to samples just to prevent proteins-of-interest from sticking to the sides of the tube. BSA is often added to protein preparations and enzymatic reactions, such as antibodies and restriction enzyme digests. Structure of glycerol, one of the most commonly used chemical chaperones.Īnother favorite atypical “chemical” chaperone choice is the protein BSA (bovine serum albumin). However, glycerol is not just added to prevent freezing – lots of things could do that (such as ethanol) – glycerol is added because it also promotes protein stability by directly permitting energetically favorable interactions of the protein with water.įigure 1. Glycerol prevents freeze/thaw cycles by lowering the freezing point of the solution. Glycerol is often added to commercially purchased enzymes and proteins that are stored below freezing. The most often used chemical chaperone is glycerol. Commonly used chemical chaperones include: This promotes protein solubility, and prevents aggregation and heat-induced denaturation. This allows them bind both to the hydrophobic sites on your protein and simultaneously hydrogen bond with the surrounding water of your buffer. They are amphipathic in nature: that is they contain both hydrophilic and hydrophobic properties. To overcome this problem chemical chaperones are often added to extraction and storage buffers.Ĭhemical chaperones are naturally occurring molecules that are often upregulated in vivo during times of stress. Once your proteins-of-interest are extracted away from the natural folding systems of the cell (which centers on protein chaperones), they become susceptible to unfolding. If a protein isn’t folded correctly, hydrophobic regions of the protein are exposed causing aggregation, degradation and insolubility. Read this article to appreciate the love that chemical chaperones bathe on your proteins and learn when to use them!Ī chemical chaperone is a molecule that promotes the favorable interaction of protein with water in a nonspecific manner.Īs we all remember from Protein Chemistry 101 a major driving force in protein folding and solubility is the hydrophobic effect. From buffers to storage solutions, chemical chaperones silently make proteins happy and soluble. Chemical chaperones are necessary in protein experiments.
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