Their folding into distinct three-dimensional structures
Where are the functional properties of proteins derived from?
Specific polypeptide sequence
What is each protein fold based on?
the temperature at which proteins unfold
hydrogen bonding, van der Waals, hydrophobicity, protein hydration
What are the non-covalent factors in protein stabilization?
a summation of the van der waals attractive forces among nonpolar groups in the protein interior, which change the surrounding water structure necessary to accommodate these groups if they become exposed
Ionic bond that depends strongly on the sharing of a proton between two electronegative atoms
Between a protein atom and water molecule or as protein intramolecular hydrogen bonds
Where may hydrogen bonds form?
Which force occurs between any two charged groups?
Van der waals interactions
Interaction between atoms that arise from net attractive interactions between permanent dipoles and/or induced dipoles
When hydrogen bonds between water and protein surface stabilize
Denaturation, surface adsorption, aggregation, precipitation
What are some of the causes of the physical instability of proteins?
Unfolding or unnatural refolding, changes in hydrogen bonding, changes in hydrophobic interactions
What are some results from the physical instability of proteins?
The alteration of the global fold of a native molecule
characterized by the adhesion of proteins to surfaces (i.e. insulin)
protein molecules when placed in aqueous solutions may self-associate resulting in the formation of dimmers, tetramers, hexamers, and also macromolecular aggregates
the macroscopic equivalent of aggregation that occurs in conjunction with denaturation
Hydrolysis, oxidation, racemization, disulfide exchange
What are some causes of chemical instability of proteins?
When water molecules attack a bond and cause cleavage in the peptide bond
In strong acids or in weak acids with high temperature
Where may hydrolysis occur?
the hydrolysis of the side chain on a glutamine or asparagine residue
Introduce an additional negative charge which may alter tertiary structure
What is the result of deamidation?
Aromatic side chains, methionine, cysteine
Which molecules are susceptible to oxidation?
Interactions with molecular oxygen, hydrogen peroxide, free radicals
What are some causes of oxidation?
Temperature, pH, buffers, catalysts, oxygen tension, amino acid neighbors
What can influence oxidation?
process of conversion of L-amino acids to D, L-mixtures and occurs through a carbanion intermediate
Alters biological activity
What may racemization alter?
what prevents disulfide exchange?
what catalyzes disulfide exchange?
Aggregation, surface adsorption, precipitation
What may result from noncovalent changes to a protein
Deamidation, racemization, oxidation, hydrolysis, disulfide exchange
What may result from covalent changes to a protein?
protein unfolding and then refolding in a non-native form
in addition to shearing, causes foaming or an increase in the air-liquid interface and oxidation
Which analysis is used to determine the molecular weight of proteins?
B-mercaptoethanol, dithiothreitol, sodium dodecyl sulfate
Which chemicals are used in SDS-PAGE?
Western blotting or immunoblotting
Used to determine with a specific primary antibody, the relative amounts of the protein present in different samples
These combine the specificity of antibodies with the sensitivity of simple enzyme assays, by using antibodies or antigens coupled to an easily-assayed enzyme