Search results
Results from the WOW.Com Content Network
The pH-dependence of the activity displayed by enzymes and the pH-dependence of protein stability, for example, are properties that are determined by the pK a values of amino acid side chains. The pK a values of an amino acid side chain in solution is typically inferred from the pK a values of model compounds (compounds that are similar to the ...
Also, amino acid side chain affinity for water was measured using vapor phases. [14] Vapor phases represent the simplest non polar phases, because it has no interaction with the solute. [ 18 ] The hydration potential and its correlation to the appearance of amino acids on the surface of proteins was studied by Wolfenden.
For amino acids with uncharged side-chains the zwitterion predominates at pH values between the two pK a values, but coexists in equilibrium with small amounts of net negative and net positive ions. At the midpoint between the two p K a values, the trace amount of net negative and trace of net positive ions balance, so that average net charge ...
For instance, if a stretch of about 20 amino acids shows positive for hydrophobicity, these amino acids may be part of alpha-helix spanning across a lipid bilayer, which is composed of hydrophobic fatty acids. On the converse, amino acids with high hydrophilicity indicate that these residues are in contact with solvent, or water, and that they ...
Amino acid Short Abbrev. Side chain Hydro-phobic pKa § Polar pH Small Tiny Aromatic or Aliphatic van der Waals volume (Å 3) Alanine: A Ala -CH 3 - - Aliphatic 67 Cysteine: C Cys -CH 2 SH: 8.55 acidic - 86 Aspartic acid: D Asp -CH 2 COOH 3.67 acidic - 91 Glutamic acid: E Glu -CH 2 CH 2 COOH 4.25 acidic - 109 Phenylalanine: F Phe -CH 2 C 6 H 5 ...
The N-O distance required is less than 4 Å (400 pm). Amino acids greater than this distance apart do not qualify as forming a salt bridge. [11] Due to the numerous ionizable side chains of amino acids found throughout a protein, the pH at which a protein is placed is crucial to its stability.
Backbone-dependent rotamer library for serine.Each plot shows the population of the χ 1 rotamers of serine as a function of the backbone dihedral angles φ and ψ. In biochemistry, a backbone-dependent rotamer library provides the frequencies, mean dihedral angles, and standard deviations of the discrete conformations (known as rotamers) of the amino acid side chains in proteins as a function ...
Many applications exist in biochemistry; for example, the pK a values of proteins and amino acid side chains are of major importance for the activity of enzymes and the stability of proteins. [67] Protein pK a values cannot always be measured directly, but may be calculated using theoretical methods.