In chemistry, a salt bridge is a combination of two non-covalent interactions: hydrogen bonding and ionic bonding. Ion pairing is one of the most important noncovalent forces in chemistry, in biological systems, in different materials and in many applications such as ion pair chromatography. It is a most commonly observed contribution to the stability to the entropically unfavorable folded conformation of proteins. Although non-covalent interactions are known to be relatively weak interactions, small stabilizing interactions can add up to make an important contribution to the overall stability of a conformer.[1] Not only are salt bridges found in proteins, but they can also be found in supramolecular chemistry. The thermodynamics of each are explored through experimental procedures to access the free energy contribution of the salt bridge to the overall free energy of the state. In proteins, the salt bridge most often arises from the anionic carboxylate (RCOO−) of either aspartic acid or glutamic acid and the cationic ammonium (RNH3+) from lysine or the guanidinium (RNHC(NH2)2+) of arginine. Although these are the most common, other residues with ionizable side chains such as histidine, tyrosine, and serine can also participate, depending on outside factors perturbing their pKa's. The distance between the residues participating in the salt bridge is also cited as being important. The distance required is less than 4 Å. Here you can see a de novo designed protein that contains networks of salt bridges established between arginine and glutamate residues (PDB code: 7P12)
#molecularart ... #immolecular ... #folding ... #protein ... #saltbridge ... #argnine ... #glutamate ... #polarinteraction ... #xray
Structure of the engineered protein with salt bridges rendered with @proteinimaging and depicted with @corelphotopaint
#molecularart ... #immolecular ... #folding ... #protein ... #saltbridge ... #argnine ... #glutamate ... #polarinteraction ... #xray
Structure of the engineered protein with salt bridges rendered with @proteinimaging and depicted with @corelphotopaint
