The alphabet of intrinsic disorder: II. Various roles of glutamic acid in ordered and intrinsically disordered proteins

Uversky, Vladimir N

Hydrogen bond (H-bond) is another non-covalent bond. This interaction depends on the sharing of one hydrogen atom (H-atom) between two other atoms, where the H-atom has a covalent bond to one of them (which therefore serves as the H-bond donor), and where the other atom, to which the H-atom has a weaker bond, serves as the acceptor, A. Hydrogen bond is weaker than a covalent bond but stronger than a van der Waals bond. Similar to electrostatic interactions, H-bonds can easily be broken and reformed. Among established geometrical criteria for H-bond are a set of optimal distances between the non-H atom of donor and acceptor (Dono-Acceptor < 3.9 Ã…) and between the H atom of donor and acceptor (H-Acceptor < 2.5 Ã…). 65 Being negatively charged at physiological pH, glutamic acid can serve as a hydrogen bond acceptor, whereas at acidic pH, it also can be a hydrogen bond donor.