H2NCH2CONHCH2COOH

H2NCH2CONHCH2COOH is the dipeptide glycylglycine, also known as diglycine. It consists of two glycine residues linked by a single peptide bond, with a free amino group at the N-terminus and a free carboxyl group at the C-terminus. Its molecular formula is C4H8N2O3 and its molecular weight is about 132.12 g/mol. This simple dipeptide is the smallest glycine-containing peptide.

In this molecule, the amide bond is between the carbonyl carbon of the first glycine and the amino nitrogen of the second, forming NH2-CH2-CO-NH-CH2-COOH. The N-terminus is free, while the C-terminus is a carboxyl group. The molecule is zwitterionic at physiological pH, with the amino terminus bearing a positive charge and the carboxyl terminus negative.

Preparation and occurrence: Glycylglycine can be prepared by condensation of two glycine units or by standard peptide synthesis. It also arises as a degradation product of longer polypeptides. In solution, it is highly polar and soluble in water.

Applications: It serves as a model substrate in studies of peptide bond hydrolysis and protease specificity, and as a standard reference compound in amino acid analyses and chromatographic methods such as HPLC and LC-MS.