Crystal structure of seleno-L-cystine dihydrochloride

Abstract

Numerous crystal structures are available for the dimeric amino acid cystine. In proteins it is formed by oxidation of the -SH thiol groups of two closely spaced cysteine residues, resulting in the formation of a familiar disulfide bridge. The title compound [systematic name: (R,R)-1,1'-dicarboxy-2,2'-(diselanediyl)-diethanaminium dichloride], C6H14N2O4Se22+ ·2Cl-, is the first example of a small molecule structure of the biologically important analogue with a -CH2-Se-Se-CH2- bridging unit. Bond lengths and angles of seleno-L-cystine dihydrochloride and its isotypic sulfur analogue L-cystine dihydrochloride are compared.