Crystal structure of seleno- L -cystine dihydrochloride

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], C 6 H 14 N 2 O 4 Se 2 2+ ·2Cl − , is the first example of a small molecule structure of the biologically important analogue with a —CH 2 —Se—Se—CH 2 — bridging unit. Bond lengths and angles of seleno-L-cystine dihydrochloride and its isotypic sulfur analogue L-cystine dihydrochloride are compared.