The metal complexes of peptides and related compounds. 6. The copper (II) complexes of 6-aminohexanoic acid

✍ Scribed by R. Österberg; B. Toftgård

• Publisher: Elsevier Science
• Year: 1972
• Weight: 799 KB
• Volume: 1
• Category: Article
• ISSN: 0006-3061
• DOI: 10.1016/s0006-3061(00)81004-2

✦ Synopsis

A model compound for protein lysine side chains, 6aminohexanoic acid, forms copper(I1) compkxea in solution only with its dip&r ionic form (HA). This is shown by emf titrations at 25' and 3.0 M NaCIOI medium, using glass and copper amalgam electrodes. The results found are consistent sssuming the following main equilibria: Cur+ + IIA ti Cu(HA)*, Iog Kr = 1.76 f 0.04; CuHA*+ + HA = Cu(HA)t*+ , log Kr = 1.28 zk 0.09. The data are first treated by graphical methods and then by Letagrop, a general least squares computer program. Deviations of the data might be ascribed to smaii analytical errors but may also indicate some minor species; if so, they are C~r(H_4)~4+ and Cu(HA)f+. Aithough copper(D) ions can be bound to the e-amino group of 6aminohexanoic acid, after first being reduced and then reoxidized, the compositions of the present complexes indicate that in solution the carboxylate rather than the e-amino group interacts directly with Cu(I1) ions.