Solid State Conformational Studies of Hexamethylene Initiated Oligo e-Carbobenzoxy-L-Lysine
The IUP Journal of Chemistry, Vol. IV, No. 3, September 2011, pp. 34-40
Posted: 5 Jul 2012
Date Written: September 2011
N-Carboxyanhydride (NCA) of -carbobenzoxy-L-lysine is polymerized using hexamethylenediamine as initiator. The monomer to initiator ratio was adjusted 30, 40 and 60. As hexamethylenediamine has amino group (NH2) on either end, the polymerization proceeds in both the directions leading to a polypeptide with a hexamethylene moiety in the center and polypeptide chain on either side. On end-group analysis, the Degree of Polymerization (DP) on either side of hexamethylene moiety of the three systems was found to be 15, 19 and 29. The three systems are represented as ( -CBZ-K)n-HMDA-( -CBZ-K)n: n = 15, 19 and 29. The conformation of the films of all the three oligopeptides were studied using X-ray diffraction, Circular Dichroism (CD) and IR spectroscopy. Conformational studies of the films indicated clearly that invariably a -component is present in all the three oligopeptides. When the chain length is smaller, contribution of -component is larger. The second component present is -helix. When the chain length increased from 15 to 29 -helix component also increased.
Keywords: -carbobenzoxy-L-lysine, X-ray diffraction, Circular Dichroism (CD), IR spectroscopy, -component, Hexamethylene moiety
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