SIDE-CHAIN CONTRIBUTIONS TO THE STABILITY OF ALPHA-HELICAL STRUCTURE IN PEPTIDES

[[abstract]]Short peptides that contain significant α-helical structure in aqueous solution allow the investigation of the role of amino acid side chains in stabilizing or destabilizing α-helix structure. A host-guest system of soluble synthetic peptides was designed that consisted of chains with the block sequence TyrSerGlu$_4$Lys$_4$X$_3$Glu$_4$Lys$_4$, denoted EXK, in which X represents any "guest" amino acid residue. Circular dichroism spectroscopy indicates that the extent of helicity of these peptides follows the order Ala Leu Met Gln Ile Val Ser Thr Asn Gly. This order differs from both host-guest copolymer values (Met Ile Leu Ala Gln Val Thr Asn Ser Gly) and the tendencies of these amino acids to occur in helices in globular proteins (Ala Met Leu Gln Ile Val Asn, Thr Ser Gly), but matches the order found in a series of synthetic coiled-coil α helices, except for Ser. Proton nuclear magnetic resonance analysis of several EXK peptides indicates that these peptides are partially helical, with the helical residues favoring the amino terminus.[[fileno]]2050134010002[[department]]生科