ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Poly(L-arginine) assumes the α-helix in the presence of the tetrahedral-type anions or some polyanions by forming the “ringed-structure bridge” between guanidinium groups and anions which is stabilized by a pair of hydrogen bonds and electrostatic interaction [Ichimura, S., Mita, K. & Zama, M. (1978) Biopolymers 17, 2769-2782; Mita, K., Ichimura, S. & Zama, M. (1978) Biopolymers 17, 2783-2798]. This paper describes the parallel CD studies on the conformational effects on poly (L-homoarginine) of various mono-, di-, polyvalent anions and some polyanions, as well as alcohol and sodium dodecylsulfate. The random coil to α-helix transition of poly(L-homoarginine) occurred only in NaClO4 solution or in the presence of high content of ethanol or methanol. The divalent and polyvalent anions of the tetrahedral type (SO42-, HPO42-, and P2O74-), which are strong α-helix-forming agents for poly(L-arginine), failed to induce the α-helical conformation of poly(L-homoarginine). By complexing with poly(L-glutamic acid) or with polyacrylate, which is also a strong α-helix-forming agent for poly(L-arginine), poly(L-homoarginine) only partially formed the α-helical conformation. Monovalent anions (OH-, Cl-, F-, and H2PO4-) did not change poly(L-homoarginine) to the α-helix, and in the range of pH 2-11, the polypeptide remained in an unordered conformation. In sodium dodecylsulfate, poly(L-homoarginine) exhibited the remarkably enlarged CD spectrum of an extended conformation, while poly(L-arginine) forms the α-helix by interacting with the agent. Thus poly(L-homoarginine), compared with poly(L-arginine), has a much lower ability to form the α-helical conformation by interacting with anions. The stronger hydrophobicity of homoarginine residue in comparison with the arginine residue would provide unfavorable conditions to maintain the α-helical conformation.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1980.360190603
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