Wu C S, Yang J T
Cardiovascular Research Institute, University of California, San Francisco 94143-0524.
Biopolymers. 1990;30(3-4):381-8. doi: 10.1002/bip.360300315.
The conformation of a 13-residue C-peptide analogue of ribonuclease A, suc-AET-AAAKFLRAHA-CONH2, in NaDodSO4 solutions with respect to temperature was studied with CD. The equilibrium constant of unfolding yielded a straight line in a van't Hoff plot. In 10 mM NaDodSO4, delta G mu = 120 cal/mol, delta H mu = 700 cal/mol, and delta S mu = 2.0 entropy units all on per helical residue. These values compared fairly well with the thermodynamic parameters of the uncharged helix-coil transition of (Glu)n in 0.1 M NaCl based on the theories of Zimm and Bragg and Zimm and Rice. The peptide was not unfolded at 75 degrees C completely. Even in water without surfactant it was not a "random coil."
利用圆二色光谱（CD）研究了核糖核酸酶A的一种13个残基的C肽类似物suc - AET - AAAKFLRAHA - CONH2在含十二烷基硫酸钠（NaDodSO4）溶液中随温度变化的构象。解折叠的平衡常数在范特霍夫图中呈现为一条直线。在10 mM NaDodSO4中，每个螺旋残基的ΔGμ = 120卡/摩尔，ΔHμ = 700卡/摩尔，ΔSμ = 2.0熵单位。基于齐姆（Zimm）和布拉格（Bragg）以及齐姆和赖斯（Rice）的理论，这些值与0.1 M NaCl中（Glu）n的无电荷螺旋 - 随机线团转变的热力学参数相当吻合。该肽在75℃时并未完全解折叠。即使在没有表面活性剂的水中，它也不是“无规线团”。
