Pörschke D
Nucleic Acids Res. 1980 Apr 11;8(7):1591-612. doi: 10.1093/nar/8.7.1591.
The binding of LysTrpLys to single stranded poly(A) was studied by measurements of fluorescence, UV-absorbance, electrodichroism and field jump relaxation. The van't Hoff enthalpy determined at constant degree of peptide protonation is -3.5 kcal/mol (delta S = 9 e.u.). The electrodichroism of bound tryptophane residues is negative; its absolute value decreases with increasing degree of binding theta. The magnitude of the dichroism at low theta indicates a preferential orientation of the tryptophane residues in the plane of the adenine bases, suggesting stacking of Trp with adenine bases. The overall degree of orientation decreases, however, to virtually zero at high theta. Relaxation measurements by low theta demonstrate the existence of two steps in the binding reaction of LysTrpLys to poly(A): a fast bimolecular step controlled by diffusion is followed by a slow intramolecular conversion with a forward rate of 1.5 x 10(5) s-1 and a backward rate of 2.7 x 10(3) s-1. The forward rate is close to that expected for an insertion reaction into stacked poly(A), yet the corresponding stability constant (approximately 55) is unexpectedly high.
通过荧光、紫外吸收、电二色性和场跃弛豫测量研究了LysTrpLys与单链聚腺苷酸（poly(A)）的结合。在肽质子化程度恒定的情况下测定的范特霍夫焓为-3.5千卡/摩尔（ΔS = 9熵单位）。结合的色氨酸残基的电二色性为负；其绝对值随结合度θ的增加而降低。低θ时二色性的大小表明色氨酸残基在腺嘌呤碱基平面内优先取向，表明色氨酸与腺嘌呤碱基发生了堆积。然而，在高θ时，整体取向程度降低到几乎为零。低θ时的弛豫测量表明，LysTrpLys与poly(A)的结合反应存在两个步骤：由扩散控制的快速双分子步骤之后是缓慢的分子内转化，正向速率为1.5×10⁵秒⁻¹，反向速率为2.7×10³秒⁻¹。正向速率接近插入堆积的poly(A)中的反应预期速率，但相应的稳定常数（约55）却出乎意料地高。
