Auer H E, Patton E
Biophys Chem. 1976 Jan;4(1):15-21. doi: 10.1016/0301-4622(76)80002-6.
The kinetics of the transformation of poly(L-tyrosine) from the disordered chain to the intramolecular beta structure in aqueous solution has been studied. The reaction is induced by an isothermal pH jump and is followed by conventional circular dichroism methods. Upon application of curve-fitting procedures, it is found that the kinetics are poorly represented by a single first-order process, but a two-step sequential first-order equation is adequate. Sharp pH-dependent maxima in the phenomenological rate constants and in the fractional amplitude of the rapid step were found. It is proposed to attribute these phenomena to a transition in initial states which is shown to occur over the same pH range within the domain of the disordered-to-beta transition. No sigmoid transient curves were observed, indicating that no slow nucleation events are discernible in this system. These observations contrast strikingly with the mechanism elaborated for beta formation in (Lys)n [R. Hartman et al., J. Mol. Biol. 90 (1974) 415].
研究了聚（L-酪氨酸）在水溶液中从无序链转变为分子内β结构的动力学。该反应由等温pH跃变引发，并采用传统圆二色性方法进行跟踪。应用曲线拟合程序后发现，单一的一级过程不能很好地描述动力学，但两步连续一级方程是合适的。在现象学速率常数和快速步骤的分数幅度中发现了明显的pH依赖性最大值。有人提出将这些现象归因于初始状态的转变，这种转变在无序到β转变范围内的相同pH范围内发生。未观察到S形瞬态曲线，表明在该系统中没有可辨别的缓慢成核事件。这些观察结果与（Lys）n中β形成所阐述的机制形成了鲜明对比[R. Hartman等人，《分子生物学杂志》90（1974）415]。
