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Ultrafast events in the folding of ferrocytochrome c

机译：折叠Ferrocytochrome C中的超快事件

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Laser flash photolysis and stopped-flow methods have been used to study the dynamic events in the micro- to millisecond time bin in the refolding of horse ferrocytochrome c in the full range of guanidine hydrochloride concentration at pH 12.8 (+/- 0.1), 22 degrees C. Under the absolute refolding condition, the earliest relaxation time of the unfolded protein chain is less than 1 mu s. The chain then undergoes diffusive dynamics-mediated contraction and expansion, in which intrapolypeptide ligands make transient contacts with the heme iron, giving rise to two distinct kinetic phases of similar to 0.4 and similar to 3 mu s. Under moderate to absolute refolding conditions, the rates of these processes show little dependence on the denaturant concentration, indicating the absence of structural element in the incipient or the relaxed state. Chain expansion and contraction events continue until the polypeptide finds a stable and supportive transition state. The crossing of this transition barrier, which rate-limits the folding of alkaline ferrocytochrome c, is characterized by a stopped-flow measured time constant of similar to 3 ms in aqueous solvent. Observed kinetics thus implicate no submillisecond folding structure. The folding kinetics is effectively two state in which the unfolded polypeptide first relaxes to an unstructured chain and then crosses over a late rate-limiting barrier to achieve the native conformation. The experimentally observed rates as a function of guanidine hydrochloride concentration have been simulated by numerically calculated microscopic rates of a simple kinetic model that captures the essential features of folding.
机译：激光闪光光解和停止流动方法已被用于研究微量至毫秒的时间箱中的动态事件，以在pH12.8（+/- 0.1），22的全系列盐酸盐酸盐浓度的全系列胍盐酸盐浓度下在绝对的重折叠条件下，展开蛋白质链的最早的弛豫时间小于1亩。然后将链条经历扩散动力学介导的收缩和膨胀，其中肺泡配体与血红素铁产生瞬态接触，产生两个类似于0.4的不同动力学相位，类似于3亩。在中等至绝对重量条件下，这些方法的速率依赖于变性剂浓度，表明初始或松弛状态的结构元素的不存在。链膨胀和收缩事件持续，直到多肽发现稳定和支持性的过渡状态。这种过渡屏障的交叉率限制碱性二氧化物COCOCHROMS C的折叠，其特征在于，在水性溶剂中相似的止动流测量的时间常数。因此，观察到的动力学造成没有潜在的折叠结构。折叠动力学有效地是两个状态，其中展开的多肽首先放松到非结构化链中，然后在后期限速屏障上穿过以实现天然构象。通过数值计算的简单动力学模型的数值计算的微观速率模拟了作为盐酸盐酸盐浓度的函数的实验观察到的速率。

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