Kinetics of the premelting (L beta'-P beta') and main transition (P beta'-L alpha) in hydrated dipalmitoylphosphatidylcholine. A time-resolved x-ray diffraction study using microwave-induced temperature-jumps.
Kinetics of the premelting (L beta'-P beta') and main transition (P beta'-L alpha) in hydrated dipalmitoylphosphatidylcholine. A time-resolved x-ray diffraction study using microwave-induced temperature-jumps.
复制标题
水合二棕榈酰磷脂酰胆碱中预熔化（L beta-P beta）和主要转变（P beta-L α）的动力学。
DOI：
10.1016/s0006-3495(90)82410-3
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发表时间：
1990
影响因子：
3.4
通讯作者：
Zhang,J
中科院分区：
文献类型：
--
作者：
Caffrey,M;Fanger,G;Magin,RL;Zhang,J
采用微波辐射均匀加热样品，通过低角时间分辨X射线衍射（TRXRD）研究了完全水合二棕榈酰磷脂酰胆碱的预熔融（L β '-P β'）和主转变（P β '-L α）的动力学和机制。平衡和动态方面的过渡进行了研究。动态研究涉及应用足够幅度的温度跃变来依次影响两个转变。我们的研究结果如下。(a)微波辐射已被证明是一种有用的手段，用于实施快速和均匀的内部加热的温度跳跃研究的脂质相变动力学。(b)加热速率可以通过调节微波功率设置来控制。(c)三个溶致相的热膨胀系数遵循顺序L β '不等于0大于P β'远大于L α。(d)无论温度跃变幅度和样品加热速率如何，P β '相总是明显地作为L β'和L α相之间的中间相。(e)P β '相的发展程度与温度跃变幅度和升温速率成反比。(f)对于组合的L β ′-P β ′和P β ′-L α跃迁记录的最短通过时间小于1 s。(g)在从L α相冷却时，链无序/有序转变的开始是明显的，如散射角对时间图中斜率的急剧变化，其被解释为由转变潜热引起的样品加热。(h)基于P β '相的低角衍射图案的形状，P β'-L α转变似乎是可逆的，没有亚稳性的证据，如在Tenchov等人（1989）的慢扫描TRXRD测量中观察到的。Biophys. J. 56：757-768）。
The dynamics and mechanism of the premelting (L beta'-P beta') and main transitions (P beta'-L alpha) in fully hydrated dipalmitoylphosphatidylcholine were examined by low-angle time-resolved x-ray diffraction (TRXRD) using microwave radiation to effect uniform, internal sample heating. Equilibrium and dynamic aspects of the transitions were investigated. The dynamic studies involved applying a temperature jump of sufficient amplitude to effect the two transitions sequentially. Our findings are as follows. (a) Microwave radiation has proven useful as a means for implementing rapid and uniform internal heating in temperature-jump studies of lipid-phase transition kinetics. (b) Heating rate can be controlled by adjusting microwave power setting. (c) The thermal expansion coefficient of the three lyotropic phases follows the sequence L beta' not equal to O greater than P beta' much greater than L alpha. (d) Regardless of temperature-jump amplitude and sample heating rate the P beta' phase was always in evidence as an intermediate between the L beta' and L alpha phases. (e) The degree of development of the P beta' phase was inversely proportional to temperature-jump amplitude and heating rate. (f) The shortest transit time recorded for the combined L beta'-P beta', and P beta'-L alpha transitions was less than 1 s. (g) Upon cooling from the L alpha phase the onset of the chain disorder/order transition was apparent as a dramatic change of slope in the scattering angle vs. time plot which is interpreted as arising from sample heating by the latent heat of the transition. (h) Based on the shape of the low-angle diffraction pattern of the P beta' phase the P beta'-L alpha transition appears to be reversible with no evidence of metastability as was observed in the slow scan TRXRD measurements of Tenchov et al. (1989. Biophys. J. 56:757–768).