Nonequilibrium heating in LHCII complexes monitored by ultrafast absorbance transients.
Nonequilibrium heating in LHCII complexes monitored by ultrafast absorbance transients.
复制标题
通过超快吸收瞬变监测 LHCII 复合物中的非平衡加热。
作者：
V. Gulbinas;R. Karpicz;G. Garab;L. Valkunas
通过在 10 K 到室温的宽温度范围内使用不同的激发强度，研究了 LHCII（植物的主要光捕获复合体）瞬态光谱中非平衡局部加热的证据。在室温下没有发现明显的局部加热现象，而在 10 K 时，当每个 LHCII 三聚体每个脉冲产生超过 10 个激子时，局部加热效应是明显的。在这些条件下，由于激子-激子湮灭，大部分激发能转化为热量。最初，热能分配在叶绿素 a 分子上，在最高激发强度下达到数百度，相当于单个激发脉冲产生的每个三聚体近 100 个激子。非平衡温度的衰减可以用两个指数来很好地表征。冷却的初始阶段很可能是由蛋白质上的热量传播引起的，对应于大约 20 ps 的特征时间常数。随后，冷却速率减慢至大约 200 ps，这与向溶剂的热传递有关。
Evidence of nonequilibrium local heating in transient spectra of LHCII, the main light-harvesting complex of plants, was studied by using various excitation intensities over a wide temperature range, from 10 K to room temperature. No obvious manifestation of local heating was found at room temperature, whereas at 10 K, the local heating effect is discernible when more than 10 excitons per LHCII trimer per pulse are generated. Under these conditions, a major part of the excitation energy is converted into heat as a result of exciton-exciton annihilation. Initially, the heat energy is allocated on chlorophyll a molecules, reaching hundreds of degrees at the highest excitation intensities, which correspond to almost 100 excitons per trimer generated by a single excitation pulse. The decay of the nonequilibrium temperature is characterized well by two exponentials. The initial phase of cooling, which is most likely caused by the spreading of heat over the protein, corresponds to a characteristic time constant of approximately 20 ps. Later, the cooling rate decelerates to approximately 200 ps and is related to heat transfer to the solvent.