Michigan State University, Department of Chemistry, East Lansing, Michigan 48824-1322, USA.
J Phys Chem B. 2010 Nov 4;114(43):13703-9. doi: 10.1021/jp1045723.
We have investigated the molecular reorientation dynamics of perylene incorporated into the nonpolar acyl chain region of 100 nm diameter phosphocholine unilamellar vesicles. When perylene is excited to the S(1) electronic manifold, it exhibits a different fluorescence anisotropy decay than when it is excited to its S(2) electronic manifold. In addition to differences in the polarization of the two transitions, there is a difference in the amount of excitation energy dissipated nonradiatively, because for both excitation conditions radiative emission is from the S(1) state. The data reveal a faster rotational diffusion constant for excitation to the S(2) manifold, and we interpret this finding in the context of local heating of the chromophore immediate environment by the nonradiative dissipation of energy associated with rapid relaxation from the S(2) to S(1) manifolds. Our results are consistent with transient heating on the order of 4 K, with the actual temperature increase depending subtly on whether the phospholipid acyl chains are in the gel phase or the fluid phase.
我们研究了芘分子在直径为 100nm 的磷酸胆碱单层囊泡非极性酰链区的分子重定向动力学。当芘被激发到 S(1)电子态时，其荧光各向异性衰减与被激发到 S(2)电子态时不同。除了两个跃迁的极化差异之外，非辐射耗散的激发能量也存在差异，因为对于两种激发条件，辐射发射都来自 S(1)态。数据显示，激发到 S(2)态的旋转扩散常数更快，我们根据与从 S(2)到 S(1)态的快速弛豫相关的非辐射能量耗散引起的发色团近环境的局部加热，对这一发现进行了解释。我们的结果与约 4K 的瞬态加热一致，实际的温度升高取决于磷脂酰链是处于凝胶相还是流体相，这取决于微妙的情况。
