Sklar L A, Hudson B S, Petersen M, Diamond J
Biochemistry. 1977 Mar 8;16(5):813-9. doi: 10.1021/bi00624a001.
This paper is the first in a series which extends introductory studies of parinaric acid and its phospholipid derivatives as membrane probes (Sklar, L.A., Hudson, B., and Simoni, R.D. (1975), Proc. Natl. Acad. Sci. after U.S.A. 72, 1649; (1976), J. Supramol. Struct. 4, 449). Parinaric acid has a conjugated tetraene chromophore and exhibits many spectroscopic properties common to linear polyenes. Its absorption spectrum is characterized by a strong near-ultraviolet transition with vibronic structure, which is strongly affected by solvent polarizability. The fluorescence emission occurs at considerably lower energy than the absorption and the wavelength of the emission is nearly independent of the solvent. The fluorescence quantum yield and lifetime are strongly affected by temperature and solvent. These spectral features are interpreted in terms of an excited electronic-state order such that a weak transition occurs at longer wavelengths than the strongly allowed transition which dominates the absorption. The sensitivity of the fluorescence quantum yield an lifetime to environment is shown to be due primarily to variations in the nonradiative rate, although changes in the radiative rate constant are also observed and interpreted. The absorption spectrum (epsilon max greater than 65 000) is in the 300-320-nm range, a region relatively free of absorption due to intrinsic biological chromophores. Shifts of several nanometers are characteristic of different environments. These shifts are compared to similar effects observed for a series of diphenylpolyenes for which new data are given and are correlated using a simple but adequate theory of solvent shifts. The intrinsic (or radiative) fluorescence lifetime is near 100 ns in a wide variety of environments. This is much longer than the intrinsic lifetime calculated from the absorption spectrum and strongly supports the proposed excited-state order.
本文是一系列论文中的第一篇，该系列扩展了对十八碳四烯酸及其磷脂衍生物作为膜探针的初步研究（斯克拉，L.A.，哈德森，B.，和西蒙尼，R.D.（1975年），《美国国家科学院院刊》72卷，第1649页；（1976年），《超分子结构杂志》4卷，第449页）。十八碳四烯酸具有共轭四烯发色团，并表现出许多线性多烯共有的光谱性质。其吸收光谱的特征是在近紫外区有一个强跃迁并伴有振动结构，该结构受溶剂极化率的强烈影响。荧光发射发生在比吸收低得多的能量处，且发射波长几乎与溶剂无关。荧光量子产率和寿命受温度和溶剂的强烈影响。这些光谱特征根据激发电子态的有序性来解释，即弱跃迁发生在比主导吸收的强允许跃迁更长的波长处。虽然也观察到并解释了辐射速率常数的变化，但荧光量子产率和寿命对环境的敏感性主要归因于非辐射速率的变化。吸收光谱（最大吸收系数大于65000）在300 - 320纳米范围内，该区域相对没有因内在生物发色团产生的吸收。几纳米的位移是不同环境的特征。将这些位移与一系列二苯基多烯观察到的类似效应进行比较，给出了新的数据，并使用一个简单但足够的溶剂位移理论进行关联。在各种环境中，固有（或辐射）荧光寿命接近100纳秒。这比根据吸收光谱计算出的固有寿命长得多，有力地支持了所提出的激发态有序性。
