Frackowiak D, Zelent B, Malak H, Cegielski R, Goc J, Niedbalska M, Ptak A
Institute of Physics, Poznań University of Technology, Poland.
Biophys Chem. 1995 Apr;54(2):95-107. doi: 10.1016/0301-4622(94)00118-4.
Fluorescence lifetime in the ps range, polarized absorption, polarized fluorescence spectra and delayed luminescence time resolved spectra were measured for chlorophyll a solutions with and without beta-carotene addition in nematic liquid crystal. Photoacoustic spectra of the same samples at various frequencies of light modulation were also taken. The frequency dependence of the photoacoustic spectra suggests that part of the excitation is converted into heat in a slow process (with a decay time of the order of ms). The lifetime results suggest that at used concentration some aggregation of the chlorophyll a occurs. The chlorophyll a molecules interact strongly with the beta-carotene forming some nonfluorescent or weakly fluorescent aggregates characterized by having various thermal deactivation yields and orientations in anisotropic matrix when compared to those of separated pigments. It seems that the aggregated forms of the chlorophylls are partially disrupted as a result of the their interaction with the beta-carotene. Singlet excitation of beta-carotene is not transferred to the fluorescent form of chlorophyll a. Delayed (in microsecond time range) luminescence of chlorophyll a is quenched by beta-carotene. This luminescence is located in the same spectral region as prompt fluorescence. Interactions between chlorophyll a and beta-carotene depend on the degree of pigment orientation and their aggregation.
测量了向列型液晶中添加和未添加β-胡萝卜素的叶绿素a溶液在皮秒范围内的荧光寿命、偏振吸收、偏振荧光光谱以及延迟发光时间分辨光谱。还获取了相同样品在不同光调制频率下的光声光谱。光声光谱的频率依赖性表明，部分激发在一个缓慢过程（衰减时间约为毫秒量级）中转化为热量。寿命结果表明，在所使用的浓度下，叶绿素a会发生一些聚集。叶绿素a分子与β-胡萝卜素强烈相互作用，形成一些非荧光或弱荧光聚集体，与分离的色素相比，这些聚集体在各向异性基质中具有不同的热失活产率和取向。似乎叶绿素的聚集形式由于与β-胡萝卜素的相互作用而部分被破坏。β-胡萝卜素的单线态激发不会转移到叶绿素a的荧光形式。叶绿素a的延迟（微秒时间范围内）发光被β-胡萝卜素淬灭。这种发光位于与即时荧光相同的光谱区域。叶绿素a与β-胡萝卜素之间的相互作用取决于色素的取向程度及其聚集情况。
