Breton J, Geacintov N E
Ciba Found Symp. 1978(61):217-36. doi: 10.1002/9780470720431.ch12.
Measurements of the linear dichroism and of the polarization of the fluorescence with oriented chloroplasts have revealed a definite orientation of the pigment molecules with respect to the membrane plane. The Qy transition moments of the chlorophyll a molecules are more closely inclined with respect to this plane for the forms absorbing at longer wavelengths than for those absorbing at shorter wavelengths. The fluorescence depolarization by energy transfer, determined with magnetically-oriented chloroplasts, indicates that the degree of local order increases with wavelength for the different (absorption wavelength) forms of chlorophyll a in vivo. Laser pulses of either picosecond or microsecond duration have been used to probe the emission spectrum, lifetime and quantum yield of fluorescence of chloroplasts at various temperatures. With single picosecond pulses, singlet-singlet annihilations occur within the light-harvesting chlorophyll molecules. In the case of microsecond pulses, triplet excitions act as efficient quenchers of the singlets. By monitoring both the yield of carotenoid triplets and of the fluorescence during and after a laser flash, one can show that the carotenoid triplets account for part of but not all the fluorescence quenching.
对取向叶绿体的线性二色性和荧光偏振的测量揭示了色素分子相对于膜平面的明确取向。叶绿素a分子的Qy跃迁矩对于吸收较长波长的形式比吸收较短波长的形式更紧密地相对于该平面倾斜。用磁取向叶绿体测定的通过能量转移引起的荧光去极化表明，体内不同（吸收波长）形式的叶绿素a的局部有序程度随波长增加。已使用皮秒或微秒持续时间的激光脉冲来探测叶绿体在不同温度下的发射光谱、寿命和荧光量子产率。使用单个皮秒脉冲时，单重态-单重态湮灭发生在捕光叶绿素分子内。在微秒脉冲的情况下，三重态激子是单重态的有效猝灭剂。通过监测激光闪光期间和之后类胡萝卜素三重态的产率和荧光，可以表明类胡萝卜素三重态占部分但不是全部的荧光猝灭。
