Mar T, Singhal G S, Merkelo H
Biophys J. 1972 Jul;12(7):797-808. doi: 10.1016/S0006-3495(72)86123-X.
Using a mode-locked laser (lambda, 632.8 nm), fluorescence decay of chlorophyll (Chl) a in the green alga Chlorella pyrenoidosa, the red alga Porphyridium cruentum, and the blue-green alga Anacystis nidulans was measured by the phase-shift method under conditions when photosynthesis was not operative (3-(3,4-dichlorophenyl)-1,1-dimethylurea [DCMU] poisoning, or cooling to 77 degrees K). In the presence of 10(-5) M DCMU, the lifetime of Chl a fluorescence (tau) at room temperature is about 1.7 nsec in Chlorella, 1.0 nsec in Porphyridium, and 0.7 nsec in Anacystis. At 77 degrees K, tau is 1.4 nsec (for fluorescence at about 685 nm, F-685) and 2.3 nsec (for F-730) in Chlorella, 0.9 nsec (F-685) and 1.2 nsec (F-730) in Porphyridium, and 0.8 nsec (F-685 and F-730) in Anacystis. From the above measurement, and the assumption that tau(0) (the intrinsic fluorescence lifetime) for Chl a in all three algae is 15.2 nsec, we have calculated the rate constants of radiationless transition (that includes energy transfer to weakly fluorescent system I) processes competing with fluorescence at room temperature to be about 5 x 10(8) sec(-1) in Chlorella, 9 x 10(8) sec(-1) in Porphyridium, and 13 x 10(8) sec(-1) in Anacystis. At 77 degrees K, this rate constant for Chl a that fluoresces at 685 nm remains, in the first approximation, the same as at room temperature. From the tau data, the rate constant for the trapping of excitation energy is calculated to be about 1.2 x 10(9) sec(-1) for Chlorella, 2 x 10(9) sec(-1) for Porphyridium, and 2 x 10(9) sec(-1) for Anacystis. The efficiency of trapping is calculated to be about 66% (Chlorella), 68% (Porphyridium), and 60% (Anacystis). (It is recognized that variations in the above values are to be expected if algae grown under different conditions are used for experimentation.) The maximum quantum yield of Chl a fluorescence for system II (lambda, 632.8 nm), calculated from tau measurements, is about 10% in Chlorella, 6-7% in Porhyridium, and 5% in Anacystis under conditions when photosynthesis is not operative; the values at 77 degrees K appear to be very close to those with DCMU added at room temperature. ø for F-730 at 77 degrees K, however, is somewhat higher than for F-685. The predicted quantum yields of fluorescence for Chl a in intact cells (both systems I and II) at low intensities of 632.8 nm light are about 2-3, 1-2, and 1% for Chlorella, Porphyridium, and Anacystis, respectively.
使用锁模激光器（波长632.8纳米），通过相移法在光合作用不起作用的条件下（3 -（3,4 - 二氯苯基）-1,1 - 二甲基脲[DCMU]中毒，或冷却至77K）测量了绿藻小球藻、红藻紫球藻和蓝藻集胞藻中叶绿素（Chl）a的荧光衰减。在存在10^(-5) M DCMU的情况下，室温下小球藻中Chl a荧光寿命（τ）约为1.7纳秒，紫球藻中为1.0纳秒，集胞藻中为0.7纳秒。在77K时，小球藻中τ为1.4纳秒（对于约685纳米处的荧光，F - 685）和2.3纳秒（对于F - 730），紫球藻中为0.9纳秒（F - 685）和1.2纳秒（F - 730），集胞藻中为0.8纳秒（F - 685和F - 730）。根据上述测量，并假设所有三种藻类中Chl a的τ(0)（固有荧光寿命）为15.2纳秒，我们计算出在室温下与荧光竞争的无辐射跃迁（包括能量转移到弱荧光的光系统I）过程的速率常数在小球藻中约为5×10^8秒^(-1)，紫球藻中为9×10^8秒^(-1)，集胞藻中为13×10^8秒^(-1)。在77K时，685纳米处发出荧光的Chl a的该速率常数在一级近似下与室温时相同。根据τ数据，计算出小球藻中激发能捕获的速率常数约为1.2×10^9秒^(-1)，紫球藻中为2×10^9秒^(-1)，集胞藻中为2×10^9秒^(-1)。捕获效率计算约为66%（小球藻）、68%（紫球藻）和60%（集胞藻）。（认识到如果使用在不同条件下生长的藻类进行实验，上述值会有变化。）在光合作用不起作用的条件下，根据τ测量计算出的光系统II（波长632.8纳米）中Chl a荧光的最大量子产率在小球藻中约为10%，紫球藻中为6 - 7%，集胞藻中为5%；77K时的值似乎与室温下添加DCMU时的值非常接近。然而，77K时F - 730的ø比F - 685的ø略高。在632.8纳米低强度光下，完整细胞（光系统I和II）中Chl a荧光的预测量子产率对于小球藻、紫球藻和集胞藻分别约为2 - 3%、1 - 2%和1%。
