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E Rabinowitch

Publications and source records attributed to E Rabinowitch.

11 recordsLinked to original sources
PubMed1969

Measurement of the fluorescence lifetime of chlorophyll a in vivo.

New measurements have been made of fluorescence lifetime (tau) of chlorophyll a in the algae Chlorella pyrenoidosa, Porphyridium cruentum, Anacystis nidulans, and in spinach chloroplast. tau-values of 0.6 and 0.7 nsec were obtained with green plants. Anacystis and Porphyridium gave a tau of 0.5 nsec. The previously described two stage decay of fluorescence in vivo in these organisms could not be confirmed. This observation could have been caused by a second wave of light emission from the exciting hydrogen lamp (not detected in earlier work). The lifetimes found in this study (calculated, as before, by the method of convolution integrals) were close to those found by other observers for "low" excitation intensities; the value first reported from this laboratory (1.0-1.7 nsec) may have corresponded to "high" excitation intensity.

Chlorophyll↗
PubMed1968

Red drop in the quantum yield of fluorescence of sonicated algae.

The change of the quantum yield of fluorescence, Phi, with the frequency of exciting light, was investigated in Chlorella, Anacystis, and Porphyridium suspensions, and in sonicates from these cells prepared under aerobic and anaerobic conditions. In case of Chlorella, sonicates were made in acid and in alkaline media (pH 4.65 and 7.80). In the alkaline medium, a drop of Phi towards the longer waves was found to begin at 1.466 x 10(4) cm(-1) (682 nm) in sonicates, and in suspension. In the acid medium, the drop began at 1.471 x 10(4) cm(-1) (680 nm), 1.418 x 10(4) cm(-1) (705 nm), and 1.389 x 10(4) cm(-1) (720 nm) in suspension, anaerobic sonicate, and aerobic sonicate, respectively. The results indicate that the cause of the change in the red drop is preferential destruction of a long-wave component of chlorophyll a (such as Chl a 693). The amount of this component remaining after sonication is larger in alkaline than in acid sonicates. With Anacystis and Porphyridium, only alkaline suspensions (pH 7.80) could be used for sonication, because in acid medium, the phycobilin-chlorophyll complex is rapidly broken and phycobilin extracted from the cell. In Anacystis, the red drop begins at 1.562 x 10(4) cm(-1) (640 nm) and 1.538 x 10(4) cm(-1) (650 nm) in suspension and sonicate, respectively; in Porphyridium, it starts at 1.550 x 10(4) cm(-1) (645 nm) in both cases. These results suggest that sonication in alkaline medium (pH 7.80) destroys some Chl a 693 in Anacystis, but not in Porphyridium.

Eukaryota↗
PubMed1965

Fluorescence decay studies of chlorophyll A in vivo.

The study of the fluorescence of chlorophyll a offers a useful approach toward better understanding of the primary act of photosynthesis. This paper describes new measurements of the decay of chlorophyll a fluorescence in vivo, made with a considerably improved oscilloscopic-display technique. The main result is the identification of two decay periods both of the order of a few nanoseconds. Possible interpretations of this phenomenon are discussed.

Chlorophyll↗