The Mechanisms of Electrogenic Reactions in Bacterial Photosynthetic Reaction Centers: Studies in Collaboration with Alexander Konstantinov.

In this review, we discuss our studies conducted in 1985-1988 in collaboration with A. A. Konstantinov, one of the top scientists in the field of membrane bioenergetics. Studying fast kinetics of membrane potential generation in photosynthetic reaction centers (RCs) of purple bacteria in response to a laser flash has made it possible to examine in detail the mechanisms of electrogenic reactions at the donor and acceptor sides of RCs. Electrogenesis associated with the intraprotein electron transfer from the exogenous secondary donors, redox dyes, and soluble cytochrome (cyt) c to the photooxidized dimer of bacteriochlorophyll P870 was studied using proteoliposomes containing RCs from the non-sulfur purple bacterium Rhodospirillum rubrum. It was found that reduction of the secondary quinone electron acceptor QB accompanied by its protonation in the chromatophores from R. rubrum in response to every second light flash was electrogenic. Spectral characteristics and redox potentials of the four hemes in the tightly bound cyt c in the RC of Blastochloris viridis and electrogenic reactions associated with the electron transfer within the RC complex were identified. For the first time, relative amplitudes of the membrane potential generated in the course of individual electrogenic reactions were compared with the distances between the redox cofactors determined based on the three-dimensional structure of the Bl. viridis RC.

Unique features of the 'photo-energetics' of purple bacteria: a critical survey by the late Aleksandr Yuryevich Borisov (1930-2019).

We provide here an edited version of the "Farewell discussion" by the late Aleksandr (Alex) Yuryevich (Yu) Borisov (1930-2019) on several aspects related to the excitation energy transfer in photosynthetic bacteria. It is preceded by a prolog giving the events that led to our decision to publish it. Further, we include here a few photographs to give a personal glimpse of this unique biophysicist of our time. In addition, we provide here a reminiscence, by Andrei B. Rubin, on the scientific beginnings of Borisov. This article follows a Tribute to Borisov by Semenov et al. (2019, Photosynthesis Research, this issue).

Tribute in memory of Jacques Breton (1942-2018).

Jacques Breton spent his 39 years of professional life at Saclay, a center of the French Atomic Energy Commission. He studied photosynthesis with various advanced biophysical tools, often developed by himself and his numerous coworkers, obtaining a large number of new information on the structure and the functioning of antenna and of reaction centers of plants and bacteria: excitation migration in the antenna, orientation of molecules, rate of primary reactions, binding of pigments and electron transfer cofactors. Although it is much too short to illustrate his impressive work, we hope that this contribution will help maintaining the souvenir of Jacques Breton as an active and enthusiastic person, full of qualities, devoted to research and to his family as well. We include personal comments from N. E. Geacintov, A. Dobek, W. Leibl, M. Vos and W. W. Parson.

Stories and photographs of William A. Arnold (1904-2001), a pioneer of photosynthesis and a wonderful friend.

William A. Arnold discovered many phenomena in photosynthesis. In 1932, together with Robert Emerson, he provided the first experimental data that led to the concept of a large antenna and a few reaction centers (photosynthetic unit); in 1935, he obtained the minimum quantum requirement of 8-10 for the evolution of one O2 molecule; in 1951, together with Bernard L. Strehler, he discovered delayed fluorescence (also known as delayed light emission) in photosynthetic systems; and in 1956, together with Helen Sherwood, he discovered thermoluminescence in plants. He is also known for providing a solid-state picture of photosynthesis. Much has been written about him and his research, including many articles in a special issue of Photosynthesis Research (Govindjee et al. (eds.) 1996); and a biography of Arnold, by Govindjee and Srivastava (William Archibald Arnold (1904-2001), 2014), in the Biographical Memoirs of the US National Academy of Sciences, (Washington, DC). Our article here offers a glimpse into the everyday life, through stories and photographs, of this remarkable scientist.

Picosecond spectroscopy of the isolated reaction centers from the photosystems of oxygenic photosynthesis--ten years (1987-1997) of fun : a tribute to Michael R. Wasielewski on his 60th birthday.

Mike Wasielewski's pioneering work on Photosystem II photochemistry has an important place in the history of photosynthesis; we are proud to have been associated with him in making those first measurements. Here, we present our association and publications with him, and provide some of the history behind this research.