Thomas John Wydrzynski (8 July 1947-16 March 2018).

With this Tribute, we remember and honor Thomas John (Tom) Wydrzynski. Tom was a highly innovative, independent and committed researcher, who had, early in his career, defined his life-long research goal. He was committed to understand how Photosystem II produces molecular oxygen from water, using the energy of sunlight, and to apply this knowledge towards making artificial systems. In this tribute, we summarize his research journey, which involved working on 'soft money' in several laboratories around the world for many years, as well as his research achievements. We also reflect upon his approach to life, science and student supervision, as we perceive it. Tom was not only a thoughtful scientist that inspired many to enter this field of research, but also a wonderful supervisor and friend, who is deeply missed (see footnote*).

Remembering George Feher (1924-2017).

We provide a tribute to George Feher, one of the founding scientists in the use of biophysical techniques to probe photosynthetic complexes, especially the bacterial reaction center. His early life is briefly reviewed followed by a description of the impact of his 30 years of photosynthesis research. We describe his pioneering work in bacterial photosynthesis that helped to provide a detailed picture of the molecular events responsible for light energy capture and the subsequent electron and proton transfer events in photosynthetic organisms. These studies had a profound and lasting impact on our understanding of the molecular mechanisms of photosynthesis. We also include some personal comments from his former students and colleagues.

On the history of phyto-photo UV science (not to be left in skoto toto and silence).

This review of the history of ultraviolet photobiology focuses on the effects of UV-B (280-315 nm) radiation on terrestrial plants. It describes the early history of ultraviolet photobiology, the discovery of DNA as a major ultraviolet target and the discovery of photoreactivation and photolyases, and the later identification of Photosystem II as another important target for damage to plants by UV-B radiation. Some experimental techniques are briefly outlined. The insight that the ozone layer was thinning spurred the interest in physiological and ecological effects of UV-B radiation and resulted in an exponential increase over time in the number of publications and citations until 1998, at which time it was realized by the research community that the Montreal Protocol regulating the pollution of the atmosphere with ozone depleting substances was effective. From then on, the publication and citation rate has continued to rise exponentially, but with an abrupt change to lower exponents. We have now entered a phase when more emphasis is put on the "positive" effects of UV-B radiation, and with more emphasis on regulation than on damage and inhibition.

Warwick Hillier: a tribute.

Warwick Hillier (October 18, 1967-January 10, 2014) made seminal contributions to our understanding of photosynthetic water oxidation employing membrane inlet mass spectrometry and FTIR spectroscopy. This article offers a collection of historical perspectives on the scientific impact of Warwick Hillier's work and tributes to the personal impact his life and ideas had on his collaborators and colleagues.

A tribute to Achim Trebst, a friend.

I honor here a friend, Achim Trebst, on his 80th birthday on June 9, 2009. I have known his outstanding research, on the biochemistry of photosynthesis, for years. My brief tribute, which includes personal, scientific and a cultural component, is followed by excellent tributes by Volker ter Meulen and Rudolf K. Thauer, by Heinrich Strotmann, and by Walter Oettmeier (this issue).

Water, water everywhere, and its remarkable chemistry.

Photosystem II (PSII), the multisubunit pigment-protein complex localised in the thylakoid membranes of oxygenic photosynthetic organisms, uses light energy to drive a series of remarkable reactions leading to the oxidation of water. The products of this oxidation are dioxygen, which is released to the atmosphere, and reducing equivalents destined to reduce carbon dioxide to organic molecules. The water oxidation occurs at catalytic sites composed of four manganese atoms (Mn(4)-cluster) and powered by the redox potential of an oxidised chlorophyll a molecule (P680(*+)). Gerald T (Jerry) Babcock and colleagues showed that electron/proton transfer processes from substrate water to P680(*+) involved a tyrosine residue (Y(Z)) and proposed an attractive reaction mechanism for the direct involvement of Y(Z) in the chemistry of water oxidation. The 'hydrogen-atom abstract/metalloradical' mechanism he formulated is an expression of his genius and a highlight of his many other outstanding contributions to photosynthesis research. A structural basis for Jerry's model is now being revealed by X-ray crystallography.

The water-oxidation complex in photosynthesis.

Studies of the photosynthetic water-oxidation complex of photosystem II (PS II) using spectroscopic techniques have characterized not only important structural features, but also changes that occur in oxidation state of the Mn(4) cluster and in its internal organization during the accumulation of oxidizing equivalents leading to O(2) formation. Combining this spectroscopic information with that from the recently published relatively low-resolution X-ray diffraction studies, we have succeeded in limiting the range of likely cluster arrangements. This evidence strongly supports several options proposed earlier by DeRose et al. [J. Am. Chem. Soc. 116 (1994) 5239] and these can be further narrowed using compatibility with electron paramagnetic resonance (EPR) data.

Photosynthetic water oxidation: the role of tyrosine radicals.

This mini-review outlines the involvement of the tyrosine electron carriers, Y(D) and Y(Z), in the mechanism of electron transfer from water to P680. We discuss our data and put forward our ideas on the role of Y(D) and Y(Z).