Electron donors and acceptors in the initial steps of photosynthesis in purple bacteria: a personal account

Abstract

The discovery by Louis N. M. Duysens in the 1950s that illumination of photosynthetic purple bacteria can cause oxidation of either a bacteriochlorophyll complex (P) or a cytochrome was followed by an extended period of uncertainty as to which of these processes was the 'primary' photochemical reaction. Similar questions arose later about the roles of bacteriopheophytin (BPh) and quinones as the initial electron acceptor. This is a personal account of kinetic measurements that showed that electron transfer from P to BPh occurs in the initial step, and that the oxidized bacteriochlorophyll complex (P + ) then oxidizes the cytochrome while the reduced BPh transfers an electron to a quinone.Abbreviations: BChl -bacteriochlorophyll; P -the BChl complex that serves as electron donor in the initial electron-transfer step of photosynthesis in purple bacteria; P + -the oxidized form of P The primary electron donorAs a predoctoral student at

Charge-Gating Dibenzothiophene-S,S-dioxide Bridges in Electron Donor–Bridge–Acceptor Conjugates

“…[1][2][3][4][5][6][7][8][9][10][11] These studies are also important as models for the stepwise charge-transfer processes in complex naturally occurring systems, such as the photosynthesis reaction center. [12][13][14][15] It is, therefore, of paramount importance to understand the effects of systematically varying the chemical structure and length of the bridge in new DBA systems, where the bridge mediates the electronic coupling between donor-and acceptor moieties over large distances. 4, [16][17][18][19][20][21][22][23][24] Coupling typically decays exponentially with increasing distance between the D and A termini, 25 as reflected by the electron-transfer rate constant k ET .…”

Time Line of Discoveries: Anoxygenic Bacterial Photosynthesis

“…W. Parson uses kinetic spectroscopy on chromatophore membranes of C. vinosum to establish that P870 oxidation is the primary reaction in bacterial photosynthesis, and that a cytochrome is oxidized as P870 + is rereduced (Parson 1968). See also Parson (2003).…”

“…These states are later identified as the chargeseparated state P870 + BPh − and the triplet state of P870, respectively (Parson et al 1975). See also Parson (2003).…”

Time line of discoveries: anoxygenic bacterial photosynthesis

“…Parson uses kinetic spectroscopy on chromatophore membranes of C. vinosum to establish that P870 oxidation is the primary reaction in bacterial photosynthesis, and that a cytochrome is oxidized as P870 + is rereduced (Parson 1968). See also Parson (2003). …”

“…These states are later identified as the chargeseparated state P870 + BPh − and the triplet state of P870, respectively . See also Parson (2003).…”