1b:I[76749,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"default"] 1c:I[3486,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"default"] 1d:I[41892,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"default"] 1e:I[17707,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"default"] 1f:I[66528,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"default"] 20:I[63176,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"default"] 21:I[87099,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"default"] 22:I[26200,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"Group"] 23:I[23365,["/_next/static/chunks/0383663887945ae7.js","/_next/static/chunks/df7e62179e4ae938.js","/_next/static/chunks/acf71181277ecf85.js","/_next/static/chunks/63561dcd578bd4db.js","/_next/static/chunks/5bf36002c846d2d8.js","/_next/static/chunks/b24fef6e58c9b2f5.js","/_next/static/chunks/ea1fda2cc52e974e.js"],"default"] 24:T47d,The catalytic center of photosynthetic water oxidation, the Mn₄CaO₅ cluster, is assembled in photosystem II (PSII) through a light-driven process called photoactivation, whose mechanism remains elusive. Here, we used rapid-scan time-resolved Fourier transform infrared (FTIR) spectroscopy combined with the attenuated total reflection (ATR) technique to monitor the photoactivation process. Rapid-scan ATR-FTIR spectra of apo-PSII with Mn²⁺ upon flash illumination showed spectral features typical of carboxylate stretching vibrations, which were attributed to two carboxylate ligands, D1-D170 and D1-E189, by quantum chemical calculations. The FTIR signal decayed with a time constant of ∼0.7 s, showing that the subsequent "dark rearrangement" step occurred with a low quantum yield and Mn³⁺ ions were mostly released during this decay. Simulation of the kinetic process provided a slow intrinsic rate of the dark rearrangement, which was attributed to a large protein conformational change. The photoassembly mechanism of the Mn₄CaO₅ cluster is proposed based on these findings.

Akihiko Sato

Publications