Open AccessFemtosecond coherent transient infrared spectroscopy of reaction centers from Rhodobacter sphaeroides.
Author(s) -
Sudipta Maiti,
Gilbert C. Walker,
B. R. Cowen,
R. S. Pippenger,
Christopher C. Moser,
P. Leslie Dutton,
Robin M. Hochstrasser
Publication year - 1994
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.91.22.10360
Subject(s) - rhodobacter sphaeroides , photoexcitation , ultrafast laser spectroscopy , photosynthetic reaction centre , chemistry , spectroscopy , femtosecond , vibrational energy relaxation , infrared spectroscopy , dephasing , infrared , electron transfer , atomic physics , photochemistry , analytical chemistry (journal) , excited state , physics , photosynthesis , optics , laser , biochemistry , organic chemistry , quantum mechanics , chromatography
Protein and cofactor vibrational dynamics associated with photoexcitation and charge separation in the photosynthetic reaction center were investigated with femto-second (300-400 fs) time-resolved infrared (1560-1960 cm-1) spectroscopy. The experiments are in the coherent transient limit where the quantum uncertainty principle governs the evolution of the protein vibrational changes. No significant protein relaxation accompanies charge separation, although the electric field resulting from charge separation modifies the polypeptide carbonyl spectra. The potential energy surfaces of the "special pair" P and the photoexcited singlet state P* and environmental perturbations on them are similar as judged from coherence transfer measurements. The vibrational dephasing time of P* modes in this region is 600 fs. A subpicosecond transient at 1665 cm-1 was found to have the kinetics expected for a sequential electron transfer process. Kinetic signatures of all other transient intermediates, P, P*, and P+, participating in the primary steps of photosynthesis were identified in the difference infrared spectra.