Femtosecond Spontaneous-Emission Studies of Reaction Centers From Photosynthetic Bacteria

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 89; no. 18; pp. 8517 - 8521
• Main Authors: Du, Mei, Rosenthal, Sandra J., Xie, Xiaoliang, DiMagno, Theodore J., Schmidt, Mark, Hanson, Deborah K., Schiffer, Marianne, Norris, James R., Fleming, Graham R.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15-09-1992; National Acad Sciences; National Academy of Sciences
• Subjects: Absorption spectra; Bacteria; Biochemistry; Biological and medical sciences; Biology; Bleaching; decay; Electrochemistry; Electron transfer; Energy Transfer; Fluorescence; Fundamental and applied biological sciences. Psychology; Kinetics; Lasers; Molecular biophysics; Photosynthesis; Photosynthetic Reaction Center Complex Proteins - metabolism; Physical chemistry in biology; Physics; reaction centers; Rhodobacter capsulatus; Rhodobacter sphaeroides; Spectrometry, Fluorescence; Spontaneous emission; Stimulated emission; Wavelengths; Rhodobacter capsulatus; Rhodospirillales; Bacteriochlorophyll; Rhodobacter sphaeroides; Reaction center; Decay; Fluorescence; Electron transfer; Bacteria; Rhodospirillaceae; Photosynthesis
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.89.18.8517

Spontaneous emission from reaction centers of photosynthetic bacteria has been recorded with a time resolution of 50 fs. Excitation was made directly into both the special-pair band (850 nm) and the Qxband of bacteriochlorophylls (608 nm). Rhodobacter sphaeroides R26, Rhodobacter capsulatus wild type, and four mutants of Rb. capsulatus were studied. In all cases the fluorescence decay was not single exponential and was well fit as a sum of two exponential decay components. The short components are in excellent agreement with the single component detected by measurements of stimulated emission. The origin of the nonexponential decay is discussed in terms of heterogeneity, the kinetic scheme, and the possibility of slow vibrational relaxation.