Low-intensity pump-probe spectroscopy on the B800 to B850 transfer in the light harvesting 2 complex of Rhodobacter sphaeroides

✍ Scribed by René Monshouwer; Iñaki Ortiz de Zarate; Frank van Mourik; Rienk van Grondelle

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 628 KB
• Volume: 246
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(95)01104-h

✦ Synopsis

The isolated LH2 (BSOO-850) complex of Rb. sphaeroides has been studied at 77 K using low-intensity one-colour pump-probe spectroscopy. Delta absorbance transients were measured at several wavelengths within the B800 band. In the red part of the band, the excited BSOO population decays mono-exponentially with a lifetime of about 1.2 f 0.1 ps. More to the blue much faster rates are found which are ascribed to downhill energy-transfer among the BSOO pigments. To our surprise, increasing the average intensity from 4 W/cm' to higher excitation densities significantly slows the decay of B800 * . Since this effect is permanent we conclude that it is due to some form of photodamage. We propose that this observation explains the slower decay reported by others.