Femtosecond time-resolved spectroscopy of the primary photochemistry of phytochrome

✍ Scribed by Frank Andel III; K. C. Hasson; Feng Gai; Philip A. Anfinrud; Richard A. Mathies

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 259 KB
• Volume: 3
• Category: Article
• ISSN: 1075-4261
• DOI: 10.1002/(sici)1520-6343(1997)3:6<421::aid-bspy1>3.0.co;2-3

✦ Synopsis

Time-resolved absorption spectra of P r phytochrome were obtained using a regeneratively amplified femtosecond titanium : sapphire laser system. The early time transient absorption spectra are comprised of prompt P r photobleaching, stimulated emission, and excited-state absorption features that decay with a 24 ps time constant that matches the ground state appearance time of the primary photoproduct. Based on the 5 ns radiative lifetime calculated from the absorption and spontaneous emission spectra and the fluorescence quantum yield of 5.5 ( { 0.5) 1 10 03 , we calculate an excited-state lifetime of 28 ps that agrees well with the directly determined lifetime. The transient absorption spectra are consistent with a primary photochemical reaction quantum yield of 0.15, and the absorption spectrum of the primary photoproduct closely resembles that of the low-temperature trapped intermediate, lumi-R. We conclude that the primary photoisomerization, which is believed to be a Z,syn r E,syn isomerization of the C 15 |C 16 chromophore bond, occurs in 24 ps.