| Autor: |
Ujj, L., Devanathan, S., Meyer, T.E., Cusanovich, M.A., Tollin, G., Atkinson, G.H. |
| Zdroj: |
Biophysical Journal; July 1998, Vol. 75 Issue: 1 p406-412, 7p |
| Abstrakt: |
Previous studies have shown that the room temperature photocycle of the photoactive yellow protein (PYP) from Ectothiorhodospira halophila involves at least two intermediate species: I1, which forms in <10ns and decays with a 200-μs lifetime to I2, which itself subsequently returns to the ground state with a 140-ms time constant at pH 7 (Genick et al. 1997. Biochemistry. 36:8–14). Picosecond transient absorption spectroscopy has been used here to reveal a photophysical relaxation process (stimulated emission) and photochemical intermediates in the PYP photocycle that have not been reported previously. The first new intermediate (I0) exhibits maximum absorption at ∼510nm and appears in ≤3ps after 452nm excitation (5ps pulse width) of PYP. Kinetic analysis shows that I0 decays with a 220±20ps lifetime, forming another intermediate (I‡0) that has a similar difference wavelength maximum, but with lower absorptivity. I‡0 decays with a 3±0.15ns time constant to form I1. Stimulated emission from an excited electronic state of PYP is observed both within the 4–6-ps cross-correlation times used in this work, and with a 16-ps delay for all probe wavelengths throughout the 426–525-nm region studied. These transient absorption and emission data provide a more detailed understanding of the mechanistic dynamics occurring during the PYP photocycle. |
| Databáze: |
Supplemental Index |
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