Picosecond time-resolved absorption and fluorescence dynamics in the artificial bacteriorhodopsin pigment BR6.11

T. L. Brack, J. K. Delaney, G. H. Atkinson, A. Albeck, M. Sheves, M. Ottolenghi

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The picosecond molecular dynamics in an artificial bacteriorhodopsin (BR) pigment containing a structurally modified all-trans retinal chromphore with a six-membered ring bridging the C11=C12-C13 positions (BR6.11) are measured by picosecond transient absorption and picosecond time-resolved fluorescence spectroscopy. Time-dependent intensity and spectral changes in absorption in the 570–650-nm region are monitored for delays as long as 5 ns after the 7-ps, 573-nm excitation of BR6.11. Two intermediates, J6.11 and K6.11/1, both with enhanced absorption to the red (> 600 nm) of the BR6.11 spectrum are observed within approximately 50 ps. The J6.11 intermediate decays with a time constant of 12 +/- 3 ps to form K6.11/1. The K6.11/1 intermediate decays with an approximately 100-ps time constant to form a third intermediate, K6.11/2, which is observed through diminished 650-nm absorption (relative to that of K6.11/1). No other transient absorption changes are found during the remainder of the initial 5-ns period of the BR6.11 photoreaction. Fluorescence in the 650–900-nm region is observed from BR6.11, K6.11/1, and K6.11/2, but no emission assignable to J6.11 is found. The BR6.11 fluroescence spectrum has a approximately 725-nm maximum which is blue-shifted by approximately 15 nm relative to that of native BR-570 and is 4.2 +/- 1.5 times larger in intensity (same sample optical density). No differences in the profile of the fluorescence spectra of BR6.11 and the intermediates K6.11/1 and K6.11/2 are observed. Following ground-state depletion of the BR6.11 population, the time-resolved fluroescence intensity monitored at 725 nm increases with two time constants, 12 +/- 3 and approximately 100 ps, both of which correlate well with changes in the picosecond transient absorption data.(ABSTRACT TRUNCATED AT 250 WORDS)

Original languageEnglish
Pages (from-to)964-972
Number of pages9
JournalBiophysical Journal
Volume65
Issue number2
DOIs
StatePublished - 1993
Externally publishedYes

Bibliographical note

Funding Information:
The authors wish to gratefully acknowledge the technical assistance of Peter Schmidt and Dr. J. P. Jiang in recording these data and the efforts of Scott Rex, Michael Stringer, James Schmeits, and Peter Cho in the preparation of bacteriorhodopsin samples. This work was supported by grants from the biophysics program of the National Science Foundation and the United States-Israel Binational Sci- ence Foundation.

Fingerprint

Dive into the research topics of 'Picosecond time-resolved absorption and fluorescence dynamics in the artificial bacteriorhodopsin pigment BR6.11'. Together they form a unique fingerprint.

Cite this