The Laser-Induced Blue State of Bacteriorhodopsin: Mechanistic and Color Regulatory Roles of Protein-Protein Interactions, Protein-Lipid Interactions, and Metal Ions
详细信息 查看全文
- 作者：Mark B. Masthay ; David M. Sammeth ; Merritt C. Helvenston ; Charles B. Buckman ; Wuyi Li ; Michael J. Cde-Baca ; and John T. Kofron
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：April 3, 2002
- 年：2002
- 卷：124
- 期：13
- 页码：3418 - 3430
- 全文大小：212K
- 年卷期：v.124,no.13(April 3, 2002)
- ISSN：1520-5126
文摘
In this paper we characterize the mechanistic roles of the crystalline purple membrane (PM)lattice, the earliest bacteriorhodopsin (BR) photocycle intermediates, and divalent cations in the conversionof PM to laser-induced blue membrane (LIBM; 
max = 605 nm) upon irradiation with intense 532 nm pulsesby contrasting the photoconversion of PM with that of monomeric BR solubilized in reduced Triton X-100detergent. Monomeric BR forms a previously unreported colorless monomer photoproduct which lacks achromophore band in the visible region but manifests a new band centered near 360 nm similar to the 360nm band in LIBM. The 360 nm band in both LIBM and colorless monomer originates from a Schiff base-reduced retinyl chromophore which remains covalently linked to bacterioopsin. Both the PM
LIBM andmonomercolorless monomer photoconversions are mediated by similar biphotonic mechanisms, indicatingthat the photochemistry is localized within single BR monomers and is not influenced by BR-BR interactions.The excessively large two-photon absorptivities (
106 cm4 s molecule-1 photon-1) of these photoconversions,the temporal and spectral characteristics of pulses which generate LIBM in high yield, and an action spectrumfor the PMLIBM photoconversion all indicate that the PMLIBM and MonCMon photoconversions areboth mediated by a sequential biphotonic mechanism in which 
journals/jacsat/124/i13/eqn/ja010116ae10001.gif"> is the intermediate which absorbs thesecond photon. The purpleblue color change results from subsequent conformational perturbations ofthe PM lattice which induce the removal of Ca2+ and Mg2+ ions from the PM surface.
max = 605 nm) upon irradiation with intense 532 nm pulsesby contrasting the photoconversion of PM with that of monomeric BR solubilized in reduced Triton X-100detergent. Monomeric BR forms a previously unreported colorless monomer photoproduct which lacks achromophore band in the visible region but manifests a new band centered near 360 nm similar to the 360nm band in LIBM. The 360 nm band in both LIBM and colorless monomer originates from a Schiff base-reduced retinyl chromophore which remains covalently linked to bacterioopsin. Both the PMLIBM andmonomercolorless monomer photoconversions are mediated by similar biphotonic mechanisms, indicatingthat the photochemistry is localized within single BR monomers and is not influenced by BR-BR interactions.The excessively large two-photon absorptivities (106 cm4 s molecule-1 photon-1) of these photoconversions,the temporal and spectral characteristics of pulses which generate LIBM in high yield, and an action spectrumfor the PMLIBM photoconversion all indicate that the PMLIBM and MonCMon photoconversions areboth mediated by a sequential biphotonic mechanism in which blue color change results from subsequent conformational perturbations ofthe PM lattice which induce the removal of Ca2+ and Mg2+ ions from the PM surface.