ABSTRACT
The pH-dependence of the O and P intermediates in the photocycle of bacteriorhodopsin (bR) on the intensity and duration of the exciting flash was investigated for bR glycerol suspensions and bR gelatin films. Green and red laser flashes (532 and 670 nm) were utilized to generate a photoequilibrium state of bR and O at ambient temperature, and UV-vis spectroscopy was used to determine the photoconversion for the bR suspensions and films. The maximal concentration of the O intermediate was observed to be pH-dependent and the dependency was most pronounced at a slightly alkaline pH values. The photochemical conversion from the O to P intermediate was investigated for both bR suspensions and films. The P intermediate was only found in bR gelatin film. These results indicate that bR gelatin film may be an attractive candidate for the information storage based on P intermediate. It is possible, with red light, to create photoproducts which are thermally stable at ambient temperature and that can be photochemically erased.
Subject(s)
Bacteriorhodopsins/chemistry , Light , Gelatin/chemistry , Glycerol/chemistry , Hydrogen-Ion Concentration , PhotochemistryABSTRACT
Two kinds of water-soluble and ultraviolet (UV) curable oligomers were synthesized and characterized. The oligomers were evaluated as resins for water-based UV curable coating. The rheology of the two oligomers' aqueous solutions was investigated in terms of solid fraction, pH dependence, and temperature dependence. The solutions were found to be Newtonian fluid showing rather low viscosity even at high solid fraction of 0.55. The drying process of the coatings and the properties of the cured coatings were studied by comparing them with water-dispersed UV-curable polyurethane methyl acrylate. It was evident that the water-soluble coating dried more slowly; and that the overall properties were inferior to those of the water-dispersed coating.
Subject(s)
Acrylic Resins/chemistry , Polyurethanes/chemistry , Ultraviolet Rays , SolubilityABSTRACT
Chemically modified bacteriorhodopsin (BR) films embedded in gelatin matrix were fabricated. It was found that chemically modified BR/gelatin film remained the original conformation of BR and possessed homogeneity. Then, the photochemical conversion from all-trans O state to 9-cis P state in the chemically modified BR film/gelatin was investigated. For comparison purpose, the same conversion in the wild-type BR (BRwt) film was also presented here. To our know, it is the first report to show that the absorption changes of the P state in the chemically modified BR film were larger than in the BRwt film upon illumination with red light at the low actinic power density.
Subject(s)
Bacteriorhodopsins/chemistry , Bacteriorhodopsins/chemical synthesis , Gelatin/chemistry , Ions , Protein Conformation , Protein Engineering , Spectrophotometry , Spectroscopy, Fourier Transform Infrared , Time FactorsABSTRACT
The photochromic retinal protein bacteriorhodopsin (BR) was found in the cell membrane of the Archaean Halobacterium salinarium. The excellent photochromic and photocycle properties of the BR provide the possibility of many applications in the filed of optical information processing. In this paper, the spectrum response characteristic of the wild type bacteriorhodopsin molecule film was studied by using pump-probe method. After the samples was excited by 532 nm YAG laser beam, the absorption spectra were probed by an optical fiber spectrum analysis (OSA). The absorption peaks at the ground state (B state) of the two samples are all at 562 nm wavelength. At 562 nm wavelength, the optical densities (OD) of the samples are about OD (WT1) 562 nm = 2.04 and OD (WT2) 562 nm = 1.37 respectively. The experiment results show that BR(WT) films have absorption that appears to strengthen with the probe time increasing in wavelength 550-650 nm, and this change phenomenon is described by spectra measured at different probe time. Appling the theoretical plot-fit of two exponentials to analyze the process of the absorption change it is found that this change includes two processes-fast process and slow process. Their corresponse time constants of BR(WT1) are about 11 ms and 60 s, and those of BR(WT2) about 24 and 30 s respectively.
Subject(s)
Bacteriorhodopsins/chemistry , Halobacterium salinarum/chemistry , Light , Optics and Photonics , Protein Conformation , Spectrum Analysis/methods , Absorption , Circular Dichroism , Dose-Response Relationship, Radiation , Photochemistry/methods , Spectrum Analysis/statistics & numerical dataABSTRACT
A series of organized (PDAC/PM)(n) (poly(diallyldimethylammonium chloride)/purple membrane) multilayer films were prepared by alternate adsorptions of positively charged PDAC polyelectrolyte and negatively charged purple membrane (PM). The kinetics of the photocycle of bacteriorhodopsin (bR) in PM was studied by flash photolysis and transient photovoltage methods. Although the orientation of the adsorbed bR depends on the pH of the PM suspension, the kinetics of the photo-induced reaction cycle in dehydrated films is independent of the deposition pH. In dry (PDAC/PM)(n) films the decay of the M intermediate to the initial bR state is multiexponential and delayed to several minutes for both orientations. A simultaneous two-exponential decay in millisecond time domain was observed at red wavelengths. The source of the red-shifted absorption is suggested to be the C(610) intermediate of the cis photocycle of bR.
