摘要:

Abstract—Membrane‐buried proline residues are found in many transport proteins. To study their roles in the structure and function of bacteriorhodopsin (bR), effects of the individual substitutions ofPro–50,Pro–91 andPro–186 on the deprotonation and reprotonation kinetics of the Schiffbase (SB) were determined by flash photolysis. The obtained rate constants and the amplitudes of the slow and fast components were compared with those of ebR (wild‐type bR, the native protein that is expressed inEscherichia coli).The deprotonation rates of PSB were found to be 10 times faster than that of ebR for P50A, P91A and P91G mutants, and 4 times faster for the P50G mutant. These mutations also increased the initial reprotonation rate of the SB, although the overall change in the reprotonation rate is not as significant as that in the deprotonation rate. Our results indicate thatPro–50 andPro–91, as well asPro–186, are important for the proton‐pum

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb02966.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—This paper describes the mutantdkglin the fernCeratopteris richardii,which shows rapid germination in darkness but is markedly inhibited by white light. Action spectra plotted at 10 nm intervals from 400 to 800 nm are presented for germination responses of wild‐type and mutant spores to photon flux densities of 0.004, 0.04 and 0.4 jtmol/mVs. The action spectra for wild‐type spores exhibit a sharp phytochrome‐mediated peak at 660 nm, a broad peak from 670 to 740 nm resulting from an apparent high irradiance response and no germination below 560 nm. In the corresponding action spectra for mutant spores, the blue region displays rather complex fine structure with prominent minima at 450 and 470 nm, which suggests that cryptochrome is unaltered in these spores. The region from 550 to 640 nm shows the greatest inhibition of spore germination, but this region exhibits no obvious fine structure, which argues rather strongly against the possibility of a unique photoreceptor being active in mutant spores. The mutant spectra resemble the wild‐type spectra in the region from 650 to 800 nm, and thus phytochrome seems normal in the mutant spores. Thedkglmutation appears to act late in the phytochrome transduction pathway where a hypothetical coupling protein may regulate the light‐sensitive step in spore

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb02967.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—The ciliated protozoan,Blepharisma,shows an avoidance reaction (step‐up photophobic response) in response to light stimulation. A profile of a gel‐permeation of a crude detergent‐solubilized sample of the cells resulted in several red‐colored fractions. Among these blepharismin‐containing fractions, the fractions III‐V did not contain amino acids. The peak of fraction II monitored by 580 nm absorbance was much smaller. A prominent peak appeared in fraction I, which contained a large amount of amino acids. The absorption spectrum of fraction I was well fitted to the action spectrum of the step‐up photophobic response, although free pigment (blepharismin) also fitted. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of this fraction resulted in a thicker band corresponding to molecular mass of 200 kDa. These results suggest that the 200 kDa chromoprotein (blepharismin‐protein complex) is responsible for the step‐up photophobic response inBlepharisma.The absorption spectrum of free chromophore dissociated from the chromophore‐protein complex was identical to free red pigment termed blepharismin. The absorption spectrum of the other fractions agreed with that of thin‐layer chromatography‐purified red pigment, indicating that the pigments contained in these fractions are free pigment dissociated from the

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb02968.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—This paper reports a new method for monitoring the allomerization reactions of chlorophyllaand pheo‐phytina.Complex mixtures are generated from illuminating pure compounds and monitored using both diode array high‐performance liquid chromatography (DAD‐HPLC) and liquid chromatography‐mass spectrometry (LC‐MS). LC‐MS allows molecular weight and fragment ion analysis of significant HPLC peaks. Five products of the degradation of chlorophyllacan be simultaneously detected in a mixture, namely the monohydroxy allomer, the methoxylactone allomer, pheophytinaand the two corresponding allomers of the pheophytin. It is demonstrated that more than one pathway must be involved in thein vitrophotodegradation of chlorophyllaas shown by the simultaneous existence of several

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb02969.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—The excited singlet state of a deprotonated, reduced flavin [1, 5‐dihydro‐N(3)‐carboxymethyllumiflavin] in aqueous solution at pH 8 has been detected by laser flash photolysis. The broad absorption band maximized at ∼ 490 nm (ε= 9.9 × 103M‐1cm‐1). The lifetime of the transient was found to be 100 ± 15 ps. The lifetime was not affected by the presence of pyrimidine dimers, which would be monomerized under these conditions. A longer‐lived transient, tentatively identified as the solvated electron, was also detected. The neutral reduced flavin did not give a de

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb02970.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—The luminescence emission of singlet molecular oxygen (1O2) generated by bacteriopheophytin a, a near‐infrared‐emitting photosensitizer, was measured using a new high‐sensitivity spectrometer system for time‐ and spectral‐resolved near‐infrared detection. The instrument uses a low energy pulsed nitrogen laser (40 μJ per pulse) to excite the photosensitizer optically and is capable of a time resolution of 40 ns per data point and an instrument response function of 350 ns FWHM (full width at half maximum). The use of a low‐energy (and relatively low cost) source provides sufficient system sensitivity to measure time‐resolved spectra in the near infrared with high spectral and temporal resolution. The simultaneous detection, with high accuracy and repeatability, of both the temporal and spectral dependence of the photoprocesses of1O2generation, especially with near‐infrared‐emitting photosensitizers, may further stimulate the current intensive investigations concerning the activit

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb02971.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb02972.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract—A comparative study was carried out on thein sitususceptibilities to photoinactivation of the photosystem I (PS I) and II (PS II) complexes of spinach thylakoids treated with efficient type II sensitizers. While the presence of the exogenous sensitizers caused a substantial increase in the extent of photoinactivation of whole chain electron transport, it did not affect PS I activity of thylakoids in light but exerted an enhanced photoinactivating effect only on PS II. The measurements of the action spectrum for the inhibition of PS II activity of the sensitizer‐incorporated thylakoids and that for the generation of singlet oxygen (1O2) from them revealed that photosensitized inactivation of PS II is directly related to the photoproduction of1O2in thylakoid membranes. The results obtained in the present work clearly demonstrate an exceptional sensitivity of PS II to1O2, providing circumstantial evidence that high light‐induced damage to PS II may result from photosensitization reactions mediated by1O2, which is not necessarily produced within the PS II co

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1993.tb02973.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY