摘要:

ABSTRACT–Quantitative comparison of the decay rate for absorbance photochanges in chromatophores ofR. rubrumat the major wavelengths of peaks and troughs (280, 365, 385, 433, 605, 763, 790, 810, 850, 865, 890 nm) reveal no major differences under a variety of sample conditions. In addition, the decay kinetics of EPR phtochange at the two environmental potentials used in this study are identical with the absorbance ph;otochange decay.Decay curves for fresh chromatophores, aged chromatophores, and fresh chromatophores at high ionic strength display a variety of half times and curve shapes. All of these data however, may be fit (within 10 per cent) by the equation x=αe8.2t+βe0.18tby merely varying the values of α and β. This is interpreted as meaning that any single trapping site may exist in one of two major forms each of which decays following a first order or pseudo‐first order reaction. Although the change in decay pattern upon aging is not reversible, that due to high ionic strength is. The time dependencies for two light emission phenomena have been measured as well as their response to the oxidation state of molecules at the trapping site. A major component of long‐lived luminescence follows pseudo‐second order kinetics with a half time of 38 msec. A very long lived luminescence shows an increse with time which is nearly proportional to the decay of absorbance p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08885.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

ABSTRACT–P‐Type delayed fluorescence and sensitised P‐Type delayed fluorescence have been observed from solutions of chlorophyllsaandbin ethanol. E‐Type delayed fluorescence has been observed from solutions in propylene glycol. The measurements in propylene glycol have yielded approximate values for the triplet energies of chlorophyllsaandb.Measurements of the emissions from the ethanolic solutions have been used to calculate approximate values of the triplet formation efficiencies in this solvent. The sums of the fluorescence and triplet formation efficiencies in ethanol fall far short of unity and the triplet formation efficiencies therefore need to be confirmed by an independent method before they can be accepted with con

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08886.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

ABSTRACTBoth Class I (intact) and Class II (without the outer plastid membrane) chloroplasts ofSpinacea oleraceaexhibit a shrinkage of the thylakoid volume under conditions which lead to the well known light‐induced light scattering increases. In the present report this shrinkage has been measured on micrographs prepared by the freeze‐etch technique. In cloroplasts kept in darkness through the freezing or in those treated with DCMU prior to exposure to red light, the thylakoids are in a slightly swollen condition: in plastids exposed to red light and no inhibitor, the thylakoid membranes are closely appressed, giving the thylakoid a shrunken appearance relative to the control.It is further shown that Class I chloroplasts which are actively fixing CO2do not give appreciable light scattering changes, but lowering the pH away from the optimum for ATP formation (and CO2fixation) or adding the uncoupler quinacrine restores the light‐induced scattering incr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08887.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

ABSTRACTThe sensitivities of U(1) and U(2) TMV strains to inactivation by ultraviolet light at 253.7 nm were compared with those of hybrid viruses obtained by reconstituting the protein of either native strain with the RNA of the other. In each case, the hybrid virus was found to be virtually identical in sensitivity to the native strain which supplied the protein coat, indicating that the relative sensitivities of the two native strains to ultraviolet light are solely a function of their respective protein coats. Amino acid analysis of the U (2) protein reveals about thirteen or fourteen amino acid replacements compared with the U (1) strain, which is in agreement with earlier studies indicating that there are considerable differences in the protein subunits of the two proteins. Some of the ways in which the observed differences in proteins of the two strains may determine their respective ultraviolet sensitivities are discussed.

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08888.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

ABSTRACTWhen cystine is irradiated at pH 1 by 254‐nm u.v. the following yields are observed: 4 cystines → 5.2 cysteines + 2.8NH3. Thus, SH production accounts for only 0.65 of the cystine destruction; further C‐S breakage to give alanine or serine is not efficient. The yields for cystine and glutathione destruction are essentially the same at pH 1. However the presence of the glutamic and glycine residues stabilize the cystine in glutathione so that NH3is not lost until the peptide bonds are hydrolyzed. Increasing the pH from 1 to 8.6 increases the yield of cystine destruction in glutathione by 50 per cent. The yield of cystine destruction is greater in both compounds when O2is present during irradiation (e. g. the cysteic acid yield in glutathione is increased by 50 times). The overall production of SH varies by a factor of 2 in the four proteins‐insulin, RNase, trypsin and lysozyme. The present data further support the earlier observation that radiation damage is quite non‐random in RNase: at least two and perhaps three of the four constituent cystines must be disrupted before activity is lost: i.e. the most radiosensitive cystines are not critical for enzymic activity. Similarly, in both trypsin and lysozyme the integrity of the most radiosensitive cystines also does not appear to be critical for the retention of enzymic potential. In insulin, however, all three cystines appear to be crucial for activity and to have approximately equal radiosensitivities. These differences in sensitivity of cystines in different proteins must depend specifically upon energy transfer and/or chemical interactions between the chromophoric groups. If yields are calculated on the basis of those quanta absorbed only in the cystines, values about 5 to 8 times greater than those in the model compounds cystine and oxixized glutathione are obtained. The yields of cystine destruction are much higher in those protiens which contain tr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08889.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

ABSTRACTEquations are proposed for the estimation of quantum yields for cystine destruction and disulfide protein inactivation during u.v.‐irradiation in acidic and neutral solutions. The formulas permit a discussion of energy transfer from excited aromatic amino acids to cystines and/or of chemical reactions between excited tryptophans or tyrosines and cystines. The results are discussed with regard to general aspects of the photo‐biochemistry of enzy

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb08890.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY