ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05826.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05827.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05828.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—Moderate u.v.‐doses (2537 Å) sufficient to reduce enzymatic activities of native enzymes up to about 90 per cent, in general do not produce measurable amounts of smaller dialyzable fragments.The disappearance of the original boundary in sedimentation diagrams is mostly due to the formation of rapidly sedimenting polydispersed material. Generally the sedimentation constants of the native proteins are not significantly changed. The boundaries, however, often loose their symmetry. The quantum yields for the disappearance of the original boundaries are roughly inversely proportional to the molecular weights. The number of molecules disappearing from the main peak is smaller than the number of molecules inactivated by a given dose. The data indicate that ultracentrifugation provides no satisfactory method for separation of native molecules from the damaged and inactivated. Proteins with labile quaternary structures (e.g. thyroglobulin or hemocyanine) which tend to dissociate under very mild conditions show an enhanced dissociation after u. v.‐irrad

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05829.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—Photolysis with light of 2537 Å of a series of aliphatic dipeptides in the solid state has been shown to lead to bond rupture and free radical formation. The structures of the radicals have been determined by ESR techniques and in general, the free electron has been shown to reside on the carbon atom attached to the nitrogen atom of the peptide bond. Dipeptides containing phenylalanine residues show ESR spectra typical of the free amino‐acid in the terminal posi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05830.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—Exposure ofE. coliB/r and B at low average dose rates of u.v. radiation (2537 Å), produced either by fractionated doses or by continuous irradiation at a very low dose rate (80 ergs/mm2/hr), results in much increased survival compared to single exposure at high dose rate. This increase is attributed to repair taking place during the irradiation period. The effect is small in the repair‐deficient strainsE. coliB8‐1_, and Csyn‐, and is absent in phage T1 and T4, which cannot undergo repair in the extracellular state. However, the prolonged time available for repair in these experiments accounts for only a very minor part of the increase in survival. The principal factor apparently is that the number of lesions present at any time remains relatively low. Presumably complete repair, not only the excision step, can occur in buffer during the irradiation period. This interpretation is supported by experiments in which cells were exposed to combinations of highly fractionated irradiation and single‐dose irradiation. We therefore propose that mutual interference in repair, possibly by overlapping of repair regions in complementary DNA strands, reduces considerably the repair efficiency if many lesions are present. This hypothesis explains the ‘shouldered’ survival curves of B/r and possibly otherE. colistrains as due to decreasing repair efficiency with incre

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05831.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—Porcine trypsin was inactivated by various methods (heat, autolysis, photodynamic action, ultraviolet light, and gamma‐radiation) and the inactivated products were tested for their ability to precipitate porcine trypsin antiserum using the capillary fluid precipitin method. It was found that the chemical and structural modifications incurred with irradiation, sufficient to inactivate porcine trypsin, in contrast to heat and autolysis, did not interfere with those parts of the protein surface required for immunochemical reactiv

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05832.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—There is considerable evidence that the light‐induced narrow EPR signal I atg= 2·0025 in green algae is a reflection of the turnover of the photosynthetic reaction center, P700. A lag period or induction effect of the formation of this signal, subsequent to a dark period in whole fresh cells, is similar to induction effects for the bleaching of P700. The rate of formation of the signal is slower the longer the preceding dark period. DCMU does not much affect the induction phenomenon, but heating the cells to 60° abolishes it. Some substance or process which exists in the intact cell is altered by light and is detectable by its effect on signal I and on the rate of light‐induced oxidation of P700 and cyt

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05833.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

Abstract—The action spectra for violaxanthin de‐epoxidation and zeaxanthin epoxidation in New Zealand spinach leaf segments,Tetragonia expansa, were determined at equal incident quanta of 2·0 × 1015quanta cm‐2sec‐1. Precise action spectra were not obtained due to variable leaf activity. The de‐epoxidation action spectrum had major peaks at approximately 480 and 648 nm. Blue light was slightly more effective than red light and little activity was observed beyond 700 nm. The epoxidation action spectrum showed major peaks at around 440 and 670 nm. Blue light was more effective than red light and light beyond 700 nm showed definite activity.The net result of de‐epoxidation and epoxidation is a cyclicscheme, the violaxanthin cycle, which consumes O2and photoproducts. The action spectra indicate that the violaxanthin cycle is more active in blue than in red light and therefore could account for O2uptake stimulated by blue light. However, the violaxanthin cycle is not the pathway for O2uptake by photosynthetic system 1. It was suggested that the violaxanthin cycle may function as a pathway for the consumption of excess photoproducts generated in blue light or the conversion of these photo‐products to other

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05834.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb05835.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY