摘要:

Abstract—We have shown previously that the viability ofE. coliB.U.‐andE. coliB. try‐could be restored after u.v.‐irradiation if post‐irradiation incubation took place in the presence of chloramphenicol or in the absence of an essential metabolite. By way of contrast, the viability of the u.v.‐irradiatedE. coliK.12meth‐decreased rapidly during post‐irradiation incubation in the presence of chloramphenicol or in the absence of methionine. During the study of the biosynthesis of nucleic acids and protein in the above strains we made the following observations.Protein synthesis was permanently inhibited in both amino acid requiring strains during post‐irradiation incubation in the absence of the respective essential metabolite. InE. coliB.U.‐a slow synthesis of protein could be observed even if post‐irradiation incubation took place in the absence of uracil.DNA synthesis was completely and permanently inhibited in bothE. coliB. try‐andE. coliK.12meth‐during post‐irradiation incubation in the absence of the respective essential amino acid. InE. coliB.U.‐, however, DNA synthesis resumed after a prolonged lag even if the bacteria were incubated after u.v.‐irradiation in the absence of uracil.RNA synthesis was completely and permanently inhibited in bothE. coliB. mutants, the uracil requiring and the tryptophan requiring, if they were incubated after irradiation in the absence of uracil and tryptophan respectively. InE. coliK.12meth‐a small amount of RNA is synthesized during post‐irradiation incubation in the

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05786.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Abstract—For use with very intense light source, e.g. flash lamps and high‐pressure arcs, some new stable transmission filters for the U.V. were developed. All filters were composed to give maximum transmittance in the desired bands together with optimum absorbance of the visible light, at an optical path of 1 cm. The filters described are easy to prepare and have considerably better properties than the well known NiSO4‐‐CoSO4filter and other filter combinations.During initial irradiation with high‐intensity light sources the transmittance of the freshly prepared filter solutions increases slowly till maximum transmittance is attained. The position of the transmission bands, however, does not change.Based on the fact that the 6700 Å absorption band of some non‐aqueous solutions of CoCl2has an extinction coefficient about a hundred times larger than the 5100 Å absorption band of the aqueous solution with the same concentration, filter solutions were developed for the following transmission bands: 2600–3900 Å, 2900–3900 Å and 3100–3900 Å with transmission maxima of 90, 90 and 75 per cent respectively, and 2600–4600 Å, 2900–4500 Å and 3100–4600 Å with transmission maxima of 95, 95 and 90 per cent respectiv

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05787.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Abstract—The dye‐sensitized photodegradation of ovalbumin is shown to involve the reduction of light‐excited dye molecules by the substrate. The photodynamic denaturation of ovalbumin, therefore, results both from attack by ‘dye‐peroxide’ molecules (as is the case when the substrate can not act as a photoreductant) and from attack by OH radicals which are generated by re‐oxidation in the dark of the photoreduced dye molecules. Cysteine, histidine, methionhe, tyrosineand tryptophan can act as photoreductants formethylene blue, thionine and proflavine. Photodynamic denaturation of ovalbumin results in a decrease in solubility of the protein at its isoelectric point, and changes its immunologic

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05788.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Abstract—Clear‐plaque mutations of phagekof Serratia are induced by extracellular u.v.‐irradiation in a 2–hit process. The 2–hit‐nature cannot be due to induction of one hit in each of the two DNA‐strands since replating the contents of 97 wildtype plaques of u.v.‐survivors (u.v.‐dose 4.5 min) revealed only 1 case of heterozygosity; at least 20 cases would have been expected if phage with 1–hit‐mutations formed phages looking like wildtype. On the other hand, only 1 case of heterozygosity was observed among replatings of 94c‐mutants induced by the u.v.‐dose 4.5 min (survival 10‐3); most of the plaques contained purec‐type. The purec‐mutant clones are very probably due to ‘recessive’ lethal lesions in the nonpremutated DNA‐strand. This is indicated by the dose dependence of the frequency of heterozygotes; at a dose of 3 min u.v. (survival 1.2 × 10‐‐2) 9 heterozygotes were observed among 95 mutants tested. From these numbers the rate of induction by u.v. of the recessive lesions's can be calculated. The data at the higher dose are in satisfactory agreement with the calculated rate. Also other types of plaque mutations (e,t, b) showed heterozygosity. Two cases of abnormal heterozygosity were observed; one contained 2 stable mutant types (c

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05789.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

摘要:

Abstract—Restoration of viability of E. coli B U‐ after a total dose of 900 ergs/mm2 U.V. in the presence of chloramphenicol and in the absence of uracil was studied. Both treatments result in the recovery of the same fraction of the irradiated bacterial population. There is no additive effect if both treatments are applied to the same irradiated cult

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05790.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05791.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05792.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05793.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05794.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1966.tb05796.x

出版商:Blackwell Publishing Ltd    

年代:1966

数据来源: WILEY