摘要:

Abstract—Aninvestigation was made of the location, function and characteristics of production of carotenoid pigments of a strain ofMycobacterium marinum, an organism which produces its pigments only when exposed to light.It was found that light‐grown cells of this organism contain only one pigment. The intracellular location of this pigment was found to be the cell envelope. The pigment was found to be capable of protecting the cells against lethal photo‐oxidations mediated by the dye, toluidine blue.These studies also revealed that in dark‐grown cells exposed to light, pigment production occurred after a short lag and then remained constant during logarithmic growth. Pigment was produced by starved cells, but to a lesser degree than son‐starved cells; the addition of a carbon or nitrogen source to starved cells increased pigmentation to the level in non‐starved cells. Pigmentation did not occur in the absence of oxygen. Cells exposed to light at 4°C were not pigmented immediately after exposure, but became so if incubated at 30°C. Production of pigment was found to obey the Bunsen‐Roscoe reciprocity law. The determination of an action spectrum for the production of pigment indicates that maximum pigment productiion occurs in the vicinity of 410 and 439 mµ, with smaller maxima in the vicinity of502

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08114.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—The conversion of catecholamines exposed to ultraviolet irradiation has been investigated spectrophotometricaly. The UV activation of the molecule is a direct effect and the activation is not dependent upon the presence of metals. The transformation, which includes mdolization and polymerization requkes the presence of oxygen. The rate of the oxidative transformation is of the same order of magnitude in 100 per cent oxygen as in air, provided a metal chelating agent is present.At neutral pH photoactivated adrenaline is oxidized to adrenochrome and further polymerized to melanin. At alkaline pH U.V. irradiation results in the formation of conversion products of adrenaline, different from those observed at neutral pH, and the melanin production is low.When noradrenaline is subjected to U.V. irradiation at neutral pH the processes of oxidation and polymerization takes place at a much slower rate than that observed for adrenaline. The radiation effect on noradrenaline at alkaline pH is characterized by increased melanin formation.Radicals derived from U.V. irradiation of H2O2convert the catecholamines to different products, and no melanin formation can be recorded.The sequence of reactions leading from the activated catecholamines to indolic structures, and the participation of the indolic structures in melanogenesis from the catecholamines is discusse

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08115.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—Investigations concerning the occurrence of disulphide interchange for disulphides related to cystine are made with either a single unsymmetrical disulphide or an equimolar mixture of two symmetrical disulphides. It is found that in the pH range 1–6 where spontaneous interchange can usually be disregarded, interchange can be initiated by the addition of a small amount of a thiol or by irradiation with ultraviolet light from either of two artificial sources, interchange being more rapid at pH 4–6 than at pH 1–3. Direct sunlight and, to a lesser extent, visible (filtered tungsten) light are also effective. Disulphide interchange in the solid state can also be promoted by ultraviolet light. A comparison is made between the roles' of S‐S and C‐S bond fission in the photochemistry of disulphides, with respect not only to the promotion of disulphide interchange, but to other phenomena such as the dismutation of disulphides to thioethers and t

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08116.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—The ocellar pigment ofSpirocodon sdtatrixwas extracted with 2% mildly alkaline cetyltrimethylammonium bromide (CTAB). The pigment is thermally unstable at pH values of higher than 5 and is a pH‐indicator, Λ max being 480 mµ in strong acid, 430–50 mµ in neutral and mildly acid and alkaline, and 370–90 mµ in strongly alkaline solution. The pigment undergoes changes upon illumination, the maximum loss in density occurring at 490 mµ and the maximini gain, at 300–10 mµ. Formalin‐treated samples become chloroform soluble, in which the pigment is still photosensitive. The Λ max of the maximum gain upon iIlumination is 310–20 mµ. The properties of the ocellar pigment resemble those of known visual pigm

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08117.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—The irradiation of native DNA's by ultraviolet radiation of different wave lengths changes their absorption spectra. The changes are similar to those found for the formation of dimers between adjacent thymines in polynucleotide chains. The decreases in absorbance at 270 mµ produced by 280 mµ irradiation are reversed to a large extent by subsequent 239 mµ irradiation. The magnitude of the absorbance changes produced by large doses of 280 mµ correspond to the formation of dimers between approximately 50 per cent of all the TT sequences in the DNA. An incident dose of 100 erg/mm2of 280 mµ radiation forms about one dimer per molecule of calf thymus DNA of molecular weight 6 times 106. The irradiation of heat‐denatured DNA produces larger absorbance changes than are observed in native DNA. The absorbance changes in denatured DNA arise in part from a heat‐reversible reaction, presumably involving cytidine, part from the formation of thymine dimers, and part from some unknown photoproducts. The reversal of thymine dimers by short wave length irradiation does not pioduce an equivalent change in the melting temperature

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08118.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—Les résultats des expériences réalisées sous différentes conditions d'éclairement et de température ont permis de définer deux processus de germination probablement indépen‐dants: 1°/un processus thermosensible: à l'obscurité la germination ne se produit qu'en alternance de température. L'éfficacité de ces alternances est fonction de l'éart qui existe entre les deux températures et de la valeur de ces deux températures. L'influence des alternances de températures peut être exaItée par un certain nombre de substances: nitrates, nitrites, hydroxylamine et thiourée 2°/un processus photosensible: la lumière rouge clair (630–680 mµ) stimule le germination, par contre la lumière rouge sombre (700–730 mµ) élimine la stimulation due à la lumière rouge clair. L'acide gibbéréllique sensibili

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08119.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08120.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08121.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY