ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06553.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Virus‐host cell interactions may be investigated by study of the enhancement of infectivity of ultraviolet (UV)‐irradiated virus obtained by UV‐irradiating the host cell [ultraviolet reactivation (UVR)]. This phenomenon was studied withHerpes simplexvirus and normal (embryonic lung) and malignant (HeLa) human cells. Although the lung cells displayed no UVR, both the HeLa cells and a Sendai‐virus carrier culture of HeLa cells demonstrated UVR capabilities. This UVR persisted at equal or increased levels for at least 24 h. Since the lung cells and HeLa cells have similar host‐cell‐reactivation (HCR) abilities, the differences in UVR suggests that UVR and HCR may operate by differe

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06554.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The action spectrum for inactivation of the capacity of stationary‐phaseEscherichia coliB to support the growth of T7 bacteriophage was measured, using radiation 240–405 nm in wavelength. The action spectrum has a minimum at 254 nm, a maximum at 267 nm, and a shoulder between 313 and 334 nm, followed by a decrease at longer wavelengths, indicating that nucleic acid is probably not the target for capacity inactivation. Deoxycytidine, cytidine, thiamine, and some proteins have absorption spectra similar to the far‐ultraviolet (240–300 nm) portion of this action

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06555.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Photochemical reactions of cationic acridine orange (AO+) in aqueous solution were studied using the flash photolysis technique. Complete conversion to the triplet state was achieved. The triplet dye decays by first‐ and second‐order reactions, which partly regenerate the dye in the ground state and partly produce semi‐oxidized and semi‐reduced acridine orange. These radical species are formed by an electron‐transfer mechanism between two triplet molecules. The radicals recombine rapidly to give the dye in the ground state. An efficient photooxidation reaction is observed in acridine orange solution containing ferric ions. Semi‐oxidized dye is formed in high yield by reaction between the triplet and the oxidant; the semi‐oxidized radicals disappear, yielding permanent photoproducts. Tetra‐methylparaphenylene diamine (TMPD) reacts efficiently with the acridine orange triplet to give the semi‐reduced dye and the semi‐oxidized form of TMPD; this reduction was found to be reversible. Absorption spectra of the transient species were determined and rate constants for the observed reactions measured. The results are compared with results from a previous study of ne

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06556.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Ultraviolet‐radiation photolysis of thymine in the presence of cysteine gives rise to four isomeric dimers, dihydrothymine, and at least five cysteine addition products. Similar reactions occur for uracil but the products have not all been characterized in detail. The addition reactions arise from the triplet state of the pyrimidine. The initial step is production of a hydropyrimidine radical, which then reacts with cysteine to give the addition products. The triplet is quenched by cysteine with a rate constant of about 2 times 108M‐1s‐1for thymine and 2–9 times 108for uracil. The total yield of products gives a lower‐limit estimate of the triplet yield and hence of the intersystem‐crossing efficiency. These studies, combined with earlier determinations of dimer yields, show that 93% of the thymine triplets which interact with another thymine molecule are quenched without forming stable dimers. For uracil, the corresponding

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06557.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The triplet states of then‐butyl‐amine Schiff bases of 11‐cis, 9‐cis, 13‐cisand all‐transretinal are produced via triplet‐triplet energy transfer. Their absorption spectra, peaking around 435 nm, and their decay kinetics are recorded using pulsed‐laser photolysis. Direct‐excitation (φDISO) and triplet‐sensitized (φTISO) photoisomerization yields, determined using steady irradiation methods, are found to be: φTISO(9‐cis) = 0.06, φTISO(11‐cis) = 045, φTISO(13‐cis) = 008, φTISO(all‐trans) = 0.02‐0.05, φDISO(11‐cis, = (4 ± 1) × 10‐3, φDISO(all‐trans) = (2 ± 1) × 10‐3. The possible role of the triplet s

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06558.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Phytochrome (Pfr)‐mediated threshold control of apparent lipoxygenase (LOG) synthesis in the cotyledons of the mustard seedling depends on the presence of the hypocotylar hook. With isolated cotyledons, no suppression by light of apparent LOG synthesis can be detected. As soon as the cotyledons are separated from the hook, the control of apparent LOG synthesis byPfris completely lost. The data are consistent with the hypothesis advanced in a previous paper [Oelze‐Karow, H. and H. Mohr (1973)Photochem. Photobiol.18,319–330] that apparent LOG synthesis in the cotyledons is controlled by phytochrome located in the hypocotylar hook. The data support the concept [De Greef, J. A. and R. Caubergs (1972)Arch. Int. Physiol. Biochim.80,959–960] that a very precise and highly ordered biophysical recognition and transmission system of light signals exists

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06559.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Our recent research on photochemiluminescence (PCL) of pigments in solutions is reviewed. PCL was observed in the course of photooxidation by oxygen of chlorophylla, bacteriochlorophyll, protochlorophyll, their analogs, synthetic dyes and aromatic hydrocarbons. The PCL of chlorophyll was studied in detail. It depends on oxygen concentration, intensity of exciting light, pH, nature of pigments, solvents etc. The thermochemiluminescence was observed after illumination of liquid and solid pigment solutions at low temperature (down to ‐ 170d̀C). The excitation spectra of PCL coincide with the pigment absorption spectra. The PCL emission spectra in most cases differ from those of pigment fluorescence. Electron acceptors, electron donors, radical inhibitors and β‐carotene quench PCL. The quenching efficiency of electron acceptors is similar to their action on the chlorophyll triplet state. The quenching effect of radical inhibitors and β‐carotene correlates with their activity in reaction with singlet oxygen. The effect of quenchers on the chlorophyll fluorescence, photobleaching and pigment sensitized oxygenation was studied. Analysis of experimental data allowed the assumption that chemiluminescence accompanies the decomposition of labile pigment peroxides. The accumulation of peroxides is probably due to the reaction in the complex of pigment and singlet oxygen, formed as a result of energy transfer from photoexcited (triplet) pigment molecules to oxygen. The terminal chemiluminescence emission proceeds from the singlet excited states of molecules of pigments and products of their

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06560.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The dose response curve for light (phytochrome)‐induced anthocyanin synthesis was determined in the mustard seedling. The curve gives the amount of anthocyanin (A) synthesized within 24 h as a function of the amount of Pfr* produced by a brief light pulse. The [Pfr] response curve is composed of two linear parts with very different slopes (a1,2) connected by a relatively narrow transient range (curved segment). The [Pfr] response curve extrapolates precisely through zero [Pfr]. The reciprocity law is valid over the whole range investigated (up to 320 s of irradiation). It is concluded that the initial (or primary) reaction of Pfr(Pfr+ X → PfrX) does not involve any significant cooperativity in the case of phytochrome‐mediated anthocyanin synthesis. It is speculated that the linear parts of the [Pfr] response curve truly reflect the mode of phytochrome action (A=a1,2[Pfr]; X does not come into play since it isnotrate limiting) whereas the curved segment represents a transition of the reaction matrix of Pfr. The large difference between a1and a2seems to indicate that the physiological effectiveness of a given amount of Pfr(or PfrX) is determined by [Pfr] through a Pfr‐induced change in the reacti

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06561.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The effects of ultraviolet irradiation of double‐stranded synthetic polynucleotides containing BrU and A have been investigated. Homopolymer pairs and alternating copolymers composed of either ribo‐ or deoxyribo‐nucleotides were prepared and were irradiated with either 313 nm or ˜ 285 nm light. Strand separation and a modest amount of strand breakage followed irradiation of the homopolymer pairs. Changes in the ultraviolet absorption spectra of the polymers during irradiation reflected the sum of hyperchromic increases caused by progressive strand separation and loss of absorbance caused by photoproduct formation. Extensive debromination occurred. An RNase digest of irradiated poly(rA)–poly14C(rBrU), analysed by column chromatography, showed components similar to those found previously upon irradiation of single‐stranded poly(rBrU). Little photoproduct was released by RNase digestion as mononucleotides. The major photoproduct was in the dinucleotide fraction, and may be 5,5′‐diuracil. Base sequence had a profound effect on the sensitivity of the polynucleotides. Irradiation of alternating copolymers with doses of light comparable to those that produced major photochemical changes in the homopolymer pairs brought about little if any change in the copolymers of alternati

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1974.tb06562.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY