bluuebunny/crossref_metadata_2025_split huggingface dataset:
PHOTOSENSITIZED INACTIVATION OF E. COLI CELLS IN TOLUIDINE BLUE‐LIGHT SYSTEM
Authors: Wakayama Yoshiko , Takagi Masamichi , Yano Keiji 
Published: January 2008

Abstract— E. coli cells were inactivated with visible light in the presence of toluidine blue as a photo‐sensitizer. This photodynamic effect was partially protected with α‐tocopherol. Not only pH but the concentration of the buffer during irradiation also affected the survival. The addition of osmotic stabilizers such as KCI, glycerol and polyethyleneglycol to the buffer increased the survival. The difference in singlet oxygen production in these reaction mixtures could not be related to these features. Furthermore, the survival was also dependent upon both irradiation temperature and cultivation temperature of the cells. These results with E. coli cells support the notion that one of the primary targets of toluidine blue sensitized photodynamic inactivation is cytoplasmic membrane, although other factors than cytoplasmic membrane also influence the survival of the cells.
ULTRAVIOLET INDUCED BINDING OF DAUNOMYCIN TO DNA
Authors: Gray P. J. , Phillips D. R. 
Published: January 2008

Abstract—Up to 10–15% of daunomycin present in solutions of DNA‐daunomycin remains irreversibly bound to DNA after 2 h of UV irradiation. Three times as much drug is irreversibly bound to DNA when oxygen is present, compared to deoxygenated solutions. Maximal amounts of the irreversibly bound drug are obtained between pH 5.5 and 7.5 and at an ionic strength of 0.76 M. Although the presence of daunomycin inhibits the extent of UV‐induced degradation of the DNA, the DNA is still extensively degraded and denatured in the time required for optimal yields of the DNA‐daunomycin photoproduct. This degradation of the DNA may impair its use as a lysosomotropic carrier of daunomycin.
DNA REPAIR IN V‐79 CELLS TREATED WITH COMBINATIONS OF PHYSICAL AND CHEMICAL CARCINOGENS*
Authors: Ahmed Farid E. , Setlow R. B. 
Published: January 2008

Abstract—Excision repair of DNA damage was measured by the photolysis of bromodeoxyuridine incorporated into parental DNA during repair in Chinese hamster V‐79 cells treated with 254 nm of ultraviolet radiation (UV), 7,12‐dimethylbenz[a]anthracene 5,6‐oxide (DMBA‐epoxide), N‐acetoxy‐2‐acetylaminofluorene (AAAF), 4‐nitroquinoline 1‐oxide (4NQO), 2‐methoxy‐6‐chloro‐9‐[3(ethyl‐2‐chloroethyl)‐aminopropylamino]acridine dihydrochloride (ICR‐170), X‐rays, ethylmethanesulfonate (EMS), methyl methanesulfonate (MMS) and combinations of these agents. Compared to normal human cells V‐79 were defective in repair of UV lesions and the lesions induced by the UV‐mimetic chemicals. The extent of the defects varied from 10 to 50% and was similar to those in Xeroderma pigmentosum group C cells (XP C). V‐79 cells repaired X‐ray damage and damage from the alkylating agents EMS and MMS to the same extent as human cells. Repair was additive after a combination of UV plus MMS indicating, as expected, that there are different rate‐limiting steps for removal of the damages from these agents. Repair was less than additive in cells treated with UV plus ICR‐170, AAAF plus ICR‐170, AAAF plus 4NQO, and 4NQO plus ICR‐170 and approximately equal to that observed for the higher of the two agents separately, indicating that there may be similar rate‐limiting steps for removal of lesions. Although the results on repair after combinations of UV plus 4NQO, UV plus DMBA‐epoxide or X‐rays plus MMS were difficult to interpret, there was not any inhibition of repair in these combinations.
ANALYSIS OF THE MECHANISM OF PHOTODYNAMIC INDUCTION OF SYNTHESIS OF A POLYPEPTIDE IN ARTHROBACTER SP.
Authors: Hoober J. Kenneth , Franzi Joseph 
Published: January 2008

Abstract—Synthesis of a 21000‐dalton polypeptide is greatly stimulated in a species of Arthrobacter by the combined influence of light, oxygen and a sensitizing dye. The dye must enter the cells for the effect to occur. The extent of photoinduction was not enhanced in the presence of D2O nor was it significantly inhibited by 10–20 mM azide or 1,4‐diazabicyclo [2.2.2]octane. The phenazine dye neutral red was nearly as effective as methylene blue and rose bengal in sensitizing photoinduction, although neutral red was inactive as a sensitizer of the photooxidation of histidine or methionine, singlet oxygen‐mediated reactions. Thus, generation of singlet oxygen does not seem to be a necessary step in the mechanism of induction. Neutral red had low activity as a sensitizer of the oxidation of sulfite, which proceeds by a radical mechanism. Considering also the known properties of phenazine compounds, the evidence supports the involvement of radical intermediates in the mechanism of photoinduction. Furthermore, the results suggest that the dyes must interact directly with an intracellular component, possibly DNA, for induction to occur.
CHARACTERIZATION OF THE RED LIGHT INDUCED REDUCTION OF A PARTICLE ASSOCIATED b‐TYPE CYTOCHROME FROM CORN IN THE PRESENCE OF METHYLENE BLUE*
Authors: Widell Susanne , Britz S. J. , Briggs W. R. 
Published: January 2008

Abstract—Methylene blue transfers electrons to a membrane‐associated b‐type cytochrome in particulate fractions from corn coleoptiles. The Km for methylene blue is less than 1 µM under optimal conditions. This reaction is destroyed by boiling, but not by 7 M urea. Kinetic analyses of the influence of light intensity on cytochrome reduction suggest that a first order photochemical reaction is limiting. Free EDTA may serve as an electron donor in this system at least at high methylene blue and protein concentrations. The photoactivity does not coincide either with mitochondrial or endoplasmic reticulum markers, and may be localized in plasma membrane. There is an estimated 5 times 10‐10 mol photoreducible cytochrome per g coleoptile tissue. Studies on the effect of pH on the reaction in the presence of methylene blue or thionine indicate that dye photoreduction itself is not rate‐limiting. Wavelength dependence studies suggest that it is methylene blue monomer and not dimer which mediates the reaction. Although oxygen is apparently required for the reaction, neither superoxide nor excited singlet oxygen appear to be involved. The reaction mechanism is still unknown.
PHOTOCHEMICAL REACTIONS OF THYMINE WITH CARBOXYLIC ACIDS. A MODEL FOR NUCLEIC ACID‐PROTEIN PHOTOCROSSLINKING
Authors: Toulme Francine , Hélène Claude 
Published: January 2008

Abstract—When nucleic acid bases are UV‐irradiated in the presence of carboxylic acids or carboxylate anions new photoproducts are formed as compared to the bases irradiated in the absence of carboxylic acids. The behavior of thymine and thymidine has been examined in detail. At least four photoproducts are formed in the presence of propionic acid and three in the presence of butyric acid. None of them appears to be a cyclobutyl dimer. From the concentration dependence of the rate of photoproduct formation it is concluded that the reactive excited species is the first excited singlet state of thymine. When 14C‐labelled thymine is irradiated in the presence of polyglutamic acid an important part of the radioactive material is covalently linked to the polymer. Photochemical reaction of thymine with glutamic (or aspartic) acid could thus induce crosslinks between proteins and nucleic acids. It is also shown that these photoproducts are stable under usual conditions of acidic hydrolysis of UV‐irradiated DNA.
PHOTOINITIATION OF ONE ELECTRON REACTIONS IN DIPEPTIDES AND PROTEINS CONTAINING TRYPTOPHAN AND TYROSINE
Authors: Sloper R. W. , Land E. J. 
Published: January 2008

Abstract—A radical transformation of the type Trṗ‐TyrOH → TrpH‐Tyr&#x004f;̇, previously observed by pulse radiolysis, has been detected following 265 nm laser excitation of oxygen saturated neutral aqueous solutions of TrpH‐TyrOH, TyrOH‐TrpH and cyclo‐TrpH‐TyrOH. A similar process was observed after photoexcitation of the proteins α‐lactalbumin and α‐chymotrypsin.
SENSITIZED TRIPLET FORMATION OF CHLOROPHYLL‐A AND ß‐CAROTENE
Authors: Jensen Niels‐Henrik , Wilbrandt Robert , Pagsberg Palle B. 
Published: January 2008

Abstract—The naphthalene‐sensitized formation of triplet excited chlorophyll‐a (Chl‐a) and all‐transß‐carotene has been studied by pulse radiolysis. The rate constants for transfer of triplet energy from naphthalene to Chl‐a and all‐transß‐carotene in benzene at 25°C are (3.6 ± 0.6)·109M‐1 s‐1 and (10.7 ± 1.2)·109M‐1 s‐1, respectively. The decays of the excited triplet states of naphthalene, Chl‐a and all‐transß‐carotene all follow a mixed first‐and second‐order mechanism. The first‐order rate constant for triplet decay is strongly dose dependent for naphthalene but only slightly dependent and independent of dose for Chl‐a and all‐transß‐carotene, respectively. The rate constants for triplet‐triplet annihilation are (1.4 ± 0.3)·109M‐1 s‐1 for Chl‐a and (3.6 ± 0.4)·109M‐1 s‐1 for all‐transß carotene. The nearly constant ratio k(ß‐carotene)/k(Chl‐a) for the bimolecular triplet energy transfer rate constants is discussed in terms of the molecular shapes of the two molecules. The energetics of the triplet‐triplet annihilation of all‐transß‐carotene are discussed, and it is proposed that production of the excited 1AB state may be a major route in the annihilation process.
THE PHOTOPHYSICS OF BONELLIN: A CHLORIN FOUND IN MARINE ANIMALS
Authors: Matthews J. Ioan , Braslavsky Silvia E. , Camilleri Patrick 
Published: January 2008

Abstract—The photophysical properties of bonellin, a free‐base chlorin, were studied in ethanolic solution. For the singlet excited state the following data were determined: an energy level, EBS= 187 ± 2kJ mol‐1, a lifetime, τf= 6.3± 0.1ns at 298 K, and fluorescence quantum yields, φr= 0.07 ± 0.02 (298 K) and 0.20 ± 0.04 (77 K). The S1→ T intersystem crossing quantum yield was φisc= 0.85 ± 0.1. No phosphorescence was observed at 298 K and 77 K. Based on quenching experiments the triplet state energy level was determined to be EBT= 180 ± 20 kJ mol‐1. A unimolecular decay rate constant, k1= (2.3 ± 0.5)· 103 s‐1 at room temperature, and a molar absorption coefficient, εT443= 9500 ± 500 M‐1 cm‐1, were obtained for the triplet state. This species was quenched by O2 with ko2= (1.7 ±0.3)· 108M‐1 s‐1, and by benzoquinone with kq= (5.2 ± 0.3)‐109M‐1 s‐1. The latter value, as well as the high value determined for the triplet annihilation rate constant, k2= (2 ± 0.5)· 109M‐1 s‐1, might reflect an electron transfer mechanism. Copper bonellin had a shorter triplet lifetime (>20 ns), which offers a possible explanation for its lack of photodynamic action.
PHOTOREVERSIBLE UV‐INACTIVATION OF MESSENGER RNA IN AN INSECT EMBRYO (SMITTIA SPEC., CHIRONOMIDAE, DIPTERA)
Authors: Jäckle Herbert , Kalthoff Klaus 
Published: January 2008

Abstract—Smittia embryos were UV‐irradiated during intravitelline cleavage. At this stage, nuclei are heavily shielded by yolk‐rich cytoplasm, and do not synthesize detectable amounts of RNA. Irradiation at 265, 285 and 295 nm wavelength caused biological inactivation, and pyrimidine dimer formation in maternal RNA as described earlier (Kalthoff, 1976; Jäckie and Kalthoff, 1978). In addition, we observed marked effects on protein synthesis: (1) The overall rate of [35S]‐methionine incorporation in vivo was reduced to less than half of the normal rate. (2) Two‐dimensional gel electrophoresis revealed quantitative variations in the synthetic rate of some polypeptides, and the appearance of new ones in UV‐irradiated embryos. (3) Translation of polyadenylated RNA from Smittia embryos in a cell‐free system was inhibited by UV irradiation in vivo. (4) The apparent degradation, during early embryogenesis, of maternal polyadenylated RNA was retarded in UV‐irradiated embryos.Exposure to light (400 nm) after UV caused partial photoreversal of all UV effects observed. Both the photoreactivable sector of UV‐inactivation, and the photoreactivated portion of UV inhibition of protein synthesis, were correlated with the amounts of pyrimidine dimers generated in maternal RNA by UV irradiation at the three wavelengths used. These correlated effects were produced most efficiently by 295 nm radiation, indicating the involvement of photosensitizing components in the embryos. Our data show, for the first time to our knowledge, that animal mRNA, after UV irradiation, can be photoreactivated in vivo. Moreover, our results strongly suggest that the photorepairable lesions consist of pyrimidine dimers generated in a photosensitized reaction.
THE EXPRESSION OF LIQUID HOLDING RECOVERY IN ULTRAVIOLET‐IRRADIATED ESCHERICHIA COLI REQUIRES A DEFICIENCY IN GROWTH MEDIUM‐DEPENDENT DNA REPAIR
Authors: Tang Moon‐Shong , Smith Kendric C. 
Published: January 2008

Abstract—Ultraviolet (UV) irradiated Escherichia coli K‐12 recA cells (but not rec+ cells) show enhanced survival if they are held in buffer prior to plating for viability. To understand the role of the recA mutation in this liquid holding recovery (LHR) phenomenon, we have studied LHR in a temperature sensitive recA 200 mutant. The detection of LHR requires that the irradiated cells be recA when they are plated on growth medium, but the recA deficiency plays no role during liquid holding (LH). We conclude that it is the extreme sensitivity of recA cells in growth medium to unrepaired DNA daughter‐strand gaps that magnifies the beneficial effects of the excision repair of DNA lesions during LH. Furthermore, we demonstrate a correlation between a strain's inability to perform growth medium dependent repair and its ability to express LHR. The relative amount of LHR was: recA > recF > lexA > recB > wild type (with the recB and wild‐type strains showing negative LHR). Two strains did not show this correlation; the uvrD strain showed less LHR than expected from its UV radiation sensitivity, while the polA strain showed more. The molecular bases for these exceptions are explored.
CONTROL BY PHYTOCHROME OF CHLOROPHYLL SYNTHESIS IN SEEDLINGS OF SORGHUM VULGARE
Authors: Sawhney S. , Oelze‐Karow H. , Sawhney N. , Mohr H. 
Published: January 2008

Abstract—The strong effect of light pretreatments on the synthesis of chlorophyll‐a and‐b in the shoot of Sorghum vulgare (kept under saturating white light) can be attributed to phytochrome only. No specific blue light effect was found. The phytochrome system appears to function perfectly normally under these conditions. Escape from reversibility is not detectable up to approximately 40 min after the onset of an inductive red light pulse. Thereafter, escape is fast, being completed at approximately 2.5 h after the inductive light pulse.
THE FLUORESCENCE DECAY OF REDUCED NICOTINAMIDES IN AQUEOUS SOLUTION AFTER EXCITATION WITH A UV‐MODE LOCKED Ar ION LASER
Authors: Visser A. J. W. G. , Hoek A. van 
Published: January 2008

Abstract— The fluorescence decay kinetics of the reduced nicotinamides NMNH, NADH and NADPH in aqueous solution were investigated using an Ar ion laser, mode locked in the UV, as source of excitation and single photon counting electronics in the detection system allowing for a time resolution in the picosecond range. Analysis of the experimental fluorescence decay showed that the dinucleotides did not follow a single exponential decay law. Good fitting was accomplished with a sum of two exponentials. The mononucleotide fluorescence decay was a single exponential for at least 95% of its amplitude.The heterogeneity in lifetimes of the fluorescence of the dinucleotides was interpreted in terms of an exciplex mechanism.
INCORPORATION OF 11,12‐DIHYDRORETINAL INTO THE RETINAE OF VITAMIN A DEPRIVED RATS
Authors: Crouch Rosalie , Katz Sidney , Nakanishi Koji , Gawinowicz M. A. , Balogh‐Nair Valeria 
Published: January 2008

Abstract— The incorporation of 11,12‐[15–3H]‐dihydroretinal, a retinal in which the crucial 11‐ene is saturated, into the retinae of vitamin A deficient rats as a result of intraperitoneal injection of the corresponding alcohol was shown by the presence of the tritium label in the rod outer segments and by identification of the extracted retinals using high pressure liquid chromatography. The amplitude of the electroretinogram (ERG) b‐wave, diminished as the result of vitamin A deprivation, was not affected by administration of the analogue, although similar treatment of deprived litter mates with trans retinal restored the ERG b‐wave amplitude to a normal level.The evidence that the analogue is bound to opsin forming 11,12‐dihydrorhodopsin is as follows: (1) when incubated with 11‐cis retinal, extracts from vitamin A deficient rats regenerate 1.4 nmol rhodopsin while extracts from rats deficient in vitamin A and supplemented with 11,12‐dihydroretinal regenerate 0.6 nmol rhodopsin indicating binding of the dihydroretinal blocks rhodopsin regeneration. (2) 11,12‐dihydroretinal is shown to remain unchanged in hexane‐washed retinae after extraction with methylene chloride and (3) injection of retinal into animals previously injected with 11,12‐dihydroretinal also fails to restore visual sensitivity as measured by the ERG b‐wave. Our results indicate that the dihydro‐chromophore occupies the same binding site as the natural 11‐cis retinal and that occupation of the chromophore binding site of opsin is not sufficient to restore the visual sensitivity in a vitamin‐A‐deprived animal.
Book Reviews
Authors: Zuclich Joseph A. , Harrison Joseph M. , Duráan Nelson 
Published: January 2008

Book reviewed in this article: The Effects of Constant Light on Visual Processes. Edited by T. P. Williams and B. N. Baker. Plenum Press, New York, 1980. 455 pp. $45.00. Radiation Biology and Chemistry: Research Developments. Edited by H. E. Edwards, S. Navaratnam, B. J. Parsons and G. O. Phillips. Elsevier Scientific, Amsterdam, 1979. 505 pp. $78.00
INACTIVATION OF NORMAL AND MUTANT NEUROSPORA CRASSA CONIDIA BY VISIBLE LIGHT AND NEAR‐UV: ROLE OF 1O2, CAROTENOID COMPOSITION AND SENSITIZER LOCATION
Authors: Thomas Sharon A. , Sargent M. L. , Tuveson R. W. 
Published: January 2008

Abstract— Inactivation of Neurospora crassa conidia from wild‐type and mutant strains by visible and near‐UV light has been investigated in the presence and absence of photosensitizing dyes. Inactivation by near‐UV is virtually unchanged by the presence of deuterium oxide or azide suggesting that, contrary to the situation with visible light and photosensitizing dyes, 1O2 is not involved in any substantial way in the formation of lethal lesions. The finding that carotenoid deficient strains are similar to wild‐type strains in sensitivity to near‐UV inactivation is consistent with 1O2 not being involved.Photodynamic inactivation of conidia by visible light occurs in the presence of methylene blue (MB), toluidine blue O (TB), or acridine orange (AO). Carotenoid deficient strains are more sensitive to such inactivation only when MB and TB are used. These results support the contention that MB and TB mediated damage involves the cell membrane where carotenoids are available for quenching, whereas AO mediated damage occurs in the nucleus sequestered from the protective influence of carotenoids.A newly isolated, lemon–yellow mutant, mapping to the al‐1 locus, exhibits sensitivities to photodynamic inactivation similar to other pure‐white mutants at the same locus. The sensitivity of this pigmented mutant is apparently related to insufficient unsaturation (seven to nine double bonds) of the two colored carotenoids, zeta–carotene and neurosporene, produced by the mutant.
LUMINESCENCE STUDIES ON FORMYCIN, ITS AGLYCONE, AND THEIR N‐METHYL DERIVATIVES: TAUTOMERISM, SITES OF PROTONATION AND PHOTOTAUTOMERISM
Authors: Wierzchowski Jacek , Shugar David 
Published: January 2008

Abstract— A detailed study has been made of the luminescence spectra of 3‐β‐d‐ribofuranosyl‐7‐amino‐pyrazolo(4,3‐d)pyrimidine (formycin A), 3‐propyl‐7‐aminopyrazolo(4,3‐d)pyrimidine (7APP), and their various N‐methyl derivatives, at room temperature and in methanol‐water glasses at 77 K. Comparisons of the foregoing, together with the observed dependence of the emission spectra of formycin and 7APP on excitation wavelength, demonstrated that these consist of two tautomeric species, N(1)H and N(2)H, both of which emit at 300 and 77 K. The two tautomers may be distinguished by the location of the emission maxima, especially for phosphorescence, and quantum yields for emission.Comparisons of the emission spectra of the protonated forms of 7APP and its N‐methyl derivatives showed that the fluorescence of the cations of 7APP and its N,‐ and N2‐methyl derivatives originates from the forms protonated on N(4). By contrast, the forms protonated on N(6) contribute appreciably to the phosphorescence at 77 K. On the basis of the emission spectra at 77 K, it is concluded that the major tautomeric form of the formycin cation is N(1)H,N(4)H+, but there is also some contribution by the form N(2)H,N(4)H+.In acid medium at room temperature, there is photodissociation of a proton from the pyrazole ring of the formycin cation. This leads to formation in the state S! of the tautomeric species N(4)H, which does not exist in the ground state. This conclusion, similar to that previously reported for the analogous isomeric 4‐aminopyrazolo(3,4‐d)pyrimidines, is derived from a comparison of the fluorescence spectra of the cations of formycin and N4‐methylformycin, which exhibit two bands at 375 and 440 nm, the latter corresponding to the emission of the neutral form of N,i‐methylformycin. The proposed mechanism of phototautomerization is supported by a study of solvent and salt effects.
PIGMENT ORGANIZATION IN THE LIGHT‐HARVESTING CHLOROPHYLL‐a/b PROTEIN COMPLEX OF LETTUCE CHLOROPLASTS. EVIDENCE OBTAINED FROM PROTECTION OF THE CHLOROPHYLLS AGAINST PROTON ATTACK and FROM EXCITATION ENERGY TRANSFER
Authors: Siefermann‐Harms Dorothea , Ninnemann Helga 
Published: January 2008

Abstract—The light‐harvesting Chl‐a/b protein complex (LHC) ofLactuca sativaL. was examined for pigment content, excitation energy transfer and behavior under acidic conditions:(1) Lettuce LHC contains Chl‐a, Chl‐b and xanthophylls (lutein, neoxanthin, lactucaxanthin, viola‐xanthin) at a molar ratio of 6:4:3; their contribution to the absorbance of the LHC between 390 and 530 nm is estimated to be about 31% (Chl‐a), 26% (Chl‐h) and 43% (xanthophylls).(2) Energy transfer from xanthophylls and Chl‐fe to Chl‐a takes place at 100% transfer efficiency.(3) LHC exhibits an unusual acid stability: in contrast to complexes of photosystem I or II, LHC‐bound chlorophylls are not converted to phaeophytin and LHC apoprotein is not denatured at pH 1.5; also, energy transfer is maintained.(4) Pronase or trypsin treatment do not affect acid stability and energy transfer.(5) Treatments that break down acid stability (heat, urea or TritonX–100) also inhibit energy transfer.The coincidental breakdown of energy transfer and acid stability points at one underlying process, namely, the breakdown of a structure that enables protection of chlorophylls from proton attack and close contiguity of xanthophylls and chlorophylls as required for energy transfer. Dense packing of xanthophylls and chlorophylls within lipophilic crevices of the LHC is suggested.