bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOTOCHEMICAL ADDITION OF GLUTATHIONE TO URACIL AND THYMINE
Authors: Varghese A. J.
Published: January 2008

Abstract—Irradiation (Λ > 240 nm) of thymine in aqueous solution in the presence of glutathione produces primarily 5‐S‐glutathione‐5, 6‐dihydropyrimidine and 5‐S, S‐glutathione‐5, 6‐dihydro‐pyrimidine. These adducts are obtained in better yields when the irradiations (Λ > 280 nm) are carried out in the presence of triplet‐state sensitizers. Reduction of 5‐S, S‐glutathione‐5, 6‐dihydropyrimidine with zinc dust in acetic acid yields the corresponding 5, 6‐dihydropyrimidine. When thymine‐glutathione adducts are heated in 6 N HCl for 2h, 5‐S‐cysteine‐5, 6‐dihydrothymine and 5‐S, S‐cysteine‐5, 6‐dihydrothymine are formed. Under these conditions, uracil‐glutathione adducts are less stable and are converted to products other than uracil‐cysteine adducts.
PHOTOCYCLOADDITION OF ACETONE TO URACIL AND CYTOSINE
Authors: Varghese A. J.
Published: January 2008

Abstract— Ultraviolet irradiation (Λ > 280 nm) of uracil in aqueous acetone (1:1) produces cyclobutane uracil dimer and uracil‐acetone addition product. The addition product is identified as an oxetane. The same product is also obtained from cytosine irradiated under the same conditions. The cytosine‐acetone oxetane apparently undergoes deamination readily. Irradiation (Λ= 265 nm) of the oxetane in aqueous solution produces acetone and uracil with a quantum efficiency of 0–16.
LIGHT‐INDUCED FREE RADICALS IN ORIENTED DNA‐PROFLAVINE COMPLEXES
Authors: Gräslund A. , Rupprecht A. , Ström G.
Published: January 2008

Abstract— Oriented wet DNA‐proflavine complexes were illuminated with visible light, Λ > 395 nm, at 77 K, in the presence or absence of oxygen. The electron paramagnetic resonance spectra at 77 K and low microwave power (3 μ W) indicated formation of anionic free radicals in thymine and cationic free radicals, probably in guanine, identical to those induced by y rays at 77 K in similar samples of pure DNA.

The free‐radical formation rate showed a quadratic dependence on light intensity, indicating a biphotonic mechanism. The proflavine triplet spectrum was observed during illumination. If the exciting light includes wavelengths below 390 nm, significant amounts of hydrogen addition radicals in thymine are found.
PROPERTIES OF THE ULTRAVIOLET‐LIGHT‐MEDIATED BINDING OF BOVINE SERUM ALBUMIN TO DNA*
Authors: Braun Andrew , Merrick Bruce
Published: January 2008

Abstract— The binding of DNA to protein mediated by U V (254 nm) radiation has been investigated using binding of the complex to Millipore membrane filters as an assay technique. The reaction proceeds through an activated protein intermediate which then reacts with the DNA. The activated protein has a half‐life of about 75 min at 0°C and about 18 min at 37°C. Short wavelengths are more efficient in forming the complex than wavelengths in the 250–280 nm range. N‐ethyl maleimide treatment of protein before irradiation markedly inhibits the reaction.
PHOTOTACTIC RESPONSE OF CHLAMYDOMON AS TO FLASHES OF LIGHT‐I. RESPONSE OF CELL POPULATIONS
Authors: Feinleib Mary Ella
Published: January 2008

Abstract— Chlamydomonas reinhardi responds phototactically to a single, very short flash of blue light (6‐4 μs). Net oriented response of a cell population is monitored photometrically, using the “population system” of Feinleib and Curry (1967). A single high‐intensity flash elicits a small, but definite net movement away from the stimulus source. Repetitive flashing at low frequency (between 8 and 60 flashes per min) and at the same intensity elicits a prolonged response in the same direction. Net phototactic response to single or repetitive flashes varies with stimulus intensity in the same way as does response to continuous light (Feinleib and Curry, 1971b); response is positive at low intensity and negative at high intensity. These data indicate that at least some cells become oriented in response to a short flash. The occurrence of such a response has implications for the mechanism of phototactic orientation. If almost all the cells responded, one would assume that Chlamydomonas perceives light direction instantaneously by detecting an absorption gradient within the cell. Unequivocal interpretation of the short‐flash response requires examination of the behavior of individual cells.
INTERMEDIATES IN THE PHOTOLYSIS OF INDOLE: ROOM TEMPERATURE AQUEOUS SOLUTIONS AND LOW TEMPERATURE GLASSES
Authors: Arce R. , Grimison A. , Revuelta J. , Simpson G. A.
Published: January 2008

Abstract— Flash photolysis of indole aqueous solutions produces four transients with absorption maxima, in their order of appearance in time, at 720, 370, 380 and 520 nm. These correlate with low temperature photolysis observations. The results are interpreted in terms of electron‐radical cation generation and subsequent production of the indolyl radical.
THE PHOTOLABILITY OF DNA CONTAINING 5‐BROMOURACIL‐I. SINGLE‐STRAND BREAKS AND ALKALI‐LABILE BONDS*
Authors: Hewitt Roger R. , Marburger Kathleen
Published: January 2008

Abstract— The proportions of single‐strand breaks and alkali‐labile bonds produced by UV‐light were investigated in covalently‐closed circular 5‐bromouracil (BrUra)‐containing λ‐phage DNA. When BrUra DNA was irradiated in 001 M Tris‐0–001 M EDTA (pH 8‐1) buffer, the D0 was 11‐7 J/m2 for single‐strand breaks, 2–25 J/m2 for total breaks, and 2–8 J/m2 for alkali‐labile bonds. Thus, alkali‐labile bonds were the predominant photochemical products. No double‐strand breaks were observed after exposure to 7‐7 times the D0 for neutral breakage. The photolability measured under both neutral and alkaline conditions was affected by the NaCl concentration in the irradiation solvent, with the greatest resistance to breakage exhibited at the lowest concentrations. The composition of the irradiation buffer also affected sensitivity. Exposure in 1/10 SSC yielded 4‐4 (neutral) and 5–7 (alkaline) times the breakage produced in Tris‐EDTA.
WAVELENGTH DEPENDENCE OF THE INTERSYSTEM CROSSING EFFICIENCY FOR RETINAL ISOMERS
Authors: Bensasson R. , Land E. J. , Truscott T. G.
Published: January 2008

Abstract— The quantum efficiencies of intersystem crossing (P̈ISC) fur four isomers of retinal, the all‐trans, 9‐cis, 11‐cis and 13‐cis, have been measured using both 265 nm and 353 nm excitation. The values for the all‐trans and 9‐cis isomers are independent of the excitation wavelength but the values for the 11‐cis and 13‐cis isomers show a marked increase in the efficiency of ISC for 353 nm excitation compared with the 265 nm excitation.
LIGHT PRODUCTION IN ALKALINE MIXTURES OF REDUCING AGENTS AND DIMETHYLBIACRIDYLIUM NITRATE*
Authors: Totter John R.
Published: January 2008

Abstract— Kinetic studies were made of light production and 02 absorption elicited by treatment of dimethylbiacridylium hydroxide [D(OH)2] with reducing agents in alkaline aqueous solutions. D(OH)2 addition stimulated O2 uptake which proceeded with zero‐order kinetics until nearly all of the O2 or of the D(OH)2 was converted to end products. At the termination of the reactions with fructose as reductant the D(OH)2 was converted to methylacridone and to dimethylbiacridene each compound accounting for approximately one‐half the D(OH)2 consumed. O2 was reduced to H2O2. With hydroxylamine as the reducing agent the emitted light intensity was related to the first power of the D(OH)2 concentration and the rate of O2 uptake to the square root of the D(OH)2. The disappearance of D(OH)2 in these circumstances was by a first order or pseudo‐first order rate. Fructose as a reducing agent by contrast resulted in an O2 uptake nearly independent of D(OH)2 concentration over a range from 1 × 10‐5M‐1 × 10‐4M, while the light intensity and disappearance of D(OH)2 followed a one‐half order rate. O2 uptake was by zero order kinetics and the oxidation of fructose proceeded at the same rate as was found with ferricyanide as oxidant. The kinetics, quantum yields and temperature dependence of the fructose reactions were compared with similar reactions employing H2O2 as the light eliciting reagent. The results are interpreted as indicating that D(OH)2 acts as a chain initiator in a manner analogous to better known, radical producing compounds found to accelerate hydrocarbon autooxidations.
THE IN VIVO ASSOCIATION OF MANGANESE WITH THE CHROMOSOME OF MICROCOCCUS RADIODURANS
Authors: Lebowitz P. J. , Schwartzberg L. S. , Bruce A. K.
Published: January 2008

Abstract—Extremely high levels of paramagnetic manganese (Mn2+) which quench phosphorescent reactions have been found to inhibit the formation of thymine‐containing dimers in M. radiodurans. Lowering the concentration of Mn2+ in the culture medium resulted in a lower intracellular concentration of Mn2+, an increase in the UV‐sensitivity of this bacterium, and a larger photochemical yield of thymine‐containing dimers. High levels of paramagnetic Mn2+ were not found in other test organisms which are more sensitive to UV‐irradiation. One interpretation of our data is that in Micrococcus radiodurans Mn2+ may bind to the chromosome and thereby reduce the photochemical yield of thymine‐containing dimers.
FLASH PHOTOLYSIS OF AQUEOUS TRYPTOPHAN, ALANYL TRYPTOPHAN AND TRYPTOPHYL ALANINE
Authors: Templer H. , Thistlethwaite P. J.
Published: January 2008

Abstract— Tryptophan has been flash photolysed in deoxygenated and air equilibrated solutions. The kinetics of the subsequent reactions of the tryptophyl radical and the hydrated electron have been elucidated. Oxygen has been found to reduce the primary photoionization yield, indicating a triplet state precursor, but no evidence has been found for a biphotonic process. Appreciable differences in the photoionization quantum yields have been found for tryptophan, alanyl tryptophan and tryptophyl alanine.
DIFFERENTIAL EFFECTS OF NEAR‐UV AND VISIBLE LIGHT ON ACTIVE TRANSPORT AND OTHER MEMBRANE PROCESSES IN ESCHERICHIA COLI*
Authors: Sprott G. D. , Martin W. G. , Schneider Henry
Published: January 2008

Abstract— The effects of monochromatic near‐UV and visible light on active transport and several other membrane processes in Escherichia coli were investigated. Using mercury lines at 366, 405, 435, 546 and 578 nm, large differential effects were observed. Transport systems with photosensitive initial rates of uptake were classified into three groups on the basis Of wavelength dependence. Three, and possibly four photosensitizers may be involved; three active under aerobic conditions and the fourth in the absence of oxygen. Respiration rate exhibited the same sensitivity as one of the groups, suggesting that the active uptake of member amino acids (e.g. glycine) is largely dependent on oxidative energy. The photosensitivity of glycine transport at 405 nm was not the result of inhibition of the membrane‐bound Ca–Mg adenosine triphosphatase as shown using an isogenic mutant strain. Cell viability was not affected at the highly active wavelength, 405 nm. Photoeffects on transport of α‐methylglucoside were minimal at 366 and 405 nm, contrasting to most of the amino acids investigated. The relative photosensitivity of respiration and several amino acid transport systems depended on carbon source.
STOCHASTIC MODELING OF LIGHT ENERGY CONVERSION IN PHOTOSYNTHESIS
Authors: Ross Robert T. , Anderson Roland J. , Hsiao Ta‐Lee
Published: January 2008

Abstract— Photosynthetic quantum conversion and early electron transport is modeled as a stochastic process on a digital computer to determine what free‐energy losses are a necessary consequence of specific assumptions about the reaction structure, kinetics, and thermodynamics of the participating molecules. Maximal free‐energy yield requires that all dark reactions be near equilibrium, so the potentials of all half‐cells on each side of the light act are nearly the same. This near equilibrium requires that all forward rate constants be at least 102 times the rate of light absorption, and that all reverse rate constants be at least the rate of light absorption. The behavior of model systems with one primary donor and one primary acceptor is comparatively independent whether there is one or an infinite number of secondary electron donors and acceptors. A system having no metastable (e.g. triplet) state of the light‐activated donor can convert light energy with nearly ideal efficiency, provided that the standard electrode potentials of the primary donor and primary acceptor half‐cells are precisely located with respect to one another and to the potentials of the ultimate donor and acceptor. While not necessary for near maximal free‐energy yield, a metastable intermediate allows a flexibility in the choice of half‐cell potentials which is not possible in the absence of such an intermediate.
ACTION SPECTRA FOR LETHALITY IN RECOMBINATION‐LESS STRAINS OF SALMONELLA TYPHIMURIUM AND ESCHERICHIA COLI*
Authors: Mackay Donna , Eisenstark A. , Webb R. B. , Brown M. S.
Published: January 2008

Abstract— Action spectra for lethality of both stationary and exponentially growing cells of recombinationless (recA) mutants of Salmonella typhimurium and Escherichia coli were obtained. Maximum sensitivity was observed at 260nm which corresponds to the maximum absorbance of DNA. However, a shoulder occurred in the 280–300 nm range that departed significantly from the absorption spectrum of DNA. At wavelengths longer than 320nm, the shapes of inactivation curves departed significantly from those at wavelengths shorter than 320nm and survival curves at wavelengths longer than 320nm had a large shoulder. A small peak or shoulder occurred in the 330–340nm region of the action spectra. The special sensitivity of recA mutants to broad spectrum near‐UV radiation may be due to synergistic effects of different wavelengths. Parallels between the inactivation of recA mutants and the induction of a photoproduct of l‐tryptophan toxic for recA mutants (now known to be H2O2) suggest that H2O2 photoproduct from endogenous tryptophan may be involved in the high sensitivity of these strains to broad spectrum near‐UV radiation.
SYNERGISTIC LETHAL ACTION OF ULTRAVIOLET‐VIOLET RADIATIONS AND MILD HEAT IN ESCHERICHIA COLI
Authors: Tyrrell Rex M.
Published: January 2008

Abstract— The lethal interaction of far ultraviolet (254nm), near ultraviolet (334 and 365nm) and violet visible (405nm) radiation treatment with mild heat treatment was studied. Except at 254nm, a strong positive radiation dose‐dependent interaction (synergism) was always observed. The efficiency of sensitisation to heat, as a function of dose at each wavelength, was found to be directly correlated with the dose necessary to eliminate the shoulder from the survival curve of a repair proficient strain but was apparently unrelated to the relative near‐ultraviolet sensitivities of a repair deficient strain. The interaction was independent of the order of treatments. A radiation dose of 106 Jm‐2 at 365nm slightly sensitised a cell population to 45°C incubation (normally non‐lethal) and strongly sensitised the cells to 48°C treatment (normally 80 percent survival after 2 hours). It is proposed that in addition to DNA damage, both heat treatment and near ultraviolet treatment interfere with DNA recovery mechanisms so that the combination of the two agents inevitably leads to a strong positive interaction.
THE PHOTOREDUCTION OF METHYLENE BLUE BY AMINES—II. AN INVESTIGATION OF THE DECAY OF SEMIREDUCED METHYLENE BLUE
Authors: Kayser R. H. , Young R. H.
Published: January 2008

Abstract— The decay of semireduced methylene blue (MB') formed in the photoreduction of the dye by aryl‐ and alkylamines was examined by flash photolysis. The second order decay of MB in methanol produced using arylamines and 1,4‐diazabicyclooctane as photoreducing agents led to complete regeneration of the dye and amine. The rate constants for a series of N.N‐dimethylanilines showed a small substituent effect (p= 0.69 ± 0.16) compatible with recombination of MB' with arylamine derived radical cations. A study of the solvent effect on the recombination process revealed the importance of the stability of the radical cation toward the solvent and also indicated that the reaction approaches the rate of diffusion. The photoreduction of the dye by most alkylamines examined resulted in permanent bleaching of methylene blue. The second order decay of MB' produced using tertiary aliphatic amines led exclusively to formation of the leuco‐dye with no apparent regeneration of methylene blue; this process was tentatively assigned to a reaction of MB' with α‐amino radicals formed from the amine radical cation. It was concluded that the methylene blue‐sensitized photooxidation of amines involves a Type I process and possible mechanisms are discussed.
PHOTODYNAMIC TREATMENT OF HERPES SIMPLEX VIRUS INFECTION IN VITRO
Authors: Lytle C. David , Hester Lynda D.
Published: January 2008

Abstract— The effects of photodynamic action on in vitro herpes simplex virus infections of CV‐1 monkey kidney fibroblasts or human skin fibroblasts were determined using proflavine sulfate and white fluorescent lamps. Photodynamic treatment of confluent cell monolayers prior to virus infection inactivated cell capacity, i.e. the capacity of the treated cells to support subsequent virus growth as measured by plaque formation. The capacity of human cells was more sensitive to inactivation than the capacity of monkey cells when 6 μM proflavine was used. Treated cell monolayers recovered the capacity to support virus plaque formation when virus infection was delayed four days after the treatment. Experiments in which the photodynamically treated monolayers were infected with UV‐irradiated virus demonstrated that this treatment induced Weigle reactivation in both types of cells. This reactivation occurred for virus infection just after treatment or 4 days later. A Luria‐Latarjet‐type experiment was also performed in which cultures infected with unirradiated virus were photodynamically treated at different times after the start of infection. The results showed that for the first several hours of the virus infection the infected cultures were more sensitive to inactivation by photodynamic treatment than cell capacity. By the end of the eclipse period the infected cultures were less sensitive to inactivation than cell capacity. Results from extracellular inactivation of virus grown in monkey cells at 6 μM proflavine indicated that at physiological pH the virus has a sensitivity to photodynamic inactivation similar to that for inactivation of cell capacity. The combined data indicated that photodynamic treatment of the cell before or after virus infection could prevent virus growth. Thus, photodynamic inactivation of infected and uninfected cells may be as important as inactivation of virus particles when considering possible mechanisms in clinical photodynamic therapy for herpes simplex.
PROTECTION OF ESCHERICHIA COLI CELLS AGAINST THE LETHAL EFFECTS OF ULTRAVIOLET AND X IRRADIATION BY PRIOR X IRRADIATION: A GENETIC AND PHYSIOLOGICAL STUDY
Authors: Smith Kendric C. , Martignoni Klaus D.
Published: January 2008

Abstract— When log phase cells of wild‐type E. coli K‐12 were maintained in growth medium after X irradiation, they became progressively more resistant to a subsequent exposure to UV or X radiation. The time to achieve maximum resistance was about 60 min. The uvrB, uvrD, polA and certain exrA strains (W3110 background) also demonstrated this X ray‐induced resistance to subsequent UV or X irradiation but recA, recB, lex (AB1157 or W3110 backgrounds) and other exrA strains (AB1157 background) did not. The resistance induced in wild‐type, uvrB and uvrD cells was characterized by the production or enhancement of a shoulder on the survival curves obtained for the second irradiation, while the resistance induced in the W3110 exrA strains was expressed only as a change in slope. The induction of resistance in the W3110 exrA strain was not inhibited by the presence of chloramphenicol, but that in the wild‐type cells appeared to be. The production or enhancement of a shoulder on the survival curves of the rec+lex+exr+ cells is consistent with the concept of the radiation induction of repair enzymes. Alternative explanations, however, are discussed.
INDICATION OF FAST TRIPLET FORMATION IN BIMOLECULAR QUENCHING OF EXCITED SINGLET STATES STUDIED BY CONVENTIONAL FLASH PHOTOLYSIS
Authors: Vogelmann Ekehardt , Kramer Horst E. A.
Published: January 2008

The bimolecular quenching of the first excited singlet state of oxonine by allylthiourea leads to the formation of the triplet state of the dye. This has been proved by comparison with the triplet‐triplet absorption spectrum of oxonine obtained by triplet‐triplet energy transfer. The conventional flash experiments suggest that the dye triplet state is produced directly rather than by radical recombination.
EXTRARETINAL PHOTORECEFTION IN INSECTS
Authors: Truman James W.
Published: January 2008

Abstract— Extraretinal photoreceptors are widespread among insects and function in the photoperiodic control of development and in the entrainment of circadian rhythms. The effects of light on the daily and seasonal regulation of brain neuroendocrine activity are mediated solely through extraretinal photoreceptors. In primitive insects, the eyes participate in the entrainment of nonendocrine circadian rhythms such as the locomotor rhythm. In more advanced forms, however, extraretinal pathways appear to be the only pathway for the entrainment of all rhythms thus far examined. But even in this latter case, the eyes sometimes effect a masking of the expression of the overt rhythm. An exact localization of the extraretinal receptors has not been accomplished, but in all studies to date they appear to be associated with the cerebral lobe region of the brain. Action spectra for photoperiodic responses have been determined for a number of insects. In general the responses are maximally sensitive in the blue with a marked decline in the red although exceptions do exist. Complete action spectra for circadian responses have been determined only for two insects. In both cases a plateau of sensitivity extends through the blue with a steep drop at longer wavelengths. From the action spectra data, the extraretinal receptors appear to have a threshold sensitivity less than 3 times 10‐2 J/m2. The pigment nature of the receptor is unknown although it appears not to be a carotenoid derivative.
EXTRAOCULAR PHOTORECEPTION IN AMPHIBIANS
Authors: Adler Kraig
Published: January 2008

Abstract— Amphibians possess extraocular photoreceptors (EOPs) which exclusively or together with the lateral eyes perceive light for various physiological and behavioral activities. Several kinds of EOPs are discussed but emphasis is given to the pineal complex: the dermal frontal organ (or stirnorgan) found only in frogs and toads among amphibians and the intracranial pineal body (or epiphysis cerebri) found in all Amphibia. Both structures are derived as dorsal evaginations of the diencephalon and have a retina‐like fine structure. Both are sensitive to visible and UV light but not to IR, mechanical or chemical stimuli. The frontal organ gives chromatic and achromatic responses but in most species only achromatic ones are recorded from the pineal. Photopigments have been identified for some of these responses.

Pineal EOPs are involved in several activities: (i) neurosecretory activity by the subcommissural organ in the brain; (ii) body‐lightening reaction in larval amphibians, involving the light‐inhibited release by the pineal of a hormone, presumably melatonin, which contracts melanophores in the skin; (iii) cuing of circadian locomotor rhythms, including phase shifts and synchronization with environmental light cycles; (iv) perception of celestial cues for use in time‐compensated compass orientation; and (v) possibly perception of linearly‐polarized light.

Non‐pineal EOPs have been implicated in (i) tail‐darkening reaction of frog larvae where light has a direct effect on melanophores; and (ii) in phototaxis where unknown EOPs in various parts of the body and tail mediate withdrawal from light. Evidence for use of pineal and non‐pineal EOPs and location of specific receptors is reviewed drawn from biochemical, ultrastructural, neurophysiological and behavioral studies. The possible use of EOPs for other biological functions and their possible adaptive value are briefly discussed.
HOST CELL REACTIVATION IN MAMMALIAN CELLS‐V. PHOTOREACTIVATION STUDIES WITH HERPES VIRUS IN MARSUPIAL AND HUMAN CELLS
Authors: Lytle C. D. , Benane S. G. , Stafford J. E.
Published: January 2008

Abstract— The survival of UV‐irradiated herpes simplex virus was determined in cultured Potoroo (a marsupial) and human cells under lighting conditions which promote photoreactivation. Photoreactivation was readily demonstrated for herpes virus in two lines of Potoroo cells with dose reduction factors of 0.7‐0.8 for ovan cells and 0.5‐0.7 for kidney cells. Light from Blacklite (near UV) lamps was more effective than from Daylight (mostly visible) lamps, suggesting that near UV radiation was more efficient for photoreactivation in Potoroo cells. The quantitative and qualitative aspects of this photoreactivation were similar to those reported for a similar virus infecting chick embryo cells. UV‐survhal curves for herpes virus in Potoroo cells indicated a high level of “dark” host cell reactivation. No photoreactivation was found for UV‐irradiated vaccinia virus in Potoroo cells. A similar photoreactivation study was done using special control lighting (Λ > 600 nm) and human cells with normal repair and with ceils deficient in excision repair (XP). No photoreactivation was found for UV‐irradiated herpes virus in either human cell with either Blacklite or Daylight lamps as the sources of photoreacti‐vating light. This result contrasts with a report of photoreactivation for a herpes virus in the same XP cells using incandescent lamps.
THE SUBSTRATE‐DEPENDENT PHOTOINACTIVATION OF UROCANASE FROM RAT LIVER
Authors: Hug Daniel H. , Hunter John K. , O'Donnell Peter S.
Published: January 2008

Abstract— Rat liver urocanase was readily inactivated by near‐UV light in the presence of the substrate. Irradiation of substrate or enzyme alone was ineffective. The purpose of this study was to examine the conditions which influenced this inactivation and to investigate the mechanism. The urocanate concentration needed for 50% of the maximum inactivation for a 15 min irradiation was 0.09 μM. Temperatures from 0 to 30°C during irradiation had little influence. Inactivation occurred at ‐75°C, which indicated a photochemical reaction. The pH had little influence on inactivation. Photoinactivation was the same in nitrogen and air. Dialysis experiments showed that unbound small molecules were probably not involved. Inactivated enzyme did not inhibit active enzyme. Chelators, reducing agents, and pyridoxal phosphate did not affect the inactivation. Visible light was not effective. An action spectrum was established with the aid of a monochromator. The action spectrum had a peak at 280 nm and a shoulder extending from 300 to 340 nm which rules out flavins. pyridoxal phosphate, a simple protein, and free urocanate as the chromophore. The results suggest that this photochemical process is not photodynamic action. It appears that only substrate and enzyme are needed for this photoinactivation. The enzyme‐substrate complex may be the chromophore.
WHAT DOES THE TERM “VIBRONIC COUPLING” MEAN?
Authors: Azumi Tohru , Matsuzaki Kazuo
Published: January 2008

Abstract— The term usually referred to as vibronic coupling is discussed. Various adiabatic approximations are exactly defined in an effort to remove the existing ambiguities. The various approaches for improving approximate wavefunctions to obtain more exact wavefunctions are discussed. Transition dipole moments between two vibronic states are evaluated by the different methods, and the mutual relationship among the methods is discussed.
5,5′‐DIURIDINYL, A MAJOR PHOTOPRODUCT FROM UV‐IRRADIATION OF POLYNUCLEOTIDES CONTAINING BROMOURACIL
Authors: Sasson S. , Wang S. Y. , Ehrlich M.
Published: January 2008

Abstract— The major photoproduct from UV‐irradiation of polynucleotides containing bromouracil has been identified as 5,5′‐diuridinyl by comparing Rf values and UV and fluorescence spectra with a synthetic compound.
HEMOLYSIS OF HUMAN ERYTHROCYTES BY ACTIVATED OXYGEN SPECIES
Authors: Michelson A. M. , Durosay P.
Published: January 2008

Abstract— The hemolysis of human erythrocytes by irradiation at 254 nm has been studied. Neither superoxide radicals nor singlet oxygen play a significant rôle and it is likely that the major species involved are hydroxyl radicals and, indirectly, carbonate anion or formate radicals. Similarly, when erythrocytes are treated with a system commonly used as source of superoxide radicals (photoreduction of riboflavin) it has been demonstrated that O‐2 does not participate in lysis, but that singlet oxygen (possibly with hydroxyl radicals) is a major oxygen species involved in destruction of the cell membrane.
PHOTOCHEMISTRY OF 5‐BROMOURIDINE AND 5‐BROMO‐2‘‐DEOXYURIDINE IN ICE AND IN “PUDDLES”*
Authors: Sasson S. , Wang S. Y.
Published: January 2008

Abstract. 5,5‘‐Diuridinyl and 5,5’‐dideoxyuridinyl have been isolated from UV irradiation (254nm) in a frozen state of 5‐bromouridine and 5‐bromodeoxyuridine, respectively. These compounds were characterized by UV, IR, NMR, and mass spectra. They are formed in relatively high quantum yields which are comparable to thymidine dimerization and were found to be unaffected upon further irradiation. This photostability suggests that these 5,5‘‐coupled products, if formed, may accumulate in biological systems. Experiments carried out in “puddles” indicate, by negative inference, that the main reaction pathway is probably the recombination of two radicals to yield the coupled products in a frozen state. Therefore, the coupled products formation should be explored as a possible mechanism for the increased radiation and photosensitivity of biological systems when thymine in DNA is replaced with 5‐halouracil. In addition, these compounds may be synthesized chemically, though, in very low yields, ˜7%.
REPAIR OF 313‐NM INDUCED LESIONS AND PHOTOPROTECTION IN YEAST CANDIDA GUILLIERMONDII
Authors: Fraikin G. Y. , Pospelov M. E. , Rubin L. B.
Published: January 2008

Abstract. The present communication is concerned with the effects of near‐UV radiation (300–380 nm) on yeast Candida guilliermondii. It was found that certain doses of 313 nm irradiation caused inactivation of the yeast which was exhibited in a way different from the lethal action of far‐UV radiation. It was also found that the cells inactivated by 313 nm are capable of recovering vitality, if incubated for some time in a non‐nutrient medium. The yeast inactivated by far‐UV radiation also proved to be capable of recovering, though to a lesser degree. Both 334 nm radiation and non‐lethal doses at 313 nm induced the photoprotective effect against far‐UV damage. The effect was exhibited if there was a certain time interval (2–4 h) between the exposures to photoprotective light and subsequent far‐UV radiation. Within this time interval the extent of photoprotection was dependent on temperature.
PHOTODYNAMIC INACTIVATION OF YEAST SENSITIZED BY EOSIN Y
Authors: Cohn G. E. , Tseng H. Y.
Published: January 2008

Abstract. Wild‐type diploid yeast has been irradiated with visible light in the presence of eosin Y to investigate the photodynamic inactivation of this model eukaryote. Light, eosin Y and oxygen were all required for substantial inactivation, and no dark recovery was detected. Long periods of irradiation were required for greater than 90% inactivation, corresponding to a very small low‐dose quantum yield. Neither binding nor uptake of the dye by yeast was detected. Corrections for the photooxidative bleaching of eosin Y during irradiation indicate that bleaching causes a significant reduction in the apparent rate of inactivation. The results suggest that eosin Y acts as an extracellular sensitizer where the likelihood of damage to the cell envelope is enhanced.
THE PHOTOINACTIVATION OF THE RESPIRATORY CHAIN IN SARCINA LUTEA (MICROCOCCUS LUTEUS) AND PROTECTION BY ENDOGENOUS CAROTENOID
Authors: Anwar M. , Prebble J.
Published: January 2008

Abstract. Irradiation of isolated membranes of Sarcina lutea (Micrococcus luteus) with blue light rapidly inactivated the respiratory malate oxidase system under aerobic but not anaerobic conditions. This inactivation was much faster than that seen in whole cells suggesting that the intact organism possesses protective mechanisms capable of preventing or repairing light damage. Three photosensitive sites have been detected by comparing the effect of blue light on membranes from the carotenoid‐containing wild‐type and a carotenoidless mutant. The sites have been identified as the initial malate dehydrogenase enzyme, a flavoprotein assayed by phenazine methosulphate reduction, a sulphydryl group associated with the dehydrogenase complex but not involved in phenazine methosulphate reduction and the respiratory quinone, menaquinone. Menaquinone was found to be sensitive only in carotenoidless membranes and not in membranes from the pigmented wild‐type. Studies of the variation of photosensitivity with wavelength suggest that the three sites are sensitized by different chromophores and that the quinone acts as its own photosensitizer.
DEPENDENCE OF THE TRIPLET YIELD ON EXCITATION ENERGY IN ALL‐TRANS AND 11‐CIS RETINAL*
Authors: Hochstrasser Robin M. , Narva David L.
Published: January 2008

Abstract. The triplet‐triplet absorption of all‐trans and 11‐cis retinal was measured as a function of the exciting radiation from 423 nm to 365 nm in a glass of 3‐methylpentane at 77 K. This experiment was also accomplished with all‐trans retinal in hexane at ambient temperature. The relative triplet formation quantum yields of all‐trans and 11‐cis retinal at 77 K were found to be independent (±10%) of the frequency of the exciting radiation. At room temperature we measured an increase in this relative quantum yield for all‐trans retinal from 1.0 at 365 nm to 1.82 at 423 nm [Bensasson et al. (1975) measured an absolute quantum yield of 0.45 at 353 nm]. These results are used to evaluate previous interpretations for photophysical decay processes in all‐trans retinal, and previous suggestions for wavelength dependent radiationless transitions are shown to be unacceptable. High energy excitation of 300 K solutions of all‐trans retinal produce excited states that result in less efficient intersystem crossing. These states appear to be inaccessible in the 77 K matrices. We suggest that steric restrictions introduced by the retinal matrix interaction at 77 K are able to block this new internal conversion pathway back to the ground state.
THE EPIDERMAL BIOSYNTHESIS OF CHOLECALCIFEROL (VITAMIN D3)
Authors: Beadle Peter C.
Published: January 2008

Abstract— An attempt has been made to calculate the rate of ultraviolet absorption by 7‐dehydrocholes‐terol. provitamin D3, in the epidermis as a function of latitude, season and skin type, in the hope that it will provide an upper‐limit estimate of the epidermal vitamin production. The results indicate that a significant fraction of the total epidermal production may occur in the stratum corneum with figures of 15 and 31% being found for non‐pigmented and pigmented epidermises, respectively. Total production in negroid epidermis is predicted to be about 40% of that in the Caucasian one and the latitudinal variation is greater than the seasonal variation, in agreement with the behaviour of the available solar ultraviolet. Overall production rates are sufficiently high for it to be unnecessary to invoke an enhanced absorption mechanism for the provitamin, although the results do indicate that there may be a risk of deficient production above about 40oN.
RADIATION ENHANCED REACTIVATION OF NUCLEAR REPLICATING MAMMALIAN VIRUSES*
Authors: Bockstahler Larry E. , Lytle C. David
Published: January 2008

Abstract— When CV‐1 monkey kidney cells were UV‐irradiated (0–18 J/m2) or X‐irradiated (0–10krads) before infection with UV‐irradiated simian adenovirus 7 (SA7) or simian virus 40 (SV40), increases in the infectivity of these nuclear replicating viruses as measured by plaque formation were observed. These radiation enhanced reactivations, UV enhanced reactivation (UVER) and X‐ray enhanced reactivation (X‐ray ER), occurred both when virus infection immediately followed irradiation of the cells (except for X‐ray ER with SA7) and when virus infection was delayed until 3–5 days after cell irradiation. While there was little difference in the levels of reactivation of UV‐irradiated SV40 between immediate and delayed infection, delayed infection resulted in higher levels of reactivation of SA7. X‐ray enhanced reactivation of UV‐irradiated Herpes simplex virus persisted for several days but did not increase. Thus, X‐ray enhanced and UV enhanced reactivations of these mammalian viruses were relatively long‐lived effects. Essentially no UVER or X‐ray ER was found in CV‐1 cells for either immediate or delayed infection with UV‐irradiated vaccinia virus or poliovirus, both of which replicate in the cell cytoplasm. These results suggest UVER and X‐ray ER in mammalian cells may be restricted to viruses which are replicated in the cell nucleus.
THE EFFECT OF ULTRAVIOLET LIGHT ON ARRESTED HUMAN DIPLOID CELL POPULATIONS
Authors: Kantor G. J. , Warner C. , Hull D. R.
Published: January 2008

Abstract— The results of experiments to determine an effect of UV (254 nm) on human diploid fibro‐blasts (HDF) arrested with respect to division by using 0.5% fetal calf serum in the culture medium are reported. A fraction of cells from irradiated arrested populations, maintained in the arrested state post‐irradiation, is lost from the populations. The extent of cell loss is hence‐dependent and cell strain specific. A Xeroderma pigmentosum cell strain is more sensitive to UV than are normal HDF. No differences in sensitivity were observed when arrested populations established from normal HDF populations of various in vitro ages were used. The length of the pre‐irradiation arrested period affects the sensitivity of normal HDF, which appear more resistant at longer arrested periods, but not the sensitivity of arrested Xeroderma populations. These results suggest that DNA repair processes play a role in maintaining irradiated cells in the arrested state. The suggestion is made that the lethal event caused by UV is an effect on transcription leading to an inhibition of required protein synthesis.
ON THE NATURE OF CHLOROPHYLL a IN AQUEOUS MICELLAR SYSTEMS
Authors: Mukherjee T. , Sapre A. V. , Mittal Jai P.
Published: January 2008

Abstract— Absorption and fluorescence spectra of chlorophyll a in aqueous micellar solutions were studied. Solutions in anionic micelles gave an absorption band at 740 nm, attributable to microcrystal‐ line chlorophyll a. Solutions in cationic and nonionic micelles do not show this band. The positions of the spectral bands in anionic micelles and the possible structure of microcrystalline form are discussed. A comparison is made of the behaviour of microcrystalline form in hydrocarbon solvents and in micellar solutions.
EFFECT OF SODIUM AZIDE ON PHOTODYNAMIC INDUCTION OF GENETIC CHANGES IN YEAST
Authors: Kobayashi Katsumi
Published: January 2008

Abstract— In view of the increasing attention to 1O2 (1Δg) participation in the photodynamic action, different types of genetic changes in Saccharomyces cerevisiae by acridine orange sensitization were compared with respect to the response to N3‐, a well known quencher of 1O2. The induction of mitotic crossing over with respect to ade 2 locus and mitotic gene conversion at trp 5 locus were suppressed by the addition of N3‐ suggesting the involvement of 1O2 as a major intermediate. However, the induction of reverse mutation at ilv 1 was only slightly suppressed. These results may indicate that there are two types of photodynamic DNA damage; one is produced via 1O2 and the other via non‐1O2 reaction pathway which lead to mitotic gene conversion and mitotic crossing over, and to mutation, respectively.
OPTICAL CELLS TO INVESTIGATE REACTIONS OF SINGLET OXYGEN IN LIQUID SOLUTIONS AT HIGH OXYGEN PRESSURES*
Authors: Keltie Richard J. , Koroll Grant W. , Singh Ajit
Published: January 2008

Abstract— We have designed cells to study the reactions of singlet oxygen and related species in which the pressure of oxygen can be varied between 1 and 150atm. (0.1 and 15MPa). These cells allow routine absorption spectroscopy of solutions, optical excitation of 3O2 to 1O2 in a laser photolysis system and formation of 1O2 and O‐2aq in a pulse radiolysis system. The laser photolysis cell and the pulse radiolysis cell are parts of a flow system which operates independently of the gas pressure. In designing these cells safety has been one of the important considerations.
GENERATION AND PARTICIPATION OF O‐2 IN 2‐NITROPROPANE DIOXYGENASE REACTION
Authors: Kido Toshiko , Hashizume Katsumi , Soda Kenji , Asada Kozi
Published: January 2008

Abstract— 2‐Nitropropane dioxygenase (EC 1. 13. 11) of the yeast Hansenula mrakii catalyzes the oxygenative denitrification of 2‐nitropropane as follows:

image

The enzyme is significantly inhibited by superoxide dismutase and various scavengers for superoxide such as cytochrome c, epinephrine, thiols and polyhydric phenols. The scavengers added to the reaction mixture were oxidized or reduced. The addition of superoxide dismutase and the omission of 2‐nitropropane or oxygen prevented the oxidation and the reduction of the scavengers. The enzyme catalyzes the formation of nitrite from 2‐nitropropane by KO2 added anaerobically.

One mole of NADH is bound per mole of the enzyme and predominantly the pro‐R hydrogen of bound NADH is transferred to superoxide formed enzymatically or provided externally. The enzyme shows incomplete stereospecificity for hydrogen transfer from NADH.
RADIATION PROTECTION BY SUPEROXIDE DISMUTASE
Authors: Petkau Abram
Published: January 2008

Abstract— Protection of X‐irradiated mice by bovine superoxide dismutase is enhanced when the enzyme is given intravenously both before and after the exposure. With the combined treatment, the LD50(30) dose is increased from 734 ± 8 to 1144 ± 15rad for a dose reduction factor of 1.56 ± 0.04. This protection occurs in a dose range where hematological damage is an important contributor to animal lethality. The proliferative capacity of bone marrow stem cells, X‐irradiated in air, is protected by exogenous superoxide dismutase. The enzyme increased the D0 from 105 ± 6 to 290 ± 34rad, an increase that represents 83% of the oxygen enhancement ratio of 3.3. In N2 and N2O, the D0 of the stem cells is 348 ± 50 and 327 ± 55 rad, respectively, and the enzyme does not significantly change these values.
MECHANISMS OF RADIOPROTECTION—A REVIEW
Authors: Copeland Edmund S.
Published: January 2008

Abstract— Theories of radiation protection can be considered at both the molecular and biochemical‐physiological levels. Four molecular level protection hypotheses, radical scavenging, hydrogen transfer reactions, the mixed disulfide hypothesis and the endogenous nonprotein sulhydryl hypothesis, probably describe different aspects of the actual protection mechanism, although each has inconsistencies. At the biochemical‐physiological level, hypothermia induction, hypoxia induction and biochemical shock may be involved in protection of the organism against radiation induced damage and death. It is most likely that no single mechanism can account for the protection offered by a radioprotective drug. Certain compounds may operate primarily by means of physiological effects resulting in hypoxia or hypothermia in critical tissues. Others may operate primarily by influencing the intrinsic radiosensitivity of target molecules by causing localized radical scavenging or by donating a hydrogen atom. Metabolic effects such as biochemical shock, release of endogenous nonprotein sulfhydryls, induction of structural changes in target molecules or delay in DNA synthesis and cell division are also possible mechanisms for radioprotection.
A LINEAR DICHROISM STUDY OF THE ORIENTATION OF AROMATIC PROTEIN RESIDUES IN MAGNETICALLY ORIENTED BOVINE ROD OUTER SEGMENTS
Authors: Becker Joseph F. , Trentacosti Florence , Geacintov Nicholas E.
Published: January 2008

Abstract— Linear dichroism measurements using magnetic field oriented bovine visual rod outer segments have been made in the UV and visible spectral regions. The results indicate that the planes of the aromatic amino acid residues of rhodopsin tend to be oriented normal to the membrane plane both before and after bleaching. In contrast, the retinal chromophore which tends to be oriented with its absorption oscillator parallel to the membrane plane before bleaching is randomly oriented about 10min after bleaching whereas the membranes remain oriented. Estimates of the anisotropy in the diamagnetic susceptibility of rhodopsin aromatic residues indicate that the anisotropic magnetic properties of these protein residues are sufficient to account for the observed orientation of visual rod outer segments in a homogenous magnetic field.
INTRINSIC POLARIZATION AND ROTATIONAL DEPOLARIZATION OF FLUORESCENCE OF DNA BASES IN AQUEOUS SOLUTION AT ROOM TEMPERATURE*
Authors: Morgan James P. , Daniels Malcolm
Published: January 2008

Abstract— A counting procedure is described for determining the polarization characteristics of very weak emission. The degree of polarization of weak emission of DNA bases in aqueous solution at room temperature is found to he high and positive, and shows an inverse correlation with their emission quantum yields which can be understood in terms of a competition between emission lifetimes and rotational relaxation times. For 5‐methylcytosine the emission quantum yield can be changed by varying the acidity and the corresponding degrees of polarization show the behavior expected from Perrin's relation. The ratio τo/τrot is discussed in terms of anisotropic relaxation and calculations of τ0.
THE ROLE OF CYTOKININS IN THE PHYTOCHROME‐MEDIATED GERMINATION OF DORMANT IMBIBED CELERY (APIUM GRAVEOLENS) SEEDS
Authors: Thomas T. H. , Biddington N. L. , Palevitch D.
Published: January 2008

The dormancy of celery seeds was broken by red light treatment given during imbibition and this effect was reversed by far‐red light. The exact quantitative relationship between the timing and duration of red light treatment and dormancy‐break has not been elucidated. However, the accumulated effect of daily 5 min exposures was greater than a single 5 min exposure on the second day of imbibition. The effects of red light treatment were simulated by treatment with a mixture of the gibberellins A4 and A7 and N6‐‐benzyladenine. A correlation between the requirement for red light and the requirement for exogenous cytokinins in the presence of GA4/7 was demonstrated by using six cultivars with different dormancy characteristics. In order to investigate the role of natural cytokinins in dormancy‐break, quantitative and qualitative changes in cytokinins were measured in celery seeds immediately after red‐light treatments. Rapid increases in n‐butanol‐soluble cytokinins following irradiation were associated with concomitant decreases in water‐soluble cytokinins, suggesting a red light induced cytokinin conversion. Three of the cytokinins present in the n‐butanol fraction of celery seed extracts were chromatographically similar to zeatin, zeatin riboside and N6‐‐A2‐‐isopentenyladenosine (i6Ado). The elution profiles from a PVP column of two others were similar to BA and its riboside. The possibility that these two cytokinins act as specific dormancy‐breaking cytokinins in celery seeds is discussed. There was little evidence of reversal of the cytokinin conversion mechanism by far‐red light exposure.