bluuebunny/crossref_metadata_2025_split huggingface dataset:
STRUCTURAL FACTORS CONTROLLING THE ACTION OF UV LIGHT IN NUCLEIC ACIDS*
Authors: Lang H. , Zimmer Ch. 
Published: January 2008

Abstract— UV light induced conformational effects of different deoxyoligonucleotides and deoxypolynucleotides containing thymine and adenine residues are investigated by means of CD measurements and quantum yield calculations. UV‐irradiation at the wavelengths 254, 280 and 313 nm indicate that unsensitized irradiation at low doses leads to thymine photoproduct formation of non‐cyclobutane type.In contrast to that irradiation at 313 nm in the presence of acetophenone causes different changes in the CD spectra due to the formation of thymine dimers of the cyclobutane type structure.Quantum yield calculations demonstrate a pronounced dependence of the photoproduct formation on the nucleotide sequence of the oligomers. Thus, clustering of thymine dimer formation can be neglected. Adenine photoproducts in the (A.T) containing oligomers are only formed at higher fluences. > 1.5 × 104 J/m2 and are biological less important events.
PHOTODECOMPOSITION OF CATECHOLAMINES. PHOTOPRODUCTS, QUANTUM YIELDS AND ACTION SPECTRUM OF ADRENALINE
Authors: Mol N. J. de , van Henegouwen G. M. J. Beyersbergen , Gerritsma K. W. 
Published: January 2008

Abstract—The photochemical decomposition of several catecholamines in aqueous solution was investigated. The respective aminochromes were found to be products of adrenaline and isoprenaline. Irradiation of adrenochrome and N‐isopropylnoradrenochrome produced their respective 5, 6‐dihydroxyindoles in addition to the ultimate formation of melanine. No trihydroxyindoles could be detected amongst the photoproducts of catecholamines.The action spectrum of adrenaline suggested that the catecholamine itself, in excited state, initiated the first step in the transformation process. The quantum yields for the decomposition were determined for several catecholamines: N‐alkyl compounds. decompose more rapidly under influence of light (λ 254 nm) than those with an unsubstituted amino group. In determining the quantum yields the use of corrections for the inner filter effect could be avoided.
INHIBITION OF 15‐HYDROXYPROSTAGLANDIN DEHYDROGENASE ACTIVITY BY NEAR‐ULTRAVIOLET LIGHT AND TRYPTOPHAN PHOTOPRODUCTS*
Authors: Sun Ming , Zigman Seymour , Tai Hsin‐Hsiung 
Published: January 2008

Abstract—The activity of NAD+ dependent 15‐hydroxyprostaglandin dehydrogenase. the major prosta‐glandin catabolic enzyme, was found to be effectively inhibited by near‐UV radiation and by tryptophan photoproduct. Both free tryptophan and tryptophan photoproducts enhance the inhibitory action of near‐UV light on the enzyme.
THE CONTRIBUTION OF RHODOSPZRZLLUM RUBRUM FERREDOXIN II TO IN VIVO EPR SIGNALS AND ITS ROLE IN ELECTRON TRANSPORT
Authors: Corker G. A. , Henkin B. M. , Sharpe S. A. 
Published: January 2008

Abstract—Evidence is presented that Fd II, an iron‐sulfur protein containing 4 irons and 4 acid‐labile sulfurs, is responsible for a number of signals previously reported detectable in cells of R. rubrum. When oxidized, Fd II exhibits a g = 2.012 EPR signal which is readily detected in R. rubrum cells. In our hands, Fd II is photochemically reduced to an EPR‐silent product contrary to the results of other investigators. However. in the presence of reducing agents. the reduced form is apparently denatured upon freezing. The denatured form exhibits EPR signals similar to some also previously observed in whole cells.Fd II catalyzes the ascorbate‐DCPIP linked photoreduction of NAD with R. rubrum chromatophores even in the presence of an inhibitor which suppresses the formation of pH and emf gradients. This result raises the possibility of a role for Fd II in non‐cyclic electron transport in R. rubrum.
MULTIPLE EXCITATIONS AND REACTION YIELDS IN PHOTOSYNTHETIC SYSTEMS
Authors: Mauzerall D. 
Published: January 2008

Abstract—Alternative explanations of the limited yield of product when bacterial reaction centers are excited by intense ps pulses (Moskowitz and Malley, Photochem. Photohiol. 27 55, 1978) are given. These alternatives, based on photoreversal or multitrap effects, can be experimentally distinguished by a predicted wavelength variation or by the effect of a second flash.
RAPID AND SENSITIVE OPTICAL ROTATION MEASUREMENT: KINETICS OF CONFORMATIONAL CHANGE OF RHODOPSIN INTERMEDIATE
Authors: Tsuda Motoyuki 
Published: January 2008

Abstract—A rapid and sensitive optical rotation (OR) measurement system using laser light has been developed to meet the demands of flash‐photolysis experiments. The optimal OR resolution of the apparatus is 0.3mdeg with 10 μs time constant with single shot. The OR resolution could be easily improved less than 0.1 mdeg with accumulation of data by a kinetic processor. Applications are briefly described for the study of transient conformational change of photochemical intermediates of octopus rhodopsin following a blue light flash.
PHOTOCHEMICAL REACTION BETWEEN PROTEIN AND NUCLEIC ACIDS: PHOTOADDITION OF TRYPTOPHAN TO PYRIMIDINE BASES*1
Authors: Reeve A. E. , Hopkins T. R. 
Published: January 2008

Abstract— The photochemical interactions between tryptophan and nucleic acid bases were studied. When aqueous solutions of tryptophan were irradiated (Λ > 260 nm) at neutral pH in the presence of each of the nucleic acid bases, pyrimidine bases but not purine bases were altered. Air was found to decrease the rate of reaction. Two classes of photoproducts were isolated by thin layer and ion‐exchange chromatography and partially characterized. One was the dihydro‐pyrimidine forms of the base (see Reeve and Hopkins, 1979) and the other consisted of tryptophan‐pyrimidine photoadducts. Four tryptophan‐uracil and two tryptophan‐thymine adducts each with a 1:1 molecular stochiometry were found. Spectroscopic measurements and a positive reaction with Ehrlich's reagent indicate that the indole nucleus remained intact, but that the pyrimidine base was reduced at the 5, 6 double bond. The absence of a positive ninhydrin reaction and the effect of pH on the quantum yield of the photoadduct formation indicated that the ionized a‐amino acid group of tryptophan was involved in photoadduct formation. Indole derivatives lacking an a‐amino group were also found to form photoadducts with pyrimidine bases.The experimental results are consistent with a reaction mechanism involving tryptophan excitation to the first excited singlet state as the initial event. Radical scavenging experiments indicate that tryptophan free radicals, formed by electron dissociation from the excited state, react with the ground state pyrimidine.
LIGHT AND pH INDUCED CHANGES IN THE SURFACE PRESSURE‐AREA ISOTHERMS OF BACTERIORHODOPSIN
Authors: Vivino A. , Berns D. S. , Brody S. S. 
Published: January 2008

Abstract— Pressure‐area isotherms of monolayers of purple membrane fragments were measured at an air‐water interface. The pH of the aqueous phase was varied from 2 to 10. Over the pH range 5 to 9 the area/molecule of bacteriorhodopsin was constant and illumination of the film had no effect on the isotherms.At pH's more acid than 5 and more alkaline than 9, there were large decreases in area/molecule. Under these conditions of extreme pH the monolayer was very sensitive to light. Illumination resulted in irreversible increases in area/molecule.
QUENCHING OF INTRAMOLECULAR AMINE‐HYDROCARBON EXCIPLEX FLUORESCENCE BY WATER
Authors: Ibemesi J. A. , El‐Bayoumi M. Ashraf 
Published: January 2008

Abstract— The quenching of intramolecular exciplex fluorescence in 2,6‐bis(methylamino)naphtha]ene, (II), 2,6‐bis(/V‐methyl, methylamino)naphthalene, (III) and 2,6‐bis(N‐dimethy], methylamino)naphthalene, (IV) by water was investigated. Exciplex fluorescence intensity decreased continuously with increase in water concentration; while monomer fluorescence intensity remained constant up to 25% of water, followed by a rapid increase in intensity.Absorption spectra showed that specific interaction occurred between water and ground state amine molecules at high concentrations (25% by volume) of water. These observations were interpreted in terms of a static quenching involving the interaction of water with the ground‐state amine and a dynamic quenching involving the interactions of water with the exciplex. Our observations explain the greater efficiency of exciplex‐fluorescence quenching by protic polar solvents.
SENSITIVITY TO PHOTOADDITION OF MONO‐AND BIFUNCTIONAL FUROCOUMARINS OF X‐RAY SENSITIVE MUTANTS OF SACCHAROMYCES CEREVISIAE
Authors: Henriques J. A. P. , Moustacchi E. 
Published: January 2008

Abstract— With the exception of rad53, seven other X‐ray sensitive mutants of the rad50 serie of Saccharomyces cerevisiae were found to be more sensitive than the wild type to photoaddition of Afunctional (3‐methoxypsoralen) and monofunctional (3‐carbethoxypsoralen) furocoumarins. The magnitude of sensitivity to killing is dependent upon the locus and the phase of growth.This means that in addition to the two repair pathways (excision‐resynthesis and mutagenic pathways) previously shown to be involved in repair of furocoumarins photo‐induced lesions, a third pathway is implicated in the repair of such lesions.
REDUCTION BY NEAR‐ULTRAVIOLET (334 nm) LIGHT OF E. COLI CAPACITY FOR PHAGE GROWTH DEPENDS UPON THE rel GENE AND 4‐THIOURIDINE
Authors: Wingo Richard J. , Fossum Tore , Luo Solomon , Jagger John 
Published: January 2008

Abstract— Near‐ultraviolet radiation (near UV; 300–380 nm) has long been known to produce a transient reduction of the capacity of bacteria to support phage growth. The present work shows that, at high fluenœs (40–100 kJ/m2), 85% of 334‐nm‐induced reduction of capacity in Escherichia coli B/r requires the rel gene; that is, it results from rel‐gene activity caused by the near‐UV treatment. This rel‐gene activity leads to (1) a bacterial growth delay and concomitantly lowered bacterial metabolism, and (2) a parallel delay in phage development, with a considerable depression of burst size. We propose that the observed effects on phage development are a consequence primarily of the lowered bacterial metabolism, but they may also result partly from a direct inhibition of phage DNA synthesis by the rel gene product, these effects together leading to the observed reduction of capacity in a rel+ strain. The remaining 15% of capacity reduction, observed in a rel strain, has an unknown mechanism, but does appear to involve a delay in phage development.At least 95% of the total capacity reduction observed in the rel+ strain in the range 40–100 kJ/m2 requires the presence of 4‐thiouridine, an unusual base in E. coli transfer RNA, which is presumably both the chromophore and the target for near‐UV‐induced capacity reduction.
RHODOPSIN‐PHOSPHOLIPID INTERACTION IN DETERGENT AND IN THE DISK
Authors: Ikai Atsushi , Tamura Eriko , Nishigai Masaaki 
Published: January 2008

Abstract— Solubilization of cattle disk membrane in deoxycholate shifted the fluorescence emission maximum from 324 to 331 nm without changing the intensity. Tryptophyl residues are probably located at the hydrophobic interface between rhodopsin and phospholipid. Depletion of deoxycholate concentration from the solubilized disk by Sephacryl 200 column chromatography produced rhodopsin‐phospholipid complexes with different characteristics that are the intermediate stages of membrane formation from homogeneous molecular solution. Association of rhodopsin takes place in a two‐dimensional way even in the appreciably low content of phospholipid.Sedimentation velocity studies showed that reassociation of lipid and rhodopsin occurs in 0.2% deoxycholate as well as in 0.05% sodium dodecylsulfate.By using Sephacryl column we can now prepare, within 60 min, the rhodopsin‐lipid complex that can form large vesicles in response to the addition of MgCl2 without dialysis. This type of lipoprotein complex will be useful to the study of the mechanism of the two dimensional membrane formation.
RECONSTITUTION OF SQUID RHODOPSIN IN RHABDOMAL MEMBRANES
Authors: Seki Takaharu , Hara Reiko , Hara Tomiyuki 
Published: January 2008

Abstract— Squid opsin which is capable of combining with 11‐cis or 9‐cis retinal to reconstitute photo‐pigment has been prepared by irradiation of rhabdomal membranes with orange light (> 530 nm) in the presence of 0.2 M hydroxylamine. When the irradiation is carried out either at concentrations of hydroxylamine higher than 0.2 M or with light of wavelength shorter than 530 nm, rhodopsin in the membranes is bleached quickly, but the ability of the resultant opsin to form rhodopsin is greatly reduced.The optimum pH for rhodopsin regeneration in rhabdomal membranes was found to be between 6.5 and 8.5. The rate of regeneration of rhodopsin increases with raising temperature, and at about 20°C it is almost the same as that of isorhodopsin. Even after solubilization in digitonin solution, opsin still preserves the ability to reform rhodopsin.All‐trans retinal can be incorporated into retinochrome‐bearing membranes, in which it is isomerized into 11‐cis isomer by the photoisomerase activity of retinochrome. Rhabdomal membranes retaining active opsin can take up 11‐cis retinal from retinochrome membranes so as to synthesize rhodopsin.
POLARIZED FLUORESCENCE OF 5‐METHYLCYTOSINE SPECIES IN SOLUTION AT ROOM TEMPERATURE
Authors: Anderson Bruce E. , Callis Patrik R. 
Published: January 2008

Abstract—Fluorescence yields (πf,'s) and polarizations (P) are measured for aqueous 5‐methylcytosine (˜ 0.1 mM) at 20°C as a function of pH over the range 2–14. Both properties change abruptly and in parallel at pH's corresponding to the known pKa values. Polarizations were also obtained for the 5‐methylcytosine cation, neutral and anion species in ethylene glycol water glass at ˜180K. The weak fluorescence of the neutral and cation species at 20°C was polarized almost as highly as at low temperature. When the fluorescence lifetimes are assumed to be correctly given by the product of calculated radiative lifetimes and quantum yields, the polarizations are found to be consistent with rotational diffusion rates ˜4 times faster than predicted from Stokes‐Einstein models for the neutral and anion species. The cation seemed to rotate about two times more slowly than the neutral and anion species. It was also shown that the properties of the three species are such that a plot of 1/P vs apparent πf in the pH range 2–11 is fortuitously linear.
THE ANAEROBIC PHOTOLYSIS OF TRYPTOPHAN CONTAINING PEPTIDES
Authors: Dillon James 
Published: January 2008

Abstract—The anaerobic photolysis of either Glycine‐l‐Tryptophan or Glycine‐l‐Tryptophan‐Glycine, leads to one major product. These analogous compounds are shown to be the result of deamination followed by cyclization to the 4‐position of indole. Structural proof is given, and the possible mechanisms involved in the reaction are discussed.
ULTRAVIOLET INACTIVATION OF THE MIDI VARIANT OF Qβ RNA: UV‐INDUCED ‘KINETIC BARRIERS’ TO REPLICATION AT TWO TEMPERATURES
Authors: O'Hara Patrick J. A. , Gordon Milton P. 
Published: January 2008

Abstract—MDV‐1 RNA is a small variant of bacteriophage Qβ, and is an active template in replication reactions catalyzed by Qβ replicase. The predominant lesion formed when MDV‐1 is irradiated with 254 nm light with a dose of 2500 Jm‐2 is uridine hydrate, which is chemically closely related to the major thymidine products formed in DNA by ionizing radiation. We have found that the replication of irradiated MDV‐1 RNA is inhibited at 37°C as well as 12°C. However, while replication appears to be blocked at the sites of photolesions at 12°C, Qβ replicase ‘pauses’ at the lesions before continuing elongation at 37°C. This effect is not caused by reversion of the photoproducts to parent material at the higher temperature. ‘Pauses’ (caused by ‘kinetic modulators’) during the synthesis of nucleic acids from unirradiated templates have been reported to occur in a number of systems and may play a role in the regulation of transcription and replication. Our results suggest that one consequence of radiation damage to nucleic acid bases may be the introduction of lesions which mimic such modulators, leading to aberrations in the regulation of nucleic acid synthesis.
HERPES SIMPLEX VIRUS PRODUCES LARGER PLAQUES WHEN ASSAYED ON ULTRAVIOLET IRRADIATED CV1 CELLS
Authors: Coohill Thomas P. , Babich Michael A. , Taylor William D. , Snipes Wallace 
Published: January 2008

Abstract—Plaque development for either untreated or UV treated irradiated Herpes simplex virus Type 1 is faster when assayed on UV irradiated CV1 cells. This Large Plaque Effect only occurs if a minimum delay of 12h between cell irradiation and viral inoculation is allowed. Shorter delays give plaques that are smaller than controls (unirradiated virus‐unirradiated cells). The effect is maximal for a 48‐h delay and remains unchanged for delays as long as 84h. The effect is greatest for cell exposures of 10J m‐2.
THE WAVELENGTH DEPENDENCE OF HERPES SIMPLEX VIRUS INACTIVATION BY ULTRAVIOLET RADIATION
Authors: Detsch Richard M. , Bryant F. Dudley , Coohill Thomas P. 
Published: January 2008

Abstract—The effect of different wavelengths of ultraviolet (UV) radiation on Herpes simplex virus when assayed on mammalian cells (measured by plaque forming ability) was investigated. The wavelength dependence of viral inactivation was obtained for 11 different wavelengths over the region 238–297 nm. The resulting action spectrum does not closely follow the absorption spectrum of either nucleic acid or protein. The most effective wavelengths for viral inactivation are over the region 260–280 nm.
LOSS OF PHOTOREACTIVABILITY DURING LIQUID‐HOLDING IN ESCHERICHIA COL1 WP2
Authors: Roczen Diktmar , Mennigmann Horst‐Dieter 
Published: January 2008

Abstract—Loss of photoreactivability during liquid‐holding occurs much faster in Escherichia coli WP2 than has been reported for another strain of B/r (Harm, 1968). The underlying mechanism considerably reduces the maximum photoreactivation attainable within 30 min. The addition of caffeine to UV irradiated strain WP2 prevents the loss of photoreactivation activity. Similarly, a uvrA mutant also fails to show this loss of photoreactivation capacity. These results are consistent with the view that in WP2 the initial steps of excision repair take place during liquid‐holding and that they can preclude photoreactivation at a high rate. But it remains to be elucidated why different strains of B/r differ with respect to this rate.
SIMULATION ANALYSIS OF THE PHOTOCONVERSION PROCESS OF SQUID RHODOPSIN AT LIQUID HELIUM TEMPERATURE
Authors: Sarai Akinori , Kakitani Toshiaki , Shichida Yoshinori , Tokunaga Fumio , Yoshizawa Toru 
Published: January 2008

Abstract—The photoconversion process among squid rhodopsin, bathorhodopsin isorhodopsin and hypsorhodopsin was studied at liquid helium temperature. We evaluated the relative quantum yields of the photoconversion among four pigments by analysing the time‐dependent change of absorption spectra. The result suggests that hypsorhodopsin is the common intermediate of rhodopsin and isorhodopsin, and there is no direct conversion between rhodopsin and isorhodopsin. Furthermore, rhodopsin converts to hypsorhodopsin or bathorhodopsin much more efficiently than does isorhodopsin, and bathorhodopsin does not convert directly to hypsorhodopsin. It was also found that rhodopsin and isorhodopsin convert to bathorhodopsin more efficiently than to hypsorhodopsin. In particular, the quantum yield of conversion from rhodopsin to bathorhodopsin was found to be about twice as large as that from rhodopsin to hypsorhodopsin. This result is somewhat in disagreement with the result obtained from the laser flash experiments at room and liquid nitrogen temperatures. The reason for the difference between the two experimental results is discussed.
LIGHT‐INDUCED CAROTENE SYNTHESIS IN MUTANTS OF PHYCOMYCES WITH ABNORMAL PHOTOTROPISM
Authors: Jayaram M. , Leutwiler L. , Delbrück M. 
Published: January 2008

Abstract—Mutants of Phycomyces. abnormal in their phototropic responses (the mad mutants), have been tested for their responses in light‐induced carotene synthesis (LICS). The amount of carotene synthesized at any given fluence is significantly lower in the madA, madB and madD mutants than in the wild type. The amount of carotene is not lower in other mad mutants (madC, madE, madF and madG). The double mutant mad A madB and the triple mutant mad A madB madC show stronger effects. The wild type strain, as well as those carrying a single mad mutation (madA and madB) or those carrying two or three mad mutations (madA madB. madA madB madC) show closely similar sensitivity to LICS. This contrasts with phototropism and photoinitiation of sporangiophores which are sensitive to extremely small signals in the wild type and in which the madA mutation decreases the sensitivity by nearly a factor of 104 and madB mutation by a factor of 105. It appears that LICS does not share the signal amplification mechanisms characteristic of the other two responses.
NMR ANALYSES OF TRYPTOPHAN‐8‐METHOXYPSORALEN PHOTOREACTION PRODUCTS FORMED IN THE PRESENCE OF OXYGEN
Authors: Megaw J. , Lee‡ J. , Lerman S. 
Published: January 2008

Abstract—Proton‐made spectroscopy was performed on solutions of l‐tryptophan and 8‐mcthoxypsoralen (8‐MOP) in either D2O or DMSO‐d6 in the presence of oxygen before and after irradiation with 360 nm monochromatic light. Irradiation results in the loss of hydrogen atoms at the 3. 4 and 4′. 5′ positions of 8‐MOP and at the indole C2 position of tryptophan. Changes in the aliphatic regions of the spectra also occur with irradiation. It is postulated that generation of photoreaction products between 8‐MOP and tryptophan involves the 3.4 and 4′.5′ positions of 8‐MOP and the imidazole moiety of tryptophan.Reprint requests to: Dr J. Megaw, Laboratory for Ophthalmic Research, Emory University School of Medicine, Atlanta. Georgia 30322. USA.
SPIN TRAPPING OF THE SUPEROXIDE RADICAL BY 4‐(N‐METHYLPYRIDINIUM) t‐BUTYL NITRONE
Authors: Sanderson Douglas G. , Chedekel Miles R. 
Published: January 2008

Abstract—The synthesis of 4‐(N‐methylpyridinium) t‐butyl nitrone (4‐MePyBN) and its use as a spin trap for superoxide radicals produced in aqueous solutions is reported (aN= 13.78 G, aHß= 1.65 G, and g = 2.0091). The half‐life of the spin adduct as a function of pH (83 s at pH 5.5, 78 s at pH 7.0, and 65 s at pH 8.0) the effects of iron salts, diethylenetriaminepentacetic acid (DETAPAC), and superoxide dismutase were examined, and comparisons made between 4‐MePyBN and 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO) as spin trapping agents for the superoxide radical.
PHOTOCHEMICAL AND FREE RADICAL INITIATED REACTIONS OF 1,3‐DIMETHYLTHYMINE WITH ETHANOL
Authors: Shetlar Martin D. 
Published: January 2008

Abstract—The photochemically induced reaction of 1,3‐dimethylthymine (DMT) with ethanol gives four major alcohol adducts. These have been identified as l,3‐dimethyl‐6‐(1‐hydroxy‐1‐ethyl)thymine (1), 1,3‐dimethyl‐5‐(2‐hydroxy‐l‐pyl)uracil (2), and the cis and trans isomers of 5,6‐dihydro‐l,3‐di‐methyl‐6‐(l‐hydroxy‐l‐ethyl) thymine (3 and 4). The compounds 3 and 4 have been shown to be identical to the adducts produced in y‐ray irradiated ethanolic aqueous solutions of DMT. Cyclobutane dimers of DMT are also found in the photochemical reaction mixture. Reaction of 1‐hydroxyethyl radicals with DMT, initiated by decomposition of di‐t‐butyl peroxide, leads to formation of the same alcohol adducts, as well as to DMT adducts containing two molecules of ethanol. The acetone sensitized reaction of DMT with ethanol gives 1,3, and 4, along with a variety of adducts incorporating the acetone sensitizer.