bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNA PHOTOREACTIVATING ENZYME FROM SILKWORM
Authors: Muraoka Noriko , Okuda Atsuyuki , Ikenaga Mituo 
Published: January 2008

Abstract—An ammonium‐sulfate‐precipitable (33–70%) fraction in extracts from eggs of silkworm Bombyx mori contains photoreactivating enzyme that reactivates the transforming activity of UV inactivated Hemophilus influenzae DNA. The action spectrum for in vitro photoreactivation with the enzyme has a broad peak around 365–385 nm, with a shoulder extending to 460 nm. This relatively higher photoreactivation efficiency at wavelengths longer than 450 nm seems to be a unique feature of DNA photoreactivating enzyme of silkworm. Using gel filtration, a mol wt of 42,000 was estimated for the enzyme. Optimum and isoionic pH of the enzyme were 7.2 and 5.4, respectively. These properties of silkworm enzyme are within the range of variations in reported biochemical characteristics of photoreactivating enzymes from different species.
EXISTENCE OF HYPSORHODOPSIN AS THE FIRST INTERMEDIATE IN THE PRIMARY PHOTOCHEMICAL PROCESS OF CATTLE RHODOPSIN
Authors: Kobayashi Takayoshi 
Published: January 2008

Abstract—It has long been believed that bathorhodopsin is the first intermediate of visual process for cattle rhodopsin. In the present paper hypsorhodopsin is shown to be the first intermediate by the use of picosecond spectropic technique. The main first intermediate, hypsorhodopsin, is formed with the time constant of 15 ± 5 ps. The time constant of the formation of bathorhodopsin from hypsorhodopsin is 50 ± 20 ps. Bathorhodopsin intermediates formed directly from excited state rhodopsin and those formed indirectly through hypsorhodopsin are 71/2#% and 93%, respectively, of total bathorhodopsin intermediates in octylglucoside buffered solution. Batho intermediates formed directly and indirectly are 0% and 100%. respectively, of total batho intermediates in LDAO buffered solution.
PHOTOCONDUCTIVITY AND PHOTOVOLTAIC EFFECTS IN LANGMUIR‐BLODGETT FILMS OF CHLOROPHYLL‐a
Authors: Jones R. , Tredgold R. H. , O'Mullane J. E. 
Published: January 2008

Abstract—The DC photoconductivity and photovoltaic effect in Langmuir films of Chlorophyll‐a (Chi a) of precisely controlled thickness formed between Al and Au electrodes have been extensively investigated. The dark conductivity and dark voltage are almost abolished in a N2 atmosphere. The action spectrum of the photocurrent closely resembles the monolayer absorption spectrum of Chl indicating that the primary event in photoconduction is the generation of singlet excited states. Thicknessdependence studies on the photoconductivity indicate that carrier generation is a surface process and that the mean diffusion length of the excited state is approximately 20 nm. In short (˜1 s) light exposures the photocurrent always increases linearly with both the applied voltage and the light intensity. In continuous light the current‐voltage characteristics are highly non‐linear and the photocurrent shows a square‐root intensity dependence at high intensities and small applied potentials. These results are interpreted in terms of second‐order recombination and charge‐trapping processes at high carrier densities. The photovoltage usually shows a logarithmic intensity dependence at high intensities and its maximum value in thick films is 800 mV with the Al electrode acquiring a negative polarity. This behaviour, together with some observations on the asymmetry of photocurrent‐voltage characteristics and the effect of substituting an aqueous top electrode for Au, further suggest that the photoactive surface is a p‐n junction between the Chl and Al2O3 layers.
INDUCED REPAIR IN ESCHERICHIA COLI: INDUCTION BY ULTRAVIOLET LIGHT AT‐79°C
Authors: Rader Mildred , Fluke D. J. , Pollard Ernest C. 
Published: January 2008

Abstract—Two of the phenomena associated with induced (S.O.S.) repair, namely induced inhibition of post radiation DNA degradation and induced radioresistance have been shown to be elicited by 245 nm radiation applied to E. coli cells in the frozen state at ‐79°C. The effect of radiation in this condition is considerably less photoreactivable than similar effects produced by exposure in the wet state. Since protein‐DNA crosslinks are believed to be formed under these conditions, such consequences of UV radiation appear to be a potent inducer of induced repair.
FLUORESCENCE PROPERTIES OF PORPHYRIN‐GLOBIN FROM HUMAN HEMOGLOBIN
Authors: Sebban Pierre , Coppey Maïté , Alpert Bernard , Lindqvist Lars , Jameson David M. 
Published: January 2008

Abstract—Fluorescence excitation and emission spectra, decays, and quantum yields are reported for the porphyrin‐globin of hemoglobin (HbdesFe) in aqueous solution of pH 8, at 4°C. A very weak fluorescence was observed in the UV (maximum at 334 nm), due to tryptophan and tyrosine residues, in addition to the strong porphyrin emission in the visible (maxima at 624 and 692 nm) reported previously. The absorption and fluorescence properties of the porphyrins of HbdesFe were compared to those for free porphyrin in organic solvents and in aqueous solution. The close similarity of the fluorescence decays and quantum yields in HbdesFe and in solution indicate the absence of stronger, specific porphyrin‐protein interactions; however, slight spectral shifts point to the existence of water molecules in the HbdesFe porphyrin environment. The fluorescence study also demonstrates the existence of efficient Trp‐porphyrin energy transfer of Förster type. The extent of transfer is in satisfactory agreement with the value expected from crystallographic data for hemoglobin. The results are discussed and compared to previous fluorescence studies of hemoglobin and apohemoglobin. An improved method for the preparation of HbdesFe is reported.
SPECTROSCOPY OF POLYENES—IV. ABSORPTION AND EMISSION SPECTRAL PROPERTIES OF POLYENE ALCOHOLS RELATED TO RETINOL AS HOMOLOGUES
Authors: Das Paritosh K. , Becker Ralph S. 
Published: January 2008

Abstract—A number of polyene alcohols related to retinol as homologues have been examined for their spectral and photophysical properties. The absorption spectra of the polyene alcohols with short polyene chainlength show an intense band system with its maximum at 3000–4000 cm‐1 above that of the main band system. The intensity of this higher‐energy band system decreases sharply as the polyene chainlength is increased. All the polyene alcohols fluoresce strongly or moderately strongly at 77 K, the intrinsic fluorescence lifetimes being significantly longer than those expected from the oscillator strengths of the main, low‐energy absorption band system. Fluorescence (relatively weak) is also observed at room temperature in the cases of polyene alcohols of long chainlength. A discussion is presented regarding the possible assignments of the various observed absorption band systems, state order and nature of the lowest excited singlet state, and aggregate formation (in 3‐methylpentane at 77 K) and its effect on spectral and photodynamical behavior.
OBSERVATIONS OF C‐S AND S‐S BOND CLEAVAGE IN THE PHOTOLYSIS OF DISULFIDES IN SOLUTION
Authors: Morine Gerald H. , Kuntz Robert R. 
Published: January 2008

Abstract— A comparison of the transient absorption spectra from the photolysis of disulfides in solution suggests that C‐S bond breakage is a common primary photolytic process. This process becomes more important as the resulting carbon centered radical is stabilized by increasing alkyl substitution or resonance interaction with an aromatic system. The perthiyl radical product is characterized by λmax?380 nm,ε380?1700 M−1 cm−1 and decays by second order kinetics with k2?3.7×108M−1 s−1 in water.In the presence of O2, the photolysis of disulfides which produce the thiyl radical give transient absorptions in the 500–600 nm region. Possible identities of these transients are discussed.
ELECTRIC DICHROISM OF PURPLE MEMBRANE SUSPENSIONS
Authors: Kimura Yoshiaki , Ikegami Akira , Ohno Koki , Saigo Satoshi , Takeuchi Yasuaki 
Published: January 2008

Abstract— Suspensions of purple membranes were exposed to reversing rectangular pulses of relatively low electric field (less than 100V/cm) at various frequencies. Orientation of the membranes was estimated by measuring linear dichroism at 565nm. In the electric field of frequency lower than about 10Hz the purple membranes tended to align perpendicular to the electric field. This orientation was induced mostly by permanent dipole which was perpendicular to the membrane surface. The value of permanent dipole moment was determined to be 140D per protein at pH 7.0, 25°C, in the presence of 5mM phosphate buffer.In an electric field of frequency more than 100Hz the membrane tended to align parallel to the electric field. Electric polarizability parallel to the membrane surface was estimated to be 1 ± 10−12 cm3 under the same conditions.Electric dichroism of light‐adapted and dark‐adapted purple membranes was found to coincide with each other at high frequency. From this result the angle of retinal to the membrane surface was concluded to be the same between light‐adapted and dark‐adapted bacteriorhodopsins.
BLUE and NEAR ULTRAVIOLET REVERSIBLE PHOTOREACTION IN THE INDUCTION OF FUNGAL CONIDIATION
Authors: Kumagai Tadashi 
Published: January 2008

Abstract— The effects of blue light and near UV light on the induction of conidiation in the fungus, Aliernuriu tomato, were investigated. Induction of conidiation was repeatedly controlled by alternating doses of near UV light and blue light. When the final light was near UV, conidiation was induced and conidia developed in the following darkness; when it was blue, the induction of conidiation was suppressed. When conidiation was induced by irradiation with a light mixed with near UV and blue, not only the time lag for inducing conidiation but also the amount of conidia formed were regulated by the fluence rates of both those lights.Thus, ‘mycochrome’ is considered to function as a photoreceptor system in the induction of conidiation of this fungus.
DIRECT RECORDING OF THE INITIALLY EXCITED AND THE SOLVENT RELAXED FLUORESCENCE EMISSION SPECTRA OF TRYPTOPHAN BY PHASE SENSITIVE DETECTION OF FLUORESCENCE
Authors: Lakowicz Joseph R. , Balter Aleksander 
Published: January 2008

Abstract Phase sensitive detection of fluorescence was used to directly record the initially excited and the solvent‐relaxed emission spectra of N‐acetyl‐L‐tryptophanamide in propylene glycol. Emission from the initially excited state was suppressed by adjusting the phase sensitive detector to be out of phase with the emission on the short wavelength side of the fluorescence spectrum. Then, the phase sensitive intensities revealed the emission spectrum of the solvent relaxed state. Similarly, the emission from the solvent relaxed state was suppressed by adjusting the detector to be out of phase with the emission on the long wavelength side of the spectrum, allowing the spectrum of the initially excited state to be directly recorded. Distinct emission spectra could be recorded when the solvent relaxation time was comparable to the fluorescence lifetime. At higher or lower temperatures, emission occurs predominantly from a single state, and suppression of the fluorescence signal at any arbitrary wavelength resulted in suppression of the entire emission. A simple theory is described which allows the spectral relaxation times to be estimated from the phase sensitive intensities. From this analysis we obtained an activation energy for spectral relaxation of 3 kcal/mol. This activation energy is smaller than that found for the temperature dependence of fluorescence depolarization, 7.8 kcal/mol. We attribute this difference to the smaller molecular motions required for spectral relaxation.The method of phase sensitive detection of fluorescence shows excellent resolving power and sensitivity, and this method should facilitate measurement of spectral relaxation around tryptophan residues in proteins.
INCREASED LEVELS OF UNSCHEDULED DNA SYNTHESIS IN UV‐IRRADIATED HUMAN FIBROBLASTS PRETREATED WITH SODIUM BUTYRATE
Authors: Williams J. I. , Friedberg E. C. 
Published: January 2008

AbstractPretreatment of growing normal and xeroderma pigmentosum (XP) human fibroblasts with sodium butyrate at concentrations of 5‐20 mM results in increased levels of DNA repair synthesis measured by autoradiography after exposure of the cells to 254 nm UV radiation in the fluence range 0‐25 J/m2. The phenomenon manifests as an increased extent and an increased initial rate of unscheduled DNA synthesis (UDS). This experimental result is not due to an artifact of autoradiography related to cell size. Xeroderma pigmentosum cells from complementation groups A, C, D and E and XP variant cells all exhibit increases in the levels of UV‐induced UDS in response to sodium butyrate proportional to those observed with normal cells. These UDS increases associated with butyrate pretreatment correlate with demonstrable changes in intracellular thymidine pool size and suggest that sodium butyrate enhances uptake of exogenous radiolabeled thymidine during UV‐induced repair synthesis by reducing endogenous levels of thymidine.
DIFFERENTIAL SENSITIVITY TO INACTIVATION OF NUR AND NUR+ STRAINS OF ESCHERICHIA COLI AT SIX SELECTED WAVELENGTHS IN THE UVA, UVB AND UVC RANGES*
Authors: Webb Robert B. , Tuveson R. W. 
Published: January 2008

AbstractThe radiation response of stationary‐phase cells of Escherichia coli strains RT4 (nur+) and RT2 (nur) was measured at 6 selected wavelengths between 254 and 405 ran. The relative response of the nur+. and nur strains was almost the same at 254 and 290 nm. However, the differential sensitivity of the RT4 and RT2 strains (ratio of the initial F37 values of the nur+ to the nur strains) was 2.7 at 313 nm, 3.2 at 334 nm, 3.1 at 365 nm, and 2.3 at 405 nm. Thus, the fluence enhancing effect of the nur genotype extends over the wavelength range of approximately 300 to 420 nm. The substantial effect of nur at 313 nm strongly suggests that the increased sensitivity of the nur strain is the consequence of a repair deficiency that reduces the efficiency of mending DNA lesions produced by UVA (320–400 nm) and UVB (290–320 nm), but not UVC (200–290 nm) radiation.
SUPPRESSION OF LIPID PHOTOPEROXIDATION BY QUERCETIN AND ITS GLYCOSIDES IN SPINACH CHLOROPLASTS
Authors: Takahama Umeo 
Published: January 2008

Abstract— Quercetin, quercitrin and rutin suppressed lipid photoperoxidation in spinach chloroplasts in the presence of 100 μM carbonylcyanide m‐chlorophenylhydrazone (CCCP) or 100 μM methyl viologen (MV). Fifty percent inhibition of lipid peroxidation by quercetin was observed between 30 and 50 μM. Concentrations of quercetin and rutin higher than 100 μM were required to obtain 50% inhibition. Ouercitrin was more effective than rutin in the suppression of lipid photoperoxidation.Photooxidation of the flavonols by chloroplasts in the presence of MV was suppressed by superoxide dismutase (SOD) more than 90%, and the rates of the oxidation decreased in order of quercetin, quer citrin and rutin suggesting that the reactivity of the flavonols with O2‐decreased in that order. The photooxidation of the flavonols by CCCP‐poisoned chloroplasts was partially suppressed by SOD. Radicals generated in the course of lauroyl peroxide degradation also oxidized the flavonols and the oxidation was insensitive to SOD. In these experiments, oxidation rate of quercetin was faster than those of its glycosides. The results obtained suggest that flavonols can function as antioxidants in chloroplasts by scavenging both O2‐and the radicals formed during lipid peroxidation.
PROPHAGE INDUCTION, MUTAGENESIS AND CELL SURVIVAL OF AMES' MUTAGEN TESTER STRAINS AFTER 8‐METHOXYPSORALEN PLUS ULTRAVIOLET LIGHT‐A
Authors: Wheeler Larry A. , DeMeo Michel , Lowe Nicholas 
Published: January 2008

Abstract— The furocoumarin 8‐methoxypsoralen (8‐MOP) is not detected as a mutagen in the standard Ames test either in the presence or absence of S9‐mix and/or ultraviolet light‐A (320–400 nm). The Ames strains have recently been shown to harbor bacteriophages that are inducible by carcinogens and mutagens. Psoralen (8‐MOP) plus UVA (PUVA) was found to be a potent prophage inducing treatment. Induction was observed in TA1535, TA1538, TA98, TA100, TA1978 and TA1975 with 0.1 μg/ml of 8‐MOP and 2.5 kJ/m2 of UVA. PUVA is a potent bactericidal treatment at concentrations of 8‐MOP above 0.5 μg/ml and 2.5 kJ/m2 in tester strains TA1535, TA1538, TA98, and TA100. PUVA is known to be bactericidal, but the cytotoxicity observed in this study was unique in that the frameshift tester strains (TA1538 and TA98) were more sensitive to the lethal effects of PUVA than the base pair tester strains (TA1535 and TA100). The differential cytotoxicity in such closely related strains led to the examination of some of the strains from which the Ames strains were derived. The data suggest mutations introduced into the Ames strains to make them more sensitive to carcinogens and mutagens (ΛuvrB) have resulted in an altered response to PUVA. It is postulated that TA1535 retains a DNA repair function that is lost by TA1538 during the selection for uvrB deficient strains.PUVA is also unique in that plasmid pKM101 does not confer enhanced survival of TA100 compared to TA1535 in contrast to many other carcinogens and mutagens. In conclusion, these data show that PUVA induces a pathway leading to prophage induction and demonstrates the potential use of prophage induction assays to detect mutagens and carcinogens that may otherwise be lethal to the Ames tester strains.
PHOTOTOXIC EFFECTS OF FOUR PSORALENS ON L1210 CELLS. THE CORRELATION WITH DNA INTERSTRAND CROSS‐LINKING
Authors: Nielsen Peter Eigil , Bohr Vilhelm 
Published: January 2008

Abstract—L1210 mouse leukaemia cells were treated with psoralen [S‐methoxy‐(XMOP), 4,5′,8‐trimethyI‐(TMP), 4′‐hydroxymethyl‐4,5′,8‐trimethyl‐(HMT) or 4′‐amino‐ methyl‐4,5′,8‐trimethylpsoralen (AMT)] in combination with long wavelength ultraviolct irradiation (Λ∼ 365 nm). In order to investigate the relative photobiological activities of the psoralens, cell viability and DNA‐synthesis activity as well as psoralen‐DNA photoaddition and DNA interstrand cross‐linking were measured after the treatment. In all assays the activity ranking order was found to he: TMP > HMT > AM7 > 8MOP. Furthermore, a direct correlation between phototoxicity, psoralen induced DNA interstrand cross‐links and inhibition of DNA synthesis was indicated. Finally, psoralen uptake by the cells appears to be an important determinant for phototoxicity, whereas their DNA photoreactivity does not.
THE CHARACTERISATION OF THE TRIPLET STATE OF CROCETIN, A WATER SOLUBLE CAROTENOID, BY NANOSECOND LASER FLASH PHOTOLYSES
Authors: Craw M. , Lambert C. 
Published: January 2008

Abstract— The triplet state of crocetin, which is a water soluble carotenoid, has been sensitized by psoralen. The triplet extinction coefficient, εT (73000 dm3 mol‐1 cm‐1 at 470 nm), the triplet‐triplet spectrum and the quantum yield of triplet formation, φT (less than 1%) are reported in aqueous solution.In order to calculate the extinction coefficient of crocetin it was necessary to obtain εT for psoralen in water (10000dm3 mol‐1 cm‐1 at 450 nm). This latter value was obtained using the complete conversion technique and is reported with the triplet‐triplet spectrum.
BINDING OF ANTHRACENE TO CELLULAR MACROMOLECULES IN THE PRESENCE OF LIGHT
Authors: Sinha Birandra Kumar , Chignell Colin F. 
Published: January 2008

AbstractUltraviolet radiation (δ > 295 nm) induced covalent binding of anthracene to DNA which increased with time and was not affected by oxygen. Irradiation in the presence of anthracene induced nicking of Col E, circular DNA and decreased the thermal denaturation temperature of calf thymus DNA. These effects were oxygen dependent, and were decreased by GMP. Irradiation of anthracene and human serum albumin resulted in covalent binding of the hydrocarbon to the protein accompanied by crosslinking of the protein. Protein crosslinking decreased under anaerobic conditions. Irradiation of anthracene bound to liposomes induced lipid peroxidation which was not affected by superoxide dismutase or catalase.
COMPARISON OF THE EFFECTS OF UV‐VISIBLE IRRADIATION OF MELANINS and MELANIN‐HEMATOPORPHYRIN COMPLEXES FROM HUMAN BLACK and RED HAIR
Authors: Persad Surujdeen , Menon I. Aravindakshan , Haberman Herbert F. 
Published: January 2008

AbstractClinical evidence indicates that people with light skin and red hair have a higher incidence of UV radiation‐induced diseases including cancer. It is not known whether this is because of the lower protection due to the smaller amounts of eumelanin present in the skin of these people or whether the presence of pheomelanin in their skin is responsible for the higher susceptibility to carcinogenesis. Irradiation of melanoproteins from red hair with UV‐visible light has been reported to produce superoxide. Comparative studies on the formation of superoxide during the irradiation of the melanins isolated from human black and red hair (BHM and RHM, respectively) are reported in this paper. These showed that no superoxide formation could be detected in the case of the BHM. whereas the formation of superoxide during the irradiation of RHM could be definitely demonstrated. Irradiation of the RHM with NADH resulted in the oxidation of more NADH than the irradiation of NADH with BHM. The observation that RHM is an active photosensitizer indicates that this property of pheomelanin present in light skin may at least partly be responsible for the harmful effect of radiation on people with light skin and/or red hair. Administration of hematoporphyrin followed by visible irradiation is a currently used mode of therapy for cancer. The present studies have shown that hematoporphyrin is bound to both BHM and RHM. The binding of hematoporphyrin to the melanins increased the formation of superoxide by RHM and the oxidation of NADH by both the melanins. The binding of porphyrins to melanins may have an influence upon the photosensitivity in diseases such as porphyrias and may also affect the therapeutic efficacy of hematoporphyrin.
DCMU‐INDUCED STIMULATION OF PHOTOSYSTEM I ELECTRON TRANSPORT. INVOLVEMENT OF MEMBRANE STRUCTURAL CHANGES
Authors: Ramanujam P. , Bose Salil 
Published: January 2008

AbstractDCMU‐induced stimulation of the rate of photosystem I (PS I) electron transport in DCIPH2→ MV photoreaction occurs through the action of DCMU on the rate‐limiting step which contains the site of electron donation of DCIPH2(Ramanujamet al., 1981). The magnitude of stimulation of the rate by 50 μMDCMU decreased with increasing concentration of chlorophyll (Chl), implying that DCMU is stoichiometrically related to Chl with respect to the stimulation of the PS I rate.DCMU‐induced stimulation was sensitive to the ionic condition of the thylakoids, the effect being reduced at low cation concentration. Cation‐induced scattering changes in thylakoid suspension were partially reversed by DCMU, and the percent Chl in the 10 K fraction of the thylakoid decreased upon addition of DCMU, indicating that grana structure is disrupted by DCMU. Hydroquinone‐mediated reduction of cytochromefin thylakoids in the dark was accelerated in the presence of DCMU. The DCMU effect was not observed in isolated PS I particles.It is concluded that DCMU binds to the thylakoid membranes and brings about structural changes leading to unstacking of the thylakoids accompanied by an altered interaction of the electron transfer chain components with the added electron donor. This binding of DCMU must have an affinity lower than the well‐known binding of DCMU to photosystem II (PS II), because the concentration required is markedly higher.