bluuebunny/crossref_metadata_2025 huggingface dataset:
THE EFFECTS OF LIQUID HOLDING ON NEAR‐UV(300–400 nm) IRRADIATED ESCHERICHIA COLI STRAINS DIFFERING IN NEAR AND FAR‐UV RADIATION SENSITIVITY
Authors: Tuveson R. W. , Violante Edward V.
Published: January 2008

Abstract— Stationary phase cells from four Escherichia coli strains differing in near‐ (nur vs. nur +) and far‐UV (recAl vs. recA+) radiation sensitivity were subjected to near‐UV radiation (NUV) in 0.85% saline. Although the NUV‐irradiated cultures yielded increased colony numbers following 24 h of liquid holding (LH), a fluctuation test for each experiment showed that the observed increases were not due to recovery but were in fact due to cell multiplication. The decline in viability observed after NUV with liquid holding using the fluctuation test was equivalent in strains RT2, 3 and 4 while the decline observed with RT1 was less marked. The discrepancy between LH involving cell densities of 108‐109 and 1–4 cells/m/ can be resolved by assuming that with dense cell suspensions, NUV‐induced membrane damage leads to leakage or lysis, supplying sufficient nutrients to allow growth of undamaged, surviving cells.
PHOTOVOLTAIC PROPERTIES OF MESO‐TETRAARYLPORPHYRINS
Authors: Yamashita Kazuo , Kihara Nobuo , Shimidzu Hiroaki , Suzuki Hitomi
Published: January 2008

Abstract—The photovoltaic properties ofmeso‐tetraphenylporphyrin and its derivatives with variouspara‐substituents, meso‐tetrakis(2,4‐dimethoxyphenyl)porphyrin andmeso‐tetrakis (2‐fluorenyl)porphyrin have been investigated. The forward dark current‐voltage characteristics of Al/porphyrin/Ag cells are attributed to the MIS Schottky barriers consisting of Al/Al2O3/porphyrin. The barrier parameters such as the apparent diffusion potentialV0the barrier width w0and the density of ionized impurityNare estimated by using the capacitor discharge method. The action spectra of photocurrents closely follow the optical absorption spectra of the porphyrin films. The photocurrents vary asipαIγ, whereIis the incident light intensity, and the Sight exponentsyrange between 0.83 and 1.0. The sublinear difference from unity could be related to the exponential distribution of hole traps in films of the porphyrins. No obvious correlation between the photocurrent and the fluorescence quantum yields of the sublimed porphyrin films is found. The electron donating substituents such as OCH3and CH3strikingly increase the photocurrents. The photocurrent quantum yields correlate exponentially with the first ring oxidation potentials of the porphyrins and also with the substituent constants for the Hammett linear free‐energy relationship. The current quantum yields estimated for the porphyrins studied, range in the order of 10‐4–10‐2with power conversion efficiencies 10‐7–10‐3.
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.
PHOTOTOXICITY FROM BENOXAPROFEN: IN VIVO AND IN VITRO STUDIES
Authors: Webster Guy F. , Kaidbey Kays H. , Kligman Albert M.
Published: January 2008

Abstract Benoxaprofen (2‐[4‐chlorophenyl]‐α‐methyl‐5‐benzoxazole acetic acid), a non‐steroidal antiinflammatory drug, was found to provoke phototoxicity reactions in humans. Exposure of the skin of benoxaprofen‐treated subjects to either solar simulating radiation or a broad UV‐A wavelength band produced intense itching and burning sensations, followed by the development of a classical wheal and flare response within 2‐4 min. Phototoxicity was related to both the UV radiation fluence and the dose of orally administered benoxaprofen. Wavelengths between 320 and 340nm were active in provoking urticaria. In vitro studies demonstrated that benoxaprofen and UV irradiation produced a dose‐dependent lysis of sheep erythrocytes which did not appear to be dependent on the presence of oxygen. Red cells were not lysed by pre‐irradiated benoxaprofen arguing against the production of stable lytic photoproducts. Human neutrophils were lysed by benoxaprofen and UV light which resulted in the liberation of both cytoplasmic and lysosomal enzymes. Benoxaprofen failed to induce photolysis of human platelets and photoactivation of complement in human serum. It is suggested that phototoxic urticaria provoked by benoxaprofen may be due to a direct photolytic effect on human dermal mast cells.
p‐AMINOBENZOIC ACID‐SUNLAMP SENSITIZATION OF PYRIMIDINE DIMER FORMATION AND TRANSFORMATION IN HUMAN CELLS
Authors: Sutherland Betsy M.
Published: January 2008

Abstract In the presence of sunlamp radiation, p‐aminobenzoic acid sensitizes pyrimidine dimer formation in the DNA of human skin fibroblasts. It also sensitizes the sunlamp‐induced transformation of such cells to anchorage‐independent growth.
DETERMINANTS OF HEMATOPORPHYRIN‐CATALYZED PHOTOSENSITIZATION
Authors: Kessel David
Published: January 2008

Abstract Using murine leukemia L1210 cells in culture, determinants of photosensitization by hemato‐porphyrin were examined. Cells incubated for 10 min with a commercial preparation of hematopor‐phyrin rapidly accumulated protoporphyrin and vinyl‐hydroxyethyldeuteroporphyrin present as impurities. The resulting photosensitization appears to be mainly derived from the latter product.
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.
MECHANISMS FOR DYE‐MEDIATED PHOTODYNAMIC ACTION: SINGLET OXYGEN PRODUCTION, DEOXYGUANOSINE OXIDATION AND PHAGE INACTIVATING EFFICIENCIES
Authors: Houba‐Herin N. , Calberg‐Bacq C. M. , Piette J. , Van de Vorst A.
Published: January 2008

Abstract The production of singlet oxygen (1O2) upon irradiation of several dyes in aqueous solution at pH 9.0, was quantitatively analyzed on the basis of the appearance of stable nitroxide radicals using the amine 2,2,6,6‐tetramethyl‐4‐piperidone as 1O2 acceptor. The dyes were checked for purity, their concentrations uniformized in terms of absorbance values and a correction factor was introduced which took into account the amount of photons absorbed. The rates of 1O2 production (in arbitrary units per min) were: 71 with rose Bengal, 70 with methylene blue, 61 with eosin Y, 18 with thiopyronine, 10 with proflavine and 9 with acridine yellow. Production of 1O2 was not observed with 9‐aminoacridine, acridine orange, quinacrine and ethidium bromide. Irradiated lumichrome initiated, with the same amine, another type of reaction. The rates of two other photoreactions were also determined under similar experimental conditions by following (i) the deoxyguanosine decomposition in which case the reaction was found to be less sensitive but largely parallel to the 1O2 production and (ii) the bacteriophage ØX174 inactivation in which case the dyes showed differences in their relative efficiencies. The proteinic capsid of the phage appeared as an effective impermeability barrier towards externally generated 1O2. Moreover, some of the dyes studied intercalated into the phage DNA, a process known to favor radicalar reactions.
BLEACHING OF PURPLE MEMBRANE WITH O‐SUBSTITUTED HYDROXYLAMINES
Authors: Renthal Robert , Perez Manuel N.
Published: January 2008

Abstract The retinal Schiff base of bacteriorhodopsin, in the purple membrane from Halobacterium halobium, can be cleaved by hydroxylamine in the presence of light. We have further investigated this reaction with a series of O‐substituted hydroxylamines, RONH2, where R = ‐H (HA), ‐CH3 (MHA), ‐SO3− (HAS), benzyl‐ (BHA), p‐nitrobenzyl‐ (NBHA), and pentafluorobenzyl‐ (FBHA). All except MHA caused light‐induced bleaching of the purple membrane and the chromophore could be regenerated from apomembrane and all‐trans retinal. Relative bleaching rate constants were obtained from V=QIak0X/(kr+k0X), where V= bleaching rate, Q= quantum yield, Ia = absorbed light intensity, X= hydroxylamine concentration, k0= rate constant for bleaching and kr= rate constant for return of photoexcited bacteriorhodopsin to the initial state. This equation fits the time‐, concentration‐ and intensity‐dependences of the bleaching reactions in 0.02 M phosphate, pH 7.0. The rate constants k0 relative to HA were: MHA: 0; HAS: 0.3; HA: 1.0; BHA: 1.8; FBHA: 10.1; NBHA: 10.8. The relative rate constants do not correlate with the basicity of the derivatives. Instead, the results suggest that the retinal Schiff base is near a non‐polar cavity into which an aromatic group can be inserted.
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

Pretreatment 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

The 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.
STUDIES ON PLANT BILE PIGMENTS. II. REGIOSELECTIVE PHOTOCHEMICAL AND ACID CATALYZED Z,E ISOMERIZATION OF DIHYDROBILINDIONE AS PHYTOCHROME MODEL
Authors: Kufer W. , Cmiel E. , Thümmler F. , Rüdiger W. , Schneider S. , Scheer H.
Published: January 2008

The (4 Z, 10 Z, 15E)‐2,3‐dihydrobilindione 4, along with the fully unsaturated (E, Z, Z)‐analogue 8, has been prepared from the corresponding (Z, Z, Z)‐isomer by a variation of Falk's method (Falk et aL, 1980). The photochemical and acid‐catalyzed back‐reactions have been studied by UV‐vis and 1H‐NMR spectroscopy.
THE COLORS OF FIREFLY BIOLUMINESCENCE—I. OPTIMIZATION MODEL*
Authors: Seliger H.H. , Lall† A.B. , Lloyd J.E. , Biggley W.H.
Published: January 2008

Abstract— A model is developed for the optimization of signal‐to‐noise ratio for the detection of bioluminescence by fireflies during twilight. The relative degree of optimization is derived in terms of a dimensionless ratio, a biologically effective adaptation. The numerical values of this adaptation can be used to predict the sequence of adaptations of both visual spectral sensitivities and bioluminescence spectral emissions that result in the range of colors of bioluminescence of fireflics from green through yellow. It is shown that a narrowing of visual spectral sensitivity via a screening pigment pathway in order to discriminate against green ambient light is more efficient than a shift in visual spectral sensitivity via change in the opsin photoprotein. The model predicts that the range of wavelengths for the peak intensities of bioluminescence for North American fireflies should be between 550 and 580 nm and provides the physical basis for the observations that in general dark‐active firefly species cmit green bioluminescence and twilight‐active firefly species emit yellow bioluminescence.
SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—IV. THE PHOTOLYSIS OF BENOXAPROFEN, AN ANTI‐INFLAMMATORY DRUG WITH PHOTOTOXIC PROPERTIES
Authors: Reszka Krzysztof , Chignell Colin F.
Published: January 2008

Abstract— Benoxaprofen [2‐(4‐chlorophenyl)‐α‐methyl‐5‐benzoxazole acetic acid] is an anti‐inflammatory drug that causes acute phototoxicity in many patients. Photolysis studies in organic solvents (ethanol, benzene, dimethylsulfoxide) showed that benoxaprofen underwent both Type I and Type II reactions. Irradiation of an anerobic solution of benoxaprofen in ethanol resulted in hydrogen abstraction from the solvent to yield hydroxyethyl and ethoxyl radicals. In the presence of oxygen, superoxide, singlet oxygen and hydroxyethyl radicals were detected. Photolysis of benoxaprofen in air‐saturated benzene or dimethylsulfoxide gave superoxide. However, under anerobic conditions the drug yielded a carbon‐centered radical in benzene that could not be identified. These findings suggest that both oxygen‐dependent and oxygen‐independent processes may be important in the phototoxic reactions of benoxaprofen.
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.
THE POTENCY OF SENSITIZED PHOTOHEMOLYSIS DEPENDS ON THE COMPOSITION OF THE REACTION VESSEL
Authors: Pooler John P.
Published: January 2008

Abstract— Delayed photohemolysis has been shown to vary with the composition of the reaction vessel. Human erythrocytes were illuminated in the presence of sensitizer for 1 h and examined 23 h later for percent hemolysis. Four sensitizers, two cationic and two anionic, and three types of reaction vessel were studied. The cationic sensitizers were much more effective in tissue culture treated plastic than in neutral plastic or glass. All were somewhat more effective in neutral plastic than glass. Sorption of sensitizers to reaction vessels without cells present was also studied. In some cases sorption leads to virtually complete removal of sensitizer from the reaction medium. In other cases no sorption is detectable. For the highest sorbing sensitizer total replacement of the reaction medium with sensitizer‐free solution did not decrease effectiveness, demonstrating that sorbed sensitizer is available to sensitize. The results suggest that photooxidation of the cell membrane occurs in two zones, one at the interface between vessel surface and cell surface, and the other where the membrane faces the bulk reaction medium. The relative importance of the interface may depend on the strength of sorption and the affinity of sensitizer for the cell membrane.
THE PHOTOTOXIC EFFECT OF BENOXAPROFEN AND ITS ANALOGS ON HUMAN ERYTHROCYTES AND RAT PERITONEAL MAST CELLS
Authors: Sik Robert H. , Paschall Carl S. , Chignell Colin F.
Published: January 2008

Abstract— Benoxaprofen [2‐(4‐chlorophenyl)‐α‐methyl‐5‐benzoxazoleacetic acid] is a phototoxic non‐steroidal anti‐inflammatory agent. Irradiation of human erythrocytes in the presence of benoxaprofen (8 μM) and oxygen resulted in rapid cell lysis which began after 10 min and was complete within 30 min. While photohemolysis was also observed under anerobic conditions, its onset was delayed for more than 20 min and it took nearly 100 min for complete lysis to occur. Photohemolysis was also delayed by butylated hydroxyanisole but was unaffected by reduced glutathione. 1,4‐diazabicyclo[2.2.2]octane, D2O. β‐carotene, or superoxide dismutase. The main photoproduct of benoxaprofen, 2‐(4‐chlorophenyl)‐5‐ethylbenzoxazole, was almost as effective in causing photohemolysis as benoxaprofen itself. In the presence of UV irradiation, benoxaprofen (10 (μM) caused the degranulation of rat peritoneal mast cells and the release of histamine. The release of mast cell histamine may provide a reasonable explanation for the urticarial response to benoxaprofen and irradiation seen in human subjects.
PHOTOCONTROL OF HYPOCOTYL ELONGATION IN DE‐ETIOLATED Cucumis sativus L. A BLUE‐LIGHT‐INDUCED POST‐ILLUMINATION BURST OF GROWTH
Authors: Gaba V. , Black M.
Published: January 2008

Abstract— A rapid transient increase in the growth rate of Cucumis sativus L. seedlings is found to occur after a transition from fluorescent white light to darkness. The post‐illumination burst of growth starts after about 20 min of darkness and lasts for 30 to 50 min. The response occurs after long periods of continuous white light, in cycles of white light and darkness, whether the cotyledons are covered or exposed. The post‐illumination burst is an expression of the loss of photocontrol of hypocotyl inhibition via the specific blue light photoreceptor because (a) its kinetics resemble those of recovery from blue‐light inhibition, and (b) it only occurs on transition from a blue‐rich to a blue‐poor light environment.
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.
RIBOFLAVIN SENSITIZED PHOTOREDUCTION OF NITRO BLUE TETRAZOLIUM ION (NBT2+) IN DEGASSED AQUEOUS SOLUTION
Authors: Takakubo M. , Faure J.
Published: January 2008

Abstract— When sensitized by riboflavin, the reduction of NBT2+ (nitro blue tetrazolium ion) takes place in both aerated and degassed aqueous solution. Laser photolysis experiments revealed that the triplet riboflavin reduces NBT2+ to nitro blue tetrazolinyl radical, NBT2+. and it disappears according to pseudo‐first order kinetics, with a bimolecular rate constant of (4.2 ± 0.2) X 108M‐1s‐1. It is shown that NBT2+ is not always a good detecting reagent for the superoxide anion, when the formation of the anion is mediated by riboflavin.
LIGHT DRIVEN TRANSPORT OF BILIRUBIN THROUGH A BULK LIQUID MEMBRANE
Authors: Eichinger D. , Falk H. , Sobczak R.
Published: January 2008

Abstract— Hexadecyltrimethylammonium bromide was used as a carrier in a bulk liquid membrane to construct a model system for the rapid excretion of bilirubin during phototherapy of jaundice. When bilirubin in the donor phase was irradiated its transport through the bulk membrane increased by about two orders of magnitude compared to the dark. As production of the photodiastereomers of bilirubin and their thermal reversion are fast processes compared to the carrier mediated transport, active transport against a bilirubin concentration gradient driven by the photoisomerisation reaction is observed. The kinetics of this novel transport system is discussed and approximated by a recursion algorithm.
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.
THE EFFECT OF pH ON THE ABSORPTION AND FLUORESCENCE SPECTRA OF SANGUINARINE
Authors: Maiti M. , Nandi R. , Chaudhuri K.
Published: January 2008

Abstract— The influence of pH in the range 1.0 to 13.0 on the structure of sanguinarine has been investigated by spectrophotometric and spectrofluorimetric measurements. The data on absorption maxima, molar extinction coefficient, fluorescence emission maxima, relative fluorescence intensity and fluorescence quantum yield of the sanguinarine under various pH are presented. It is suggested that the pH dependent absorbance and fluorescence property of sanguinarine is due to the formation of the carbinolamine by hydroxylation at C‐6 at alkaline pH.
BINDING OF ANTHRACENE TO CELLULAR MACROMOLECULES IN THE PRESENCE OF LIGHT
Authors: Sinha Birandra Kumar , Chignell Colin F.
Published: January 2008

Ultraviolet 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

Clinical 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

DCMU‐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.
PHOTOMOVEMENT IN AN “EYELESS” MUTANT OF Chlamydomonas
Authors: Morel‐Laurens N. M. L. , Feinleib M. E.
Published: January 2008

The function of the stigma (“eyespot”) in the green flagellate Chlamydomonas reinhardtii was investigated by comparing the photomovement of the wild‐type alga with that of an “eyeless” mutant (ey 627). Movements of individual cells in response to a blue‐green stimulus light were recorded using a videomicroscope system and were analyzed using vectorial methods. Cells of the “eyeless” mutant were phototactic; at a high stimulus fluence rate, their swimming paths were directed away from the light source. Although the orientation of the mutant was not as strongly directional as that of the wild type, it was statistically significant. However, the swimming paths of the mutant cells were very erratic in the presence of the stimulus beam, undergoing frequent changes of direction. Despite the differences in their phototactic orientation, cells of mutant and wild type all showed a distinct step‐up photophobic response at the onset of stimulation. These results are consistent with the hypothesis that the stigma plays an accessory role in phototaxis, either by shading the photoreceptor or by acting as a quarter‐wave reflector.
THE CHLOROPHYLL‐SENSITIZED REACTION BETWEEN BENZOQUINONE AND ETHANOL*
Authors: Seely G. R. , Rutkoski A. M. , Shaw E. R.
Published: January 2008

The electron‐transfer reaction between triplet excited chlorophyll and quinones has been extensively studied as a model of the primary reaction in photosystem II. There has also been reported a minor reaction in which the chlorophyll cation radical ostensibly oxidizes the alcohol solvent or even water, leading to a gradual net reduction of quinone, but the exact mechanism and even the existence of this reaction has been uncertain. We have examined the consequences of prolonged irradation of ethyl chlorophyllide and benzoquinone in acidulated ethanol, and find a chlorophyllide‐sensitized reaction which is not analogous to the better‐known autosensitized reduction of quinones in blue or UV light. In the chlorophyllide‐sensitized reaction, benzoquinone is apparently converted to ethoxy‐substituted quinones and quinols, and polymeric material. Ethyl chlorophyllide (or chlorophyll) is simultaneously oxidized to more polar products which themselves continue to photosensitize the reaction of quinones. The production of acetaldehyde could not be demonstrated in the sensitized reaction. Chlorophyllide‐sensitized reaction of (l‐hydroxyethyl)benzoquinone, ethoxybenzoquinone and 2.5‐diethoxybenzo‐quinone were examined for additional information. A reaction sequence, tentatively proposed to accommodate the known facts, starts with oxidative attack by quinone on an oxidized chlorophyllide radical formed by loss of a hydroxyl proton from alcohol bound as a ligand to Mg2+. It is not likely that this reaction is closely related to events at the oxidizing side of photosystem II.
OXIDATION‐REDUCTION AND EPR PROPERTIES OF A CYTOCHROME COMPLEX FROM Chromatium vinosum
Authors: Knaff David B. , Kraichoke Saran
Published: January 2008

A cytochrome b560‐c553 containing fraction from the photosynthetic purple sulfur bacterium Chromatium vinosum has been shown to contain equimolar amounts of the two cytochromes and also to contain ubiquinone. The oxidation‐reduction midpoints (at pH 7.5) of cytochrome b560 and c553 in this fraction are −5 and +20 mV, respectively, essentially identical to the values found for the cytochromes in chromatophores. The fully oxidized fraction exhibits EPR features at g = 2.93 and 3.35. The former had previously been identified as originating from ferricytochrome c553, while the latter appears to arise from ferricytochrome bS60.
SPECTRAL STUDY OF THE PHOTOCHEMISTRY OF DIPYRROLE MODELS FOR BILIRUBIN BOUND TO HUMAN SERUM ALBUMIN
Authors: Lamola Angelo A. , Braslavsky Silvia E. , Schaffner Kurt , Lightner David A.
Published: January 2008

—Dipyrromethenones, which include xanthobilirubinic acid (I), its methyl ester (II) and the endo‐vinyl analog of neoxanthobilirubinic acid methyl ester (“half bilirubin” methyl ester) (III) bind to human serum albumin (HSA) and thereby exhibit greatly increased fluorescence as well as induced circular dichroism in their long wavelength transitions. As determined from fluorescence studies, the “tightness” of the binding to HSA is, inter alia, inversely related to the inherent solubility of the dipyrromethenone in aqueous buffer. Fast (ps) configurational isomerization (Z→E) is the major pathway for decay of the first excited (singlet) states of the HSA‐bound dipyrromethenones. A quantum yield of − 0.4 is associated with the Z→E isomerization. Binding to HSA enhances the lifetimes of the less thermodynamically stable E‐isomers. The results of these studies of “half bilirubins” allow a clear evaluation of the effects of protein binding upon the photophysics and photochemistry of bilirubin.
PHOTOSENSITIZATION OF METHYL LINOLEATE OXIDATION BY TRYPTOPHAN IN PEPTIDES
Authors: Kochevar Irene E. , Yoon Minjoong
Published: January 2008

The ability of tryptophan in peptides to photosensitize the oxidation of methyl linoleate (ML) was evaluated. Purified ML was irradiated (λ > 270 nm) alone or in the presence of a tryptophan‐containing peptide in ethanol solution. Oxidation was monitored by measuring the dienc hydroperoxides formed from ML by high performance liquid chromatography. N‐acetylphenylalanyltryptophan (NAPT) and N‐acetyltryptophan were about 2‐fold more effective as photosensitizers than leucyltryptophan and tryptophylleucine. N‐acetylphenylalanyltryptophan photolyzed in ethanol to form multiple photoproducts including N‐formylkynurenine‐type compounds. However, the NAPT photoproducts did not photosensitize the oxidation of ML and N‐formylkynurenine was about 8% as effective as NAPT. Sodium azide partially quenched the photooxidation sensitized by NAPT.
AN ACTION SPECTRUM FOR ULTRAVIOLET RADIATION‐INDUCED MEMBRANE DAMAGE IN Escherichia coli K‐12
Authors: Kelland L. R. , Moss S. H. , Davies D. J. G.
Published: January 2008

A wild‐type Escherichia coli K‐12 strain was irradiated using monochromatic radiation in the range 254 to 405 nm. A measure of the cell membrane damage induced at each wavelength was investigated by comparing cell viability after irradiation on nutrient agar and on minimal medium containing either a low or high inorganic salt concentration. An action spectrum for lethality and for cell membrane damage was then determined. From 254 to 310 nm lethality closely corresponded to the absorption spectrum of DNA, and there was no indication of membrane damage. However, above a wavelength of 310 nm, the direct absorption of radiation by DNA could not account for the sensitivity observed. Moreover, at wavelengths longer than 310 nm, cell membrane damage was induced and by an increasing factor up to a peak at 334 nm. At the longer wavelengths of 365 and 405 nm, there was a gradual decrease from the peak of damage to cell membranes induced by 334 nm radiation. These results indicate that cell membrane damage may contribute significantly to near‐UV radiation‐induced cell lethality in wild‐type E. coli K‐12.
REPAIR OF ULTRAVIOLET‐IRRADIATED TRANSFORMING DNA IN A recA MUTANT OF Haemophilus influenzae
Authors: Stuy Johan H. , Walter Ronald B.
Published: January 2008

—Ultraviolet‐irradiated transforming DNA was assayed on a wild‐type strain of Haemophilus influenzae strain Rd, on an excision repair‐deficient (uvr‐2) mutant, on a recombination repair‐deficient (recA4) mutant, and on a strain carrying both mutations. The donor DNA had a point mutation genetic marker (strAl) and a long nonhomologous plasmid‐derived DNA segment inserted in the HP1 prophage. The shape of the inactivation curves suggested that only recombination was responsible for the inverse square root kinetics observed with excision repair‐proficient recipients.
STATE I‐STATE II TRANSITIONS IN THE THERMOPHILIC BLUE‐GREEN ALGA (CYANOBACTERIUM)Synechococcus lividus*
Authors: Fork David C. , Satoh Kazuhiko
Published: January 2008

Time courses of state I‐state II transitions were measured in the thermophilic blue‐green alga (Cyanobacterium),Synechococcus lividus, that was grown at 55°C. The rate of the state I–II transition using light II illumination was the same as that in the dark, and the dark state was identified to be state II. Therefore, light regulation attained by state transitions is produced by the state II–I transition induced by system I light. The redox level of plastoquinone did not affect this dark state II.

Arrhenius plots of the state transitions showed a break point around 43°C that corresponded to the phase transition temperature of this alga. Since both the state I–II and II–I transitions were very much temperature‐independent, we could keep the alga in either state for a long time at a “low” temperature such as room temperature.

Activities of both photosystems I and II in states I and II were also measured. After a state II–I transition, the system II activity increased about 16% and at the same time, svstem I activity decreased about 30%.
FORMATION OF 5‐HYDROXYMETHYLCYTOSINE‐CONTAINING PYRIMIDINE DIMERS IN UV‐IRRADIATED BACTERIOPHAGE T4 DNA
Authors: Childs John D. , Ellison Michael J. , Pilon Raymond
Published: January 2008

Cyclobutyl pyrimidine dimers composed of 5‐hydroxymethylcytosine and thymine (5HMC><T) increased from 0.07 at 254 nm to a maximum of 0.41 at 313 nm and then declined to 0.26 at 320 nm. These relative yields are 3‐10‐fold lower than the corresponding yields of cytosine‐thymine dimer relative to T><T dimer appears to be 4 times higher than that of a T<>T dimer for a mutant of T4 (denV) that is unable to excise pyrimidine dimers from its DNA. The ability of 5HMC to form dimers suggests that other modified pyrimidines such as 5‐methylcytosine can participate in dimer formation, particularly at the UV wavelengths in sunlight likely to be responsible for the induction of skin cancer.
COMPARISON OF THE ERYTHEMOGENIC EFFECTIVENESS OF ULTRA VIOLET‐B (290‐320 nm) and ULTRA VIOLET‐A (320‐400 nm) RADIATION BY SKIN REFLECTANCE
Authors: Wan San , Jaenickeand KurtF. , Parrish JohnA.
Published: January 2008

–Based on optical properties of the skin, its constituent layers and the blood, and a previously experimentally verified quantitative model for the optical transfer properties in skin, noninvasive determinations of the amount of cutaneous blood in the superficial plexus are made from skin reflectance. This method is used to determine UVA and UVB fluences that cause cutaneous blood in the superficial plexus to increase to 1.5, 2 and 2.5 times the pre‐radiation volume at various times after irradiation. Our results show that on an equal fluence basis, UVB is two to three thousand times as effective as UVA in inducing erythema, whether erythema is evaluated 8, 24 or 72 h after irradiation. This agrees with the result obtained in terms of minimal erythema dose by visual inspection.
PROTOPORPHYRIN‐INDUCED PHOTODAMAGE: STUDIES USING CULTURED SKIN FIBROBLASTS
Authors: Latham Patricia S. , Bloomer Joseph R.
Published: January 2008

A new system is described for the study of protoporphyrin‐induced photodamage of cells. This system differs from those previously described in that fibroblasts are induced to synthesize protoporphyrin from its precursor δ‐aminolevulinic acid.

Fibroblasts were cultured from skin biopsies of 6 normal individuals and 6 patients with protoporphyria. All cell lines in both groups accumulated protoporphyrin when incubated with δ‐aminolevulinic acid in the absence of iron. Irradiation for 2 min with long‐wave UV light caused death of cells which had accumulated protoporphyrin, but not of cells which had been incubated without δ‐aminolevulinic acid. Cell damage could be quantitatively assessed by the release of chromium‐51 into the medium.

Examination of irradiated protoporphyrin‐rich fibroblasts by electron microscopy revealed no significant differences between lines from patients with protoporphyria and normal individuals. The earliest indications of photodamage were rarifaction of the mitochondrial matrix with dilatation of cristae. dilatation of endoplasmic reticulum, and loss of plasma membrance integrity. Condensation of the cells correlated with cell death. These structural alterations suggest a generalized cellular injury.
PHOTOSENSORY BEHAVIOR OF A BACTERIORHODOPSIN‐DEFICIENT MUTANT, ET‐15, OFHalobacterium halobium
Authors: Hildebrand Eilo , Schimz Angelika
Published: January 2008

–Halobacterium halobium, strain ET‐15, which does not contain detectable amounts of bacteriorhodopsin (BR) shows behavioral responses to UV and yellow‐green light. Attractant stimuli. i.e. light‐increases in the yellow‐green range or light‐decreases in the UV, suppress the spontaneous reversals of the swimming direction for a certain time. Repellent stimuli, i.e. light‐decreases in the yellow‐green range or light‐increases in the UV, elicit an additional reversal response after a few seconds. Action spectra of both sensory photosystems, PS 370 and PS 565, were measured with attractant as well as with repellent stimuli. As in BR‐containing cells, maximal sensitivity was always found at 370 nm for the UV‐system and at 565 nm for the long‐wavelength system. Fluence‐response curves at 370 and 565 nm obtained with strain ET‐15 and with a BR‐containing strain show that the sensitivity of both photosystems is not reduced in the absence of BR. It is concluded that BR is required neither for PS 565 nor for PS 370. Instead retinal‐containing pigments different from BR have to be assumed to mediate photosensory behavior.
PHOTODYNAMIC EFFECTS ON CELLSIN VITROEXPOSED TO HEMATOPORPHYRIN DERIVATIVE and LIGHT
Authors: Moan Johan , McGhie James , Jacobsen Petter Balke
Published: January 2008

AbstractSeveral effects of hematoporphyrin derivative (HpD) and light on NHIK 3025 cellsin vitrowere studied. The treatment resulted in a partly repairable reduction of the rate of thymidine incorporation into DNA, a division delay, a reduced rate of protein synthesis, a reduced rate of active cellular uptake of α‐aminoisobutyrate, a reduction in the colony‐forming ability and an increased permeability of the cell membrane to chromate. Thymidine incorporation was by far the most sensitive parameter studied. However, comparison of the photodynamic effects after 1 and 18 h incubation with HpD prior to irradiation indicated that neither the reduced rate of DNA synthesis nor any of the other observed effects was the main primary cause of cell inactivation under all conditions. Several of the effects, such as increased permeability of the cell membrane to chromate, reduction in the rate of protein synthesis and reduction in the rate of repair of the damage to the mechanism of DNA synthesis, were clearly of secondary nature. When seen in relation to cellular survival, membrane damage was more important after short incubation times with HpD than after long incubation times.
SPECTRAL CHARACTERIZATION OF LIGHT‐REDUCIBLE CYTOCHROME IN A PLASMA MEMBRANE‐ENRICHED FRACTION AND IN OTHER MEMBRANES FROM CAULIFLOWER INFLORESCENCES
Authors: Widell S. , Caubergs R. J. , Larsson C.
Published: January 2008

Abstract— Low temperature spectroscopy has been used to characterize microsomal fractions obtained from cauliflower inflorescences (Brasska oleracea L.) by differential centrifugation and partition in an aqueous polymer two‐phase system. The plasma membrane‐enriched fraction (U3) was found to contain one dominant b‐cytochrome, which could be reduced both by blue light and by dithionite. An action spectrum of the blue light‐induced absorbance change [LIAC, Δ(A430—A410)] associated with the reversible reduction of this b‐type cytochrome indicated that the primary light‐receptor was a flavin‐like compound. Another microsomal fraction (L3) containing membranes from mitochondria, endoplasmic reticulum and other organelles also contained light‐reducible cytochrome. One of these could be identified as cytochrome c oxidase, and another may be identical to cytochrome b5 of the endoplasmic reticulum.