bluuebunny/crossref_metadata_2025_split huggingface dataset:
PHOTOSENSITIZATION OF PYRIMIDINES BY 2‐METHYLNAPHTHOQUINONE IN WATER: A LASER FLASH PHOTOLYSIS STUDY
Authors: Fisher Gordon J. , Land Edward J. 
Published: January 2008

Abstract2‐Methylnaphthoquinone (MQ) has been excited in water with a 20 ns laser flash at 353 nm and the resultant transient species have been observed optically. Triplet‐state MQ (3MQ) decays on a sub‐microsecond time scale. It has been characterized in terms of its absorption spectrum and quantum yield. Rate constants have been measured for the decay of3MQ in infinitely dilute solution, for self‐quenching by ground‐state MQ, and for reactions of3MQ with oxygen, thymine, uracil, 6‐methyluracil, and orotic acid. The interaction of3MQ with pyrimidines involves charge transfer to give the pyrimidine cation radical and the MQ : anion radical. These reactions are discussed in relation to the mechanism of pyrimidine photooxidation sensitized by MQ.
DOSE‐TIME DEPENDENCY OF TUMOR FORMATION BY CHRONIC UV EXPOSURE
Authors: R.DeGruijl F. , Der Meer J.B. Van , Der Leun J. C. Van 
Published: January 2008

Abstract‐An animal experiment is presented which involved a total of 223 albino hairless mice (Skh hr 1). These mice, excluding 24 of them which served as controls, were divided over 6 groups, each of which received a different but constant daily dose of UV radiation from fluorescent sunlamps (Westinghouse FS40TL12). The range of daily doses encompassed a factor of 33. Data on the response of each group as a whole are presented. The group responses are measured in two ways: (1) the proportion of tumor bearing mice (prevalence), and (2) the average number of tumors per survivor (yield). The data provide information on the variation of the group response with time, daily dose and tumor size.The relationship between the daily dose and the duration of the treatment till 50% of the mice have tumors is given for several sizes of tumors. From these results, and from direct measurements of tumor growth, it appears that the growth of tumors is virtually dose‐independent and, in consequence, only the initiation of tumors is dose‐dependent. This implies that the theoretical model of UV‐tumorigenesis presented by Blum (1959). based on UV‐accelerated growth, is incorrect. It is pointed out that, in similarity to chemo‐ and radiotumorigenesis, the total dose delivered to a mouse for the induction of tumors has to be higher if a high daily dose is used than if a low daily dose is used. It seems as though an animal becomes more resistant to the UV‐stimuius as the rate at which the stimulus is presented is increased: an adaptive phenomenon.
ENERGY‐REGULATED FUNCTIONAL TRANSITIONS OF CHLOROPLAST ATPASE
Authors: Schuurmans J. J. , Kraayenhof R. 
Published: January 2008

AbstractThe functional transitions of the membrane‐bound chloroplast ATPase (CF1) as influenced by low ADP and uncoupler concentrations are investigated by measurements of initial and steady‐state ATP hyrolysis and concomitant membrane energization. Following activation of latent ATP hydrolysis by light in the presence of dithioerythritol, the resulting steady‐state ATP hydrolysis depends on the dark‐period (td) bteween light activation and ATP addition. ADP, added during td, inhibits this activity (Ki about 2 μM) and induces a lag in the onset of ATP hydrolysis. The extent of membrane energization as monitored by an aminoacridine fluorescent probe is proportional to the ATPase activity.An uncoupler amplifies the inhibitory effect of ADP if added during fd, whereas it induces the normal stimulation of ATP hydrolysis in the absence of ADP. The ADP effect, which is different from product inhibition, is interpreted as a conformational interaction with CF1 causing an increase of the energy threshold required for the inactive → active transition of the CF1 molecules. These results are in harmony with currently proposed models of CF1 regulation by adenine nucleotides based on binding studies.The inactive → active transition of CF1 conformation is investigated by analysis of the lag in the onset of ATP hydrolysis at different ADP concentrations and by means of varied light pulses and single‐turnover flashes, using the electric potential indicating absorption change at 515 nm as a probe for the onset of ATP hydrolysis. The half‐time of the process leading to fully (re)activated ATP hydrolysis is about 0.25 s. The ATP‐dependent flash‐induced inactive → active transition occurs within a few turnovers of electron flow.
TIME RESOLVED STUDIES OF 1.27 μm LUMINESCENCE FROM SINGLET OXYGEN GENERATED IN HOMOGENEOUS and MICROHETEROGENEOUS FLUIDS
Authors: Rodgers Michael A. J. 
Published: January 2008

Abstract‐The luminescence at 1.27 μm from the 3→→1δg transition of the oxygen molecule has been detected from a variety of liquid systems. A Q‐switched laser delivering pulses of 532 nm light was the excitation source, a germanium photodiode was the detector and substituted porphyrins were used as photosensitizers. Protio‐ and deutero‐ forms of several solvents were studied and the singlet oxygen lifetimes determined directly agreed well with published values. Tδ in D2O was found to be 55 μs and, by extrapolation from a series of H2O ‐ D2O mixtures, a value of 3.3 μs was obtained for Tδ in H2O. The technique was shown to be useful in measuring Tδ values in several microheterogeneous systems such as surfactant micelles, vesicles and human serum albumin.
QUENCHING AND PHOTOBLEACHING OF EXCITED POLYCYCLIC AROMATIC HYDROCARBONS BY CARBON TETRACHLORIDE AND CHLOROFORM IN MICELLAR SYSTEMS
Authors: Encinas María V. , Rubio María A. , Lissi Eduardo 
Published: January 2008

Abstract—Aromatic hydrocarbons incorporated into cetyltrimethylammonium chloride (CTACl) or sodium dodecylsulphate (SDS) micelles are efficiently quenched and photobleached by carbon tetrachloride. Similar results were obtained employing chloroform, but the efficiency of this compound as a quencher is nearly 103 times smaller than that of carbon tetrachloride.Bimolecular quenching constants, with the quencher concentration given in moles per liter of micellar pseudophase, have been evaluated and compared with those obtained in homogeneous solutions. For slow processes, the values obtained would indicate that the polarity sensed by the probe depends both upon the probe and the surfactant. For diffusionally controlled processes (i.e. quenching of biphenyl), bimolecular quenching constants are considerably smaller in the micellar pseudophase. For these processes the pseudo‐first‐order quenching rate constants are larger in SDS than in CTACl micelles. This effect is partly due to the smaller size of the SDS micelle but also is a consequence of a lower “microviscosity” of these micelles.
FLUORESCENCE DECAY OF THE ACRIDINE ORANGE‐SODIUM DODECYL SULFATE SYSTEM: FORMATION OF DYE‐RICH INDUCED MICELLES IN THE PREMICELLAR REGION*
Authors: Ban Taketora , Kasatani Kazuo , Kawasaki Masahiro , Sato Hiroyasu 
Published: January 2008

AbstractThe fluorescence decay behavior was studied for the acridine orange (AO)‐sodium dodecyl sulfate (SDS) system in order to investigate the nature of the dye‐detergent interaction, especially in the premicellar region, i.e. below the critical micelle concentration (cmc). The fluorescence spectra and decay behavior were found to depend on [AO] and [SDS]. An exponential fluorescence decay with a lifetime of 3‐4 ns was found for large [SDS]s together with a fluorescence band at 545 nm and the monomer‐type absorption spectrum. This can be attributed to the monomer dye associated with micelles. For smaller [SDS]s where the fluorescence band at 640 nm appeared together with a dimer band in absorption spectra, slower fluorescence decays were observed when we probed the long‐wavelength region (λobs > 620 nm). These decays can be attributed to the dimer of the dye associated with micelles. The presence of this slower decay below the cmc directly proves the presence of dye‐rich induced micelles. The distribution of dye molecules among the dye‐rich induced micelles is discussed assuming that the same fluorescence behavior is the consequence of the same distribution of dye molecules among micelles (above the cmc) or among dye‐rich induced micelles (below the cmc).
SYNTHETIC MODELS RELATED TO DNA‐INTERCALATING MOLECULES. INTERACTIONS BETWEEN 8‐ALKOXYPSORALEN AND ADENINE*
Authors: Decout Jean Luc , Lhomme Jean 
Published: January 2008

AbstractTo investigate the interactions and the photoreactions between furocoumarins and adenine, we have synthesised compounds in which a psoralen molecule is linked by different polymethylene bridges to adenine. Ring‐ring intramolecular interactions are observed by UV spectroscopy. Thermodynamic parameters of these hydrophobic interactions are determined by the study of the variation of the hypochromic effect with temperature.
QUANTUM YIELD OF SINGLET OXYGEN PRODUCTION BY XANTHENE DERIVATIVES
Authors: Gandin E. , Lion Y. , Van de Vorst A. 
Published: January 2008

AbstractThe singlet oxygen quantum yield (ϕ1o2) of 11 purified fluorescein derivatives was determined by reaction with singlet oxygen acceptors in aqueous and ethanolic solutions; in both solvents ϕ1o2 was enhanced with increasing halogenation. Tryptophan and 2,2,6,6‐tetramethylpiperidone were found to be unadapted for the determination of ϕ1o2, in our systems; however, the use of 9.10‐dipropionic anthracene acid andp‐nitrosodimethylaniline in conjunction with imidazole derivatives was suitable for 1O2 detection in water. Both methods lead to results in excellent agreement. As in ethanol. ϕ1o2, was equal to the triplet state quantum yield (ϕT), the comparison between the two solvents showed that ϕT in water was greater than in ethanol. The comparison between our values obtained with polychromatic light with published data obtained with monochromatic light suggests that the triplet quantum yield of fluorescein derivatives is wavelength independent.
GROWTH DEPENDENT LUMINESCENCE FROM CULTURES OF NORMAL and RESPIRATORY DEFICIENT SACCHAROMYCES CEREVISIAE
Authors: Quickenden T. I. , Tilbury R. N. 
Published: January 2008

Abstract—Luminescence was detected from oxygenated, liquid cultures of the yeast Saccharomyces cerevisiae with a photon counter sensitive between 200 and 600 nm. Four periods of emission were observed: (1) during the late exponential phase (137 ± 6 counts s−1); (2) during the early stationary phase (118 ± 24 counts s−1); (3) during the late stationary phase (ca. 1000 counts s−1); and (4) during the very late stationary phase (ca. 1000 counts s−1). Emissions (3) and (4) have not been previously reported. Experiments in which the yeast was temporarily separated from the nutrient medium suggested that all of the luminescences arose from within the yeast cell. Respiratory deficient (“petite”) mutants of S. cerevisiae gave similar emissions, except that the first and third emission peaks were more intense and an early shoulder appeared on the first peak. All of the emissions from normal and “petite” cultures disappeared when the yeast was grown anaerobically. It was concluded that the luminescences do not arise from any of the reactions in the fermentative and respiratory pathways and that O−2, may be involved in the processes leading to emission.
BEHAVIORAL RESPONSES IN Paramecium multimicronucleatum TO VISIBLE LIGHT
Authors: Iwatsuki Kenji , Naitoh Yutaka 
Published: January 2008

AbstractSpecimens of colorless Paramecium multimicronucleatum were found to respond to visible light. They accumulated in the shaded region (photodispersal) of a half‐shaded glass tube during 2 min exposure to visible light. The specimens showed avoiding reaction upon both spatial and temporal increase in light intensity (step‐up photophobic response). Steady‐state swimming velocity (orthokinesis) was higher, while steady‐state frequency of spontaneous change in swimming direction (klinokinesis) was lower when the light intensity was kept higher. In a light with wavelength of 440 nm the velocity was highest, while the frequency was lowest. The specimens did not show phototaxis (light direction‐oriented locomotion). Spectral sensitivity curves for both the photodispersal and the step‐up photophobic response showed a major peak at 520 nm and a minor peak at 680 nm. The photodispersal seems to be caused mainly by the step‐up photophobic response exhibited by the specimens at the dark‐light border. The photokinetic responses enhance the degree of the photodispersal.
STIMULATION OF BIOLUMINESCENCE IN DINOFLAGELLATES BY RED LIGHT*
Authors: Sweeney Beatrice M. , Fork David C. , Satoh Kazuhiko 
Published: January 2008

AbstractIn three species of dinoflagellate, Gonyaulax polyedra, Pyrocyslis fusiformis and Pyrocvstis lunula, bioluminescence can be stimulated by light. This phenomenon is observed if the cell suspension is rendered anaerobic by any of the following treatments: N2gas. metabolically active yeast. glucose plus glucose oxidase, dithionite or allowing a concentrated cell suspension to stand for several hours in darkness, conditions which remove oxygen from the cell suspension. An alternate pretreatment is inclusion of carbonylcyanide‐m‐chlorophenyl hydrazone or hydroxylamine in the cell suspension. The emission spectrum with a maximum at 478 nm identifies dinoflagellate luciferin as the emitter. The action spectrum (maximum at 675 nm in the red region of the spectrum) points to chlorophyll as the photoreceptor. Evidence for the participation of PS II of photosynthesis in the light‐stimulation of bioluminescence is the strong inhibition of light emission by 3‐(3.4‐dichlorophenyl)‐l.l‐dimethylurca (DCMU) and 2,5‐dibromo‐3‐isopropyl‐p‐benzoquinone and the failure of diaminodurol + ascorbate to reverse the inhibition by DCMU. The observation that, with short irradiations (5 μ.s). no bioluminescence is emitted until the third flash also suggests photosystem II (PS II) as the site of stimulation. The evolution of oxygen is not involved in the light‐stimulation of bioluminescence. since oxygen evolution is completely inhibited by NH2OH, while light emission is potentiated by the presence of NH2OH. A consideration of the action of inhibitors suggests that the stimulation of light emission is the result of a change in membrane potential produced upon irradiation of PS II. This membrane potential is not caused by the movement of protons.
HOST CELL REACTIVATION BY FIBROBLASTS FROM PATIENTS WITH PIGMENTARY DEGENERATION OF THE RETINA
Authors: DavidLytle C. , Tarone RobertE. , Barrett SusannaF. , Wirtschafter JonathanD. , Dupuy Jean‐Marie , Robbins JayH. 
Published: January 2008

Abstract–Cockayne syndrome (CS) is an autosomal recessive disease characterized by numerous clinical abnormalities including acute sun sensitivity and primary pigmentary degeneration of the retina. Cultured fibroblasts from CS patients are hypersensitive to ultraviolet (UV) radiation. Since host cell reactivation of irradiated virus is a useful probe to evaluate repair in different host cells, we studied such host cell reactivation in CS and in other diseases with retinal degeneration. The survival of UV‐irradiated Herpes simplex virus type 1 was determined in fibroblast lines from four normal donors. two patients with CS, one with both xeroderma pigmentosum (XP) and CS, and from several other patients with (Usher syndrome, olivopontocerebellar atrophy, retinitis pigmentosa) and without (XP, ataxia telangiectasia) primary pigmentary degeneration of the retina. The viral survival curves (log survival vs linear fluence) in all cell lines showed two components: a very sensitive initial component (not quantitated in this study) followed by an exponential, less sensitive component. The exponential component had greater sensitivity than normal in the case of the CS patients, the patient with both XP and CS. and the XP patient. We propose that patients with CS have defective repair of DNA which may be the cause of their retinal degeneration.
TRANSMISSION OF UV‐RADIATION THROUGH HUMAN EPIDERMAL LAYERS AS A FACTOR INFLUENCING THE MINIMAL ERYTHEMA DOSE
Authors: BRULS WIEL A. G. , VAN WEELDEN HUIB , VAN DER LEUN JAN C. 
Published: January 2008

Abstract— The extent to which transmission of human Caucasian epidermis and stratum corneum influences the Minimal Erythema Dose (MED) was examined for UV‐B and UV‐C.Transmission correlated well with variations in MED for UV‐B and UV‐C that exist between individuals, as measured on the skin of the lower back and anterior upper leg.Regional differences of the MED that occur within the same individual between different parts of the body, were related less well to differences in transmission. For UV‐B, the difference in transmission of stratum corneum and epidermis between upper leg and lower back was on the average too small to completely account for the difference in MED UV‐B. Other parameters, therefore, have to be involved in determining such regional variations in MED UV‐B. For UV‐C, on average, the difference in transmission of stratum corneum was smaller and of epidermis larger than the difference in MED UV‐C between upper leg and lower back, though the deviations were not significant.A series of UV‐B irradiations of the lower back resulted in an increase in MED UV‐B and MED UV‐C, which was paralleled by a decrease in transmission of stratum corneum and epidermis. The average decrease in UV‐B transmission of stratum corneum was too small and that of epidermis somewhat too large to account for the average increase in MED UV‐B. The average decrease in UV‐C transmission of stratum corneum was about as large as the average increase in MED UV‐C. Consequences of these observations for the location of the primary reactions leading to erythema are discussed.The relationship between log MED UV‐C and log MED UV‐B was confirmed to be approximately linear.
PHOTOCHEMICAL ADDITION OF AMINO ACIDS AND PEPTIDES TO HOMOPOLYRIBONUCLEOTIDES OF THE MAJOR DNA BASES
Authors: SHETLAR MARTIN D. , HOM KELLIE , CARBONE JOHN , MOY DAVID , STEADY ELAINE , WATANABE MARK 
Published: January 2008

Abstract— The photochemical quantum yields for addition of glycine and the L‐amino acids commonly occurring in proteins (excluding proline) to polyadenylic acid, polycytidylic acid, polyguanylic acid and polyribothymidylic acid have been determined in deoxygenated phosphate buffer at Λ 254 nm and pH 7, using a fluorescamine assay technique. Polyadenylic acid was reactive with eleven of the twenty amino acids tested, with phenylalanine, tyrosine, glutamine, lysine and asparagine having the highest quantum yields. Polyguanylic acid reacted with sixteen amino acids; phenylalanine, arginine, cysteine, tyrosine, and lysine displayed the largest quantum yields. Polycytidylic acid showed reactivity with fifteen amino acids with lysine, phenylalanine, cysteine, tyrosine and arginine having the greatest quantum yields. Polyribothymidylic acid, reactive with fifteen of nineteen amino acids surveyed, showed the highest quantum yields for cysteine, phenylalanine, tyrosine, lysine and asparagine. None of the polynucleotides were reactive with aspartic acid or glutamic acid.The quantum yields for photoaddition of eighteen dipeptides of the form glycyl X (X being one of the amino acids commonly occurring in proteins, including proline), and of L‐alanyl‐L‐tryptophan, L‐seryl‐L‐seryl‐L‐serine, L‐threonyl‐L‐threonyl‐L‐threonine, L‐cystine‐bis‐glycine, and Nα‐acetyllysine to polyadenylic acid, polycytidylic acid and polyguanylic acid were measured. All of these were found to add photochemically to each of these polymers. Polyribothymidylic acid, tested with eleven of these peptides and with Nα‐acetyllysine, was found to be reactive with all.
ELECTRON SPIN ECHO ENVELOPE MODULATION OF THE TRANSIENT EPR SIGNALS OBSERVED IN PHOTOSYNTHETIC ALGAE AND CHLOROPLASTS*
Authors: Thurnauer Marion C. , Clark Carl 
Published: January 2008

AbstractPhase memory decays were obtained from the transient signals sampled within 50 ns of laser excitation by time resolved electron spin echo (ese) spectroscopy in normal protonated, deuterated, deuterated 15N photosynthetic algae and broken chloroplasts. Previously, it has been shown that application of time resolved ese to study these systems, in particular, gives rise to two kinds of signals (standard and special ese). The standard ese signal at g = 2.0023 and the special ese signal exhibit similar electron spin echo envelope modulation (eseem). The modulation frequency and pattern can be identified with that obtained from stable oxidized P700 in the same system. The two lower field resonances of the standard ese signal do not show eseem. The results support the proposed mechanism for formation of special ese and the notion that the standard ese is due to at least two radicals. It is also demonstrated that we can observe eseem of P+700 under ambient temperature conditions.
PHOTODYNAMIC EFFECTS: PORPHYRIN VS CHLORIN
Authors: Kessel David , Dutton Christopher J. 
Published: January 2008

AbstractThe photosensitizing properties of mesoporphyrin were compared with those of a structurally‐related chlorin, bonellin. Using Sarcoma‐180 tumor cells in culture and irradiation at 610–660 nm, we observed a 10‐fold greater efficiency of photodynamic inactivation by the chlorin. This result was correlated with differences in absorption spectra of the two compounds, not with differences in extent and loci of intracellular accumulation.
AMIODARONE PHOTOTOXICITY TO HUMAN ERYTHROCYTES AND LYMPHOCYTES
Authors: HASAN Tayyaba , E. Kochevar Irene , Abdulah Dorina 
Published: January 2008

AbstractAmiodarone (AD) therapy for cardiac arrhythmia frequently leads to cutaneous phototoxicity. Amiodarone and its metabolite, desethylamiodarone (DEA), photosensitized hemolysis of red blood cells (RBC) and were phototoxic to lymphocytes. Hemolysis photosensitized by 3.3 μM AD was partially oxygen dependent and was partially quenched 5 mM sodium azide, 50 mM mannitol, superoxide dismutase (251 U/mee) and catalase (1500 U/me), but was unaffected when H2O was replaced by D2O. These results suggest that membrane damage may be important in the in vivo phototoxicity to AD, that both oxygen dependent and oxygen independent mechanisms may operate, and that active oxygen species such as O2 and hydrogen peroxide may be involved. Photohemolysis was more rapid in the presence of DEA than of AD. However, this may be due to the greater fragility of the cell membrane in the presence of DEA. The greater phototoxicity of DEA than AD towards lymphocytes was not due to greater membrane fragility.
COMPARATIVE STUDIES ON THE LETHAL, MUTAGENIC, AND RECOMBINOGENIC EFFECTS OF ULTRAVIOLET‐A,‐B,‐C, AND VISIBLE LIGHT WITH AND WITHOUT 8‐METHOXYPSORALEN IN Saccharomyces cerevisiae
Authors: Mondon P. , Shahin Majdi M. 
Published: January 2008

AbstractGenetic effects of UV‐A, UV‐B, UV‐C, and the combination of 8‐methoxypsoralen (8MOP) with UV‐A or visible light were studied in the haploid strain XV185–14C and diploid strain D5 of Saccharomyces cerevisiae. The induction of his+, lys+, and horn+ reverse mutations was measured in strain XV185–14C. In strain D5 we measured the induction of genetically altered colonies, particularly twin spot colonies arising from a mitotic crossing‐over. UV‐C and UV‐B induced point mutations at the three loci in the haploid strain and mitotic crossing‐over and other genetic alterations in the diploid strain. UV‐C was more mutagenic and recombinogenic than UV‐B. UV‐A or visible light alone did not induce genotoxic effects at the doses tested. However, UV‐A plus 8‐MOP produced lethal and mutagenic effects in the haploid strain XV185–14C, although mutagenic activity was less than that of UV‐B. Visible light plus 8‐MOP also induced genotoxic effects in strain XV185–14C. In the diploid strain D5, UV‐A plus 8‐MOP induced a higher frequency of genetic alterations than UV‐B at comparative doses. Visible light plus 8‐MOP was also genetically active in strain D5. The haploid strain was more sensitive to the lethal effects of UV‐C, UV‐B, UV‐A, and impure visible light plus 8‐MOP than the diploid strain.