bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE DOSE‐RESPONSE RELATIONSHIP OF TUMORIGENESIS BY ULTRAVIOLET RADIATION OF 254 nm
Authors: Sterenborg H. J. C. M. , van der Putte S. C. J. , van der Leun J. C. 
Published: January 2008

Abstract— Groups of albino hairless mice, Skh‐hrl, were exposed daily to UVC radiation from low pressure Hg arcs (Philips TUV 40W). These lamps emit predominantly radiation of 254 nm. Three groups of animals were used in the experiments, each receiving a different daily dose.The results were described with the Weibull probability function. As in earlier studies with UVB. the tumor induction time was proportional to a power of the daily dose. The exponent turned out to be as low as ‐0.2. This implies that the induction time varied only a little with the daily dose. The average number of tumors per animal was proportional to a power of time. A sample of 73 tumors of at least 4 mm in diameter were investigated histologically. The large majority were classified as squamous cell carcinomas.A comparison was made with the results of an earlier reported experiment with Westinghouse FS40 sunlamps. Throughout the whole range of daily doses used in the present experiment, UVC was less carcinogenic than UVB. An intriguing difference between the two types of radiation was that the tumors induced by UVC appeared much more scattered over the irradiated parts of the animals than the UVB‐induced tumors.
ANTIVIRAL PROPERTIES OF PHOTOSENSITIZERS*
Authors: Hudson J. B. , Towers G. H. N. 
Published: January 2008

Abstract—We have studied the antiviral properties of three different groups of photo‐sensitizers,viz.(i) various furyl compounds; (ii) β‐carboline alkaloids; (iii) thiophenes and their acetylene derivatives. In general the antiviral potency of the furyl compounds correlated with their ability to produce DNA photoadducts.Among the naturally occurring β‐carboline alkaloids, harmine was considerably more potent (in the presence of long wavelength UV radiation, UVA) than several other harmane‐related compounds. Slight alterations in chemical structure had profound effects on their antiviral activities. Harmine was shown to inactivate the DNA‐virus murine cytomegalovirus (MCMV) by inhibiting viral gene expression, although other targets may also exist. Several eudistomins, carboline derivatives isolated from a tunicate, were also photoactive against viruses.Various plant thiophenes and polyacetylenes were studied in detail. These compounds also required UVA for antiviral activity, and some of them were extremely potent against viruses with membranes, e.g. α‐terthienyl, which showed significant activity at only 10‐5μg/ml. When MCMV had been treated with α‐terthienyl plus UVA, the virus retained its integrity and penetrated cells normally; but the virus did not replicate. More than 30 additional thiophenes have recently been evaluated, including many synthetic ones, and some of these are even more potent than a‐terthienyl. We believe that certain thiophenes possess potential therapeutic value and should be tested against model virus infections in animals.
THE ROLE OF HEMOGLOBIN IN THE PHOTOTAXIS OF THE NEMATODE Mermis nigrescens
Authors: Burr A. H. (Jay) , EGGLETON DAVID K. , PATTERSON ROBERT , LEirrscHER‐HAZELHOFF JOHANNA T. 
Published: January 2008

Abstract A dense zone of crystalline hemoglobin in the head has been presumed to be involved in the photosensitivity of Mermis. With the aim of identifying its role, we have studied the wavelength dependence of the phototaxis. Measuring phototaxic efficiency at constant photon fluence rate (intensity), we find that the spectral response curve is approximately fiat from 350–540 nm and falls to an insignificant level by 580 nm. This is unlike the absorptance (fraction absorbed) spectrum of the hemoglobin pigmentation. Also, fluence‐rate/response curves at 420 and 500 nm occur at the same fluence rates even though these wavelengths correspond to a maximum and a minimum of hemoglobin absorption. These results prove that the hemoglobin cannot be functioning as the visual pigment in phototaxis but, for reasons discussed, they neither confirm nor rule out a role as a shadowing pigment. The results are consistent with a shadowing role in the presence of contrast enhancement by the nervous system.A steep fluence‐rate dependence suggests that contrast enhancement does occur in Mermis phototaxis. The 420 or 500 nm fluence rate for half‐maximal response is 6 times 10 photons s‐1 cm‐2 (about equivalent in effectiveness to pre‐dawn twilight). The wide range of sensitivity, 350–560 nm, has interesting implications as to the nature of the visual pigment.†NATO reaearch collaborator a n leave from the Department of Biophysics. Laboratorium voor Algemene Natuurkunde, Rijksuniversiteit Groningen, Westersin‐gel 34. 9718 CM Groningen, The Netherlands.
GEOMETRY OF INTERCALATION OF PSORALENS IN DNA APPROACHED BY MOLECULAR MECHANICS*
Authors: Demaret Jean‐Philippe , Brunie Simone , Ballini Jean‐Pierre , Vigny Paul 
Published: January 2008

Abstract—The results of molecular mechanical calculations on intercalation complexes of 3‐car‐bethoxypsoralen, 5‐methoxypsoralen, 8‐methoxypsoralen, 7‐methylpyrido[3,4‐c]psoralen (MepyPs) and 7‐methylpyrido[4,3‐c]psoralen (2N‐MePyPs) with the double stranded duodecanucleotide d(CGCGATATCGCG)2are presented. In the energy‐minimized structures, the psoralens are intercalated with their plane orthogonal to the helix axis. Stacking interactions between the furan ring of the psoralen and the adjacent bases are maximized in most derivatives studied, whereas the effect of the various substituents of the psoralen ring is to specifically push part of the molecule towards either the minor or the major groove, preventing a symmetrical intercalation (with respect to the two strands of the DNA). The relative position of the psoralen ring and of the adjacent thymine foreshadows the formation of furan‐side monoadducts in 3‐CPs, MePyPs and 2N‐MePyPs, whereas the formation of a pyrone‐side monoadduct appears as geometrically more favourable in 5‐MOP and both furan‐ and pyrone‐side monoadducts can be geometrically envisaged in 8‐MOP. A good correlation therefore exists between the more or less favourable equilibrium geometries and the experimentally observed photoreactions. The present study is the first attempt to characterize the geometrical parameters as part of a complex set of geometrical, dynamical and excited state parameters governing the overall DNA‐psoralen photoreaction.
MONOFUNCTIONAL ANGULAR FUROCOUMARINS: SEQUENCE SPECIFICITY IN DNA HOTOBINDING OF 6,4,4′‐TRIMETHYLANGELICIN and OTHER ANGELICINS
Authors: Miolo G. , DallAcqua F. , Moustacchi E. , Sage E. 
Published: January 2008

Abstract—The sequence specificity in the photoreaction (365 nm) of 6,4,4′‐trimethylangelicin (TMA) with DNA fragments of the lac I gene of Escherichia coli was studied by using DNA sequencing methodology. In order to map the sites of TMA photoaddition, we took advantage of the (3′‐5′) exonuclease activity associated with T4 DNA polymerase, which is blocked by bulky adducts, such as furocoumarin photoadducts. A quantitative analysis of the sites of photoaddition is reported. TMA was demonstrated to photoreact with thymine and, to a lower extent, to cytosine. AT‐rich sequences and I'll sites in a GC context are the most reactive sites towards TMA whereas TA, AT, CA, AC sites are weaker sites with similar reactivity. Cytosines in alternated CG sequences are also targets of TMA photobinding. We observed a less pronounced sequence specificity of TMA than that of other psoralen derivatives already studied (Sage and Moustacchi, 1987; Boyer et al., 1988). A comparison with other furocoumarins 4,4′‐dimethylangelicin (4,4′‐DMA), 4′‐methylangelicin (4′‐MA), angelicin, 4,5′,8‐trimethylpsoralen (TMP) and 8‐methoxypsoralen (8‐MOP) is also reported. The role of flanking sequence and consequently of the local conformation at the various sites of photoaddition is discussed. A preferential orientation of the TMA molecule during the intercalation in the dark is suggested. Hot alkali treatment of TMA‐modified DNA did not reveal any DNA strand breakage due to photooxidized bases.
THE EFFECTS OF NEAR‐UV RADIATION ON HUMAN LENS β‐CRYSTALLINS: PROTEIN STRUCTURAL CHANGES and THE PRODUCTION OF O2_ and H2O2
Authors: Andley Usha P. , Clark Barbara A. 
Published: January 2008

Abstract—β‐Crystallins (β1,‐, β2‐ and β3‐crystallin) comprise nearly half the protein of the human lens. The effect of near‐UV radiation, which is one of the possible risk factors in cataract formation, on the p‐crystallins is investigated in this study. Protein intersubunit crosslinking, change in charge of the protein subunits to more acidic species and changes in protein tertiary structure (conformation) by 300 nm irradiation are reported. The fluorescence yield of protein tryptophan residues decreases by 300 nm irradiation. There is an increase in nontryptophan fluorescence (λcx 340 nm, λcm 400–600 nm), and in protein absorption at 340 nm, due to the formation of tryptophan photooxidation products. Both tryptophan and its oxidation products can be photoexcited by 300 nm irradiation and the latter are known to be good photosensitizers. The results provide evidence for the generation of H202 in the irradiated human β‐crystallin solutions by the Type I photosensitizing action of the chromophores absorbing at 300 nm. The H2O2 is generated via the intermediate production of O‐2 anion; the latter spontaneously dismutates to H202, presumably via O ‐2 ‐ protein interactions. The amount of H2O2 generated per absorbed photon is compared for various solutions of β1,‐, β2‐ and β3‐crystallins from human lenses of different age.
PHOTOPROPERTIES OF ALKOXY‐SUBSTITUTED PHTHALOCYANINES WITH DEEP‐RED OPTICAL ABSORBANCE
Authors: Ford W. E. , Rihter B. D. , Kenney M. E. , Rodgers M. A. J. 
Published: January 2008

Abstract—Triplet‐state properties of 1,4,8,11,15,18,22,25‐octa‐n‐butoxy phthalocyanine and its zinc derivative were determined for the first time. The T1 state of the metal‐free phthalocyanine was characterized by a short lifetime (τT= 17 µs) and low quantum yield (φT= 0.095), and quenching of the triplet by O2 occurred with a bimolecular rate constant (kTσ= 1.3 times 108M‐1 s‐1) that is indicative of an endogonic reaction. The zinc complex (ZnPc(OBu)8) was markedly better as a triplet photosensitizer with respect to both tT (60 µs) and φT (0.5). Quenching by O2 produced singlet oxygen with nearly 100% efficiency, and kTσ (1.7 times 109M‐1s‐1) was close to the spin‐statistical diffusion‐controlled limit. Phosphorescence measurements showed the energy of the T1 state of ZnPc(OBu)8 to be 100 kJ/mol, which is 6 kJ/mol above the lδg state of O2. These photoproperties, together with Q‐band absorption maxima in the mid‐700 nm range indicate that metal‐centered 1,4,8,11,15,18,22,25‐octaalkoxyphthalocyanines have excellent potential as sensitizers in photodynamic therapy.
RED EDGE EXCITATION EFFECT IN INTACT EYE LENS
Authors: Rao Ch. Mohan , Rao S. Chenchal , Rao P. Bheema 
Published: January 2008

Abstract—Shift in the wavelength of emission upon shift in the excitation wavelength towards the red edge of the absorption band is termed Red Edge Excitation Shift (REES). This effect is observed only in a situation where the fluorophore mobility with respect to the surrounding matrix is considerably reduced. We have observed such red edge excitation effect in the intact eye lens. The REES observed for a normal lens is different from that seen in a photodamaged lens and hence appears to be a potential tool to monitor the changes in the state of the lens. Photodamage experiments with tryptophan in polyethylene glycol (PEG) and intact eye lens indicate that the red edge photon can also cause photodamage.
OZONE, MIDDLE ULTRAVIOLET RADIATION AND THE AQUATIC ENVIRONMENT
Authors: Smith Raymond C. 
Published: January 2008

AbstractMarine organisms in the upper layers of the sea may be endangered by increased ultraviolet radiation resulting from declines in the thickness of stratospheric ozone. Evidence supporting this hypothesis includes the fact that wavelengths of potentially damaging ultraviolet radiation can penetrate to ecologically significant depths and laboratory findings that many marine organisms are extremely sensitive to this radiation. Estimated effects of increased ultraviolet radiation on populations of marine organisms range from insignificant to catastrophic. Direct estimation of population effects have not been made, although this is the only adequate measure of the potential impact. The extreme diminution of ozone during the Antarctic spring, coupled with the dynamics of phytoplankton production in this region, may provide conditions suitable for an environmental test of the hypotheses that marine organisms are endangered by reduced stratospheric ozone. There is an urgency to the testing of this hypothesis since these populations may be directly impacted at the present time.
THE PEROXIDASE/OXIDASE ACTIVITY OF SOYBEAN LIPOXYGENASE ‐ I. TRIPLET EXCITED CARBONYLS FROM THE REACTION WITH ISOBUTANAL AND THE EFFECT OF GLUTATHIONE
Authors: SCHULTE‐HERBRUGGEN THOMAS , SIES HELMUT 
Published: January 2008

AbstractSoybean lipoxygenase shows a secondary peroxidase/oxidase activity: The aerobic reaction with isobutanal, enhanced by hydrogen peroxide as a cosubstrate, yields acetone, exhibits chemiluminescence and consumes oxygen (φcl= 1.3 × 10‐9photons/O2molecule consumed). 9,10‐Dibromoanthracene‐2‐sulfonate increases the photoemission (kelφ= 2 104M‐1;= 0.9 × 10‐7photons/O2), whereas it is diminished by sorbate, tryptophan, 2‐methyl‐1,4‐naphthoquinone, glutathione, and superoxide dismutase. In the presence of hydrogen peroxide the lipoxygenase reaction with glutathione yields yet another excited state.From the well‐known reactions promoted by horseradish‐peroxidase, these features are concluded to indicate the novel activity of soybean lipoxygenase. With isobutanal as a substrate lipoxygenase acts as an oxidase and as a peroxidase. The mechanism suggested leads to photoemissive triplet excited acetone as expected from the cleavage of an intermediate dioxetane.
THE PEROXIDASE/OXIDASE ACTIVITY OF SOYBEAN LIPOXYGENASE – II. TRIPLET CARBONYLS AND RED PHOTOEMISSION DURING POLYUNSATURATED FATTY ACID AND GLUTATHIONE OXIDATION
Authors: SCHULTE‐HERBRUGGEN THOMAS , SIES HELMUT 
Published: January 2008

AbstractDuring the aerobic reaction of soybean lipoxygenase with polyunsaturated fatty acids (linoleic, linolenic, and arachidonic acid) oxygen uptake is followed by excited carbonyl photoemission. The chemiluminescence yield of φcl= 10‐10photons/O2molecule consumed is enhanced 2–3 orders of magnitude by the carbonyl sensitizers 9,10‐dibromo‐anthracene‐2‐sulfonate (kETφ= 104M‐1; φcl= 10‐8photons/O2) and chlorophyll‐a(kETφ= 106M‐1φcl= 10‐7photons/O2), respectively. α,β‐Saturated triplet excited carbonyls as from 1,2‐dioxetane cleavage are discussed to arise from a secondary peroxidase/oxidase reaction with aldehydes formed in the course of enzymic lipid peroxidation.When 1 mMglutathione is added to the aerobic lipoxygenase/arachidonate reaction, carbonyl emission (375–455 nm) is replaced by intense red bands (630–645 nm and 695–715 nm) resembling the characteristic spectrum of (1†g)O2‐singlet oxygen dimol‐emission. The quantum yield (φcl= 10‐8photons/O2) remains unaffected by chlorophyll indicating that the red emission is independent of excited carbonyls. The effect of GSH is attributed to dioxetane interception and subsequent glutathione peroxidation generating1O2by electron transfer from the superoxide anion radical to a peroxysulfenyl radical.
PHYTOCHROME CONTROL OF EXTRACELLULAR PEROXIDASE ACTIVITY IN MUSTARD INTERNODES: CORRELATION WITH GROWTH, and COMPARISON WITH THE EFFECT OF WOUNDING
Authors: Casal Jorge J. , Whitelam Garry C. , Smith Harry 
Published: January 2008

Abstract— The effects of phytochrome status on extracellular peroxidase activity were investigated in Sinapis alba L. seedlings grown for 12 days under continuous white light and transferred to darkness after a red light or a far‐red light pulse. The rates of extension growth and dry matter accumulation in the first internode were increased by the far‐red light pulse. Extracellular proteins, obtained by low speed centrifugation of intact internodes infiltrated with CaCl2, were separated by isoelectrofocusing, and four extracellular acidic peroxidases were resolved, the most active being A3 and A4 (both ˜60 kD). The activity of A4 was reduced by the far‐red light pulse perceived by phytochrome, while the activity of A3 was unaffected. The promotion of internode extension growth caused by far‐red light is biphasic [Casal and Smith (1989) Plant, Cell Environ.12,511–50]. Changes in peroxidase activity were detected prior to the second, but not to the first phase of the internode growth promotion. The effects on both growth and peroxidase activity were virtually restricted to the upper half of the internode and, once established, did not subsequently increase in magnitude.In contrast to the effects mediated by phytochrome, blue light pretreatments affected growth but not extracellular peroxidase activity. Wounding the internode reduced extension growth, increased the activity of A3, but caused no significant effects on A4.Other extracellular proteins, separated in sodium dodecyl sulphate polyacrylamide gels and stained with Coomassie blue, showed no significant differences. The concentration of extracellular proteins was higher in the upper than the lower half of the internode.Results are discussed in terms of phytochrome effects in light grown plants, peroxidase activitv‐arowth relationships, and extracellular peroxidase isoform functions.
ON THE MULTIPLE CYCLES OF BACTERIORHODOPSIN AT HIGH pH
Authors: Bitting Herbert C. , Jang Du‐Jeon , El‐Sayed M. A. 
Published: January 2008

AbstractBacteriorhodopsin (bR) shows at least two parallel photocycles at pH 10.5, suggesting that more than one form of bR exists in alkaline bR sample. Upon the absorption of visible light, the different forms of bR at high pH yield different parallel intermediates: M412 with two rise and two decay components; and R, an extremely fast rising and extremely slow decaying intermediate with an absorption peak at 350 nm. The kinetics and spectra do not agree with the proposal of Kouyama el al. (1988, Biochemistry 27,5855–5863) that the 350 nm‐absorbing species is the N intermediate which follows M412 and that the slow decaying M412 is an M‐like photoproduct of N. Our results basically agree with the proposal of Dacshazy et al. (1988, Proc. Natl. Acad. Sci. USA 85,6358–6361) that the fast and slow decaying M412 intermediates and R are in independent photocycles arising from different forms of bR. The different forms of bR are probably in dynamic equilibrium with their ratios controlled by pH and ionic strength.
QUINONES AS MEDIATORS OF ELECTRON TRANSFER FROM MEMBRANE‐BOUND CHLOROPHYLL TO CYTOCHROME c IN THE AQUEOUS PHASE IN LIPID BILAYER VESICLES: SYNERGISTIC ENHANCEMENT OF CYTOCHROME c REDUCTION BY LIPOPHILIC/ HYDROPHILIC QUINONE PAIRS
Authors: Chamupathi V. G. , Tollin G. 
Published: January 2008

AbstractLaser flash photolysis has been used to determine the kinetics of cytochrome c reduction by chlorophyll triplet state in negatively‐charged lipid bilayer vesicles, as mediated by quinones. Large synergistic enhancements in the yield of reduced cytochrome were obtained using a pair of quinones, one of which was lipophilic (e.g. benzoquinone, 2,6‐di‐f‐butylbenzoquinone) and the other of which was hydrophilic (e.g. l,2‐naphthoquinone‐4‐sulfonate). The mechanism was shown to involve initial quenching of the triplet by the membrane‐associated quinone to form chlorophyll cation radical and quinone anion radical. An interquinone electron transfer process followed this reaction, which occurred at the membrane‐water interface, and greatly facilitated electron transport from within the bilayer to the aqueous phase. This process formed the basis of the synergistic effect. Cytochrome c reduction occurred in the water phase by reaction with the anion radical of the hydrophilic quinone. Finally, the reduced cytochrome was reoxidized by a slow reaction with chlorophyll cation radical. Under the most favorable conditions, we estimate that the quantum yield of conversion of triplet quenching events to reduction of cytochrome approached unity. The lifetime of the reduced protein and oxidized chlorophyll could be as long as 140 ms, under the best conditions. This system has properties which are thus quite favorable for solar energy conversion in a biomimetic process.
EFFECT OF TEMPERATURE AND pH ON THE QUENCHING OF TRIPLET LUMIFLAVIN IN THE PRESENCE AND ABSENCE OF FERRI‐ AND FERROCYANIDE
Authors: Naman S. A. 
Published: January 2008

Abstract—–Flash photolysis at 450 nm over the temperature range 0.8–60°C was used to determine Arrhenius parameters for the first and second order disappearance of triplet lumiflavin (1.66 µ.M) at a flash energy of 2 kj in deaerated phosphate buffer at varying pH:3Lf → Lf03Lf +3Lf → Lf0+ Lf0Arrhenius parameters were also determined for the pseudo first‐order quenching of triplet lumiflavin by 10 µMferri‐ and ferrocyanide ions,3Lf + Fe3+→ Fe3+→ Lf0+ Fe3+(energy transfer)3Lf + Fe2+→ Lf‐+ Fe3+(electron transfer)and for disappearance of the semireduced lumiflavin in the presence of ferrocyanide at pH 6.8, by the second‐order reactionLf‐+Lf‐→ Lf0+ Lf=.
PHOTOOXYGENATION OF BIPHENYL AND ITS DERIVATIVES via PHOTOINDUCED ELECTRON TRANSFER: EFFECT OF Mg(CIO4)2 ON PHOTOOXYGENATION
Authors: Tamai Toshiyuki , Mizuno Kazuhiko , Hashida Isao , Otsuji Yoshio 
Published: January 2008

AbstractThe 9,10‐dicyanoanthracene (DCA)‐sensitized photooxygenation of biphenyl derivatives in the presence of Mg(CIO4)2 in acetonitrile produces benzoic acid and its derivatives in high yields. In the absence of Mg(CIO4)2, the rates for the consumption of biphenyl derivatives decrease by a factor of 0.5‐0.8, compared with those in the presence of Mg(CIO4)2. In these cases, however, both biphenyls and DCA are oxygenated to give benzoic acids and anthraquinone, respectively, indicating that the addition of Mg(CIO4)2 retards the photooxygenation of DCA. With 4‐methylbiphenyl, the photooxygenation proceeds efficiently without added Mg(CIO4)2, and benzene rings and methyl groups are competitively oxygenated to give benzoic acid, 4‐methylbenzoic acid, 4‐phenylbenzoic acid, and 4‐phenylbenzaldehyde. The addition of Mg(CIO4)2 facilitates the oxidation of benzene rings, giving benzoic acid and 4‐methylbenzoic acid as major products. These photooxygenations are initiated by a one‐electron transfer from biphenyls to the excited singlet DCA and proceed via the radical cations of biphenyls and the radical anion of DCA.
SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–XVI. ISPERSE BLUE 35
Authors: Dabestani Reza , Reszka Krzysztof J. , Davis Donald G. , Sik Robert H. , Chignell Colin F. 
Published: January 2008

AbstractThe photochemistry (Type I and II) of the phototoxic textile dye Disperse Blue 35 (DB‐35) and its purified components has been studied using electron spin resonance in conjunction with spin trapping technique and the direct detection of singlet oxygen (1O2) luminescence. The main components of DB‐35 (which is synthesized by the successive nitration, reduction and methylation of 1,8‐dihydroxy‐anthraquinone) were separated by HPLC and identified by mass spectrometry and 2‐D NMR as 4,5‐diamino‐1,8‐dihydroxyanthraquinone (4,5‐DDHAQ; 62% of total dye) and 2,7‐diamino‐1,8‐dihydroxyanthraquinone (2,7‐DDHAQ; 31% of total dye). Minor components included 2,5‐diamino‐1,8‐dihydroxyanthraquinone (2,5‐DDHAQ) and a monomethylated derivative of either 4,5‐DDHAQ or 2,7‐DDHAQ. Irradiation (624 nm) of 4,5‐DDHAQ and 2,7‐DDHAQ in dimethylsulfoxide resulted in the generation of superoxide which was trapped by 5,5‐dimethyl‐l‐pyrroline‐N‐oxide (DMPO). Visible light irradiation of the components in ethanol generated 1O2 with the yields decreasing in the following order: 4,5‐DDHAQ > 2,5‐DDHAQ > 2,7‐DDHAQ. These findings indicate that upon irradiation by visible light DB‐35 can generate active oxygen species which may be responsible for the photocontact dermatitis caused by this dye.