bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOTO‐ AND THERMAL‐ACTIVATION OF BOVINE LIVER UROCANASE
Authors: Hug Daniel H. , Hunter John K. , Bedell Bruce A.
Published: January 2008

Abstract— In the photoactivation of sulfite‐modified urocanase from Pseudomonas putida, the sulfite adds to the nicotinamide adenine dinucleotide and photodissociation accompanies activation. Bovine urocanase contains the same coenzyme. The purpose was to find if sulfite can inactivate a mammalian urocanase and if UV light can reactivate the enzyme. It was inactivated by sulfite,10–100 i.M, and dialysis did not restore activity. Near‐UV light (11 W m‐2) reactivated the enzyme in 45 min. A competitive inhibitor protected urocanase from sulfite, showing that sulfite acts at the active site. The modification was dependent on temperature, time, and concentration of sulfite. The modification was reversed by incubation at 25°C for 24 h. These results resemble those found with the P. putida urocanase. It is likely that these thermal‐ and photo‐reactions are the same for the bacterial and mammalian urocanases.
DEACTIVATION OF SINGLET MOLECULAR OXYGEN BY THIOLS AND RELATED COMPOUNDS, POSSIBLE PROTECTORS AGAINST SKIN PHOTOSENSITIVITY
Authors: Rougee M. , Bensasson R. V. , Land E. J. , Pariente R.
Published: January 2008

Abstract— From time‐resolved measurements of the decay of singlet molecular oxygen phosphorescence at 1270 nm in D2O, direct estimates have been gained for the rate constants of the singlet oxygen reactions with a group of sulphur compounds in the pD range 5 to 13. In the case of most of the thiols, the results are consistent with singlet oxygen reacting exclusively with the thiolate anions. At the normal physiological pH 7, the apparent rate constants (in units of M‐1 s‐1) were 8.9 times 106 (cysteine), 2.5 times 106 (N‐acetyl cysteine), 2.9 times 106 (glutathione), 3.0 times 105 (2‐mercaptoethanol), 2.3 times 107 (ergothioneine) and 2.7 times 106 (2‐mercaptopropionyl glycine). For methionine the rate constant, 1.4 times 107, was independent of pD in the range studied. These sulphur compounds, in particular N‐acetyl cysteine and ergothioneine, or related compounds, might be considered as possible candidates for protection against skin photosensitivity side effects associated with the photodynamic therapy of solid tumours and as observed in the disease erythropoietic protoporphyria.
PHOTOLYSIS OF PHOSPHODIESTER BONDS IN PLASMID DNA BY HIGH INTENSITY UV LASER IRRADIATION
Authors: Choke David T. , Blau Werner , Ohuigin Colm , Kelly John M. , Mcconnell David J.
Published: January 2008

Abstract— The cleavage of phosphodiester bonds in DNA exposed to high intensity UV laser pulses in aerated aqueous solution has been investigated using a krypton fluoride excimer laser (248 nm) and bacterial plasmid DNA. The dependence of strand breakage on fluence and intensity has been studied in detail and shows that the process is non‐linear with respect to intensity. The relationship between the quantum yield for strand breakage and intensity shows that the strand breakage reaction involves two‐photon excitation of DNA bases. The quantum yield rises with intensity from a lower value of 7 times 10‐5 until a maximum value of 4.5 times 10‐4 is attained at intensities of 1011 W m‐2 and above. This value is approximately fifty‐fold higher than the quantum yield for strand breakage induced by exposure to low density UV irradiation (254 nm, 12 W m‐2). DNA sequencing experiments have shown that strand breakage occurs by the specific cleavage of the phosphodiester bond which lies immediately 3′ to guanine residues in the DNA, leaving some alkali‐labile remnant attached to the terminal phosphate. A mechanism for DNA strand breakage which involves the generation of guanine radical cations is proposed.
CYTOTOXICITY AND GENOTOXICITY OF UVA IRRADIATION IN CHINESE HAMSTER OVARY CELLS MEASURED BY SPECIFIC LOCUS MUTATIONS, SISTER CHROMATID EXCHANGES AND CHROMOSOME ABERRATIONS
Authors: Lundgren Karsten , Wulf Hans Christian
Published: January 2008

Abstract— The increasing use of artificial UVA (320‐400 nm) suntanning devices has brought attention to possible hazardous effects of UVA. In contrast with earlier studies, several groups recently have described that UVA possibly is mutagenic. In this paper we evaluate the genotoxic properties of broad band UVA using CHO cells and three different assays: specific locus (HGPRT) mutations, chromosome aberrations, and sister chromatid exchanges (SCEs). The UVA‐source was an UVASUN 2000 S (Mutzhas), emitting UVA above 340 nm. The survival curve of the cells exhibited a shoulder up to 200 kJ/m2, that was followed by exponential killing at higher fluences. Mutations were induced linearly in the fluence range from 0‐200 kJ/m2 (P < 0.001) to a level seven fold higher than the spontaneous, followed by a decrease at fluences above 300 kJ/m2. Over the total range of tested fluences (0‐300 kJ/m2) a linear dose‐response relationship was observed for UVA‐induced SCEs (P < 0.001). A significantly higher percentage of the cells showed chromosomes with aberrations at the higher levels of exposure (200, 300 and 400 kJ/m2), but no dose response was demonstrated. Our results confirm recent findings showing that UVA is mutagenic in mammalian cells and suggest that UVA exposure may contribute to the total burden of genetic damage caused by exposure to ultraviolet light.
MEASUREMENTS OF SOLAR MIDDLE ULTRAVIOLET RADIATION IN A DESERT ENVIRONMENT
Authors: Kollias N. , Baqer A. H. , Sadiq I.
Published: January 2008

Abstract— In this study measurements are reported that were carried out between August 1983 and December 1985 on the solar middle ultraviolet radiation (UVB‐280‐320 nm) in Kuwait (29.5°N). These measurements are based primarily on polysulfone film detectors. Comparative measurements were also made on a Robertson‐Berger meter and a spectroradiometer. The results reported include the daily variation of the solar UVB between 11:30 a.m. and 12:00 noon over the year, the diurnal variation, as well as the amount of UVB as a function of the receiving angle with the horizontal.

Based on these data the polysulfone films were found to be reliable and inexpensive detectors, giving results similar to those of the R‐B meter. The diurnal variation of the solar UVB was found to vary as sin2q, where q is an angle that corresponds to the time since sunrise compared to the sunrise‐sunset interval times 180. An empirical equation is developed that gives the maximum UVB as a function of the time of day and day of year. A correlation is determined of the polysulfone readings with the spectroradiometric and the R‐B meter measurements. The solar insolation was found to be independent of the receiving angle with the horizontal in the winter months and develops into a cosine dependence in the summer months.
STRUCTURE AND STABILITY OF γ‐CRYSTALLINS‐IV. AGGREGATION AND STRUCTURAL DESTABILIZATION IN PHOTOSENSITIZED REACTIONS
Authors: Mandal Krishnagopal , Kono Masahiro , Bose Swapan K. , Thomson John , Chakrabarti Bireswar
Published: January 2008

Abstract— Unlike α‐ and β‐, γ‐crystallins become turbid upon irradiation with 300 nm or white light in the presence of photosensitizers, e.g., methylene blue (MB) or riboflavin (RF). These proteins, however, do not aggregate in the presence of guanidine hydrochloride. Turbidity formation is concentration‐dependent. Except in RF‐sensitized reactions, the onset and rate of turbidity formation are faster in γ‐IV than in the other two crystallins. Labeling the thiol groups of the protein with iodoacetamide does not change the turbidity rate in case of irradiation with 300 nm light, but it does change it in case of RF‐ or MB‐sensitized reaction. The order of rate constants of the decrease in tryptophan emission under aerobic conditions upon 300 nm irradiation and MB‐ and RF‐sensitized reactions is γ‐IV > γ‐III > γ‐II. The rate constants in the absence of air and in the presence of D2O upon MB‐ and RF‐sensitized reactions also indicate that the role of singlet oxygen is significant in the former reaction. We suggest that the photoinduced structural changes occur in two steps. In the first, photooxidation of tryptophan as well as cysteine residues (including the buried cysteines) occurs, leading to small conformational changes of the protein. Conformational changes of the protein, as evident from the near‐UV CD and fluorescence lifetime measurements, subsequently result in aggregation of the protein. As suggested by X‐ray analysis, the perturbation of the cys 78 and 32 by the active species of oxygen appears to be responsible for the destabilization of the protein structure, resulting in rapid aggregation of these crystallins.
RED CHEMILUMINESCENCE FROM RAM SEMINAL VESICLE MICROSOMES: PITFALLS IN THE USE OF SPECTRALLY RESOLVED RED CHEMILUMINESCENCE AS A TEST FOR SINGLET OXYGEN IN BIOLOGICAL SYSTEMS
Authors: Kanofsky Jeffrey R.
Published: January 2008

Abstract— The assignment of the red chemiluminescence bands in the ram seminal microsome system to singlet oxygen as previously reported by Cadenas and Sies (1983) Hoppe‐Seyler's Z. Physiol. Chem. 364, 519‐528 was re‐evaluated. Measurements of 1268 nm emission demonstrated that ram seminal vesicle microsomes produced very small quantities of singlet oxygen (0.41 2 0.05 p.M) when they metabolized high concentrations of 15‐hydroperoxyarachidonic acid (1 mM). The red chemilumi‐ nescence, however, was not due to singlet oxygen, since it failed to increase in deuterium oxide and it was five orders of magnitude larger than the predicted emission from singlet oxygen produced in this system. Quantitative measurements of the time integral of the square root of the red chemiluminescence intensity may be a useful test to confirm the assignment of red emission to singlet oxygen in other biochemical systems.
PHOTOBIOLOGICAL PROPERTIES OF A NOVEL, NATURALLY OCCURRING FUROISOCOUMARIN, CORIANDRIN
Authors: Ashwood‐Smith M. J. , Warrington P. J. , Jenkins M. , Ceska O. , J.Romaniuk P.
Published: January 2008

Abstract— The photobiological properties of a novel, naturally occurring furoisocoumarin isolated from coriander and named coriandrin are described. Photosensitized lethal and mutagenic effects in bacteria indicate that it is more active than psoralen. It is a weak frameshift mutagen in the dark. Mammalian cells in tissue culture are photosensitized more actively with coriandrin than with psoralen even though preliminary evidence from interrupted radiation experiments and DNA analysis suggest that coriandrin does not form DNA interstrand crosslinks. Sister chromatid exchanges were induced with a unit dose of 1.1 times 10‐2 with coriandrin; the value for psoralen is 3 times 10‐3. Coriandrin appears to be metabolized more rapidly than furocoumarins by liver mixed function oxidases. Skin photosensitizing activity is very weak compared with psoralen, a surprising observation considering its potency in biological test systems.
CHEMICAL MODIFICATION AND CHARACTERIZATION OF THE ALPHA CYSTEINE 106 AT THE Vibrio harveyi LUCIFERASE ACTIVE CENTER
Authors: Paquatte Olivier , Tu Shiao‐Chun
Published: January 2008

Abstract— Vibrio harveyi luciferase, an αβ dimer, was effectively inactivated by treatment with the methylation agent methyl p‐nitrobenzene sulfonate. However, inactivation of luciferase in the presence of excess amounts of this reagent did not follow pseudo‐first‐order kinetics. After taking the autodecay of this reagent into consideration in kinetic analysis, the pseudo‐first‐order constants and subsequently the second‐order rate constant (83 min‐1M‐1 at pH 7 and 23°C) were determined. The inactivation rate can be retarded by the addition of the decanal or the reduced FMN substrate but not by the reaction product FMN. The binding of decanal specifically protected one target residue against modification with a concomitant protection of luciferase against inactivation. A pentapeptide containing this specific target residue was isolated and identified to be Phe‐Gly‐Ile‐X‐Arg with X corresponding to the S‐methylated form of the cysteinyl residue at position 106 of the luciferase α subunit. It is concluded that this reactive αCys‐106 is at the aldelhyde site and is also near the reduced flavin site of luciferase. The modified enzyme exhibited no gross conformational changes detectable by protein fluorescence measurements, which may be due to the small size change of the target cysteinyl residue after methylation. The methylated enzyme still retained the ability to bind one decanal and one reduced FMN without any substantial changes in binding affinities. The cause of luciferase inactivation by the methylation of αCys‐106 has been shown to be the impaired ability to form the 4a‐hydroperoxy‐flavin intermediate from the bound flavin substrate or to stabilize this intermediate.
ELECTRON SPIN RESONANCE STUDY OF THE RELATIONSHIP OF UV IRRADIATION TO NITROXIDE RADICAL FORMATION IN DESFERRIOXAMINE (DESFERAL) AND RELATED HYDROXAMATE AND HYDROXYLAMINE DERIVATIVES
Authors: HINOJOSA O. , JACKS T. J. , CALAMARI T. A. , THIBODEAUX D. P.
Published: January 2008

Abstract UV irradiation of desferoxamine (Desferal) produced a well resolved electron spin resonance spectrum that we attributed to a nitroxide radical on the basis of the g value and hyperfine splitting constants. Of related hydroxylamines, only N, N‐dialkyl or N‐isopropyl and larger branched N‐alkyl derivatives formed nitroxides and UV was not needed; smaller N‐alkyl and N, N‐dicarbonyl derivatives were inert to UV. Of related acetohydroxamates, the N‐methyl and N‐ethyl derivatives required UV irradiation for radical formation; the other, larger branched N‐alkyl derivatives readily formed free radicals without UV. Nitroxides from hydroxamates, as represented by UV‐irradiated desferoxamine, were predominant at acidic pH values; those from hydroxylamines, as represented by N, N‐dimethyl hydroxylamine, were so at alkaline values. The results were related to the electron donating and withdrawing properties of the N‐substituting groups and the derealization of the unpaired electron.
THE ‘Q‐BAND’ ABSORPTION spECTRA OF HEMATOPORPHYRIN MONOMER AND AGGREGATE IN AQUEOUS SOLUTION
Authors: SMITH GERALD J. , GHIGGINO KENNETH P. , BENNETT LOUISE E. , NERO TRACY L.
Published: January 2008

Abstract The resolution of the absorption spectra in the Q band (480 nm‐620 nm) spectral region of monomeric and dimeric hematoporphyrin species present in aqueous solutions has been achieved using absorption, fluorescence and computer analysis methods. The absorption maxima of the dimer in this spectral region are red shifted about 12 nm with respect to those of the monomer. The significance of this finding in relationship to the well documented blue shift of hematoporphyrin aggregate observed in the Soret band region (λmalx∼400 nm) of the absorption spectrum is discussed.
ENHANCEMENT OF UV‐INDUCED SKIN CARCINOGENESIS BY AZATHIOPRINE: ROLE OF PHOTOCHEMICAL SENSITISATION
Authors: KELLY GRAHAM E. , MEIKLE WILLIAM D. , MOORE DOUGLAS E.
Published: January 2008

Abstract The phototoxicity of various drugs (chlorpromazine (CPZ), metronidazole (MET), 8‐methoxypsoralen (8‐MOP), azathioprine (AZA) and the azathioprine metabolites, 6‐mercaptopurine (6‐MP), methylnitrothio‐imidazole (MNTI), methylnitroimidazole (MNI)) was determined in hairless (Skh‐hrl) mice exposed to a light source with broad emission (290–700 nm). Chlorpromazine, MET, 8‐MOP, AZA, MNI and 6‐MP were phototoxic, as determined by the oedematous response of skin, at doses comparable to those used clinically.

The effects of long‐term drug therapy and UV radiation on skin carcinogenesis were then determined. Chlorpromazine and MET, and to a lesser extent AZA, MNTI and 6‐MP, enhanced photocarcinogen‐esis. In each case, both the tumour yield and the proportion of malignant:benign skin tumours were increased. The results of this study imply that prolonged treatment of mice with low‐level phototoxins predisposes to photocarcinogenesis.
INFLUENCE OF DIETARY MENHADEN OIL UPON CARCINOGENESIS AND VARIOUS CUTANEOUS REspONSES TO ULTRAVIOLET RADIATION*
Authors: ORENGO IDA F. , BLACK HOMER S. , KETTLER ANNE H. , WOLF JOHN E.
Published: January 2008

Abstract Recent reports suggest that eicosapentaenoic acid (EPA) inhibits growth of transplanted tumors and the formation of various chemically induced cancers in animals. Menhaden oil is a source of polyunsaturated lipid with a high content of EPA, an omega‐3 fatty acid. We sought to explore the effects of menhaden oil on photocarcinogenesis by employing the hairless mouse/UV‐carcinogenesis model. Five groups of 40 SKH‐Hr‐1 mice received (a) a semipurined equicaloric diet containing either 0.75% corn oil, 4% corn oil. 4% menhaden oil or 12% menhaden oil and (b) an escalating regimen of UV radiation to a cumulative dose of 70 J/cm2. Additional animals were employed to further examine the role of menhaden oil in acute cutaneous responses to UV, i.e., erythema, edema, and ornithine decarboxylase (ODC) induction. After a 2‐week feeding period UV‐induced ODC activity in mice receiving 12 or 20% menhaden oil was 3 to 13‐fold lower than that of corn oil fed animals. Further studies showed that edema was also markedly decreased. Animals receiving menhaden oil required twice the level of irradiance to evoke a comparable erythema as that which occurred in corn oil fed animals.

Menhaden oil exerted significant influence upon carcinogenic expression, as manifested in significantly longer tumor latent periods and lower tumor multiplicities when compared to corn oil fed animals. Although the mechanism(s) of these menhaden oil effects remains unknown, it is clear that this unique lipid has a pronounced influence upon cutaneous photoresponses.

15th Annual Meeting of the American Society for Photobiology, Bal Harbor, FL, June, 1987.
KINETICS OF CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER REACTIONS IN PHOspHOLIPID BILAYER VESICLES
Authors: RONG SHOUYU , BROWN RICHARD K. , TOLLIN GORDON
Published: January 2008

Abstract The effects of electrostatic surface charge and valinomycin addition in the presence of K* on the kinetics and the inside‐outside asymmetry properties of light‐induced electron transfer reactions between chlorophyll triplet state and benzoquinone, ferricyanide and methyl viologen in large unilamellar vesicles have been investigated using laser flash photolysis. Modifying the surface charge of the bilayers by incorporating charged surfactants or decreasing the ionic strength of the suspending medium caused large changes in the dynamics of the electron transfer reactions, which could be interpreted in terms of electrostatic interactions between reactants, products and membrane components, and the existence of a spontaneous transmembrane electrical potential corresponding to an excess of negative charge at the outer surface of the vesicle bilayer. The presence of valinomycin had more specific effects on these reactions, which were consistent with an electrostatic influence of the presence of the positively‐charged K+‐valinomycin complex within the bilayer on the dynamics of only those triplet quenching and radical formation and decay processes which occur in this region of the vesicle structure.
TRANSDUCIN ACTIVATION BY MOLECULAR SPECIES OF RHODOPSIN OTHER THAN METARHODOPSIN II*
Authors: OKADA DAISUKE , NAKAI TOSHIKI , IKAI ATSUSHI
Published: January 2008

Abstract [1] Decay of metarhodopsin II was accelerated by hydroxylamine treatment or dark incubation of metarhodopsin II at 30°C. The products thus obtained after decay of metarhodopsin II induced GTPase activity on transducin as well as metarhodopsin II suggesting that rhodopsin could activate transducin after the decay of metarhodopsin II intermediate. [2] After urea‐treated bovine rod outer segment membrane was completely bleached, rhodopsin in the membrane was regenerated by the addition of 11‐cis retinal at various temperatures between 0 and 37°C. The capacity to induce GTPase activity on transducin and phosphate incorporating capacity catalyzed by rhodopsin kinase were measured on such rhodopsins. The results showed that: (1) Regeneration of alpha band of rhodopsin was complete regardless of regeneration temperature; (2) When regenerated at temperatures below 10°C, rhodopsins induced a GTPase activity on transducin in the dark even after treatment with hydroxylamine, whereas rhodopsins after regeneration at temperatures above 13°C did not; (3) When regenerated at 0°C, rhodopsin was phosphorylated if incubated with rhodopsin kinase and ATP in the dark, whereas the spectrally regenerated rhodopsin at 30°C was not. The complete quenching of functions of photoactivated rhodopsin was achieved by recombination with 11‐cis retinal at temperatures above 13°C but not below 10°C suggesting the existence of a low temperature intermediate upon regeneration.

Nishigonaka, Okazaki 444. Japan.
EFFECT OF LIGHT QUALITY ON THE in vitro THYLAKOID PROTEIN PHOSPHORYLATION IN THE GREEN ALGA Scenedesmus obliquus
Authors: HEIL WOLFGANG G. , DÖRNEMANN DIETER , SENGER HORST
Published: January 2008

Abstract Thylakoid protein phosphorylation was assayed in vitro with isolated thylakoids of Scenedesmus obliquus by irradiation with monochromatic light of different wavelengths and equal photon fluences. The action spectrum for light‐activated protein phosphorylation showed two maxima at 450 and 679 nm. A minimum of activity was reached around 580 nm. At this wavelength, the level of protein phosphorylation barely differed from that of dark‐incubated samples. The action spectrum of thylakoid protein phosphorylation resembled the chlorophyll absorption spectrum obtained in vivo. The results show that chlorophyll is the photoreceptor for thylakoid membrane phosphorylation.
OVERPRODUCTION OF SSB PROTEIN ENHANCES THE CAPACITY FOR PHOTOREPAIR IN Escherichia coli recA CELLS
Authors: LERŠ NELLA , SALAJ‐ŠMIC ERIKA , TRGOVČEVIĆ ŽELJKO
Published: January 2008

Abstract We studied photoreactivation in cells carrying the multicopy ssb+ plasmid. These cells overproduce single‐stranded DNA‐binding protein (SSB). Overproduction of SSB enhances the capacity for photoreactivation in recA bacteria but not in the recA+ background. It is suggested that, in recA cells, SSB binds to the dimer region of DNA and that this binding stimulates the process of photoreactivation. In recA+ cells, the same stimulation might be achieved by RecA protein.
SYNTHESIS AND PHOTOCYTOTOXICITY OF SOME NEW SUBSTITUTED PHTHALOCYANINES
Authors: LEZNOFF C. C. , VIGH S. , SVIRSKAYA P. I. , GREENBERG S. , DREW D. M. , BEN‐HUR E. , ROSENTHAL I.
Published: January 2008

Abstract Some new, ring‐substituted phthalocyanines have been synthesized and underwent preliminary testing for photodynamic activity using the colony forming ability of Chinese hamster cells in culture as an endpoint. Using 4‐(3‐N, N‐diethylaminopropyl)phthalonitrile as a precursor, the previously unknown metal‐free 2,9,16,23‐tetra‐(3‐N, N‐diethylaminopropyl)phthalocyanine was prepared and converted to its zinc (II) and its cationic water‐soluble 2,9,16,23‐tetramethylammonium zinc (II) iodide derivatives. Other new phthalocyanine derivatives tested, include a 2,9,16,23‐tetra(2‐hydroxymethyl‐2‐methyIbutoxy)phthalocyaninato zinc (II) and 2,3,9,10,16,17,23,24‐octahydroxyphthalocyaninato zinc (II) derivatives. Boron tribromide cleavage of the newly prepared and fully characterized 2,3,9,10,16,17,23,24‐octamethoxyphthalocyanine gave the unstable metal‐free octahydroxyphthalocy‐anine, which could only be characterized by ultraviolet‐visible, NMR and IR spectroscopy.
THE LATE PHASE OF HEMATOPORPHYRIN DERIVATIVE‐INDUCED PHOTOTOXICITY IN MICE: RELEASE OF HISTAMINE and HISTOLOGIC CHANGES
Authors: Nicholas Dan He , Soter A. , Lim Henry W.
Published: January 2008

Abstract—

This study was designed to directly examine the role of mast cells and the histologic changes in the late phase (4–48 h) of hematoporphyrin derivative‐induced phototoxicity. BALB/c mice were rendered phototoxic by intraperitoneal injection of HpD, followed by exposure to 1.59 kj/m2 of 396–406 nm radiation. Immediately before radiation, and at 4, 8, 12, 18, 24 and 48 h after radiation, the ear thickness, serum histamine levels and histologic changes of ears were examined. A maximal net increase in ear thickness of 33.5 ±0.3 times 10‐2 mm (mean ± SE) was noted at 12 h, associated with a maximal net increase of serum histamine (43.3 ± 11.6 ng/ml, mean ± SE), and a maximal mast cell degranulation. Other histologic changes consisted of mild epidermal spongiosis at 18–24 h, and a predominant neutrophilic infiltrate, which peaked at 24 h (211.6 ± 0.4 cells/mm2). No significant alteration was observed in control mice. These data indicated that mast cells participate in the late phase of HpD‐induced phototoxicity in mice.
AN ANALYSIS OF PHYTOCHROME‐MEDIATED THRESHOLD CONTROL OF HYPOCOTYL GROWTH IN MUSTARD (Sinapis alba L.) SEEDLINGS†
Authors: Oelze‐Karow Heidemarie , Mohr Hans
Published: January 2008

Abstract—

Hypocotyl elongation in mustard (Sinapis alba L.) seedlings is known to be controlled by phytochrome (Pfr) through a threshold response. This phytochrome‐mediated threshold response was studied in detail with the following results: (i) The Pfr threshold value required to suppress hypocotyl growth is much lower (0.03% Prr, based on total phytochrome in the hypocotyl at 36 h after sowing = 100%) than those threshold valued observed previously in threshold control by hook phytochrome of appearance of ‘potential capacity for photophosphorylation’ and lipoxygenase appearance in the mustard cotyledons (1.25% Ptr, based on total phytochrome in the hypocotyl at 36 h after sowing = 100%). This probably explains why hypocotyl elongation is so extremely sensitive to light, (ii) The Pfr threshold value controlling hypocotyl growth is a system constant, independent of total phytochrome content, developmental age and actual growth rate, (iii) Threshold control of hypocotyl elongation is unaffected by the removal of the cotyledons and half of the hook. However, removal of the whole hook totally eliminates any light control over the residual hypocotyl growth, (iv) After termination of the threshold control, the hypocotyl growth rate immediately returns to precisely that found in untreated dark control even though the partial growth rates of the different parts of the hypocotyl are quite different, relative to their dark controls. Obviously, the organ grows as an integrated unit.

It is concluded that the all‐or‐none threshold control over hypocotyl growth is exerted from the plumular hook. It appears that the hook can send off phytochrome all‐or‐none signals in both directions, to the cotyledons and to the hypocotyl.
PHOTOREACTIVATION OF LETHAL DAMAGE AND DAMAGE LEADING TO CHROMATID DELETIONS INDUCED IN G1 PHASE HAMSTER x Xenopus HYBRID CELLS BY UV
Authors: Kulp Susan Q. , Griggs H. Gaston
Published: January 2008

Abstract—

A86 Xenopus cells, cloned from a Xenopus line that exhibited a high level ot photoreacti‐vation of UV‐induced lethal damage, and V79M1 hamster cells, cloned from a hamster line that did not exhibit efficient photoreactivation of such damage, were fused to produce the V79M1 A86 cell line ‐ a hybrid line in which approximately 84% of the cells contained the entire V79M1 and A86 genomes. Ultraviolet and UV plus photoreactivation fluence‐survival relations were then determined and compared for hybrid and parental Gl phase cells in a first attempt to elucidate interactions of the parental genetic potentials for photoreactivation in the hybrid. Specifically, it was anticipated that the combined V79M1 and A86 genomes in the hybrid would produce photoreactivating enzymes sufficient to efficiently photoreactivate UV‐induced lethal damage in both A86 and V79M1 DNA and little difference would be observed in the levels of photoreactivation exhibited by V79M1 A86 and A86 Gl phase cells. To the contrary, the level of photoreactivation observed for the hybrid did not closely approach that observed for the A86 line. To assist in the interpretation of this somewhat unexpected observation, three additional studies were performed: (1) comparison of ‘optimal’ schemes for photoreactivation of UV‐induced lethal damage in the hybrid and parental Gl phase cells, (2) comparison of the effects of some different types of growth medium on photoreactivation of UV‐induced lethal damage in hybrid and parental Gl phase cells, and (3) comparison of the levels of photoreactivation of UV‐induced chromatid deletions in the V79M1 and A86 chromosomes of Gl phase hybrid cells. The results suggested that the relatively low level of photoreactivation of UV‐induced lethal damage manifested by the hybrid cells could be attributed, at least in part, to their inability to efficiently photoreactivate pyrimidine dimers induced in the DNA of their V79M1 chromosomes.
QUANTUM YIELDS FOR LASER PHOTOCYCLIZATION OF BILIRUBIN IN THE PRESENCE OF HUMAN SERUM ALBUMIN. DEPENDENCE OF QUANTUM YIELD ON EXCITATION WAVELENGTH
Authors: McDonagh Antony F. , Agati Giovanni , Fusi Franco , Pratesi Riccardo
Published: January 2008

Abstract—

The quantum yield for laser photocyclization of bilirubin to lumirubin in the presence of human serum albumin (tHLR) was measured at five monochromatic excitation wavelengths in the range 450–530 nm. Solutions used were optically thin throughout the wavelength range and precautions were taken to exclude contributions from photocyclization of bilirubin XHIa impurities. The values obtained (7.2‐18 10‐4) were lower than those previously reported and showed the following wavelength dependence: 457.9 < 488.0 < 501.7 < 514.5 528.7. However, the rate of lumirubin formation, normalized to constant fluence, decreased with wavelength over the same wavelength range and no evidence was found that photoisomerization of bilirubin to lumirubin is faster with green (514.5 or 528.7 nm) than with blue (457.9 or 488.0 nm) light. The stereoselectivity of the configurational isomerization of bilirubin to 4Z,15E and 4E,15Z isomers also was studied. This reaction became less regioselective for the 4Z,15E isomer with increasing wavelength. The observed wavelength dependence of tHLR and of the [4Z,15E]: [4Z,15E] ratio at photoequilibrium are consistent with an exciton coupling model in which intramolecular energy transfer can occur between the two pyrromethenone chromophores of the bilirubin molecule in the excited state. Relative rates of lumirubin formation in vivo at different excitation wavelengths and constant fluence were estimated for different optical thicknesses and for different skin thicknesses. These estimates suggest that the recently reported clinical equivalence of blue and green phototherapy lights probably reflects the marked variation of skin transmittance with wavelength more than wavelength‐dependent photochemistry. The calculations also indicated that the optimal wavelength for phototherapy is probably on the long wavelength side of the bilirubin absorption maximum.
FLUORESCENCE SPECTROSCOPY OF BENZO[a]PYRENE DIOL EPOXIDE‐DNA ADDUCTS. CONFORMATION‐SPECIFIC EMISSION SPECTRA
Authors: Kim Seog K. , Brenner Henry C. , Soh Byoung Joon , Geacintov Nicholas E.
Published: January 2008

Abstract—

The fluorescence characteristics of adducts derived from the covalent binding of the highly tumorigenic (+) and the non‐tumorigenic (‐) enantiomers of trans‐7,8‐dihydroxy‐anti‐9,10‐epoxy‐7,8,9,10‐tetrahydrobenzo[a]pyrene (BPDE) to native calf thymus DNA are significantly different from one another both at room temperature and at 77 K. The ratio R of fluorescence intensities of the (0,0) band I (situated near 380 nm) and vibronic band V (near 400 nm) of the pyrene ring system in the BPDE‐DNA adducts and of the tetraol (BPT) hydrolysis product of BPDE is very sensitive to the polarity of the solvent, thus mimicking the well known behavior of pyrene itself (A. Nakajima, 1971, Bull. Chem. Soc. Jpn. 44, 3272). The fluorescence excitation and emission spectra of the(+)‐BPDE‐DNA adducts are relatively sharp and only slightly red‐shifted (2–3 nm) with respect to those of BPT in aqueous buffer solution, and R= 1.07 when the fluorescence is excited at the maximum of the absorption spectrum; this compares with R= 1.17 for BPT in water, R= 0.75 in ether, and R= 0.84 for noncovalently intercalated BPT. These results suggest that the pyrene ring system in the covalent (+)‐BPDE‐DNA adducts is located in an environment which is relatively exposed to the aqueous environment, while physically intercalated BPT molecules are located at hydrophobic binding sites. The fluorescence characteristics of the (‐)‐BPDE‐DNA adducts are more heterogeneous and thus more complex than those of the (+)‐adducts. The R ratio depends rather strongly on the wavelength of excitation; a minor, more highly fluorescent and relatively solvent‐accessible form of adducts exhibits an R ratio of 1.01. The major, less solvent accessible form is characterized by a larger red shift in the absorption spectrum (10 nm) and emission spectrum (6 nm for the (0,0) band) relative to BPT, and an R ratio of 1.07. These characteristics suggest that the local environments of the pyrenyl residues in the (‐)‐BPDE‐DNA adducts are significantly different from those of BPT bound noncovalently to DNA by the intercalation mechanism. Fluorescence methods, particularly at low temperatures where the bands are better resolved and the fluorescence yields are significantly greater than at room temperature, can also be used to distinguish covalent DNA adducts derived from the binding of (+)‐BPDE and (‐)‐BPDE to native double‐stranded DNA.
REACTIVITY OF CHLOROPHYLL a/b‐PROTEINS AND MICELLAR TRITON X‐100 COMPLEXES OF CHLOROPHYLLS a OR b WITH BOROHYDRIDE
Authors: Scheer Hugo , Porra Robert J. , Anderson Jan M.
Published: January 2008

Abstract—

The reaction of several plant chlorophyll‐protein complexes with NaBH4has been studied by absorption spectroscopy. In all the complexes studied, chlorophyllbis more reactive than Chia,due to preferential reaction of its formyl substituent at C‐7. The complexes also show large variations in reactivity towards NaBH4and the order of reactivity is: LHCI > PSII complex > LHCII > PSI > P700 (investigated as a component of PSI). Differential pools of the same type of chlorophyll have been observed in several complexes.

Parallel work was undertaken on the reactivity of micellar complexes of chlorophyllaand of chlorophyllbwith NaBH4to study the effect of aggregation state on this reactivity. In these complexes, both chlorophyll a andbshow large variations in reactivity in the order monomer > oligomer > polymer with chlorophyllbgenerally being more reactive than chlorophylla.It is concluded that aggregation decreases the reactivity of chlorophylls towards NaBH4in vitro,and may similarly decrease reactivity in naturally‐occurring chlorophyll‐protein complexes.
PHOTOSENSITIZED REACTIONS OF POLY(U) WITH TRIS(2,2′ BIPYRIDYL)RUTHENIUM(II) AND PEROXYDISULFATE
Authors: Tossi Alessandro B. , Görner Helmut , Schulte‐Frohlinde Dietrich
Published: January 2008

Abstract— The reactions of polyuridylic acid [poly(U)] with Ru(bpy)33 [Ru(III)] and SO−4˙, following UV and visible light irradiation of Ru(bpy)23+ [Ru(II)j in the presence of S2O28, were studied in an argon‐saturated aqueous solution using time‐resolved absorption and conductivity methods. The kinetics of the Ru(III) conversion to Ru(II) in the presence of poly(U) was monitored spectroscopically either in the absence of SO−4˙ [rapid mixing with Ru(III)] or in its presence (after laser flash excitation, λexe= 353 nm). The conversion of Ru(III) to Ru(II) is complete at a [nucleotide]/[sensitizer] (N/S) ratio ≥ 10 (rate constant k= 12 s−1) for rapid mixing and at N/S ≥b (k = 15 s−1 at N/S = 10) after laser pulsing. Conductivity measurements following the laser pulse revealed a fast conductivity increase (risetime < 10 µs), due to the formation of charged species and protons. A slower increase in the 0.1–0.5 s range was observed for poly(U) but it is considerably smaller for poly(dU) and absent in uracil containing monounits. The slow increase is unaffected by pH changes in the 3.5'7 range, markedly reduced in the7–9 range and is replaced by a slight decrease in conductivity in buffered solutions. An explanation is that poly(U)‐bound excited Ru(II) reacts with S2O28 forming Ru(III) and SO−4˙ as oxidizing species both of which react with poly(U) bases. The resulting base radicals react with Ru(III) or the ligands in the ruthenium complex, producing protons which give rise to the slow conductivity increase (k = 15 s−1 atN/S = 10). The formation of single‐strand breaks and the ensuing release of condensed counterions does not appear to contribute significantly to the slow conductivity signal. AtN/S < 10 the observed rate and extent of Ru(III) →Ru(II) conversion and of the slow proton production vary markedly with the N/S ratio.
PHOTOCHEMICAL cis/trans ISOMERIZATION OF AN AMPHIPHILIC MEROCYANINE DYE IN HOMOGENEOUS SOLUTION AND REVERSED MICELLES
Authors: Abdel‐Kader Mahmoud H. , Hamzah Riyad Y. , Abdel‐Halim Shakir T.
Published: January 2008

Abstract— In the present study, the photochemical cis⇌trans isomerization of the amphiphilic merocy‐anine dye (4‐hydroxy‐l‐cetyl stilbazolium betaine C16M) is reported. The structure of each isomer is established from high resolution FT 1H‐NMR analysis. The photochemical quantum yields φt→c, and φc→t are determined in methanol and in reversed micelles of the system (CDBA, benzene, water). The quantum yield φc→t increases in reversed micelles compared to that in methanol. The reverse results are obtained for φt→c. The micellar effect on the photochemical trans→cis isomerization will be discussed.
NORMAL BRAIN TISSUE RESPONSE TO PHOTODYNAMIC THERAPY: HISTOLOGY, VASCULAR PERMEABILITY AND SPECIFIC GRAVITY
Authors: Dereski M. O. , Chopp M. , Chen Q. , Hetzel F. W.
Published: January 2008

Abstract— The response of photodynamic therapy on normal brain was investigated in 140 Fisher rats. The rats were injected i.p. with Photofrin II (12.5mg/kg) and 48 h later the dural area over the frontal cortex was photoactivated with red light (630 ± 1 nm) from an argon dye laser. Treatment was performed with optical energy densities of 140 and 70 J/cm2. Histopathology, vascular permeability and specific gravity measurements were conducted on different populations of rats at 4 h, 24 h, 72 h and 1 week after photodynamic therapy (PDT). Histopathology revealed similar gross and microscopic pathology associated with light energies of 70 and 140 J/cm2 after all time points. A large cerebral infarct approximately the size of the brain surface area treated, evolved 24 h following treatment. Evans blue extravasation indicated a small area of vascular permeability evident as early as 4 h following PDT treatment at both energy levels, with increasing permeability evident at later time points. Specific gravity measurements taken on a representative area of the lesion indicated a significant (P < 0.01) amount of edema present at 24 h post treatment with a gradual reduction approaching control values over the time period of] week. The data indicate a significant amount of damage to normal brain from low PDT treatment doses.
THE INFLUENCE OF pH ON THE SPECTROSCOPIC CHARACTERISTICS OF SOME PHENANTHRENIC ALKALOIDS
Authors: Chakraborty S. , Nandi R. , Maiti M. , Achari B. , Bandyopadhyay S.
Published: January 2008

Abstract— The absorption and fluorescence characteristics of aristolochic acid, aristololactam, N‐methyl aristololactam and aristololactam‐ß‐D‐glucoside have been studied at neutral pH. Absorption and fluorescence characteristics of the alkaloids have been evaluated from their UV‐visible spectra, the fluorescence emission and excitation spectra, and quantum yields. The effect of pH in the range 1.0–14.0 on the structure of the alkaloids has also been investigated. A pH dependent reversible change in the absorption and fluorescence spectra is obtained with aristololactam and aristololactam‐ß‐D‐glucoside. It is suggested that the pH dependent properties of aristololactam and aristololactam‐ß‐D‐glucoside are due to the formation of lactam ⇄ lactim and phenanthrenic lactam ⇄ amino phenanthrenic acid, respectively.
POTENTIAL EFFECTS OF UV‐B RADIATION ON MARINE ORGANISMS OF THE SOUTHERN OCEAN: DISTRIBUTIONS OF PHYTOPLANKTON AND KRILL DURING AUSTRAL SPRING
Authors: Bidigare R. R.
Published: January 2008

Increases in UV‐B radiation resulting from ozone depletion during austral spring could potentially alter the balance of the Southern Ocean marine ecosystem. A quantitative assessment ol the effects of UV‐B enhancement requires knowledge of (1) the wavelength‐dependent fluxes of UV‐B in the upper ocean, (2) action spectra for UV‐B damage to Antarctic phytoplankton and zooplankton, and (3) depth‐dependent distributions and residence times of Southern Ocean phytoplankton and zooplankton during austral spring. Unfortunately, only limited data arc currently available to address this impact directly. To provide some of the information required for such an assessment, available data regarding plankton distributions and their photophysiological characteristics have been summarized. A preliminary assessment of the available literature suggests that Antarctic phytoplankton and krill receive very low doses of UV‐B during austral spring. The high spectral attenuation coefficients associated with the environments in which most plankton arc found during springtime precludes the possibility of UV damage. Future research directions are described which should provide a better understanding of the ecological consequences of the “ozone hole” which resides over the Antarctic continent during austral spring.
EFFECTS OF ULTRAVIOLET RADIATION ON THE IMMUNE SYSTEM IN HUMANS
Authors: Morison Warwick L.
Published: January 2008

–In experimental animals, exposure to UV‐B radiation produces selective alterations of immune function which are mainly in the form of suppression of normal immune responses. This immune suppression is important in the development of nonmelanoma skin cancer, may influence the development and course of infectious disease and possibly protects against autoimmune reactions. The evidence that this form of immune suppression occurs in humans is less compelling and very incomplete. The wavelengths of radiation most affected by a depletion of the stratospheric ozone layer are those known to be most immunosuppressive in animals and it is likely that such depletion will increase any suppressive effect of sunlight on immunity in humans. In addition to establishing whether or not UV‐B radiation can cause suppression of immune function in humans, studies are required to determine if melanin can provide protection against such suppression, the role of this suppression in the pathogenesis of skin cancer, the development of infectious disease and vaccine effectiveness, and the capacity for humans to develop adaptive, protective mechanisms which may limit damage from continued exposure to UV‐B radiation.
EFFECTS OF ULTRAVIOLET LIGHT ON THYMIDINE INCORPORATION AND DNA CHAIN ELONGATION IN PHOTOREACTIVABLE INSECT CELLS
Authors: Styer Susan C. , Meechan Paul J. , Griffiths T. Daniel
Published: January 2008

–An insect cell line, IAL‐PID2, was exposed to UV and analyzed for its ability to incorporate [3H]‐thymidine and to elongate replicon‐sized DNA fragments. After exposure to 5 or 10 J/m2 UV, the cells exhibited a rapid and prolonged depression in the rate of thymidine incorporation. Photoreactivation reduced this depression but did not entirely reverse it. For exposures of 5 J/m2 or above, full recovery did not occur until 18 h after exposure. The blockage of fork progression after UV exposure was fluence‐dependent, with replication segments after exposure to 20 J/m2 being shorter than those observed after exposure to 10 J/m2. Immediately after exposure to either 10 or 20 J/m2, photoreactivation reversed blockage of fork progression, indicating that the (5–6) cyclobutyl pyrimidine dimer is responsible for blockage. This also indicates that blockage of fork progression may not be the only factor responsible for the prolonged depression seen in thymidine incorporation. Three hours after exposure to either 10 or 20 J/m2, replication segments were still significantly shorter than control segments. Photoreactivation completely reversed blockage after exposure to 10 J/m2, but did not completely reverse blockage after exposure to 20 J/m2, indicating that at such fluences, other lesions may play a role in UV‐induced blockage of fork progression.
EFFECTS OF SOLAR RADIATION ON DEVELOPMENT IN THE CELLULAR SLIME MOLD, Dictyostelium discoideum
Authors: Häder Donat‐P. , Hader Maria
Published: January 2008

–The effect of solar radiation on development was studied in two strains (wild type N04 and axenic AX2) of the cellular slime mold, Dictyostelium discoideum. In both strains early development was retarded by solar radiation and amoebae exposed for >200 min never developed into mature sorocarps. Overheating can be excluded as a mechanism for inhibition since the organisms were exposed in a temperature‐controlled growth chamber. The most effective component seems to be UV‐B radiation (while UV‐A has a smaller inhibitory effect) as shown by cutting off shorter wavelength radiation using WG filters.
INTRAMOLECULAR FLUORESCENCE QUENCHING IN COVALENT ACRYLAMIDE‐INDOLE ADDUCTS
Authors: EFTINK MAURICE R. , JIA YI‐WEI , GRAVES DAVID E. , WICZK WIESLAW , GRYCZYNSKI IGNACY , LAKOWICZ JOSEPH R.
Published: January 2008

Abstract— Indole derivatives have been prepared which have a covalently linked quencher, acrylamide. One of these adducts, N‐acrylyltryptamine, has a flexible linkage and the other, N‐acrylyl‐1,2,3,4‐tetrahydropyridoindole, has a rigid bridge between indole and the quencher. The intensity decays of these adducts were obtained using multi‐frequency phase and modulation fluorometry. The fluorescence of these adducts appears to be dynamically quenched; dominant lifetimes of 64 ps and 31 ps are found for the flexible and rigid adducts. This indicates that very rapid intramolecular quenching occurs, even when the quencher and fluorophore cannot collide. Quenching in the rigid molecule probably involves electron transfer through two sigma bonds. Anisotropy decay data were also collected and rotational correlation times of 62 ps and 163 ps are reported for the flexibile and rigid adducts, respectively.
PHOTOCHEMISTRY OF PHYCOBILIPROTEINS: RECIPROCITY OF REVERSIBLE PHOTOCHEMISTRY AND AGGREGATION IN PHYCOERYTHROCYANIN FROMMastigocladus laminosus
Authors: SIEBZEHNRÜBL S. , FISCHER R. , KUFER W. , SCHEER H.
Published: January 2008

Abstract—(a) Native PEC from the cyanobacterium,Mastigocladus laminosus, and its isolated α‐subunit show photoreversibly photochromic reactions with difference‐maxima around 502 and 570 nm in the spectral region of the α‐84 phycoviolobilin chromophore. (b) Native PEC and its β‐subunit show little if any reversible photochemistry in the 600–620 nm region, where the phycocyanobilin chromophores on the β‐subunit absorb maximally, (c) Reversible photochemistry is retained in ureadenatured PEC at pH = 7.0 or pH ≤ 3. The difference maxima are shifted to 510 and 600 nm, and the amplitudes are decreased. An irreversible absorbance increase occurs around 670 nm (pH ≤ 3). (d) The amplitude of the reversible photoreaction difference spectrum is maximum in the presence of 4–5Murea or 1MKSCN, conditions known to dissociate phycobiliprotein aggregates into monomers. At the same time, the phycocyanobilin chromophore(s) are bleached irreversibly, (e) The amplitude becomes very small in high aggregates, e.g. in phycobilisomes. (f) In a reciprocal manner, the phototransformation of native PEC leads to a reversible shift of its aggregation equilibrium between trimer and monomer. The latter is favored by orange, the former by green light, (g) It is concluded that the phycoviolobilin chromophore of PEC is responsible for reversible photochemistry in PEC, and that there is not only an influence of aggregation state on photochemistry, but alsovice versaan effect of the status of the chromophore on aggregation state. This could constitute a primary signal in the putative function as sensory pigment, either directly, or indirectlyviathe release of other polypeptides,viaphotodynamic effects, or the like.