bluuebunny/crossref_metadata_2025 huggingface dataset:
DYNAMIC FLUORESCENCE OF TRYPTOPHANYL RESIDUES IN LOW MOLECULAR WEIGHT MODEL COMPOUNDS AND PROTEINS
Authors: Bismuto Ettore , Irace Gaetano
Published: January 2008

Abstract—

The tryptophanyl fluorescence decay of tuna apomyoglobin, a protein containing a single indole residue, has been compared to that of the monomeric tryptophanyl residue (NATA) in order to discriminate the effect determined by the protein matrix from those induced by physical and chemical agents. The fluorescence decay, obtained in the frequency domain, has been analyzed in terms of lifetime distributions having a Lorentzian shape. The results indicate that the incorporation of the chromophore into the protein matrix determines a broadening of the distribution pattern.

A further increase of the distribution width has been observed on guanidine‐induced unfolding of the protein, whereas no effect has been detected for NATA in the presence of guanidine at concentrations as high as 6.0 M. These observations lead to the conclusion that the tryptophanyl fluorescence lifetime is influenced by the protein matrix even in the fully unfolded state.

The increase of temperature from 20 to 45oC produces an enlargement of the distribution width of NATA and unfolded tuna apomyoglobin. In the same thermal range, the native protein exhibits a narrowing of the tryptophanyl lifetime distribution. This different behaviour has been explained in terms of a larger distribution of microenvironmental states, generated by the chromophore‐solvent interaction (which is very limited in the native protein), at higher temperature.

This conclusion has been further corroborated by the observation that a temperature increase changes the weight of the various components which contribute to the total emission of the free amino acid tryptophan.
RELATIVE REPAIR OF ADENOVIRUS DAMAGED BY SUNLAMP, UV AND γ‐IRRADIATION IN COCKAYNE SYNDROME FIBROBLASTS IS DIFFERENT FROM THAT IN XERODERMA PIGMENTOSUM FIBROBLASTS
Authors: Rainbow Andrew J.
Published: January 2008

Abstract—

The DNA repair capacities of three unrelated Cockayne syndrome(CS) fibroblast strains were compared to that of three unrelated xeroderma pigmentosum(XP) strains for three different DNA damaging agents using a sensitive host cell reactivation(HCR) technique. Adenovirus type 2(Ad 2) was treated with either UV light, γ‐rays or sunlamp‐irradiation and subsequently assayed for its ability to form viral structural antigens(Vag) in the CS and XP strains using immunofluorescent straining. D37 values for the survival of Ad 2 Vag synthesis in the CS and XP strains, expressed as a percentage of those obtained in normal strains, were used as a measure of DNA repair capacity. Percent HCR values in the XP strains XP25RO, XP2BE and XP5BE respectively were lowest for UV(6, 14 and 6%), intermediate for sunlamp‐irradiation(18, 32 and 10%) and highest for 7‐irradiation(65, 61 and 60%), whereas for the CS strains CS1BE, CS3BE and CS278CTO respectively, percent HCR values were lowest for UV (26, 30 and 34%), intermediate for γ‐irradiation(61, 64 and 69%) and near normal for sunlamp‐irradiation(82, 73 and 89%). These results suggest that the spectrum of lesions' which is defectively repaired in CS is not the same as that which is defectively repaired in XP.
MEASUREMENT OF INDUCTION PERIODS IN INHIBITED FREE‐RADICAL OXIDATION BY INFRARED CHEMILUMINESCENCE AT 1270 nm
Authors: Lee S. H. , Niu Q. , Sheng X. C. , Mendenhall G. D.
Published: January 2008

Abstract—

Infrared chemiluminescence at 1.27 µ. appears after the consumption of phenolic inhibitors in solutions of 1‐tetralyl hydroperoxide in tert‐butylbenzene (BPh), initiated with di‐tert‐butyl hyponitrite (BHN) at 68oC. The induction periods with phenols were in excellent agreement with ones calculated from rates of decomposition of the initiator. Di‐(2,2,6,6‐tetramethyl‐4‐piperidinyl) sebacate, benzhyd‐rol, a derivative of benzhydrol, and di‐rerr‐butyl ketoxime under these conditions showed no inhibition or a weak effect. Initiated solutions 2.5 mM in p,p′‐di‐tert‐octyldiphenylamine showed no detectable emission at 1270 nm because of efficient quenching of 1O2 by diaryl nitroxides formed from the amine, and because the oxidation products of the amine are peroxy scavengers (Thomas, J. R. 1960, J. Amer. Chem. Soc. 82, 5955). The relative yields of IR luminescence from several alkyl hydroperoxides and oxygen‐hydrocarbon mixtures, initiated in each case by BHN, were found to vary substantially with the structure of the hydrocarbon and with the solvent.
A POSSIBLE CONTROL BY A PHYTOCHROME‐LIKE PHOTORECEPTOR OF CHLOROPHYLL SYNTHESIS IN THE GREEN ALGA Ulva rigida
Authors: Loapez‐Figueroa F. , Niell F. X.
Published: January 2008

Abstract—

Chlorophyll synthesis is stimulated by red light pulses in the green alga Ulva rigida C. Aghard. Chlorophyll synthesis in darkness is greater after longer red light pulses (30 min) than after shorter red light pulses (5 min). Chlorophyll synthesis was higher after red light pulses of 14 Wm‐2 fluence rate than after those of 7 Wm‐2. The effect of red light showed some far‐red reversibility. The reversion by far‐red light was higher after red light pulses of 4 min than after those of 30 min. These results indicate the existence of a rapid induction of chlorophyll synthesis during the red light pulses and a fast escape from photoreversibility. The percentage of reversion is also affected by the fluence rate of the light pulses. The reversion was reduced by about 15% when the photon fluence rate was increased from 7 to 14 Wm‐2. Reversion was also observed when red and far‐red light pulses were applied successively. Thus, phytochrome or a phytochrome‐like photoreceptor could be involved in the induction of chlorophyll synthesis in Ulva rigida.
PROBING THE STRUCTURE OF HPD BY FLUORESCENCE SPECTROSCOPY
Authors: Kessel David
Published: January 2008

Abstract—

Fluorescence emission spectra indicate that oligomers containing both hematoporphyrin and its dehydration products (vinyl porphyrins) comprise the tumor‐localizing fraction of HPD. In the relatively polar solvent methanol, the vinyl porphyrins exhibit reduced fluorescence yields while the hematoporphyrin residues are relatively resistant to fluorescence quenching by Fe+3. In the less polar solvent tetrahydrofuran, fluorescence from oligomeric vinyl porphyrins was enhanced, and Fe+3‐induced quenching of oligomeric hematoporphyrin promoted. These, together with other studies in biological systems, suggest a substantial degree of interaction among the porphyrin units contained in these oligomers, as a function of the polarity of the environment.
CONVEX CURVATURES OF ALKALINE ELUTION PROFILES OF DNA FROM HUMAN CELLS IRRADIATED WITH 405 nm UVA: EVIDENCE FOR INDUCTION OF SLOWLY DEVELOPING ALKALI‐LABILE SITES
Authors: Peak Meyrick J. , Peak Jennifer G.
Published: January 2008

Abstract—

The alkaline (pH 12.1) elution profiles of DNA from human P3 cells exposed to monochromatic 405 nm UVA radiation deviate from exponential: on a logarithmic plot of eluted fraction of DNA vs time of elution, the rate of elution accelerates for the first 6 h. Following this period, the profiles become exponential. In contrast, the elution profiles of DNA after 520 nm green light or ionizing radiation exposures (x‐ and gamma rays, and fission spectrum neutrons) are always strictly exponential, evidence that the convex profiles were not due to an artifact caused by elution technique. Holding the DNA at pH 12.1 for 6 h after 405‐nm exposures before initiating elution resulted in profiles that were close to exponential, with slopes similar to the final slopes observed following the 6‐h elution period in the original experiments. This is evidence that some DNA breaks develop slowly during the first 6 h of elution, as a result of exposure to alkali. Therefore, the DNA lesions induced by 405‐nm light as measured by the alkaline elution technique are apparently heterogeneous and include a major class of alkali‐labile sites that develop slowly during incubation at pH 12.1. Convex profiles also occur following exposure of the cells td visible light at 434 and 512 nm.
RAPID EQUILIBRATION OF OXYGEN IN FLUORESCENCE QUENCHING REACTIONS
Authors: Eftink Maurice R. , Ghiron Camillo A.
Published: January 2008

Abstract—

A simple means is described for the rapid equilibration of oxygen in fluorescence quenching reactions. This involves bubbling the gas through experimental solutions. With this procedure, data for Stern‐Volmer plots can be obtained in 1–2 h, without bubbling it takes approximately ten times as long to collect such data.
AUTOINDUCTION AND ALDEHYDE CHAIN‐LENGTH EFFECTS ON THE BIOLUMINESCENT EMISSION FROM THE YELLOW PROTEIN ASSOCIATED WITH LUCIFERASE IN Vibrio fischeri STRAIN Y‐1b
Authors: CHO Ki Woong , Colepicolo Pio , Hastings J. Woodland
Published: January 2008

Abstract— A new strain of the yellow‐light emitting bacterium Vibrio fischeri Y‐lb, possessing a higher fraction of its emission in the yellow, was isolated and characterized. The in vivo yellow to blue ratio (Y/B) increases during growth in parallel with the autoinduction of luciferase, reaching a value above 5 at 17°C. This Y/B increase is attributed to concomitant increases in the intracellular levels of both luciferase and the specific protein associated with yellow emission, the yellow fluorescent protein (YFP), and to the association of the two proteins at higher concentrations. The yellow emission is rapidly but reversibly lost by brief exposures to a temperature of 27°C (5 s), and irreversibly so at 40°C, attributed to dissociation of the two proteins. A concentrated crude extract emits almost exclusively yellow light in the in vitro reaction, and theY/B ratio decreases with dilution. The Y/B ratio in vitro is also dependent on the aldehyde chain length; experiments with aldehyde analogs suggest that the aldehyde binding site of luciferase must be occupied for YFP to stimulate light emission.
INCREASING INCIDENCE OF CUTANEOUS MELANOMA, ULTRAVIOLET RADIATION AND THE CLINICIAN
Authors: Cascinelu Natale , Marchesini Renato
Published: January 2008

–Incidence of melanoma is certainly rising all over the world and this observation has been related to a more frequent and prolonged exposure to the rays of the sun.

The authors critically review pertinent literature and conclude that descriptive epidemiology of melanoma does not give survival trends and does not support the claim that melanoma is ultraviolet (UV) dependent. Analytical epidemiology has not reached a consensus on this aspect.

Experimental data available are also difficult to interpret because there are consistent differences of susceptibility to UV among different animals, among lamps used and methods of measuring employed in various laboratories.

Information available shows that the maximal relative biological activity of UV in humans is at about 305 nm. This evaluation greatly depends on (1) thickness of the skin, (2) the quantity and quality of secretions that cover the skin, (3) cleaness of the skin, (4) the latitude, (5) the weather, (6) the hour of the day and (7) the presence of chemical carcinogens in the air and on the skin.

The authors stress the importance of the criteria of clinical diagnosis recently introduced in clinical practice and higher public awareness as the causes of the increasing incidence of melanoma.
PHOTOCHEMISTRY OF POLYFUNCTIONAL MOLECULES. DEVELOPMENT OF ANTENNA CHROMOPHORES FOR SELF‐SENSITIZED PHOTOREDUCTION OF KETONES*
Authors: Wu Zheng‐Zhi , Morrison Harry
Published: January 2008

–Model systems are reported which test the efficacy of potential aryl antenna groups designed to harvest photons and subsequently transfer electronic energy to a target ketone through singlet‐singlet energy transfer. The model series consists of 4‐aryl substituted cyclohexanones where the aryl groups are benzyloxy (5a), benzoyl (5b), and dimethylphenylsiloxy (5c). In each case, photolysis of isopropyl alcohol solutions of the substrate with 254 nm light results in photoreduction of the ketone to the corresponding alcohols, 6a‐6c. The most efficacious sensitizing antennae are the benzyloxy and dimethylphenylsiloxy chromophores, with quantum efficiencies for reduction equal to 0.57 and 0.48, respectively. Photophysical and photochemical studies on 5a confirm that energy transfer to the ketone is intramolecular with the rate constant for energy transfer estimated at 2.4 × 100 s‐1.
FORMATION OF PURINE PHOTOPRODUCTS IN A DEFINED HUMAN DNA SEQUENCE
Authors: GALLAGHER PATRICIA E. , DUKER NAHUM J.
Published: January 2008

Abstract

The formation of DNA base damages by broad spectrum ultraviolet irradiation (250–400 nm) was investigated using a defined sequence of human DNA. The irradiated, 92 base pair, 3‐end of the human alphoid segment was incubated with an enzyme fraction purified from bacteriophage T4‐infected E. coli. As previously reported, analysis of reaction products by sequencing gels showed enzymic incision of purine‐containing photoproducts as well as pyrimidine cyclobutane photodimers. The purine‐incising activity does not require metal ions and was unaffected by β‐mercaptoethanol or dithiothreitol. The formation of the purine photoproducts is independent of buffer; these lesions are produced by irradiation of DNA in Tris, Hepes or phosphate buffers. They are produced at biologically significant wavelengths between 260 to 300 nm. Only low levels were detected above or below this range. The formation of purine photoproducts is dose dependent with similar yields at some specific loci to pyrimidine dimers. These results suggest that purine‐containing photoproducts could be of consequence in ultraviolet carcinogenesis.
EXPOSURE OF MICE TO UV‐B RADIATION SUPPRESSES DELAYED HYPERSENSITIVITY TO Candida albicans
Authors: DENKINS YVONNE , FIDLER ISAIAH J. , KRIPKE MARGARET L.
Published: January 2008

Abstract

Groups of mice were exposed to a single dose of UV radiation before or after immunization with Candida albicans. The delayed type hypersensitivity (DTH) response was markedly depressed in all UV‐irradiated groups. Exposure of mice to UV radiation before sensitization induced splenic suppressor cells that, upon transfer to normal recipients, impaired the induction of DTH to Candida. In contrast, exposure of mice to UV radiation after sensitization interfered with elicitation of the DTH response, but this suppression was not transferable. These studies demonstrate that immunity to Candida albicans in mice is impaired by exposure to UV radiation and that two separate mechanisms may be involved.
THE DIRECT OBSERVATION OF A PSORALEN‐THYMINE UVA INDUCED SOLID‐STATE CYCLOADDITION REACTION PRODUCT BY SINGLE‐CRYSTAL x‐RAY DIFFRACTOMETRY
Authors: PFLUGER C. E. , OSTRANDER R. L.
Published: January 2008

Abstract— Single‐crystal x‐ray diffraction methods have been used to directly observe and simultaneously determine the molecular structure of the UVA induced cis‐syn photocycloaddition product in a partially photolyzed single crystal of a psoralen(pyrone ring side)‐DNA(thymine) interaction model compound, 1 ‘‐(8‐oxypsoralen)‐8’(thym‐l“yl)3‘,6’‐dioxaoctane.
THE ENZYMOLOGY AND MOLECULAR BIOLOGY OF THE Ca2+‐ACTIVATED PHOTOPROTEIN, AEQUORIN
Authors: CORMIER MILTON J. , PRASHER DOUGLAS C. , LONGIARU MAT , MCCANN RICHARD O.
Published: January 2008

Abstract— Aequorin is a bioluminescent protein, isolated from the hydromedusan Aequorea victoria. A recombinant cDNA plasmid (pAEQl) was shown to encode apoaequorin by detecting photoprotein activity in an extract of an E. coli strain containing pAEQl (Prasher et al., 1986, Biochem. Biophys. Res. Comm. 126, 1259–1268). The nucleotide sequence of the pAEQl insert has been determined and is shown to differ significantly from the aequorin cDNA (AQ440) isolated by Inouye et al. (1985, Proc. Natl. Acad. Sci. USA 82, 3154–3158). Comparisons of the coding regions of the two cDNAs show there are 52 nucleotide differences, 19 of which are responsible for 18 amino acid replacements. These differences explain the microheterogeneity observed at 17 positions during the sequencing of native apoaequorin.

Five aequorin isotypes extracted from Aequorea tissue are observed on 2‐dimensional gels and the E. coli‐expressed apoaequorin is shown to co‐migrate with one of these isotypes. The multiple isotypes could be caused by the presence of a multi‐gene family since Southern blot analysis of Aequorea DNA suggests the presence of a minimum of four aequorin genes. Immunoblot analysis suggests that purified native aequorin is proteolytically cleaved during its purification from Aequorea. Comparison of the deduced cDNA translations and the protein sequence suggests the loss of seven residues from the amino terminal.

Overexpression of the apoaequorin cDNA in E. coli now provides the means of obtaining gram quantities of a single isotype of the protein which can be converted to aequorin in the presence of coelenterate luciferin, oxygen and an appropriate thiol. Proper extraction procedures and a single chromatographic step provides apoaequorin which is >95% homogeneous.
CHRONIC ULTRAVIOLET B RADIATION‐INDUCED BIOCHEMICAL CHANGES IN THE SKIN OF HAIRLESS MICE*
Authors: Chatterjee Ranjit , Benzinger Mark J. , Ritter Jayne L. , Bissett Donald L.
Published: January 2008

Abstract— Skh:HR‐l hairless mice were irradiated chronically with sub‐erythemal doses of UVB radiation, and a number of biochemical parameters in the skin were determined after 6,12, 18, and 24 wk of exposure. The parameters measured were water, collagen, elastin, and glycosaminoglycan content; collagenase and elastase levels; and Bz‐Tyr‐OEt (7V‐benzoyl‐L‐tyrosine ethyl ester) and BAPNA (alpha‐N‐benzoyl‐DL‐arginine‐p‐nitroanilide) hydrolyzing activities. Data for UVB radiation‐exposed and chronological age‐matched control mice were compared with respect to unit area and to unit mass of skin. On a unit area of skin basis, UVB radiation exposure increased the level of most parameters. The particular exceptions were collagen and collagenase which remained constant. On a mass of skin basis, though, there is an apparent decrease in collagen content because of the increase in the other skin components. This suggests that there is insufficient collagen in UVB radiation‐exposed skin to support the increasing mass of the tissue.
THE USE OF STOKES RAMAN SCATTERING IN TIME CORRELATED SINGLE PHOTON COUNTING: APPLICATION TO THE FLUORESCENCE LIFETIME OF TYROSINATE*
Authors: Willis Kevin J. , Szabot Arthur G. , Krajcarski Donald T.
Published: January 2008

Abstract— The decay kinetics of the tyrosinate form of tyrosine in aqueous solution, pH 11, were investigated by time correlated single photon counting using laser excitation. The lifetime of the single exponential decay was 30.5 ± 0.2 ps. Stokes Raman scattering was used to determine the instrument response function and the advantages of this approach over the conventional Rayleigh scattering method are discussed.
QUATERNARY STRUCTURE OF PEA PHYTOCHROME I DIMER STUDIED WITH SMALL‐ANGLE X‐RAY SCATTERING and ROTARY‐SHADOWING ELECTRON MICROSCOPY
Authors: Nakasako Masayoshi , Wada Masamitsu , Tokutomi Satoru , Yamamoto Kotaro T. , Sakai Jun , Kataoka Mikio , Tokunaga Fumio , Furuya Masaki
Published: January 2008

Abstract— The quaternary structure of pea phytochrome type I (PI) dimer in the red‐light‐absorbing form was studied by small‐angle X‐ray scattering (SAXS) technique and rotary‐shadowing electron microscopy. Structural parameters for PI 114 kDa chromopeptide dimer and its tryptically digested N‐terminal 59 kDa chromopeptide monomer, such as average electron density, molecular volume and the second moment of electron density distribution, were determined in terms of SAXS using the contrast variation method. Furthermore, by means of model simulation for the scattering profiles of the chromopeptides, most plausible structural models for both peptides were constructed. The distance between the chromophoric domains was estimated to be about 70 A in the resultant model for 114 kDa chromopeptide dimer. Furthermore, the model was consistent with the electron‐micrographic images of both the intact PI dimer and the PI 114 kDa chromopeptide dimer, so that the N‐terminal 7 kDa fragment did not significantly contribute the low‐resolution images of the dimer.
FLUORESCENCE QUANTUM YIELDS OF 124‐kDa PHYTOCHROME FROM OAT UPON EXCITATION WITHIN DIFFERENT ABSORPTION BANDS
Authors: Colombano Claudio G. , Braslavsky Silvia E. , Holzwarth Alfred R. , Schaffner Kurt
Published: January 2008

Abstract— A fluorescence quantum yield (emission at650–850 nm) of π= (2.3 ± 0.3)10−3 was measured for the red‐absorbing form (Pr) of 124‐kDa phytochrome from etiolated oat seedlings (Avena sativa) upon excitation in the Soret band at Λexc= 380 nm. The small difference between this value and the previously determined quantum yield with Λexc= 640 nm, π= (3.5 ± 0.4)10−3is attributed to a blue‐absorbing emitter responsible for the “anomalous” or “blue” emission of the chromoprotein in the region from ca. 400 to 550 nm. The absorption of Pr at 380 nm is consequently somewhat lower than that measured directly from the spectrum. Processes from upper excited states of the Pr phytochromobilin‐derived chromophore other than rapid relaxation to the emitting state are not important. A quantum yield of Φ ' 1.2 times 10−3 is estimated for the blue fluorescence. The proportion of the blue emitters relative to Pr appears to be relatively high.
THE PHOTOSYNTHETIC APPARATUS OF Acetabularia mediterranea GROWN UNDER RED OR BLUE LIGHT. BIOPHYSICAL QUANTIFICATION and CHARACTERIZATION OF PHOTOSYSTEM II and ITS CORE COMPONENTS
Authors: Schmid R. , Fromme R. , Renger G.
Published: January 2008

Abstract— The photosynthetic activity of white light‐grown Acetabularia mediterranea Lamouroux (=A. acetabulum (L.) Silva) decreases under continuous red light to less than 20% within 3 weeks. Subsequent blue light reactivates photosynthesis within a relatively short period of 3 days. In a former publication (Wennicke and Schmid, Plant Physiol.84,1252–1256, 1987) we have shown that the regulated rate limiting step, which is an immediate light driven reaction, is part of photosystem II (PS II). The following biophysical properties of PS II were analyzed in thylakoids isolated from algae grown 3 weeks under either blue or red light with or without subsequent 3 days of blue light illumination: (a) fluorescence induction in the short time domain dominated by QA reduction, (b) the slow fluorescence decline reflecting pheophytin photoaccumulation, (c) absorption changes at 320 and 830 nm under repetitive flash excitation as indicator for the turnover of QA and P680, respectively, (d) oscillation pattern of the oxygen yield by a flash train in dark adapted samples and (e) the binding capacity for atrazine. None of these PS II functions were severely affected, but a minor impairment of20–30% was observed in the thylakoids from algae grown for 3 weeks in red irradiation. The changes do not fully account for the drastic reduction of the electron transport through PS II which was 80% after red light treatment. Therefore, the regulated rate‐limiting step appears to not be mainly located in the PS II core complex itself. It seems likely that the regulation process predominantly comprises the antenna system.
LIGHT‐INDUCED CHANGES IN THE VESICULAR APPARATUS OF Phycomyces SPORANGIOPHORES DURING THE PHOTOTROPIC RESPONSE
Authors: Morales M. , Ruiz‐Herrera J.
Published: January 2008

Abstract— We studied the ultrastructure of laterally illuminated stage I sporangiophores of Phycomyces blakesleeanus to determine whether the phototropic response had any structural correlate. Stimulated sporangiophores conserved the distinctive division into the four longitudinal zones described for state I, and showed no significant differences in the distribution of major organelles in the sides proximal and distal to the light source. On the other hand, apical vesicles were asymmetrically distributed, being present in lower numbers in the faster growing (distal) side of the sporangiophore. We suggest that this asymmetrical distribution reflects the differential utilization of vesicles necessary to sustain the corresponding growth rate of each side. Illumination therefore, must affect the rate of vesicle migration and utilization, more than their rate of synthesis.
ISOLATION and CHARACTERIZATION OF A SUBUNIT FORM OF THE B875 LIGHT‐HARVESTING COMPLEX FROM Rhodobacter capsulatus
Authors: Heller Barbara A. , Loach Paul A.
Published: January 2008

A structural subunit (called B816) has been isolated from the B875 light‐harvesting complex of Rhodobacter capsulatus using a detergent‐mediated dissociation of chromatophores. Rb. capsulatus MW442 (B800–850− B875+ car+) chromatophores were extracted with benzene and titrated with octyl glucoside (OG) to shift the near‐infrared absorption maximum from 873 to 816 nm. Gel filtration chromatography was then used to separate B816 from reaction centers. B816 could be quantitatively shifted back to a B875‐like form (lemax= 875 nm) by decreasing the OG concentration. A similar B816 species could be isolated in low yield from wildtype (B800–850+ B875+ car+) cells but not from SB203E (B800–850− B875 + car−). In the latter case, the B816 subunit seemed too unstable to be isolated under equivalent conditions. The α: β polypeptide ratio, the CD spectrum, and the ability to reversibly dissociate B816 to free bacteriochlorophyll and α‐ and β‐polypeptides were found to be similar to those of the B820 subunit of Rs. rubrum previously reported by our laboratory.
SPECTRAL SENSITIZATION OF SnO2 THIN FILM ELECTRODE BY THE J‐AGGREGATE OF CYANINE DYES IN MONOLAYERS
Authors: Haraguchi Akira , Yonezawa Yoshiro , Hanawa Ryotaro
Published: January 2008

Abstract—

Arachidic acid monolayers containing 5,6,5′,6′‐dibenzo‐I,I‐diethyl‐2,2′‐cyanine chloride were prepared by the spreading method and deposited on the SnO2 surface using the Langmuir‐Blodgett technique. The SnO2 : dye assembly prepared in this manner was used as a photoelectrode of the conventional electrochemical cell. A distinct J‐band was observed in the action spectra of sensitized anodic and cathodic photocurrents. Effects of calcium arachidate barriers inserted between dye layer and either SnO2 electrode (inside barrier) or electrolyte solution (outside barrier) on the photocurrent were examined. Although the inside barrier was effective in decreasing both anodic and cathodic photocurrents, the outside barrier did not suppress cathodic photocurrent. The following mechanism involving a molecular exciton of the J‐aggregate is proposed for the sensitized photocurrent. The anodic photocurrent is caused by hole trapping by some reducing agent and concomitant injection of the electron from molecular exciton to the conduction band of SnO2. Extraction of conduction‐band electron of SnO2 by molecular exciton and supplying to some oxidizing agent such as dissolved oxygen are responsible for the cathodic photocurrent.
HYDROGEN BONDING AND PHOTOTAUTOMERISM OF 3‐METHYLLUMICHROME
Authors: Szafran Magdalena M. , Koziot Jacek , Heelis Paul F.
Published: January 2008

Abstract—

The spectral changes of 3‐methyllumichrome in 1,2‐dichloroethane upon addition of hex‐afluoroisopropanol, trifluoroacetic acid and acetic acid as hydrogen donor agents, have been defined. In the presence of 0.8Mhexafluoroisopropanol, the absorption and fluorescence emission spectra of 3‐methyllumichrome in 1,2‐dichloroethane acquire features nearly identical to those observed in aqueous solution. Therefore, hexafluoroisopropanol can be considered as a model compound for studies on hydrogen bonding of alloxazine derivatives in nonpolar media. The observed spectral changes upon addition of trifluoroacetic acid are caused mainly by protonation. The presence of hydrogen bonded and protonated forms of 3‐methyllumichrome has been checked by means of excitation spectra. The addition of acetic acid causes minor hydrogen bonding effects but gives rise to the phototautomery with an efficiency of one order of magnitude higher in 1,2‐dichloroethane than previously observed in methanol or dioxane. The isoalloxazinic emission band appears at about 495 nm and shifts bathochromically to 540 nm upon increasing acetic acid concentration, probably due to the opening of the primary cyclic structure between 3‐methyllumichrome and acetic acid. The fluorescence emission spectra can be resolved using lognormal approximation into three bands, one ascribed to the alloxazinic form (maximum at about 440 nm) and the others to isoalloxazinic species (maxima at about 495 and 540 nm). The excitation spectra confirm the presence of two excited alloxazinic forms, one solvated by 1,2‐dichloroethane with emission at 435 nm and T ˜1 ns, and the second bonded with acetic acid, bathochromically shifted with T ˜5 ns and able to phototautomerize. The sum of excitation spectra of both forms in suitable proportion reconstructs the absorption spectra of 3‐methyllumichrome in 1,2‐dichloroethane and acetic acid.
ULTRAVIOLET LIGHT INDUCES DOUBLE‐STRAND BREAKS IN DNA OF CULTURED HUMAN P3 CELLS AS MEASURED BY NEUTRAL FILTER ELUTION
Authors: Peak Jennifer G. , Peak Meyrick J.
Published: January 2008

Abstract—

Neutral filter elution at pH 7.2 and 9.6 was used to measure the induction of DNA lesions in human P3 teratocarcinoma cells by monochromatic 254‐, 270‐, 313‐, 334‐, 365‐, and 405‐nm radiation and by 60gamma rays. In this assay DNA double‐strand breaks (dsb) increase the rate of elution of DNA from cell lysates on a filter. Yields of dsb as measured by this procedure were determined by using a calibration of the assay that correlates elution parameters with number of dsb caused by disintegration of 125I incorporated into the DNA. Analysis of fluence responses obtained by using the calibrated assay indicated that the number of dsb induced per dalton of DNA as measured by this assay is proportional to the square of the fluence at all the energies of radiation studied, implying that the induction of these lesions may be a two‐hit event. Analysis of the relative efficiencies for the induction of dsb by ultraviolet radiation, corrected for quantum efficiency, revealed a spectrum that coincided closely with that for the induction of single‐strand breaks (ssb) in the same cells, having a close fit with the spectrum of nucleic acid in the UVC and UVB region below 313 nm, and a shoulder in the UVA region. It was calculated, however, that there may be too few ssb for dsb to result from randomly distributed closely opposed ssb.
CHARACTERIZATION OF RAD4 GENE REQUIRED FOR ULTRAVIOLET‐INDUCED EXCISION REPAIR OF Saccharomyces cerevisiae PROPAGATED IN Escherichia coli WITHOUT INACTIVATION
Authors: Choi In Soon , Kim Jae Bum , Lee Kee Nyung , Park Sang Dai
Published: January 2008

Abstract—

The previously isolated RAD4 gene designated as pPCl from the genomic library of Saccharomyces cerevisiae (Yoon et al., 1985, Korean J. Genetics 7, 97–104) appeared to propagate in Escherichia coli and yet retained its complementing activity to rad4 mutants without inactivation. The subcloned RAD4 gene was found to be localized within a 2.5 kb DNA fragment flanking Bg/II and Bam HI sites in the insert DNA, and was shown to have the same restriction map as a yeast chromosomal DNA, as determined by Southern hybridization. Tetrad analysis and pulse‐field chromosome mapping have revealed that the cloned RAD4 gene can be mapped and integrated into the yeast chromosome V, the actual site of this gene. DNA‐tRNA hybridization has shown that the isolated RAD4 gene did not contain a suppressor tRNA gene. These results have indicated that the pPCl is a functional RAD4 gene playing a unique role involved in the nucleotide excision repair of yeast without any genetic change during amplification in E. coli.
PHOTORECEPTOR PROTEINS AND PIGMENTS IN THE PARAFLAGELLAR BODY OF THE FLAGELLATE Euglena gracilis
Authors: Brodhun Bonita , Hader Donat‐P.
Published: January 2008

Abstract— –The presumed photoreceptor for phototaxis, the paraflagellar body, in the flagellate Euglena gracilis, was isolated still attached to the flagellum. After solubilization, fast protein liquid chromatography (FPLC) analysis yielded four major protein fractions with the chromophoric groups still attached. Fluorescence spectra showed that three fractions had excitation peaks at 380 nm and emission peaks around 450 nm indicative of pterins, while the fourth chromoprotein had a fluorescence emission at 520 nm and an excitation peak at 450 nm, indicative of a flavin. The separated proteins were analyzed by gel electrophoresis: the pterin binding proteins have apparent molecular masses between 27 000 and 31 600 and the flavin binding protein has an apparent molecular mass of 33 500.
RESEARCH NOTE
Authors: Hacham Haim , Freeman Steven E. , Gange Richard W. , Maytum Daniel J. , Sutherland John C. , Sutherland Betsy M.
Published: January 2008

Abstract— A previous report [Freeman et al.(1986) Photochem. Photobiol.43S, 93S] indicated that irradiation of human skin in situ with 385 or 405 nm radiation produced detectable levels of pyrimidine dimers in DNA. Since these wavelengths are absorbed poorly by DNA, these results suggested that DNA damage was sensitized by other absorbing molecules present in skin. Examination of two experimental aspects of the previous work indicates that (1) the static gel electrophoresis method for DNA dispersion used in lesion determination gave accurate values of the levels of induced dimers, and (2) the DNA damage apparently induced by 385 nm was actually induced by shorter wavelength UV present in the 20 nm bandpass beam of the monochromator. The current results indicate that monochromatic 385 and 405 nm radiation are ineffective in dimer production in human skin in situ.
A STUDY OF THE PHOTODYNAMIC EFFICIENCIES OF SOME EYE LENS CONSTITUENTS
Authors: Krishna C. Murali , Uppuluri Shobha , Riesz Peter , JR J. Samuel Zigler , Balasubramanian D.
Published: January 2008

We have studied the photochemical quantum yields of singlet oxygen production (using the RNO bleaching method) and superoxide production (using the EPR‐spin trapping method and the SOD‐inhibitable ferricytochrome c reduction spectral assay) of kynurenine (Ky), N‐formylkynurenine (NFK), 3‐hydroxykynurenine (3HK), kynurenic acid (KUA), and the flavins, riboflavin (RF) and flavin mononucleotide (FMN). Such a study of the photodynamic efficiencies is important since these compounds appear endogenously in the eye. The singlet oxygen quantum yields of the flavins and KUA are high, while Ky and 3HK generate no detectable amounts of singlet oxygen. The superoxide quantum yields of the sensitizers are low compared to their singlet oxygen, and Ky and 3HK produce no detectable amounts of superoxide. The production of the superoxide radical is enhanced in the presence of electron donor molecules such as EDTA and NADH. These results suggest that the production of oxyradicals in the lens may be modulated by the presence of endogenous electron donor molecules such as the coenzymes NADH and NADPH, which are present in significant amounts in some lenses. They also suggest that Ky and 3HK, which are known to be present in aged lenses, might play a protective rather than a deleterious role in the eye.
SITES and EFFICACY OF PHOTODAMAGE BY TIN ETIOPURPURIN in vitro USING DIFFERENT DELIVERY SYSTEMS
Authors: Kessel David , Morgan Alan , Garbo G. M.
Published: January 2008

Photosensitization by tin etiopurpurin (SnET2) was determined in cell culture using sensitizer dissolved in ethanol or solubilized via three different delivery systems: Cremophor EL, γ‐cyclodextrin or Molecusol (a more water‐soluble cyclodextrin derivative). Sensitizer uptake was substantially more efficient when the delivery systems were employed, in terms of intracellular level needed to lethally photosensitize cells. We observed photodamage at both membrane and mitochondrial loci, but the former was better correlated with loss of viability.
TIME‐RESOLVED FLUORESCENCE OF NITROBENZOXADIAZOLE‐AMINOHEXANOIC ACID: EFFECT OF INTERMOLECULAR HYDROGEN‐BONDING ON NON‐RADIATIVE DECAY
Authors: Lin Su , Struve Walter S.
Published: January 2008

The fluorescence kinetics of the nitrobenzoxadiazole (NBD) chromophore were studied at low concentrations in solvents with varying polarity and hydrogen‐bonding donor strength. The emission decay was essentially single exponential in all solvents studied. While the absorption and fluorescence solvatochromism is determined largely by the solvent polarity, the S, state decay kinetics are strongly modulated by the solvent H‐bonding capacity. The NBD emission lifetime, generally –7–10ns in the aprotic solvents, is reduced to 0.933 ns in water. The solvent deuterium isotope effect on the fluorescence decay is substantial in D20 and in methanol‐d4, but is insignificant in DMSO‐d6. These results are consistent with acceleration of S1S11 internal conversion through an accepting vibrational mode created by intermolecular hydrogen‐bonding of the NBD chromophore to an H atom‐donating solvent. This work bears on the practicality of using NBD as a fluorophore in assays for estrogen and progesterone receptors.
THE SHAPE OF FLUENCE‐RESPONSE CURVES FOR THE LIGHT‐INDUCED TRANSCRIPT ACCUMULATION IN PEA SEEDLINGS
Authors: Yoshida Kazuichi , Takimoto Atsushi , Sasaki Yukiko
Published: January 2008

The fluence‐response curves for the transcript accumulation of four light‐regulated genes were investigated at various times after exposure to 5‐min red light ranging from a very low fluence (1.6 × 10−3μmol m−2) to low fluence (3.0 × 103μmol m−2). The fluence‐response curves were monophasic 6 or 12 h after exposure, although they were biphasic 48 h after exposure, as reported elsewhere. The curves determined 18 or 24 h after red light exposure showed a monophasic or slightly biphasic character. That is, the shape of the fluence‐response curves changed from monophasic to biphasic with an increase in the time of darkness after the treatment with 5 min red light.
PHOTOOXYGENOLYSIS OF VITAMIN B12 and RELATED CORRINS: COBALT(III)CORRINS AS SUBSTRATES and QUENCHERS FOR SINGLET OXYGEN (1Δg)*
Authors: Kraeutler Bernhard , Stepanek Rene
Published: January 2008

Under photooxygenolytic conditions, vitamin B12 can be degraded to two isomeric dioxosec‐ocorrins by a regioselective oxygenolytic cleavage of the corrin macrocycle (preliminary report in Krautler and Stepanek (1985), Angew. Chem.97,71–73; Angew. Chem. Intl. Ed. Engl.24,62–64): irradiation of an oxygen saturated solution of vitamin B12 (1), of KCN and of methylene blue (molar ratio (1:1:0.005) in CD3OD at ca 200 K with visible light led to a selective oxygenolysis of the vitamin. The two products, potassium CoαCoβ‐dicyano‐5,6‐dioxo‐5,6‐seco‐5′6′‐dimethylbenzimidazolyl‐cobam‐idate (3, 10% yield) and potassium CoαCoβ‐dicyano‐14,15‐dioxo‐14,15‐seco‐5′6′‐dimetliylbenzirnida‐zolyl‐cobamidate (4, 25% yield), and 1 (31% yield) were chromatographically separated and isolated. The structures were established spectroanalytically, and by the help of an acid catalyzed methanolysis of 3 and 4 to the related CoαCoβ ‐dicyano‐heptamethyl‐ dioxosecocobyrinates (6 and 7).

When irradiated with visible light in any oxygen saturated methanolic solution containing methylene blue, vitamin B12 itself exhibited considerable inertness. Only upon addition of a stoichiometric amount of KCN to such a solution (to afford the adduct 2) did the photolysis lead to oxygenation of the cobaltcorrin within a useful time. The regioselectivity of the oxygenolysis of 2 and the ratio of products formed are comparable to the outcome of the photooxygenolysis of the structurally related heptamethylcobyrinate 5 (Kräutler (1982) Helv. Chim. Acta65,1941–1948). The reaction at the methyl‐substituted meso‐positions of the corrin macrocycle is indicated to involve singlet oxygen (1Δg). In support of this interpretation, the preparative photolysis of 2 at 200 K also turned out to be about 7 times slower when CH3OH was used instead of CD3OD.
CHOLESTEROL CONTENT BUT NOT PLASMA MEMBRANE FLUIDITY INFLUENCES THE SUSCEPTIBILITY OF L1210 LEUKEMIA CELLS TO MEROCYANINE 540‐SENSITIZED IRRADIATION
Authors: Gaffney David K. , Feix Jim B. , Schwarz Hans P. , Struve Mark F. , Sieber Fritz
Published: January 2008

This paper examines the relationship between lipid composition, plasma membrane fluidity, expression of dye binding sites, and susceptibility to merocyanine 540 (MC540)‐sensitized irradiation in L1210 leukemia cells. Reducing the cells' cholesterol content by exchange diffusion with phosphatidylcholine liposomes or by inhibiting its biosynthesis with 25‐hydroxycholesterol enhanced plasma membrane fluidity, the expression of dye binding sites, and the cells' susceptibility to MC540‐sensitized irradiation. Conversely, if the cholesterol content was enhanced by exchange diffusion with cholesterol:phosphatidylcholine liposomes, the cells' susceptibility to MC540‐sensitized irradiation was decreased. However, contrary to expectations, dye‐binding was slightly enhanced and plasma membrane fluidity remained unchanged. Growing the cells in fatty acid‐supplemented medium had profound effects on their lipid composition. Cells enriched in polyunsaturated fatty acids had more fluid plasma membranes. However, dye‐binding was not significantly affected and photosensitivity was slightly reduced. These results suggest that cholesterol is one, but probably not the only, determinant of the expression of cellular dye binding sites and, consequently, the cell's susceptibility to MC540‐sensitized irradiation. By contrast, plasma membrane fluidity does not appear to play a major role in the regulation of dye‐binding site expression.
STRUCTURE and CONFORMATION OF PHOTOSYNTHETIC PIGMENTS and RELATED COMPOUNDS. 2. NICKEL (II) METHYL PYROPHEOPHORBIDE a–A SEVERELY ISTORTED CHLOROPHYLL DERIVATIVE*
Authors: Senge Mathias O. , Smith Kevin M.
Published: January 2008

The crystal structure of Ni(II) methyl pryopheophorbide a (3) (CMH34N4Ni03, Mu= 605.4) was determined by x‐ray diffraction methods in order to determine the influence of the nickel‐ion on the ring conformation. The crystals were blue octahedrons and crystallized in the tetragonal space group P4121,2 with a= 14.727(4) Å, c = 26.666(12) Å, V= 5781(3) Å3Z= 8, D= 1.391 mg/m3. (Mo Kα) = 0.71069 Åμ= 0.713 mm−1, F(000) = 2544, 130 K. The final R value was 0.064 for 4096 observed reflections, wR = 0.065. The molecule is severely distorted and shows a saddle‐shaped ring conformation, the β‐pyrrole atoms being displaced up to 0.6 A out of the plane of the nitrogens. The severe deformation restricts the use of Ni‐derivatives in spectroscopic model studies on chlorophylls and provides an example for the conformational flexibility of the phorbin macrocycle.
ACTION SPECTRA OF THE ANTILEUKEMIC and ANTIVIRAL ACTIVITIES OF MEROCYANINE 540
Authors: O'Brien J. M. , Singh R. J. , Feix J. B. , Kalyanaraman B. , Sieber F.
Published: January 2008

Action spectra of the antileukemic and antiviral activities of merocyanine 540 (MC540) were determined using L1210 leukemia cells and human Herpes simplex virus type 1. The major peak of both action spectra aligned closely with the absorption spectrum of membrane‐bound dye monomer, and by implication, the action spectrum of 1O2 generation. These results are compatible with the notion that the antileukemic and antiviral activities of MC540 are primarily attributable to membrane‐bound monomer and at least in part mediated by 1O2.
PHOTOCHEMISTRY OF QUINOLYLMETHYLISOTHIORONIUM SALTS. GUANINE SELECTIVE DNA PHOTOCLEAVAGE REAGENTS
Authors: HENRIKSEN U. , LARSEN C. , KARUP G. , JEPPESEN C. , NIELSEN P. E. , BUCHARDT O.
Published: January 2008

Abstract—

Quinolylmethylisothioronium salts (1a and 4a) cleave DNA upon irradiation. The cleavage is more than 10‐fold enhanced by piperidine treatment and subsequently shows a high preference for guanines. Photolysis of 1a, 2a and 4a in water at Λ > 300 nm resulted in photoheterolysis. Irradiation of 1a in 2‐propanol gave only products from photohomolysis, whereas irradiation of 1a in methanol and 2a and 4a in 2‐propanol resulted in products from both photoheterolysis and photohomolysis. Quantum yields for the disappearance of 1a in water and 2‐propanol were determined. The presence or absence of oxygen had no effect in water, whereas oxidation products were observed upon irradiation in methanol and 2‐propanol in the presence of oxygen. The guanine specific DNA photoreaction is proposed to take place by alkylation at N7 via the quinolylmethyl carbocation and thus to represent a photoalkylation.
THE PROTECTIVE FUNCTION OF THE EPIDERMAL LAYER OF RYE SEEDLINGS AGAINST ULTRAVIOLET‐B RADIATION
Authors: TEVINI M. , BRAUN J. , FIESER G.
Published: January 2008

Abstract—

Ultraviolet‐B radiation induces the accumulation of UV‐absorbing pigments of the flavonoid type in the epidermal layer of rye seedlings. The content of pigments identified as isovitexin derivatives was about 4 times higher in leaves preirradiated for up to 24 h with long wavelength UV‐B radiation as compared to control plants without any UV‐B pretreatment. Leaves preconditioned in this way could prevent or reduce damage to photosynthetic function caused by short wavelength UV‐B radiation. Photosynthetic activity monitored by variable fluorescence was reduced in unprotected leaves compared to protected leaves when expressed as a fluorescence decrease ratio value, as quantum yield of photosystem II (Fvm/Fm) or as leaf vitality index (Fm/Fo).
PHOTOPHYSICAL AND PHOTOBIOLOGICAL PROPERTIES OF DIPORPHYRIN ETHERS
Authors: KESSEL DAVID , BYRNE CHRIS J. , WARD A. DAVID
Published: January 2008

Abstract—

Spectral properties of several diporphyrin ethers were assessed in different solvents and after accumulation by leukemia L1210 cells in vitro. To facilitate studies in a variety of solvents, both tetramethylesters of the diporphyrin ethers and free acids were employed. For comparison, studies on the corresponding porphyrin monomers were also carried out. The joining of two porphyrins by an ether linkage had several consequences. We observed a blue shift in the Soret band of the ethers, but not of the corresponding simple porphyrins, in protic solvents. This phenomenon is likely related to ether aggregation under conditions which promote H‐bonding. The presence of an ether linkage was associated with enhanced fluorescence at 630–640 nm and decreased fluorescence lifetimes and yields, especially in protic solvents. The ether linkage was unaffected by intracellular enzymes, but porphyrin esters were readily hydrolyzed upon accumulation by L1210 cells. The joining of two hematoporphyrin molecules by an ether linkage promoted dye accumulation by L1210 cells. In contrast, accumulation of mesoporphyrin and protoporphyrin was thereby retarded.
PHOTODYNAMIC ACTION OF MEROCYANINE 540 IN ARTIFICIAL BILAYERS AND NATURAL MEMBRANES: ACTION SPECTRA AND QUANTUM YIELDS
Authors: SINGH RAVINDER J. , FEIX JIM B. , PINTAR THOMAS J. , GIROTTI ALBERT W. , KALYANARAMAN B.
Published: January 2008

Abstract—

The action spectra and quantum yields for singlet oxygen (1O2) generation by merocyanine 540 (MC540) in liposomes and isolated erythrocyte membranes were obtained using electron spin resonance techniques. Oxygen consumption was measured by spin label oximetry in the presence of histidine for fully‐saturated dimyristoylphosphatidylcholine vesicles, mono‐unsaturated 1‐palmitoyl‐2‐oleoylphosphatidylcholine vesicles and erythrocyte membranes. The quantum yield for the photogeneration of 1O2 by membrane‐bound MC540 in aqueous buffer was determined to be 0.065 ± 0.005, which is approx. 1/10 of the value determined for Rose Bengal under similar conditions. Using unilamellar liposomes and isolated erythrocyte membranes containing MC540 at different monomer/dimer ratios, we have observed that the action spectra of 1O2 generation closely overlap the absorption spectra of the monomeric dye in these systems. It is likely that factors which affect the monomer‐dimer equilibrium of MC540 will influence the production of 1O2. These findings have important implications for the phototherapeutic efficacy of MC540.