bluuebunny/crossref_metadata_2025_split huggingface dataset:
HYDROGEN GENERATION FROM ARTIFICIAL SEA HATER IN A SEMICONDUCTOR SEPTUM ELECTROCHEMICAL PHOTOVOLTAIC CELL
Authors: TIEN H. TI , CHEN J.‐W. 
Published: January 2008

AbstractVisible light of the solar spectrum is directly converted to stored chemical energy of hydrogen from artificial sea water in a novel electrochemical photovoltaic cell. The principal element of the cell, modeled after the photosynthetic thylakoid membrane, is a semiconductor septum made of polycrystalline n‐CdSe thin film deposited on nickel foil, which separates two aqueous solutions. Under short‐circuit conditions, vigorous hydrogen evolution was seen at the Ni surface and continued as long as the cell was operated. The novel cell, the concept of which was derived from pigmented bilayer lipid membrane studies, is easy to construct, simple to operate, and appears to be a practical approach to the photochemical conversion and storage of solar energy.
A STUDY OF SOME POLYPYRIDYLRUTHENIUM(II) COMPLEXES AS DNA BINDERS AND PHOTOCLEAVAGE REAGENTS
Authors: TOSSI ALESSANDRO B. , KELLY JOHN M. 
Published: January 2008

AbstractThe nature of the binding of several ruthenium polypyridyl complexes containing 2, 2`‐bipyridine (bipy), 4, 4`‐dimethyl‐2, 2`‐bipyridine (DMB), 1,10‐phenanthroline (phen), 4,7‐diphenyl‐1,10‐phenanthroline(DPP), 2, 2`, 2`‐terpyridine (terpy), 2, 2`‐biquinoline (biq), 1,4,5,8‐tetraazaphen‐anthrene (TAP) and 1,4,5,8,9,12‐hexaazatriphenylene (HAT), with calf thymus DNA, poly[d(A‐T)] and poly[d(G‐C)] were studied by absorption and emission spectroscopy, DNA melting techniques, and emission lifetime measurements. In low ionic strength phosphate buffer, spectroscopic changes and DNA stabilization depended on the polypyridyl ligands present, and indicated binding that varied from substantially electrostatic to intercalative. Ru(bipy)2(HAT)2+ and Ru(phen)32+, which bind by partial intercalation, also show a strong preference for poly[d(A‐T)]. The emission quantum yields for most complexes were increased in the presence of DNA. An exception was Ru(TAP)32+ which has a markedly reduced emission quantum yield and lifetime in the presence of poly[d(G‐C)] or CT‐DNA, due to photoredox interaction with guanines. Emission decays of the complexes generally showed multiexponential behaviour. The ability of the ruthenium complexes to sensitise DNA cleavage was determined using pBR322 plasmid DNA. Ru(TAP)32+ is the most efficient sensitiser while uncharged complexes and complexes with very short‐lived excited states do not cleave DNA.
ULTRAVIOLET RADIATION INDUCES A CHANGE IN CELL MEMBRANE POTENTIAL in vitro: A POSSIBLE SIGNAL FOR ULTRAVIOLET RADIATION INDUCED ALTERATION IN CELL ACTIVITY
Authors: GALLO RICHARD L. , KOCHEVAR IRENE E. , GRANSTEIN RICHARD D. 
Published: January 2008

AbstractThe regulation of a transmembrane ionic gradient, reflected by the cellular membrane potential, has been shown in several cell systems to be involved in the regulation of cell function. This investigation presents evidence that biologically relevant doses of ultraviolet radiation (UVR) will alter the membrane potential of keratinocytes in vitro. Estimation of the relative change in the steady‐state membrane potential of the murine keratinocyte cell line PAM 212, the murine myelomonocytic cell line P388D., and normal human keratinocytes in culture, were made through the use of the lipophilic cationic membrane potential sensitive probe; triphenylmethylphosphonium. Our observations indicate that UVR composed primarily of UVB (280–320 nm) radiation at doses as low as 100 J/m2 can induce a depolarization in the murine cell lines and a hyperpoiarization in human keratinocytes. Evidence suggests that this difference in the direction of the membrane potential response reflects a difference in Na+/K+ ATPase activity following UVR. These results suggest a possible mechanism for modulation of keratinocyte activity induced by UVR.
PHOTOOXIDATIVE DAMAGE TO LYSOSOMES OF CULTURED MACROPHAGES BY ACRIDINE ORANGE
Authors: Zdolsek Johann M. , Olsson G. Mikael , Brunk Ulf T. 
Published: January 2008

Abstract— Cultured cells accumulate acridine orange (AO), which is a weak basic dye and a photosensi‐tizer, in lysosomes and other acidic compartments. During exposure to blue light, AO‐loaded macrophages show decreasing red granular fluorescence and increasing green diffuse fluorescence. This is hypothesized to represent peroxidative damage to lysosomal membranes resulting in an impaired proton gradient with deprotonation of the AO to its uncharged form and subsequent leakage of the dye. Further damage to the lysosomal membranes will result in release of lytic enzymes from the lysosomal compartment into the cytosol, leading to degeneration and finally cell death.The survival of AO‐loaded and light‐exposed macrophages is controllable by varying the exposure times to blue light. Inhibition of lysosomal proteases by E‐64 results in increased cell survival after AO and blue light‐mediated damage, indicating a role of proteolytic enzymes in this type of damage.Morphological analysis shows 'rounding up'with formation of retraction fibrils and pronounced plasma membrane blebbing. The formation of autophagic vacuoles is an early and pronounced event. After protease inhibition, however, all these phenomena are inhibitable to a considerable degree.We have thus directed photooxidative damage selectively to lysosomal membranes and their contents. This technique will allow further detailed studies of the role of lysosomes in degeneration‐regeneration processes.
PHOTOTRANSFORMATION OF AGGREGATED FORMS OF PROTOCHLOROPHYLLIDE IN ISOLATED ETIOPLAST INNER MEMBRANES
Authors: Boddi Bela , Lindsten Agneta , Ryberg Margareta , Sundqvist Christer 
Published: January 2008

Abstract— Irradiation of an etioplast inner membrane fraction caused the transformation of two photoactive spectroscopically different protochlorophyllide forms into two chlorophyllide forms. A weak light flash, 6% of a saturating flash, preferentially caused the formation of a short wavelength chlorophyllide form absorbing at 672 nm and emitting at 676 nm. A saturating flash resulted in the formation of the 684 nm absorbing form of chlorophyllide with an emission maximum at 698 nm.The circular dichroism (CD) signals of the newly formed chlorophyllide forms indicated that they are pigment aggregates of different sizes. These aggregates are probably connected to protochlorophyllide reductase and NADPH or NADP. In the absence of NADPH a decomposition of the pigment aggregates took place as revealed by a decrease in the CD‐signal. A model is suggested which describes the structural changes of the pigment‐protein aggregates after irradiation.
ON THE SIGNAL‐TRANSDUCTION CHAINS OF TWO Pfr‐ MEDIATED SHORT‐TERM PROCESSES: INCREASE OF ANCHORAGE and MOVEMENT OF Mougeotia CHLOROPLASTS
Authors: Schonbohm Ekkehard , Schönbohm Elfriede , Meyer‐Wegener Jens 
Published: January 2008

Abstract— We examined two published hypotheses on the signal‐transduction chain of the light‐oriented chloroplast movements in the fresh‐water alga Mougeotia. One hypothesis postulates a Ca2+‐influx controlled by a tetrapolar gradient of phytochrome in its far‐red light absorbing form (Pfr). The other hypothesis postulates anchorage sites for actin‐filaments even at those areas of the plasmalemma where phytochrome is in its inactive form (Pr). Calmodulin and Ca2+‐sequestering vesicles are assumed to be essential links of this transduction chain.To test these hypotheses we have studied the effects of Ca2+‐entry blockers, Ca2+ deficiency and calmodulin antagonists on chloroplast movements and on chloroplast anchorage. None of our results support the Ca2+/calmodulin hypotheses mentioned above. The results and their implications (with regard to the role of Ca2', calmodulin and anchorage sites) are discussed.
QUANTUM YIELD OF PRODUCTION OF SINGLET MOLECULAR OXYGEN (xδg) IN AQUEOUS DISPERSIONS OF SMALL UNILAMELLAR LIPID VESICLES. A TIME‐RESOLVED NEAR‐IR PHOSPHORESCENCE STUDY*,†
Authors: Nonell Santiago , Braslavsky Silvia E. , Schaffner Kurt 
Published: January 2008

AbstractThe quantum yield of formation and kinetic behaviour of O2(1δg) in D2O dispersions of small unilamellar vesicles (SUVs) of dipalmitoyl phosphatidylcholine were studied by time‐resolved detection of near‐IR phosphorescence. At a SUV concentration of 26 nM, O2(1δg) is not quenched by the vesicles. It diffuses quickly through the lipid bilayer and a partition equilibrium of O2(1δg) between the lipid bilayer and the buffer is attained before decay occurs. In this equilibrium situation O2(1δg/sb>) is mostly located in the buffer phase, which permits the determination of absolute quantum yields for O2(1δg) production, φδ, by comparison of the luminescence in the dispersions with that in neat D2O. The maximal φδ values for the sensitizers incorporated in the SUV bilayer were 0.47 ± 0.09 for the dipyridyl complex of zinc(II) phthalocyanine (ZnPc), 0.35 ± 0.08 for porphycene, and 0.36 ± 0.08 for 2,7,12,17‐tetra‐H‐propylporphycene. These values are equal to those in neat organic solvents but lower than those previously obtained in SUVs by using chemical trapping agents. The high degree of organization of the environment around the sensitizers does not influence their efficiency of producing O2(1δg). While no concentration dependence is observed for ZnPc (at least up to a local concentration of 20 mM in the bilayer), φδ for both porphycenes significantly decreases above a local concentration of 4 mM in the bilayer. This result is expected in view of previous observations on the concentration dependence of other photophysical parameters of the porphycenes in such microheterog‐eneous media.
STUDY OF LUMINESCENT FORMS OF THE URANYL ION
Authors: Darmanyan Alexander P. , Khudyakov Igor V. 
Published: January 2008

Abstract—Luminescence spectra and luminescence decay kinetics of uranyl sulphate water and uranyl nitrate acetone solutions of different concentrations have been studied. Similar experiments have been done with uranyl sulphate powder under vacuum. It has been experimentally shown that the hydrolysis of uranyl sulphate in water takes place, and under low salt concentrations (0.1‐4.0 times 10‐4M) a luminescence of a basic form of the photoexcited ion with a tentative structure of UO2OH+* has been observed. The luminescence of the acidic form UO+* has been observed under higher salt concentrations (1–4 times 10‐2M) in water and under any salt concentration in acetone. The acidic form has the characteristic emission spectrum possessing vibrational structure. The luminescence concentrational quenching of both photoexcited uranyl forms and exciplex emission have not been observed. The effect of a number of organic quenchers and molecular oxygen on uranyl luminescence has been studied. There is no luminescence quenching by O2 up to 2 times 106 Pa (20 atm) pressure. The low effectiveness of energy transfer from the photoexcited uranyl forms has been explained in terms of strong steric screening of 5f‐uranium (VI) orbital by oxygen atoms and by external filled up uranium electronic shells.
ANTHRALIN‐DERIVED TRANSIENTS—II. FORMATION OF THE RADICAL BY SPONTANEOUS FRAGMENTATION OF BOTH SINGLET AND TRIPLET STATES OF THE 10,10′‐DEHYDRODIMER: RADICAL PAIR MULTIPLICITY EFFECTS
Authors: Bruce J. M. , Dodd N. J. F. , Gorman A. A. , Hamblett I. , Kerr C. W. , Lambert C. , McNeeney S. P. 
Published: January 2008

Abstract—The singlet and triplet states of the anthralin (1,8‐dihydroxy‐9‐anthrone) dehydrodimer have been produced selectively in benzene via pulsed laser excitation and pulse radiolysis respectively. The lifetime of S, is 30 ps, that of T, short but unspecified. Both states fragment spontaneously to yield a pair of anthralin radicals. The singlet radical pair predominantly undergoes geminate recombination within the solvent cage. In contrast, the corresponding triplet radical pair undergoes essentially exclusive cage escape to give the anthralin free radical (δ.max 370, 490 and 720 nm) which recombines under normal diffusive conditions. Both recombination processes lead, at least in part, to one or more species which have been assigned as tautomeric forms of the original dimer. The anthralin free radical in benzene is insensitive to the vitamin E model 6‐hydroxy‐2,2,5,7,8‐pentamethylchroman and reacts only slowly with oxygen.
THE INFLUENCE OF THE LIGANDS ON THE LUMINESCENCE OF METAL IONS*
Authors: Blasse G. 
Published: January 2008

Abstract—The nature of the ligands determines the luminescence properties of the central metal ion. This is illustrated on the following examples: (i) nonradiative transitions in the strong coupling model; (ii) nonradiative transitions in the weak coupling model; (iii) energy transfer from ligand to central ion. Several applications are dealt with. The cryptand ligands appear to play a special role.
SELF‐IRRADIATION EFFECT ON YEAST CELLS
Authors: Grasso F. , Musumeci F. , Triglia A. , Yanbastiev M. , Borisova S. 
Published: January 2008

AbstractThe effect of self irradiation on yeast cells has been investigated by counting the young gemmae formation in 104 self irradiated samples, as compared with an equal set of control samples. The results show that the rate of gemmae formation is higher in self irradiated samples; the statistical significance of the results is discussed.
COMPARATIVE PHOTO ACTIVITY OF TIN and ZINC PORPHYRIN INHIBITORS OF HEME OXYGENASE: PRONOUNCED PHOTOLABILITY OF THE ZINC COMPOUNDS
Authors: Greenbaum Nancy L. , Kappas Attallah 
Published: January 2008

AbstractMetalloporphyrin inhibitors of heme oxygenase may also have photosensitizing properties in vivo. To assess photoactivity in serum, the relative ability to mediate photooxidation of tryptophan or other oxidizable targets, presumably by singlet oxygen production, was measured for tin mesopor‐phyrin, zinc mesoporphyrin, and zinc deuteroporphyrin bisglycol in aqueous solution and when bound to human serum albumin. While tin mesoporphyrin sensitized at the greatest initial rate in aqueous solution, the zinc compounds sensitized at a greater initial rate in detergent micelles or when bound to albumin. There was minimal alteration of the tin mesoporphyrin during the time course of illumination in the Soret or visible absorption regions. The zinc compounds, however, proved to be extremely photolabile and were extensively destroyed by light; the photooxidized forms were found to be ineffective as inhibitors of heme oxygenase.
AGE‐RELATED CHANGES IN THE FLUORESCENCE OF MELANIN and LIPOFUSCIN GRANULES OF THE RETINAL PIGMENT EPITHELIUM: A TIME‐RESOLVED FLUORESCENCE SPECTROSCOPY STUDY
Authors: Docchio Franco , Boulton Mike , Cubeddu Rinaldo , Ramponi Roberta , Barker Pierrette Dayhaw 
Published: January 2008

AbstractThe photophysical properties of purified populations of melanin and lipofuscin granules from human retinal pigment epithelium, and their changes with donor age, have been investigated using high‐sensitivity time‐resolved fluorescence spectroscopy techniques with picosecond gating capabilities. The overall fluorescence intensity of both melanin and lipofuscin granules clearly increased with increasing donor age, the increase being most marked for melanin. In all granule populations the fluorescence decays were multiexponential with subnanosecond and nanosecond decay components. The resultant time‐integrated and time‐gated spectra also exhibited marked age‐variations for each type of granule. Young melanin showed spectral patterns similar to those of bovine melanin, while a yellow‐orange fluorescence band appeared in melanin samples from older age groups. Lipofuscin granules exhibited a blue, a yellow and an orange band whose relative amounts were age‐related. The results demonstrate the potential of time‐resolved techniques for discriminating fluorophores in vitro and in situ, and have confirmed results previously obtained using extraction techniques. Furthermore, the ability of this technique to identify and quantify individual fluorophores within granules may provide an important insight into the origin and development of lipofuscin within the retinal pigment epithelium and ultimately into the mechanisms of age‐related retinal diseases.
ORIGIN OF THE RED SHIFTED ABSORPTION IN PHYCOCYANIN 632 FROM Mastigocladus laminosus
Authors: Gottschalk L. , Fischer R. , Lottspeich F. , Scheer H. 
Published: January 2008

AbstractA phycocyanin (PC) with γmax= 632 nm (PC632) was isolated from extracts of the cyanobacterium Mastigocladus laminosus. The complex contained three polypeptides migrating in SDS‐PAGE around 22 kDa. The N‐termini of the three polypeptides are identical. They are homologous to rod‐core linker polypeptides from this and another cyanobacterium and are identical to one of them. Reconstitution of PC (γmax=614–620 nm) with the 22 kDa polypeptide produced again the red‐shifted PC632. Phycobilisomes isolated at pH 6 or 7 contain, if any, only traces of 22 kDa polypeptides. Origin and functions of the polypeptides are discussed, they are most likely proteolytic fragments of allophycocyanin‐PC rod‐core linkers that contain the PC‐binding domain.
CARBOXYLATED ZINC‐PHTHALOCYANINES–II* DIMERIZATION AND SINGLET MOLECULAR OXYGEN SENSITIZATION IN HEXADECYLTRIMETHYLAMMONIUM BROMIDE MICELLES
Authors: Daraio Marta E. , Aramendía Pedro F. , Román Enrique A. San , Braslavsky Silvia E. 
Published: January 2008

AbstractThe dimerization of the diamide of zinc‐tetracarboxyphthalocyanine was studied spectro‐scopically in hexadecyltrimethylammonium bromide (CTAB) micelles at surfactant concentrations from 0.026 to 0.1 M and dye concentrations between 0.1 and 10 μM. The apparent dimerization constant in CTAB 0.1 M is 8.6 × 105M−1, while the intramicellar dimerization constant is 1.8 × 103. The dimer absorption spectrum was also obtained. Singlet molecular oxygen sensitization was studied by steady state photolysis using 1,3‐diphenylisobenzofurane as scavenger in 0.1 M CTAB. The usual sensitization mechanism is extended to include dimer reactions. Singlet molecular oxygen sensitization yields for monomer and dimer in the micelles are 0.7 and 0.1, respectively. With the reported values it is possible to calculate the average yield of singlet molecular oxygen production at any surfactant and dye concentrations.
DIFFERENTIAL INACTIVATION OF SURROGATE VIRUSES WITH MEROCYANINE 540
Authors: Lytle C. D. , Budacz A. P. , Keville E. , Miller S. A. , Prodouz K. N. 
Published: January 2008

AbstractBacteriophages may be useful as surrogates for animal viruses when the virucidal properties of different photosensitizing compounds are initially investigated. We studied photoinactivation of four bacteriophages, φX174, T7, PRD1, and φ6, by the dye merocyanine 540 (MC540) (15 μ g/mL). Merocyanine 540 (MC540) should be most effective with lipid‐containing viruses, since it is primarily lipophilic (but also binds to proteins). Two of the phages, PRD1 and φ6 contain lipid, with only φ6 having an external lipoprotein envelope. Filtered radiation (450–600nm) from a 750 W projector was used at16–100 W/m2. The survival curves of the different viruses clearly demonstrated different levels of sensitivity to photoinactivation by MC540, with φ6 (Do= 1.5 kJ/m2) being the most sensitive, followed by T7 (21‐fold less sensitive). While both PRD1 and (J>6 have lipid components, only φ6 was photoinactivated by MC540. Thus the internal lipid components of PRD1 were not sufficient to allow photoinactivation by this dye, at fluences up to 300 kJ/m2. For comparison, we also photoinactivated Herpes simplex virus (Do= 0.053 kJ/m2) and found it to be 28‐fold more sensitive than φ6 to photoinactivation by the same concentration of MC540. Thus φ6 may be used as a surrogate for enveloped human viruses for photoinactivation by lipophilic dyes, but the results may only be useful qualitatively.
ENHANCEMENT OF THE SENSITIVITY OF RADIATIVE and NON‐RADIATIVE DETECTION TECHNIQUES IN THE STUDY OF PHOTOSENSITIZATION BY WATER SOLUBLE SENSITIZERS USING A REVERSE MICELLE SYSTEMS*,†
Authors: Redmond Robert W. 
Published: January 2008

AbstractThe study of photosensitization processes in aqueous solution is complicated by the unsuit‐ability of water as solvent for the commonly used techniques for monitoring radiative and non‐radiative relaxation processes. The infrared luminescence method is hampered by the relatively weak intensity of emission and short lifetime of singlet molecular oxygen, O2(1Δg), in water. Photoacoustic and photothermal detection of the dominant non‐radiative relaxation process for O2(1Δg) is also inhibited by the unfavorable physico‐chemical properties of water which reduce the sensitivities of these techniques for the study of sensitizers in aqueous with respect to non‐aqueous media. Such problems have been alleviated by incorporating the sensitizer in the aqueous core of aerosol OT reverse micelles. It is demonstrated that the sensitivity of both radiative and non‐radiative detection depends not on the local environment of the sensitizer but on the overall composition of the medium, which, in the case of reverse micelle solutions, is predominantly hydrocarbon. This produces a 4.5 and 6‐fold enhancement of the sensitivity of luminescence and optoacoustic detection, respectively, in comparison to purely aqueous solution. The utility of the method is demonstrated for Rose Bengal, where quantum yields of intersystem crossing (φisc) of 0.78 (LIOAC) and singlet oxygen generation (φδ) of 0.81 (LIOAC) and 0.80 (TRLD) were measured. Phenazine was also studied for comparative purposes and to corroborate values obtained for Rose Bengal.
PHOTOCHEMISTRY IN A CYCLODEXTRIN CAVITY. PRIMARY PROCESSES IN THE PHOTOREDUCTION OF 3‐ and 4‐BENZOYLPYRIDINE STUDIED BY LASER FLASH‐PHOTOLYSIS*
Authors: MONT Sandra , Camaioni Nadia , Bortolus Pietro 
Published: January 2008

AbstractThe photochemistry of 3‐ and 4‐benzoylpyridine‐cyclodextrin inclusion complexes (BPyCDx) was examined by nanosecond laser flash‐photolysis and stationary techniques. The lifetimes of the triplet complex and of the triplet radical pair, formed by H‐abstraction from a glucose unit of the CDx, have been measured in β‐CDx complexes. The reactivity of the heterocyclic ketones with CDx is higher than that of benzophenone, but the lower binding ability of the macrocycle toward these more hydrophylic molecules induces faster separation of the geminate radicals. The quantum yields of the escaped radicals and their decay kinetics have been determined. The β‐CDx cage favours geminate recombination reactions, while α‐ and ‐γ‐CDx tend to release the guest molecule. Cage products have been spectroscopically characterized in the case of the 3‐BPy‐β‐CDx system.
INTRAMOLECULAR EXCIMER FORMATION and MOLECULAR RECOGNITION OF MODIFIED CYCLODEXTRINS APPENDED BY TWO NAPHTHALENE RINGS*
Authors: Minato Shingo , Osa Tetsuo , Morita Masahiko , Nakamura Asao , Ikeda Hiroshi , Toda Fujio , Ueno Akihiko 
Published: January 2008

AbstractThe intramolecular excimer formation of 6A,6B‐, 6A,6C‐, 6A,6D‐, and 6A,6E‐bis(2‐naphthyl‐sulfonyl)‐γ‐cyclodextrins (1, 2, 3, and 4, respectively) and 6A.6B‐, 6A,6C‐, and 6A,6D‐bis(2‐naphthyl‐sulfonyl)‐β‐cyclodextrins (5, 6, and 7, respectively) has been studied in 10% ethylene glycol aqueous solution. The two naphthyl rings are co‐included in the γ‐cyclodextrin cavities of1–4, and marked excimer emission was observed for 2, 3, and 4. On the other hand, almost pure monomer emission was observed for 5, 6, and 7 due to inclusion of one of two naphthyl rings in the β‐cyclodextrin cavities. Compounds 2, 3, 6, and 7 showed remarkable guest‐induced enhancement in the excimer emission, and this property was used for detecting several organic compounds with remarkable molecular recognition.