bluuebunny/crossref_metadata_2025_split huggingface dataset:
POLARIZED TIME‐RESOLVED FLUORESCENCE SPECTRA OF PHYCOBILISOMES ISOLATED FROM Tolypothrix tenuis EMBEDDED IN POLY(VINYL ALCOHOL) FILM
Authors: Frackowiak Danuta , Minuro Mamoru , Yamazaki Iwao , Tamai Naoto , Fujita Yoshihiko 
Published: January 2008

Abstract–Time‐resolved fluorescence spectra in the ps time range were measured on phycobilisome (PBS) embedded in poly(vinyl alcohol) films. The cyanobacterium Tolypothrix tenuis was used as a source of PBS because the pigment composition and the structure of the PBS are well defined. Isotropic PBS in the unstretched film and PBS uniaxially oriented in the stretched film were investigated. Diameters of PBS hemidiscs were oriented parallel to the film‐stretching direction. The time‐resolved fluorescence spectra of the unstretched sample and of the two polarized components in the stretched samples showed several differences in the rise and decay. The delay time, estimated from the time span between the maximum laser pulse and maximal intensity of the phycocyanin and allophycocyanin fluorescence, was much longer than that reported in the aqueous media. This suggests occurrence of a higher thermal deactivation of PBS in polymer film than in aqueous media. The excitation energy transfer from excited phycocrythrin to allophycocyanin was more efficient in the unstretched than in the stretched samples, and it was greater in the parallel polarized component of the stretched sample than in the perpendicular component. The present results are in agreement with a previous suggestion which states that there are two independent pathways of excitation energy transfer in PBS and that there is more than one final emitter of fluorescence. The molecules taking part in various pathways of energy transfer differ in their orientation within PBS.
PHOTO‐CIDNP OF THE AMINO ACIDS
Authors: STOB S. , KAPTEIN R. 
Published: January 2008

AbstractA photochemically induced dynamic nuclear polarisation (photo‐CIDNP) study is presented of the amino acids that are polarisable with a flavin dye. These include derivatives of tryptophan, tyrosine, histidine, methylated lysines and methionine. The influence of pH, concentration and chemical modification on the magnitude of the CIDNP effect has been studied to obtain mechanistic information about the radical pair formation.The pH and concentration dependence of tyrosine and tryptophan polarisation could be accounted for quantitatively. The CIDNP evidence indicates that hydrogen‐atom abstraction is important in generating radical pairs in the case of histidine and tyrosine, while electron transfer prevails in the case of tryptophan, the methylated lysines and methionine.
PHOTOCHEMISTRY OF DNA USING 193 nm EXCIMER LASER RADIATION
Authors: Kochevar Irene E. , Buckley Lisa A. 
Published: January 2008

AbstractPhotoproducts in double‐stranded DNA induced by 193 nm radiation have been investigated. Double‐stranded, supercoiled pBR322 DNA in buffered aqueous solution was exposed to varying fluences of 193 nm radiation from an ArF excimer laser. The quantum yields for formation of cyclobutylpyrimidine dimers, frank strand breaks and alkali labile sites were calculated from the conversion of supercoiled (Form I) DNA to relaxed (Form II) DNA after treatment withMicrococcus luteusdimer‐specific endonuclease, no treatment, or treatment with alkali and heat, respectively. The quantum yields were 1.65 (± 0.03) × 10−3for pyrimidine dimers, 9.4 (± 3.2) × 10−5for frank strand breaks and 9.6 (± 3.6) × 10−5for alkali labile sites. The quantum yields for pyrimidine dimers and frank strand breaks were independent of Tris buffer and EDTA concentrations. The yields of frank strand breaks and alkali labile sites were not affected by 10mMmannitol. The relative quantum yields for these DNA photoproducts induced by 193 nm radiation differed markedly from those produced by 254 nm radiation.
INVESTIGATIONS ON THE FLUORESCENCE CONCENTRATION QUENCHING OF FLAVOMONONUCLEOTIDE IN GLYCERINE‐WATER SOLUTIONS
Authors: Grajek H. , Zurkowska G. , Bojarski C. , Drabent R. 
Published: January 2008

AbstractWe measured concentration changes of the fluorescence quantum yield η/ηo of flavomononucleotide (FMN) in glycerine‐water solutions of various viscosities. The results obtained show that FMN dimers are traps for the exciting light energy as well as the energy transferred non‐radiatively. Very good agreement between the experimental and theoretical η/ηo results was obtained. It has been shown that in the investigated solutions non‐radiative energy transfer from monomers to dimers takes place, preceded by the migration of energy. It has been stated that no monomer quenching occurs in these solutions. The contribution of the individual fluorescence concentration quenching mechanisms has been determined.
ERYTHROPOIETIC PROTOPORPHYRIA: PHOTODYNAMIC TRANSFER OF PROTOPORPHYRIN FROM INTACT ERYTHROCYTES TO OTHER CELLS
Authors: Brun Atle , Western André , Malik Zvi , Sandberg Sverre 
Published: January 2008

AbstractErythrocytes in patients with erythropoietic protoporphyria (EPP) contain large amounts of protoporphyrin and are regarded as the main source of protoporphyrin in this disease. Cells in the skin of EPP patients accumulate protoporphyrin released from the erythrocytes and upon sun exposure endothelial cells are photodamaged. In the present study a light‐induced transfer of protoporphyrin directly from EPP erythrocytes to cultured cells is demonstrated. Erythrocytes were layered upon cultured cells and irradiated. The nearness of erythrocyte and cultured cell membranes potentiated the transfer of protoporphyrin between these cells. This transfer was rapid and preceded the release of protoporphyrin to proteins in the medium. Further irradiation of the protoporphyrin‐enriched cultured cells, after removal of the erythrocytes, caused severe photodamage to the cells and survival was dependent on both the amount of protoporphyrin transferred and on the light fluence. Clinical observations and the results of this study indicate that light energy may be involved in two steps in the pathophysiology of EPP: (A) light‐induced release of protoporphyrin from erythrocytes to endothelial cells and (B) photodynamic damage to protoporphyrin‐enriched endothelial cells.
IMMEDIATE PIGMENT DARKENING: VISUAL AND REFLECTANCE SPECTROPHOTOMETRIC ANALYSIS OF ACTION SPECTRUM
Authors: Rosen Cheryl F. , Jacques Steven L. , Stuart Mary E. , Gange Richard W. 
Published: January 2008

AbstractImmediate pigment darkening (IPD) occurs in human skin upon exposure to ultraviolet‐A and visible radiation. The spectral changes that occur during IPD were measured with a rapid scanning reflectance spectrophotometer (RS) which employs optical fiber bundles for delivery and detection of light between 400 and 750 nm. The radiation dose dependence and wavelength dependence (334–549 nm irradiation) of IPD were studied by both the classical visual grading method and by spectrophotometric scoring using the RS system. The spectral changes that occur at long wavelengths with IPD mimic the natural absorption spectrum of melanin. Therefore, the IPD was scored in terms of the apparent change in melanin optical density, using the method Kollias and Baqer [Photochem. Photobiol. 43,49–54 (1986)], based on reflectance in the620–720 nm range. The nonlinearity of the visual grading method is demonstrated. The degree of IPD is first‐order with respect to delivered dose and saturates after high doses. The maximum amount of IPD attained at saturation is greater for shorter wavelengths. Extrapolation of the reflectance data suggests the longest wavelength capable of eliciting IPD is about 470 nm.
CELL MEMBRANE DNA: A NEW TARGET FOR PSORALEN PHOTOADDUCT FORMATION
Authors: GASPARRO F.P. , DALL'AMICO R. , O'MALLEY M. , HEALD P.W. , EDELSON R.L 
Published: January 2008

Abstract—The effects of 8‐methoxypsoralen plus long wavelength ultraviolet radiation on cell membrane DNA were examined. Treatment of human lymphocytes with 100 ng/ml 8‐methoxypsoralen and 5 J/cm2 UVA led to the formation of 7.1 ±3.8 photoadducts per million bases. A monoclonal antibody, specific for 8‐methoxypsoralen 4′,5′4nonoadducts, was used to detect photoadducts in the cell membrane DNA of human lymphocytes and three lymphoblastoid cell lines. Treatment of lymphocytes with 8‐MOP and UVA reduced the lymphocyte DNA binding capacity by 56%. Cell membranes of normal lymphocytes were shown to contain three high affinity DNA binding proteins of 28, 59, and 79 kDa, respectively.
THE USE OF FLUORESCENT PROBES IN IMMUNOCHEMISTRY*
Authors: Davidson R. Stephen , Hilchenbach Martin M. 
Published: January 2008

Abstract—The limitations and advantages of particular dyes for labelling proteins and other biological materials are discussed. Methods available for conjugating dyes to proteins are outlined. Following a discussion of double labelling methods the use of photoactivatable fluorochromes and time resolved fluorescence methodologies are outlined. The reasons for the photoinstability of some fluorochromes are discussed and methods for overcoming the problem are described.
DNA BREAKS CAUSED BY MONOCHROMATIC 365 nm ULTRAVIOLET‐A RADIATION OR HYDROGEN PEROXIDE and THEIR REPAIR IN HUMAN EPITHELIOID and XERODERMA PIGMENTOSUM CELLS
Authors: Peak Jennifer G. , Pilas Barbara , Dudek Edward J. , Peak Meyrick J. 
Published: January 2008

AbstractThe induction and repair of DNA single‐strand breaks (SSB) assayed by alkaline filter elution was compared in human epithelioid P3 and xeroderma pigmentosum (XP) cells exposed to monochromatic 365‐nm UV‐A radiation and H2O2. Initial yields of SSB were measured with the cells held at 0.5°C during exposure. The yield from exposure to 365‐nm radiation was slightly greater in XP than in P3 cells, whereas H2O2 produced more than three times as many SSB in P3 compared with XP cells. o‐Phenanthroline (50 mM) markedly inhibited the yields of SSB induced in XP cells by H2O2, but had no effect on those produced by 365‐nm UV‐A. These results are consistent with the fact that P3 cells, unlike XP cells, have undetectable levels of catalase. The measured production of trace amounts of H2O2 by the actual 365‐nm UV‐A exposures was not sufficient to account for the numbers of breaks that were observed. Single‐strand breaks produced by both agents were completely repaired after 50 min in P3 cells, as were H2O2‐induced SSB in XP cells. However, 25% of the 365‐nm UV‐A‐induced SSB in XP cells remained refractory to repair after 60 min. The results show that SSB produced by these two agents are different and that 365 nm radiation produces most SSB in cells by mechanisms other than by production of H2O2.
BIOCHEMICAL CHANGES IN HAIRLESS MOUSE SKIN COLLAGEN AFTER CHRONIC EXPOSURE TO ULTRAVIOLET‐A RADIATION*
Authors: Kligman Lorraine H. , Gebre Michele 
Published: January 2008

AbstractEvidence is mounting that UV‐B and UV‐A radiation affect skin differently in responses as diverse as erythema and elastosis. We found in this study that collagen metabolism was also differentially affected. Albino hairless mice were irradiated with two UV‐A sources: (1) UVASUN 3000 (340–400nm) for cumulative exposures of 4000 and 8000 J/cm2; (2) a xenon solar simulator filtered to provide full spectrum UV‐A (320–400nm) and long wavelength UV‐A (335–400nm) for cumulative exposures of 3000 and 4000 J/cm2 respectively. Collagen was isolated from other skin proteins by acid extraction, pepsin digestion and salt precipitation. Collagen types I and III were separated by interrupted gel electrophoresis. Ultraviolet‐A rendered the collagen highly resistant to pepsin digestion. In age‐matched controls only16–18% of the total collagen remained insoluble, whereas in long wavelength UV‐A‐irradiated skins the insoluble fraction was as high as 87%. A dose response was noted at 4000 and 8000 J/cm2 as delivered by the UVASUN. Recovery of collagen from the pepsin soluble fraction was low in all UV‐A groups and the amount of type III so small that determination of ratios of type III to I collagen was unreliable. These results suggest that chronic UV‐A radiation may increase cross‐linking of dermal collagen.
THE PHOTO‐OXIDATION OF N, N‐DIETHYLHYDROXYLAMINE BY ROSE BENGAL IN ACETONITRILE AND WATER
Authors: Bilski P. , Li A.S.W. , Chignell C.F. 
Published: January 2008

AbstractThe Rose Bengal photosensitized oxidation of N,N‐diethylhydroxylamine has been investigated in water and acetonitrile using the techniques of oxygen uptake, singlet oxygen phosphorescence and electron spin resonance. In both solvents H2O2 is the major oxidation product and diethylnitroxide is an intermediate. In water, superoxide dismutase decreases oxygen uptake suggesting involvement of superoxide anions in the oxidation process. Results indicate that in water the photo‐oxidation proceeds mainly by a Type I(electron transfer) mechanism, while in acetonitrile a Type II(energy transfer) mechanism has been confirmed (Encinas et al., 1987, J. Chem. Soc. Perkin Trans. II,1125–1127).
ROOM‐TEMPERATURE FLUORESCENCE PROPERTIES OF THE POLYNUCLEOTIDE POLYdA POLYdT
Authors: Ge G. , Georghiou S. 
Published: January 2008

AbstractThe room‐temperature fluorescence spectrum of the non‐alternating polynucleotide polydA‐polydT is found to have its maximum at about 325 nm and, when exciting in the spectral region where both adenine (A) and thymine (T) absorb, to coincide with that obtained for excitation at 293 nm where thymine is selectively excited. The fluorescence anisotropy is found to be equal to 0.18 and independent of the excitation and emission wavelengths. These observations are consistent with: (i) emission stemming from T; and (ii) transfer of electronic energy from A to T being not efficient. These inferences are also supported by the observed dependence of the fluorescence quantum yield on the excitation wavelength.
ACTION SPECTRA AGAIN?*
Authors: Coohill Thomas P. 
Published: January 2008

AbstractAction spectroscopy has a long history and is of central importance to photobiological studies. Action spectra were among the first assays to point to chlorophyll as the molecule most responsible for plant growth and to DNA as the genetic material. It is useful to construct action spectra early in the investigation of new areas of photobiological research in an attempt to determine the wavelength limits of the radiation region causing the studied response. But due to the severe absorption of ultraviolet (UV) radiation by biological samples, UV action spectra were first limited to small cells (bacteria and fungi). Advances in techniques(e.g.single cell culture) and analysis allowed accurate action spectra to be reported even for mammalian cells. But precise analytical action spectra are often difficult to obtain when large, pigmented, or groups of cells are investigated. Here some action spectra are limited in interpretation and merely supply a wavelengthvseffect curve. When polychromatic sources are employed, the interpretation of action spectra is even more complex and formidable. But such polychromatic action spectra can be more directly related to ambient responses. Since precise action spectra usually require the completion of a relatively large number of careful experiments using somewhat sophisticated equipment over a range of at least six wavelengths, they are often not persued. But they remain central to the elucidation of the effect being studied. The worldwide community has agreed that stratospheric ozone is depleting, with the possibility of a consequent rise in the amount of UV‐B (290–320nm) reaching the earth's surface. It is therefore essential that new action spectra be completed for UV‐B effects on a large variety of responses of human, animal, and aquatic plant systems. Combining these action spectra with the known amounts of UV‐B reaching the biosphere can give rise to solar UV effectiveness spectra that, in turn, can give rise to estimates of effect. Preliminary estimates suggest that ozone layer depletion may seriously impact such important biological end‐points as skin cancer, cataracts, the immune system, crop yields, and oceanic phytoplankton. So action spectra continue to play a central role in important photobiological research.
ISOMER COMPOSITION and SPECTRA OF THE DARK and LIGHT ADAPTED FORMS OF ARTIFICIAL BACTERIORHODOPSINS*
Authors: Steinberg G. , Friedman N. , SHEVES M. , Ottlenghi M. 
Published: January 2008

Abstract– The isomer composition and spectral properties of 15 artificial bacteriorhodopsin (bR) pigments, based on a series of retinal analogs with polyene residue modified below C9 are determined for both dark‐adapted (DA) and light‐adapted (LA) forms. Similarly to native bR, in all cases only two isomers, C13=C14cis (13‐cis) and M‐trans, are observed. However, the artificial DA pigments have a lower 13‐d.s content than native DA bR (˜ 66%) while the corresponding LA pigments have a much higher 13‐cis content (11‐69%) than native LA bR (<2%). Thus, in variance with the native pigment, in all of the artificial systems light also induced the reversed all‐trans13‐cis process. The data are accounted for in terms of specific steric interactions between the polyene and the protein binding site which allow a (C15‐anti)(Cls‐syn) isomerization during the photocycle of the artificial pigments, but not in the case of native bR. This accounts for the high proton pumping efficiency of the natural pigment.The nature of a highly red shifted light‐adapted form of two of the artificial pigments is investigated and discussed. It is also shown that, in variance with native bR, several artificial pigments exhibit identical absorption spectra for their 13‐cis and all‐trans isomers. It is concluded that the spectral data for the above species of artificial pigments do not lead to a clear molecular model for the origin of the spectral shift between 13‐cis and all‐trans bR.
CELLULAR DELIVERY AND RETENTION OF PHOTOFRIN II: THE EFFECTS OF INTERACTION WITH HUMAN PLASMA PROTEINS
Authors: KORBELIK MLADEN , HUNG JACLYN 
Published: January 2008

Abstract—The absorbance and fluorescence spectra of Photofrin II (PII) in the presence of albumin, globulins and lipoproteins from human plasma show that all of these proteins induce a degree of disaggregation of PII material. In addition, there are substantial rearrangements in the distribution of different fractions contained in PII and their binding to the protein. It is shown that these rearrangements have considerable impact on the uptake of PII by cultured cells and the ensuing retention of the drug in the cells. The information on the contribution of fluorescing and non‐fluorescing components of PII in the cells was obtained by measuring first the PII fluorescence in suspensions of live cells, followed by chemical extraction of porphyrin material from the same cells. The interaction of PII with low density lipoproteins resulted in markedly lower levels of PII material retained in the cells, compared to protein‐free drug exposure. Somewhat better but still inferior PII retention was observed with high density lipoproteins. The samples with very low density lipoproteins showed increased uptake of PII, but the subsequent retention of the drug was low, so that the remaining amount of the drug was not much different than in protein‐free samples. The strongest inhibition of PII uptake was seen with albumin, with ensuing retention of PII not significantly different than in protein‐free samples. The best retention of PII was observed with globulins, with approx. 25% higher total drug content retained in the cells after long‐term clearance relative to protein‐free samples.
ARE THE EFFECTS OF LIGHT ON PHASE AND PERIOD OF THE Gonyaulax CLOCK MEDIATED BY DIFFERENT PATHWAYS?
Authors: ROENNEBERG TILL , HASTINGS J. WOODLAND 
Published: January 2008

Abstract—The effects of different wavelengths of light on period, phase shifting, entrainment and after‐effects of the circadian clock of the motile marine dinoflagellate Gonyaulax polyedra are described. Phase shifting and entrainment by light can be explained by the action of a single blue sensitive light input pathway. However, tonic effects of light on the period under free‐running conditions, and also after‐effects on period resulting from single 4 h light exposures, appear to involve two input pathways with different absorption and temperature characteristics. These results suggest different mechanisms for the control of phase and period of the circadian clock.
PSORALEN‐PHOTOSENSITIZED DAMAGE OF RAT PERITONEAL EXUDATE CELLS
Authors: KYAGOVA A. A. , KORKINA L. G. , SNIGIREVA T. V. , LYSENKO E. P. , TOMASHAEVA S. K. , POTAPENKO A. YA. 
Published: January 2008

Abstract— Psoralen‐sensitized photodamage (PUVA) of rat peritoneal exudate cells was investigated. Quartz‐activated luminol‐dependent chemiluminescence (ChL) was registered and the amount of trypan‐positive cells was determined.Irradiation of peritoneal exudate cells in the presence of psoralen resulted in a dose‐dependent monotonous inhibition of ChL. The reciprocity law of irradiation intensity and duration of irradiation was not valid for the observed inhibition of ChL; the inhibition increased with higher intensity.When psoralen previously photooxidized in ethanol (POP) was added to peritoneal exudate cell suspension, a double‐phase response depending on psoralen irradiation dose was obtained: ChL activation was observed at low doses of UVA, ChL inhibition at high doses. Chemiluminescence inhibition correlated well with the increase in the number of trypan‐positive cells.It may be supposed that the observed effects of PUVA or POP treatment are caused by cell cytoplasmic membrane damage.
PROTECTIVE ROLE OF BUTYLATED HYDROXYTOLUENE AND CERTAIN CAROTENOIDS IN PHOTOCARCINOGENESIS*
Authors: BLACK HOMER S. , MATHEWS‐ROTH MICHELINE M. 
Published: January 2008

Abstract—Butylated hydroxytoluene (BHT) and certain carotenoid pigments have been found to inhibit photocarcinogenesis in animal models. In addition, BHT protects against UV‐B‐induced erythema and UV‐B induction of ornithine decarboxylase.Studies on the photoprotective mechanism(s) of BHT suggested that changes in the physico‐chemical properties of the keratin of the stratum corneum layer of skin occurred, leading to increases in UV absorption of that tissue. These changes might be exertedviathe anti‐radical action of BHT that retards oxidation and prevents cross‐linking of the keratin chains, resulting in a diminution of UV‐B radiation reaching potential target sites.The carotenoids β‐carotene, canthaxanthin and phytoene also inhibit UV‐B carcinogenesis. β‐Carotene and canthaxanthin are excellent quenchers of singlet oxygen, and all three pigments can quench free radicals. β‐Carotene and canthaxanthin have been shown to quench singlet oxygen/free radical reactions in the skin of porphyric mice, and these two pigments as well as phytoene have been found to quench excited species formed on irradiation of mouse skin by UV‐B.