bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE S0AND Ti STATES OF ISOMERIC CANTHAXANTHIN AS COMPARED WITH THOSE OF β‐CAROTENE: EFFECT OF THE TERMINAL CARBONYL GROUPS DETECTED BY RAMAN SPECTROSCOPY
Authors: Hashimoto Hideki , Koyama Yasushi 
Published: January 2008

AbstractThe S0(ground singlet‐state) Raman spectra of theall‐trans, 9‐cis, 13‐cis, 9,9‐cis, 9, 13‐cis,9,13′‐cisand13,13′‐cisisomers of canthaxanthin as well as the T1(lowest‐excited triplet‐state) Raman spectra of theall‐trans, 9‐cis,13‐cis and 9,13‐cis isomers were recorded. In order to reveal the effect of the carbonyl groups at both ends on the carbon‐carbon conjugated system in‐between (in both the S0and T, states), the carbon‐carbon stretching frequencies were compared between isomeric canthaxanthin and p‐carotene: in the S0state, the C=C stretching frequencies of canthaxanthin were lower by3–10 cm−1than those of β‐carotene, indicating increased conjugation in the former. In the T, state, the “C=C” stretching frequencies of canthaxanthin were lower by12–15 cm−1, indicating a large decrease in the “C=C” bond order in the central part of canthaxanthin. Further, the relations of the C=C (S0) and “C=C” (T1) stretching frequenciesvsthe number of carbon‐carbon double‐bonds were examined for the above two and additional five carotenoids. The result indicated that the terminal carbonyl groups of canthaxanthin are incorporated in the carbon‐carbon conjugated system in the T, state, but that they are almost independent of it in the S0state. Both observations support the idea that the “triplet‐excited region” of canthaxanthin is extended over the entire double‐bond system.
FORMATION OF SINGLE AND DOUBLE STRAND BREAKS IN DNA ULTRAVIOLET IRRADIATED AT HIGH INTENSITY
Authors: Masnyk Taras W. , Minton Kenneth W. 
Published: January 2008

AbstractThe induction of single‐strand breaks (SSB) by two quantum processes in DNA is well established. We now report that biphotonic processes result in double‐strand breaks (DSB) as well. pUC19 and bacteriophage M13 RF DNA were irradiated using an excimer laser (248 nm) at intensities of 107, 109, 1010and 1011W/m2and doses up to 30 kJ/m2. The proportion of DNA as supercoil, open circular, linear and short fragments was determined by gel electrophoresis. Linear molecules were noted at fluences where supercoiled DNA was still present. The random occurrence of independent SSB in proximity to each other on opposite strands (producing linear DNA) implies introduction of numerous SSB per molecule in the sample. If so, supercoiled DNA that has sustainednoSSB should not be observed.A model accounting for the amounts of supercoiled, open circular, linear and shorter fragments of DNA due to SSB, DSB and Scissions (opposition of two independently occurring SSB producing an apparent DSB) was developed, our experimental data and those of others were fit to the model, and quantum yields determined for SSB and DSB formation at each intensity. Results showed that high intensity laser radiation caused an increase in the quantum yields for both SSB and DSB formation. The mechanism of DSB formation is unknown, and may be due to simultaneous cleavage of both strands in one biphotonic event or thebiasedintroduction of an SSB opposite a preexisting SSB, requiring two biphotonic events.
HOLE‐BURNING SPECTROSCOPY OF ACTIVE AND INACTIVATEE) PHOTOSYSTEM II PARTICLES
Authors: Vacha M. , Adamec F. , Ambroz M. , Baumruk V. , Dian J. , Nedbal L. , Hala J. 
Published: January 2008

AbstractThis paper reports transient and persistent hole‐burning of photosynthetically active as well as chemically reduced and heat inactivated photosystem II particles isolated from cyanobacteria. Transient spectra of active and non‐active particles are significantly different. For both, the possible origin of the bottle‐neck state is discussed. Persistent holes were ascribed to the antenna complex of photosystem II. From their width the energy transfer rate was estimated to be 4.8 ps at 4.2 K.
PTHALOCYANINE‐INDUCED PHOTODYNAMIC CHANGES OF CYTOPLASMIC FREE CALCIUM IN CHINESE HAMSTER CELLS
Authors: Ben‐Hur E. , Dubbelman T.M.A.R. , Steveninck J. Van 
Published: January 2008

AbstractExposure to light of Chinese hamster cells preloaded with chloroaluminum phthalocyanine causes an immediate increase of cytoplasmic free calcium, [Ca2+]i, from about 0.2 μM to 1 μM within 5 min after illumination. This increase was dose‐dependent within the biological dose range, reaching a plateau at a dose that kills 99.5% of the cells. Fluoride addition prior to light exposure protected against cell killing and reduced the increase of [Ca2+]i. These findings raise the possibility that changes in [Ca2+]i after photodynamic treatment may be relevant to cell killing and/or other biological responses of the cells, e.g. release of eicosanoids.
CHRONIC ULTRAVIOLET RADIATION‐INDUCED INCREASE IN SKIN IRON and THE PHOTOPROTECTIVE EFFECT OF TOPICALLY APPLIED IRON CHELATORS 1,*
Authors: Bissett Donald L. , Chatterjee Ranjit , Hannon Daniel P. 
Published: January 2008

AbstractIn the skin of albino hairless mice (Skh:HR‐l) there is a basal level of non‐heme iron. Chronic exposure of mice to sub‐erythemal doses of ultraviolet (UV) B radiation results in an increased skin level of non‐heme iron. The iron increase may be the result of a UVB radiation‐induced increase in vascular permeability, which we measured in vivo with the dye marker Evans Blue. We also observed greater non‐heme iron in sun‐exposed vs non‐exposed body sites of human skin, suggesting that similar events occur in man.Iron may have a role in skin photodamage by participating in formation of reactive oxygen species. These species have been implicated in skin photodamage. It is known that iron can contribute to oxygen radical production by acting catalytically in the formation of species such as hydroxyl radical. While the basal level of skin iron may be available for catalysis, the elevated iron content of UV‐exposed skin increases the potential for iron‐catalyzed radical production.Topical application of certain iron chelators to Skh albino hairless mice dramatically delayed the onset of UVB radiation‐induced skin photodamage. Non‐chelating analogs provided no significant protection.
SIMULTANEOUS ESTABLISHMENT OF MONOCLONAL ANTIBODIES SPECIFIC FOR EITHER CYCLOBUTANE PYRIMIDINE DIMER OR (6‐4)PHOTOPRODUCT FROM THE SAME MOUSE IMMUNIZED WITH ULTRAVIOLET‐IRRADIATED DNA
Authors: Mori Toshio , Nakane Misa , Hattori Tsuyoshi , Matsunaga Tsukasa , Ihara Makoto , Nikaido Osamu 
Published: January 2008

AbstractSix new monoclonal antibodies (TDM‐2, TDM‐3, 64M‐2, 64M‐3, 64M‐4 and 64M‐5) specific for ultraviolet (UV) induced DNA damage have been established. In the antibody characterization experiments, two TDM antibodies were found to show a dose‐dependent binding to UV‐irradiated DNA (UV‐DNA), decrease of binding to UV‐DNA after cyclobutane pyrimidine dimer photo‐reactivation, binding to DNA containing cyclobutane thymine dimers, and unchanged binding to UV‐DNA after photoisomerization of (6‐4)photoproducts to Dewar photoproducts. These results indicated that the epitope of TDM monoclonal antibodies was the cyclobutane pyrimidine dimer in DNA. On the other hand, four 64M antibodies were found to show a dose‐dependent binding to UV‐DNA, unchanged binding to UV‐DNA after cyclobutane pyrimidine dimer photoreactivation, undetectable binding to DNA containing thymine dimers, and decrease of binding to UV‐DNA after photoisomerization of (6‐4)photoproducts. These results indicated that the epitope of 64M antibodies was the (6‐4)photoproduct in DNA. This is the first report of the simultaneous establishment of monoclonal antibodies against the two different types of photolesions from the same mouse. By using these monoclonal antibodies, we have succeeded in measuring both cyclobutane pyrimidine dimers and (6‐4)photoproducts in the DNA from human primary cells irradiated with physiological UV doses.
PHOTOHEMOLYSIS SENSITIZED BY PSORALEN: RECIPROCITY LAW IS NOT FULFILLED
Authors: Potapenko A. Ya. , Agamalieva M. A. , Nagiev A. I. , Lysenko E. P. , Bezdetnaya L. N. , Sukhorukov V. L. 
Published: January 2008

ReferencesThe effect of the intensity of ultraviolet‐A (UV‐A) radiation (366 nm) on delayed photo‐hemolysis sensitized by psoralen (PUV‐A hemolysis) was studied. It was shown that PUV‐A hemolysis induced by UV‐A radiation at low fluence rate (20 W m−2) develops according to the well‐known colloid‐osmotic mechanism: there was no threshold dose of PUV‐A treatment. After irradiation all the cells were hemolysed. The rate of PUV‐A hemolysis was proportional to the square of the fluence. Hemolysis was delayed in the presence of sucrose. When the fluence rate of UV‐A radiation was increased to 150 W m−2, the character of PUV‐A hemolysis changed drastically. A threshold fluence appeared, below which PUV‐A hemolysis was not induced. At fluences slightly exceeding the threshold, only part of the cells in the suspension were lysed. The dependence of the portion of hemolysing cells on fluence was S‐shaped. Increasing the fluence resulted in complete (100%) hemolysis. The rate of complete hemolysis decreased at higher fluences, but was many‐fold higher than the rate of low‐intensity PUV‐A hemolysis at equal fluences. The main features of high intensity PUV‐A hemolysis (dependences on fluence and temperature, effect of sucrose) were the same for the hemolysis induced by the addition of previously photooxidized psoralen. We suggest that high intensity PUV‐A hemolysis is induced with participation of photooxidized psoralen as an intermediate.
CYCLOBUTANE DIMERS AND (6‐4)PHOTOPRODUCTS IN HUMAN CELLS ARE MENDED WITH THE SAME PATCH SIZES
Authors: Cleaver James E. , Jen Jin , Charles Wayne C. , Mitchell David L. 
Published: January 2008

AbstractThe sizes of excision repair patches corresponding to excision of (6‐4) pyrimidine‐pyrimidone photoproducts and (5‐5,6–6) cyclobutane dimers have been independently determined by using bromodeoxyuridine substitution and density increases in isopycnic gradients of small DNA fragments. The two classes of photoproducts were distinguished by using (a) a xeroderma pigmentosum (XP) revertant cell line that excises (6‐4) photoproducts normally, but does not excise cyclobutane dimers from bulk DNA or from an actively transcribed sequence; (b) an XP cell line containing the denV gene of bacteriophage T4, which repairs only cyclobutane dimers by a unique glycosylase mechanism, and (c) normal cells analyzed during time intervals in which cyclobutane dimer repair is the main repair process in action. The patch sizes for the two lesions were similar under all conditions and were estimated to be approximately30–40 bases. These values are slightly larger than corresponding estimates for Escherichia coli and Saccharomyces cerevisiae but close to estimates from in vitro experiments with human cell extracts. The size of 30 bases may consequently be very close to the actual distance between cleavage sites made on either side of a photoproduct during repair.
QUANTUM YIELD RATIO OF THE FORWARD and BACK LIGHT REACTIONS OF BACTERIORHODOPSIN T LOW TEMPERATURE and PHOTOSTEADY‐STATE CONCENTRATION OF THE BATHOPRODUCT K*
Authors: Balashov S. P. , Imasheva E. S. , Govindjee R. , Ebrey T. G. 
Published: January 2008

AbstractThe maximum photosteady state fraction of K, xKmax, and the ratio of the quantum yields of the forward and back light reactions, trans‐bacteriorhodopsin (bR) hArr; K, φbR/φK, were obtained by measuring the absorption changes produced by illumination of frozen water‐glycerol (1:2) suspensions of light‐adapted purple membrane at different wavelengths at ‐165°C. An independent method based on the second derivative of the absorption spectrum in the region of the β‐bands was also used. It was found thatThe quantum yield ratio (0.66 ± 0.06) was found to be independent of excitation wavelength within experimental error in the range510–610 nm. The calculated absorption spectrum of K has its maximum at603–606 nm and an extinction 0.85 ± 0.03 that of bR. At shorter wavelengths there are P‐bands at 410, 354 and 336 rim. Using the data of Hurley et al. (Nature 270,540–542, 1977) on relative rates of rhodopsin bleaching and K formation, the quantum yield of K formation was determined to be 0.66 ± 0.04 at low temperature. The quantum efficiency of the back reaction was estimated to be 0.93 ± 0.07. These values of quantum efficiencies of the forward and back light reactions of bR at ‐ 165°C coincide with those recently obtained at room temperature. This indicates that the quantum efficiencies of both forward and back light reactions of bacteriorhodopsin are temperature independent down to ‐165°C.
ROTATIONAL DIFFUSION EFFECTS ON ABSORBANCE MEASUREMENTS: LIMITATIONS TO THE MAGIC‐ANGLE APPROACH*
Authors: Lewis J. W. , Kliger D. S. 
Published: January 2008

Abstract–Optical absorbance changes are commonly used to characterize intermediates which appear in the bleaching sequence of rhodopsin and in the photocycle of bacteriorhodopsin. Absorbance changes can be caused by an intermediate's rotational diffusion, and when this occurs it can distort absorbance changes due to the structural evolution of intermediates. Linear polarization of an optical probe source at 54.7° (the magic angle) relative to the polarization direction of a linearly polarized actinic source has often been used to eliminate signals due to rotational diffusion. We used Jones calculus to investigate the validity of the magic‐angle strategy. Taylor expansion of the result in powers of the absorbances of the bleached ground state and of the intermediates leads to a relatively simple expression which can be used to determine whether rotational contributions are likely under various experimental conditions. This expression shows that in first order no dichroism‐dependent term appears in the absorbance measured at magic angle. In second order, however, linear dichroism contributes to signals. For the sequence of rhodopsin intermediates:rhodopsin → bathorhodopsin BSI → lumirhodopsin.where BSI is a recently discovered blue‐shifted intermediate, we determined the magnitude of the dichroism signals to be, on average, <2% of the true absorbance change due to the intermediates themselves (and hence undetectable). Freedom from dichroism artifacts in this case results from the fact that the transition dipoles of these intermediates are similar to that of rhodopsin. Larger and certainly detectable dichroism signals are predicted to occur, even at the magic angle, for later intermediates which have transition dipole moments which differ significantly from that of rhodopsin. Other strategies for eliminating rotational diffusion effects are compared to the magic‐angle approach.
PICOSECOND FLUORESCENCE FROM PHYCOCYANIN 612
Authors: MALAK HENRYK , MACCOLL ROBERT 
Published: January 2008

Abstract—The biliprotein, phycocyanin 612, was purified from a cryptomonad,Hemiselmis virescens.The protein, which is an α2β2dimer having four spectrally different tetrapyrrole chromophores, was studied using picosecond fluorescence by exciting the various chromophores at three wavelengths, 565, 585 and 615 nm. These wavelengths were chosen to excite selectively the three highest energy chromophores. Decay times were measured as the excitation energy migrated from each of the three excited chromophores to the lowest‐energy chromophore. The ps decay times were found to be 9, 13, and 12 ps for excitations at 565, 585, and 615 nm, respectively. A comparison is made between phycocyanin 612 and phycocyanin 645 with regard to the causes of their differing absorption maxima.
CHEMIEXCITATION IN THE ARACHIDONIC ACID CASCADE
Authors: NASCIMENTO ANA LUCIA T. O. , CILENTO GIUSEPPE 
Published: January 2008

Abstract—As investigated in neutrophils, the very weak luminescence accompanying the arachidonic acid cascade is associated with the lipoxygenase pathway. The emission is dramatically enhanced by energy transfer to chlorophylla. The number of chlorophyll molecules excited to the fluorescent state per oxygen consumed, (the S1/O2ratio), equal to the product of the quantum yields of chemiexcitation and of energy transfer, is 5.4 × 10−6. The quantum yield of chemiexcitation is inferred to be higher than 1 × 10−3. The two most likely chemiexcitation routes point to triplet conjugated carbonyls as the most likely candidates for the excited species that transfer to chlorophyll. As such the emission intensity may reflect the level of hydroperoxyeicosatetraenoic acid. This is the first case where addition of a biotic substrate to a cellular system results in substantial generation of electronic excited states without any drastic loss of cell viability. Whether the formation of excited states in the arachidonic acid cascade in neutrophils is accidental or has a biological role is an open question.
A NEW METHOD OF DETERMINING INTRACELLULAR FREE Ca2+CONCENTRATION USING Quin2‐FLUORESCENCE
Authors: MIYOSHI NORIO , HARA KIYOAKI , KIMURA SHIRO , NAKANISHI KAZUO , FUKUDA MASARU 
Published: January 2008

Abstract—We determined intracellular free Ca2+ concentration by fluorescence spectroscopy and the time‐resolved measurements of 2‐[(2‐amino‐5‐methylphenoxy) methyl]‐6‐methoxy‐8‐aminoquinoline‐N, N, N′, N′‐tetraacetic acid, tetrapotassium salt (Quin2) incorporated in suspended mouse leukemia L1210 cells. The paper reports the following two points. (1) Various fluorescence spectrum patterns in cell suspensions dissolved with Quin2 acetoxy methylester were compared with those of the complex in buffer solution containing esterase. (2) The fluorescence lifetime of Quin2 bound to Ca2+ was approx. 4.5–11 times longer (10 ± 1 ns) than that (1.5 ± 0.5 ns) of Quin2. The fraction of the long lifetime component was plotted against the concentration of CaCl2 in buffer solution. From the results obtained, it was found that approx. 35 nM Ca2+ was contained in each L1210 cell.
PHOTOSENSITIZED LIPID PEROXIDATION AND ENZYME INACTIVATION BY MEMBRANE‐BOUND MEROCYANINE 540: REACTION MECHANISMS IN THE ABSENCE AND PRESENCE OF ASCORBATE*
Authors: BACHOWSKI GARY J. , PINTAR THOMAS J. , GIROTTI ALBERT W. 
Published: January 2008

Abstract—The lipophilic photosensitizing dye merocyanine 540 (MC540) is being studied intensively as an antitumor and antiviral agent. Since plasma membranes are believed to be the principal cellular targets of MC540‐mediated photodamage, we have studied membrane damage in a well characterized test system, the human erythrocyte ghost. When irradiated with white light, MC540‐sensitized ghosts accumulated lipid hydroperoxides (LOOHs derived from phospholipids and cholesterol) at a rate dependent on initial dye concentration. Neither desferrioxamine nor butylated hydroxytoluene inhibited LOOH formation, suggesting that Type I (iron‐mediated free radical) chemistry is not important. By contrast, azide inhibited the reaction in a dose‐dependent fashion, implicating a Type II (singlet oxygen, 1O2) mechanism. Stern‐Volmer analysis of the data gave a 1O2 quenching constant ∼50 times lower than that determined for an extramembranous target, lactate dehydrogenase (the latter value agreeing with literature values). This suggests that 1O2 reacts primarily at its membrane sites of origin and that azide has limited access to these sites. Using [14C]cholesterol‐labeled membranes and HPLC with radiodetection, we identified 3β‐hydroxy‐5α‐cholest‐6‐ene‐5‐hydroperoxide as the major cholesterol photoproduct, thereby confirming 1O2 intermediacy. Irradiation of MC540‐sensitized membranes in the presence of added iron and ascorbate resulted in a large burst of lipid peroxidation, as shown by thiobarbituric acid reactivity and appearance of 7‐hydroperoxycholesterol and 7‐hydroxycholesterol as major oxidation products. Amplification of MC540‐initiated lipid peroxidation by iron/ ascorbate (attributed to light‐independent reduction of nascent photoperoxides, with ensuing free radical chain reactions) could prove useful in augmenting MC540's phototherapeutic effects.
THE PHOTODEGRADATION OF PORPHYRINS IN CELLS CAN BE USED TO ESTIMATE THE LIFETIME OF SINGLET OXYGEN
Authors: MOAN JOHAN , BERG KRISTIAN 
Published: January 2008

Abstract—NHIK 3025 cells were incubated with Photofrin II (PII) and/or tetra (3‐hydroxyphenyl)porphyrin (3THPP) and exposed to light at either 400 or 420 nm, i. e. at the wavelengths of the maxima of the fluorescence excitation spectra of the two dyes. The kinetics of the photodegradation of the dyes were studied. When present separately in the cells the two dyes are photodegraded with a similar quantum yield. 3THPP is degraded 3–6 times more efficiently by light quanta absorbed by the fluorescent fraction of 3THPP than by light quanta absorbed by the fluorescent fraction of PII present in the same cells. The distance diffused by the reactive intermediate, supposedly mainly1O2, causing the photodegradation was estimated to be on the order of 0.01–0.02 μm, which corresponds to a lifetime of 0.01–0.04 μs of the intermediate in the cells. PII has binding sites at proteins in the cells as shown by an energy transfer band in the fluorescence excitation spectrum at 290 nm. During light exposure this band decays faster than the Soret band of PII under the present conditions. Photoproducts (1O2etc.) generated at one binding site contribute significantly in the destruction of remote binding sites.
In vivo AND PHOTOPHYSICAL STUDIES ON PHOTOOXIDATIVE DAMAGE TO LENS PROTEINS AND THEIR PROTECTION BY RADIOPROTECTORS
Authors: ROBERTS JOAN E. , KINLEY JUDITH S. , YOUNG ANTONY R. , JENKINS GLORIA , ATHERTON STEPHEN J. , DILLON JAMES 
Published: January 2008

Abstract— Photooxidation, whether initiated by an endogenous or exogenous sensitizer, is an important mechanism in light induced damage to the lens. One of the substrates for this damage is lens protein. A porphyrin sensitizer which binds to lens proteins [mesotetra(p‐sulfonatophenyl) porphyrin (TPPS)] was found to photooxidize Skh‐2 pigmented mice lens protein in vivo. Uroporphyrin, a model for a non‐binding photosensitizer, did not induce photooxidative damage to the mouse lens.The radioprotector 3‐amino‐2‐hydroxypropyl phosphorothioate (WR‐77913) was investigated as an agent to retard or negate in vivo photooxidative damage to the lens. Intraperitoneal injections of WR‐77913 prior to irradiation reduced the TPPS induced photodestruction of lens protein in Skh‐2 pigmented mice.The mechanism of protection was also investigated. Thiols were found to quench both the triplet state of porphyrins and the reactive intermediate singlet oxygen on the order of 105 and 106M‐1 s1 respectively. These are probably not fast enough to explain most of the protection afforded by thiols. An additional mechanism may be the accelerated photobleaching of porphyrins by thiols which protects tissue by reducing the absorptions due to the porphyrins.
BIOPHOTON EMISSION (ULTRAWEAK PHOTOEMISSION) FROM DARK ADAPTED SPINACH CHLOROPLASTS
Authors: HIDEG ÈVA , INABA HUMIO 
Published: January 2008

Abstract— Biophoton emission (ultraweak photoemission) is observable in isolated spinach chloroplasts, even after several hours of dark adaptation. This spontaneous light emission is oxygen dependent, decreased by respiratory inhibitors such as cyanide or salycilhydroxamic acid, suppressed by p‐benzoquinone and enhanced by NADPH. We suggest that the respiratory chain of chloroplasts is involved in the series of redox reactions leading to the dark excitation of the emitter of biophotons, presumably chlorophyll molecules.Biophoton emission is inhibited by superoxide dismutase, implying that the univalent reduction of molecular oxygen is associated with this process, in a yet unknown way.