bluuebunny/crossref_metadata_2025 huggingface dataset:
SISTER CHROMATID EXCHANGES AND CHROMOSOME ABERRATIONS IN HUMAN CELLS INDUCED BY H2O2 AND OTHER PHOTOPRODUCTS GENERATED IN FLUORESCENT LIGHT‐EXPOSED MEDIUM
Authors: Estervig David , Wang Richard J.
Published: January 2008

Exposure of Dulbecco's modified Eagle's tissue culture medium to visible fluorescent light generated photoproducts toxic to human cells in culture. Toxicity manifested at the chromosome level was increased chromosome aberrations and sister chromatid exchanges in cells exposed to the photoproducts. Hydrogen peroxide (H2O2), a major photoproduct, induced SCE but failed to increase chromosome aberrations. Pure H2O2, or the H2O2 generated in light‐exposed medium, was necessary and sufficient for inducing all the increase in SCE. However, H2O2 was necessary but insufficient to cause most of the chromosome aberrations. Only when acting synergistically with other photoproducts did H2O, induce extensive chromosome aberrations. The relatively high cell densities at near confluence levels used in these experiments were less sensitive to light‐induced effects, nevertheless the entire light exposure dosage range effected photoproduct production adequate for inducing SCE and chromosome aberrations. Thus, mammalian tissue and cell culture media can receive sufficient dosage from fluorescent lights illuminating rooms and culture hoods for generation of photoproducts causing gross and insidious SCE and chromosome alterations.
PHOTOCHEMICAL INTERACTIONS OF CHLORPROMAZINE WITH PHOSPHOLIPIDS AND CHOLESTEROL IN ARTIFICIAL AND NATURAL MEMBRANES
Authors: TESTYLIER GUY , CLEMENT GILLES , LETERRIER FRANÇOIS
Published: January 2008

Abstract— Dipalmitoylphosphatidyl‐choline (DPPC) liposomes do not modify the nature of the photoproducts formed by UV irradiation of chlorpromazine. However, when cholesterol is added to DPPC liposomes, new photoproducts are formed which demonstrate the photoaddition of chlorpromazine to cholesterol. Similar results are obtained with phosphatidyl‐serine and phosphatidyl‐inositol. The reactivity of irradiated chlorpromazine towards lipidic components of myelin, taken as an example of biological membrane, is also demonstrated.
LEAKAGE OF 86Rb+ AFTER ULTRAVIOLET IRRADIATION OF Escherichia coli K‐12
Authors: KELLAND L. R. , Moss S. H. , DAVIES D. J. G.
Published: January 2008

Abstract— Stationary phase cultures of a DNA repair proficient Escherichia coli K‐12 strain showed a release of intracellular material as assessed by three different methods (260 nm absorption; [methyl‐3H]thymidine leakage and 86Rb+ leakage) after broad‐band (Black‐Light Blue) near‐UV radiation but not after far‐UV (254 nm) radiation. As a control response for membrane damage to cells, this leakage of intracellular material was also determined by each method after mild‐heat (52°C) treatment of E. coli K‐12. An action spectrum for the release of 86Rb+ from E. coli K‐12 after irradiation with monochromatic wavelengths, from 254 to 405 nm, is also presented. The action spectrum for lethality (F37 values) obtained for this strain, shows that leakage of 86Rb+ occurs at fluences equivalent to or slightly less than fluences causing inactivation at wavelengths above 305 nm. In contrast, at wavelengths below 305 nm, leakage of 86Rb+ from irradiated cells can be induced but only at fluences significantly greater than was required to cause cell inactivation. These results indicate, therefore, that near‐UV radiation can induce a damaging effect on the cell's permeability barrier which may be significant in causing the death of the cell, whereas the effect is not significant in causing the death of cells by far‐UV radiation where DNA damage is known to be the main cause of lethality.
PHOTOSENSITIZED PRODUCTION OF SUPEROXIDE ANION BY MONOCHROMATIC (290–405 nm) ULTRAVIOLET IRRADIATION OF NADH and NADPH COENZYMES
Authors: Cunningham Michael L. , Johnson Jennifer S. , Giovanazzi Susan M. , Peak Meyrick J.
Published: January 2008

Abstract— The reduced pyridine coenzymes NADPH and NADH produced superoxide anion(“CK”) from ground state molecular oxygen when irradiated by ultraviolet (UV) radiation extending from 290 to 405 nm as detected by cytochrome c reduction. Superoxide dismutase (SOD), but not catalase or heat‐inactivated SOD, decreased the amount of cytochrome c reduced, indicating that O2− was responsible for the reduction of cytochrome c. Decreased oxygen tension during irradiation also inhibited production of O2−. Quantum yields for the production of the anion were in the region of 10−7 to 10−9 mol per photon. These data indicate that NADH and NADPH can act as type II photosensitizers of both far‐and near‐UV radiation, and that the deleterious biological effects of exposure to these radiations such as erythema and dermal carcinogenesis may be mediated at least in part through the generation of O2−.
SEASONAL VARIATION OF SOLAR UV‐RADIATION AT A HIGH MOUNTAIN STATION
Authors: Blumthaler M. , Ambach W. , Canaval H.
Published: January 2008

Abstract— At the high mountain station Jungfraujoch (3576 m), the maximum daily totals for erythemal dose (GER), UV‐A radiation (GUVA) and global radiation (G) are 29 Sunburn Units d−1, l.7 MJ m−2d−1 and 37 MJ m−2 d−1. The maximum instantaneous values at solar noon in midsummer are 4.2 Sunburn Unit h−1, 53 W m−2 and 1110 W m−2. A significantly nonlinear relation between GER and G results from the influence of the irradiated ozone mass on the UV‐B erythemal dose. In contrast, GUVA and G are linearly proportional, which can be seen from the diurnal and seasonal courses of the ratios GER/G and GUVA/G AND from their dependence on the optical air mass. UV‐A radiation flux is less attenuated by cloudiness than is global radiation. This effect is masked for the erythemal dose by variations in the ozone concentration. Due to seasonal ozone layer thickness and effective pathlength variations, the ratio GER/G shows a significant asymmetry. At the autumn equinox it is about 16% higher than at the spring equinox.
TIME and SEQUENCE DEPENDENT INFLUENCE OF IN VITRO PHOTODYNAMIC THERAPY (PDT) SURVIVAL BY HYPERTHERMIA
Authors: Mang Thomas S. , Dougherty Thomas J.
Published: January 2008

Abstract— Experimental mouse mammary tumor cells (EMT‐6) were subjected to PDT (30 u‐g/mt DHE,620–640 nm at 3.94 mW/cnr) and hyperthermia (45.2°C, Haake FK2 waterbath) for varying lengths of time and sequences. The results show that the two modalities interact in a manner which is more cytotoxic than the sum of the individual treatments, and the sequence of administration is a determining factor in the degree of interaction. The greatest potentiation of PDT is seen when hyperthermia is administered immediately after PDT. Introducing a time interval at 37°C, between treatments, leads to a rapid loss of interaction. Analysis of dose‐response curves reveals a return of the shoulder and an increase in the D., after various incubation periods at 37°C. These data suggest that the cells accumulate and demonstrate recovery from sub‐lethal damage and also develop a tolerance to a second challenge. The appearance of stress proteins was also detected after PDT treatments, which may account for some of the phenomena observed.
ISOLATION and SPECTROSCOPIC CHARACTERIZATION OF THE B875 ANTENNA COMPLEX OF A MUTANT OF Rhodopseudomonas sphaeroides
Authors: Sebban Pierre , Robert Bruno , Jolchine Geneviève
Published: January 2008

Abstract— We describe a procedure of purification of the B875 antenna complex isolated from the 3P17 mutant strain of Rhodopseudomonas sphaeroides, enriched in B875. The integrity of this isolated complex, as well as a very low content of residual B800‐850 antenna, was suggested from low temperature absorption and resonance Raman spectra. Time resolved experiments were also carried out. The important result is the identity of the fluorescence lifetime of the B875 isolated complex (0.64 ± 0.03 ns) with that of the B875 antenna in vivo (0.63 ns), in the membrane of the C71 reaction center‐less mutant of Rhodopseudomonas sphaeroides, measured in our previous study.

Our data suggest that the interactions between the bacteriochlorophylls of the complex, as well as the constraints imposed by their protein environment are not much changed from the in vivo state.
ON INDUCED PHOTOCHROMISM OF THE C‐PHYCOCYANIN CHROMOPHORE: THE ZINC COMPLEX IN MICELLES*
Authors: Kok Jacob De
Published: January 2008

Abstract— Absorption spectra of the chromophore of C‐phycocyanin, in its free base form and as its zinc complex, were measured after denaturation with 8 M urea and with a cationic detergent. An acidic and an alkaline form of the zinc complex are distinguished. The acidic form shows photoreversible photochrom‐ism, but only when it is embedded in detergent micelles. The photochromism is tentatively ascribed to a direct photoisomerization of the chromophore.
COMPARISON BETWEEN THE LUMINOL‐DEPENDENT CHEMILUMINESCENCE OF POLYMORPHONUCLEAR LEUKOCYTES AND OF THE MYELOPEROXIDASE‐HOOH SYSTEM: INFLUENCE OF pH, CATIONS AND PROTEIN
Authors: Dahlgren C. , Briheim G.
Published: January 2008

Abstract— Measurements of luminol‐dependent chemiluminescence (CL) from normal human polymorphonuclear leukocytes (PMNL) were carried out and the results were compared to the CL obtained from a cell‐free myeloperoxidase(MPO)‐HOOH‐system.

The chemotactic peptide formylmethionyl‐leucyl‐phenyl‐alanine (fMLP) induced a bimodal luminol‐dependent CL response in PMNL, while phorbol myristate acetate (PMA) induced a one‐peak response. Calcium was found to be required for the fMLP but not for the PMA induced response. The absence of glucose reduced the PMA but not the fMLP induced PMNL CL response. Neither calcium nor glucose had any effect on the light emitted from a cell‐free MPO‐HOOH‐system.

The PMNL CL response to both fMLP and PMA was affected by the pH‐value, in that at a low pH (6.3) the response was decreased and at a high pH (8.0) the response was increased. These effects were also obtained in cell‐free MPO‐HOOH‐systems. The presence of human serum albumin (HSA) totally inhibited the CL of a cell‐free MPO‐HOOH‐system while, in PMNL CL, HSA reduced only the first phase of the fMLP induced response.

The results are discussed in view of the fact that CL is increasingly used as a clinical instrument to study defects in PMNL function and the effects on PMNL function of various agents such as drugs.
ULTRA WEAK BIOLUMINESCENCE SPECTRA OF STATIONARY PHASE Saccharomyces cerevisiae AND Schizosaccharomyces pombe
Authors: Quickenden T. I. , Comarmond M. J. , Tilbury R. N.
Published: January 2008

Abstract— Oxygenated, stationary phase cultures of the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe emit weak luminescence, most of which lies at wavelengths longer than 450 nm. Anaerobic cultures emit no detectable luminescence. The blue‐green component of the emission was attributed to excited carbonyl groups and the more intense red component was attributed to excited singlet 02‐02 dimers, both species arising from the decomposition of lipid peroxides. The higher ratio of blue:red emission in S. pombe compared with S. cerevisiae was attributed to the higher proportion of unsaturated lipids in the former yeast.
INVESTIGATION OF MIGRATION PARAMETERS OF ELECTRON EXCITATION ENERGY IN PHOTOSYNTHETIC and ARTIFICIAL SYSTEMS
Authors: Rubin L. B. , Braginskaya O. V. , Isakova M. L. , Efremov N A.
Published: January 2008

Abstract— The technique for the determination of diffusion parameters on the basis of nonlinear fluorescence quenching and excitation energy capturing by the traps is discussed. The nonstationary character of the processes of excitation capturing by traps and of singlet‐singlet annihilation which occur upon the system excitation by a picosecond pulse is taken into account. The obtained values of the diffusion parameters in the artificial pigment‐polymer antenna system (the diffusion coefficient ∼ 10‐2 cm2 s‐1 and the diffusion length ∼ 500 Å) are close to those in the photosynthesizing systems. It is also shown that the method of the determination of diffusion parameters on the basis of excitation capturing by the reaction centres may be applied for the study of the native photosynthetic systems.
BENZOFUROCOUMARINS: NEW MONOFUNCTIONAL DNA‐PHOTOBINDING AGENTS
Authors: Palumbo M. , Rodighiero P. , Gia O. , Guiotto A. , Magno S. Marciani
Published: January 2008

Abstract— The tetracyclic furocoumarin 2H‐benzofuro[3,2‐g]‐1‐benzo‐pyran‐2‐one and its 4 and/or II methyl analogues have been investigated in their DN A‐photobinding properties. Spectrophotometric and radioactivity measurements show that these compounds exhibit prominent ability to bind to the polynucleotide double helix by covalent photoaddition of the furocoumarin 3,4 double bond.

Denaturation‐renaturation experiments demonstrate that no cross‐link of DNA chains occurs. Benzopsoralens can thus be considered as a new class of monofunctional DNA‐photobinding agents.
CIDNP DETECTED FLASH PHOTOLYSIS OF cis–syn 1,3 DIMETHYLTHYMINE DIMER
Authors: Kemmink J. , Eker A. P. M. , Kaptein R.
Published: January 2008

Abstract— Theanthraquinone–2‐sulfonate photo‐sensitized splitting of cis‐syn 1,3‐dimethylthymine dimer gives rise to large CIDNP effects in the reaction product 1,3‐dimethylthymine. The polarization originates from a radical ion pair formed by electron transfer from the dimer to the triplet state sensitizer. In a deoxygenated solution the sign of the polarization of theC–6 proton is reversed compared to the predicted one on account of the CIDNP sign rules. In an aerated solution the correct sign is observed. This can be accounted for by assuming reduction of the lifetime of the radical pair in the presence of oxygen. The time‐resolved photo‐CIDNP technique was used to study the time dependence of the 1,3‐dimethylthymine signal. To account for this time‐dependence a cation radical disproportionation reaction is proposed.
EFFECTIVENESS OF UV‐B RADIATION ON THE GROWTH AND PHYSIOLOGY OF FIELD‐GROWN SOYBEAN MODIFIED BY WATER STRESS
Authors: Murali N. S. , Teramura Alan H.
Published: January 2008

Abstract— Soybeans [Glycine max (L) Merr. cv Essex] were grown in field plots during May‐October 1985 under ambient and an enhanced level of ultraviolet‐B (UV‐B) radiation (supplemental daily dose: 5.1 effective kJ m‐2). They were either subjected to water stress or supplementally irrigated, resulting in a 2.0 MPa lower soil water potential in stressed plots. Increased levels of UV‐B radiation reduced leaf area, total plant dry weight and net photosynthesis under well‐watered conditions, but no significant UV‐B effects were detected in plants concurrently subjected to water stress. The insensitivity of growth and net photosynthesis to UV‐B radiation in water‐stressed plants may be related to anatomical and biochemical changes induced by water stress. These include an increase in the concentration of UV absorbing compounds in leaf tissues and leaf thickening.
VACUUM UV CIRCULAR DICHROISM OF POLYSACCHARIDES
Authors: Stevens Eugene S.
Published: January 2008

Polysaccharides are of great commercial and biological importance. At the molecular level they display a richness in structural and conformational variability, and helical structures are commonplace. Of the various experimental techniques applicable to the study of polysaccharide conformation, optical spectroscopy has been limited by the relatively high energy of the electronic excitations, the first excitation in unsubstituted saccharides being in the vacuum ultraviolet region. In the past decade, the development of VUV CD spectrometers, including the use of synchrotron radiation, has allowed the chiroptical properties of polysaccharides to be observed directly. In this brief review the major CD features of polysaccharides are summarized, and several applications are described illustrating the usefulness of VUV CD spectroscopy in the study of the polysaccharide conformation. Examples include the glucans, dextran and acetylated cellulose; the glycosaminoglycan, heparin; and the microbial polysaccharides, gellan and xanthan. A recently proposed quadrant rule which describes the sign of the 175 nm n‐σ* polysaccharide CD band also is discussed. This rule is the first attempt to place the descriptionof polysaccharide VUV CD on a theoretical foundation.
GLOBAL ANALYSIS OF FLUORESCENCE DECAY: APPLICATIONS TO SOME UNUSUAL EXPERIMENTAL AND THEORETICAL STUDIES
Authors: Beechem Joseph M. , Brand Ludwig
Published: January 2008

The methodology for the simultaneous analysis of fluorescence decay curves is shown to create the possibility for some new types of fluorescence decay experiments. These new experiments include the use of the T‐format in anisotropy experiments without the need to match the timing characteristics of photomultiplier tubes. Decay surfaces obtained at multiple timing calibrations can be analyzed simultaneously to resolve widely differing decay rates. Methodologies are described for the discrimination of associative from nonassociative behavior for multiexponential anisotropy decay. A systems theory approach to the analysis of excited state reactions is described.
THE TIME‐RESOLVED PHOTON‐COUNTING FLUOROMETER AT THE NATIONAL SYNCHROTRON LIGHT.SOURCE
Authors: Laws William R. , Sutherland John Clark
Published: January 2008

A single‐photon‐counting fluorometer, capable of steady‐state and time‐dependent measure‐ments, is now operational at port U9B of the National Synchrotron Light Source at Brookhaven National Laboratory. Excitation wavelengths are selected by a prism‐grating double monochromator. Emission energies are chosen by filter(s) or by a one‐meter Spex monochromator. Commercial electronics are used for data acquisition, except for special circuitry required by the high (53 MHz) repetition rate of the synchrotron. A large sample chamber allows flexibility in arranging optical components and samples. The standard optical configuration of the sample chamber consists of a focusing mirror, a six position excitation optic wheel, a turntable with four thermostatted cuvette holders, a six position emission optic wheel, and an f/0.7 emission collection lens. Data acquisition and the setting of correct wavelengths and sample chamber optics are controlled by a Tektronix 4052 computer via the IEEE‐488 General Purpose Interface Bus. Time‐dependent fluorescence data are transferred to a VAX 11/730 for analysis; current deconvolution software includes nonlinear least‐squares programs for single curve and global analysis.
A NEW APPROACH TO THE OBSERVATION OF THE RESIST IN X‐RAY CONTACT MICROSCOPY
Authors: Shinohara Kunio , Aoki Sadao , Yanagihara Mihiro , Yagishita Akira , Iguchi Yasuo , Tanaka Akira
Published: January 2008

X‐ray microscopy is one of the useful applications of synchrotron radiation researches, and at present, X‐ray contact microscopy is the best developed method in this field. The images on the resist in X‐ray contact microscopy have been observed with a scanning electron microscope, and there have been some attempts to use the transmission electron microscope, but few have used the replica method. We have applied the replica method with plasma polymerization‐film to observe X‐ray images on the resist with a transmission electron microscope and found it to be applicable.

A long exposure time is required when we use the monochromatic synchrotron radiation with a grasshopper monochromator. Our preliminary experiments with a new light source, undulator radiation, showed that it is very intense and useful for X‐ray contact microscopy.
THE VASCULAR RESPONSE OF HUMAN SKIN TO ULTRAVIOLET RADIATION
Authors: Farr P. M. , Diffey B. L.
Published: January 2008

The vascular response of human skin to 300 nm (UV‐B) and 254 nm (UV‐C) ultraviolet radiation was assessed using the reflectance measurement of erythema and the technique of laser Doppler velocimetry. For both wavelengths, the increase in measured Doppler blood flux varied with the increase in erythema in a quadratic manner predicted by a simple model based on the principles of fluid mechanics. This suggests that the mean red blood cell velocity increases significantly in areas of UV‐B and UV‐C erythema. No qualitative difference in response to these two wavelengths was demonstrated, suggesting that the same blood vessels are involved in the causation of both UV‐B and UV‐C erythema.
GENETIC EFFECTS OF UV‐B: MUTAGENICITY OF 308 nm LIGHT IN CHINESE HAMSTER V79 CELLS
Authors: Colella Carlo M. , Bogani Patrizia , Agati Giovanni , Fusi Franco
Published: January 2008

Abstract —Chinese hamster V79 cells were irradiated with 254 nm (UV‐C) and 308 nm (UV‐B) light, emitted by a germicidal lamp and an excimer laser, respectively. Induction of mutations at two distinct genetic loci was measured by selecting colonies resistant to 6‐thioguanine or to ouabain. Unlike 6‐thioguanine resistance which can be presumed to be due to many different types of genetic damage, mutation to ouabain resistance seems to result from base‐pair substitution events only. Much higher doses of 308 than of 254 nm radiation are required to induce equivalent numbers of mutants. However, induction of cell inactivation and 6‐thioguanine resistant mutations with the two UV sources appears to be correlated, suggesting that a common mechanism, perhaps involving the induction of pyrimidine‐containing dimers, is involved. The frequency of ouabain resistant mutants per lethal event is on the other hand much higher after irradiation with the 308 nm light. This latter finding further defines a part of the UV‐B spectral region which seems to induce a unique kind of DNA damage which specifically results in base‐pair substitution events. Action spectra studies therefore appear necessary in the definition of the mutagenic effects of UV‐B radiations in mammalian cells.
PHOTOPHYSICAL PARAMETERS OF CHLOROPHYLLS a AND b·FLUORESCENCE AND LASER‐INDUCED OPTOACOUSTIC MEASUREMENTS
Authors: Jabben Merten , Garcia Norman A. , Braslavsky Silvia E. , Schaffner Kurt
Published: January 2008

Abstract— The quantum yields of internal conversion (energy loss) of the photoexcited chlorophylls a and b in ethanol at 24°C have been determined by measuring the quantum yields of the competing radiative (fluorescence) and non‐radiative (intersystem crossing) deactivation processes (which lead to energy storing species) by means of emission and laser‐induced optoacoustic spectroscopy, respectively. The values for internal conversion of chlorophyll a are 10% and 14% in the presence and absence of molecular oxygen, respectively. The corresponding yields for chlorophyll b are negligibly small. The internal conversion in chlorophyll a is attributed to vibronic coupling with the substituents of the porphin system, since internal conversion was found to be substantially reduced for unsubstituted Mg‐porphin in ethanol and for chlorophyll a when dissolved in a viscous medium.
FREE RADICALS FROM PHOTODECOMPOSITION OF BISPHENOL‐A
Authors: Peltonen Kimmo , Zitting Antti , Koskinen Heimo , Itkonen Ahti
Published: January 2008

Abstract— Irradiation of 2,2‐bis‐(4‐hydroxyphenyl)‐propane (bisphenol‐A) with UV light causes photo‐decomposition of the compound. Spin‐trapping with α‐phenyl‐N‐tert‐butyl‐nitrone showed that free radicals were cleaved from the molecule. No direct ESR‐spectroscopic information concerning the structure of the remaining radical skeleton could be obtained. Gas chromatographic mass spectrometric analysis of the decomposition products indicated the existence of a semiquinone structure following cleavage of a methyl radical from 2,2‐bis‐4–(hydroxyphenyl)‐propane. The capacity of 2,2‐bis‐(4‐hydroxyphenyl)‐propane to give rise to radicals might explain its photoallergenic properties.
FLUORESCENCE LIFETIMES OF ANGULAR FUROCOUMARINS
Authors: Andreoni A. , Cubeddu R. , Knox C. N. , Truscott T. G.
Published: January 2008

Properties of singlet states of a range of non‐substituted and aceto‐substituted angular furocoumarins as investigated by the technique of time‐resolved fluorescence are reported. In the three solvents studied, water, ethanol and benzene, a variety of 1, 2 or 3 fluorescence lifetime components were found and resolved, the importance of which varied in the different media. No correlation or marked variation could be observed for this lifetime data with either solute concentration or excitation wavelength. The results are discussed with respect to triplet quantum yields and to the possible role of the close proximity of various excited singlet states.
STUDIES ON THE STRUCTURE OF PORPHYRINS CONTAINED IN PHOTOFRIN® II
Authors: Dougherty Thomas J.
Published: January 2008

Abstract Using three methods to attempt to identify the presence of ester‐linked porphyrins in Photofrin® II, lithium aluminum hydride reduction, basic hydrolysis and proton NMR. it can be concluded that 40‐50% of such linkages are present. The majority of the remaining material is cleaved by acid hydrolysis, which is consistent with the ether structure proposed earlier. earlier.
ALUMINUM SULFONATED PHTHALOCYANINE DISTRIBUTION IN RODENT TUMORS OF THE COLON, BRAIN and PANCREAS
Authors: Tralau C. J. , Barr H. , Sandeman D. R. , Barton T. , Lewin M. R. , Bown S. G.
Published: January 2008

Abstract The most widely discussed aspect of photodynamic therapy (PDT) is the preferential uptake and retention of sensitisers by malignant tissues. The sensitiser usually used is hematoporphyrin derivative (HPD) but this compound is not an ideal photosensitiser for this purpose and we have therefore studied an aluminum sulfonated phthalocyanine (AlSPc) as a possible alternative. Here we have studied the uptake and retention of this compound in a rat colon cancer, a hamster pancreatic cancer and a mouse glioma, using an alkali extraction technique to estimate tissue AlSPc and comparing the results with those from the corresponding normal tissues. All of the tumors studied reached accumulation peaks at 24‐48 h after intravenous administration of AlSPc compared with peaks at 1‐3 h in the normal tissues. The tumors outside the central nervous system (CNS) reached peak tumor : normal tissue ratios of 2‐3 : 1 and the tumor within the CNS, the malignant glioma, reached a far higher ratio of 28 : 1. These ratios are similar to those reported by others using HPD.
THE INFLUENCE OF SODIUM PENTOBARBITAL ANESTHESIA ON in vivo PHOTODYNAMIC THERAPY
Authors: Gomer Charles J. , Hayashi Naganobu , Murphree A. Linn
Published: January 2008

Abstract The use of sodium pentobarbital anesthesia 50 jig gm−1 during localized photodynamic therapy (PDT) was examined in C57BL/6 mice transplanted with the pigmented B‐16 melanoma. A 10 mg kg−1 i.p. injection of Photofrin II was administered 24 h prior to light exposure (630 nm, 150 mW, cm−2, 300‐500 J cm−2). Separate groups of mice were utilized to monitor tumour temperature and PDT tumor response. Core tumor temperatures decreased by approx. 10oC following sodium pentobarbital administration. Tumor responses were determined by documenting the percentage of treated animals without tumor recurrences for a period of 50 days following PDT. Superior PDT induced tumor responses were obtained in control (non‐anesthetized) mice following light doses of 400 and 500 J cm−2. The results of this study indicate that sodium pentobarbital can induce a protective effect on B‐16 melanomas treated with PDT.
PHOTOCHEMICAL COUPLING OF 5‐BROMOURACIL TO TRYPTOPHAN, TYROSINE AND HISTIDINE, PEPTIDE‐LIKE DERIVATIVES IN AQUEOUS FLUID SOLUTION
Authors: Dietz Timothy M. , Koch Tad H.
Published: January 2008

Direct irradiation of 5‐bromouracil (BU) in aqueous fluid solution in the presence of tryptophan (trp), tyrosine (tyr) or histidine (his) derivatives using a XeCl excimer laser at 308 nm yielded photocoupling of BU to the aromatic ring of each amino acid. Irradiation of BU at 308 nm most likely results in excitation of the n‐φ* transition, intersystem crossing to the triplet manifold, and coupling via electron transfer from the aromatic amino acid. The coupling observed was regiospecific between the 5‐position of uracil (U) and the 2‐position of the indole and phenol rings and the 5‐position of the imidazole ring of the respective amino acids. Quantum yields of photocoupling to BU ranged from 1 × 10‐3 to 7 × 10‐3 and paralleled known rates of electron transfer and ionization potentials of the aromatic rings. The photocoupling between BU and some of the aromatic amino acid peptide‐like derivatives possibly mimics photocrosslinking of BU‐DNA to associated proteins, a potentially useful photoreaction for studying nucleic acid‐protein interactions. Formation of crosslinks of the type proposed here might be detected by the characteristic fluorescence emission of the uracil amino acid adducts.
PHOTOKINETIC AND PHOTOPHYSICAL MEASUREMENTS OF THE SENSITIZED PHOTOOXIDATION OF THE TRYPTOPHYL RESIDUE IN N‐ACETYL TRYPTOPHANAMIDE AND IN HUMAN SERUM ALBUMIN
Authors: Reddi E. , Lambert C. R. , Jori G. , Rodgers M. A. J.
Published: January 2008

Abstract— The photosensitized oxidation of 10–100 μM N‐acetyl‐L‐tryptophanamide (NATA) in neutral aqueous solution and in the presence of various dyes proceeds by a pure O2(1Δg)‐involving mechanism. Incorporation of the tryptophyl (Trp) residue into the polypeptide chain of human serum albumin (HSA) has no influence on the mechanism and efficiency of Trp photooxidation when sensitized either by methylene blue, a non‐binding dye, or by rose bengal, a dye that gives non‐covalent 1: 1 complexes with HSA. This is due to the location of the Trp residue in close proximity of the protein surface and, in the case of rose bengal, to the coincidence of the photophysical properties (including the quantum yield of O2(1Δg) generation) for the free and HSA‐bound dye. Hematoporphyrin also binds to HSA with 1: 1 stoichiometry, although at a different site from rose bengal. Bound Hp again displays photophysical properties very similar with those of free Hp; however, the efficiency of Trp photo‐oxidation in HSA is about 5‐fold higher than in NATA owing to a limited rearrangement of the protein structure, induced by Hp binding, which enhances the probability of chemical quenching of O2(1Δg) by the indole ring.
PICOSECOND RESOLUTION OF INDOLE ANISOTROPY DECAYS AND SPECTRAL RELAXATION BY 2 GHz FREQUENCY‐DOMAIN FLUOROMETRY
Authors: Lakowicz Joseph R. , Szmacinski Henryk , Gryczynski Ignacy
Published: January 2008

Abstract— We used frequency‐domain fluorescence spectroscopy to measure rotational diffusion and time‐resolved emission spectra of indole in methanol on the picosecond timescale. The indole emission was quenched by acrylamide to allow measurements to the instrumental limit of 2 GHz and to eliminate emission from the longer‐lived indole molecules, which can no longer provide information on the picosecond (ps) processes. The resolution was adequate to measure rotational correlation times as short as 8 ps at 80†C, and spectral relaxation times as short as 16 ps at 5†C.
CHEMICALLY MODIFIED PHOTOSYNTHETIC BACTERIAL REACTION CENTERS: CIRCULAR DICHROISM, RAMAN RESONANCE, LOW TEMPERATURE ABSORPTION, FLUORESCENCE AND ODMR SPECTRA AND POLYPEPTIDE COMPOSITION OF BOROHYDRIDE TREATED REACTION CENTERS FROM Rhodobacter sphaeroides R26
Authors: Beese D. , Steiner R. , Scheer H. , Angerhofer A. , Robert B. , Lutz M.
Published: January 2008

Abstract— Reaction centers from Rhodobacter sphaeroides have been modified by treatment with sodium borohydride similar to the original procedure [Ditson et al., Biochim. Biophys. Acta766, 623 (1984)], and investigated spectroscopically and by gel electrophoresis.

(1) Low temperature (1.2 K) absorption, fluorescence, absorption‐ and fluorescence‐detected ODMR, and microwave‐induced singlet‐triplet absorption difference spectra (MIA) suggest that the treatment produces a spectroscopically homogeneous preparation with one of the ‘additional’ bacteriochlorophylls being removed. The modification does not alter the zero field splitting parameters of the primary donor triplet (TP870).

(2) From the circular dichroism and Raman resonance spectra in the1500–1800 cm‐1 region, the removed pigment is assigned to BchlM, e.g. the “extra” Bchl on the “inactive” M‐branch.

(3) A strong coupling among all pigment molecules is deduced from the circular dichroism spectra, because pronounced band‐shifts and/or intensity changes occur in the spectral components assigned to all pigments. This is supported by distinct differences among the MIA spectra of untreated and modified reaction centers, as well as by Raman resonance.

(4) The modification is accompanied by partial proteolytic cleavage of the M‐subunit. The preparation is thus spectroscopically homogeneous, but biochemically heterogenous.
ISOLATION AND CHARACTERIZATION OF A MARSUPIAL DNA PHOTOLYASE
Authors: Sabourin Carol L. K. , Ley Ronald D.
Published: January 2008

Abstract— Post UV‐B(280–320 nm) exposure to UV‐A(320–400 nm) reverses pyrimidine dimers in the epidermal DNA of the South American opossum Monodelphis domestica [Ley, R. D. (1984) photorepair of pyrimidine dimers in the epidermis of the marsupial Monodelphis domestica. Photochem. Photobiol. 40,141–143.] To demonstrate that the observed photorepair is mediated by an enzyme, we have isolated a DNA photolyase from the opossum. DNA photolyase from liver was purified 3000‐fold by ammonium sulfate fractionation and phenylsepharose, hydroxylapatite, DEAE‐cellulose and DNA‐cellulose column chromatography. Heat denaturation (60°C for 4 min) completely eliminated the photoreactivating activity. The enzyme was active in the pH range of 5.5 to 8.5 with a pH optimum of 7.5. The enzyme has an apparent molecular weight of 32 000 under nondenaturing conditions. The activity of the enzyme was not affected by sodium chloride up to 250 mM. The action spectrum for the purified DNA photolyase showed activity in the range of325–475 nm with peak actvity at 375 nm.
RESONANCE RAMAN SPECTRA OF THE Pr‐FORM OF PHYTOCHROME
Authors: Fodor Stephen P. A. , Lagarias J. Clark , Mathies Richard A.
Published: January 2008

Abstract— Resonance Raman spectra of the Pr‐form of oat phytochrome have been obtained at 77 K. Interference from phytochrome fluorescence is avoided by employing far‐red 752 nm excitation. Vibrational assignments are suggested for the tetrapyrrole chromophore in phytochrome by comparison with previously published model compound spectra and by examining the characteristic shifts induced by deuteration of the pyrrole nitrogens. The lack of carbonyl intensity, the frequencies of the 1626 and 1644 cm‐1 C=C stretching modes, and the presence of an intense mode at 1326 cm‐1 are all consistent with a protonated structure for the tetrapyrrole chromophore in Pr. This suggests that the ‐50 nm red‐shift of the protein‐bound chromophore absorption compared to the chromophore in vitro is caused by protonation of the pyrrole nitrogen.
PHOTOREACTIVATION OF KILLING INE. coliK–12 phr‐ CELLS IS NOT CAUSED BY PYRIMIDINE DIMER REVERSAL
Authors: Husain Intisar , Carrier William L. , Regan James D. , Sancar Aziz
Published: January 2008

Abstract— Escherichia coliK–12 strains deleted in the phr gene which encodes the apoenzyme of photolyase show significant residual photoreactivation activity after exposure to high photoreactivating light doses. We show that this photoreactivation of killing is not associated with reversal of pyrimidine dimers and conclude that the effect is probably attributable to the direct photoconversion of the6–4 photoproducts to their Dewar isomers (Type III photoreactivation).
INVESTIGATIONS ON BIOLOGICAL EFFECT OF POLARIZED LIGHT
Authors: Kubasova Tamara , Fenyö Márta , Somosy Zoltán , GAZSÓ Lajos , Kertész Iván
Published: January 2008

Abstract— The biological effects of single and 4‐time irradiation of primary human embryo fibroblasts with 4 J/cm2 polarized light emitted by a halogen light source were investigated. The functional state of the plasma membrane was examined by means of lectin‐binding and polycationized ferritin‐binding techniques. It was established that the Con A binding of the cells did not change, whereas the number of negatively charged binding sites increased to a significant degree in relation to the untreated (control) samples and cell cultures exposed to diffuse (non‐polarized) light. The micromorphological examinations showed no ultrastructural deviations. The quantitative increase of negative surface charges may be regarded as an indication of the biological effect of polarized light exerted on the cell membrane. The modifying effect of polarized light on the survival of E. coli exposed to the ionizing radiation was manifested in decreased anoxic radiation response.
SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS‐XIII. pH DEPENDENCE OF THE PHOTOCHEMISTRY OF PHOTO ALLERGENS BITHIONOL AND FENTICHLOR: AN ELECTRON spIN RESONANCE STUDY OF THE FREE RADICAL PHOTOPRODUCTS
Authors: LI ANSON S. W. , CHIGNELL COLIN F.
Published: January 2008

Abstract The photoallergens bithionol (BT) and fentichlor (FT) generated free radical photoproducts upon UV photolysis which were observable by direct electron spin resonance (ESR). Both the yield and the type of free radical photoproducts were affected by pH, and to some extent, concentration of oxygen and concentrations of the photosensitizers. At pH 8.5, bithionol (0.9 mM) generated a semiquinone type free radical (BI) via a mechanism which probably involves substitution of the 4‐chlorine by hydroxyl to form the corresponding hydroquinone followed by oxidation. The photolysis of 4‐chlorophenol, 4‐chlorocatechol and 2,2'‐methylene‐bis(4‐chlorophenol) also generated the corresponding semiquinone radicals, suggesting that this mechanism is shared by other 4‐chlorophenols. At pH 8.5, only photoproduct BI was observed during the irradiation of BT; FT related photoproducts were not observed at this pH. However, at higher pH values (pH 10.7 or pH 12), FT photoproducts were also observed in addition to BI upon prolonged irradiation. Moreover, the yield of BI increased drastically at higher pH. Oxygen did not play any role at pH 10.7, although it enhanced the yield of BI at pH 8.5. At pH 8.5, irradiated fentichlor generated, in roughly equal amounts, a semiquinone radical (Fla) and an unidentified species which contained two inequivalent protons (FII). At higher pH values (pH 10.7 and pH 12), at least four species were observed. All of the species are believed to be semiquinone radicals and two have been unambiguously identified. The yield of FI increased by a factor of 50 as the pH was increased from 8.5 to 12. Oxygen played only a minor role at pH 10.7 and above. However, at pH 8.5, it also enhanced the yield of FI.
PHOTOCHEMICAL REDUCTION OF 5‐BROMOURACIL BY CYSTEINE DERIVATIVES AND COUPLING OF 5‐BROMOURACIL TO CYSTINE DERIVATIVES
Authors: DIETZ TIMOTHY M. , KOCH TAD H.
Published: January 2008

Abstract Irradiation of pH 7, aqueous solutions of 5‐bromouracil (BU) in the presence of cysteine peptide‐like derivatives at 308 nm using a XeCl excimer laser yielded initial formation of only uracil (U) and the corresponding cystine derivative. Continued irradiation yielded an S‐uracilylcysteinyl adduct as well as additional U and cystine derivative. Similar irradiation of a solution of BU and a cystine derivative yielded initial formation of U and the S‐uracilylcysteinyl adduct. Formation of these products as well as secondary products of uracil photochemistry was observed upon irradiation of the respective solutions with 254 nm light. With 308 nm laser excitation, U‐Cys adduct formation and reduction of BU to U are proposed to occur via initial electron transfer from the disulfide of the cystine derivative to triplet BU. The quantum yield of BU destruction with 308 nm excitation in the presence of cystine derivative is 1.1 × 10‐3. Reaction of triplet BU with the cysteine derivative does not yield U‐Cys adduct but U and cystine derivative. A possible byproduct of reduction of triplet BU to U by a cysteinyl residue in a protein BU‐DNA complex is a sulphenyl bromide which might yield a protein‐DNA crosslink via nucleophilic substitution on sulfur by a nucleophilic site in DNA.
INDUCTION OF LAMBDA PROPHAGE NEAR THE SITE OF FOCUSED UV LASER RADIATION
Authors: MATCHETTE L. S. , WAYNANT R. W. , ROYSTON D. D. , HITCHINS V. M. , ELESPURU R. K.
Published: January 2008

Abstract DNA damage from photon scatter or beam spread during UV excimer laser irradiation was investigated using the induction of bacteriophage lambda in E. coli BR339. Prophage induction in these cells leads to the production of β‐galactosidase which can be detected colorimetrically by the application of appropriate substrates. An agar surface overlayed with BR339 cells was placed at various distances from the focal point of a converging lens and exposed to either 193 or 248 nm laser radiation. Energy densities ranging from approximately 5 mJ/cm2 to 30 J/cm2 were used. Ablation with 193 nm laser radiation produced an 800 u, m wide clear ‘trench’ surrounded by a 500 μm zone of cells in which lambda had been induced. Following ablation with 248 nm laser radiation, the zone of induction was several millimeters wide. Exposures to 193 nm radiation at 170 mJ/cm2/pulse produced visible ablation of the agar surface at 1.7 J/cm2. Lambda induction was observed surrounding cleared ablation areas. The presence of induction in this system suggests that both 248 and 193 nm excimer laser radiation delivered at high energy densities has sufficient spread or scatter to damage DNA in cells surrounding areas of ablation.
UROCANIC ACID AND IMMUNOSUPPRESSION
Authors: Norval M. , Simpson T. J. , Ross J. A.
Published: January 2008

Abstract—

Urocanic acid, a molecule found at high concentration in the stratum corneum, acts as a photoreceptor for UV‐light, isomerizing from the naturally occurring trans‐lorm to the cis‐form. It has been proposed that cis‐urocanic acid may mediate the transient alteration in immune surveillance resulting in immunosuppression induced after UV‐irradiation, by interacting with immune cells locally and/or systemically to generate T cells with suppressor function. The evidence to support this hypothesis is summarized, and possible interactions of urocanic acid with immune cells and their outcome are discussed.
EFFECT OF LIGHT AND TRITON X‐100 ON THE SIZE OF PROTOPLASTS FROM Ulothrix gigas
Authors: Davies Eric , Kuczmarski Dan
Published: January 2008

Abstract— An electronic particle‐size analyzer (Coulter Counter with Channelyzer) was used both to monitor the purity of large numbers of protoplasts during sequential steps in their isolation from Ulothrix gigas and also to detect changes in volume (swelling or growth) after incubation of purified protoplasts under various conditions.

Protoplasts almost devoid of contaminating debris, but heterogenous in size, were obtained by pelleting partly‐purified protoplasts through sucrose solutions. Pure protoplasts of discrete sizes were obtained by centrifuging these resuspended protoplasts on iso‐osmotic mannitol/sucrose gradients. The protoplasts were shown to enlarge (swell) and then burst when transferred to increasingly hypotonic solutions or when incubated in Triton X‐100.

The rate of protoplast enlargement (growth) was also monitored on the Coulter Counter and differences in size of large populations were discernible within 2 h in protoplasts incubated under low light, and growth rates of such protoplasts could be assessed for up to 36 h.

The Coulter Counter provides a rapid, reproducible and sensitive method for measuring the size distribution of large numbers of protoplasts. This, combined with the techniques described here for the isolation of protoplasts from V. gigas in high yield and purity, provides a system eminently suitable for investigating a wide array of physiological and developmental processes in plant protoplasts.
UV‐B EFFECTS ON TERRESTRIAL PLANTS
Authors: Tevini Manfred , Teramura Alan H.
Published: January 2008

The potential impacts of an increase in solar UV‐B radiation reaching the Earth's surface due to stratospheric ozone depletion have been investigated by several research groups during the last 15 years. Much of this research has centered on the effects of plant growth and physiology under artificial UV‐B irradiation supplied to plants in growth chambers or greenhouses. Since these artificial sources do not precisely match the solar spectrum and due to the wavelength dependency of photobiol‐ogical processes, weighting functions, based on action spectra for specific responses, have been developed to assess the biological effectiveness of the irradiation sources and of predicted ozone depletion. Recent experiments have also utilized artificially produced ozone cuvettes to filter natural solar radiation and simulate an environment of reduced UV‐B for comparative purposes.

Overall, the effectiveness of UV‐B varies both among species and among cultivars of a given species. Sensitive plants often exhibit reduced growth (plant height, dry weight, leaf area, etc.), photosynthetic activity and flowering. Competitive interactions may also be altered indirectly by differential growth responses. Photosynthetic activity may be reduced by direct effects on photosynthetic enzymes, metabolic pathways or indirectly through effects on photosynthetic pigments or stomatal function. The fluence response of these changes has yet to be clearly demonstrated in most cases. Plants sensitive to UV‐B may also respond by accumulating UV‐absorbing compounds in their outer tissue layers, which presumably protect sensitive targets from UV damage. Several key enzymes in the biosynthetic pathways of these compounds have been shown to be specifically induced by UV‐B irradiation.

Few studies have documented the effects of UV‐B on total plant yield under field conditions. One notable exception is a 6‐yr study with soybean demonstrating harvestable yield reductions under a simulated 25% ozone depletion. These effects are further modified by prevailing microclimatic conditions. Plants tend to be less sensitive to UV‐B radiation under drought or mineral deficiency, while sensitivity increases under low levels of visible light. Further studies are needed to understand the mechanisms of UV‐B effects and the interactions with present stresses and future projected changes in the environment.
FLUORESCENCE SPECTRA IN LUNG WITH PORPHYRIN INJECTION
Authors: ANTHONY D. J. , PROFIO A. E. , BALCHUM O. J.
Published: January 2008

Abstract

The fluorescence emission spectra from human bronchial mucosa and tumors, before and after injection of dihematoporphyrin ether/ester, have been measured with an optical multichannel analyzer from 500 to 750 nm. Fluorescence was excited with a violet krypton ion laser (average wavelength 410 nm). The autofluorescence spectra decrease monotonically with increasing wavelength except for a small broad peak near 600 nm. The spectra from tumor sites, after injection of the fluorescent porphyrin, exhibit the characteristic fluorescence emission at 630 and 690 nm, added to the autofluorescence spectrum. The spectra from control or nontumor sites are similar but the magnitude of the component due to the injected porphyrin is smaller than at a tumor site. The magnitude ratio of tumor to control site fluorescence depends on concentration of the porphyrin, tumor thickness, and time after injection. Autofluorescence degrades contrast and thus makes very thin tumors difficult to image. Subtraction of the autofluorescence background is desirable.
SENSITIZATION OF THE NORBORNADIENE TO QUADRICYCLENE CONVERSION BY SUBSTITUTED BENZOPHENONES: EVIDENCE AGAINST BIRADICAL INTERMEDIACY
Authors: Gorman A. A. , Hamblett I. , McNeeney S. P.
Published: January 2008

Abstract— The light‐induced reactions of 4,4'‐dimethoxybenzophenone, benzophenone and 4,4'‐dichlo‐robenzophenone with norbornadiene and quadricyclene have been examined in time‐resolved and steady‐state modes with both acetonitrile and benzene as solvent. It is clearly demonstrated that in all cases formation of quadricyclene as a consequence of bimolccular reaction between ketone triplet and norbornadiene does not proceed via the intermediacy of an adduct biradical as has been recently proposed.