bluuebunny/crossref_metadata_2025 huggingface dataset:
EXCITATION OF MESOPHYLL AND BUNDLE SHEATH CHLOROPLASTS OF Atriplex repanda IN THE ABSENCE OF LIGHT
Authors: SILVA EDUARDO , RODRÍGUEZ GLADYS , FALJONI ADELAIDE , CILENTO GIUSEPPE
Published: January 2008

Abstract— Mesophyll and bundle sheath chloroplasts isolated from Atriplex repanda cells promote oxygen consumption by isobutyraldehyde or phenylacetaldehyde. In all cases, a red emission and reduction of tetrazolium blue was observed. Addition of horseradish peroxidase greatly increases the reduction of the dye. In the presence of 3‐(3, 4‐dichlorophenyl)‐1, 1‐dimethylurea, the reduction of the Hill acceptor was fully suppressed. This suppression was abolished when 2, 6‐dichlorophenolindophenol and ascorbate were added to the systems. These results indicate that, in mesophyll and bundle sheath chloroplasts, chlorophylls can be efficiently excited in the absence of light and an electron flow through the photosystems can be promoted.
PROPERTIES OF CREMOPHOR EL MICELLES PROBED BY FLUORESCENCE
Authors: Kessel David
Published: January 2008

Abstract—

Using 1‐anilino,8‐naphthalenesulfonic acid (ANS) as a probe, we examined properties of micelles of Cremophor EL, an amphipathic agent which can solubilize hydrophobic photosensitizing agents and promote their distribution to plasma lipoprotein. In aqueous solution, Cremophor micelles persisted for several hours after dilution below the critical micellar concentration (CMC). After equilibrium was reached, we found a CMC of 0.009% (wt/vol). Fluorescence data suggest that the micellar environment of ANS binding has a dielectric constant of approximately 27. Cremophor also reverses examples of multi‐drug resistance associated with impaired accumulation of anti‐tumor agents, e.g. daunorubicin. Although the latter drug is relatively hydrophilic, fluorescence spectroscopy and anisotropy studies indicate an association with Cremophor. Moreover, resistance reversal occurred only at Cremophor concentrations above the CMC.
EXTENSION GROWTH AND ANTHOCYANIN RESPONSES OF PHOTOMORPHOGENIC TOMATO MUTANTS TO CHANGES IN THE PHYTOCHROME: PHOTOEQUILIBRIUM DURING THE DAILY PHOTOPERIOD
Authors: Kerckhoffs L. H. J. , Kendrick R. E. , Whitelam G. C. , Smith H.
Published: January 2008

Abstract—

Four genotypes of tomato (Lycopersicon esculentum Mill.) in the genetic background ‘Aha Craig’ were used: an aurea (au) mutant, deficient in the bulk light‐labile phytochrome pool; a high pigment (hp) mutant, showing exaggerated phytochrome responses at the time of de‐etiolation; the au,hp double mutant and the isogenic wild type (WT). A dramatic increase in plant height resulting from an increase in the length of all internodes for each of the genotypes studied was observed upon reduction of the red light: far‐red light photon ratio (R:FR) from 6.90 to 0.13 by addition of FR for the whole photoperiod. A concomitant increase in leaf length was also observed. Since au and au,hp mutants, deficient in the bulk light‐labile phytochrome pool, respond to this reduction in the R:FR these data demonstrate that the phytochrome pool that mediates this response is present and fully functional. Anthocyanin was detectable in the comparably developed young growing leaves of the WT and hp mutant under the high R:FR, but not in the au and au,hp mutants, suggesting that the potential for anthocyanin synthesis is correlated with the presence of the bulk light‐labile phytochrome pool. The kinetics of anthocyanin decrease in the young growing leaves were investigated in the hp mutant and the results suggest a very rapid cessation of flavonoid biosynthesis upon reduction of the R:FR. The functions of different phytochrome types are discussed.
PHOTOMORPHOGENIC RESPONSES TO UV RADIATION. II: A COMPARATIVE STUDY OF UV EFFECTS ON HYPOCOTYL ELONGATION IN A WILD‐TYPE AND AN aurea MUTANT OF TOMATO (Lycopersicon esculentum Mill.)
Authors: Lercari Bartolomeo , Sodi Francesco
Published: January 2008

Abstract—

Hypocotyl growth in etiolated seedlings of wild‐type and an aurea mutant of tomato (Lycopersicon esculenturn Mill.), that appears to be deficient in labile phytochrome, is strongly inhibited by UV radiation in the region of 300–400 nm. The role of phytochrome in the UV‐mediated inhibition of hypocotyl growth was studied using different experimental approaches: (1) by comparing the effectiveness of treatments of increasing duration of exposure to 692 nm and UV radiation; (2) by modifying the UV spectral range with specific cut‐off filters. The experimental results suggest that the UV‐induced inhibition of growth in wild‐type tomato is mediated to a large extent by the longer wavelengths of the UV‐A region and is mediated mainly by phytochrome. In contrast, at wavelengths < 305 nm a strong UV‐B effect was found in the aurea mutant, suggesting a preeminent action of a specific UV‐B absorbing photoreceptor that displays less action in the wild‐type.
INACTIVATION OF WILD‐TYPE AND rad MUTANT Caenorhabditis elegans BY 8‐METHOXYPSORALEN AND NEAR ULTRAVIOLET RADIATION
Authors: Hartman Phil S. , Marshall Anne
Published: January 2008

Abstract— Survival of wild‐type and four radiation‐sensitive (rad) mutants of the nematode Caenorhubditis eleguns was determined after near‐UV irradiation in the presence of 8‐methoxypsoralen (8‐MOP). Three sets of inactivation profiles were generated for each strain by irradiating synchronous populations of either early embryos, late embryos or first‐stage larvae (L1s). Late embryos were consistently the most sensitive. Curiously, none of the four rad mutants were even moderately hypersensitive. Split‐dose experiments indicated that DNA‐DNA crosslinks were primarily responsible for lethality. Crosslink induction and repair were determined using two different assays. In both cases, little if any repair was observed in wild‐type. This lack of repair thus explains why the rad mutants were not hypersensitive to 8‐MOP photoinactivation. Since early embryos undergo extensive cell cycling, their resistance to 8‐MOP photoinactivation suggests that replication is highly refractory to both monoadducts and crosslinks, as has been demonstrated previously for UV radiation‐induced photoproducts (Hartman et al., 1991, Mutat. Rex, 255, pp. 163–173).
LOCALIZATION OF ULTRA WEAK PHOTON EMISSION IN PLANTS
Authors: Schauf B. , Repas L. M. , Kaufmann R.
Published: January 2008

Abstract— Ultraweak light emission and light piping of cucumber seedlings was shown using two‐dimensional photon imaging via an ultrahigh sensitive photon counting image acquisition system. A macroscopic localization of the photon generating region was achieved.
SINGLET OXYGEN YIELDS, OPTICAL PROPERTIES, AND PHOTOTOXICITY OF REDUCED DERIVATIVES OF THE PHOTOSENSITIZER CERCOSPORIN
Authors: Leisman Gary B. , Daub Margaret E.
Published: January 2008

Abstract— The perylenequinone cercosporin (CR) is a singlet oxygen generating photosensitizer produced by Cercospora spp which plays a critical role in parasitism of plants by these fungi. Several lines of evidence suggest that the defense mechanism of Cercospora spp towards this toxin is the generation of a cell surface reducing environment that leads to transient reduction of CR. In order to demonstrate that reduced CR is less toxic, several derivatives of CR were synthesized. Hexaacetyl‐dihydrocercos‐porin (HAC) was prepared by reductive acetylation of CR. Noranhydrocercosporin (NAC) resulted from dehydration of CR and tetramethyl‐noranhydrodihydrocercosporin (TMNAC) was a product of reductive methylation of NAC. The perylenequinones, CR and NAC, absorb more light than their respective reduced derivatives, but are much less fluorescent; the relative fluorescence intensities of HAC, TMNAC, and dithionite‐reduced CR were 80–160 times greater than that of CR and NAC. Also, CR and NAC were more efficient at generating singlet oxygen. As measured by time‐resolved IR luminescence, the singlet oxygen quantum yields relative to CR (adjusted to 1.00) were 0.16, 0.19 and 0.73, respectively, for HAC, TMNAC, and NAC. Toxicity was measured by assaying for inhibition of growth of CR‐sensitive fungi in constant light. The reduced derivatives were less toxic than their respective oxidized forms. None of the compounds showed significant growth inhibition in the dark with any of the fungi, or when assayed in the light with the CR‐resistant fungus Cercospora kikuchii. A lipid peroxidation assay with methyl linolenate also showed that HAC was less active than CR. Thus, reduction of CR leads to greater fluorescence intensities, lower production of singlet oxygen and lower phototoxicity. These data support the hypothesis of transient cercosporin reduction as a mechanism of defense against cercosporin toxicity.
PORPHYRIN PHOTOSENSITIZATION OF MULTI‐DRUG RESISTANT CELL TYPES
Authors: Kessel David , Erickson Cathy
Published: January 2008

Abstract— The P388 murine leukemia and P388/ADR, a subline expressing the multi‐drug resistance (MDR) phenotype, were examined with regard to the role of MDR as a determinant of responsiveness to photodynamic therapy in vitro. Mesoporphyrin was used as a model substrate. We found no differences in porphyrin accumulation nor transport alterations associated with exposure of P388/ADR cells to the verapamil analog DMDP. There was a significant correlation between photodamage to mitochondria vs loss of cell viability in both cell lines, and LD50 sensitizer levels were not significantly different in P388 vs P388/ADR. P388/ADR cells were partly resistant to porphyrin‐catalyzed photodamage to amino acid transport, but this result was not associated with differences in sensitizer localization, as indicated by fluorescence studies. Moreover, photodamage to membrane transport was not associated with loss of viability. These studies suggest that cells which express the MDR phenotype are unlikely to be cross‐resistant to photodynamic therapy.
PHOTODYNAMIC INACTIVATION OF AN ION CHANNEL: GRAMICIDIN A
Authors: Sträszle M. , Stark G.
Published: January 2008

Abstract— The ion channel formed by the peptide gramicidin A in planar lipid membranes is inactivated by visible light in the presence of the photosensitizer Rose Bengal. This is concluded from the strong decrease of the membrane conductance by more than two orders of magnitude.

Experiments performed at different oxygen concentrations, in the presence of the singlet oxygen quenchers β‐carotene or α‐tocopherol indicate, that presumably a type I process between the dye Rose Bengal and the tryptophan residues of the gramicidin channel with a subsequent oxidation of the tryptophans is responsible for the loss of the conductance properties of the channel.
FREE RADICALS AND EXCITED SPECIES IN THE METABOLISM OF INDOLE‐3‐ACETIC ACID AND ITS ETHYL ESTER BY HORSERADISH PEROXIDASE AND BY NEUTROPHILS
Authors: Escobar Jorge A. , Vásquez‐Vivar Jeannette , Cilento Giuseppe
Published: January 2008

Abstract— The peroxidative metabolization of indole‐3‐acetic acid, a biologically important process, has been followed by EPR spectroscopy with the aim of obtaining information on the mechanism of generation of electronically excited species.

The skatole‐3‐methylene radical detected during oxidation by horseradish peroxidase, does not appear to be involved in a major oxygen consuming process or in the generation of singlet oxygen. The chemiluminescence spectrum exhibits several maxima, which are also observed when the ethyl ester of indole‐3‐acetic acid is metabolized by horseradish peroxidase or by myeloperoxidase in neutrophils. When the ester is metabolically activated in either of these systems, the EPR spectrum indicates a tertiary carbon‐centered radical. This radical centered on the carbon in the 3‐position participates in a chemiexcitation/emissive route. Within the cell, this emissive process is responsible for a large part of the oxygen consumed. Some of the emitters originate in the cleavage of the 2,3 double bond.

The ester, which is capable of penetrating into the cells, also emits with other myeloperoxidase‐containing cells. This compound may have useful applications as an intracellular chemiluminescent probe for the presence of myeloperoxidase.
MODIFIED POLYVINYL ALCOHOL‐BENZOPORPHYRIN DERIVATIVE CONJUGATES AS PHOTOTOXIC AGENTS
Authors: Davis Noelle , Liu Daniel , Jain Ashok K. , Jiang Shi‐Yi , Jiang Frank , Richter Anna , Levy Julia G.
Published: January 2008

Abstract— Photosensitizing and biodistribution characteristics of a photosensitizer(benzoporphyrin derivative, monoacid ring A; BPD) conjugated to a macromolecule (modified polyvinyl alcohol; M‐PVA, molecular weight=10000) were tested in vitro and in vivo. Modified PVA was loaded with BPD at molar ratios 1:12, 1:25, 1:50, 1:75 and 1:100. Most of the work was carried out with a conjugate having a 1:25 molar ratio. In vitro photosensitization was tested using A549 (human lung carcinoma), A432 (human epidermoid carcinoma) and P815 (mastocytoma of DBA/2 mice) cell lines. Photosensitization of M1 (rhabdomyosarcoma of DBA/2 mice) tumors was tested in an in vivo/in vitro assay, in which tumor‐bearing mice were injected intravenously with free or conjugated 3H‐BPD and 3 h later light activation of tumor cells was carrie out in vitro. Biodistribution studies were carried out using M1 tumor‐bearing DBA/2 mice and 3H‐BPD either free or conjugated to M‐PVA. The result of there these studies showed that the conjugatin of BPD to M‐PVA resulted in the formation of a macromolecular photosensitizer that retained full photosensitizing avtivity of the photosensitizer molecules and at the same time gained new charcteristics, advantageous from photodynamic treatment, especially in vivo. In vitro M‐PVA‐BPD conjugates were at least as efficient in photosensitization of tumor cells as an equivalent number of free BPD molecules, both in the presence and in the absence of serum. Although the biodistribution was in general comparabel to free BPD, the conjugate(1:25) reached slightly higher leves in the blood, kidney, lung and spleen, and lower levels in the liver, brain, skin and muscle in comparison with free BPD. Although the level of M‐PVA‐BPD in tumor tissue was lower than tht of free BPD under comparable conditions, the conjugate was bound more tightly to the tumor cells and effected higher tumor cell kill when activated by light
IMPROVED HIGH‐PERFORMANCE LIQUID CHROMATOGRAPHIC ANALYSIS OF 8‐METHOXYPSORALEN MONOADDUCTS and CROSS‐LINKS IN POLYNUCLEOTIDE, DNA, and CELLULAR SYSTEMS: ANALYSIS OF SPLIT‐DOSE PROTOCOLS
Authors: Olack Gerard , Gattolin Paola , Gasparro Francis P.
Published: January 2008

Abstract— The distribution of 8‐methoxypsoralen‐thymidine photoadducts from polynucleotides, calf thymus DNA and mammalian cells treated with [3H]8‐methoxypsoralen under a variety of irradiation conditions was determined using high‐performance liquid chromatography and scintillation analysis. The split‐dose protocol, with samples treated with 8‐methoxypsoralen and low doses of long‐wavelength UV radiation to generate monoadducts, washed to remove unreacted 8‐methoxypsoralen, then irradiated further to convert the monoadducts to cross‐links, was examined. The photoadduct distribution in the first step is dependent upon the UVA dose and the wavelength of the radiation, but it is relatively independent of 8‐methoxypsoralen concentration. Low fluence and longer wavelengths generate mainly 4′,5′‐monoadducts, whereas higher fluences and shorter wavelengths yield more cross‐links. The second irradiation step converts the 4′,5′‐monoadducts to cross‐links as well as to 3,4‐monoadducts. The overall yield of cross‐links after the second irradiation step is not dependent upon the wavelength used in the first step. Cellular studies demonstrated that the split‐dose protocol is applicable to mammalian systems. These results may afFect the interpretation of mutagenesis studies based on the split‐dose protocol, because the second step can convert 4′,5′‐monoadducts to both 3,4‐monoadducts, the expected cross‐links. Therefore, interpretations that link increases in mutagenicity after the second step in a split‐dose study solely to cross‐link formation may need re‐examination.
A PHYTOCHROME PHOTOTRANSFORMATION STUDY USING TWO‐LASER/TWO‐COLOR FLASH PHOTOLYSIS: ANALYSIS OF THE DECAY MECHANISM OF I700*
Authors: Scurlock Rodger D. , Evans Christopher H. , Braslavsky Silvia E. , Schaffner Kurt
Published: January 2008

The mechanism of I700 decay, representing an early event in the phytochrome Pr→ Pfr phototransformation, was reanalyzed in the microsecond range by conventional laser flash photolysis as well as by two‐laser/two‐color flash photolysis. Three kinetic models that might describe the I700 decay mechanism following Pr excitation were considered: a parallel, a sequential, and an equilibrium model. These models were used to mathematically simulate both the one‐ and two‐laser flash experiments in an effort to select the model best describing the I700 decay. The sequential model could be excluded already on the basis of the one‐laser flash photolysis results alone. Discussion of the two‐laser/two‐color flash rcsults in the context of the equilibrium and the parallel models is presented.
STRUCTURAL AND FUNCTIONAL INTEGRITY OF THE PHOTOSYSTEM II REACTION CENTER ON SILVER ELECTRODES: FLUORESCENCE AND REDOX PROBES
Authors: Chumanov George , Picorel Rafael , Toon Stephen , Seibert Michael , Cotton Therese M.
Published: January 2008

Two simple and sensitive methods have been developed to assess the structural and functional integrity of isolated photosystem II reaction centers deposited on a roughened Ag electrode. Surface‐enhanced resonance Raman scattering (SERRS) spectra useful for ascertaining structural information can be obtained from biological materials with this technique. The first method presented is based on observing differences in the fluorescence emission properties of reaction centers; these depend on the activity of the material. The second is based on the observation of changes in Raman bands that are sensitive to the redox state of cytochrome b559 present in the reaction center complex. It is concluded that the conditions used here to obtain SERRS spectra do not affect the structural or functional integrity of the isolated photosystem II reaction center complex. In principle these approaches also could be used with other chromoproteins.
A GARLIC EXTRACT PROTECTS FROM ULTRAVIOLET B (280–320 nm) RADIATION‐INDUCED SUPPRESSION OF CONTACT HYPERSENSITIVITY
Authors: Reeve Vivienne E. , Bosnic Meira , Rozinova Emilia , Boehm‐Wilcox Christa
Published: January 2008

Abstract Lyophilized aged garlic extract has been incorporated at concentrations of 0.1%, 1% and 4% by weight into semipurified powdered diets and fed to hairless mice. Under moderate UVB exposure conditions resulting in 58% suppression of the systemic contact hypersensitivity response in control‐fed mice, a dose‐responsive protection was observed in the garlic‐fed mice; contact hypersensitivity in the UVB‐exposed mice fed 4% garlic extract was suppressed by only 19%. If the UVB exposure was replaced by topical application of one of a series of lotions containing increasing concentrations of cis‐urocanic acid, a dose‐responsive suppression of contact hypersensitivity was demonstrated in control‐fed mice (urocanic acid at 25, 50, 100 and 200 μg per mouse resulting in 22–46% suppression). Mice fed a diet containing 1% aged garlic extract were partially protected from cis‐urocanic acid‐induced suppression of contact hypersensitivity, with greater protection from the lower concentrations of urocanic acid. Mice fed a diet containing 4% aged garlic extract were protected from all concentrations of urocanic acid. The results indicate that aged garlic extract contains ingredient(s) that protect from UVB‐induced suppression of contact hypersensitivity and suggest that the mechanism of protection is by antagonism of the cis‐urocanic acid mediation of this form of immunosuppression.
THE UPTAKE OF PORPHYRIN AND ZINC‐METALLOPORPHYRIN BY THE PRIMATE PROSTATE
Authors: Pantelides M. L. , Moore J. V. , Forbes E. , Truscott T. G. , Blacklock N. J.
Published: January 2008

Abstract— The relative distribution of sensitizer drugs in the prostate and its contiguous organs is of importance in the treatment of localized prostatic cancer with photodynamic therapy. Using the primate model, whose prostate is both morphologically and physiologically homologous with its human counterpart, the distribution of hematoporphyrin derivative (HpD) amongst organs of urological interest was determined. Hematoporphyrin derivative levels were comparatively low in both caudal and cranial prostatic lobes (0.93‐1.77 μg/g) and were similar to those in rectum, urethra and the skin. The reticuloendothelial organs, liver, spleen and also the kidney accumulated the highest quantities of porphyrin (4.76‐9.8 μg/g, liver > spleen > kidney). Despite a high avidity of prostatic tissue for zinc, a zinc‐metalloporphyrin (Zn‐HpD) did not concentrate selectively in the prostate. The results are of clinical value in view of the homology between the primate and the human.
MECHANISMS OF QUENCHING OF THE FLUORESCENCE OF A BENZO[a]PYRENE TETRAOL METABOLITE MODEL COMPOUND BY 2′‐DEOXYNUCLEOSIDES
Authors: Geacintov Nicholas E. , Zhao Rushen , Kuzmin Vladimir A. , Kim Seog K. , Pecora Lorenzo J.
Published: January 2008

Abstract— The hydrophobic interactions of bulky polycyclic aromatic hydrocarbons with nucleic acid bases and the formation of noncovalent complexes with DNA are important in the expressions of the mutagenic and carcinogenic potentials of this class of compounds. The fluorescence of the polycyclic aromatic residues can be employed as a probe of these interactions. In this work, the interactions of the (+)‐trans stereoisomer of the tetraol 7,8,9,10‐tetrahydroxytetrahydrobenzo[a]pyrene (BPT), a hydrolysis product of a highly mutagenic and carcinogenic diol epoxide derivative of benzo[a]pyrene, were studied with 2′‐deoxynucleosides in aqueous solution by fluorescence and UV spectroscopic techniques. Ground‐state complexes between BPT and the purine derivatives 2′‐deoxyguanosine (dG), 2′‐deoxyadenosine (dA), and 2′‐deoxyinosine (dI) are formed with association constants in the range of ∼40–130 M−1 Complex formation with the pyrimidine derivatives 2′‐deoxythymidine (dT), 2′‐deoxycytidine (dC), and 2′‐deoxyuridine (dU) is significantly weaker. Whereas dG is a strong quencher of the fluorescence of BPT by both static and dynamic mechanisms (dynamic quenching rate constant kdyn= [2.5 ± 0.41 × 109M1 s 1, which is close to the estimated diffusion‐controlled value of ∼ 5 × 109M− 1 s−1), both dA and dI are weak quenchers and form fluorescenceemitting complexes with BPT. The pyrimidine derivatives dC, dU, and dT are efficient dynamic fluorescence quenchers (Kdyn∼ [1.5–3.0] × 109M−1 s−1), with a small static quenching component due to complex formation evident only in the case of dT. None of the four nucleosidcs dG, dA, dC and dT are dynamic quenchers of BPT in the triplet excited state; the observed lower yields of triplets are attributed to the quenching of single excited states of BPT by 2′‐deoxynucleosides without passing through the triplet manifold of BPT. Possible fluorescence quenching mechanisms involving photoinduced electron transfer are discussed. The strong quenching of the fluorescence of BPT by dG, dC and dT accounts for the low fluorescence yields of BPT‐native DNA and of pyrene‐DNA complexes.
ISOLATION AND CHARACTERIZATION OF THE PRESUMED PHOTORECEPTOR PROTEIN OF Blepharisma japonicum
Authors: Gioffré Domenico , Ghetti Francesco , Lenci Francesco , Paradiso Cristina , Dai Renke , Song Pill‐Soon
Published: January 2008

Abstract— Photosensory responses in the ciliated protozoan Blepharisma japonicum are mediated by a hypericin‐like chromophore, blepharismin, localized in granules distributed under the cell membrane. A blepharismin‐binding protein, with an apparcnt molecular weight ranging between 35 and 38 kDa, has been isolated by means of column separations and preparative isoelectric focusing and characterized by means of gel electrophoresis, analytic isoelectric focusing as well as absorption and fluorescence spectroscopy.
PHOTODEGRADATION OF SULFAMETHOXAZOLE: A CHEMICAL SYSTEM CAPABLE OF MONITORING SEASONAL CHANGES IN UVB INTENSITY
Authors: Moore Douglas E. , Zhou Wei
Published: January 2008

Abstract— Sulfamethoxazole (SMX) in its nonionized form in aqueous solution has ultraviolet (UV) absorption that is maximal at 268 nm but extends through the ultraviolet‐B (UVB) region. It was found to be extremely susceptible to photodegradation when exposed to artificial UV radiation through a Pyrex filter or to unfiltered natural sunlight. The SMX anion was more stable. The quantum yields of the photodegradation of both forms were determined by use of monochromatic light and ferrioxalate chemical actinometry, the values of 0.47 (pH 3.0) and 0.084 (pH 9.0) at the maximum absorption wavelengths (268 and 257 nm, respectively) being obtained. Using literature data on sunlight intensity, the photochemical shelf‐life of SMX solutions exposed to direct sunlight was calculated for Sydney (latitude 33.5°S) as a function of season of the year and verified experimentally. A fixed correlation was established between the rate constant for SMX degradation and UVB intensity measured by a radiometer, suggesting the capacity of this chemical system to monitor changes in the UVB region of sunlight.
A THEORETICAL STUDY OF THE CYTOSINE EXCIMER STATE: THE ROLE OF GEOMETRY OPTIMIZATION
Authors: Danilov Victor I. , Slyusarchuk Oleg N. , Alderfer James L. , Stewart James J. P. , Callis Patrik R.
Published: January 2008

Abstract A study of the lowest excited dimer (excimer) singlet state of the DNA base cytosine was performed with fully optimized geometry (near the cis‐syn form) using a slightly modified version of MOPAC6 (AM1 hamiltonian) and 112 excited configurations involving an active space consisting of the four highest occupied and the two lowest empty MO of the dimer. A binding energy of 3 kcal/mol for the excimer state is demonstrated, and the excimer fluorescence is predicted to be shifted 150 nm to longer wavelengths relative to that of the monomer fluorescence. The excimer geometry has the planes nonparallel (40–45° interplanar angle) and distorted, with the C5‐C6 bonds showing quite close contact (2.4 Å). Excitation is found to be more localized in the region of the C5‐C6 bond than expected from the monomer wavefunction. No stable excimer was found if the planes were constrained to be planar, nor if the triplet state was selected. The results suggest that the excimer geometry found in this study may be a precursor to the cis‐syn cyclobutane photodimer.
THE UV ACTION SPECTRA FOR THE CLONE‐FORMING ABILITY OF CULTURED HUMAN MELANOCYTES AND KERATINOCYTES
Authors: De Leeuw Sandra M. , Janssen Sacha , Simons Johannes W. I. M. , Lohman Paul H. M. , Vermeer Bert‐Jan , Schothorst Albert A.
Published: January 2008

Abstract Melanocytes (skin type 2) and keratinocytes were irradiated with UV light of 254, 297, 302, 312 and 365 nm and the survival was measured. Clone‐forming ability was chosen as the parameter for cell survival. Melanocytes were found to be less sensitive to UV light than keratinocytes (a difference of a factor 1.22‐1.92 for the UV‐C and UV‐R wavelengths (254, 297, 301 and 312 nm) and a factor 6.71 for the UV‐A wavelength (365 nm). Because melanin does not appear to protect against the induction of pyrimidine dimers the difference between melanocytes and keratinocytes in the UV‐C and UV‐B region could not be explained by the presence of melanin in the melanocytes. The relatively small difference can be explained by the longer cell cycle of melanocytes, which provides more time for the melanocytes to repair UV damage. In the UV‐A region the difference between melanocytes and keratinocytes was much larger, suggesting that besides the longer cell cycle some additional factors must be involved in protection against UV‐A light.
Ca2+ INFLUX INDUCED BY PHOTODYNAMIC ACTION IN HUMAN CEREBRAL GLIOMA (U‐87 MG) CELLS: POSSIBLE INVOLVEMENT OF A CALCIUM CHANNEL
Authors: Joshi Preeti G. , Joshi Kunju , Mishra Sudha , Joshi Nanda B.
Published: January 2008

Abstract The plasma membrane has been implicated as a critical target of photodynamic action on cells. We have observed that the photosensitization of human cerebral glioma (U‐87 MG) cells by hematoporphyrin derivative (HpD) causes a large increase in intracellular calcium [Ca2+]. This increase in [Ca2+]i was solely due to the influx of extracellular Ca2+ through the plasma membrane and showed a dependence on HpD concentration, light dose and concentration of calcium in the extracellular medium. The magnitude of the Ca2+ influx decreased with increasing postirradiation time, which suggests that the cell membrane partially recovers from the photodynamic injury. The photoinduced Ca2+ influx was inhibited by the Ca2+ channel blocker diltiazem and the reducing agent dithioerythritol. These findings are discussed in terms of possible activation of a Ca2+ channel as a result of photosensitization.
VISIBLE CHEMILUMINESCENCE ASSOCIATED WITH THE REACTION BETWEEN METHEMOGLOBIN OR OXYHEMOGLOBIN WITH HYDROGEN PEROXIDE
Authors: Lissi Eduardo A. , Escobar Jorge , Pascual Carlos , Castillo Maria del , Schmitt Tais H. , Mascio Paolo Di
Published: January 2008

Abstract Visible chemiluminescence is emitted in the irreversible deactivation of hemoglobin or methemoglobin with excess H2O2. The emission takes place in two phases. The most intense one lasts a few seconds and is followed by a second phase of lower intensity that remains for longer periods. This second phase presents chaotic or sustained oscillations. Free radicals are implicated in the luminescent process since the emission can be reduced by free radical scavengers such as 6‐hydroxy‐2,5,7,8,‐tetramethylchroman‐2‐carboxylic acid (Trolox) or ascorbic acid. These additives lead to a delay in reaching the maximum intensity, which can be related to their consumption, implying substantial recycling of the hemoprotein. Chemiluminescence is also observed in the oxidation of hemin by H2O2, suggesting a role for the heme group in the processes leading to the excited state production. The lower intensity observed in the presence of hemin can be related to the contribution of the globin chains.
PHOTOCHEMICAL STABILITY OF BIOLOGICALLY ACTIVE COMPOUNDS. IX. CHARACTERIZATION OF THE SPECTROSCOPIC PROPERTIES OF THE 4‐AMINOQUINOLINES, CHLOROQUINE AND HYDROXYCHLOROQUINE, AND OF SELECTED METABOLITES BY ABSORPTION, FLUORESCENCE AND PHOSPHORESCENCE MEASUREMENTS
Authors: Nord Karin , Karlsen Jan , Tosnnesen Hanne Worth
Published: January 2008

Abstract The spectroscopic properties of the antimalarials chloroquine, hydroxychloroquineand selected metabolites were investigated by absorption, fluorescence and phosphorescence measurements. The antimalarials exhibit both fluorescence and phosphorescence. Fluorescence dominates for the deprotonated forms of the 4‐aminoquinolines, while phosphorescence dominates when the compounds are protonated. The phosphorescence lifetimes of the 4‐aminoquinolines were measured. Both the protonated and the deprotonated forms have long phosphorescence lifetimes indicating a long‐lived triplet state.
8‐METHOXYPSORALEN INCREASES DAYTIME PLASMA MELATONIN LEVELS IN HUMANS THROUGH INHIBITION OF METABOLISM
Authors: Garde E. , Mici S. , Knudsen K. , Angelo H. R. , Wulf H. C.
Published: January 2008

Abstract It is well established that in healthy humans oral intake of 5‐or 8‐methoxypsoralen (5‐and 8‐MOP) is followed by a significant increase in plasma melatonin concentrations. The effect of psoralen on rat melatonin has been studied in vitro and in vivo and a stimulation of release or secretion from the pineal gland has been suggested. In this study we examined the time‐related changes in plasma concentrations of 8‐MOP, melatonin and 6‐sulfatoxymelatonin in 15 patients admitted for routine psoralen plus UVA therapy. On the first day of treatment blood samples were collected before, and30, 60, 66 and 90 rnin after intake of 8‐MOP (0.6 mg/kg). Although the rate of 8‐MOP absorption vaned greatly, a significant increase (P= 0.0002) in melatonin levels was found 60 min after 8‐MOP intake. During UVA exposure a strongly correlated decrease in mean melatonin and mean 8‐MOP concentrations was found, indicating an effect of UVA radiation, either direct or 8‐MOP mediated, on circulating melatonin levels. Plasma 6‐sulfatoxymelatonin concentrations decreased significantly between all time points, suggesting inhibition of melatonin metabolism.
PHOTOSENSITIZATION OF SUPERCOILED DNA DAMAGE BY 5,6‐DIHYDROXYINDOLE‐2‐CARBOXYLIC ACID, A PRECURSOR OF EUMELANIN
Authors: Routaboul C. , Serpentini C.‐L. , Msika P. , Cesarini J.‐P. , Paillous N.
Published: January 2008

Abstract—

The photosensitizing or photoprotecting action of 5,6‐dihydroxyindole‐2‐carboxylic acid (DICA), an intermediate in the biosynthesis of eumelanins, was investigated. Under irradiation at 313 nm, aqueous buffered solutions of DICA (22.5 μW) photosensitized the cleavage of phage φX174 DNA. The number of single strand breaks (SSB) depended on the dose of irradiation and was more important in the absence than in the presence of oxygen. In the presence of oxygen, the quantum yield of SSB was around 6′10 7 (ΦSSB) The influence of specific scavengers, such as mannitol, sodium azide or superoxide dismutase, indicated that hydroxyl radicals, superoxide anions and perhaps singlet oxygen were involved in these processes. The increase in SSB in D2O was also indicative of the participation of singlet oxygen. Comparative experiments performed with indole‐2‐carboxylic acid (IC), a dehydrox‐ylated analog of DICA, showed that this compound, although lacking a phenol group, also photosensitized DNA cleavage via a mechanism involving hydroxyl radicals. Various sources of these radicals were envisioned. Furthermore, under our conditions, DICA was not found to photoinduce the formation of DNA dimers: No increase in SSB was observed in DNA irradiated in the presence of DICA, after treatment by phage T4 endonuclease V (an enzyme that selectively cuts DNA at dimer sites), whereas, in contrast, a significant increase in SSB was detected after treatment of DNA irradiated alone. So it appears that DICA may both photosensitize DNA cleavage and reduce UV‐induced DNA dimer formation.
INTERCONVERSION OF BACTERIOCHLOROPHYLL c AGGREGATES IN SOLID FILMS UPON ORGANIC VAPOR TREATMENT
Authors: Uehara Kaku , Tachibana Taro , Tsunooka Masahiro , Ozaki Yukihiro
Published: January 2008

Abstract—

Bacteriochlorophyll c (BChl c) solid films were prepared from a carbon tetrachloride solution on CaF2 plates as artificial aggregates. Effects of organic vapor such as acetone and tetrahydrofuran (THF) on the BChl c films were studied by absorption and Fourier‐transform infrared spectroscopy. Two major homologs (R[E,E]BChl cF and R[P,E]BChl cF) and one minor homolog (S[I,E]BChl c) isolated from the green photosynthetic bacterium Chlorobium limicola strain 6230 were examined for the experiments. The BChl c polymeric aggregates absorbing at739–753 nm similar to those in the chlorosome were induced for all homologs upon the treatment of BChl c solid film with acetone vapor. The 131‐keto C=O stretching band in the R[E,E]BChl cF solid film showed a downward shift from 1651 cm−1to 1643 cm−1 with a concomitant shift of the 31‐OH stretching bands from 3337 and 3238 cm−1 to 3163 cm−1. It was suggested that the lower aggregates brought about by Mg…O=C(131) and (31)O…O=C(131) bonds were transformed into the higher aggregates strongly hydrogen‐bonded in a Mg…(31)O‐H…O=C(13l) interaction. They were transformed to a monomer‐like form absorbing at 667 nm upon exposure to THF vapor and were reversibly converted to the higher aggregates upon removal of THF molecules in vacuo.
REDISTRIBUTION AND VIRUS INACTIVATION EFFICACY OF A SILICON PHTHALOCYANINE IN RED BLOOD CELL CONCENTRATES AS A FUNCTION OF DELIVERY VEHICLE
Authors: Ben‐Hur E. , Zuk M. M. , Chin S. , Banerjee D. , Kenney M. E. , Horowitz B.
Published: January 2008

Abstract—

The silicon phthalocyanine, HOSiPcOSi(CH3)2(CH2)3N(CH3)2 (Pc 4), is a new photosensi‐tizer that can inactivate lipid‐enveloped viruses in red blood cell concentrates (RBCC) upon exposure to red light. Because Pc 4 is insoluble in water, it was delivered either as an emulsion in saline and cremophor EL (CRM) or as a solution in dimethyl sulfoxide (DMSO). In RBCC, Pc 4 added in either vehicle distributed between the plasma and red blood cells (RBC) in a ratio of 4:6, similar to the ratio of these components in RBCC 3:7 (i.e. a hematocrit of 70%). Light exposure did not affect this distribution and caused only marginal degradation of Pc 4 at a light dose that inactivates >5 log,0 vesicular stomatitis virus (VSV). Among human plasma proteins, Pc 4 bound mainly (about 70%) to lipoproteins and to a lesser extent to albumin and lower molecular weight proteins when delivered in DMSO. When delivered in CRM, distribution between lipoproteins and albumin became more even. Among the lipoproteins Pc 4 bound almost exclusively to very low‐density lipoproteins (VLDL) when delivered in DMSO and to both VLDL and low‐density lipoproteins when added in CRM. The rate of VSV inacti‐vation was independent of the delivery vehicle but there was less RBC damage, as measured by hemolysis during storage, when Pc 4 was added in CRM. These results indicate that using CRM as emulsifier can enhance the specificity of Pc 4‐induced photochemical decontamination of RBCC for transfusion.
A SCALAR IRRADIANCE FIBER‐OPTIC MICROPROBE FOR THE MEASUREMENT OF ULTRAVIOLET RADIATION AT HIGH SPATIAL RESOLUTION
Authors: Garcia‐Pichel Ferran
Published: January 2008

Abstract— The construction of a new type of microprobe for the measurement of scalar irradiance (integral dose rate) in the UV down to wavelengths of 250 nm is described. The microprobes were made from tapered standard optical fibers and a tip‐diffuser of magnesia/silica vitroceramic. The sensing tips were ca 100 μm in diameter and had maximal deviations in the angular response of ± 15%. I present measurements of scalar irradiance at high spatial resolution within dry beach sand and suspensions of microorganisms. These two media are environments in which microorganisms are exposed to UV, either under natural (sand) or laboratory conditions (suspensions). In both cases, the space distribution of UV scalar irradiance, and thus the distribution of integral dose rates, departed significantly from that predicted by absorptive effects alone. The results underscore the importance of small‐scale, in situ measurements of scalar irradiance for UV dosimetry in such scattering media.
REACTIVITY OF SINGLET OXYGEN TOWARD LARGE PEPTIDES
Authors: Michaeli Albert , Feitelson Jehuda
Published: January 2008

Abstract— The reactions of singlet oxygen, 1O2, with amino acids and their derivatives have been studied previously. It was found that only five amino acid residues interact readily with 1O2. Here we describe its reactions with the large peptides melittin, neuropeptide Y (NPY) and insulin in their native and in their denatured forms. The singlet oxygen quenching by a polypeptide was compared with that of a solution at the same concentration as those of its constituent amino acids, which are known to react efficiently with 1O2. It was found that the quenching rate by such a mixture exceeded that of the polypeptides in their native form. The ratio of the rate constants for NPY to that of the corresponding amino acid mixture in solution was 0.75. For melittin in its monomeric form it was 0.83 and for a tetramer of melittin (at high ionic strength) it was 0.70. For native insulin the ratio of the rate constants was 0.55. For oxidized insulin with its ‐S‐S‐ bridges opened the figure became 0.80. However, the quenching by all the polypeptides in their fully denatured form (in the presence of 6 M urea) equalled that of the corresponding amino acid mixtures. Although polypeptides are generally supposed not to possess a stable secondary structure in solution the effects are explained by shielding of some of the reactive amino acid residues in the chain by temporary folding or incipient secondary structures of the native polypeptide.

It is shown that the kinetics for a homogeneous solution of quenchers applies also to measurements in a polypeptide solution where the quenchers are localized along the polypeptide backbone and thus form clusters in solution.
FUROCOUMARIN‐PHOTOSENSITIZEDHYDROXYLATION OF GUANOSINE IN RNA AND DNA
Authors: Wamer Wayne G. , Timmer William C. , Wei Rong Rong , Miller Sharon A. , Kornhauser Andrua
Published: January 2008

Abstract— Guanosine hydroxylation was used as a marker for assessing photooxidation of DNA and RNA sensitized by monofunctional and bifunctional furocoumarins. DNA or RNA, treated with sensitizer and UVA light, was enzymatically hydrolyzed, dephosphorylated and then analyzed by reversed‐phase HPLC with electrochemical detection. Hydroxylated guanosine, i.e. 8‐hydroxy‐2′‐deoxyguanosine (8‐OHdG) or 8‐hydroxyguanosine (8‐OHG), was quantitated. 3‐Carbethoxypsoralen (3‐CP) was found to be an efficient photosensitizer for oxidation of guanosine in DNA, resulting in conversion of up to 0.4% of guanosine residues to 8‐OHdG. In contrast, dramatically lower levels of guanosine hydroxylation were observed in 3‐CP‐photosensitized RNA. Psoralen was found to be a more efficient photosensitizer than angelicin in both DNA and RNA. Additional studies of oxidation of 3‐CP‐photosensitized DNA indicated that double‐stranded DNA is 10 times more susceptible to photooxidation than single‐stranded DNA, implicating 3‐CP binding to DNA as an important mechanistic step in photooxidation of guanosine. The effects of D2O and degassing with argon on photooxidation of guanosine in DNA sensitized by 3‐CP were inconsistent with a mechanism involving 1O2. In addition, chelation of adventitious metal ions present in preparations of DNA photosensitized by 3‐CP had no effect on hydroxylation of guanosine.
A PORTABLE INSTRUMENT FOR MEASURING GROUND REFLECTANCE IN THE ULTRAVIOLET
Authors: Diffey B. L. , Green A. T. , Loftus M. J. , Johnson G. J. , Lee P. S.
Published: January 2008

Abstract— A lightweight, battery‐powered instrument specifically designed for measuring ground reflectance in the UV is described. The instrument has been used to measure the UV reflectance over different terrains in Saudi Arabia, Canada and England, and data are presented for a number of surfaces including tarmac, grass, wood, concrete and sand. These values agree closely with those obtained by diffuse spectral reflectance measurements.
Preservation of Immunoreactivity in the Photolabeling of the B72.3 Human Antibody
Authors: Pandurangl Raghoottama S. , Karra Srinivasa R. , Kuntz Robert R. , Volkert Wynn A.
Published: January 2008

A versatile photochemical method of labeling human antibodies is described. Labeling is achieved by photolyzing 4‐azido‐2, 3, 5, 6‐tetrafluoro‐14C‐methylbenzoate and the B72.3 human antibody in a buffer at physiological pH. The photochemically produced nitrene presumably inserts into bonds in the hydrophobic part of the antibody resulting in >75% attachment of the photoprobe. An immunoassay of B72.3 with mucin (B72.3 antigen) reveals >97% retention of immunoreactivity and suggests that photochemical labeling is a viable alternative for the conjugation of biomolecules.
Plant Canopy Shape and the Influences on UV Exposures to the Canopy
Authors: Parisi A. V. , Wong J. C. F.
Published: January 2008

The solar spectra at selected sites over hemispherical, conical and pinnacle plant canopy models has been evaluated with a dosimetric technique. The irradiance at the sites varies by up to a factor of 0.31 compared to the irradiance on a horizontal plane. The biologically effective (UVBE) exposures evaluated with the dosimetric technique at sites over the plant canopy are up to 19% of that on a horizontal plane. Compared to a spectroradiometer, the technique provides a more practicable method of measuring the UVBE exposures at multiple sites over a plant canopy. Usage of a dosimeter at one site to provide the exposures at that site for different sun angles introduces an error of more than 50%. Knowledge of the spectra allowed the UV and UVBE exposures to be calculated at each site along with the exposures to the entire canopies. These were dependent on the sun angle and the canopy shape. For plant damage, the UVBE was a maximum of about 1.4 mJ cm 2 min−1. Compared to the hemispherical canopy, the UVBE exposure for generalized plant damage was 45% less for the pinnacle canopy and 23% less for the conical canopy. The canopy exposures could not be determined from measurements of the ambient exposure.
Kinetic Transport Analysis of Daunorubicin by LoVo and LoVo/DX Cells
Authors: Andreoni A. , Colasanti A. , Colasanti P. , Kisslinger A. , Mastrocinque M. , Ricclo P. , Roberti G.
Published: January 2008

We describe a fluorometric technique for the measurement of transport parameters of fluorescent drugs through cellular membranes. Unlike other procedures, this method gives an accurate measure of drug accumulated in the cells and measures the fraction of free and bound drug in the cell. The kinetic parameters of transport through cellular membranes are determined using a simple three‐compartment model combined with fluorescence measurements performed on the extracellular medium and on Triton‐permeabilized cells during daunorubicin incorporation. With this technique we found that LoVo cells have a greater daunorubicin uptake, a similar input rate constant and a lower output rate constant than the drug‐resistant LoVo/DX cells.
Book Review
Authors: Johnson Richard P.
Published: January 2008

Excited States and Photochemistry of Organic Molecules. Martin Klessinger and Josef Michl
A Method for Evaluation of UV and Biologically Effective Exposures to Plants
Authors: Parisi A. V. , Wong J. C. F. , Galea V.
Published: January 2008

This paper presents a method for evaluating the UV and biologically effective exposures to a plant canopy during the irradiation of soybean with supplemental levels of UV radiation in a greenhouse study. The method employs four materials as dosimeters that allow evaluation of the UV spectra. The exposures evaluated at three growth stages were less by factors of 0.44, 0.49 and 0.56 compared to the ambient exposures. At the end of the irradiation period, the ambient biologically effective exposure for generalized plant response was higher by 180% compared to that calculated over the canopy. This is the magnitude of the error in UV studies that provide the ambient exposure as a measure of the UV incident on the plant. Additionally, the difference between the ambient and canopy exposures varied during the growth stages. These results indicate that the dosimetric technique applied to evaluating the UV exposures over a plant canopy is a more accurate representation of the UV exposure incidence on a plant than any obtained by measuring the ambient exposures only.