bluuebunny/crossref_metadata_2025 huggingface dataset:
CUTANEOUS PHOTOSENSITIZING AND IMMUNOSUPPRESSIVE EFFECTS OF A SERIES OF TUMOR LOCALIZING PORPHYRINS
Authors: MUSSER DAVID A. , FIEL ROBERT J.
Published: January 2008

Abstract— A series of tumor localizing porphyrins was evaluated with respect to their ability to elicit cutaneous photosensitivity and systemic immunosuppression, two of the most common side effects associated with photodynamic therapy. Using the murine ear swelling response as an indicator, it was found that all the non‐metalloporphyrins caused cutaneous photosensitization. Immunosuppressive effects were noted using hematoporphyrin derivative (HPD) and meso‐tetra(4‐sulfonatophenyl)porphine if sensitization occurred immediately after photoirradiation, but none were evident using Photofrin II (PII) or meso‐tetra(4‐carboxyphenyl)porphine (TCPP). Subsequent studies indicated that PII and TCPP manifested a delayed type immunosuppression similar to that found following UVB photoirradiation. Manganese (III) meso‐tetra(4‐sulfonatophenyl)porphine, a prototype magnetic resonance imaging contrast agent, was also evaluated because of its reported demetallation in vivo. It was found to cause neither cutaneous photosensitivity nor immunosuppression.
THE CHEMILUMINESCENCE OF AMIDES AND MONOACYL HYDRAZIDES BASED ON FIREFLY DEHYDROLUCIFERIN
Authors: WHITE EMIL H. , LI MIN , ROSWELL DAVID F.
Published: January 2008

Abstract— Monoacyl hydrazides based on 5‐methyldehydroluciferin and simpler analogs have been synthesized; they proved to be chemiluminescent on treatment with a strong base in DMSO in the presence of oxygen. The light emitters in these cases appear to be the corresponding carboxylate ions; a pathway involving an oxidative decarboxylation was eliminated as a possibility by consideration of the fluorescence wavelengths of the corresponding oxyluciferins. A reaction mechanism for the luminescence involving the possible intermediacy of an azadioxetane is proposed. The corresponding amides were also synthesized; they proved to be equally chemiluminescent to the hydrazides in the dehydroluciferin series.
RING OPENING PHOTOREACTIONS OF 5‐BROMOURACIL AND 5‐BROMO‐2′‐DEOXYURIDINE WITH SELECTED ALKYLAMINES
Authors: SHETLAR MARTIN D. , ROSE ROBERT B. , HOM KELLIE , SHAW ANTHONY A.
Published: January 2008

Abstract— Several studies in the literature indicate that histones (lysine rich proteins found associated with DNA in eukaryotic chromatin), as well as poly‐L‐lysine, can be photocross‐linked by ultraviolet (UV) light to DNA in which 5‐bromo‐2′‐deoxyuridine has been substituted for thymidne. To gain some insight into the possible nature of this cross‐linking, we have studied the photoreactions occurring in deoxygenated aqueous solutions containing 5‐bromouracil (I) (BrUra) or 5‐bromo‐2′‐deoxyuridine (III) (BrdUrd) and ethylamine, a lysine side chain analog. In the case of I this reaction produced the ring opened compound N‐(N′‐ethylcarbamoyl)‐3‐amino‐2‐bromoacrylamide (Ia). A small amount of N‐(N′‐ethylcarbamoyl)‐3‐ethylamino‐2‐bromoacrylamide (Ic) was also isolated. It was found that purified Ia, standing in the presence of ethylamine, was gradually converted to Ic in a dark reaction. The βandαanomers of N‐(N′‐ethylcarbamoyl)‐3‐(2′ deoxyribofuranos‐1′‐yl)amino‐2‐bromoacrylamide (IIIa and IIIb respectively) were isolated as products in the photoreaction of III with ethylamine; the α anomer was produced in a dark reaction from the β anomer. The identity of these anomers was established by comparison of their proton NMR spectra with those of the four corresponding α and β furanosyl and pyranosyl isomeric nucleosides of thymine, which are presented in the Appendix. A study was also made of the reaction of I with methylamine; a ring opened product analogous to In, viz. N‐(N′‐methylcarbamoyl)‐3‐amino‐2‐bromoacrylamide(IIa) was formed. A similar study with 5‐bromo‐1‐methyluracil produced N‐(N′‐methylcarbamoyl)‐3‐methylamino‐2‐bromoacrylamide (IIc) as a product. Likewise, the reaction of 5‐chlorouracil with ethylamine was studied and N‐(N′‐ ethylcarbamoyl)‐3‐amino‐2‐chloroacrylamide (Ie), which is analogous in structure to Ia, was found to be produced. Structural identifications were made through use of UV spectroscopy, high resolution 1H‐NMR spectroscopy, mass spectrometry and, in the case of Ia and IIa, 13C‐NMR spectroscopy. In the BrUra and BrdUrd reaction systems, described above, dehalogenation reactions accounted for a major portion of the products. The yields of ring opened products, determined at pH 10, ranged from a high of 10.3% in the BrUra‐ethylamine system to a low of 1.7% in the MeBrUra‐methylamine system.

The pH profile of the relative quantum yields for production of total opened ring product (IIIa+IIIb) in the photoreaction of III with ethylamine indicates that this quantity increases rapidly over the pH range between 7.5 and 9.5 and then decreases above 10.5.

An additional reaction, a photoinduced halogen exchange process, was found to occur when Ia was irradiated in sodium chloride solution; this reaction converted Ia to Ie.
STEADY HYPSOCHROMIC SHIFT OF PEAK RESPONSIVITY TO ATTRACTANT LIGHT FROM 590 nm TO 560 nm INHalobacterium halobium*
Authors: WAGNER GOTTFRIED , HESSE VOLKER , TRAULICH BERNHARD
Published: January 2008

Abstract—Peak responsivity of photoattraction inHalobacterium halobiumcells shows steady hypsochromic shift from 590 nm wavelength under low irradiance conditions to 560 nm under high irradiance conditions. Inversion of the photoattractant response, as dependent on bluevsred background light, is compatible with the known properties of photochromic sensory rhodopsin‐I (SR‐I) with ground state maximum absorption at 587 nm. Relaxation of the photoattractant response inH. halobium, as a function of wavelength and irradiance, gives a hint at an antagonistic pigment or intermediate state, different from ground state SR‐I, with peak sensitivity at 620 nm or even above. The less sensitive photoattractant response at 560 nm persists without photorelaxation and represents the peak responsivity under high irradiance conditions.
LIGHT‐DEPENDENT GENERATION OF SUPEROXIDE FROM HUMAN ERYTHROCYTES
Authors: Bynoe Leon A. , Gottsch John D. , Pou Sovitj , Rosen Gerald M.
Published: January 2008

Abstract—

Using the cytochrome c reduction method, we investigated light‐dependent erythrocytic superoxide production. After 4 h light and dark exposure of erythrocytes from eight healthy human subjects, an average of 18.6% more superoxide was generated by erythrocytes exposed to light. Pretreatment of erythrocytes with the superoxide dismutase inhibitorN,N‐diethyldithiocarbamate increased detection of superoxide while pretreatment with the anion channel blocker 4‐a‐cetamido‐4′‐isothiocyano‐2,2′‐disulfonic acid stilbene decreased detection. These findings indicate that substantially more spontaneously generated superoxide is produced and escapes from normal erythrocytes at ambient oxygen tensions on exposure to light. This excess generation and escape of superoxide from erythrocytes exposed to light may result in tissue photosensitization, especially in the retina of the eye, where high oxygen tension, blood and chronic light exposure occur simultaneously.
BASE RELEASE FROM DNA AND POLYNUCLEOTIDES UPON 193 nm LASER EXCITATION
Authors: Gurzadyan Gagik G. , Gorner Helmut
Published: January 2008

Abstract—

Release of bases from calf thymus DNA and three polynucleotides, induced by 20 ns excitation at 193 nm in aqueous solution at pH 7, was detected by HPLC. The quantum yields of formation of free bases (ΦB) from double‐stranded DNA (0.4 mM) are independent of intensity, indicating a one‐quantum mechanism ofN‐glycosidic bond cleavage. The ΦBvalues increase in the order guanine, thymine, adenine, cytosine, the latter being ΦC= 7 × 10−‐4for double‐stranded DNA under Ar and O2. The larger atlvalues in N2O‐saturated solution,e.g. Φc= 1.2 × 10−‐3are ascribed to additional base releaseviaOH‐adduct radicals. The ΦBvalues of homopolynucleotides increase in the order poly(G), poly(A) and poly(C),e.g. Φc‐= 7 × 10−‐2under Ar, as do the efficiencies for base release per radical cation (nB). A comparison of the nBvalues with the efficiencies of single‐strand breakage for poly(C), poly(A) and DNA shows a similar trend; both are markedly larger for pyrimidines than for purines. Pathways to undamaged bases, initiated from base radical cations, are proposed.
IMPROVED SURVIVAL FROM INTRACAVITARY PHOTODYNAMIC THERAPY OF RAT GLIOMA
Authors: Walstad Ying Jt. Diana , Brown J. Tony , Powers Stephen K.
Published: January 2008

Abstract—

The effectiveness of intratumoral photoradiation in photodynamic therapy (PDT) using a polyporphyrin photosensitizer was studied in the RT‐2 rat glioma model. One week after intracerebral implantation of RT‐2 cells, experimental rats received a single i.p. injection of 2 mg/kg of PhotofrinTM. After administration of the photosensitizer (48 h), the tumors were partially resected and the exposed cavity was irradiated with 15 J of laser light at a wavelength of 630 nm. Further treatment with a large craniectomy significantly enhanced rat survival. Control rats which received no photosensitizer but were treated with surgery, alone or in combination with laser irradiation, succumbed from early tumor recurrence. Photodynamic therapy without decompressive surgery resulted in hemorrhagic infarction of residual tumor and adjacent brain with focal cerebral edema which resulted in cerebral herniation and early death. Our results indicate that photodynamic therapy is effective in treating residual brain tumor but at the expense of brain tissue surrounding the tumor. Unless relieved, intracranial pressure from photodynamic therapy‐associated cerebral edema in this animal model resulted in shortened survival.
A FIBER‐OPTIC RATIO FLUOROMETER FOR MUTANT ISOLATION
Authors: Horwitz Benjamin A. , Amit Rivka , Llpson Edward D.
Published: January 2008

Abstract—

Mutants with altered fluorescence are likely to be modified in pigment composition or photochemistry. They can thus help address a variety of problems in photobiology, particularly in the areas of photosynthesis, photomorphogenesis and photobehavior. To aid in the screening for such mutants, we have developed an instrument for detecting fluorescence intensity relative to scattered light intensity. The instrument employs fiber optics for illumination and detection, and an analog electronic circuit to compute the ratio between fluorescence and scattered light. An application of the fluorometer to screen for Arabidopsis mutants altered in chlorophyll accumulation is described.
STRUCTURE‐ACTIVITY STUDIES OF PHOTOACTIVATED ANTIVIRAL AND CYTOTOXIC TRICYCLIC THIOPHENES
Authors: Marles Robin J. , Hudson James B. , Graham Elizabeth A. , Soucy‐Breau Chantal , Morand Peter , Compadre R. Lilia , Compadre Cesar M. , Towers G. H. Neil , Arnason J. Thor
Published: January 2008

Abstract—

The photoactivated antiviral and cytotoxic activities of the naturally occurring thiophene, α‐terthienyl (1), and 15 synthetic analogues were evaluated against murine cytomegalovirus and Sindbis virus, and murine mastocytoma cells. After irradiation with near UV light, α‐terthienyl and most of its analogues had significant toxicity, with minimum inhibitory concentrations in the range of 0.02–40 μM. In the absence of near UV irradiation, only one analogue had antiviral activity and five were cytotoxic. The most active analogues were those containing carboxylic acid, hydroxyl, or cyano substituents. Quantitative structure‐activity relationship analysis of thiophene phototoxicity suggested that the rate of singlet oxygen production is the primary determinant of antiviral and cytotoxic activities. For phototoxicity against murine cytomegalovirus, a significant role for hydrophobicity was also demonstrated. Tricyclic thiophenes show significant potential for photochemotherapy of viral infections and cancer. and further evaluation in animal models is recommended.
LEVELS OF REDUCED PYRIDINE NUCLEOTIDES AND LENS PHOTODAMAGE
Authors: Rao Ch. Mohan , Jr J. Samuel Zigler
Published: January 2008

Abstract—

Since most of the known factors that are associated with cataract formation are oxidative in nature, one would expect that a highly reductive environment might arrest or retard the progress of cataract formation. Reduced nucleotides, both NADH and NADPH, are potent reductants with a large negative redox potential of ‐ 320 mV. Lenses of certain species contain high levels of these nucleotides, presumably due to the presence of taxon specific crystallins. We have utilized this situation to investigate whether the levels of reduced pyridine nucleotides modulate photo‐oxidative damage to the lens. We have monitored the time dependent loss of tryptophan fluorescence upon photodamage for lenses from guinea pig, rabbit and frog (Rana) that contain high levels of pyridine nucleotides and compared with the lenses from rat, Xenopus and a mutant strain of guinea pig that contain significantly lower amounts of these nucleotides. About 75% and 90% of the initial fluorescence intensity is lost in the case of rat and Xenopus lenses, respectively, after a total of 35 min exposure. Rabbit, guinea pig and frog lenses, under identical conditions, show only about 35–40% loss of the initial fluorescence. It appears that the lenses that contain high levels of reduced nucleotides are less susceptible to photodamage. The observed anti‐oxidative role of reduced nucleotides in the lenses indicates the possibility of testing reductants (NADPH, NADH and their functional analogues) as potential candidates to therapeutically intervene in the process of cataractogenesis.
PHOTOSENSITIZATION BY 2‐CHLORO‐3, 11‐TRIDECADIENE‐5, 7, 9‐TRIYN‐1‐OL: DAMAGE TO ERYTHROCYTE MEMBRANES, Escherichia coli, AND DNA
Authors: Kagan Jacques , Wang Tian P. , Kagan Isabelle A. , Tuveson R. W. , Wang G.‐R. , Lam Jörgen
Published: January 2008

Abstract— The natural product 2‐chloro‐3, 11‐tridecadiene‐5, 7, 9‐triyn‐l‐ol (l) photosensitized the inactivation of Escherichia coli in the presence of near‐ultraviolet light (320–400 nm; NUV) under both aerobic and anaerobic conditions. A series of E. coli strains differing in DNA repair capabilities and catalase proficiency exhibited indistinguishable inactivation kinetics following treatment with the chemical plus NUV. The presence of carotenoids did afford some protection to E. coli against inactivation under aerobic conditions, consistent with the involvement of singlet oxygen. The photosensitized hemolysis of human erythrocytes occurred more rapidly in the absence than in the presence of oxygen. Aerobically, the onset of hemolysis was partially inhibited by NaN3 and by 2,6‐di‐t‐butyl 4‐methylphenol (BHT) but not by superoxide dismutase (SOD). The aerobic lipid peroxidation observed in the membranes of erythrocyte ghosts was completely inhibited by BHT, and partially by NaN3, but not by SOD. These results suggest that either lipid peroxidation of the membrane is not the main cause of photohemolysis or that BHT has insufficient access to intact erythrocyte lipids to protect them. Aerobically, crosslinking of membrane proteins was also observed; it was not affected by SOD, but was partially inhibited by BHT and NaN3. The anaerobic photosensitized hemolysis of erythrocytes was more rapid; a radical mechanism was suggested since BHT inhibited the hemolysis to a greater extent than under aerobic conditions. Neither lipid peroxidation nor protein crosslinking was observed under conditions believed to be anaerobic. A light‐dependent electron transfer to cytochrome c was obtained under argon but not under oxygen. Although induced mutations were not observed in the experiments with E. coli, I was capable of damaging both supercoiled pBR322 and Haemophilus influenzae transforming DNA in a manner that seemed to be equivalent under aerobic and anaerobic conditions. In conclusion, I can behave as typical photodynamic molecule under aerobic conditions but, in contrast to most photodynamic molecules, it is also phototoxic under anaerobic conditions. The extent to which the radical reactions detected under anaerobic reactions compete with the photodynamic processes when oxygen is present is not known.
PHOTOFRIN II PHOTOSENSITIZATION IS MUTAGENIC AT THE tk LOCUS IN MOUSE L5178Y CELLS
Authors: Rerko Ronald M. , Clay Marian E. , Antunez Antonio R. , Oleinick Nancy L. , Evans Helen H.
Published: January 2008

Abstract— Photosensitization mediated by Photofrin II (PFII) was found to be mutagenic at the heterozygous thymidine kinase (tk) locus in mouse L5178Y lymphoma strains LY‐S1 and LY‐R16 but not in strain LY‐R83 which is hemizygous at the tk locus. After treatments yielding 37% survival, the mutagenicity of photosensitization with PFII in strain LY‐S1 was similar to that of other mutagenic agents including x‐radiation, ethyl methanesulfonate, and photosensitization with chloroaluminum phthalocyanine (AIPcCI). Although both strain LY‐S1 and strain LY‐R16 were mutagenized by photosensitization with PFII, only strain LY‐S1 was mutagenized by photosensitization with AIPcCI. The non‐mutability of strain LY‐R83 following photodynamic treatment with either sensitizer may be because of the poor recovery of mutants with intergenic mutations in this TK+/0 hemizygous strain, whereas the non‐mutability of strain LY‐R16 subjected to photodynamic treatment with AIPcCI may be because LY‐R16 cells sustaining mutagenic damage do not survive for reasons other than the loss of an essential gene.
OBSERVATIONS ON THE SYNTHESIS AND in vivo PHOTODYNAMIC ACTIVITY OF SOME BENZOCHLORINS
Authors: Morgan Alan R. , Skalkos Dimitris , Maguire George , Rampersaud Ashraf , Garbo Greta , Keck Rick , Selman Steven H.
Published: January 2008

Abstract— An improved synthesis of benzochlorins is reported. Demetallation of the meso‐hydroxymethylvinyl derivative of octaethylporphyrin, followed by treatment with sulfuric acid results in cyclization to generate the corresponding octaethylbenzochlorin in high yield. Prolonged treatment with acid generates the sulfonated derivative. These sensitizers were shown to be efficient photodynamic agents in vivo. Animals bearing a transplanted N‐{4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl}formamide induced urothelial tumor were treated with either the benzochlorin or its sulfonated derivative. Irradiation of tumors 24 h later resulted in a significant tumoricidal effect in a short term assay. We conclude that benzochlorins warrant further examination as potential agents for use in photodynamic therapy.
PHOTOSENSITIZATION BY ANTICANCER AGENTS—10. ortho‐SEMIQUINONE AND SUPEROXIDE RADICALS PRODUCED DURING ANTHRAPYRAZOLE‐SENSITIZED OXIDATION OF CATECHOLS
Authors: Reszka Krzysztof , Lown J. William , Chignell Colin F.
Published: January 2008

Abstract— Photosensitized oxidation of catechol, 3,4‐dihydroxybenzoic acid (DHBA), 3,4‐dihydroxy‐dihydrocinnamic acid (DHCA), and 3,4‐dihydroxy‐phenylalanine (DOPA) by novel anticancer agents, anthrapyrazoles (AP), has been studied employing EPR and the spin trapping technique. The formation of o‐semiquinone radicals, the one‐electron oxidation products of the catechols, stabilized in the form of zinc ion complexes, has been demonstrated. Rate constants for the disproportionation of the semiquinone radical/Zn2+ complexes in (DMSO)/acetate buffer (pH 4.5, 1:1 vol/vol; 100 mM Zn2+) mixture have been determined to be 0.35 × 104 14 × 104 8.8 × 104 3 × 104M‐1 s‐1 for catechol, DHBA, DHCA and DOPA respectively. The presence of oxygen enhanced rather than inhibited the photogeneration of the o‐semiquinone radicals and facilitated their EPR detection. The EPR spectrum of the superoxide radical adduct with the spin trap 5,5‐dimethyl‐1‐pyrroline‐N‐oxide was observed for the first time during photosensitized oxidation of the catechols in acidic aqueous solutions and in DMSO/acetate buffer mixture.
A BIOFILM USED AS ULTRAVIOLET‐DOSIMETER
Authors: Quintern L. E. , Horneck G. , Eschweiler U. , Bücker H.
Published: January 2008

Abstract— A UV‐dosimeter has been developed for routine measurements which mainly weights the various components of the spectrum in relation to their damaging effects on a microorganism. For this purpose a biofilm was constructed, comprising dried spores of Bacillus subtilis (wild‐type or DNA repair defective strain), immobilized on transparent polyester plastic sheets. After irradiation, the biofilm was incubated in a growth medium. The proteins, synthesized by the immobilized microorganisms after spore germination and several cell divisions, were stained and determined by photometry, giving a measure of the biological activity. The ”biologically effective dose“ was determined from a calibration curve. It reflects the dose equivalent to that of the calibration source producing the same effect.

The UV‐response of the biofilm is additive and follows the reciprocity law in the range of fluence rates investigated. The response is nearly independent of temperature within the range of ‐20°C to +70°C as well as of humidity between about 37 and 80% relative humidity. Storage for up to 9 months at <70% relative humidity and room temperature does not significantly influence the viability of the spores.
RESEARCH NOTE: TRIPLET RADICAL ION PAIR STATE OF THE Zn‐PORPHYRIN‐VIOLOGEN DYAD AS A MAGNETIC FIELD SENSITIVE PROBE OF PHASE TRANSITIONS IN SMALL UNILAMELLAR VESICLES
Authors: Shafirovich Vladimir Ya. , Batova Elena E. , Levin Peter P.
Published: January 2008

Abstract— The magnetic field effect on the recombination kinetics of the triplet radical ion pair state (RIPS) of the Zn‐porphyrin‐viologen dyad (P‐Ph‐Vi2+) in the small unilamellar vesicles (SUV) of d, l‐dipalmitoyl‐α‐phosphatidylcholine has been studied by the nanosecond laser flash photolysis technique at 5–60°C. The increase in temperature from 25 to 40°C enhances the rate constant (kr) of the RIPS recombination in zero magnetic field from 0.9 × 106 to 1.6 × 106 s‐1 while k, is temperature insensitive at 5–25 and 40–60°C. The typical break in the kr temperature dependence is observed in the temperature range of the phase transition of the SUV bilayers from the solid to the fluid state. The kr value in a strong magnetic field (B= 0.24 T) is equal to 2.7 × 105 s‐1 it is independent of temperature at 5–60°C. The shape of the magnetic field dependence of kr is unaffected by the phase transition of the SUV bilayers and is characterized by the existence of an initial plateau of kr at B= 0 to 0.5 mT.
PHOTOACOUSTIC DETECTION OF TRIPLET STATE AND SINGLET OXYGEN IN HIGHLY ABSORBING SAMPLES
Authors: Ouzafe Mohamed , Poulet Patrick , Chambron Jacques
Published: January 2008

Abstract—A photoacoustic (PA) effect theory taking into account two heat sources corresponding to the radiationless relaxation processes of two states of different lifetimes and to the heat diffusion across the sample is herewith presented. Results obtained demonstrate that the amplitude and the phase of the PA signal depend on the sample's thermal properties, on its optical absorption coefficient, on the lifetime of the long‐lived excited state, and on the ratio of the two heat sources. This ratio can be expressed as a function of the product of the energy of the excited state times the quantum yield of its production. Simulations of PA amplitude and phase variationsvslight modulation frequency exhibit new features of the PA signal: phase inversion and fast decrease of the amplitude. Experimental verifications were carried out on solutions and gels. Fitting of the amplitude and phase variations allow us to measure the lifetime and conversion yield of the intermediate state which can be a triplet state or singlet oxygen, O2(1Δg). The addition of an acceptor, specific to O2(1Δg), induces changes in the amplitude of the PA signal which can be used to study the production and deactivation of this excited form of oxygen. This work demonstrates the usefullness of PA in the detection of metastable excited states such as the triplet state and singlet oxygen and in their quantitative analysis.
THE PHOTOCHEMISTRY OF 5‐METHYLCYTOSINE AND 5‐METHYL‐2′‐DEOXYCYTIDINE IN AQUEOUS SOLUTION
Authors: Celewicz Lech , Sheilar Martin D.
Published: January 2008

Abstract—The nucleobase 5‐methylcytosine (I) is a minor component of eukaryotic DNA thought to be important in regulation of gene expression. The photochemical reactions of this nucleobase and its 2′‐deoxyribonucleoside, 5‐methyl‐2′‐deoxycytidine (II), in water have been studied. These reactions lead, respectively, to 3‐amino‐2‐methylacrylamidine (Ib) and 3‐(2‐erythro‐d‐pentopyranos‐1‐yl) amino‐2‐methylacrylamidine (IIb) as the main photoproducts. The structure of the photoproducts was established by spectroscopic methods (1H and13C NMR, UV spectroscopy, electron impact and liquid secondary ion mass spectrometry); in the case ofIb, confirmatory evidence was obtained by chemical methods (photolysis of 5‐methyl[2–13C]cytosine, hydrolysis ofN‐carbomethoxy‐3‐amino‐2‐methylacryl‐amidine and reaction ofIbwith 1,1′‐carbonyldiimidazole to giveI). The quantum yield for formation ofIbwas determined to be 1.8 × 10‐3at pH 7.5 while the quantum yield for formation ofIIbhas a lower value of 0.2 × 10‐3at pH 7.5. These quantum yields depend strongly on pH and reach maximum values of 2.0 × 10‐3at pH 7.0 (Ib) and 0.6 × 10‐3at pH 5.0 (IIb). The mechanism of formation ofIb(orIIb) is proposed to involve nucleophilic attack of water on the C‐2 position of photoexcitedI(orII), followed by ring opening and decarboxylation of an intermediate carbamic acid.
EFFECT OF VITAMIN E ON CYTOTOXICITY, DNA SINGLE STRAND BREAKS, CHROMOSOMAL ABERRATIONS, AND MUTATION IN CHINESE HAMSTER V‐79 CELLS EXPOSED TO ULTRAVIOLET‐B LIGHT
Authors: Sugiyama Masayasu , Tsuzuki Katsuyuki , Matsumoto Kumi , Ogura Ryohei
Published: January 2008

Abstract— The effect of pretreatment with vitamin E on cytotoxicity, DNA single strand breaks, and chromosomal aberrations as well as on mutation induced by ultraviolet‐B light (UV‐B) was investigated in Chinese hamster V‐79 cells. Cellular pretreatment with non‐toxic levels of 25 μMα‐tocopherol succinate (vitamin E) for 24 h prior to exposure resulted in a 10‐fold increase in cellular levels of α‐tocopherol. Using a colony‐forming assay, this pretreatment decreased the cytotoxicity of UV‐B light. However, alkaline elution assays demonstrated that pretreatment with vitamin E did not affect the number of DNA single strand breaks caused by UV‐B light. In addition, UV‐B exposure produced a dose‐dependent induction of chromosomal aberrations and mutations at the HGPRT locus, and neither of these actions of UV‐B was influenced by pretreatment with the vitamin. These results suggest that vitamin E protects cells from UV‐B‐induced cytotoxicity, possibly through its ability to scavenge free radicals. The results also suggest that the extent of genotoxicity induced by UV‐B light may not correlate directly with the cytotoxic action of this wavelength region in sunlight.
LIGHT‐INDUCED SYNTHESIS OF ANTHOCYANIN IN CARROT CELLS IN SUSPENSION—IV. THE ACTION SPECTRUM
Authors: Takeda Junko , Abe Shunnosuke
Published: January 2008

Abstract— Using carrot cell suspension in 2,4‐dichlorophenoxyacetic acid (2,4‐D)‐depleted culture medium, fluence‐response curves for the formation of anthocyanin were determined at various wavelengths from 250 to 800 nm. In the fluence‐response curves at wavelengths between 260 and 330 nm, the response showed a sharp fluence‐dependent increase after the fluence exceeded threshold level at the respective wavelength. Such a sharp increase in response was not observed by light at 450 nm or longer wavelengths, although the response obtained by higher fluence of such light was always higher than that in the dark control. Action spectra determined at the sharp increasing phase of the response showed the single peak at 280 nm which equals the absorption maximum of UV‐B photoreceptor.

Although red (R)‐light alone had a minor effect on anthocyanin accumulation, it modulated the action of UV‐B light. That is, when carrot cells were irradiated with R‐light either before or after UV‐B irradiation, anthocyanin formation was greatly enhanced above the level enhanced by UV‐B light alone. The most effective wavelength for this enhancement was 660 nm. The effect of R‐light on the anthocyanin formation of the UV‐B irradiated cells was reversed by immediately following it with far‐red light, suggesting the involvement of phytochrome in the R‐effect.
LOCATION OF THE CAROTENOID 2Ag‐STATE AND ITS ROLE IN PHOTOSYNTHESIS
Authors: Gillbro T. , Andersson P. O. , Liu R. S. H. , Asato A. E. , Takaishi S. , Cogdell R. J.
Published: January 2008

The location of the carotenoid 2Ag‐state (S1) was studied by fluorescence spectroscopy in two series of carotenoids. One consisted of natural polyenes like phytoene, phytofluene, β‐carotene, and neurosporene, and the other of minicarotenes, i.e., compounds similar to β‐carotene, but with a smaller number of double bonds (n=3–9). A decrease of the S1‐S0 energy gap with n was observed in both series, and extrapolation to n= 11 gave the energies 14 500 and 13 200 cm−1 for β‐carotene and lycopene, respectively. The neurosporene S1 state was located at ca 16 000 cm−1. A good relationship between the nonradiative relaxation rate and the number of conjugation was observed. The rate increased by a factor of 2.5 per double bond. The possible role of the S1 state in reversible carotenoid ← chlorophyll electron‐exchange energy transfer is discussed.
A COMPARISON OF PHYCOCYANINS FROM THREE DIFFERENT SPECIES OF CYANOBACTERIA EMPLOYING RESONANCE‐ENHANCED COHERENT ANTI‐STOKES RAMAN SPECTROSCOPY
Authors: Schneider S. , Prenzel C.‐J. , Brehm G. , Gedeck P. , Sai P. S. Maruthi , Gottschalk L. , Scheer H.
Published: January 2008

Resonance‐enhanced coherent anti‐Stokes Raman spectra are recorded for monomers and trimers of phycocyanin from three different cyanobacteria: Westiellopsis prolifica, Mastigocladus laminosus and Spirulina platensis. It is shown that upon aggregation from monomer to trimer the electronic structures of both the α84 and β84 chromophores are changed. The spectra of the trimers originating from S. platensis and M. laminosus are very similar to each other, but distinctly different from the spectrum of W. prolifica.
SPECTRAL FORMS AND ORIENTATION OF BACTERIOCHLOROPHYLLS c AND α IN CHLOROSOMES OF THE GREEN PHOTOSYNTHETIC BACTERIUM Chloroflexus aurantiacus
Authors: Matsuura Katsumi , Hirota Masamitsu , Shimada Keizo , Mimuro Mamoru
Published: January 2008

Spectral forms of bacteriochlorophyll (Bchl) in chlorosomes were analyzed by linear dichroism, circular dichroism (CD), and deconvolution of these spectra. Isolated chlorosomes were embedded in polyacrylamide gels and compressed unidirectionally (along the x‐axis) while allowing the gel to stretch in another direction (along the z‐axis). The chlorosomes were aligned three‐dimensionally due to their flat oblong shape; the longest axis was presumed to parallel the z‐axis, its shortest axis was presumed to parallel the x‐axis, and the intermediate‐length axis was presumed to parallel the y‐axis. Degrees of polarization (AI− A1)/(AI+ A1) of Bchl c and a measured from the y‐axis with linearly polarized light were significantly different from those measured from the x‐axis. Deconvolution of spectra into components revealed the presence of two major forms of Bchl c with peaks at 744 nm and 727 nm. The degrees of polarization of the 744 and 727 nm spectral forms were 0.76 and 0.59 from the y‐axis and 0.48 and 0.39 from the x‐axis, respectively. The degrees of polarization of Bchl a794 were –0.21 from the y‐axis and 0.12 from the x‐axis. These values indicate that the direction of the Qy transition moment of Bchl c744 is almost completely parallel to the longest axis of chlorosomes and that of Bchl c727 is also nearly, but slightly less so, parallel to the longest axis of the chlorosomes. The Qy transition moment of the baseplate Bchl a peak at 794 nm is nearly perpendicular to the longest axis and parallel to the shortest axis: that is, it is perpendicular to the associated membrane plane in the cell. These alignments of Bchl transition moments in chlorosomes were lost after suspending the chlorosomes in a solution saturated with 1‐hexanol accompanying a shift in the peak position from 742 nm to 670 nm. The alignment recovered after the hexanol concentration was decreased. The presence of two major spectral forms of Bchl c was supported by the deconvolution of CD spectra and absorption spectra.
DIRECT EXPOSURE OF MANNALIAN CELLS TO PURE EXOGENOUS SINGLET OXYGEN (ΔgO2
Authors: Dahl Thomas A.
Published: January 2008

Mammalian cells attached to membrane filters or deposited on filters without attachment were exposed to gas‐phase singlet oxygen (1O2) in the absence of any other reactants. Cells were exposed in a monolayer or less, in the absence of external medium, during steady‐state 1O2 generation, ensuring that singlet oxygen impinged directly and equally on all cells simultaneously. The current methodology for cell exposure ensures that 1O2 is initially the only reactive species to which the cells are exposed. Results seen with this system can therefore be attributed solely and unambiguously to events initiated by 1O2. Further, all cells in the sample receive the same magnitude of exposure per surface area per time interval, which supports calculations of the amount of 1O2 required for irreversible cell damage, based on measured 1O2 flux and exposed cell surface area. Exposure to pure 1O2 irreversibly damaged a variety of cell types, including rat basophilic leukemia, human squamous carcinoma and Chinese hamster lung fibroblast cell lines, and murine primary hepatocytes. Cell survival curves following exposure to 1O2 followed apparent first‐order kinetics. A large number of singlet oxygen collisions (˜ 1012‐1013) were required to inactivate a cell, on average, indicating a low probability that singlet oxygen collision will reduce cell survival. Regardless of cell type or the survival endpoint measured, lethal toxicity required a fairly constant number of 1O2 collisions per cell. This poses a serious caveat in the assignment of causality in correlating 1O2‐initiated cellular damage with mechanism of death, i.e. most damage observed will not be related to death. The importance of various toxic effects of 1O2, whether lethal or nonlethal, will depend on the magnitude of exposure and therefore on the context in which exposure occurs.
EFFECTIVE PHOTODYNAMIC ACTION BY RHODAMINE 123 LEADING TO PHOTOSENSITIZED KILLING OF CHINESE HAMSTER OVARY CELLS IN TISSUE CULTURE AND A PROPOSED MECHANISM
Authors: Richmond Robert C. , O'Hara Julia A.
Published: January 2008

The effectiveness of rhodamine 123 (R123) as a photosensitizer of cell killing is relatively low and correlates with its inefficient production of singlet oxygen. The known selective retention of R123 in the mitochondria of epithelially derived carcinoma cells, however, is a selective feature that could lead to a more useful therapeutic ratio if photosensitizing effectiveness could be increased. Chinese hamster ovary (CHO) cells in tissue culture were therefore exposed to R123 shortly before and during illumination under conditions controlled for oxygen concentration and temperature. Effective photosensitization of cell killing, as judged by colony formation, was produced by 95% but not by 19% O2 during illumination of cells at 5d̀C or 37d̀C, and this was additionally enhanced at the sublethal temperature of 42d̀C. Two CHO cell lines were examined; one line, CHO‐AA8, was proficient in the repair of DNA damage and the parent to the second line, CHO‐EM9, that was deficient in the repair of DNA strand breaks. Cells of both lines incorporated R123 to a similar degree and were similarly photosensitized by the presence of igh oxygen concentration. Furthermore, plasma membrane damage as judged by teh exclusion of trypan blue was not observed immediately after illumination in the presence of R123, but was seen in the presence of meso‐tetra‐(4‐sulfonatophenyl)‐porphine (TPPS4). The extent of damage to the plasma membrane by TPPS4 was greater in the presence of 95% compared to 19% O2 during illumination. Photodynamic action at the level of teh plasma membrane appears to contribute to photosensitization by TPPS4 but not by R123 soon after exposure of cells to these sensitizers. It is hypothesized that photodynamic action by R123 is the primary mechanism causing the observed photosensitization of cell killing, and that mitochondria are teh site of photosensitized damage responsible for this killing.
PHOSPHORESCENCE LIFETIME STUDIES OF INTERACTIONS BETWEEN SERUM ALBUMINS AND SODIUM DODECYL SULFATE
Authors: Enescu Mironel , Ionescu Roxana , Dumbraveanu Gheorghe , Pascu Mihai L.
Published: January 2008

Binding of sodium dodecyl sulfate (SDS) to bovine serum albumin (BSA) and human serum albumin (HSA) in aqueous solutions at room temperature induces significant changes in the phosphorescence lifetime of tryptophan (Trp) residues. A steep rise of the phosphorescence lifetime from 1.9 ms to 10.0 ms for BSA and from 1.9 ms to 5.5 ms for HSA is observed when the total SDS concentration increased from 0.0 mM to 0.22 mM at 1 mg/mL protein concentration. As the total SDS concentrationis further inccreased to 2.2 mM, a slower increase in the phosphorescence lifetime is observed, from 10.0 ms to 19.5 ms for BSA and from 5.5 ms to 7.2 ms for HSA. It appears that the phosphorescence lifetime modifications are mainly due to an increase of protein matrix rigidity around Trp residues. The observed differences (between HSA and BSA) allow us to distinguish the contribution of the two Trp residues to the BSA phosphorescence.
USE OF OCTADECYLRHODAMINE FLUORESCENCE DEQUENCHING TO STUDY VESICULAR STOMATITIS VIRUS FUSION WITH HUMAN AGED RED BLOOD CELLS*
Authors: Pozzi Deleana , Lisi Antonella , Ros Ivan De , Ferroni Lucietta , Giuliani Anna , Ravagnan Glanpietro , Grimaldr Settimio
Published: January 2008

Human erythrocytes were separated into five fractions representing different age groups. In each group phospholipid inside‐outside translocation was determined by quantitation of the amino phospholipids phosphatidylserine and phosphatidylethanolamine and their lyso‐derivatives by thin layer chromatography. To assess the role of transbilayer phospholipid distribution in the recognition and fusion of vesicular stomatitis virus (VSV) and human aged erythrocytes, we monitored the fusion kinetics using the octadecylrhodamine dequenching assay.

Fusion of VSV with each single group of red blood cells (RBC) was not detectable with the youngest cells (Fl group) but increased with RBC aging (F2‐F5 groups). The same increase in fusion was observed with microvesicles generated from RBC in which aging was mimicked by incubating the cells with Ca2+ in the presence of the Ca2+ ionophore A23187.

Conversion of the aminophospholipids to the trinitrophenyl derivative by reaction with trinitrobenzensulfonate completely inhibits fusion on ghosts in which aging was artificially induced by translocation of aminophospholipids in the outer leaflet (symmetric ghosts).

These results indicate that RBC become susceptible to VSV fusion during aging and in all pathology related to the aging process.
INFLUENCE OF THE PEPTIDE BOND ON THE SINGLET MOLECULAR OXYGEN‐MEDIATED (O2[g]) PHOTOOXIDATION OF HISTIDINE and METHIONINE DIPEPTIDES. A KINETIC STUDY
Authors: Miskoski Sandra , García Norman A.
Published: January 2008

The dye‐sensitized photooxidation of l‐histidine (His) and l‐methionine (Met) and their simplest dipeptides with glycine (Gly) (His‐Gly, Gly‐His, Gly‐Met) and Met‐methyl ester (Met‐ME) mediated by singlet molecular oxygen (O2[g]) was studied.

The overall rate constants in acetonitrile‐H2O (Kt) for O2(1g) quenching were measured by time‐resolved phosphorescence detection. In H2O a competitive kinetic method was employed. In both solvents the reactive rate constants (Kt,) were determined to discriminate between the overall and physical contributions to the quenching. The kinetic and mechanistic aspects of the interaction are discussed.

For His‐Gly, the peptide bond has practically no effect on the kinetics of photooxidation. For Gly‐His the overall rate constant is much higher than that for His and His‐Gly, in both H2O and acetonitrile‐H2O. The main contribution to k1 (for Gly‐His) is the physical quenching of O2(1g)‐ In water the kt/kr ratio for free His and His‐Gly is 1.0, reaching a value of 2.0 in the organic solvent‐H2O mixture. The rates of‐NH2 loss upon sensitized photooxidation in all cases parallel the trend of kr values. The main results for the His series indicate that: (1) a polar environment favors autoprotection (i.e. an increase in the contribution of physical quenching) against photodynamic effects; (2) only the rate constant for reactive interaction with O2[g] does not depend on the location of the peptide bond involving His.

For Met derivatives the kt, values are higher in both solvents than that for free Met. Only for the free amino acid in H2O is the interaction with O2(1g) totally reactive. For Gly‐Met and Met‐ME the physical quenching prevails: kt, is, in both solvents, about one order of magnitude higher than kr. According to our results on ‐NH2 loss and on the basis of previous investigations by others, the photooxidative products distribution in the Met series indicates that Gly‐Met yields only dehydroMet, whereas Met and Met‐ME produce a mixture of Met‐sulfoxide and the Met‐dehydro compound.
OBSERVATION OF PHASE TRANSITIONS IN INTACT LEAVES BY INTRINSIC LOW‐LEVEL CHEMILUMINESCENCE
Authors: Roschger P. , Scott R. Q. , Devaraj B. , Inaba H.
Published: January 2008

The Arrhenius plots of a remnant intrinsic ultraweak light emission from dark‐adapted leaves of hibiscus, bean, cucumber, tomato and spinach exhibit strong linear behavior, despite the structural heterogeneity of the intact leaf. Well‐defined break points within the temperature range from 8°C to 17°C could be found in these plant species. In the case of hibiscus and cucumber an additional feature of a thermotropic phase change around 20°C and 24°C, respectively, could be detected. However, in the case of spinach, a representative of a chilling resistant plant species, the changes in activation energies obtained were only minor. Isolated chloroplasts of spinach leaves did not show identical thermal behavior of luminescence in comparison with the intact leaf. The activation energies were significantly lower and the transition features were different compared to intact leaves. A possible relationship between the thermal behavior of low‐level chemiluminescence and the chilling sensitivity of plants is suggested.
UPTAKE AND BIOCONVERSION OF α‐TOCOPHERYL ACETATE TO α‐TOCOPHEROL IN SKIN OF HAIRLESS MICE
Authors: Norkus E. P. , Bryce G. F. , Bhagavan H. N.
Published: January 2008

Abstract— The photoprotective effect of topically applied α‐tocopheryl acetate (vitamin E acetate), a stable derivative of α‐tocopherol (vitamin E), and its possible bioconversion to the active antioxidant species (α‐tocopherol) was examined in skin tissue of female hairless mice (HRS/J) exposed to UV‐B irradiation. Our results indicate that topically applied α‐tocopheryl acetate is absorbed into and retained by skin tissue. Furthermore, skin tissue from UV‐B‐irradiated animals that received daily topical α‐tocopheryl acetate treatments contained significantly higher levels (P < 0.001) of α‐tocopheryl acetate than non‐UV‐B‐irradiated mice that received identical daily topical α‐tocopheryl acetate treatments. Finally, free α‐tocopherol levels in skin also were significantly increased (P < 0.00 1) by topical applications of α‐tocopheryl acetate and skin levels of free α‐tocopherol were significantly greater (P < 0.001) in UV‐B‐irradiated animals that received daily topical α‐tocopheryl acetate treatments than in non‐UV‐Birradiated animals. These results suggest that UV‐B irradiation enhances both the absorption of α‐tocopheryl acetate and its bioconversion to free α‐tocopherol.
PHOTOSENSORY TRANSDUCTION IN CILIATES. II. POSSIBLE ROLE OF G‐PROTEIN AND cGMP IN Stentor coeruleus
Authors: Fabczak Hanna , Park PhunBum , Fabczak Stanislaw , Song Pill‐Soon
Published: January 2008

Abstract— The heterotrichous ciliate, Stentor coerulus, exhibits a welll defines photophobic response to a sudden increase in the intensity of visible light. the phobic reactions usually appear with a latency perios (i.e. a time delay between the onset of the stimulus and the stop response). This latency of phobic response was significatly increased when the cells werw incubated with 8‐bromo‐guanosine3′,5′‐cyclic monophospjhate. In the presence of this nucleotide, a reduction of cell responsiveness (i.e. the number of photophobically responding cells) was also observed. similar effects were observed when cells were treated with pertussis toxin, a G‐protein activity modulator, and 3′‐isobutyl‐methylxanthine, an inhibitor of guanosine 3′, 5′‐cyclic monophosphate (cGMP) phosphodiesterase. the G‐protein activator fluoroaluminate and 6‐anilino‐5,8‐quinolinedione (LY 83583) (an effective agent for lowerin cellular cGMP levels) showed opposite effects on hte cell photophobic response. These result indirectly suggesnt that the level of cytoplamic cGMP, possibly modulated by a G‐protein‐coupled CGMP phosphodiesterase, plays a phototreasducing role in Stentor. In addition, using an antiserum raised against bovine transducin, a cross reacting protein with an apparent molecular mass of 39 kDa was detected on immunoblots. The α‐subunits of aStentor G‐protein has also been partially cloned and sequenced. However, the possible coupling between the G‐protein and the putative phosphodiesterase remains to be established.
BIPHASIC M DECAY OF HIGH pH DEHYDRATED PURPLE MEMBRANE STUDIED WITH FOURIER TRANSFORM INFRARED SPECTROSCOPY: A MODEL ACCOUNTING FOR FUNCTIONAL DIFFERENCES BETWEEN DIFFERENT M FORMS
Authors: Takei H. , Lewis A.
Published: January 2008

Abstract— A purple membrane film treated with a pH 10 buffer and subsequently dehydrated exhibits an M intermediate that consists of two clearly separable fast‐and slow‐decaying forms at 275 K; 45% decays thermally within the first 10 min but most of the remaining is stable even after 25 min. Fourier transform infrared spectroscopy is applied to investigate differences in molecular structural changes accompanying thermal decay of the fast‐decaying form and photochemical decay (M bacteriorhodopsin back photoreaction) of the slow‐decaying form. When difference spectra are taken of the two decay transitions, small but highly reproducible differences are observed. These suggest differences in molecular structural changes accompanying the two decay transitionas. However, the high degree of similarity in the spectra also suggests that these forms of M are not in thermal equilibrium with other intermediates such as N. We propose a model to account for functional differences between two M forms.