bluuebunny/crossref_metadata_2025_split huggingface dataset:
HYDROGEN PEROXIDE‐DEPENDENT GENERATION OF SINGLET MOLECULAR OXYGEN BY HUMAN SALIVA: ITS DETECTION BY CHEMILUMINESCENCE FROM ACypridinaLUCIFERIN ANALOG
Authors: Takahama Umeo 
Published: January 2008

AbstractBy the addition of hydrogen peroxide to human saliva, chemiluminescence fromCypridinaluciferin analog (CCLA) and oxygen evolution were observed. Chemiluminescence was inhibited by inhibitors of salivary peroxidase, azide and cyanide and by a singlet oxygen quencher, crocin. Deuterium oxide (99.75%) stimulated the initial increase of CCLA by15–50% and the integrated CCLA 2.1‐3.6‐fold. The result suggest that the generation of singlet oxygen by peroxidase in human saliva depends on hydrogen peroxide.
A FLUOROGENIC ACTINOMETER FOR NUCLEIC ACID PHOTOCHEMISTRY UTILIZING 1‐DEAZAPURINE N(3)‐OXIDES
Authors: Blaney Ruth , Al‐Nakib Tahsin , Davies R. Jeremy H. 
Published: January 2008

AbstractA convenient and very sensitive actinometery system for UV radiation with wavelengths in the range250–310 nm is described, which is based on the fluorogenic photorearrangement of 1‐deazapurine N(3)‐oxide. The product, 1‐deazapruin‐2‐one, can be estimated fluoremetrically in the presence of the N‐oxide of 1‐deazapurine and 1‐methyl‐1‐deazapurine fail in the range 0.13‐0.15 and do not vary significantly with wavelength. There is potential for using 1‐deazupurine N(3)‐oxides as UV‐photoactivable fluorophores.
PHOTODYNAMIC KILLING OF Dictyostelium discoideum AMOEBAE MEDIATED BY 4′,5′‐DIIODOFLUORESCEIN ISOTHIOCYANATE DEXTRAN. A STRATEGY FOR THE ISOLATION OF THERMOCONDITIONAL ENDOCYTOSIS MUTANTS
Authors: Labrousse Arnaud , Satre Michel 
Published: January 2008

Abstract4′, 5′‐Diiodofluorescein dextran has been synthesized by iodination of fluorescein dextran and it was used as a sensitizer in photodynamic killing of amoebae of the cellular slime mold Dictyostelium discoideum. Amoebae from axenic strain AX2 incubated in the presence of 4′,5′‐diiodofluorescein dextran efficiently internalized the molecule by fluid‐phase pinocytosis. Subsequently, illumination of cells showed dose‐ and time‐dependent loss of viability. The tertiary amine, 2,4‐ diaza[2,2,2]bicyclooctane, significantly decreased phototoxicity, whereas the presence of D2O increased phototoxicity. These effects were fully consistent with a role for excited‐state singlet oxygen generated inside the endosomal compartments in the mechanism of photoinjury. A strategy was developed to enrich for temperature‐sensitive Dictyostelium endocytosis mutants in a nitrosoguanidine mutagenized population. Incubation with 4′,5′‐diiodofluorescein dextran at 27°C to load endosomal compartments was followed by light treatment to kill parent‐type cells selectively. In contrast, mutants unable to internalize the fluid‐phase marker would survive the treatment. Six temperature‐sensitive clones were selected that grew normally at 21°C but did not grow at 27°C. They all showed markedly decreased fluid‐phase pinocytosis capacity at nonpermissive temperature as compared to their activity at 21 °C. These mutant strains should be useful in studies designed to characterize endocytosis mechanisms in Dictyostelium.
TIME‐RESOLVED STUDIES OF SINGLET‐OXYGEN EMISSION FROM L1210 LEUKEMIA CELLS LABELED WITH 5‐(N‐HEXADECANOYL)AMINO EOSIN. A COMPARISON WITH A ONE‐DIMENSIONAL MODEL OF SINGLET‐OXYGEN DIFFUSION AND QUENCHING
Authors: Baker Ayse , Kanofsky Jeffrey R. 
Published: January 2008

Abstract— Time‐resolved measurements were made of near‐infrared emission from 5‐(N‐hexadecanoyl)amino‐eosinlabeled L1210 leukemia cells following pulsed‐laser excitation. The cells were suspended in phosphate‐buffered saline made with deuterium oxide solvent. A significant fraction of the emission occuring10–80 μs after the laser pulse was due to singlet oxygen. This singlet‐oxygen emission is believed to result from singlet oxygen generated near the cell‐membrane surface, where 5‐(N‐hexadecanoyl)amino eosin is known to concentrate, and then diffusing out into the buffer. The intensity and the kinetics of the experimentally observed singlet‐oxygen emission were in excellent agreement with the predictions of a theoretical one‐dimensional model of singlet‐oxygen diffusion and quenching.During the10–80 μs time period studied, most of the singlet oxygen was located in the buffer. Thus, the use of water‐soluble singlet‐oxygen quenchers, such as histidine, provide one means of separating the singlet‐oxygen emission quenchers, such as histidine, provide one means of separating the singlet‐oxygen emission from other sources of light during this time interval.
LASER CROSS‐LINKING OF PROTEINS TO NUCLEIC ACIDS: PHOTODEGRADATION AND ALTERNATIVE PHOTOPRODUCTS OF THE BACTERIOPHAGE T4 GENE 32 PROTEIN
Authors: Kubasek William L. , Spann Dennis , Hockensmith Joel W. 
Published: January 2008

AbstractPulsed laser cross‐linking provides a means of introducing a covalent bond between proteins and the nucleic acids to which they are bound. This rapid cross‐linking effectively traps the equilibrium that exists at the moment of irradiation and thus allows examination of the protein‐nucleic acid interactions that existed. Laser irradiation may also induce photodestruction of protein and we have used the bacteriophage T4 gene 32 protein to investigate this phenomenon. Our results show that both nonspecific and specific photoproducts can occur, specifically at wavelengths where the peptide backbone of proteins is known to absorb. These results demonstrate that nonspecific photodegradation can be correlated with the formation of a specific photodegradation product. The formation of this product was monitored to show that product yield is nonlinearly dependent on laser power and wavelength. We have also investigated an unexpected photoproduct whose formation is dependent on the length of the polynucleotide to which the gene 32 protein binds and that further demonstrates the complexities of analyzing protein‐nucleic acid interactions through the use of UV laser cross‐linking. These data provide essential information for the establishment of appropriate conditions for future studies that use UV cross‐linking of protein‐nucleic acid complexes.
QUANTIFICATION OF THE SOLVENT EFFECTS ON THE TRIPLET QUANTUM YIELD OF PSORALEN BY THE “LINEAR SOLVATION ENERGY RELATIONSHIP”
Authors: Melo Teresa Sae , Bazin Marc , Ronfard‐Haret Jean‐Claude , Santus René 
Published: January 2008

AbstractTriplet formation quantum yields (Φτ) of psoralen in a set of 17 pure solvents ranging from n‐hexane to water and in dioxane: water mixtures were obtained by nanosecond laser flash photolysis. The triplet yield increases with solvent polarity. The extremum values are 0.009 and 0.545 in n‐hexane and water, respectively. Good correlations of the experimental Φτ values with empirical “polarity” scales (Dimroth/Reichardt's ET [30], Kamlet/Taft's solva‐tochromic parameters β, and α, and Swains acity/basity AS/BS) were obtained: Ln(φT‐1 ‐ 1) = 8.86 ‐ 0.143ET(30) Ln(φT‐1 ‐ 1) = 4.40 ‐ 2.34τ ‐ 1.70α Ln(φT‐1 ‐ 1) = 4.65 ‐ 3.72As ‐ 1.12Bs The results are discussed in terms of the sensitivity of psoralen triplet quantum yield to solvent polarity and hydrogen‐bonding abilities.
ABSORPTION AND FLUORESCENCE SPECTROSCOPIC STUDIES ON DIMERIZATION OF CHLOROALUMINUM (III) PHTHALOCYANINE TETRASULFONATE IN AQUEOUS ALCOHOLIC SOLUTIONS
Authors: Yoon Minjoong , Cheon Youngjin , Kim Dongho 
Published: January 2008

AbstractDimerization of chloroaluminum (III) phthalocyanine tetrasulfonates (AIPCS) has been observed in different aqueous alcoholic solvents at room temperature by absorption and fluorescence spectroscopic methods. Both absorption and fluorescence spectral bands of the dimer are red shifted by ca 550 cm‐1 from the monomer Q bands in the corresponding spectra, suggesting that the interaction energy between the two monomer subunits is very weak. The fluorescence lifetime of the dimer is longer (ca 9.5 ns) than that of the monomer (ca 7–8 ns). These spectral behaviors of AIPCS dimer contrast with those of transition‐metallaloid phthalocyanine dimers, which usually have a nonfluorescent face‐to‐face stacking conformation. The dimer fluorescence is interpreted to be due to the fact that the lowest excited singlet state of the dimer is lower in energy than a charge‐resonance state, based on the excitoncoupling theory applied to the face‐to‐face slipping conformation. The dimerization constant determined spectrometrically decreases with an increase of water content in the aqueous alcoholic solution. Propanol and ethanol have been observed to be more effective than methanol in promoting dimerization. These results indicate that a specific interaction of water with AIPCS plays an important role in the inhibition of dimerization of AIPCS.
THE CHLOROPHYLL a AGGREGATE ABSORBING NEAR 685 nm IS SELECTIVELY FORMED IN AQUEOUS TETRAHYDROFURAN*
Authors: Uehara Kaku , Hioki Yuko , Mimuro Mamoru 
Published: January 2008

AbstractAn aqueous solution of 2–12% (vol/vol) tetrahydrofuran (THF) induced the selective aggregation of chlorophyll a (Chl a) to form a novel species, A‐685, absorbing near 685 nm. The formation of A‐685 was closely correlated with a decrease in water activity of the solution. A Raman spectrum of the Chl a species formed in the presence of 6% THF suggests a unique interaction among Chl a, solvent THF and water molecules to give a stacked aggregate (Chl a.THF.H2O.THF.Chl a). The circular dichroic spectrum of the Chl a species formed in the 6% THF aqueous solution showed an intense signal that had negative and positive wings with about 100‐fold larger molar ellipticity for the A‐685 than for monomer. However, Chl a', the C10 epimer of Chl a, and chlorophyllide, with a phytyl chain replaced by an ethyl group, did not form A‐685 in 6% THF. These clearly indicate that 10‐methylcarboxylate and the phytyl chain have a significant role in stabilizing A‐685. A possible structure for A‐685 is proposed as a novel in vitro model for the P‐680 Chl a dimer.
A PHOTOPHYSICAL STUDY OF SOLVATOCHROMIC PROBE 6‐PROPIONYL‐Z(N,N‐DIMETHYLAMINO)NAPHTHALENE (PRODAN) IN SOLUTION
Authors: Bunker Christopher E. , Bowen Tracey L. , Sun Ya‐Ping 
Published: January 2008

AbstractA photophysical study of 6‐propionyl‐2‐(N,N‐dimethylamino)naphthalene (PRODAN) in room‐temperature solutions under various conditions is reported. The results show no unusual photophysical properties, except for an extremely large solvatochromic shift of PRODAN fluorescence spectrum. The previously reported extra blue emission band for PRODAN in an aqueous solution is identified to be due entirely to trace water‐soluble impurities in the sample. The excited‐state dipole moment of PRODAN is determined based on solvatochromic results using a known twisted intramolecular charge transfer (TICT) molecule p‐(N,N‐diethylamino)ethylbenzoate (DEAEB) as a reference to probe specific solute‐solvent interactions. The possibility of TICT state formation in PRODAN is discussed, and a solvation equilibrium mechanism is proposed to account for the photophysical behavior of PRODAN.
AN ANIMAL MODEL AND NEW PHOTOSENSITIZERS FOR PHOTOPHERESIS
Authors: Iperen H. P. Van , Henegouwen G. M. J. Beijersbergen van 
Published: January 2008

AbstractRecently, photopheresis was introduced as a therapy for several T cell‐mediated disorders. The treatment results in a specific immune response against the pathogenic clone of T cells involved. However, although promising there is controversy concerning the use of photopheresis in some diseases, e.g. systemic sclerosis. One of the problems is that there is not yet sufficient insight into the mechanism underlying the therapy. This lack of knowledge is partly caused by the fact that there are no easy‐to‐handle animal models available for photopheresis.This report describes such a model—a Wistar‐derived rat with contact hypersensitivity (CHS); a T cell‐mediated immune response. White blood cells from CHS rats were simultaneously exposed to 8‐methoxypsoralen (8‐MOP) and ultraviolet A radiation (UVA) and subsequently intravenously injected into other syngeneic rats suffering from the same disorder. This treatment appears to be very efficacious in suppressing the immunological response against the applied contact allergen, 2,4‐dinitroAuorobenzene (DNFB). In addition, the generated suppression of CHS is highly specific and transferable. Furthermore, drugs other than 8‐MOP (chlordiazepoxide, nitrofurantoin and chlor‐promazine) also appear to be active in our model.
CYTOKINE RELEASE BY PERIPHERAL BLOOD MONONUCLEAR CELLS IS AFFECTED BY 8‐METHOXYPSORALEN PLUS UV‐A
Authors: Neuner Peter , Charvat Birgit , Knobler Robert , Kirnbauer Reinhard , Schwarz Agatha , Luger Thomas A. , Schwarz Thomas 
Published: January 2008

AbstractPsoralen plus UV‐A (PUVA) is an effective therapy for psoriasis but also for other inflammatory dermatoses. The precise mechanisms of action, however, are not absolutely clear. Therefore, the effect of PUVA on the release of the proinflammatory cytokines interleukin (IL)‐1, IL‐6, IL‐8 and tumor necrosis factor alpha (TNFα) was studied. Peripheral blood mononuclear cells (PBMC) obtained from humans were incubated with 8‐methoxypsoralen (8‐MOP) and exposed to UV‐A (20 kJ/m2). This treatment resulted in a significant reduction of IL‐6 and IL‐8 amounts in the supernatants. In addition, an inhibition of IL‐1β and TNFα production by lipopolysaccharide (LPS)‐stimulated PBMC was observed upon PUVA treatment. Accordingly, northern blot analysis showed decreased levels of mRNA encoding for IL‐1β, IL‐6, IL‐8 and TNFα in PUVA‐treated PBMC. Finally PBMC were obtained from psoriatics undergoing oral photochemotherapy before the beginning and after completion of treatment. The PBMC collected after PUVA spontaneously produced significantly less IL‐6 and IL‐8 in comparison to the respective samples obtained before therapy. A similar suppression of IL‐1β and TNFα by in vivo PUVA was found in LPS‐stimulated PBMC. The present data demonstrate that PUVA both in vitro and in vivo suppresses the production of the proinflammatory cytokines IL‐1β, IL‐6, IL‐8 and TNFα by PBMC. Because these cytokines are important in the mediation of inflammatory reactions, one may speculate that the inhibitory effects could contribute to the antiinflammatory activity of PUVA.
ALKALI‐LABILE PHOTOLESIONS MAPPING TO PURINE SITES IN ULTRAVIOLET‐IRRADIATED DNA
Authors: Hejmadi Vidyasagar , Stevenson Clarke , Kumar Shiv , Davies R. Jeremy H. 
Published: January 2008

AbstractGel sequencing experiments with the 5′‐ and 3′‐end‐labeled oligonucleotides d(A3GA4GA5GA6GA3G) and d(AT) 10 have demonstrated that dimeric adenine photoproducts and thymine‐adenine photoadducts constitute alkali‐labile lesions in UV‐irradiated DNA. On treatment with hot piperidine, DNA strand breakage occurs predominantly at the sites of 5′‐adenines in the dimeric photoproducts and of 3′‐adenines in the thymine‐adenine photoadducts. With 5′‐end‐labeled oligonucleotides of mixed sequence, major UV‐induced loci for alkaline cleavage map to purine bases flanked on their 5′‐side by two pyrimidines. This behavior does not arise from enhanced photoreactivity of purines in this sequence context as has been inferred from photofootprinting studies. Instead, as shown by 3′‐labeling and selective substitution with 5‐methylcytosine, it results from the anomalous electrophoretic mobility of 5′‐end‐labeled fragments produced by alkaline cleavage of DNA at adjacent pyrimidine (6‐4) pyrimidone photoproducts.
SOLVENT EFFECTS ON TRIPLET‐STATE BACTERIOCHLOROPHYLL a AS DETECTED BY TRANSIENT RAMAN SPECTROSCOPY AND THE ENVIRONMENT OF BACTERIOCHLOROPHYLL a IN THE LIGHT‐HARVESTING COMPLEX OF Rhodobacter sphaeroides R26
Authors: Nishizawa Ei‐ichi , Limantara Leenawaty , Nanjou Noriyuki , Nagae Hiroyoshi , Kakuno Tomisaburo , Koyama Yasushi 
Published: January 2008

AbstractThe frequency of BChl that was bound to the light‐harvesting complex (LHC) of Rhodobacter sphaeroides R26 was found to be 1598 cm‐1, a result which suggests that a pair of BChl molecules form a dimer in the LHC in the T1 state.
REACTION AND QUENCHING OF SINGLET MOLECULAR OXYGEN WITH ESTERS OF POLYUNSATURATED FATTY ACIDS
Authors: Tanielian C. , Mechin R. 
Published: January 2008

Abstract The rate constants for the reactive (kR) and unreactive (kQ) interaction of singlet molecular oxygen with three esters of polyunsaturated fatty acids (PUFA: cis‐methyl oleate, MO; cis‐methyl linoleate, MLA and cis‐ethyl linolenate, ELN) are determined. The values of the ratio kQ/kR are 0.51, 0.26 and 0.20 for MO, MLA and ELN, respectively. This variation results principally from that of kR because the values of kQ are only slightly different (1.24 × 104M−1 s−1 for MO and ∼1.0 × 104M−1 s−1 for MLA and ELN). It is shown that the rate constant kQ characterizes mainly an interaction with the unreactive part of the molecule rather than with the double bonds (solventlike quenching).Contrary to the already reported case of 1,5‐polyenes for which kQ <<kR, the present results and those obtained from a number of literature data show that for PUFA and their esters, neither kR+ kQ nor kR are proportional to the total number of double bonds or of methylene groups adjacent to the double bonds. Instead, a linear correlation is observed by plotting kRvs the number of methylene groups adjacent to two double bonds. It is deduced that contrary to a common assumption, biallylic hydrogens have a reactivity higher than that of singly allylic hydrogens (reactivity ratio 1.19).The consequence of this result on the estimation of relative contributions of singlet oxygen and radical mechanisms to oxidation processes is discussed. Moreover, the whole of these results allows prediction of the values of kR and kQ for all unsaturated fatty acids (and their esters) of similar structure.
TUMOR‐LOCALIZING FLUORESCENT DIAGNOSTIC AGENTS WITHOUT PHOTOTOXICITY
Authors: Takemura Takeshi , Nakajima Susumu , Sakata Isao 
Published: January 2008

AbstractIn order to develop tumor‐localizing fluorescent diagnostic agents without phototoxicity, various heterodimers linked by some spacers between a chlorine derivative and its Mn or Cu complex were synthesized. The representative agent of them was named HAT‐D01 and has a molecular formula of m‐phthalyl‐{[13,17‐bispropanoic acid‐3‐ethenyl‐8‐formylethylidene‐7‐hydroxy‐2,7,12,18‐tetramethyl‐porphyrinate]‐manganese (III)}‐[3′‐ethenyl‐8′‐formylethylidene‐7′‐hydroxy‐2′,7′, 12′, 18′‐tetramethyl‐porphine‐13′, 17′‐bispropanoyl aspartic acid]‐bishydrazone.
A FULLY AUTOMATED DUAL‐WAVELENGTH PHOTOMETER FOR PHYTOCHROME MEASUREMENTS AND ITS APPLICATION TO PHYTOCHROME FROM CHLOROPHYLLCONTAINING EXTRACE
Authors: Lamparter Tilman , Hughes Jon , Hartmann Elmar 
Published: January 2008

Abstract The photometer described here measures phytochrome photoreversibility of as many as 20 samples fully automatically. Monochromatic light of two laser diodes (670 and 780 nm) is used as a source for the measuring light beam. The whole measuring procedure is controlled by a computer linked to a lock‐in amplifier. This arrangement permits a rather simple construction and allows automatic zeroing and sample change.In addition the application of a Triton phase partitioning method to allow phytochrome photoreversibility mea surements of extracts of green tissue is described. A single phase partitioning with a chlorophylYphytochrome mixture reduced chlorophyll concentration to less than 10%. Repeated phase partitioning of crude extracts from green moss protonemata reduced chlorophyll content to less than 2% while leaving the phytochrome concentration almost unchanged. In some instances this method has advantages over polyethyleneimine precipitation, which is commonly used to obtain chlorophyll‐free extracts.
PROTEIN STRUCI'URE MODELLING OF THE BACTERIAL LIGHT‐HARVESTING COMPLEX
Authors: Olsen J. D. , Hunter C. N. 
Published: January 2008

Abstract Protein structure modelling offers a method of obtaining 3‐dimensional information that can be tested and used to plan mutagenesis experiments when a crystallographically determined structure is not available. At its simplest a model may consist of little more than a secondary structure prediction coupled with a determination of the likely regions of transmembrane/membrane surface/globular configuration. These methods can yield an interesting topology map of the protein, which places the residues in their likely positions with respect to, for example, the membrane interface. If it is a member of a large family of related proteins then aligned protein sequences can be used to predict the residues that have an important function as these. will be largely conserved in the alignments. Using all these methods a model can be constructed (using for example, the Nicholson Molecular Modelling Kit) to visualize the proposed structure in three dimensions following the premise of good design, that is, avoiding obvious steric clashes, packing of helices in a realistic manner, observing the correct H‐bond lengths, etc. In this latter exercise the review of Chothia (Annu. Rev. Biochem. 53, 537–572, 1984) of the principles of protein structure is particularly helpful as it clearly sets out how proteins pack and their preferred configuration. There is a wealth of information about individual amino acid conformational preferences and observed frequencies of occurrence in known protein structures, which can help decide how the residues in the model can be oriented.In this article we have collated the various protein models of the bacterial light‐harvesting complexes and present our own model, which is a synthesis of the available biophysical data and theoretical predictions, and show its performance in explaining recent results of site‐directed mutants of the LHI and LH2 light‐harvesting complexes of Rhodobacter sphaeroides.
THEORETICAL INVESTIGATION OF EXCIMER AND EXCIPLEX STATES OF URACIL AND HALOGEN DERIVATIVES: EFFECT OF NONPARALLELISM OF BASES
Authors: Pechenaya Vera I. , Danilov Victor I. , Slyusarchuk Oleg N. , Alderfer James L. 
Published: January 2008

AbstractTheoretical modeling of initial steps of the photodimerization mechanism of uracil, 5‐methyl‐and 5‐halogen derivatives was performed. The interaction energy of bases in stacked dimers in the ground and lowest excited states was calculated as a function of the distance between the base planes and of the rotation angles within the perturbation theory for the extended Hückel treatment. The existence of excimer and exciplex region on the potential surface of the excited state was revealed. The excimer (exciplex) geometry has the planes nonparallel with more close contact of the C5‐C6 bonds as compared to the ground state of dimers. The results provide new information useful for understanding the photodimerization mechanism of bases and testifies that the singlet excimer state can be a precursor of the photodimerization reaction.
RETINYLIDENE‐OPSIN SCHIFF BASE CHROMOPHORES AND THEIR ACCESSIBILITY TO WATER
Authors: Haarosi F. I. , Sándorfy C. 
Published: January 2008

AbstractWe propose a conceptual model to form the basis of understanding of the retinylidene‐opsin Schiff base (SB) chromophores. The first suggestion is that the protonated imine is H‐bonded to water, and this complex is similar in H‐bonding to a hydronium ion‐water dimer (H5O5+). The second proposal is a limited accessibility of water to the SB region of the chromophore. We scrutinize data from anion‐sensitive and UV‐absorbing visual pigments and find consistency with expectations based on the model: (1) Hydration plays a fundamental role in the photochemistry. (2) Protonation of the imine nitrogen is not obligatory. The latter point is supported by spectroscopic evidence from UV‐absorbing visual pigments, in which unprotonated SB chromophores are inferred. Further support is derived from thermodynamic analysis of the temperature dependence of protonation in SB models and in a UV‐absorbing visual pigment. We discuss H‐bonding opportunities for retinylidene‐opsin SB: the strong H‐bonds to ions, the weak H‐bonds of C‐H groups, serving as H‐bond donors, and of the π‐bonds, in which π‐electrons act as H‐bond acceptors.