bluuebunny/crossref_metadata_2025_split huggingface dataset:
USE OF SENSITIZED FLUORESCENCE FOR THE STUDY OF THE EXCHANGE OF SUBUNITS IN PROTEIN AGGREGATES*
Authors: Erijman Leonardo , Weber Gregorio 
Published: January 2008

AbstractThe exchange of subunits between oligomer protein particles depends upon a cycle of dissociations and associations. To examine the dynamics of these cycles we have employed two methods based on the transfer of excitation energy between fluorochromes attached to different subunits of protein oligomers, at various temperatures and pressures. In the heterotransfer method, identical solutions independently labeled with two different fluorophores, donor D and acceptor A, are mixed. The fluorescence spectrum permits the determination of the subunit exchange by the increase in A and decrease in D fluorescence as mixed AD oligomers are formed. In the homotransfer method the aggregates are labeled with fluorescein to the extent that, ideally, each subunit carries a fluorophore. The emission is strongly depolarized because sufficiently often it takes place after a transfer to a fluorophore oriented differently from the one originally excited. Both dissociation and subunit exchange with unlabeled material result in an increase in polarization and can be independently determined by the homotransfer method. Both homo‐ and heterotransfer have been employed in the study of the effect of temperature on the stability of the aggregates and the relation between the rate of dissociation and the rate of exchange when dissociation of oligomers is induced by hydrostatic pressure.
DETECTION OF RADICAL ION INTERMEDIATES IN FLAVIN‐PHOTOSENSITIZED PYRIMIDINE DIMER SPLITTING
Authors: Heelis Paul F. , Hartman Rosemarie F. , Rose Seth D. 
Published: January 2008

AbstractPhotosensitized splitting of cis‐syn‐ and trans‐syn‐l,3‐dimethyluracil dimers by 2′,3′,4′,5′‐tetraacetylri‐boflavin in acetonitrile containing a trace of perchloric acid was studied by laser flash photolysis. Protonation of the flavin prior to excitation resulted in excited singlet and triplet states that abstracted an electron from the dimers and yielded the protonated flavin radical (F1H2′+), which was detected by absorption spectroscopy. Electron abstraction by the excited singlet state predominated over abstraction by the triplet state. Approximately one‐third to one‐half of the excited states quenched by the trans‐syn dimer yielded F1H2+, the balance presumably undergoing back electron transfer within the geminate radical ion pair generated by the initial electron transfer. A covalently linked dimer‐flavin exhibited very inefficient flavin radical ion formation, consistent with the known low efficiency of dimer splitting in this system. These results constitute the first identification of a flavin radical ion intermediate in photosensitized pyrimidine dimer splitting.
DRAMATIC IMPROVEMENTS IN VIRAL INACTIVATION WITH BROMINATED PSORALENS, NAPHTHALENES AND ANTHRACENES
Authors: Rai Saroj , Kasturi Chandrika , Grayzar Jennifer , Platz Matthew S. , Goodrich Raymond P. , Yerram Nagender R. , Wong Victoria , Tay‐Goodrich Boon H. 
Published: January 2008

AbstractAmino or polyamino derivatives of naphthalene (N‐H), anthracene (A‐H) and 8‐alkoxypsoralen (PSR‐H) were prepared along with their monobrominatcd analogs (N‐Br, A‐Br and PSR‐Br). The ammonium salts of these compounds are all water soluble and bind strongly to calf thymus DNA and to λ phage, a double‐helical DNA, protein‐coated virus. Binding of the sensitizer to DNA occurs, presumably by a mixture of hydrophobic, intercalative and electrostatic interactions. Relative binding constants to calf thymus DNA and to λ phage were measured by the cthidium bromide fluorescence quenching assay. In general the brominated analogs bind more tightly to calf thymus DNA and to the virus than to the nonhalogenated analogs. It is demonstrated that the brominated aromatics are much more effective at inactivating λ phage upon photoactivation (λ 310 or 350 nm) than are their nonbrominated analogs. At identical sensitizer concentrations (by weight) and light flux N‐Br, A‐Br, and PSR‐Br produce 5–6 more logs of viral inactivation than their nonbrominated counterparts (N‐H, A‐H and PSR‐H, respectively). The bromine effect may originate from light‐induced electron transfer and subsequent cleavage of the C‐Br bond of the sensitizer radical anion bonds to form aryl radicals. Singlet oxygen cannot be responsible for the viral inactivation because the brominated sensitizers are equally effective in the presence and absence of oxygen. Dithiothreitol does not protect λ phage from light‐induced inactivation by the brominated sensitizer thereby demonstrating that the photogenerated reactive intermediates responsible for the effect are complcxed to the virus and are not generated free in solution.
IMINIUM SALT OF COPPER BENZOCHLORIN (CDS1), A NOVEL PHOTOSENSITIZER FOR PHOTODYNAMIC THERAPY: MECHANISM OF CELL KILLING
Authors: Hampton James A. , Skalkos Dimitris , Taylor Paula M. , Selman Steven H. 
Published: January 2008

AbstractThe mechanism of cell killing by CDS1, an iminium salt of octaethylbenzochlorin with copper in the aromatic ring, in combination with light from a noncoherent light source was investigated. Using a standard clonogenic assay and the AY‐27 FANFT turnor line. photoactivation of CDS1 was shown to be cytotoxic. The photodynamic cell killing ability of CDS1 required the presence of molecular oxygen. The reactive species generated by light activation of CDS1 were effectively quenched by N.N'‐diphenyl‐p‐phenylenediamine. Additionally, the photodynamic effect of CDS1 was not cnhanced by dcuterium oxide. To characterize the reactive oxygen species generated by the photoactivation of CDS1 the well‐characterized erythrocyte ghost model was used. Superoxide dismutase and catalase were potcnt inhibitors of CDS1‐induced lipid peroxidation of erythrocyte membranes. Sodium azide only partially inhibited lipid peroxidation. These findings differed from the known singlet oxygen generator, tin (II) etiopurpurin dichloride (SnET2). Sodium azide was a potent inhibitor of SnET2‐induced lipid peroxidation, whereas superoxide dismutase and catalase were totally ineffective. Based on these results, we conclude that CDS1 requires the presence of molecular oxygen for cell killing to occur but appcars to act primarily through a non‐singlet oxygen mechanism.
PHOTODEGRADATION AND in vitro PHOTOTOXICITY OF FENOFIBRATE, A PHOTOSENSITIZING ANTI‐HYPEIUIPOPROTEINEMIC DRUG
Authors: Vargas Franklin , Canudas Nleves , Miranda Miguel A. , Boscar Francisco 
Published: January 2008

AbstractThe phototoxic anti‐hyperlipoproteinemic drug fenofibrate was found to be photolabile under aerobic and anaerobic conditions. Irradiation under argon of a methanol solution of this drug produced the photoproducts isopropyl 4‐(1‐[4‐chlorophenyl]‐1,2‐dihydroxy)ethylphenoxyisobutyrate, 1,2‐bis(4‐chlorophenyl)‐1,2‐bis(4‐[isopro‐poxycarbonylisopropoxy]phenyl)ethane‐1,2‐diol and 4‐(4‐chlorobenzoyl)phenol, while under oxygen the photoproducts were 4‐chloroperbenzoic acid, methyl 4‐chlorobenzoate, 4‐chlorobenzoic acid and singlet oxygen, as evidenced by trapping with 2,5‐dimethylfuran. These results can be rationalized through hydrogen abstraction by excited fenofibrate, to afford a free radical as key intermediate. Biologically active antioxidants such as glutathione and cysteine efficiently reduced 4‐chloroperbenzoic acid to 4‐chlorobenzoic acid. The involvement of an electron transfer mechanism is suggested by detection (UV‐vis spectrophotometry) of the radical cation TMP+ during the oxidation of tetramethylphenylenediamine (TMP) with 4‐chloroperbenzoic acid. Fenofibrate was phototoxic in vitro when examined by the photohemolysis test, both under oxygen and argon atmosphere, although the photohemolysis rate was markedly lower under anaerobic conditions. The photoproducts 4‐(1‐[4‐chlorophenyl]‐1,2‐dihy‐droxy)ethylphenoxyisobutyrate and 4‐chloroperbenzoic acid induced hemolysis in the dark however, this effect was quantitatively less important than photohemolysis by fenofibrate. On the other hand, fenofibrate photosensitized peroxidation of linoleic acid, monitored by the UV detection of dienic hydroperoxides. Based on the inhibition of this process upon addition of butylated hydroxyanisole, a radical chain (type I) mechanism appears to operate. In summary, fenofibrate is phototoxic in vitro. This behavior can be explained through the involvement of free radicals, singlet oxygen and stable photoproducts.
PRIMARY DNA DAMAGE, HPRT MUTATION AND CELL INACTIVATION PHOTOINDUCED WITH VARIOUS SENSITIZERS IN V79 CELLS
Authors: Noodt Barbara B. , Kvam Egil , Steen Harald B. , Moan Johan 
Published: January 2008

AbstractDNA strand breaks and hypoxanthine guanine phosphoribosyl transferase (HPRT) mutants were measured in parallel in photochemically treated (PCT) cells and compared at the same level of cell survival. Chinese hamster fibroblasts (V79 cells) were either incubated with the lipophilic dyes tetra(3—hydroxyphenyl)porphyrin (3THPP) and Photofrin II (PII), the anionic dye meso‐tetra(4—sulfonatophenyl)porphine (TPPS4) or the cationic dye meso‐tetra(N‐methyl‐4‐pyridyl)porphine (p‐TMPyPH2 before light exposure. In the cells, the lipophilic dyes were localized in membranes, including the nuclear membrane, while the hydrophilic dyes were taken up primarily into spots in the cytoplasm. In addition, the hydrophilic TPPS4 was distributed homogeneously throughout the whole cytoplasm and nucleoplasm. According to the HPRT mutation test, the mutagenicity of light doses survived by 10% of the cells was a factor of six higher in the presence of 3THPP than of PII, whereas for X‐rays it was a factor of three higher than for PCT with 3THPP. Light exposure in the presence of the hydrophilic dyes TPPS4 and p‐TMPyPH2 was not significantly mutagenic. There was no correlation between the induced rates of HPRT mutants and of DNA strand breaks. Thus, TPPS4 was the most efficient sensitizer with regard to DNA strand breaks when compared at the same level of cell survival, followed by 3THPP, PII and p‐TMPyPH2. Hence, the rate of DNA strand breaks cannot be used to predict the mutagenicity of PCT.
ANALYZING THE RED‐SHIFT CHARACTERISTICS OF AZULENIC, NAPHTHYL, OTHER RING‐FUSED AND RETINYL PIGMENT ANALOGS OF BACTERIORHODOPSIN*
Authors: Liu R. S. H. , Krogh Erik , Li Xiao‐Yuan , Mead Dennis , Colmenares L. U. , Thiel J. R. , Ellis Jeannette , Wong Darren , Asato A. E. 
Published: January 2008

AbstractPrompted by the near infrared‐absorbing properties of some of the azulenic bacteriorhodopsin (bR) analogs, we have analyzed their absorption characteristics along with 11 new related ring‐fused analogs and the corresponding Schiff bases (SB) and protonated Schiff bases (PSB). The following three factors are believed to contribute to the total red shift of each of the pigment analogs (αRS): perturbation of the basic chromophore (SB shift, ΔSB), protonation of the SB (PSB shift, PSBS) and protein perturbation (the opsin shift, OS). For each factor, effects of structural modifications were examined. For the red‐shifted pigments, percent OS has been suggested as an alternate way of measuring protein perturbation. Computer‐simulated chromophores provided evidence against any explanation involving altered shapes of the binding pocket as a major cause for absorption differences. Implications of the current bR results on preparation of further red‐shifted bR and possible application to visual pigment analogs are discussed.
SPECTROSCOPIC CHARACTERIZATION OF TWO FORMS OF THE D1‐D2‐CYTOCHROME b559 COMPLEX FROM SUGAR BEET
Authors: Montoya Guillermo , Cases Rafael , Yruela Inmaculada , Picorel Rafael 
Published: January 2008

AbstractTwo D1‐D2‐cytochrome b559 complex forms, called RCIIa and RCIIb, with different pigment stoichi‐ometry were characterized using absorption and surface‐enhanced resonance Raman scattering spectroscopy and spectral gaussian deconvolution. Electronic absorption spectra of the RCIIb at 277 K showed significant differences compared to RCIIa, i.e. a strong decrease in the absorbance due to carotenoid and chlorophyll for the same amount of pheophytin. A reduced carotenoid and chlorophyll content in RCIIb was also observed in the surface‐enhanced resonance Raman scattering spectra. Spectral deconvolution elicited three main absorption bands at 680, 672 and 669–670 nm, which were ascribed to P680, pheophytin and accessory chlorophyll, respectively. In addition, a minor component around 667 nm was observed in the RCIIb, most probably due to some reaction center inactivation. Calculation of the relative area under the gaussians together with pigment stoichiometry data suggest that the 680, 672 and 669–670 nm components contain, respectively, two chlorophylls, two pheophytins and four chlorophylls for the RCIIa, and two chlorophylls, two pheophytins and two chlorophylls for the RCIIb.
DETERMINATION OF RESIDUAL 4‐AMINOMETHYL‐4,5‘,8‐TRIMETHYLPSORALENAND MUTAGENICITY TESTING FOLLOWING PSORALEN PLUS UVA TREATMENT OF PLATELET SUSPENSIONS
Authors: Wagner Stephen J. , White Randy , Wolf Ludwig , Chapman John , Robinette Daniel , Lawlor Timothy E. , Dodd Roger Y. 
Published: January 2008

Abstract— Psoralens and UVA light have been used in the laboratory to study the inactivation of viruses that may be infrequently present in platelet concentrates that are prepared for transfusion. In order to evaluate safety aspects of the treatment of platelet suspensions with 4'‐aminomethyl‐4,5',8‐trimethylpsoralen (AMT), we have investigated the residual levels and mutagenic potential of AMT after UVA phototreatment. 4'‐aminomethyl‐4,5',8‐trimethylpso‐ralen, at a final concentration of 40 μg/mL, was added to platelet suspensions which contained 16% plasma and a synthetic medium. Platelet suspensions containing AMT were irradiated with up to 7.2 J/cm2 UVA light under normal oxygen levels. Residual levels of AMT were determined by HPLC and a bioassay based on bacteriophage 0.6 inactivation. The photodestruction of AMT or its activity by UVA was characterized by a D37 value of 0.6 and 0.3 J/cm2 with HPLC or bioassay, respectively. At 2.4 J/cm2 UVA, which results in approximately 5 log10 inactivation of vesicular stomatitis virus (VSV) and retention of platelet in vitro properties, 12% (HPLC) to 9% (bioassay) AMT remained.Like other psoralens, AMT was found to bind to serum proteins as shown by ultrafiltration. Results are consistent with approximately 36% of the initial drug load binding primarily to serum albumin. It was determined using 3H‐AMT that 9 to 18% of radioactivity was bound to platelets in the absence of irradiation. Similar fractions (13 to 18%) of AMT were bound to platelets after 3.6 J/cm2 UVA irradiation, and 8 to 10% of total AMT was associated with saline‐washed irradiated platelets and is presumably tightly bound.Mutagenicity testing (Ames test, in the absence of UVA) was also carried out on the UVA irradiated platelet samples. With Salmonella tester strains which detect primarily base substitution mutations (TA100, TA1535 and TA102), no increase from background mutagenesis levels was observed with any of the samples. However, tester strains which detect frameshift mutations (TA98, TA1537, and TA1538) displayed significant increases in histidine revertants over background levels for irradiated and non‐irradiated AMT‐containing samples tested in the presence of S9 microsomal enzymes. In the absence of S9 activation, a mutagenic response was observed only with tester strain TA1537. All frameshift tester strains exhibited decreased numbers of induced revertants with lower residual AMT concentrations (which correlated with higher UVA dose). Significant mutagenesis was still observed for platelet suspensions irradiated with virucidal levels of UVA which maintain platelet in vitro function (2.4 J/cm2). These results suggest that residual available AMT is mutagenic in the Ames test and that the observed frameshift mutations may be caused by binding of AMT or its metabolites to nucleic acids in the absence of UVA light.
THE EFFECT OF LASER IRRADIATION ON THE RELEASE OF bFGF FROM 3T3 FIBROBLASTS
Authors: Yu Wei , Naim John O. , Lanzafame Raymond J. 
Published: January 2008

AbstractStudies have shown that low‐level laser irradiation increases the proliferation of fibroblasts in cell culture. The mechanism of action is unknown. Basic fibroblast growth factor (bFGF) is a multifunctional polypeptide that has been detected in most tissues and which supports cell proliferation and differentiation. The purpose of this study was to determine whether laser irradiation (660 nm) can stimulate production of bFGF from fibroblast cells in cell culture. Our study showed that fibroblasts irradiated with laser energy at 2.16 J/cm2 demonstrated increased cell proliferation and enhanced production of bFGF, whereas fibroblasts irradiated with laser energy at 3.24 J/cm2 neither demonstrated increased cell proliferation or an enhanced release of bFGF as compared to the control group. These results provide direct evidence that the proliferation of fibroblasts as a result of stimulation by low level laser irradiation may be associated with the autocrine production of bFGF from fibroblasts.
IMINIUM SALT BENZOCHLORINS: STRUCTURE‐ACTIVITY RELATIONSHIP STUDIES
Authors: Skalkos Dimitris , Hampton James A. , Keck Rick W. , Wagoner Miriam , Selman Steven H. 
Published: January 2008

AbstractAn iminium salt of copper(II) octaethylbenzochlorin (CDS1) is an effective new photosensitizer despite the fact that it does not produce singlet oxygen, does not fluoresce and the triplet state lifetime can only be less than 20 ns. A number of octaethylbenzochlorin derivatives were synthesized in order to determine the structural component(s) that is(are) responsible for the photodynamic action of these new photosensitizers. Studies utilizing the N‐(4‐[5‐nitro‐2‐furyl]‐2‐thiazolyl)formamide‐induced urothelial tumor revealed that the coexistence of the copper inside the aromatic ring and the iminium group at the meso position are required for the photodynamic effect.
PHOTOSENSITIZED INACTTVATION OF INFECTIOUS DNA BY UROCANIC ACID, INDOLEACRYLIC ACID AND RHODIUM COMPLEXES
Authors: Mohammad Taj , Tessman Irwin , Morrison Harry , Kennedy Matthew A. , Simmonds Stephen W. 
Published: January 2008

AbstractNaked, infectious single‐stranded (ss) and double‐stranded (ds) DNA from phages SI3 and G4 were irradiated with 308 nm UV radiation in the absence and presence of several photobiologically active compounds: E‐ and Z‐urocanic acid (E‐ and Z‐UA), their methyl esters (E‐ and Z‐MU), E‐ and Z‐indoleacrylic acid (E‐ and Z‐IA), cis‐dichlorobis(1,10‐phenanthroline)rhodium(III) chloride (cDCBPR) and tris(1,10‐phenanthroline)rhodium (III) perchlorate (TPR). E‐urocanic acid protects against cyclobutane pyrimidine dimer formation in ssDNA but concomitantly photosensitizes the formation of other lesions that inactivate ssDNA. Z‐urocanic acid also protects ssDNA against such dimerization but without the associated sensitized damage. The methyl ester isomers behave similarly. There is no such differential activity observed for the IA isomers, both of which sensitize the inactivation of ssDNA. Photostationary state mixtures of both UA and IA efficiently sensitize the inactivation of dsDNA, and cDCBPR strongly protects ssDNA from UV damage, while TPR is a significant sensitizer. Both of these metal complexes sensitize the inactivation of dsDNA slightly. For all compounds, cyclobutane pyrimidine dimers were the predominant lethal lesions produced by sensitization of the dsDNA, but they were not the major lethal lesions created by sensitization of the ssDNA. In the case of dsDNA, both UA and IA created pyrimidine dimers with a high degree of potential for mutagenesis, as determined by an assay that monitors the frequency of mutations following the spontaneous deamination of cytosine in photodimers.
4′,5′‐SUBSTITUTED METHYLANGELICINS: PHOTOCYCLOADDUCTS WITH PYRIMIDINE BASES OF DNA
Authors: Miolo Giorgia , Lucchini Vittorio , Rodighiero Paolo , Dall'Acqua Francesco , Caffieril Sergio 
Published: January 2008

AbstractThe isolation and characterization of photocycloadducts with pyrimidine bases from DNA samples irradiated (365 nm) in the presence of four 4′,5′‐substituted methylangelicins was performed. All these furocoumarins yielded mainly the cis‐syn furan‐side cycloadduct with thymine. For 4′,5′‐dimethyl‐, 5,4′,5′‐trimethyl‐ and 6,4′,5′‐trimethylangelicin this adduct was accompanied by two pyrone‐side adducts (cis‐syn and cis‐anti), whereas the 4,4′,5′‐trimethyl derivative gave the furan‐side adduct with cytosine.The characterization of the regio‐ and stereochemistry of the adducts was accomplished by 1H NOE (nuclear Overhauser effect) and 1H‐13C HMBC (heteronuclear multiple‐bond connectivity) spectroscopies.The formation of different cycloadducts in DNA by the various derivatives highlights the role of the methyl groups in determining the regio‐ and stereochemistry of the cycloaddition.
ANALYSIS OF LASER‐INDUCED FLUORESCENCE LINE SHAPE OF INTACT LEAVES: APPLICATION TO UV STRESS DETECTION
Authors: Subhash N. , Azzinghi Piero M , Agati Giovanni , Fusi Franco , Lercari Bartolomeo 
Published: January 2008

Abstract— In vivo laser‐induced fluorescence spectra of intact leaves of healthy and UV‐irradiated Salvia splendens plants excited at 337 nm by a nitrogen laser were recorded using an optical multichannel analyzer system. The spectra showed the typical fluorescence bands centered around 450, 530, 685 and 730 nm. Exposure to UV radiation changed the relative intensity values of these bands and their peak positions. The analysis of the acquired spectra in terms of a linear combination of Gaussian bands was carried out to determine accurately the peak positions and the relative intensity contribution of the various bands to the laser‐induced fluorescence spectra on healthy and UV‐treated plants of different age.The results indicate that a curve‐fitting analysis of the measured fluorescence spectra is a useful and sensitive method to discriminate the various band contribution to the whole leaf fluorescence spectrum. The comparison among blue‐green and red‐far‐red fluorescence of leaves was also confirmed as an effective indicator of UV stress in plants.
Excited States and Charge Separation in Membranes of the Green Sulfur Bacterium Prosthecochloris aestuarii
Authors: Kramer Hans , Aartsma Thijs J. , Amesz Jan 
Published: January 2008

AbstractTime‐resolved absorbance changes were measured in isolated membranes, depleted of chlorosomes, and in the Fenna‐Matthews‐Olson (FMO) complex of the green sulfur bacterium Prosthecochloris aestuarri. The isolated FMO complex showed a biphasic decay of excited bacteriochlorophyll a (BChl a) with time constants of about 80 and 1400 ps. Approximately the same time constants were observed upon excitation of isolated membranes together with a component of about 30 ps. It is concluded that the efficiency of energy transfer from the FMO to the core complex is very low, in agreement with earlier measurements of the efficiency of charge separation. The 30 ps decay component is ascribed to trapping of the excitation energy from the core BChl a by the reaction center.