bluuebunny/crossref_metadata_2025_split huggingface dataset:
VISIBLE LIGHT ANAEROBIC PHOTOCONVERSION OF TYROSINE SENSITIZED BY RIBOFLAVIN. CYTOTOXICITY ON MOUSE TUMORAL CELLS
Authors: Silva Eduardo , Fürst Sonia , Edwards Ana M. , Becker M. Ines , Ioannes Alfredo E. De 
Published: July 2010

AbstractThe anaerobic phototransformation of tyrosine under visible light sensitized by riboflavin is reported. The cytotoxicity of the anaerobic photoproducts on in vitro‐cultured myeloid mouse tumoral cells was demonstrated. A radical mechanism is proposed. Dityrosine was identified as one of the main anaerobic photoproducts by using absorption, emission and 1H‐NMR spectra.
THE MOLECULAR CHAPERONE FUNCTION OF α‐CRYSTALLIN IS IMPAIRED BY UV PHOTOLYSIS
Authors: Borkman Raymond F. , McLaughlin Jennifer 
Published: July 2010

AbstractBuffer solutions of the lens protein γ‐crystallin and the enzymes aldolase and liver alcohol dehydrogenase became turbid and formed solid precipitate upon exposure to an elevated temperature of 63°C or to UV radiation at 308 nm. When α‐crystallin was added to the protein solutions in stoichiometric amounts, heat or UV irradiation did not cause turbidity, or turbidity developed much less rapidly than in the absence of α‐crystallin. Hence, normal α‐crystallin functioned as a molecular chaperone, providing protection against both UV and heat‐induced protein aggregation. When α‐crystallin was preirradiated with UV at 308 nm, its ability to function as a chaperone vis‐a‐vis both UV and heat‐induced aggregation was significantly impaired, but only at relatively high UV doses. A major effect of preirradiation of α‐crystallin was to cause interpeptide crosslinking among the αA2 and αB2 subunits of the α‐crystallin macromolecule. In our experiments α‐crystallin was exposed to UV doses, which resulted in 0, 50 and 90% crosslinking as judged by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. α‐Crystallin samples that were 50% and 90% crosslinked gave chaperone protection, which was increasingly impaired relative to unirradiated α‐crystallin. The results are consistent with the notion that UV irradiation of α‐crystallin results in loss of chaperone binding sites.
pH Effects on the Spectroscopic and Photochemical Behavior of Enoxacin: A Steady‐State and Time‐Resolved Study
Authors: Sortino S. , Guidi G. De , Giuffrida S. , Monti S. , Velardita A. 
Published: July 2010

ABSTRACTThe spectroscopic and photochemical behavior of Enoxacin (ENX), 1‐ethyl‐6‐fluoro‐1,4‐dihydro‐4‐oxo‐7‐(1‐piperazinyl)‐1,8‐naphthyridine‐3‐carboxylic acid, has been investigated in aqueous solutions between pH 3.5 and pH 12. The absorption and emission properties of ENX are strongly affected by pH. The fluorescence quantum yield, 4 x 10−3 at pH 3.5, increases by a factor of two on going to neutral pH while a strong reduction is observed at alkaline pH. The photodegradation quantum yield also depends on pH, being maximum in neutral conditions (ca 0.04). Nanosecond flash photolysis experiments confirm that the yield of absorbing transients is maximum at neutral pH while it decreases to zero at acid and alkaline pH. These results indicate that both the dissociation of the carboxylic group and the protonation of the piperazinyl residues are key steps for the formation of the photochemically active form of ENX. Loss of F− by heterolytic cleavage of the C–F bond is proposed to occur from the triplet state of the zwitterion with formation of a carbocation. A path for the evolution of this intermediate to the final product is also proposed.
Porphyrins and Related Compounds as Photoactivatable Insecticides I. Phototoxic Activity of Hematoporphyrin Toward Ceratitis capitata and Bactrocera oleae
Authors: Amor T. Ben , Tronchin M. , Bortolotto L. , Verdiglione R. , Jori G. 
Published: July 2010

ABSTRACTThe photodynamic sensitizer hematoporphyrin (HP) IX was efficiently accumulated by Ceratitis capitata (Mediterranean fruit fly) and Bactrocera oleae (olive fly) when the insects were fed with a sugar/protein bait containing micromolar amounts of porphyrin. Hematoporphyrin appeared to be mainly accumulated in the midgut, Malpighian tubes, adipose tissue and cuticle and was gradually cleared from the organism in a 24–48 h time interval. Exposure of the HP‐fed flies to light mimicking the solar spectrum caused a decrease in the survival whose extent was modulated by the HP concentration in the bait, the irradiation fluence rate and the total light dose. For 8 μmol/mL HP in the bait 100% mortality during 1 h exposure to light was obtained using a fluence rate of 1220 μE s−1 m−2 for C. capitata and 2080 μE s−1 m−2 for B. oleae. The latter fly was somewhat less photosensitive than C. capitata possibly owing to the smaller amount of ingested HP and/or darker pigmentation. Studies are in progress in order to extend these investigations from the laboratory to the field scale.
An Insight into the Mechanisms of the Phototoxic Response Induced by Cyamemazine in Cultured Fibroblasts and Keratinocytes¶
Authors: Morliére Patrice , Haigle Josiane , Aissani Karim , Fillpe Paulo , Silva João Nuno , Santus René 
Published: July 2010

ABSTRACTThe phototoxicity of cyamemazine (CMZ, Tercian®), a neuroleptic of the phenothiazine family, has recently been reported in humans. CMZ has an absorbance maximum at 267 nm (molar absorptivity, 25800 M−1 cm−1) but a weaker molar absorptivity in the ultraviolet A (UV‐A) region. CMZ exhibits a fluorescence with maximum emission at 535 nm and a quantum yield of 0.11. CMZ is a powerful photosensitizing agent toward HS 68 human skin fibroblasts and NCTC 2544 keratinocytes. At a UV‐A radiation dose of 10 J/cm2, innocuous to cells in the absence of CMZ, the LD50 (lethal dose corresponding to 50% killing) are 0.5 and 1 μM for the fibroblasts and the keratinocytes, respectively, after overnight incubation with the drug. Short incubation times do not significantly alter the LD50. The CMZ‐induced phototoxicity is accompanied by lipid membrane peroxidation consistent with the amphiphilic character of this photosensitizer. Keratinocytes are an order of magnitude less sensitive to the photosensitized lipid peroxidation than fibroblasts. Microspectrofluorometry reveals that lysosomal membranes are major sites of CMZ incorporation into the two cell lines because a Forster‐type resonance energy transfer process occurs from CMZ to LysoTracker Red DND99 (LTR), a specific fluorescent probe of lysosomal membranes. The CMZ‐photosensitized destruction of LTR demonstrates that CMZ retains its photosensitizing capacity after its lysosomal uptake.
Epidermal Lignin Deposition in Quinoa Cotyledons in Response to UV‐B Radiation¶
Authors: Hilal Mirna , Parrado María Francisca , Rosa Mariana , Gallardo Miriam , Orce Luis , Massa Eddy Marta , González Juan Antonio , Prado Fernando Eduardo 
Published: July 2010

ABSTRACTUV‐B radiation (280–320 nm) is harmful to living organisms and has detrimental effects on plant growth, development and physiology. In this work we examined some mechanisms involved in plant responses to UV‐B radiation. Seedlings of quinoa (Chenopodium quinoaWilld.) were exposed to variable numbers of UV‐B radiation doses, and the effect on cotyledons was studied. We analyzed (1) cotyledons anatomy and chloroplasts ultrastructure; (2) peroxidase activity involved in the lignification processes; and (3) content of photosynthetic pigments, phenolic compounds and carbohydrates. Exposure to two UV‐B doses induced an increase in the wall thickness of epidermal cells, which was associated with lignin deposition and higher activity of the peroxidase. The chloroplast ultrastructure showed an appearance typical of plants under shade conditions, likely in response to reduced light penetration into the mesophyll cells due to the screening effect of epidermal lignin deposition. Exposure to UV‐B radiation also led to (1) enhancement in the level of phenolics, which may serve a protective function; (2) strong increase in the fructose content, a fact that might be related to higher requirement of erythrose‐4P as a substrate for the synthesis of lignin and phenolics; and (3) reduction in the chlorophyll concentration, evidencing alteration in the photosynthetic system. We propose that the observed lignin deposition in epidermal tissues of quinoa is a resistance mechanism against UV‐B radiation, which allows growing of this species in Andean highlands.
Radiative Relaxation Quantum Yields for Synthetic Eumelanin¶
Authors: Meredith Paul , Riesz Jennifer 
Published: July 2010

ABSTRACTWe report absolute values for the radiative relaxation quantum yield of synthetic eumelanin as a function of excitation energy. These values were determined by correcting for pump beam attenuation and emission reabsorption in both eumelanin samples and fluorescein standards over a large range of concentrations. Our results confirm that eumelanins are capable of dissipating >99.9% of absorbed UV and visible radiation through nonradiative means. Furthermore, we have found that the radiative quantum yield of synthetic eumelanin is excitation energy dependent. This observation is supported by corrected emission spectra, which also show a clear dependence of both peak position and peak width on excitation energy. Our findings indicate that photoluminescence emission in eumelanins is derived from ensembles of small chemically distinct oligomeric units that can be selectively pumped. This hypothesis lends support to the theory that the basic structural unit of eumelanin is oligomeric rather than heteropolymeric.
Decreased Levels of (6–4) Photoproduct Excision Repair in Hybrid Fish of the Genus Xiphophorus¶
Authors: Mitchell David L. , Nairn Rodney S. , Johnston Dennis A. , Byrom Michelle , Kazianis Steven , Walter Ronald B. 
Published: July 2010

ABSTRACTSelected hybridization in the fish genus Xiphophorus has been used for many years to study the genetics of malignant melanoma. Because DNA damage caused by ultraviolet radiation is implicated in the etiology of sunlight‐induced melanoma, the heritability of mechanisms that mitigate DNA damage is a matter of some interest. We examined nucleotide excision repair of the two major types of DNA‐damage induced by sunlight; the cyclobutane pyrimidine dimer (CPD) and the pyrimidine (6–4) pyrimidone dimer [(6–4)PD]. In most cases, removal of the (6–4) PD was more rapid than the CPD, and in many cases, the F1 hybrid showed reduced repair efficiency compared with the parental species. These data demonstrate reduced function in multienzyme hybrid systems and provide molecular support for potential reduced fitness in hybrid fish under conditions of environmental stress.
Biodistribution Assessment of a Lutetium(III) Texaphyrin Analogue in Tumor‐bearing Mice Using NIR Fourier‐transform Raman Spectroscopy¶
Authors: Synytsya Alla , Król Vladimír , Matejka Pavel , Poučkovó Pavla , Volka Karel , Sessier Jonathan L. 
Published: July 2010

ABSTRACTThe use of near‐infrared (NIR)‐excited Fourier‐transform (FT) Raman spectroscopy as a technique for evaluating the extent of photosensitizer localization in tumor (human pancreatic adenocarcinomas)‐bearing mice has been tested using lutetium(III) texaphyrin analogue Ln‐T2B2Tex. The complex was injected subcutaneously in the form of three injections given during the course of 3 days. The kinetics of biodistribution were then followed over a time scale of 1–6 days. The NIR‐FT‐Raman spectra of tissue samples obtained from the xenographic tumor, muscle, heart, brain, liver, spleen, kidney and blood were recorded and used to identify the presence of Lu‐T2B2Tex in these tissues. Five Raman sensitizer markers were used to estimate the relative content of Lu‐T2B2Tex in tumor at various postinjection times. UV‐Visible (Vis) absorption spectroscopic detection of this sensitizer in tissue extracts was applied as a conventional method. Both spectroscopic methods were in good agreement with each other and confirm that Lu‐T2B2Tex localizes well in tumor tissue. Maximal drug content was observed 3 days after the final injection. This time delay seems to be optimal for tumor irradiation in photodynamic therapy.
Torsion Potential Works in Rhodopsin¶
Authors: Yamada Atsushi , Yamato Takahisa , Kakitani Toshiaki , Yamamoto Shigeyoshi 
Published: July 2010

ABSTRACTWe investigate the role of protein environment of rhodopsin and the intramolecular interaction of the chromophore in the cis‐trans photoisomerization of rhodopsin by means of a newly developed theoretical method. We theoretically produce modified rhodopsins in which a force field of arbitrarily chosen part of the chromophore or the binding pocket of rhodopsin is altered. We compare the equilibrium conformation of the chromophore and the energy stored in the chromophore of modified rhodopsins with those of native rhodopsins. This method is called site‐specific force field switch (SFS). We show that this method is most successfully applied to the torsion potential of rhodopsin. Namely, by reducing the twisting force constant of the C11=C12 of 11‐cis retinal chromophore of rhodopsin to zero, we found that the equilibrium value of the twisting angle of the C11=C12 bond is twisted in the negative direction down to about −80°. The relaxation energy obtained by this change amounts to an order of 10 kcal/mol. In the case that the twisting force constant of the other double bond is reduced to zero, no such large twisting of the bond happens. From these results we conclude that a certain torsion potential is applied specifically to the C11=C12 bond of the chromophore in the ground state of rhodopsin. This torsion potential facilitates the bond‐specific cis‐trans photoisomerization of rhodopsin. This kind of the mechanism is consistent with our torsion model proposed by us more than a quarter of century ago. The origin of the torsion potential is analyzed in detail on the basis of the chromophore structure and protein conformation, by applying the SFS method extensively.
Spatial Control of Reactive Oxygen Species Formation in Fibroblasts Using Two‐photon Excitation¶
Authors: King Brett A. , Oh Dennis H. 
Published: July 2010

ABSTRACTTwo‐photon excitation (2PE) provides a means of generating reactive oxygen species (ROS) in cells and tissues with a high degree of spatial specificity. In cultured monolayers of human fibroblasts and fibroblast‐derived cells treated with the commonly used probe of ROS formation, 5‐(and 6)‐chloromethyl‐2′,7′‐dichlorodihydrofluorescein diacetate, acetyl ester (CM‐H2DCFDA), cells irradiated through a microscope objective with 150 fs near‐infrared laser pulses became highly fluorescent, reflecting intracellular ROS formation. The fluorescence intensity inside cells increased quadratically with the average power of radiation for pulsed excitation and was unchanged for continuous wave irradiation with the same average power of radiation for pulsed excitation and was unchanged for continuous wave irradiation with the same average power. Single fibroblasts embedded within dermal equivalents were also targeted in this manner and formed ROS, whereas neighboring unirradiated cells were spared. These results demonstrate that ROS can be generated intracellularly in skin cells using 2PE of the metabolic or oxidative products of CM‐H2DCFDA and that formation of ROS can be localized in both cell monolayers and in a tissue equivalent. This technique should be useful in understanding the response of whole tissues such as skin to local generation of ROS and may have applications in photodynamic therapy.
Riboflavin and UV‐Light Based Pathogen Reduction: Extent and Consequence of DNA Damage at the Molecular Level
Authors: Kumar Vijay , Lockerble Owen , Kell Shawn D. , Ruane Patrick H. , Platz Matthew S. , Martin Christopher B. , Ravanat Jean‐Luc , Cadet Jean , Goodrich Raymond P. 
Published: July 2010

ABSTRACTWe are developing a technology based on the combined application of riboflavin (RB) and light for inactivating pathogens in blood products while retaining the biological functions of the treated cells and proteins. Virus and bacteria reduction measured by tissue culture infectivity or colony formation with UV light alone and in combination with RB yield equivalent results. The effects of RB as a sensitizing agent on DNA in white cells, bacteria and viruses in combination with UV light exposure have been evaluated. UV‐mediated DNA degradation in Jurkat T cells and leukocytes in plasma as measured by the FlowTACS assay was significantly increased in the presence of RB. Agarose gel electrophoretic analysis of DNA in Escherichia coli and leukocytes in plasma demonstrated enhanced DNA degradation in the presence of RB. UV light in combination with RB prevented the reactivation of lambda phage compared with samples irradiated in the absence of RB. UV‐mediated oxidative damage in calf thymus DNA was also enhanced in the presence of RB. These observations clearly demonstrate that the presence of RB and UV light selectively enhances damage to the guanine bases in DNA. These data also suggest that the type and extent of damage to DNA for virus in the presence of RB and light make it less likely to be repaired by normal repair pathways available in host cells.
Effects of Suplementary Ultraviolet‐B Irradiance on Maize Yield and Qualities: A Field Experiment¶
Authors: Gao Wei , Zheng Youfei , Slusser James R. , Heisler Gordon M. , Grant Richard H. , Xu Jianqiang , He Douliang 
Published: July 2010

ABSTRACTStratospheric ozone depletion has caused an increase in the amount of ultraviolet‐B (UV‐B) radiation reaching the earth's surface. Numerous investigations have demonstrated that the effect of UV‐B enhancements on plants includes reduction in grain yield, alteration in species competition, susceptibility to disease and changes in plant structure and pigmentation. Many experiments examining UV‐B radiation effects on plants have been conducted in growth chambers or greenhouses. It has been questioned whether the effect of UV‐B radiation on plants can be extrapolated to field responses from indoor studies because of the unnaturally high ratios of UV‐B/ ultraviolet‐A radiation (320–400 nm) and UV‐B/photosynthetically active radiation (PAR) in many indoor studies. Field studies on UV‐B radiation effect on plants have been recommended to use the UV and PAR irradiance provided by natural light. This study reports the growth and yield responses of a maize crop exposed to enhanced UV‐B radiation and the UV‐B effects on aize seed qualities under field conditions. Enhanced UV‐B radiation caused a significant reduction in the dry matter accumulation and the maize yield in turn was affected. With increased UV‐B radiation the flavonoid accumulation in maize leaves increased and the contents of chlorophyll a, b and (a+b) of maize leaves were reduced. The levels of protein, sugar and starch of maize seed decreased with enhanced UV‐B radiation, whereas the level of lysine increased with enhanced UV‐B radiation.
Tryptophan Fluorescence in the Bacillus subtilis Phototropin‐related Protein YtvA as a Marker of Interdomain Interaction¶
Authors: Losi Aba , Ternelli Elena , Gärtner Wolfgang 
Published: July 2010

ABSTRACTThe Bacillus subtilis protein YtvA, related to plant phototropins (phot), binds flavin mononucleotide (FMN) within the N‐terminal light, oxygen and voltage (LOV) domain. The blue light‐triggered photocycle of YtvA and phot involves the reversible formation of a covalent photoadduct between FMN and a cysteine (cys) residue. YtvA contains a single tryptophan, W103, localized on the LOV domain and conserved in all phot‐LOV domains. In this study, we show that the fluorescence parameters of W103 in YtvA‐LOV are markedly different from those observed in the full‐length YtvA. The fluorescence quantum yields are ca 0.03 and 0.08, respectively. In YtvA‐LOV, the maximum is redshifted (ca 345 vs 335 nm) and the average fluorescence lifetime shorter (2.7 vs 4.7 ns). These data indicate that W103 is located in a site of tight contact between the two domains of YtvA. In the FMN‐cys adduct, selective excitation of W103 at 295 nm results in minimal changes of the fluorescence parameters with respect to the dark state. On 280 nm excitation, however, there is a detectable decrease in the fluorescence emitted from tyrosines, with concomitant increase in W103 fluorescence. This effect is reversible in the dark and might arise from a light‐regulated energy transfer process from a yet unidentified tyrosine to W103.
Simultaneous Production of Superoxide Radical and Singlet Oxygen by Sulphonated Chloroaluminum Phthalocyanine Incorporated in Human Low‐density Lipoproteins: Implications for Photodynamic Therapy¶
Authors: Martins Joana , Almeida Leonor , Laranjinha João 
Published: July 2010

ABSTRACTSulfonated chloroaluminum phthalocyanines have been studied for their use in the photodynamic therapy (PDT) of tumors. Plasma low‐density lipoproteins (LDL) are important carriers of phthalocyanines in the blood, but on exposure to visible light, phthalocyanine‐loaded LDL undergo an oxidation process that propagates to erythrocytes. We attempted to identify the reactive species involved in LDL and erythrocyte oxidation by means of electron paramagnetic resonance (EPR) spectroscopy in the presence of 2,2,6,6‐tetramethyl‐4‐piperidone (TEMP) and the spin trap 5,5′‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO). Irradiation of phthalocyanine‐loaded LDL in the presence of DMPO resulted in the formation of a four‐line EPR spectrum with relative intensity of 1:2:2:1 (aN= aH= 14.8 G), characteristic of DMPO‐hydroxyl radical spin adduct. This signal was sensitive to superoxide dismutase and slightly sensitive to catalase, but a mixture of the two enzymatic activities was the most efficient in promoting a decrease in the intensity of the EPR signal. In the presence of erythrocytes, an increase in the quartet intensity for a hematocrit of 1% and 4% was observed, decreasing for higher erythrocyte concentrations. The irradiation of phthalocyanine‐loaded LDL in the presence of TEMP resulted in the formation of a nitroxide radical, 2,2,6,6‐tetramethyl‐4‐piperidone‐N‐oxyl radical, intensity of which was sensitive to histidine, a singlet oxygen (1O2) quencher. Under both incubation conditions, with DMPO and TEMP, the formation of the respective EPR signals required the sensitizer (phthalocyanine), light and oxygen. Overall, the results are compatible with the simultaneous formation of superoxide anion and1O2, implying that Type‐I and Type‐II mechanisms of photochemistry are simultaneously operative in phthalocyanine‐loaded LDL. However, for a constant LDL/phthalocyanine ratio, the formation of oxygen free radicals shows a biphasic behavior with the concentration of LDL increasing and reaching a plateau, whereas the formation of1O2increases linearly with LDL concentration. Erythrocytes at high (physiological) concentrations induced a decrease in the intensity of both EPR signals. The physiological relevance of these findings in the framework of PDT is briefly discussed.