bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractHuman 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

AbstractThe 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

AbstractThe 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.
THE USE OF INTERNALIZABLE DERIVATIVES OF CHLORIN E6 FOR INCREASING ITS PHOTOSENSITIZING ACTIVITY
Authors: Akhlynina Tamara V. , Rosenkranz Andrey A. , Jans David A. , Gulak Pavel V. , Sererryakova Natalia V. , Sobolev Alexander S. 
Published: January 2008

AbstractExperiments with human hepatoma PLC/PRF/5 cells and human embryo skin fibroblasts involving the use of three different tests (colony formation, Trypan blue exclusion, labeled thymidine incorporation) have demonstrated a significantly higher photosensitizing activity of chlorin e6 conjugates with internalizable ligands as compared to that of chlorin e6 itself. Receptor‐mediated internalization of chlorin e6 conjugates ensures a greater photosensitization of cells than binding of those conjugates to cell surface receptors. The suitability of such conjugates that permit the delivery of a photosensitizer to sensitive intracellular targets is discussed.
THE SUSCEPTIBILITY OF MUNG BEAN CHLOROPLASTS TO PHOTOINHIBITION IS INCREASED BY AN EXCESS SUPPLY OF IRON TO PLANTS: A PHOTOBIOLOGICAL ASPECT OF IRON TOXICITY IN PLANT LEAVES
Authors: Kim Chang Sook , Jung Jin 
Published: January 2008

AbstractIn an attempt to elucidate the underlying mechanisms for iron toxicity in plants, the combined effects of iron overload and light intensities on the photosynthetic capacity of leaves were particularly focussed upon in this study, using mung bean seedlings grown under varied conditions regarding the supply of light and iron. The seedlings, when supplied with excess iron (up to 1.0 mM) and low light (40 W/m2), did not suffer any loss of photosynthesis; further, the typical symptoms of iron toxicity, as shown in the leaves grown in sunlight at ca 450 W/m2 on an average, were not seen in those. Nonetheless, excess iron supply resulted in a marked increase in photosensitivity of the low light‐adapted seedlings. A large portion of iron accumulated in chloroplasts by the supply of excess iron was found to be incorporated into thylakoids as nonheme iron (NHI), which acts as a potent sensitizer, photogenerating singlet oxygen (1O2). The generation rate of 1O2 from thylakoids linearly increased with increasing content of NHI; this was in parallel with the NHI content dependence of photoinactivation rates of photosynthetic electron transport and key enzymes of the Calvin cycle in chloroplasts. The results suggest that Fe‐dependent photosensitization reactions, occurring via the 1O2 mechanism, may be deeply involved in cellular processes leading to developing iron toxicity symptoms in plants.
MEASUREMENT OF FORMAL POTENTIALS FOR HYPERICIN IN DIMETHYLSULFOXIDE
Authors: Redepenning Jody , Tao Nengbing 
Published: January 2008

AbstractThe formal potentials for hypericin are measured in dimethylsulfoxide using cyclic voltammetry. Two reversible one‐electron reductions and a more poorly defined multielectron oxidation are observed. The formal potentials for these processes are consistent with the visible spectrum of hypericin and they indicated that hypericin is both a good oxidizing agent and a good reducing agent in the excited state.
THERMODYNAMICS OF THE BINDING OF HEMATOPORPHYRIN ESTER, A HEMATOPORPHYRIN DERIVATIVE‐LIKE PHOTOSENSITIZER, AND ITS COMPONENTS TO HUMAN SERUM ALBUMIN, HUMAN HIGH‐DENSITY LIPOPROTEIN AND HUMAN LOW‐DENSITY LIPOPROTEIN
Authors: Rosenberger Vered , Margalit Rimona 
Published: January 2008

AbstractThe phenomena of the high affinity of porphyrins to the human serum proteins, albumin, high‐density lipoproteins (HDL) and low‐density lipoproteins (LDL) is well established. Yet, evaluation of the activities of these proteins as endogenous porphyrin carriers, especially with respect to receptor‐mediated porphyrin uptake into tumor cells, the merits of which are still in dispute, requires more quantitative protein‐porphyrin binding data. As a continuation of previous studies on this issue, the binding of several porphyrin systems to each of the three proteins, employing previously developed spectral methodologies, was studied. The specific systems reported here are hematoporphyrin ester (HPE), which is a novel hematoporphyrin derivative (HPD)‐like system, two porphyrin trimers (denoted O1 and O2) and a porphyrin dimer (denoted O3) isolated from HPE. Human serum albumin (HSA) was found to have a single high‐affinity site for the monomeric components of HPE, with an equilibrium binding constant of 3.6 × 106. The equilibrium parameters determined for the binding of the three HPE‐isolated oligomers to each of the serum proteins are: (1) Binding constants (Kb') of 2.3 × 106, 6.9 × 104 and 1.5 × 104 and number of sites per protein molecule (n) of 3, 1 and 5, for the binding of 01, 02 and 03, respectively, to HSA. (2) Kb’values of 15.5 × 103, 15.3 × 103 and 6.6 × 103 and n values of 1, 2 and 2, for the binding of O1, O2 and O3, respectively, to HDL. (3) Kb’values of 3.3 × 103, 2.28 × 104 and 8.0 × 103 and n values of 50, 20 and 16 for the binding of O1, O2 and O3, respectively, to LDL. These data are direct and clear support not only for the high affinity of porphyrins to serum proteins but specifically of stable oligomers that have been assigned critical roles in the photodynamic treatment of tumors. Of the three proteins, LDL is clearly the best camer, providing the highest drug payload with a moderate affinity (enough to bind and not too much to prevent release). These data are suggested to be promising for the postulated role of LDL in porphyrin uptake into tumor cells and to be useful in the future as benchmarks for novel porphyrin systems.
COMPARATIVE POTENCY OF BROAD‐BAND AND NARROW‐BAND PHOTOTHERAPY SOURCES TO INDUCE EDEMA, SUNBURN CELLS AND UROCANIC ACID PHOTOISOMERIZATION IN HAIRLESS MOUSE SKIN
Authors: Gibbs Neil K. , Norval Mary , Traynor Nicola J. , Crosby John C. , Lowe Graham , Johnson Brian E. 
Published: January 2008

AbstractThe Philips TL01 narrow‐band (311–313 nm) fluorescent lamp provides effective phototherapy for psoriasis and atopic eczema while emitting less erythemogenic radiation than conventional broad‐band (e.g. Philips TL12; 270–350 nm) sources. We studied the potency of TL01 and TL12 radiation to induce edema and sunburn cells (SBC) and to photoisomerize naturally occumng trans‐urocanic acid (UCA) to cis‐UCA in hairless mouse skin. Cis‐UCA has immunosuppressive properties and is a putative mediator of UV‐induced suppression of immune responses. For each source, there was UV dose dependence for all three responses. Within the dose ranges used, the potency ratio of TL12: TL01 radiation to induce equivalent edema and SBC was about 6:1. However, the potency ratio to induce cis‐IJCA was less than 2.3:1. Therefore, at a given level of edema or SBC induction, TL01 was more efficient than TL12 at UCA photoisomerization. The TL01 induction of immunomodulating cis‐UCA, while causing minimal skin injury, may relate to the therapeutic efficacy of this source in skin conditions with an immunological component.
DELAYED EMISSION OF CHLOROPHYLLaAGGREGATES AND RHODAMINE 6G EMBEDDED IN POLYMER MATRIX*
Authors: Frackowiak Danuta , Planner Alfons , Goc Jacek 
Published: January 2008

AbstractDelayed luminescence (in the microsecond time range) of the chlorophyll (Chl)a“dry” form as well as hydrated dimers located in a polyvinylalcohol film was measured from room temperature down to 8 K. In the same matrix the delayed luminescence of rhodamine 6G (Rhod) was investigated. The delayed emission both of Chlaand Rhod is probably due to the formation and delayed recombination of a radical pair. It seems that this process occurs without participation of triplet states, as it does not reflect their well‐known sensitivity to oxygen. The temperature dependence of the delayed luminescence of vanous Chl forms is different. In the region around 678 nm (dry monomer) delayed luminescence needs a thermal activation energy of about 0.03 eV, whereas at 740 nm (wet aggregates) delayed luminescence intensity increases linearly with decreasing temperature. Its assignment as a‐type delayed luminescence from the low‐lying triplet state can consistently be excluded from both the weak temperature dependence of the delayed fluorescence and its large intensity as compared to the prompt fluorescence. Delayed luminescence of Rhod is almost independent of temperature between 8 K and 300 K. The dependence of delayed luminescence intensity on exciting light intensity is linear at lower intensities and tends to saturation at higher. Therefore the delayed luminescence is not related to exciton annihilation. Positions and intensities of the Chl delayed luminescence bands show that it is not phosphorescence (β‐type delayed luminescence). The aggregation of both Chl and Rhod molecules strongly influences delayed luminescence since it differs in several properties if excited in the monomer or in the aggregate absorption range. Every aggregational form of dye emits its characteristic delayed luminescence band.
INTRAUTERINE 5‐AMINOLEVULINIC ACID INDUCES SELECTIVE FLUORESCENCE AND PHOTODYNAMIC ABLATION OF THE RAT ENDOMETRIUM*
Authors: YANG J. Z. , VUGT D. A. VAN , KENNEDY J. c. , REID R. L. 
Published: January 2008

Abstract— 5‐Aminolevulinic acid (ALA), a precursor of protoporphyrin IX (Pp IX), was administered into the rat uterine cavity in an attempt to selectively ablate the endometrium. Doses of ALA ranging from 4 to 50 mg were injected into one uterine horn of rats while the vehicle (saline) was injected into the contralateral horn. Animals were divided into three groups. In group one, the uterine horns were removed and processed for either fluorescent mi‐ croscopy or spectrophotofluorometry 3 h later. In group two, rats were allowed to survive for either 2 or 10 days, and then the uterine horns were harvested and processed histologically. In group three, both uterine horns were exposed to transmural light (approximately 150 J/cm*) 3 h after administration of ALA or saline and processed histologically either 2 or 10 days later.Fluorescent microscopy showed fluorescence in the endometrium and not in the myometrium. The maximum emission spectra of endometrial fluorescence occurred at 630 and 690 nm, characteristic of Pp IX. In contrast, no fluorescence was detected in saline‐treated uterine horns. Light exposure resulted in extensive damage only to the ALA‐treated endometrium. There was no indication of regeneration 10 days after treatment.We conclude from these studies that ALA administered into the lumen of the rat uterus is selectively converted into Pp IX within the endometrium. Furthermore, photoactivation of the Pp IX results in selective ablation of the endometrium.
AN EFFICIENT OXYGEN INDEPENDENT TWO‐PHOTON PHOTOSENSITIZATION MECHANISM
Authors: SMITH G. , McGimpsey W. G. , LYNCH M. C. , KOCHEVAR I. E. , REDMOND R. W. 
Published: January 2008

AbstractA novel oxygen‐independent photosensitization mechanism from the upper triplet state (Tn) of rose bengal has been demonstrated by selectively populating Tn by sequential two‐color laser excitation. Products formed from Tn inhibit red blood cell acetylcholinesterase and decrease viability of P388D1 mouse macrophage monocyte cells as measured by trypan blue exclusion assay. Laser flash photolysis studies indicate that Tn reacts efficiently, as evidenced by permanent photobleaching of T1 absorption, with chemical yields approaching unit efficiency. This mechanism may have application for oxygen deficient photosensitization under high intensity, pulsed laser irradiation.
HOMOGENEOUS PHOTOBLEACHING OF CHLOROPHYLL HOLOCHROMES IN A PHOTOSYSTEM I REACTION CENTER COMPLEX
Authors: Purcell Marc , Carpentier Robert 
Published: January 2008

AbstractChlorophyll (Chl) photobleaching and P700 photodegradation were followed simultaneously in a P700 Chi a‐protein complex (Chl a/P700 < 35). During strong illumination, the photobleaching kinetics of the bulk Chl corresponded with that of P700 photodegradation. The absence of a blue shift of the absorption maximum at 678 nm after photobleaching indicated the simultaneous degradation of all Chl holochromes and the absence of long wavelength‐absorbing energy traps that would protect P700 against excess light energy. It was deduced that in the P700 reaction center core complex, the excitons are uniformly distributed amongst the Chl holochromes, which decreases the deleterious effects of excess light energy on P700 and protects the photosystem against photoinhibition.
PHOTOCHEMISTRY OF TYPE I ACID‐SOLUBLE CALF SKIN COLLAGEN: DEPENDENCE ON EXCITATION WAVELENGTH
Authors: Menter Julian M. , Williamson George D. , Carlyle Kimberly , Moore Cyril L. , Willis Isaac 
Published: January 2008

Abstract—Although previous studies have demonstrated that the predominant photochemistry of type I collagen under 254 nm irradiation may be attributed either to direct absorption by tyrosine/phenylalanine or to peptide bonds, direct collagen photochemistry via solar UV wavelengths is much more likely to involve several age‐ and tissue‐related photolabile collagen fluorophores that absorb in the latter region. In this study, we compare and contrast results obtained from irradiation of a commercial preparation of acid‐soluble calf skin type I collagen in solution with UVC (primarily 254 nm), UVA (335–400nm) and broad‐band solar‐simulating radiation (SSR; 290^1–00nm). Excitation spectroscopy and analysis of photochemically induced disappearance of fluorescence (fluorescence fading) indicates that this preparation has at least four photolabile fluorescent chromophores. In addition to tyrosine and L‐3,4‐dihydroxyphenylalanine, our sample contains two other fluorophores. Chromophore I, with emission maximum at 360 nm, appears to be derived from interacting aromatic moieties in close mutual proximity. Chromophore II, with broad emission at430–435 nm, may be composed of one or more age‐related molecules. Collagen fluorescence fading kinetics are sensitive to excitation wavelength and to conformation. Under UVC, chromophore I fluorescence disappears with second‐order kinetics, indicating a reaction between two proximal like molecules. Adherence to second‐order kinetics is abrogated by prior denaturation of the collagen sample. A new broad, weak fluorescence band at400–420 nm, attributable to dityrosine, forms under UVC, but not under solar radiation. This band is photolabile to UVA and UVB wavelengths. Amino acid analysis indicates significant destruction of aromatic amino acids under UVC, but not under UVA or SSR. When properly understood, collagen fluorescence fading phenomena may act as a sensitive molecular probe of structure, conformation and reactivity.
OCTA‐ALKYL ZINC PHTHALOCYANINES: POTENTIAL PHOTOSENSITIZERS FOR USE IN THE PHOTODYNAMIC THERAPY OF CANCER
Authors: Cook Michael J. , Chambrier Isabelle , Cracknell Steven J. , Mayes Denise A. , Russell David A. 
Published: January 2008

Abstract—The synthesis, characterization and electronic spectra of a series of nine 1,4,8,11,15,18,22,25‐octa‐alkyl zinc phthalocyanines (ZnPc), potential photosensitizers for the photodynamic therapy of cancer, are described. The substituents on the phthalocyanine (Pc) macrocycle “red‐shift” the absorbance maximum, in cyclohexane, of all nine members of this series to a value of 703 ± 2 nm, with a corrected fluorescence emission maximum for the octadecyl derivative of 715 nm. The solubilities and degree of aggregation of six examples in cyclohexane have been measured. The highest homologue, the octadecyl derivative, remains essentially unaggregated to a concentration of 1.5 ± 10−4 mol dm−3. The photostability of this Pc has been examined and the compound shown to be sensitive to photooxidation processes, which lead to its decomposition to 3,6‐fcw‐decylphthalimide. Known singlet oxygen quenchers inhibit the photodecomposition. In a comparative study, the octadecyl ZnPc underwent a more rapid photodecomposition than the corresponding metal‐free derivative.
CHLOROPHYLLS IN POLYMERS. II. PHEOPHYTINaIN POLYMERS and THE INFLUENCE OF STRETCHING ON THE STATE OF CHLOROPHYLLS IN ANHYDROUS POLYMER FILMS
Authors: Wróbei D. , Zandvoort M. A. M. J. van , Lettinga P. , Ginkel G. van , Levine Y. K. 
Published: January 2008

Abstract—Inthe first part of this study the spectral properties of pheophytinain rigid, unstretched anhydrous polyvinyl alcohol and nitrocellulose films have been studied in order to establish the influence of the central magnesium atom on the state of chlorophylls in polymer systems. The absorption, fluorescence, excitation spectra and fluorescence intensity decays in the polymer films and in the solutions from which they are cast are reported. It is shown that pheophytinaaggregate formation is influenced by the nature of the polymer system. An aggregate of pheophytinais found in polyvinyl alcohol films over a wide concentration range. On the other hand, pheophytinaexists in the monomeric form in unstretched nitrocellulose films at concentrations below 6 × 10‐6mol/g.In the second part of this work, the influence of stretching of the films on the state and distribution of embedded chlorophyll pigments, is described. Here we show that the chlorophyllamolecules are found to undertake a heterogenous distribution in polyvinylalcohol matrices, since stretching partially disrupts the pocket‐like structures present in unstretched films. In contrast, chlorophyllaand pheophytinamolecules can be embedded in a monomeric state in nitrocellulose matrices and moreover they remain homogeneously distributed upon stretching. The chlorophyll/nitrocellulose system is concluded to be a useful model system for studies of donor‐donor energy transfer processes.