bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECTS OF DEMETHYLCHLORTETRACYCLINE PHOTOTOXICITY ON THE STRUCTURE and FUNCTIONS OF RAT LIVER MITOCHONDRIA
Authors: Takagi Shigeru , Mizuno Nobuyuki , Adachi Kayo , Wakabayashi Takashi
Published: January 2008

Abstract— The phototoxic effects of demethylchlortetracycline (DMCT) with UVA radiation on isolated rat liver mitochondria were studied. DMCT at concentration of 21.5 μM with 5.53 times 10−2 J cm'of UVA was found to be a potent uncoupler of oxidative phosphorylation. DMCT alone also uncoupled mitochondria but at higher concentrations (105 μM). ATPase activity was remarkably induced in mitochondria exposed to DMCT (21.5 μM) plus UVA (120% of DNP‐stimulated ATPase activity). Content of ATP in such mitochondria when measured after addition of ADP was much smaller than that in control mitochondria. Ultrastructurally, mitochondria treated either with DMCT (21.5 μM) or with UVA alone stayed in the condensed configuration. On the other hand, uncoupled mitochondria treated with DMCT plus UVA became swollen and were changed into the orthodox configuration.
ANTIOXIDANT DEFENSE OF THE CABBAGE LOOPER, Trichoplusia ni: ENZYMATIC RESPONSES TO THE SUPEROXIDE‐GENERATING FLAVONOID, QUERCETIN, and PHOTODYNAMIC FURANOCOUMARIN, XANTHOTOXIN
Authors: Ahmad Sami , Pardini Ronald S.
Published: January 2008

Abstract— Superoxide dismutase (SOD) activity was induced by ca 2‐fold (to5–6 U) when Trichoplusia ni midfifth‐instar larvae were exposed to two toxic oxygen species generating plant pro‐oxidants, quercetin (a flavonoid) and xanthotoxin (8‐methoxypsoralen; a photoactive furanocoumarin). Very high catalase (CAT) activity (ca 300 U) of this insect was not affected by 8‐methoxypsoralen, but was slightly decreased by quercetin. No Se‐dependent glutathione peroxidase (GPOX) activity was observed, but high glutathione transferase (GST) peroxidase activity (over 50 U) in this insect was slightly induced by 8‐methoxypsoralen (8‐MOP), and was partially inhibited by quercetin, 8‐Methoxypsoralen induced the activity of glutathione reductase (GR), but quercetin partially inhibited the activity of this enzyme. An increase in SOD activity appears to be the main response of this insect to dietary exposure to pro‐oxidant compounds. High CAT activity guarantees the destruction of large cellular increases in H2O2, a product of rapid dismutation of superoxide from induced activity of SOD. Moreover, GST with its peroxidase activity apparently substitutes for GPOX, forming a GST/GR enzyme pair as a primary line of defense against deleterious organic hydroperoxides. These studies clearly point out the key role for an insect's antioxidant enzymatic countermeasures against defensive pro‐oxidant compounds produced by plants.
PHASE‐SPECIFIC EFFECT OF NITRATE ON PHYTOCHROME‐MEDIATED GERMINATION IN SPORES OF Dryopteris filix‐mas L.*
Authors: Haas C. J. , Scheuerlein R.
Published: January 2008

Abstract— Induction of germination in spores of Dryopteris filix‐mas L. shows an absolute requirement for light with phytochrome as photoreceptor. The effectiveness of a red light (R) irradiation is affected by the ionic composition of the culture medium (Haupt, Planta164,63–68, 1985). In this paper NO3−is identified as the component mediating this effect whereas ammonium or organic nitrogen‐containing compounds, tested so far, are ineffective. Enhancement by NO3− can be observed at concentrations 1 μM and an optimum is found around 1 mM. The kinetics of NO3− action are elucidated by restricting the presence of NO3− to defined periods after sowing, and they are compared with kinetics of Pfr action. As a result, the enhancement of NO3− can be attributed to a specific phase in the signal‐transduction chain: the promotive effect of nitrate is only obtained if the Pfr presence coincides with or slightly preceeds the presence of NO3−. If Pfr can act for 15 or 20 h and is reversed thereafter by far‐red light (FR), NO3− added during this period or immediately after FR is effective and this enhancement vanishes during 6 h following FR. In contrast, NO3− has no effect as long as it is applied only during a period before Pfr is formed. Moreover, a modulation of the effectiveness of the photoconversion Pr to Pfr by NO3− can be excluded. These results are interpreted by the action of NO3− during early steps in the Pfr‐induced signal‐transduction chain. However, an additional effect of NO3− on the “coupling” of Pfr itself to subsequent dark reactions cannot be excluded yet.
THE STIMULATING EFFECT OF A COLD, DARK PRETREATMENT ON THE ETIOPLAST/CHLOROPLAST TRANSFORMATION OF ANGIOSPERMS–II. SYNERGISM BETWEEN RED‐LIGHT and COLD PRETREATMENT ON THE CO2‐ and O2‐GAS‐EXCHANGE OF WHEAT LEAVES
Authors: Schönbohm Ekkehard , Czeska‐Werner Ulrike
Published: January 2008

Abstract— Recently we reported on the stimulating effect of a cold, dark pretreatment on the processes of greening of dark‐grown angiosperms under continuous white light (Schönbohm et al., 1988; Physiol. Plant.72,541–546). These effects could be nullified by a subsequent second dark phase (25°C) which precedes the white light period.

Our analysis was now focused on the effect of cold, dark pretreatments (with or without red‐preirradiation) on the gas exchange (O2; CO2) of etiolated primary leaves of wheat during a subsequent white light period. The following results were obtained:

(1) The net‐O2‐consumption under continuous white light decreased much more quickly after a cold than after a warm pretreatment.

(2) This effect was enhanced by red‐preirradiation.

(3) The O2‐compensation point was reached more quickly during the de‐etiolation period when the leaves had been subjected to a cold instead to a warm pretreatment.

(4) The “cold‐effect” could be nullified by a subsequent warm, dark pretreatment (in this material the compensation point could not be reached within 8 h).

(5) Cold treated material which had also been exposed to red light showed during the first 30 min of de‐etiolation an extremely strong “out‐burst” of CO2. No correlation was apparent between the O2‐uptake and this high CO2‐release.

(6) A cold, dark pretreatment induces a decrease of CO2‐release during the second half of the de‐etiolation period. This effect could be nullified by a secondary warm, dark treatment given after the cold, dark pretreatment.

Our experiments indicate that red‐preirradiation and cold, dark pretreatment stimulate chlorophyll synthesis (Schonbohm et al., 1988) and also photosynthetic O2‐evolution and CO2‐uptake. We also assume that this pretreatment causes CO2 release that is neither directly related to the respiratory electron transport chain nor to the photorespiration.
MULTIPLE ACTION OF FAR‐RED LIGHT IN PHOTOPERIODIC INDUCTION and CIRCADIAN RHYTHMICITY
Authors: Deitzer G. F. , Frosch S. H.
Published: January 2008

Abstract— It is generally accepted that phytochrome influences the photoperiodic induction of flowering through its interaction with the circadian clock mechanism. We have attempted to separate the effects of phytochrome on the clock mechanism from those that mediate flowering directly by examining a number of responses that are unrelated to flowering but are also regulated by the circadian clock. Gas exchange measurements of both CO2 and H20 vapor were monitored under light conditions (200 μmol m 2 s−1) where the addition of far‐red energy is required for the maximal promotion of flowering. In addition, photosynthetic capacity and maximal transpiration rates were measured in plants grown under continuous dim (20 μmol m−2 S−') light, with or without supplemental far‐red, by exposing them briefly to saturating fluxes (1000 μmol m−2 s‐l) of light. Net CO2 fixation was very weakly rhythmic in plants grown under both high and low light and this weak oscillation was completely suppressed by far‐red light. Far‐red also suppressed the rhythm in transpiration under high light, but the rhythm was immediately reinstated when the far‐red light was removed. The phase of this rhythm was also reset with the next peak always occurring15–18 h after the far‐red was turned off. When grown under dim light, the transpiration rhythm was not suppressed and the amplitude of the oscillation was more than doubled. Far‐red light appears to interact with the rhythm in transpiration in a manner suggesting that the stomatal rhythm may be coupled to the same clock oscillator that regulates the flowering rhythm.
SEQUENCE‐SPECIFICITY OF THE ALKALI‐SENSITIVE LESIONS INDUCED IN DNA BY HIGH‐INTENSITY ULTRAVIOLET LASER RADIATION
Authors: Kovalsky O. I. , Panyutin I. G. , Budowsky E. I.
Published: January 2008

Abstract— The action of high‐intensity (109‐1012 W/m2) UV (266 nm) laser radiation pulses (duration ca 10 ns or ca 40 ps) on liquid aqueous solutions of DNA is known to cause not only single‐ but also two‐quantum modification of nucleic bases. The action of hot piperidine on the laser‐irradiated DNA results in non‐random splitting of polynucleotide chain. Hence, at least some of the modified nucleoside residues are alkali‐sensitive lesions (ASLs). The distribution of ASLs along the DNA chain shows that the position of these lesions corresponds with pyrimidines in the PyPy sequences (similar to those formed via single‐quantum conversions) as well as with deoxyguanosine residues. The last ASLs result from two‐quantum reactions and occur much more efficiently than the direct photo‐induced cleavage of the internucleotide (phosphodiester) bond. It has been shown with fragments of plasmids pUC18, pUC19 and pBR322 (total length over 600 base pairs) that the relative efficiency of ASLs at deoxyguanosine sites depends on the primary structure context and can differ by an order of magnitude. The highest efficiency of modification is observed when a purine is 3' neighbour to the 2'‐deoxyguanosine, i.e. at 5'‐GPu‐3 sites. However, considerable variations in the modification efficiency were also found in these sequences.
CHRONIC METABOLIC MEASUREMENTS OF NORMAL BRAIN TISSUE RESPONSE TO PHOTODYNAMIC THERAPY
Authors: Chopp M. , Chen Q. , Dereski M.O. , Hetzel F.W.
Published: January 2008

Abstract— The metabolic response of normal rat brain to photodynamic therapy (PDT) was studied over a 1 week interval using in vivo 31P‐NMR spectroscopy. Rats injected with 12.5 mg/kg Photofrin II were submitted to brain photoactivation 48 h after drug administration with either 140 or 70 J/cm2 light (630 ± 1 nm) from an Argon dye laser. Control studies, animals not given drug or light, animals submitted only to brain illumination without drug, and animals given drug but no light, were also performed. The data revealed a transient metabolic degradation; a decrease in the ratio of (3‐nucleotriphosphate to inorganic phosphate (P < 0.001) at 24 h after PDT treatment was followed by a return to pretreatment spectral values. Brain tissue alkalosis was also noted, with significant (P < 0.05) differences in brain tissue pH detected at 72 h post treatment between 70 J/cm2 PDT vs control studies and at 1 week post treatment between 140 J/cm2vs 70 J/cm2, 140 J/cm2vs no light‐no drug and 140 J/cm2vs drug only. The data suggest that there is no difinitive metabolic marker from 31P‐NMR spectroscopy that can identify necrotic brain tissue caused by PDT. Phosphorus‐31 NMR data are also presented which suggest that PDT damage to brain is not solely the result of microvascular occlusion causing ischemic necrosis.
PHOTO‐CIDNP DETECTION OF PYRIMIDINE DIMER RADICAL CATIONS IN ANTHRAQUINONESULFONATE‐ SENSITIZED SPLITTING
Authors: Young Tish , Nieman Ron , Rose Seth D.
Published: January 2008

Abstract— –Anthraquinone‐2‐sulfonate (AQS) photosensitizes pyrimidine dimer splitting. Electron abstraction from the dimer is thought to induce dimer splitting, but direct evidence for the existence and intermediacy of dimer radical cations has been lacking. By employing photochemically induced dynamic nuclear polarization, we have found emission signals in the NMR spectra of dimers upon photolysis of dimers in the presence of anthraquinone‐2‐sulfonate. The two dimers employed were ci?, syn‐thymine dimer in which the JV(l)‐positions were linked by a three‐carbon bridge and the N(3), N(3′)‐dimethyle derivative of that compound. The anthraquinone‐2‐sulfonate sensitized photochemically induced dynamic nuclear polarization spectrum of the methylated derivative exhibited an emission signal from the dimer‐C(6) hydrogens. This result implied the existence of a dimer radical cation (mD+) formed by electron abstraction by excited anthraquinone‐2‐sulfonate and nuclear spin sorting within a solvent caged radical ion pair [mD+ AQS‐]. Product pyrimidine photochemically induced dynamic nuclear polarization signals were also seen [enhanced absorption by C(6)‐hydrogens and emission by C(5)‐methyl groups]. Nuclear spin polarization in the product resulted from spin sorting in one or more of its precursors, including mD+. The results support the conclusion that dimer radical cations not only exist but are intermediates in the photosensitized splitting of pyrimidine dimers by anthraquinonesulfonate.
THE REACTION OF SINGLET OXYGEN WITH PROTEINS, WITH SPECIAL REFERENCE TO CRYSTALLINS
Authors: Balasubramanian D. , Du X. , Zigler J. S.
Published: January 2008

Abstract— –Photosensitized oxidation of the eye lens proteins, the crystallins, is thought to lead to protein crosslinks and high molecular weight aggregates. Such protein modifications may be important factors in the formation of lens opacities or cataracts. We focus attention here on type 2 photo‐oxidation involving the reaction of singlet oxygen (1O2) with crystallins and some “control” proteins. We find that: (1) trp residues are oxidized to N‐formyl kynurenine and related products, but this in itself does not lead to the production of high molecular weight protein aggregates of the protein; (2) tyr residues react with 1O2 but we do not detect dihydroxyphenylalanine or bityrosine nor are protein crosslinks formed as a result; (3) oxidation of his residues appears necessary for high molecular weight protein covalent aggregates to form. Proteins devoid of his, e.g. melittin or bovine pancreatic trypsin inhibitor, do not form high molecular weight products upon reaction with 1O2. Prior reaction and blocking of his inhibits the crosslinking reactions. (4) The oxidized protein is seen to be more acidic than the parent and has an altered tertiary structure. (5) Among the crystallins, reactivity towards 1O2 varies in the order γ > β > α and also γ A/E > γ D > γ B crystallin.
CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER REACTIONS IN LIPID BILAYER VESICLES: VECTORIAL ELECTRON TRANSFER ACROSS THE BILAYER FROM REDUCED CYTOCHROME c IN THE INNER COMPARTMENT TO OXIDIZED FERREDOXIN IN THE OUTER COMPARTMENT
Authors: Zhao Zhan‐Gong , Tollin Gordon
Published: January 2008

A negatively charged large unilamellar vesicle system containing a membrane‐bound photo‐sensitizer (chlorophyll, Chi), a reduced redox protein [cytochrome c, cyt c(red)] in the inner aqueous compartment, an oxidized redox protein [ferredoxin, Fd(ox)] in the outer aqueous compartment, and propylene diquat (PDQ2+) as a mediator, was investigated using both flash and steady‐state photolysis techniques. The results demonstrate that the light‐generated triplet state of Chi (3Chl) was initially quenched by PDQ2+ at the outer membrane surface to form Chi cation radical (Chl+) and the reduced diquat (PDQ+). This was succeeded by a biphasic recombination between Chi+ and PDQ+. The slow phase of the recombination process, which represents reverse electron transfer between Chl+ and those PDQ+ molecules which escaped from the membrane surface, could be suppressed effectively both by the reduction of Chl^ in the inner monolayer of the vesicles by cyt c(red), and by the reoxidation of PDQ+ by Fd(ox) in the outer aqueous compartment. These reactions lead to the permanent accumulation of oxidized and reduced product proteins, i.e. cyt c(ox) in the inner compartment and Fd(red) in the outer compartment. The yields of such accumulation were 11%, based on the 3Chl quenched, and 1.4%, based on absorbed quanta, under the conditions used in the present study. This system mimics one of the key events in natural photosynthesis and results in an appreciable storage of electromagnetic energy in the reaction products.
DEMONSTRATION THAT PHOSPHORESCENT 6‐BROMO‐2‐NAPHTHYL SULFATE CAN BE USED TO PROBE HEME ACCESSIBILITY IN HEME PROTEINS
Authors: Bayles Stephen W. , Beckham Suzy , Leidig Paige R. , Montrem Anne , Taylor Mervin L. , Wright Tony M. , WU Ying , Schuh Merlyn D.
Published: January 2008

The phosphorescence properties of 6‐bromo‐2‐naphthyl sulfate (BNS) in aqueous solution were studied. The phosphorescence lifetime is several hundred us and is self‐quenched. Although a fluorescent photoproduct is formed from BNS, it does not interfere with the decay properties of triplet‐state BNS and its utility as a probe of the accessibility of the heme group in heme proteins. Quenching of BNS phosphorescence does not occur for the non‐heme protein lysozyme and apomyoglobin but occurs by a dynamic mechanism with a quenching constant of1–2 × 109M−1 s−1 for cytochrome c and myoglobin and with a quenching constant of 6.2 × 109M−1 s−1 for protoporphyrin IX. The phosphorescence of an inclusion complex of 1‐bromonaphthalene and β‐cyclodextrin is not quenched by heme‐containing proteins. The temperature and viscosity dependencies of the rate with which BNS phosphorescence is quenched by microperoxidase‐11 are consistent with unit quenching efficiency. These results indicate that quenching of BNS phosphorescence occurs only upon contact with the quencher, and the quenching constant can be used to assess the degree of accessibility of the heme group.
SUBNANOSECOND SINGLE PHOTON TIMING MEASUREMENTS USING A PULSED DIODE‐LASER*
Authors: Farrens David L. , Song Pill‐Soon
Published: January 2008

The convenient and inexpensive use of a pulsed diode‐laser (Hamamatsu Photonics PLP‐01 660 nm) is demonstrated as a low cost alternative to a standard pulsed laser or gas discharge flash system in a commercial time‐correlated single photon counting instrument. Fluorescence lifetimes of compounds of photobiological interest such as phytochrome, chlorophyll a, 1,1 ′‐diethyl‐4,4′ carbocyanine iodide (DCI/cryptocyanin),5,10,15,20‐tetra(p‐phenyl) porphyrin and stentorin I are presented using the pulsed diode‐laser source.
EFFECTS OF SOLAR RADIATION ON MOTILITY IN: Stentor coeruleus
Authors: Häder Donat‐P. , Häder Maria A.
Published: January 2008

The effects of solar radiation on the motility of the colored ciliate, Stentor coeruleus, have been assessed as a photodynamic model system for hypericism. The organism has been found to be extremely sensitive to solar radiation–a few minutes of unfiltered radiation suffice to arrest motility and decrease the velocity of movement. Removing UV‐B and UV‐A radiation prolongs the tolerated exposure times. From the present study, the mechanisms of the photodynamic action in S. coeruleus and in hypericin‐sensitized reactions have not been resolved in terms of Type I and II mechanisms.
PHOTOLYSIS OF DIBENZYLKETONES IN SUPERCRITICAL ETHANE and CARBON DIOXIDE*
Authors: O'Shea Kevin E. , Combes James R. , Foxt Marye Anne , Johnston Keith P.
Published: January 2008

The Norrish Type I photofragmentation of two dibenzylic ketones (l,3‐diphenyl‐2‐pro‐panone and l‐(4‐methylphenyl)‐3‐phenyl‐2‐propanone) in supercritical ethane and carbon dioxide proceeds without evidence for cage recombination of the photogenerated radical pair. A statistical mixture of the bibenzyls formed by random coupling of benzyl and p‐xylyl radicals was observed and the first order rate constant for the depletion of the reactant was independent of pressure. These results indicate that solvent cage effects are not operative in these low viscosity supercritical fluids even in the near critical region where solute‐solvent clustering is presumably maximal.
STRUCTURAL ELUCIDATION OF THE 8‐METHOXYPSORALEN OXIDIZED PRODUCT THAT INHIBITS THE CHEMOTACTIC ACTIVITY OF POLYMORPHONUCLEAR NEUTROPHILS TOWARD ANAPHYLATOXIN C5a
Authors: Mizuno Nobuyuki , Esaki Kenji , Sakakibara Jinsaku , Murakami Nobutoshi , Nagai Shinichi
Published: January 2008

The chemical structure of the 8‐methoxypsoralen oxidized product that inhibits the chemo‐tactic activity of anaphylatoxin C5a was determined to be 2,3‐dihydro‐2,9‐dimethoxy‐3‐hydroxy‐7‐oxo‐7H‐futo[3,2‐g][l]benzopyran. Its minimal concentration required to obtain the maximum inhibition of C5a des Arg (1 times 10−8M) chemotactic activity is 2.5 times 10−8M. Bioactivity of this substance was maintained for 2 weeks, stored in a dark room at room temperature under aerobic conditions. There is a possibility that this substance may be useful in the treatment of immune complex diseases.
HEAVY‐ATOM LABELLED RETINAL ANALOGUES LOCATED IN BACTERIORHODOPSIN BY X‐RAY DIFFRACTION*
Authors: Büldt G. , Konno K. , Nakanishi K. , Plohn H.‐J. , Rao B. N. , Dencher N. A.
Published: January 2008

Abstract– The location of the heavy‐atom label of three different retinal analogues in the plane of the purple membrane was determined by x‐ray diffraction. The three analogues, i.e. 9‐bromoretinal and 13‐bromoretinal labelled in the polyene chain as well as the ring‐labelled HgCI‐retinal, were incorporated into bacteriorhodopsin (BR) either biosynthetically using a retinal‐deficient mutant strain of Halobacterium halobium or with photochemically bleached bacterioopsin. All BR samples regenerated with retinal analogues were functionally active as proton pumps. The diffraction data show that the cyclohexene ring of retinal is situated in the corner formed by helices 4E and 5D. the 13‐methyl group adjacent to helix 6C and therefore the Schiff's base nitrogen about midway between helices 6C and 2G. The 9‐bromo label is found slightly off the line connecting the two other labels, directed towards helix 3F, suggesting torsion of the polyene chain or slight incline of the ring. The position and orientation of retinal obtained in our experiments are in agreement with data from neutron diffraction and high‐resolution electron microscopy. This indicates that the heavy‐atom labeled chromophores, 9‐bromo‐ and 13‐bromo‐ as well as HgCI‐retinal, are isomorphously incorporated into BR. These samples will allow kinetic investigation of light‐induced structural changes of retinal during BR's pumping cycle using x‐ray diffraction as well as extended x‐ray absorption fine structure experiments probing changes in the retinal neighbourhood between different intermediaies of the photocycle.
PHOTODESTRUCTION OF BACTERIORHODOPSIN
Authors: CZÉAGÉA JÓAZSEF , REINISCH LOU
Published: January 2008

Abstract— Suspensions of purple membrane fragments showed obvious signs of degradation after illumination with intense pulses of light from 10 ns frequency doubled Nd: YAG laser at 532 nm with intensity densities in excess of 1 MW/cm2. Using controlled illumination, a small fraction of the bacteriorhodopsin protein molecules were randomly destroyed in samples with a low salt concentration (12.5 mM) and pH = 7.9. Calculations using information from the changes in the optical absorbance spectrum and transient changes in the optical absorbance spectrum during the photocycle support a model where one protein molecule of the bacteriorhodopsin trimer is photodestroyed, the other two protein molecules switch to a blue state. In the blue state, the protein molecules have a red shifted absorption, with a peak near 600 nm. The blue state molecules show transient absorption changes at 656 nm that are similar to the native bacteriorhodopsin, except the O state is missing or altered. Additionally, the changes in curvature of the purple membrane fragments that occur during the photocycle of intact protein molecules are severely depressed. The addition of salts to the photodestroyed suspension can change the blue state molecules back to a state with an absorption maximum at 568 nm. The salt ions probably shield the other members of the trimer from the photodestroyed protein. In these reconstituted samples, the O state is observed at 656 nm; however, the membrane bending is not observed.
EFFECTS OF LIGHT BEAM SIZE ON FLUENCE DISTRIBUTION AND DEPTH OF NECROSIS IN SUPERFICIALLY APPLIED PHOTODYNAMIC THERAPY OF NORMAL RAT BRAIN
Authors: Chen Qun , Wilson Brian C. , Dereski Mary O. , Patterson Michael S. , Chopp Michael , Hetzel Fred W.
Published: January 2008

Abstract—

The light fluence distributions of 632.8 nm light incident on the exposed surface of normal rat brain in vivo have been measured using an interstitial, stereotactically‐mounted optical fiber detector with isotropic response. The dependence of the relative fluence rate on depth and the spatial distribution of fluence were compared for incident beam diameters of 3 and 5 mm. The fluence rate at depth of 1–6 mm along the optical axis within the brain tissue was approximately 70% greater for a 5 mm diameter beam than for a 3 mm beam, at the same incident fluence rate, although the plots of the relative fluence rate vs depth were parallel over the depth range 1–6 mm. The depths of necrosis resulting from photodynamic treatment of brain tissue using the photosensitizer Photofrin and irradiation by 632 nm light with 3 and 5 mm incident beams were also measured. The observed difference in necrosis depths was consistent with the measured difference in fluence. The importance of beam size in photodynamic treatment with small diameter incident light fields is discussed.
THE HAIRLESS MOUSE MODEL OF PHOTOAGING: EVALUATION OF THE RELATIONSHIP BETWEEN DERMAL ELASTIN, COLLAGEN, SKIN THICKNESS AND WRINKLES
Authors: Moloney Stephen J. , Edmonds Susan H. , Giddens Lori D. , Learn Douglas B.
Published: January 2008

Abstract—

Quantitative and qualitative changes in dermal collagen and elastin occur in response to chronic ultraviolet (UV) irradiation. These changes have been implicated in the genesis of the wrinkling seen in chronically irradiated, or photoaged skin. We examined the relationship between wrinkle formation and changes in dermal structural protein content and type. Skh‐1 hairless mice were irradiated with suberythemal doses of UV‐B three times a week for up to 20 wk. Visible wrinkling was present after 6–7 wk of irradiation. Dermal elastic fiber content was quantified by color image analysis of paraffin‐embedded tissue. There was no significant difference in dermal elastic fiber content between irradiated and age‐matched control mice after either 10 or 20 wk of irradiation. The effect of UV‐B irradiation on total dermal collagen content, ratio of collagen type III‐type I, and extent of glycosylation and crosslinking of collagen was no different in irradiated and age‐matched control mice after 10 wk of irradiation. Increased epidermal thickness was evident in frozen sections after 6 wk of irradiation, and the thickness increased with continued irradiation. Dermal thickening was evident after 10 wk of irradiation. Sufficient UV‐B irradiation will eventually cause changes in dermal elastin and collagen content; however, wrinkle formation precedes such changes. A causal relationship between wrinkle formation and dermal structural protein content changes in Skh‐1 hairless mice could not be established in this study.
PROTECTION BY THE FLUORIDE ION AGAINST PHTHALOCYANINE‐INDUCED PHOTODYNAMIC KILLING OF CHINESE HAMSTER CELLS
Authors: Ben‐Hur Ehud , Clay Marian E. , Vicioso Eduardo F. , Antunez Antonio R. , Rihter Boris D. , Kenney Malcolm E. , Oleinick Nancy L.
Published: January 2008

Abstract— When a dilute F‐ solution was added to a culture of Chinese hamster cells that had been preincubated with an aluminium phthalocyanine sensitizer derived from AlPcCI, the photosensitivity of the cells was markedly reduced compared to control cells not treated with F‐. Under the same treatment conditions, the reduction in [3H]thymidine incorporation into cellular DNA caused by light and this sensitizer and the production of DNA‐protein crosslinks caused by light and this sensitizer were also inhibited by F‐. In contrast, the killing of Chinese hamster cells, the reduction of thymidine incorporation by the cells, and the production of DNA‐protein crosslinks in the cells caused by the combination of light and either Photofrin II or the silicon phthalocyanine HOSiPcOSi(CH3)2(CH2)3‐N(CH3)2 were not inibited by F‐. We conclude that the aluminium phthalocyanine sensitizer used is largely or completely AlPc(OH)(H2O), that it is converted to a fluoro complex by F‐ that this compound probably is a less efficient generator of photochemical damage at a critical cellular target(s) than is AlPc(OH)(H2O). The inhibition of thymidine incorporation and DNA‐protein crosslink formation indicates that the effects of F‐ can be expressed at intracellular sites. It is further concluded that the silicon phthalocyanine sensitizer and Photofrin II do not interact significantly with F‐.
CHEMIEXCITATION IN THE PEROXIDATIVE METABOLISM OF DIETHYLSTILBESTROL. METABOLIC PRODUCTS
Authors: Knudsen Fernanda da Silva , Cilento Giuseppe
Published: January 2008

Abstract— In the presence of the surfactant hexadecyltrimethyl ammonium bromide (CTAB) a cascade of electronically excited states accompanies the successive steps in the peroxidative metabolization of the strong estrogenic and tumourogenic diethylstilbestrol. Reversing the order by necessity, we report in this first paper results with the metabolites.

Exposure of 4‐hydroxypropiophenone, Z, Z‐dienestrol or E, E‐dienestrol to horseradish peroxidase and H2O2 promotes oxygen uptake and spectral alterations. Light emission is observed provided that the surfactant CTAB is present. With the three substrates, 4‐hydroxybenzoic acid and a new metabolite, p‐benzoquinone, have been identified. With both dienestrol isomers, 1‐(4'‐hydroxyphenyl)‐propan‐1‐on‐2‐ol has been identified.

In all cases the emission spectrum indicates the presence of several emitters. Possible chemiexcitation routes are pointed out. From the dramatic increase of the emission by enhancers, values as high as 1 × 10‐5 are inferred for the product of the quantum yields of chemiexcitation and energy transfer.
PHOTODESTRUCTION OF TUMOR CELLS BY INDUCTION OF ENDOGENOUS ACCUMULATION OF PROTOPORPHYRIN IX: ENHANCEMENT BY 1, 10‐PHENANTHROLINE
Authors: Rebeiz Natalie , Rebeiz Carole C. , Arkins Sean , Kelley Keith W. , Rebeiz Constantin A.
Published: January 2008

Abstract— Rapidly proliferating transformed mammalian cells can be photodesroyed in vitro upon inducing the accumulation of endogenous protoporphyrin IX (Proto). Proto biosynthesis and accumulation were triggered by manipulation of the porphyrin‐heme biosynthetic pathway. Proto accumulation in cultured cells was induced by treatment with 1.0 mMδ‐aminolevulinic acid (ALA), a naturally occurring 5‐carbon amino acid, for 3.5 h. In darkness, significant Proto accumulation became evident within 3.5 h of incubation. In the light, the accumulated tetrapyrroles triggered destruction of treated cells within the first 30 min of illumination, probably via the rapid oxidation of cellular constituents by singlet oxygen. Protoporphyrin IX accumulation and specific cell lysis increased significantly by inclusion of 0.75 mM 1,10‐phenanthroline (Oph), a tetrapyrrole biosynthesis modulator. Slower growing untransformed cells did not accumulate significant amounts of Proto following ALA and Oph treatment unless stimulated to proliferate with the mitogenic lectin Concanavalin A.
INHIBITION OF PHOTOTAXIS IN Volvox aureus BY NATURAL AND SIMULATED SOLAR ULTRAVIOLET LIGHT
Authors: Blakefield Mary K. , Calkins John
Published: January 2008

Abstract— Exposure to artificial UV wavelengths and the UV component of sunlight delays positive phototaxis in the green alga Volvox aureus. Broad band wavelength filters were used to modify the output from UV‐B sources (280–320 nm) and natural sunlight. The delay in phototaxis by artificial UV is increased with exposure to shorter UV‐B wavelengths. Natural sunlight experiments were performed with exposure to full sunlight and to its UV component only. The UV component present in summer sunlight produced long periods of inhibition in phototaxis and even lethality, while exposure to the total spectrum of sunlight had no significant effects on movement or survival. The data indicate that although this species of alga is well equipped to deal with present levels of UV exposure, increases in the short UV‐B wavelengths in sunlight may force an alteration in patterns of photomovement.
SPONTANEOUS LOW‐LEVEL CHEMILUMINESCENCE FROM CHEMICAL AND ELECTROCHEMICAL OXIDATION OF β‐DEHYDRO NICOTINEAMIDE ADENINE DINUCLEOTIDE
Authors: Watanabe Nobuyuki , Inaba Humio
Published: January 2008

Abstract— Oxidation of β‐dehydro nicotineamide adenine dinucleotide (NADH) by oxygen catalyzed by horseradish peroxidase was accompanied by spontaneous, low‐level chemiluminescence in the existence of co‐oxidant 2,4‐dichlorophenol. Electrochemical oxidation of NADH by the glassy carbon electrode also emitted a spontaneous low‐level chemiluminescence above the potental +0.7 V vs reference electrode (Ag/AgCl) in aqueous medium in pH 7.0˜10.0. Low‐level electrochemilumin‐escence was observed when the NAD and oxygen species coexisted in the neighborhood of the electrode surface. The main photon emission process was supposed to be generated by the interaction of pyridine moiety of NAD and oxygen.
PHOTOCHEMISTRY OF HALOGEN PYRIMIDINES: IODINE RELEASE STUDIES
Authors: Rahn R. O.
Published: January 2008

Abstract— The feasibility of using direct iodide (I‐) measurements to monitor the photochemistry of the halogenated pyrimidines 5‐iodocytosine and 5‐iodouracil and their corresponding deoxynucleosides was examined. Radiation from either a germicidal lamp (Λ=254 nm) or a sunlamp (Λ>290 nm) was employed to induce homolytic splitting of the carbon‐iodine bond and the release of iodine atoms. These atoms combine to form I2 which reacts with water to ultimately form I‐ and iodate (10‐3). The formation of I‐ was followed using either high performance liquid chromatography with electrochemical detection or a specific ion electrode. 10‐3 was assayed spectroscopically following its conversion to triiodide. The yields of I‐ relative to starting material destroyed were either close to the theoretical limit of 83% or higher depending upon (a) the compound being irradiated, (b) the irradiation wavelength and (c) the extent of exposure. Yields of iodide >83% are generally accounted for by a concomitant reduction in the yield of iodate such that the sum I‐+ 10‐3 is approx. 100%. Because iodate is photochemically reduced to iodide by 254 nm but not sunlamp irradiation, exhaustive irradiation at 254 nm converts all of the iodate present to iodide. These studies have application to the use of photochemical methods for quantitating the percent substitution of iodinated pyrimidines in DNA, and should be useful in following the photochemistry of IdUrd and IdCyd substituted DNA.
REDOX REGULATION OF ENERGY TRANSFER EFFICIENCY IN ANTENNAS OF GREEN PHOTOSYNTHETIC BACTERIA
Authors: Blankenship Robert E. , Cheng Peiling , Causgrove Timothy P. , Brune Daniel C. , Wang Stephanie Hsiao‐Hsien , Choh Jin‐Ug , Wang Jian
Published: January 2008

The efficiency of energy transfer from the peripheral chlorosome antenna structure to the membrane‐bound antenna in green sulfur bacteria depends strongly on the redox potential of the medium. The fluorescence spectra and lifetimes indicate that efficient quenching pathways are induced in the chlorosome at high redox potential. The midpoint redox potential for the induction of this effect in isolated chlorosomes from Chlorobium vibrioforme is ‐146 mV at pH 7 (vs the normal hydrogen electrode), and the observed midpoint potential (n = 1) decreases by 60 mV per pH unit over the pH range7–10. Extraction of isolated chlorosomes with hexane has little effect on the redox‐induced quenching, indicating that the component(s) responsible for this effect are bound and not readily extractable. We have purified and partially characterized the trimeric water‐soluble bacteriochlorophyll a‐containing protein from the thermophilic green sulfur bacterium Chlorobium tepidum. This protein is located between the chlorosome and the membrane. Fluorescence spectra of the purified protein indicate that it also contains groups that quench excitations at high redox potential. The results indicate that the energy transfer pathway in green sulfur bacteria is regulated by redox potential. This regulation appears to operate in at least two distinct places in the energy transfer pathway, the oligomeric pigments in the interior of the chlorosome and in the bacteriochlorophyll a protein. The regulatory effect may serve to protect the cell against superoxide‐induced damage when oxygen is present. By quenching excitations before they reach the reaction center, reduction and subsequent autooxidation of the low potential electron acceptors found in these organisms is avoided.
SPECTROSCOPIC PROPERTIES OF THE POTENTIOMETRIC PROBE MEROCYANINE‐540 IN SOLUTIONS AND IN LIPOSOMES
Authors: Ehrenberg Benjamin , Pevzner Eliyahu
Published: January 2008

Absorption, fluorescence and resonance Raman spectra of the membrane dye merocyanine‐540 (MC540) were measured. The aggregation of the dye, its binding to lipid membranes and its response to crossmembrane electric potential differences were studied. The dye was found to aggregate even at micromolar concentrations in water, but not in organic solvents. The dimerization constant was evaluated by spectroscopic techniques. The binding constant to liposomes was estimated by a spectroscopic titration method. Resonance Raman spectra of MC540 were measured for the first time. Distinct changes were observed in the vibrational spectrum upon the generation of a valinomycin‐induced K+ diffusion potential (Nernst potential) on liposomes. The ratio of Raman band intensities, which was found to be related to the membrane potential, can be used to evaluate the absolute value of the electric potential.
DEVELOPMENT OF AN in vitro SYSTEM FOR THE ANALYSIS OF ULTRAVIOLET RADIATION‐INDUCED SUPPRESSION OF NATURAL KILLER CELL ACTIVITY
Authors: Hersey Peter , Magrath Helene , Wilkinson Frank
Published: January 2008

Previous studies have shown that natural killer (NK) cell activity was suppressed in volunteer subjects exposed to ultraviolet radiation (UVR) from solarium lamps. The present studies were carried out to determine that spectrum of UVR responsible for suppression of NK activity and to develop in vitro methods to analyze the effectivenes of sunscreen agents in prevention of UVR‐mediated suppression of NK activity and other aspects of immune function. UVR from a xenon are lamp source was used to irradiate peripheral blood lymphocytes (PBL) in wells of tissue culture flasks, and transmission interference filters were used to eliminate UVR of particular wavelengths. The results indicated that UVR from this source inhibited NK activity of PBL in a dose‐dependent manner with a 50% inhibitory dose of 5.5 mJ/cm2 when unfiltered and 29.6 mJ/cm2 when diluted through cellulose acetate, which gave a UV spectrum similar to that in solar radiation. Equivalent suppression of NK activity was mediated by UV‐A (UVR > 315 nm) at dose levels of 4.2 J/cm2, which was approximately 140 times greater than the amount of UV‐B (UVR > 315 nm) needed to suppress NK activity. Similar dose‐response curves were seen for inhibition of mitogenic responses to phytohemagglutinin except that the latter appeared less sensitive than NK to inhibition by UV‐A. These studies suggest that whe the greater proportion of UV‐A in solar radiation adn its greater penetration into skin is taken into account, UV‐A may have equivalent or greater direct immunosuppressive effects than UV‐B. The mechanisms of their immunosuppressive effects may, however, differ. The in vitro system described here would appear to provide a simple test system for further analysis of UVR‐indued imunosuppression.
THE ROLE OF LIPOPROTEINS IN THE DISTRIBUTION OF TIN ETIOPURPURIN (SnET2) IN THE TUMOR‐BEARING RAT
Authors: Kessel David , Garbo Greta M. , Hampton James
Published: January 2008

The role of plasma lipoproteins in the distribution of the photosensitizing agent tin etiopurpurin (SnET2) was examined in male rats bearing the N‐[4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl]formamide‐induced tumor. Treatement with 17α‐ethinyl estradiol resulted in the depletion of total plasma cholesterol by > 70% and a corresponding decrease in plasma lipoproteins. To both control and estradiol‐treated animals, a therapeutic dose (1.5mg/kg) of SnET2 was administered and biodistribution measured 24 h later. Estradiol treatment was not associated with difference in the distribution of SnET2 to liver, skin or tumor, or in the pattern of affinity of SnET2 to plasma albumin and lipoprotein. These results indicate that a substantial decrease in circulating lipoprotein levels does not alter patterns of SnET2 biodistribution.
USE OF SENSITIZED FLUORESCENCE FOR THE STUDY OF THE EXCHANGE OF SUBUNITS IN PROTEIN AGGREGATES*
Authors: Erijman Leonardo , Weber Gregorio
Published: January 2008

The 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

Photosensitized 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.
PHOTOCYTOTOXICITY OF WATER‐SOLUBLE METALLOPORPHYRIN DERIVATIVES
Authors: Ando Tomoyuki , Irie Kazuhiro , Koshimizu Koichi , Takemura Takeshi , Nishino Hoyoku , Iwashima Akio , Takeda Naohito , Nakajima Susumu , Sakata Isao
Published: January 2008

Abstract— A new water‐soluble porphyrin derivative, 2,4‐bis(1‐decyloxyethyl)‐deuteroporphyrinyl–6,7‐bisaspartic acid(C–10‐DP), and its metal complexes (Ga, In, Sn, Zn, Mn, Cu, Ni and Fe) were examined for their physicochemical properties (absorption, fluorescene, triplet lifetime and partition coefficient) and photocytotoxicity on HeLa cells. The five derivatives with longer(>1ms) triplet lifetimes (free base, Zn, Ga, In and Sn complexes) exhibited remarkable photocytotoxicity, and the other derivatives (Mn, Cu, Ni and Fe), which had or were deduced to have fairly short (<0.01 ms) triplet lifetimes, manifested no photocytotoxicity, indicating that the triplet lifetime of these derivatives played a significant role in their photocytotoxicity. Cellular fluorescence due to C10‐DP and its gallium complex was observed mainly on the plasma membrane at the concentrations showing significant photocytotoxicity with low (<32.6%) cytotoxicity in the dark(2–10 μM).
BIOLOGICAL ACTIVITIES OF PHTHALOCYANINES. XIII. THE EFFECTS OF HUMAN SERUM COMPONENTS ON THE in vitro UPTAKE AND PHOTODYNAMIC ACTIVITY OF ZINC PHTHALOCYANINE
Authors: Obochi M. O. K. , Boyle R. W. , Lier J. E. van
Published: January 2008

Abstract— The effect of human serum components on the photodynamic activity of zinc phthalocyanine (ZnPc) toward Chinese hamster fibroblasts (lineV–79) was studied. Photodynamic activities were correlated with cellular uptake of radiolabeled [65Zn]ZnPc, which allowed corrections to be made for the amount of sensitizer present in the cells at the time of irradiation and to express photodynamic efficiences on a cellular dye concentration basis. All serum components, with the exception of high‐density lipoproteins, inhibit uptake of ZnPc byV–79 cells, when compared to incubation of ZnPc with the same cells in serum‐free medium. High‐density lipoproteins increased ZnPc uptake by 23%, but the photodynamic efficiency corrected for the cellular ZnPc concentration was unaffected. Very low‐density lipoprotein and globulins decreased ZnPc cell uptake but likewise did not affect the cellular photodynamic efficiency of the dye. In contrast low‐density lipoprotein and albumin, while inhibiting ZnPc cell uptake, increased the cellular photodynamic efficiency of ZnPc, suggesting that these proteins facilitate localization of the dye at cellular targers sensitive to photodynamic damage and vital to cell survival. We conclude from these results that association of ZnPc with serum components can have important, and widely differing, effects on both degree of uptake and cellular distribution of the photosensitizer.
A PHYTOCHROME STUDY USING TWO‐LASER/TWO‐COLOR FLASH PHOTOLYSIS: I700 IS A MANDATORY INTERMEDIATE IN THE PrPfr PHOTOTRANSFORMATION
Authors: Scurlock Rodger D. , Braslavsky Silvia E. , Schaffner Kurt
Published: January 2008

Abstract— The phototransformation of native (124 kDa)oat phytochrome, Pr Pfr, Has been studied at 10d̀C by two laser/ two‐color flash photolysis. the overall PrPfr reaction yield did not vary with temperature within the range4–21d̀C. Foloeing the excitation of Pr with a single 15 ns laser flash at 650nm, the formation of Pfr was quantitavely measured in a time‐resolved experiment in the presence of a second 8 ns laser flash at 710 nm delayed from the initial flash. the second laser flash causes at 1.0 s after the initial laser flash a depletion of the uintermediate I700 as welll as a reduction of the Pfr absorption at 730 nm. The depletion of I700 correlates quantitavely with the reduction of Pfr formation. The absorpton spectra of I700 and of the following intermendiate, Ibi, were calculated assuming that the amount of Pr, which is photoconverted by a single laser, equals the amount of Pfr formed.