bluuebunny/crossref_metadata_2025 huggingface dataset:
ISOMERIZATION OF THE RETINYLIDENE CHROMOPHORE OF BACTERIORHODOPSIN IN LIGHT ADAPTATION: INTRINSIC ISOMERIZATION OF THE CHROMOPHORE AND ITS CONTROL BY THE APO‐PROTEIN
Authors: Koyama Yasushi , Nakasu Hiroaki , Mukai Yumiko , Tokunaga Fumio
Published: January 2008

Abstract— The dependence of the isomeric configuration of the retinylidene chromophore of bacteriorhodopsin on the pH value and on the wavelength of irradiation (in a photostationary state) were examined by high performance liquid chromatographic analyses of extracted retinal. The process of isomerization of the chromophore during light adaptation was also traced. More than 93% of all‐trans and less than 5% of 13‐cis retinal were extracted in the photostationary state for irradiation at 560 nm in the pH region of5–9 as well as for irradiation in the wavelength region of 400–650 nm at pH 7. Comparison of the above photostationary state composition with that of protonated n‐butylamine Schiff base of retinal indicates that strong constraint is applied to the chromophore by the apo‐protein. The constraint can be changed at low or high pH by a partial denaturation or transition of the apo‐protein, which results in the generation of 11‐cis retinal in the extract. At higher photon density, the isomerization process of the chromophore during light adaptation at pH 7 was characterized, as extracted isomeric retinal, by (1) the initial decrease in 13‐cis and increase in all‐trans, (2) a subsequent, transient toward the above photostationary state composition. The results are discussed in terms of both the photoisomerization pattern inherent in the retinylidene chromophore and the control by the apo‐protein.
POTENTIAL ERRORS IN THE USE OF CELLULOSE DIACETATE AND MYLAR FILTERS IN UV‐B RADIATION STUDIES
Authors: Middleton Elizabeth M. , Teramura Alan H.
Published: January 2008

Abstract— The increase in UV‐B radiation(290–320 nm) penetrating to the earth's surface as a result of the chemical depletion of the stratospheric ozone layer is an important environmental concern. In most studies using artificial UV‐B sources, the determination of enhanced UV‐B radiation effects on plants relies on equivalent UV‐A radiation(320–400 nm) from the experimental UV‐B fluorescent lamp source, filtered with either cellulose diacetate (CA) to create UV‐B treatments, or with type S Mylar or polyester (PE) to create controls (no UV‐B). The spectral irradiance in the UV‐A was measured in the dark below lamps at two daily UV‐B irradiance levels (14.1 and 10.7 W m‐2) with CA and PE at two ages. Highly significant differences in UV‐A radiation (P 0.01) were measured below the treatment/control pairs at both fluence rates and filter ages. Filter aging was observed, which reduced the UV‐A irradiance, especially for PE. The total daily ambient UV‐A irradiance was also determined in the glasshouse at three seasons: the fall equinox, summer and winter, from which the total daily UV‐A (lamp + ambient) irradiances were calculated. The addition of low to moderate ambient irradiance removed the treatment/control differences in the longwave UV‐A(350–400 nm); however, the treatment/contro1 differences remained in the shortwave UV‐A(320–350 nm), which was restricted by the glass, and in the total UV‐A. The treatment/control differences persisted in the shortwave UV‐A for the higher irradiance level, even under high summer ambient light. Also, spectral ratios (UVB:UV‐A and shortwave: longwave UV‐A) for all treatment groups decreased as the ambient UV‐A radiation increased. Therefore, a range of experimental conditions exist where PE‐covered lamps do not provide adequate control for UV‐A irradiance, relative to the CA treatment, for glasshouse/growth chamber experiments. Potential complications in the interpretation of plant response exist for UV‐B experiments conducted under low ambient light conditions (e.g. growth chambers; glasshouse in winter) or high daily UV‐B irradiances (e.g. 14 kJ m‐2) for those plant responses that are sensitive to UV‐A radiation.
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

Experiments 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

In 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

The 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

The 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

The 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

Delayed 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.
BOOK REVIEW
Authors: Magnus I. A.
Published: January 2008

Book Review in This Article:

Biological Responses to Ultraviolet A Radiation, edited by Fredrich Urbach.
QUANTUM YIELDS AND SECONDARY PHOTOREACTIONS OF THE PHOTOPRODUCTS OF dTpdT, dTpdC AND dTpdU
Authors: Lemaire DanielleG. E. , Ruzsicska Bela P.
Published: January 2008

Abstract— The photoproducts of the dinucleoside monophosphates, dTpdT, dTpdC and dTpdU, have been purified by high performance liquid chromatography and characterized by UV absorption spectroscopy, fast atom bombardment mass spectrometry and by secondary thermal and photoreactions. Four types of photoproducts were analyzed: (1) cyclobutane dimers including cis‐syn isomers and two diastereomers of the trans‐syn isomers; (2) 6‐4 photoadducts and the corresponding Dewar valence isomers; (3) photohydrates comprising two diastereomers and (4) a new photoproduct resembling nucleobase amine adducts, which occurs only for dTpdC. The quantum yields of formation of these photoproducts and for some secondary photoreactions were measured by kinetic analysis of the photoproduct yield as a function of photon fluence. These results indicate that cis‐syn cyclobutane dimers are the photoproducts formed with highest efficiency with dT[p]dC dimers being formed with 50–75% the efficiency of dT[p]dT dimers. The 6‐4 photoadducts are formed with 5–10% the efficiency of cis‐syn cyclobutane dimers and the 6‐4 photoadduct of dTpdC is formed two to three times more efficiently than that of dTpdT. Photohydrates are also formed efficiently due to an equilibrium between stacked and unstacked complexes of the dinucleoside monophosphates. It is shown that three of these photoproducts, namely the cyclobutane dimers of dTpdC, the 6‐4 photoadducts and the possible nucleobase amine adduct, undergo photolysis in the UV‐B region resulting in either photoreversion or secondary photoreaction.
QUANTUM YIELDS AND SECONDARY PHOTOREACTIONS OF THE PHOTOPRODUCTS OF dTpdT, dTpdC AND dTpdU
Authors: Lemaire Danielle G. E. , Ruzsicska Béla P.
Published: January 2008

Abstract— The photoproducts of the dinucleoside monophosphates, dTpdT, dTpdC and dTpdU, have been purified by high performance liquid chromatography and characterized by UV absorption spectroscopy, fast atom bombardment mass spectrometry and by secondary thermal and photoreactions. Four types of photoproducts were analyzed: (1) cyclobutane dimers including cis‐syn isomers and two diastereomers of the trans‐syn isomers; (2) 6‐4 photoadducts and the corresponding Dewar valence isomers; (3) photohydrates comprising two diastereomers and (4) a new photoproduct resembling nucleobase amine adducts, which occurs only for dTpdC. The quantum yields of formation of these photoproducts and for some secondary photoreactions were measured by kinetic analysis of the photoproduct yield as a function of photon fluence. These results indicate that cis‐syn cyclobutane dimers are the photoproducts formed with highest efficiency with dT[p]dC dimers being formed with 50–75% the efficiency of dT[p]dT dimers. The 6‐4 photoadducts are formed with 5–10% the efficiency of cis‐syn cyclobutane dimers and the 6‐4 photoadduct of dTpdC is formed two to three times more efficiently than that of dTpdT. Photohydrates are also formed efficiently due to an equilibrium between stacked and unstacked complexes of the dinucleoside monophosphates. It is shown that three of these photoproducts, namely the cyclobutane dimers of dTpdC, the 6‐4 photoadducts and the possible nucleobase amine adduct, undergo photolysis in the UV‐B region resulting in either photoreversion or secondary photoreaction.
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.
NUCLEOTIDE EXCISION REPAIR
Authors: Sancar Aziz , Tang Moon‐shong
Published: January 2008

Abstract— Nucleotide excision repair is the major DNA repair mechanism in all species tested. This repair system is the sole mechanism for removing bulky adducts from DNA, but it repairs essentially all DNA lesions, and thus, in addition to its main function, it plays a back‐up role for other repair systems. In both pro‐ and eukaryotes nucleotide excision is accomplished by a multisubunit ATP‐dependent nuclease. The excision nuclease of prokaryotes incises the eighth phosphodiester bond 5' and the fourth or fifth phosphodiester bond 3' to the modified nucleotide and thus excises a 12–13‐mer. The excision nuclease of eukaryotes incises the 22nd, 23rd, or 24th phosphodiester bond 5' and the fifth phosphodiester bond 3' to the lesion and thus removes the adduct in a 27–29‐mer. A transcription repair coupling factor encoded by the mfd gene in Escherichia coli and the ERCC6 gene in humans directs the excision nuclease to RNA polymerase stalled at a lesion in the transcribed strand and thus ensures preferential repair of this strand compared to the nontranscribed strand.
A CHARACTERIZATION OF THE FLUORESCENT PROPERTIES OF CIRCULATING HUMAN EOSINOPHILS
Authors: Barnes Dan , Aggarwal Shanti , Thomsen Sharon , Fitzmaurlce Maryann , Richards‐Kortum Rebecca
Published: January 2008

Abstract— This paper presents a characterization of the fluorescence properties of human eosinophils isolated from peripheral blood of normal donors over a wide range of excitation and emission wavelengths. Circulating eosinophils possess three fluorescence excitation emission maxima: one at 280 nm excitation, 330 nm emission, attributable to tryptophan fluorescence, and currently unassigned peaks at 360 nm excitation, 440 nm emission and 380 nm excitation, 415 nm emission. Fluorescence microscopy studies show that the Huorescence of eosinophils may be site dependent; specifically, when observed at 365 nm excitation, circulating eosinophil Huorescence appears blue‐violet, while the fluorescence of tissue‐dwelling eosinophils appears amber‐gold. These results should be considered in developing an optical biopsy technique to identify eosinophils in human tissue.
DYE‐SENSITIZED DESTABILIZATION OF LIPOSOMES BEARING PHOTOOXIDIZABLE LIPID HEAD GROUPS
Authors: Chowdhary Rubinah K. , Green Christopher A. , Morgan Christopher G.
Published: January 2008

Abstract— Liposomes were prepared from mixtures of dipalmitoyl‐i.‐α‐phosphatidylcholine and up to 40% mol:mol of N‐stearoyl‐L‐histidine (NSH) in the presencc or the hydrophobic sensitizer DHE. In the dark such liposomes are stable and retain entrapped salts. On photolysis with visible light, liposomes leak trapped ions at NSH concentrations greater than 10% mol:mol. Up to 15% mol:mol NSH concentration leakage is seen only during the illumination period, whereas at higher concentration the liposomes continue to leak contents after illumination and fuse to form larger structures. Photolysis of the liposomes is accompanied by oxygen uptake in proportion to the NSH concentration within the bilayer. Photocontrol of liposome permeability through oxidation of membrane additives such as NSH offers a potential means for controlled drug delivery and might he useful as an adjunct to photodynamic therapy.
FREQUENCY OF ULTRAVIOLET RADIATION‐INDUCED MUTATION AT THE hprt LOCUS IN REPAIR‐PROFICIENT MURINE FIBROBLASTS TRANSFECTED WITH THE denV GENE OF BACTERIOPHAGE T4
Authors: Kusewitt Donna F. , Budge Cindy L. , Anderson Mary M. , Ryan Sharon L. , Ley Ronald D.
Published: January 2008

Abstract— Thc frequency of spontaneous and ultraviolet radiation (UVR)‐induced mutation at the hprt locus was determined in control and denV‐transfected, repair‐proficient murine fibroblasts. Control cells removed an average of 25% of pyrimidine dimers induced by exposure to 150 J/m2UVR from an FS40 sunlamp within 24 h; under the same conditions of induction and repair, denV‐transfected cells removed an average of 71% of pyrimidine dimers. Control cells were somewhat more resistant than denV‐transfected cells to killing by UVR. The average frequency of spontancous mutation at the hprt locus for control and denV‐transfected cells was 3 and 15 6‐thioguanine (6‐TG)‐resistant colonies per 106 surviving cells, respectively; there was no statistically significant difference between control and dcnV‐transfected cells. However, after exposure to 75 or 150 J/m2 UVR, denV‐transfected cells had a significantly lower frequency of mutation to 6‐TG resistance. After exposure to a fluence of 75 J/m2, the average frequency of UVR‐induced mutation at the hprt locus was 166 mutant colonies per loh surviving cells for control cells and 92 mutant colonies for denV‐transfectcd cells; after 150 J/m2, control cells had 205 6‐TG‐resistant colonies per 106 cells, while dmV‐transfected cclls had 61 mutant colonies. These results demonstrate that UVR‐induced pyrimidine dimers are mutagenic photoproducts in mammalian cells.
STRUCTURAL DIFFERENCES BETWEEN PHYCOCYANIN and ALLOPHYCOCYANIN FROM THEIR RESONANCE RAMAN SPECTRA*
Authors: Szalontai B. , Gombos Z. , Lutz M.
Published: January 2008

Abstract— Resonance Raman spectra of the chromophores of the cyanobacterial light‐harvesting proteins phycocyanin (CPC) and allophycocyanin (APC) were recorded using 364 nm excitation. The1500–1700 cm‐1 regions of these spectra were analyzed for the pH‐induced structural changes accompanying the disruption of the native trimers into monomers as well as the progressive denaturation of these monomers. Computer‐assisted decomposition of the 1642 cm‐1 marker bands of these spectra yielded up to four components (named I‐IV), the frequencies of which were constant within 5 cm‐1 (CPC) and 10 cm‐1 (APC). The relative intensities of two of these components, namely I and III, were sensitive to chromophore conformations. The previously reported downshift of the 1642 cm‐1 band upon folding of the chromophores was shown to result from a weakening of component I and a concomitant enhancement of component III. Components I‐IV had different relative intensity patterns in CPC and APC spectra. In particular, the higher relative intensity of component I at 1646 cm‐1 indicated more extended average conformations of the chromophores in trimeric APC than in trimeric CPC. This difference likely resulted from the extra β‐155 chromophore present in CPC. Component III was sizably active in RR spectra of monomelic APC but was not observed either in those of monomelic CPC or in those of trimeric APC and CPC. This indicated that, in APC monomers, chromophore(s) did not assume the native conformations found in the trimer, while monomer formation did not sizably alter the structures of the CPC chromophores.
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

A 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

Chlorophyll (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.
PHOTOLYSIS OF INTACT YOUNG HUMAN, BABOON AND RHESUS MONKEY LENSES
Authors: Ellozy A. R. , Wang R. H. , Dillon J.
Published: January 2008

Abstract Intact young human, baboon and rhesus monkey lenses were subjected to near‐UV irradiation under identical conditions and fluorophore buildup was continuously monitored for several hours. The compositional changes occurring in the lenses were monitored by analyzing the ethanol extracts of the irradiated and control lenses using high‐performance liquid chromatography and thin‐layer chromatography (TLC). The chromatograms of the supernatant detected at 365 nm as well as the TLC scans showed the presence of 3‐hydroxykynurenine glucoside (3‐HKG) and two other kynurenine‐type compounds. The 3‐HKG and one of the compounds were found in all three species, while the remaining one was structurally different in the lower primates. A loss of 3‐HKG as a result of irradiation was apparent in all the lenses and correlated with the buildup of the blue fluorophore, suggesting that the latter may be a photoproduct(s) of 3‐HKG. The kinetic analysis of baboon and human lenses showed a slowdown in the fluorophore buildup as irradiation times increased. This was probably due to the competitive absorptions of 3‐HKG and other chromophores present. Rhesus monkey lenses did not exhibit this slowdown.
UV‐B‐INDUCED INCREASE IN SPECIFIC LEAF WEIGHT OF CUCUMBER AS A CONSEQUENCE OF INCREASED STARCH CONTENT
Authors: Britz Steven J. , Adamse Paulien
Published: January 2008

Abstract Specific leaf weight (SLW), the ratio of leaf dry matter to area, often increases in plants exposed to elevated UV‐B radiation (280–315 nm). Increased SLW can result from greater leaf thickness or increased leaf density (e.g. accumulation of high density substances in cells). The basis for large increases in SLW was examined in the first and third leaves of cucumber differing in developmental stage at the start of UV treatment. Leaf 1 was approximately 50% fully expanded, while leaf 3 had just unfolded. It is shown here that up to 80% of the UV‐generated change in SLW in leaf 1 was caused by accumulation of nonstructural carbohydrates, especially starch (increasing from 13 to 23% of total dry weight). Leaf 3 contained a much smaller proportion of nonstructural carbohydrates (less than 8%) and the effect on SLW was correspondingly less. As shown in the previous paper, UV‐B inhibition of growth in leaf 3 was reversed by supplemental blue light (BL) in a fluence‐dependent manner between 0.23 to 2.68 mol m 2 perday. Fluence‐response curves revealed that supplemental BL reversed both the UV‐induced accumulation of starch and increase in SLW in leaf 1 over the same range. The data are consistent with a back‐up of photosynthate into leaf 1 as a result of UV‐B inhibition of growth in leaf 3. The data also demonstrate that increases in SLW cannot be assumed to represent increases in leaf thickness.
ENHANCEMENT OF NILE BLUE DERIVATIVE‐INDUCED PHOTOCYTOTOXICITY BY NIGERICIN AND LOW CYTOPLASMIC pH
Authors: Lin Chi‐Wei , Shulok Janine R.
Published: January 2008

Abstract The mechanism of photocytotoxicity mediated by a lysosomotropic photosensitizer, Nile blue derivative (NBS‐61), in relation to lysosome destruction was examined by lowering the intracellular pH with low extracellular pH and an ionophore, nigericin. The treatment performed after photoirradiation had minimal effect on the cytotoxicity. However, when the treatment was initiated before photoirradiation, it caused a three orders of magnitude enhancement on cytotoxicity with a two orders of magnitude enhancement by nigericin alone. This effect on cytotoxicity resembles closely that observed on photosensitization mediated by chloroaluminum phthalocyanine. The enhancement in this case has been attributed to the synergistic interaction between photodamage and perturbation of ion transports across mitochondrial or plasma membranes by nigericin. Because these are not the main sites of localization for Nile blue photosensitizers nor their initial targets of photocytotoxic action, data from the present study suggest the possibility of an intracellular dye translocation induced by nigericin, which redistributes the Nile blue photosensitizer from lysosomes to other sites, as a possible cause of the enhancement of cytotoxicity.
LASER PHOTOLYSIS OF THE PURPLE MEMBRANE OF Halobacterium halobium IN THE PHOTOSTATIONARY STATE: THE PHOTOBRANCHING PROCESS FROM THE O640 INTERMEDIATE
Authors: Ohtani Hiroyuki , Naramoto Satoru , Yamamoto Noritaka
Published: January 2008

Abstract The photobranching process from the O640 intermediate (O) in the photocycle of bacteriorhodopsin was studied. The O form accumulated with continuous wave visible light (390–800 nm) irradiation of the acidic (pH 3.9–6.0) purple membrane of Halobacterium halobium at 22°C. The photocycle of O via an L‐like (or N‐like) intermediate was driven by 630 nm pulsed light. The newly found intermediate has an absorption band in the 450–560 nm region. The “green‐light”‐absorbing pigment, tentatively called G520, was converted to O with a time constant of (1.2 ± 0.2) ms. No M‐like species was found in the cycle. The quantum yield of the cycle was estimated to be 0.30 ± 0.15.
SPECTROSCOPY AND PHOTOSENSITIZATION OF SAPPHYRINS IN SOLUTIONS AND BIOLOGICAL MEMBRANES
Authors: Roitman Leonid , Ehrenberg Benjamin , Nitzan Yeshayahu , Kral Vladimir , Sessler Jonathan L.
Published: January 2008

Abstract A spectroscopic and photophysical study of three new sapphyrin molecules is presented. The sapphyrin backbone that was derivatized to make them water soluble possesses an absorption band around 700 nm, a desired property for biological photosensitization. We studied the absorption and fluorescence spectra, from which evidence for aggregation in solvents of different polarities was obtained. The extent of aggregation is correlated with the nature of the attached moiety. The absolute quantum yields of singlet oxygen production were measured, with 1,3‐diphenyl isobenzofuran as a model target, and were 0.13–0.18 in ethanol. The binding constants to liposomes and to cells were determined spectroscopically and were found to correspond to the hydrophobicities of the compounds, with an additional effect, ascribed to the sugar moiety, which was found in the case of one of the sapphyrins. The efficiency of photodamage to Staphylococcus aureus by sapphyrins and hematoporphyrin was equivalent, on the basis of cells killed per microgram of sensitizer in the incubation mixture.
PHOTOCHEMISTRY OF 2‐MERCAPTOPYRIDINES. PART 1. AN EPR AND SPIN‐TRAPPING INVESTIGATION USING 5,5‐DIMETHYLl‐PYRROLINE N‐OXIDE IN AQUEOUS AND TOLUENE SOLUTIONS*
Authors: Reszka Krzysztof J. , Chignell Colin F.
Published: January 2008

Abstract We have employed EPR and the spin trap 5,5‐dimethyi‐1‐pyrroline N‐oxide (DMPO) to investigate the photochemistry of pyridine‐2‐thione (2‐S‐PyrH), N‐hydroxypyridine‐2‐thione (2‐S‐PyrNOH), and its sodium salt, (2‐S‐PyrNONa), and disulfides, 2,2′‐dithiobis (pyridine N‐oxide) [(2‐S‐PyrN→O)2] and 2,2′‐dithiodipyridine [(2‐S‐Pyr),]. We have found that upon UV irradiation they generate aromatic thil radicals, 2–'SPyr and 2–'S‐PyrN → O, detected as DMPO adducts, DMPO/2–'S‐Pyr (1) and DMPO/2–'S‐PyrN→O (2). In aqueous solution (pH 7) hyperfine splitting constants (hfsc) were determined to be for 1: aN= 14.92 G, aHβ= 16.57 G, and for 2: aN= 14.78 G, aHβ= 16.05 G. In toluene hfsc were 13.09 G, 13.93 G for 1, and 13.25 G, 12.04 G for 2. Irradiation of 2‐S‐PyrH and DMPO in aerated pH 7 buffer generated the DMPO/‐O2,‐ radical (3a, aN= 14.10 G, aHβ= 11.40 G, aHγ= 1.18 G), while in aerated toluene DMPO/.O2H was formed (adduct 3b, aN= 12.74 G, aHβ= 10.41 G, aHγ= 1.295 G). In both systems adduct 1 was also observed. Because compounds possessing the pyridine‐2‐thione moiety show antifungal, antibacterial and anticancer properties, it is likely that the ability to photogenerate free radicals may be pertinent to their biological activity.
PHOTOCHEMISTRY OF 2‐MERCAFTOPYRIDINES. PART 2. AN EPR AND SPIN‐TRAPPING INVESTIGATION USING 2‐METHYL‐2‐NITROSOPROPANE AND aci‐NITROMETHANE AS SPIN TRAPS IN AQUEOUS SOLUTIONS*
Authors: REszka Krzysztof J. , Chignell Colin F.
Published: January 2008

Abstract Compounds possessing a pyridine‐2‐thione moiety show antimicrobial, antifungal and anticancer activities. Some of them are also photochemically active and upon UV irradiation generate free radicals. In this work, employing EPR and the spin traps 2‐methyl‐2‐nitrosopropane (MNP) and aci‐nitromethane (NM), we investigated the photochemistry in aqueous solutions of N‐hydroxypyridine‐2‐thione (used here as a sodium salt, 2‐S‐PyrNONa), and pyridine‐2‐thione (2‐S‐PryH), as well as photochemistry of the respective disulfides, 2,2′‐dithiobis(pyridine N‐oxide) [(2‐S‐PyrN→O)2] and 2,2′‐dithiodipyridine [(2‐S‐Pyr)2]. We found that UV irradiation of 2‐S‐PyrNONa and of 2‐S‐PyrH in the presence of MNP and NM generates EPR signals of reduced spin traps in addition to signals of MNP and NM adducts with aryl‐thiyl radicals, 2–.S‐PyrN→O and 2–.S‐Pyr. The identification of the aromatic thiyl radicals was based on comparison of EPR spectra of spin adducts generated by irradiation of 2‐S‐PyrNONa and 2‐S‐PyrH with those produced by UV photolysis of the respective disulfides (2‐S‐PyrN→O), and (2‐S‐Pyr)2. It is concluded that pyridine‐2‐thione and N‐hydroxypyridine‐2‐thione possess a photoreducing capacity and generate aromatic thiyl radicals upon UV activation. This property may be relevant to biological action of agents containing the pyridine‐2‐thione moiety.
PHOTOACTIVE TERTHIOPHENES: THE INFLUENCE OF SERUM ON ANTI‐HIV (HUMAN IMMUNODEFICIENCY VIRUS) ACTIVITIES
Authors: Yoshimura Kenjiro
Published: January 2008

Abstract Responses of Chlamydomonas to light, such as phototaxis and photophobic response, are thought to depend on a phototransduction process involving rhodopsin and a calcium ion influx at the eyespot. To assess the direction of the chromophore orientation within the eyespot, I measured the membrane current in cells captured by a suction pipette upon stimulation with polarized light. When the cells were stimulated with polarized light incident parallel to the membrane overlying the eyespot, the photoreceptor current was found to change with the direction of the e‐vector. The current was maximum when the e‐vector was parallel to the eyespot membrane and minimal when perpendicular. When the cells were stimulated with light incident perpendicular to the eyespot membrane, the photoreceptor current did not change with the direction of the e‐vector. These results suggest that the chromophore is located in the eyespot and oriented almost parallel to the plane of the membrane of the eyespot. Thus the direction of the chromophore orientation in Chlamydomonas rhodopsin with respect to the membrane is the same as in rhodopsins from bacteria and animals.
COMPARISON OF THE SOLID‐MATRIX LUMINESCENCE PROPERTIES and PHOTOPHYSICAL PARAMETERS OF TWO PRODUCTS FROM BENZO(a)PYRENE‐DNA ADDUCTS
Authors: Chu Yu , Hurtubise Robert J.
Published: January 2008

Abstract The solid‐matrix luminescence properties and several calculated photophysical parameters of two important products from the benzo(a)pyrene‐DNA adducts were compared. The products were benzo(a)pyrene‐r‐7,t‐8,9,c‐10‐tetrahydrotetrol (I‐1) and 7R,8S,9S‐trihydroxy‐10R‐(Ap‐deoxyguanosyl‐3′‐phosphate)‐7,8,9,1O‐tetrahydroben‐zo(a)pyrene (BPDE‐dG). The solid‐matrix luminescence data were obtained for 1–1and BPDE‐dG adsorbed on two different solid matrices, namely, 1% a‐cyclodextrin (CD)/NaCl and 25% trehalose/NaCl and at two different temperatures (93 K and 296 K). The 25% trehalose/NaCl gave higher fluorescence and phosphorescence quantum yields from both 1–1and BPDE‐dG in contrast to the 1%α‐CD/NaCl matrix. The BPDE‐dG showed lower fluorescence quantum yields on the solid matrices compared to 1–1. The lower fluorescence quantum yields for BPDE‐dG were attributed to a photoinduced electron transfer mechanism. In contrast to the room‐temperature solution fluorescence of BPDE‐dG, BPDE‐dG gave rather high fluorescence quantum yields at room temperature when adsorbed on the two solid matrices. From solid‐matrix luminescence quantum yields and solid‐matrix luminescence lifetimes, many photophysical parameters were calculated and compared. Several differences among the rate constants were noted with the two solid matrices for BPDE‐dG and 1–1. For example, BPDE‐dG showed internal conversion at 296 K with 25% trehalose/NaCl, but no internal conversion was observed at 93 K with this solid matrix. Also, for BPDE‐dG the phosphorescence rate constants at 296 K and 93 K. were very small with 25% trehalose/NaCl, but the intersystem crossing rate constants from the triplet state to the ground state were very large. The results from this work show how solid‐matrix luminescence can be employed to obtain unique luminescence information from the 1–1and BPDE‐dG systems.
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.
MOLECULAR CLONING OF THE HUMAN GENE SUVCC1 ASSOCIATED WITH THE REPAIR OF NONDIMER DNA DAMAGE INDUCED BY SOLAR UV RADIATION
Authors: Rosenstein Barry S. , Vaslet Charles A. , Rosenstein Rebecca B.
Published: January 2008

Abstract— A mutant cell line, DRP 287, sensitive to solar UV radiation and deficient in the repair of solar UV‐induced nondimer DNA damage, was derived from ICR 2A frog cells. These cells were transfected with human DNA and a secondary transformant obtained in which normal solar UV sensitivity was restored and the repair defect corrected. The DNA from this secondary transformant was used to construct a genomic DNA library from which a recombinant phage was isolated containing the human gene capable of restoring normal solar UV sensitivity and correcting the repair defect in the DRP 287 cells. This represents the first human gene which has been isolated that is specifically involved in the repair of nondimer DNA damage induced by solar UV radiation. It has been designated SUVCC1 to denote solar UV cross‐complementing gene number 1.
OZONE AND ULTRAVIOLET‐B IRRADIANCES: EXPERIMENTAL DETERMINATION OF THE RADIATION AMPLIFICATION FACTOR
Authors: Blumthaler Mario , Salzgeber Michael , Ambach Walter
Published: January 2008

Abstract— During the period 1981–1993, measurements of solar UV irradiances were made at the High‐Alpine Research Station Jungfraujoch (Switzerland, 3576 m a.s.l.) to determine the radiation amplification factor (RAF) for the Robertson‐Berger sunburn meter and for the narrow‐band wavelength ranges of the Eppley filter spectrometer. The Robertson‐Berger sunburn meter model 500 showed a RAF of 1.07 ± 0.15 at solar elevations between 20° and 60°. The RAF for human erythema is 1.1 in comparison. Therefore the Robertson‐Berger sunburn meter is suitable to measure the influence of total atmospheric ozone variations on the effective erythemal irradiance. In the narrow‐band wavelength ranges of the Eppley filter spectrometer the RAF increases greatly at shorter wavelengths with RAF of 1.06, 1.40 and 2.35 for the optical centers 315.1 nm, 311.1 nm and 305.2 nm, evaluated at 30° solar elevation. In order to minimize perturbations by aerosol optical depth and albedo in the evaluation of the RAF the ratios of UV irradiances to total irradiances were evaluated.
MOLECULAR MECHANISM OF DRUG PHOTOSENSITIZATION 7. PHOTOCLEAVAGE OF DNA SENSITIZED BY SUPROFEN
Authors: Condorelli G. , Costanzo L. L. , Guidi G. De , Giuffrida S. , Sortino S.
Published: January 2008

Abstract— Ultraviolet‐A irradiation of a suprofen (2‐[4‐(2‐thenoyl)phenyl]propionic acid) (SPF) buffered solution (pH 7.4) in the presence of supercoiled pBR322 DNA leads to single strand breaks with the formation of an open circular form and subsequent linearization of the plasmid. On the basis of agarose gel electrophoresis data of samples irradiated in an air‐saturated solution or in an oxygen‐modified atmosphere, and the effects of sodium azide, D2O, mannitol, copper(II), superoxide dismutase, 2‐H‐propanol, deferoxamine and surfactants, we suggest a photosensitization mechanism involving singlet oxygen and free radicals. The higher rate of photocleavage in nitrogen compared to that in an air‐saturated solution and the results obtained from oxygen consumption measurements support the hypothesis that both the type I and type II photosensitization mechanisms are operative and that oxygen quenches the excited state of the irradiated drug. The photosensitization model applied was in agreement with that previously applied to cell membrane SPF photoinduced damage. Interaction of the drug with DNA, studied through circular dichroism and fluorescence anisotropy, probably occurs through a surface binding mode. The experimental techniques used for assessing the photodamaging activity of this drug may be useful for screening of phototoxic compounds in the environment and for determining the active species involved.
A SIMPLE AND IMPROVED METHOD OF ISOLATION AND PURIFICATION FOR NATIVE OAT PHYTOCHROME
Authors: Lapko Veniamin N. , Song Pill‐Soon
Published: January 2008

Abstract— A simple procedure for the isolation and purification of 124 kDa phytochrome (phyA) from etiolated Avena seedlings has been developed employing ammonium sulfate back‐extraction. After solubilization of the ammonium sulfate precipitate (250 g/L) an additional ammonium sulfate fractionation with 17 g per 100 mL rather than column chromatography was performed. After several steps of the “washing‐out” procedure with 100 mM phosphate buffer, phytochrome was solubilized in 10 mM phosphate buffer. The resulting phytochrome had a specific absorbance ratio (SAR = A666/A28o) ranging from 0.60 to 0.85. These values are equivalent to those of phytochrome preparations after hydroxyla‐patite chromatography‐ammonium sulfate back‐extraction. The total isolation‐purification time was 8 h and yield of the chromoprotein was 50% higher than the yield using conventional techniques. The phytochrome preparation, after application to a Toyopearl HW‐65S gel filtration column, produced very pure 124 kDa phyA with a specific absorbance ratio greater than 1.00. The spectral characteristics are identical to those described for the best of the highly purified native chromoprotein preparations.