bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOTOPHYSICAL STUDIES OF INDOLE ALKANOIC ACIDS and TRYPTAMINE IN REVERSE MICELLES OF SODIUM DIOCTYL SULFOSUCCINATE
Authors: ENCINAS M. V. , Lissi E. A. , Bertolotti S. G. , Cosa J. J. , Previtali C. M.
Published: January 2008

Abstract— The fluorescence spectra and emission lifetimes of several 3‐alkanoic indoles of different chain length and tryptamine (TA) were studied in sodium dioctyl sulfosuccinate (AOT)/heptane reverse micelles over a wide range of water/AOT ratio (R ‐ 5 to 44). Fluorescence quenching experiments were done using carbon tetrachloride and acrylamide as quenchers. Experiments with TA were carried out using water at pH 3 in order to assure its protonation. Under these conditions, the results indicate that the indole moiety of TA remains at the micellar interface over all the range considered. Furthermore, the results can be interpreted assuming for the TA population a single microenvironment whose properties remain almost invariant when R increases from 11 to 44. The studies employing the 3‐alkanoic indoles were carried out at pH 10. Under these conditions, the anions are progressively displaced to the water pool when the R value increases. This displacement is determined by the length of the side alkyl chain of the 3‐indole derivatives. For these compounds, the quenching experiments indicate that, even at low R values, the excited indole moieties are distributed among different microenvironments.
METALLOPURPURINS and LIGHT: EFFECT ON TRANSPLANTABLE RAT BLADDER TUMORS and MURINE SKIN
Authors: Morgan A. R. , Garbo G. M. , Keck R. W. , Eriksen L. D. , Selman S. H.
Published: January 2008

Purpurins are modified chlorins with photodynamic properties. Their strong absorption in the red region of the visible spectrum makes them candidates for use in photodynamic cancer therapy. A series of metal derivatives of the free base purpurins have been synthesized and shown to cause tumor necrosis in transplantable tumors when exposed to visible light. In the following set of experiments, the effects of two metallo‐derivatives (tin and zinc) of two purpurins, octaethylpurpurin (NT2) and etiopurpurin (ET2), and light on the N‐{4‐(5‐nitro‐2‐furyl)‐2‐thiazolyl}formamide transplantable tumors in Fischer CDF(F344)/CrlBr rats were studied. The photodynamic activity was assessed by a short term assay using tumor dry weight 12 days after purpurin‐PDT as a criterion of response. From these experiments it appears that SnET2>SnNT2>ZnET2>ZnNT2 in photodynamic activity. SnET2 was further characterized by attempting to determine the time interval after systemic injection at which maximum therapeutic effect occurred. These studies shown that 24 h after metallopurpurin injection was the optimum time for treatment of tumors with visible light. In a final set of experiments, the effect of solar light on the skin of hairless mice injected with SnET2 was found to be much less injurious than with hematoporphyrin derivative.
HEMOPROTEIN(S) MEDIATE BLUE LIGHT DAMAGE IN THE RETINAL PIGMENT EPITHELIUM*
Authors: Pautler E. L. , Morita M. , Beezley D.
Published: January 2008

In order to elucidate the mechanisms of blue light damage on ocular tissues, the transepithelial transport, electrical characteristics and ultrastructural properties of irradiated isolated bovine retinal pigment epithelium (RPE) were investigated. Blue light (430 nm) irradiation at 20 mW/cm2 significantly reduced the transepithelial potential and short circuit current of RPE. During blue light exposure, a decrease in chloride transport was observed, and this decrease appeared to be closely coupled to changes in the electrical properties of the pigment epithelium. A decrease in leucine transport was also noted, but the effect required10–30 min of exposure to be manifested on some occasions. Utilizing the observed depolarizing effect of blue light, an action spectrum was determined which encompasses the absorption spectrum of the oxidized and reduced forms of cytochrome c oxidase. O2 uptake studies on isolated pigment epithelial cells verified the reduction of respiration by exposure to blue light, which is observed in other cells. Ultrastructural studies revealed that the major cytopathology observed up to 60 min after blue light exposure was a blistering of the mitochondria which progressed to a swollen, disrupted state within the post irradiation period of 1 h. Comparison of these results with those of other studies suggests that the mechanism of UV‐A damage differs substantially from that of blue light.
In vivo TUMOR OXYGEN TENSION MEASUREMENTS FOR THE EVALUATION OF THE EFFICIENCY OF PHOTODYNAMIC THERAPY
Authors: Tromberg B. J. , Orenstein A. , Kimel S. , Barker S. J. , Hyatt J. , Nelson J. S. , Berns M. W.
Published: January 2008

Abstract—

Among the sequence of events which occur during photodynamic therapy (PDT) are depletion of oxygen and disruption of tumor blood flow. In order to more clearly understand these phenomena we have utilized transcutaneous oxygen electrodes to monitor tissue oxygen disappearance. These results provide, for the first time, non‐invasive real‐time information regarding the influence of light dose on tissue oxygenation during irradiation. Measurements were conducted on transplanted VX‐2 skin carcinomas grown in the ears of New Zealand white rabbits. Rabbits were treated with Photofrin II and tumors were irradiated with up to 200 kj/m2(500 W/m2) of 630‐nm light. Substantial reductions in tumor oxygen tension were observed upon administration of as little as 20 kJ/m2. For a series of brief irradiations, oxygen tension was modulated by the appearance of laser light. Tissue oxygen reversibility appeared to be dependent upon PDT dose. Long‐term, irreversible tissue hypoxia was recorded in tumors for large (200 kJ/m2) fluences. These results suggest that transcutaneous oxygen tension may be useful as a general indicator of the effectiveness of PDT and as anin situpredictor of the energy required to elicit tumor damage.
EVIDENCE FOR THE FORMATION OF A CHLOROPHYLL a/ZEAXANTHIN COMPLEX IN LECITHIN LIPOSOMES FROM FLUORESCENCE DECAY KINETICS
Authors: Searle Geoffrey , Brody Seymour S. , Hoek Arie Van
Published: January 2008

Abstract—

The interaction of Chiawith zeaxanthin (Zea), which is an analogue of lutein, has been studied in soya bean lecithin liposomes using the fluorescence of Chi as monitor. The fluorescence emission spectrum at 4.2 K of Chiashowed characteristic changes in the presence of Zea: the emission maximum shifted from 688 nm to 680 nm, and a peak at 731 nm appeared. The fluorescence decay kinetics of Chiaalone could be described by the sum of two exponential components (T1,≅0.8 ns, T2≅2.5 ns). In the presence of Zea a component with a long lifetime, T≅5 ns, appeared with a large relative amplitude (40%). This indicated the formation of a Chla/Zea complex, in which Chla/Chlainteraction is negligible, presumably because of strong interaction between Chlaand Zea. The fluorescence anisotropy decay kinetics supported the hypothesis of the formation of a large Chlacontaining complex in the presence of Zea. A rotational correlation time, φ≅14 ns at 4°C and φ≅21 ns at 30°C, was found, which is distinctly larger than for samples containing Chlaonly. We interpret these results as further evidence for a strong interaction between Chlaand Zea in the hydrophobic environment of the lecithin liposomes. This interaction may also occur in the Chl‐proteins of the Chialblight‐harvesting complex of plant photosynthesis.
AGGREGATION CHARACTERISTICS OF LASER DYE RHODAMINE 6G IN AQUEOUS SURFACTANT SOLUTIONS
Authors: Kelkar V. K. , Valaulikar B. S. , Kunjappu Joy T. , Manohar C.
Published: January 2008

Abstract— –The role of surfactants as deaggregating agents for the laser dyes is investigated by spectrophotometry using Rhodamine 6G as a representative. A method to estimate the fraction of dye present as monomer, dimer and as a monomer‐surfactant (monomer or micelle) complex is described. It is shown that among the surfactants, cetyl trimethyl ammonium bromide, Triton X‐100, sodium lauryl sulfate (SLS) and potassium oleate, the anionic ones are the most effective in suppressing the aggregation of Rhodamine 6G. While the non‐ionic surfactant is found to be effective only above its critical micellar concentration, the cationic surfactant has no effect on aggregation. The optimum concentration of SLS needed for suppression of dye‐dimers is estimated.
ENCAPSULATED RADIOPHOSPHORESCENT STANDARDS FOR DAY‐TO‐DAY PHOTOMETER CALIBRATION
Authors: O'Kane Dennis J. , Lee John
Published: January 2008

Abstract— Solid, unquenched, radiophosphorescent standards for use in the day‐to‐day calibration of bottom viewing photometers (luminometers) were prepared by encapsulating commercially‐available phosphor powders that are excited to phosphoresce by the β‐ decay of 63Ni (t0,5= 96 yr) or 14C (t0 5= 5730 yr). The radionuclides are physically adsorbed on the phosphors by precipitation either as a “basic nickel carbonate” or as barium carbonate. The radioactive phosphors are then deposited by centrifugation as a thin layer at the bottom of the vials or tubes that are normally used in the photometer. The phosphor layer is infiltrated with a plastic resin and embedded. A light absorbing layer is subsequently cast over the phosphor layer to prevent stray light excitation of phosphorescence. The encapsulated photometer standards have remained mechanically and photometrically stable since their fabrication, which in some cases is 3 years ago. An equivalent level of visible luminescence emitted from the standards of up to 2.3 times 1010 photons.s‐1 was achieved by using an appropriate amount of radioactivity and the proper phosphor. The phosphor used in the standards could be chosen such that the radiophosphorescence emission spectrum corresponded approximately to the chemiluminescence or bioluminescence spectrum under investigation.
OZONE DEPLETION AND INCREASE IN ANNUAL CARCINOGENIC ULTRAVIOLET DOSE
Authors: Kelfkens Gert , de Gruijl Frank R. , van der Leun Jan C.
Published: January 2008

Abstract— –An increase in skin cancer incidence due to an increase of solar ultraviolet (UV) radiation is one of the best quantitated effects of stratospheric ozone depletion. Until now, estimates of effective UV dosages could not be based on spectral data on carcinogenicity. Instead the spectral dependence of sunburn or mutations was used. These data contained little information on longwave ultraviolet radiation (UVA: 315–380 nm). Recently, in hairless mice, experimental data have become available on the carcinogenic effectiveness of the ultraviolet, including UVA. From these new data we can estimate the effect of ozone depletion on the ambient annual carcinogenic UV dose. We find that a 1% decrease in ozone yields a 1.56% increase in annual carcinogenic UV; this value is not strongly dependent on geographical latitude. From this result, combined with the dose‐response relationship for UV carcinogenesis, we conclude that for a 1% decrease in total column atmospheric ozone an increase of 2.7% in non‐melanoma skin cancer is to be expected.
PHOTOPHYSICAL STUDIES ON THE BINDING OF TETRASULFONATOPHENYLPORPHYRIN TO LENS PROTEINS
Authors: Roberts Joan E. , Atherton Stephen J. , Dillon James
Published: January 2008

Abstract— Previous studies have shown that mesotetra(p‐sulfonatophenyl)porphine (TPPS) binds to lens proteins. This characteristic should increase the residence time of the sensitizer in the lens and therefore enhance the probability of inducing photooxidative damage to that tisue in vivo. Subsequent in vivo studies have verified that contention. The present studies were performed to determine the effect of such binding on the spectroscopy and photophysics of the porphyrins.

It was found that the binding of TPPS (1) quenches the fluorescence of lens proteins, (2) causes a shift in the ground state absorption spectra, fluorescence excitation spectra and the triplet excited state spectrum of TPPS to longer wavelengths and (3) results in an increase in the triplet state lifetime of TPPS. In the presence of the isolated crystallins the average triplet lifetime increases in the following order: gamma < beta < alpha.
ISOLATION AND CHARACTERIZATION OF A STRUCTURAL SUBUNIT FROM THE CORE LIGHT‐HARVESTING COMPLEX OF Rhodobacter sphaeroides 2.4.1 AND puc705‐BA
Authors: Chang Mary C. , Meyer Leslye , Loach Paul A.
Published: January 2008

Abstract— –A method for isolating a structural subunit, B825, from the B875 core light‐harvesting complex (LHC) of Rhodobacter sphaeroides 2.4.1 (wild‐type) and a B800‐B850(‐) mutant, puc705‐BA, is presented. This method, based on one developed to prepare a similar subunit, B820, from the core LHC of Rhodospirillum rubrum [Miller et al., Biochemistry 26, 5055–5062 (1987)], requires the dissociation of treated chromatophores with the detergent, octyl‐glucoside. A subsequent gel nitration step separates B800‐850 (if present), reaction centers, and free bacteriochlorophyll from the subunit complex. B825 was quantitatively reassociated into an 873 nm absorbing form which resembled the in vivo complex as judged by its absorption properties. The polypeptides in B825 and B800‐850 were isolated by HPLC and identified by N‐terminal amino acid sequencing. Two polypeptides, a and p, were found in each complex in a 1: 1 ratio. The spectral and biochemical properties of the subunits isolated from Rhodospirillum rubrum, Rhodobacter sphaeroides, and Rhodobacter capsulatus are compared.
TECHNICAL NOTE
Authors: Boens Noël , Tamai Naoto , Yamazaki Iwao , Yamazaki Tomoko
Published: January 2008

Abstract— –The use of a proximity type 12 µm microchannel plate photomultiplier (Hamamatsu R1564U) is demonstrated for the accurate determination of picosecond lifetimes of xanthione, stiff stilbene, cryptocyanine, pinacyanol chloride, erythrosin and l, l′‐diethyl‐2,2′‐dicarbocyanine iodide in solution at room temperature. Single curve and global analyses with reference convolution give statistically acceptable mono‐exponential fits to all obtained decays. The count rate and wavelength dependence of the measured excitation pulse profile are discussed. Matching the count rates of sample and reference is recommended for reliable picosecond lifetime determinations.
STUDY OF XANTHONE‐CYCLODEXTRIN INCLUSION COMPLEXES IN THE SOLID STATE USING TIME‐RESOLVED DIFFUSE REFLECTANCE‐LASER FLASH PHOTOLYSIS*
Authors: Barra Monica , Bohne Cornelia , Scaiano J. C.
Published: January 2008

The photochemistry of xanthone complexed with cyclodextrins (α‐, β‐ and γ‐CD) in the solid state has been examined by diffuse reflectance laser flash photolysis. The first half‐life for xanthone triplet decreases as the size of the CD cavity increases; long‐lived ketyl radicals are observed in the cases of β‐ and γ‐CD. These changes in photobehavior are attributed to the restrictions on the mobility of included xanthone imposed by the CD structure.
PHOTOPHYSICAL PROPERTIES AND CONFORMATIONAL EQUILIBRIUM OF trans‐6‐STYRYLQUINOXALINE
Authors: Kim Maeng Sup , Shim Sang Chul
Published: January 2008

The wavelength dependent fluorescence spectra and bi‐exponential fluorescence decays of trans‐6‐styrylquinoxaline (6‐StQx) indicate that two conformers exist in equilibrium in solution. When comparing the conformationally restricted analogues (5Me‐6‐StQx and 7Me‐6‐StQx) with 6‐StQx, the short‐wavelength absorbing conformer of 6‐StQx can be assigned to conformer(A) and the long‐wavelength absorbing component to conformer(B). The temperature effects on the fluorescence lifetime indicate that the short‐lived conformer(A) is the more stable conformer in non‐polar solvents, while the long‐lived conformer(B) is the stable component in polar solvents. The results of semiempir‐ical AMI and CNDO/S CI calculations on both the ground and excited states are consistent with the conclusions drawn from the spectral data.
ORGANIZATION OF PIGMENT‐PROTEIN COMPLEXES INTO MACRODOMAINS IN THE THYLAKOID MEMBRANES OF WILD‐TYPE and CHLOROPHYLL fo‐LESS MUTANT OF BARLEY AS REVEALED BY CIRCULAR DICHROISM
Authors: Garab G. , Kieleczawa J. , Sutherland J. C. , Bustamante C. , Hind G.
Published: January 2008

The organization of pigment‐protein complexes into large chiral macrodomains was investigated in wild‐type and chlorophyllb‐less mutant thylakoid membranes of barley. The variations in the anomalous circular dichroism bands and in the angular‐dependence of circular intensity differential scattering showed that in wild‐type chloroplasts, the formation of macrodomains was governed by interactions of the light‐harvesting chlorophyllalbcomplexes (LHCII). Two external factors could be identified which regulate the parameters of the anomalous circular dichroism signal: (i) electrostatic screening by divalent cations under conditions that favor membrane stacking and (ii) the osmotic pressure of the medium, which is suggested to affect the lateral interactions between complexes and influence the packing‐density of particles. These two factors governed preferentially the negative and the positive anomalous circular dichroism signals, respectively. In thechlorina f‐2mutant thylakoid membranes, deficient in most chlorophyllbbinding proteins, the formation of macrodomains which gave rise to the anomalous circular dichroism signals was still regulated by these same external factors. However, in the absence of major LHCII polypeptides the formation of macrodomains was apparently mediated by other complexes having weaker interaction capabilities. As a consequence, the size of the macrodomains under comparable conditions appeared smaller in the mutant than in the wild‐type thylakoid membranes.

Circular dichroism is a valuable probe for examining the long‐range interactions between pigment‐protein complexes which participate in the formation and stabilization of membrane ultrastruc‐ture. A functional role of macrodomains in long‐range energy migration processes is proposed.
RESISTANCE TO PHOTODYNAMIC THERAPY IN RADIATION INDUCED FIBROSARCOMA‐1 and CHINESE HAMSTER OVARY‐MULTI‐DRUG RESISTANT CELLS in vitro
Authors: Singh Gurmit , Wilson Brian C. , Sharkey Sheila M. , Browman George P. , Deschamps Paula
Published: January 2008

A degree of resistance to photodynamic therapy (PDT) has been induced in radiation‐induced fibrosarcoma‐1 (RIF‐1) tumor cells by repeated photodynamic treatment with Photofrin (4 or 18 h incubation) in vitro to the 0.1‐1% survival level, followed by regrowth from single surviving colonies. The resistance is shown as increased cell survival in the strain designated RIF‐8A, compared to the wild‐type RIF‐1 cells, when exposed to increasing Photofrin concentration for 18 h incubation and fixed light exposure. No difference was found between RIF‐1 and RIF‐8A in the uptake of Photofrin per unit cell volume at 18 h incubation.

Resistance to PDT was also observed in Chinese hamster ovary‐multi‐drug resistant (CHO‐MDR) cells compared to the wild‐type CHO cells, possibly associated with decreased cellular concentration of Photofrin in the former. By contrast, the PDT‐resistant RIF‐8A cells did not show any cross‐resistance to Adriamycin, nor was there any significant drug concentration difference between RIF‐1 and RIF‐8A. These findings suggest that different mechanisms are responsible for PDT‐induced resistance and multi‐drug resistance.
ROOM TEMPERATURE TIME‐RESOLVED IN μs RANGE DELAYED LUMINESCENCE OF CHLOROPHYLL a AND CHLOROPHYLL‐LUTEIN MIXTURE SOLUTIONS
Authors: Planner Alfons , Frackowiak Danuta
Published: January 2008

References

Using time‐resolved in μS range luminescence spectroscopy, we observed at 20°C the emission of chlorophylla,pheophytinaand chlorophyll a‐lutein mixture solutions. This delayed emission exhibits several maxima in the650–750 nm region. The positions and kinetics of decay of delayed emission bands depend on chlorophyll concentration, and vary as a result of pheophytinization and addition of lutein. Our results can be explained by supposition that upon excitation, charge transfer species are formed in various pigment complexes. The back electron transfer reactions yield chlorophyll excited singlet states contributing to observed delayed emission. Delay in emission seems to be due also to the trapping of excitation on the triplet states of various forms of pigment and its detrapping with the participation of thermal energy followed by energy transfer to the forms of pigment characterized by different decay times.
ENERGY DISSIPATION AND PHOTOPROTECTION MECHANISMS DURING CHLOROPHYLL PHOTOBLEACHING IN THYLAKOID MEMBRANES
Authors: Miller Nathalie , Carpentier Robert
Published: January 2008

The kinetics of chlorophyll photobleaching were followed in whole thylakoid membranes as well as in photosystem I and photosystem II submembrane fractions. The onset of photobleaching was characterized by a slow rate which indicated the presence of energy traps implicated in the photoprotection of the bulk pigments. The pigments in photosystem I submembrane fractions bleached at a faster rate than those in photosystem II counterparts, the latter being more sensitive towards photoinhibition. An analysis of the pigment‐protein complexes isolated from whole thylakoid membranes during the course of a photobleaching experiment has shown that the core‐antenna complexes, including CP29, are more sensitive to illumination than the peripheral complexes. The absorption spectra of the CPI and CP29 complexes presented a blue shift of the red absorption maximum after partial photobleaching, indicative of a non‐homogeneous bleaching of the holochromes in these complexes. An analysis of these data points towards the involvement of CP29 in a photoprotection mechanism at the level of photosystem II. The weaker resistance of photosystem I to photobleaching relative to photosystem II and its stronger resistance to photoinhibition is discussed in terms of an energy dissipation pathway in thylakoid membranes.
A NEW REDUCING AGENT OF FLAVINS AND ITS APPLICATION TO THE ASSAY OF BACTERIAL LUCIFERASE
Authors: Lei Ben‐Fang , Becvar James E.
Published: January 2008

References

Copper(I) plus ethylenediaminetetraacetic acid, Cu(I)‐EDTA, reduces flavins. Using Cu(I)‐EDTA reduction of riboflavin 5′‐phosphate, a new assay method for bacterial luciferase is established. In previous assay methods, flavin and aldehyde substrates for luciferase have been routinely added to luciferase at different times; the new assay permits aldehyde and Cu(I)‐reduced flavin to be injected simultaneously into air‐saturated buffer containing luciferase. In the new assay method using Cu(I), bovine serum albumin is not required, the initial emission intensity is more than twice and the overall yield is about twice of that in the so‐called standard assay for luciferase.
PHOTOCHEMICAL REACTIVITY OF MOLECULES TRAPPED IN SOL‐GEL GLASSES*
Authors: Slama‐Schwok Anny , Avnir David , Ottolenghi Michael
Published: January 2008

Photosensitizers trapped in porous sol‐gel glasses are shown to undergo photoinduced electron transfer with molecules present in the intra‐pore liquid phase. The phenomenon appears to be general, independent of molecular charge and size. The predominant mechanism involves long range electron transfer from, or to, an adsorbed solute molecule and a photosensitizer embedded in the glass. Such long range interactions are also the primary factor leading to a residual photogenerated radical ion pair which is extremely long lived (4–5orders of magnitude longer with respect to the same process in homogeneous solutions). The results bear on artificial photosynthetic devices in which solar energy conversion and storage depends on inhibition of the energy‐wasting back electron transfer reaction.
THE REACTIVITY OF CITRONELLOL and α‐THUJENE WITH SINGLET OXYGEN. RATE CONSTANTS OF CHEMICAL REACTION and PHYSICAL QUENCHING*
Authors: Bouamri M. El , Gorrichon J. P. , Braun A. M. , Oliveros E.
Published: January 2008

The quantum yields of Rose Bengal sensitized photooxidation of citronellol and α‐thujene have been determined as a function of added acceptor and compared with those of furfuryl alcohol as a standard. The results permitted the calculation of the corresponding rate constants of chemical reaction(kT)and physical quenching (Kq) of singlet oxygen. The sum(kT+ kq)has been verified independently by a Stern‐Volmer analysis of the singlet oxygen luminescence quenching. α‐Thujene reacts faster with singlet oxygen than citronellol, physical quenching being negligible in both cases.
BUTYL CONFORMATIONAL REORGANIZATION AS A POSSIBLE EXPLANATION FOR THE LONGITUDINAL FLEXIBILITY OF THE BINDING SITE OF BACTERIORHODOPSIN. THE AZULENE and C‐22 RETINOID ANALOGS*
Authors: Liut Robert S. H. , Liu Corey W. , Li Xiao‐Yuan , Asato Alfred E.
Published: January 2008

The UV‐VIS absorption data of four bacteriorhodopsin (BR) analogs formed from azulene‐retinals of varying polyene chain length show that the one‐bond‐shortened to one‐bond‐lengthened analogs possess comparable opsin shift values to that of BR. A two‐bond‐shortened analog exhibited a much smaller opsin shift. These data, combined with those reported for the C‐22 retinal analog (Tokunaga et al., 1977, Biophys. J. 19,191–198) were analyzed by molecular modelling and computer graphics in terms of a model where conformational flexibility of the appended butyl is the controlling factor in determining ease of pigment formation and protein/substrate interaction.
LONG‐TERM VARIATIONS IN ULTRAVIOLET SUNLIGHT REACHING THE BIOSPHERE: . CALCULATIONS FOR THE PAST THREE DECADES
Authors: Frederick J. E. , Weatherhead E. C. , Haywood E. K.
Published: January 2008

The long‐term data base on atmospheric ozone combined with a set of radiative transfer calculations provides estimates of the variability in ultraviolet (UV) sunlight that should have occurred over the period1957–1988 under clear, pollution‐free skies. Results refer to the earth's surface at specific locations in the Northern Hemisphere and to averages over collections of sites located in three latitude bands from 30 to 64°N. For any one year the annually integrated solar irradiance, weighted by the action spectrum for erythema, typically lies within3–4% of the 32‐year mean. No statistically significant trends span the entire 32‐year time frame. However, over the shorter time period1970–1988 the annually integrated erythemal irradiance shows an upward trend of +2.1 ± 1.2% per decade based on all ozone data at latitudes from 40 to 52°N. No trends exist in lower (30‐39°N) and higher (53‐64°N) latitude bands. We caution that a trend line provides a very simple index of the variability in UV sunlight, and these results should not necessarily be extrapolated into the future.
CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER REACTIONS IN LIPID VESICLES:ENHANCEMENT IN YIELD OF VECTORIAL ELECTRON TRANSFER ACROSS THE BILAYER FROM REDUCED CYTOCHROME c TO OXIDIZED FERREDOXIN BY ADDITION OF VALINOMYCIN PLUS POTASSIUM ION
Authors: Zhao Zhan‐Gong , Tollin Gordon
Published: January 2008

Chlorophyll photosensitized electron transfer across a vesicle bilayer from reduced cytochromecin the inner compartment to oxidized ferredoxin in the outer compartment, using propylene diquat as a mediator, has been investigated using both steady‐state and laser flash photolysis methods. One of the factors limiting the quantum yield is the transmembrane potential, which is formed during sample preparation and is increased by the electron transfer process across the membrane bilayer. This limitation can be diminished by the incorporation of valinomycin into the bilayer in the presence of potassium ion. The overall quantum yield can be approximately doubled (up to a total of 22% based on the chlorophyll triplet which is quenched, and 2.8% based on the absorbed quanta) by valinomycin addition. Another quantum yield limitation arises from the accumulation of oxidized cytochrome c in the inner aqueous compartment, which is formed as a consequence of the transbilayer electron transport process and can quench triplet chlorophyll on the inner side of the vesicle. The chlorophyll cation radical generated in this way can participate in the electron exchange equilibrium between chlorophyll molecules located within the bilayer, and thus inhibit electron flow from inside to outside. This acts to limit the extent of cytochromecoxidation to ≤ 50% of the original amount.
DETECTION OF PORPHYRIN EXCITED STATES IN THE INTACT BOVINE LENS
Authors: Roberts Joan E. , Atherton Stephen J. , Dillon James
Published: January 2008

Previous steady state and time resolved spectroscopic studies on porphyrins have shown that the triplet lifetimes of those sensitizers that bind to lens proteins are lengthened by several orders of magnitude. Presented here is an extension of this experiment to measure these transients in an intact bovine lens. As demonstrated by steady state fluorescence spectroscopy and flash photolysis, mesotetra (p‐sulfonatophenyl)porphyrin (TPPS) binds to lens proteins. In air‐saturated aqueous solution, TPPS has a triplet lifetime of 2 μs. In an intact bovine lens the triplet state decayed via biexponential kinetics with lifetimes of 0.16 and 1.6 μs. In addition to a lengthening of the lifetime there was a red shift in the triplet transient spectra of10–20 nm of the porphyrin in the intact lenses.
TIME‐RESOLVED ULTRAVIOLET ABSORPTION CHANGES IN THE PHOTOCYCLE OF BACTERIORHODOPSIN*
Authors: Sharonov A. Yu. , Tkachenko N. V. , Savransky V. V. , Dioumaev A. K.
Published: January 2008

Abstract–The kinetics of the absorption changes associated with the perturbation of aromatic acids during the photocycle of bacteriorhodopsin (bR) were studied at room temperature with microsecond time‐resolution. Flash experiments with nanosecond excitation at 532 nm were performed on the purple membrane suspension at a number of measuring wavelengths in the spectral range250–630 nm (to monitor both non‐chromophore changes and the photocycle kinetics). The kinetic data collected at different wavelengths were simultaneously fitted with a sum of exponentials to obtain time‐resolved UV‐VIS difference spectra of photocycle intermediates. This approach allowed us to separate kinetically distinct contributions coupled with tryptophan(s) and tyrosine(s) perturbations. Contributions associated with a reversible perturbation of tryptophans appeared with complex (multistep) kinetics during the bRM transitions and relaxed in a single step during the M0 transition. A contribution associated with perturbation of the local environment of tyrosine appeared before the L and relaxed during the Ob̊ transition.
FUNCTIONAL PROPERTIES OF INTERPHOTORECEPTOR RETINOID‐BINDING PROTEIN*
Authors: Pepperberg David R. , Okajima Ting‐Ing L. , Ripps Harris , Chader Gerald J. , Wiggert Barbara
Published: January 2008

Abstract– It has been hypothesized that interphotoreceptor retinoid‐binding protein (IRBP) functions as a two‐way carrier of retinoid between the retinal pigment epithelium (RPE) and rod photoreceptors in the vertebrate eye. This hypothesis has been tested in recent studies that have employed purified, initially ligand‐free, bovine IRBP and the “RPE‐eyecup” obtained from the toad (Bufo marinus) eye. The present experiments further characterize the IRBP/RPE‐eyecup system with respect to (i) the solubilization and protection of retinol by IRBP, and (ii) the time course of IRBP‐mediated release of 11‐cis retinal by the RPE. The data, together with previous findings in the IRBP/RPE‐eyecup preparation, support the view that 11‐cis retinal is the principal retinoid released by the RPE into IRBP‐supplemented aqueous medium, and that IRBP in vivo promotes the regeneration of rhodopsin by facilitating the exchange of retinoid between bleached rods and the RPE.
ENHANCED EXPRESSION OF PROTEIN KINASE C GENE CAUSED BY SOLAR RADIATION
Authors: PEAK JENNIFER G. , WOLOSCHAK GAYLE E. , PEAK MEYRICK J.
Published: January 2008

Abstract—

Natural solar radiation (5 min of midday exposure in mid July, latitude 42°N) induces protein kinase C mRNA almost two‐fold in human epithelioid P3 cells in culture. This response is the same as that following tumor promotion by chemicals. The result indicates a possible role of promotion by solar UV radiation.
PHOTOCONTROL OF HYPOCOTYL ELONGATION IN LIGHT‐GROWNCucumis sativusL. PHOTOSYNTHETIC REQUIREMENT FOR A FLUENCE RATE DEPENDENT PHYTOCHROME RESPONSE
Authors: GABA VICTOR , BLACK MICHAEL , CANAANI ORA , ATTRIDGE TERENCE H.
Published: January 2008

Abstract—

We investigated the role of photosynthesis in the photocontrol of extension growth of the hypocotyl of light‐grownCucumis sativusL. Previous work [Gaba and Black (1985b)Plant Physiol.79, 1011] demonstrated that the inhibition of cucumber hypocotyl elongation is a fluence rate dependent response in red light. However, the relative contributions of phytochrome and photosynthesis to the photon flux dependent inhibition response were not clear. Here we have shown that photoperception by the foliar cotyledons as well as the hypocotyl itself are responsible for fluence rate dependence in red light. The inhibitor of photosynthesis diuron [3‐(3,4‐dichlorophenyl)‐1, 1‐dimethylurea] reduced both the magnitude of inhibition and the fluence rate dependency in red light, indicating an involvement of photosynthesis. Furthermore, the growth of non‐pigmented seedlings (treated with the herbicide norflurazon) was less inhibited by red light, with no fluence rate dependency. In particular, inhibition due to cotyledon photoperception was completely lost in non‐pigmented (norflurazon‐treated) plants, and much reduced by diuron treatment. Hypocotyl‐perceived red light inhibition was only slightly reduced by treatment with norflurazon and diuron. Photosynthesis was compared directly to photo‐inhibition of growth: the photon flux response curve of oxygen evolution of greenCucumiscotyledons was distinctly different from that of hypocotyl inhibition. In conclusion, photosynthesis is an essential requirement for the cotyledon‐perceived inhibition, but the response itself is not due to photosynthesis.
TANNING SALON EXPOSURE SUPPRESSION OF DNA REPAIR CAPACITY AND MITOGEN‐INDUCED DNA SYNTHESIS
Authors: LARCOM L. L. , MORRIS T. E. , SMITH M. E.
Published: January 2008

Abstract—

Mitogen responsiveness and the capacity to repair genetic damage were measured in lymphocytes collected from young, healthy, adult Caucasians immediately before exposure in commercial tanning salons and again 24 h after exposure. For every individual studied, tanning exposure produced significant inhibition of phytohemagglutinin‐induced mitogenesis or of the ability to repair DNA lesions by unscheduled DNA synthesis. The results imply that such exposure could: (1) pose a significant hazard for individuals who are already immunosuppressed (e. g. cancer patients, AIDS patients or carriers of latent HIV) and (2) increase the carcinogenic effects of environmental mutagens.
INHIBITORY EFFECT OF 8‐METHOXYPSORALEN PLUS ULTRAVIOLET‐A ON INTERLEUKIN‐1 PRODUCTION BY MURINE KERATINOCYTES
Authors: TOKURA YOSHIKI , YAGI JUNJI , EDELSON RICHARD L. , GASPARRO FRANCIS P.
Published: January 2008

Abstract—

We report the effects of 8‐methoxypsoralen (8‐MOP) plus ultraviolet‐A (UV‐A) irradiation on interleukin‐1 (IL‐1) production by murine epidermal keratinocytes, correlating its effect on IL‐1 with cell viability, DNA synthesis, and 8‐MOP‐DNA photoadduct formation. Freshly isolated murine keratinocytes were treated with various doses of 8‐MOP (5–100 ng/mL; incubation time, 30 min) plus 1 J/cm2 UV‐A and cultured for 1–3 days. The IL‐1/epidermal cell‐derived thymocyte‐activating factor (ETAF) activity in both supernatant and cell extract was reduced proportionately with increasing doses of 8‐MOP/UV‐A. Interleukin‐1 inhibitors induced by 8‐MOP plus UV‐A were not detected in either supernatant or cell extract. A clear reduction of the IL‐1 production was induced by the treatment as low as 15 ng/mL 8‐MOP plus 1 J/cm2 UV‐A, which led to the formation of 0.52 8‐MOP photoadducts per million DNA bases and affected neither cell viability nor DNA synthesis of the treated cells. Cells treated with 100 ng/mL 8‐MOP and 1 J/cm2 UV‐A exhibited 57% suppression of IL‐1 production in both 2‐ and 3‐day culture samples. This treatment resulted in the formation of 3.8 photoadducts per million bases as well as significant abrogation of DNA synthesis although cell viability was unchanged. These observations provide some insights into the phototoxicity mechanisms of 8‐MOP and the effect of PUVA therapy on the cytokine regulation in keratinocytes.
SIMULTANEOUS SATURATION OF VARIABLE FLUORESCENCE YIELD AND PHOTOACOUSTICALLY MONITORED THERMAL EMISSION IN THYLAKOID MEMBRANES
Authors: CARPENTIER ROBERT , OWENS THOMAS G. , LEBLANC ROGER M.
Published: January 2008

Abstract—

Thermal and fluorescence emission from thylakoid membranes were monitored simultaneously in a photoacoustic cell. A close relationship existing between variable fluorescence and variable thermal emissions is demonstrated. The modulated measuring beam of the photoacoustic spectrophotometer was used to study the effect of light intensity on the energy storage yield and on the variable fluorescence yield. The half‐saturation light intensities obtained for both parameters were 8.5 and 9.1 W m−2, respectively. The similar sensitivity of energy storage and variable fluorescence yield to light intensity indicates that electron transfer with plastoquinone as last acceptor is probably responsible for the photoacoustically monitored energy storage.
1H‐INDENYLFURAN AND THIOPHENE DERIVATIVES– A NEW CLASS OF SINGLET OXYGEN SENSITIZERS
Authors: D'AURIA MAURIZIO , VANTAGGI ANNA
Published: January 2008

Abstract— Photophysical and photochemical properties of 1H‐indenylfuran and thiophene derivatives were studied. UV spectra showed that all the compounds tested absorbed UV light in the region 350–380 nm. The fluorescence spectra of 4a‐e showed bands in the region 410–470 nm and quantum yields (φF) in the range 0.25–0.88. Attempts to calculate the triplet energy of 4a‐e failed except for 4c and 4d, which showed ET= 43–44 kcal mol‐1. These compounds are a new class of singlet oxygen sensitizers. The sensitized reaction of 2,5‐dimethylfuran with singlet oxygen was followed showing that 4a and 4e are more reactive than α‐terthiophene (4.0 and 2.5 times respectively), while the other compounds show the same reactivity as 1. This behavior can be explained considering the different intersystem crossing quantum yields of compounds 4a‐e. Diazabicyclo[2. 2. 2]octane is a quencher of singlet oxygen in this reaction, while we can exclude superoxide ion formation using the photooxidation of α, α‐dimethylstilbene.
LIGHT INDUCED RELOCALIZATION OF SULFONATEDmeso‐TETRAPHENYLPORPHINES IN NHIK 3025 CELLS AND EFFECTS OF DOSE FRACTIONATION
Authors: BERG KRISTIAN , MADSLIEN KARI , BOMMER JERRY C. , OFTEBRO REIDAR , WINKELMAN JAMES W. , MOAN JOHAN
Published: January 2008

Abstract—Human cervix carcinoma cells of the line NHIK 3025 were incubated for 18 h with sulfonatedmeso‐tetraphenylporphines (TPPSnwheren= 1, 2a, 2o or 4) followed by 1 h in sensitizer‐free medium and then exposed to light. The fluorescing fraction of TPPS4, TPPS2oand TPPS2ahas recently been shown to be located intracellularly in extracellular granules which are intracellularly localized in a similar pattern as acridine orange‐stained granules, assumed to be endosomes and lysosomes (Berg, K., A. Western, J. Bommer and J. Moan.Photochem. Photobiol.52, 481–487). Light exposure induced a relocalization of TPPS4from its granular pattern to mainly the nuclear area while TPPS2oand TPPS2arelocalized mainly to cytoplasmic areas. After the light‐induced relocalization TPPS4became less efficient in sensitizing photoinactivation of cells as measured per fluorescing cellbound TPPS4molecules while TPPS2aand TPPS2obecame more efficient. These changes were independent of the extracellular concentration of TPPSnapplied to the cells, except for cells incubated with 75 μg/mL TPPS4. These cells became more sensitive to light after a light exposure inactivating 20% of the cells. This increased photosensitivity seems to be related to a 2–2.5 fold increase in the amount of fluorescing cellbound TPPS4induced by the first light exposure.
INCREASED TRANSCRIPTION AND TRANSLATION OF HEME OXYGENASE IN CHINESE HAMSTER FIBROBLASTS FOLLOWING PHOTODYNAMIC STRESS OR PHOTOFRIN II INCUBATION
Authors: GOMER CHARLES J. , LUNA MARIAN , FERRARIO ANGELA , RUCKER NATALIE
Published: January 2008

Abstract— Porphyrin mediated photosensitization can enhance the transcription and translation of several oxidative stress genes. In this study, we report on the enhanced expression of the gene encoding for heme oxygenase in Chinese hamster fibroblasts by; (1) incubation in Photofrin II; (2) Photofrin II mediated photosensitization; and (3) photosensitization induced by Rose Bengal. Increased expression of heme oxygenase mRNA was accompanied by a concomitant increase in the synthesis of the 34 kDa heme oxygenase protein. Western blot analysis using antibody to heme oxygenase confirmed the immunoreactivity of the 34 kDa protein induced by Photofrin II and PDT. These results demonstrate that heme oxygenase can be activated by non‐metalloporphyrins as well as by photosensitization associated with singlet oxygen mediated subcellular injury.
PHOTOMORPHOGENESIS IN Penicillium isariaeforme: EXOGENOUS CALCIUM SUBSTITUTES FOR LIGHT
Authors: MUTHUKUMAR GANAPATHY , JENSEN ELLEN C. , NICKERSON ANN W. , ECKLES MARK K. , NICKERSON KENNETH W.
Published: January 2008

Abstract— Penicillium isariaeforme is a photomorphogenic fungus which produces upright bundles of conidia‐bearing mycelia (called coremia) when grown on a defined medium in visible (450–500 nm) light. We found that exogenous Ca2+ ions could substitute for light. In the dark 1–2 mM Ca2+ triggered coremia formation. Dark induction of coremia was specific for Ca2+ in that it could not be duplicated by 50 mM Ba2+, Fe2+, Mg2+, Mn2+, Sr2+, or Zn2+. Additionally, light‐induced coremia formation was inhibited by both KI (2.5 mM) and phenylacetic acid (0.25 mM).
QUENCHING OF SINGLET OXYGEN BY HUMAN RED CELL GHOSTS
Authors: KANOFSKY JEFFREY R.
Published: January 2008

Abstract— Time resolved measurements of singlet oxygen phosphorescence at 1270 nm were made from unsealed red cell ghosts, labeled with 5‐(N‐hexadecanoyl)aminoeosin and suspended in deuterium oxide buffer. The singlet oxygen emission lifetime was long, 23 ± 1 μs. The lifetime of the singlet oxygen phosphorescence from intact unsealed ghosts was not a measure of the singlet oxygen lifetime within the red cell ghost membrane, however. The prolonged singlet oxygen emission was due to singlet oxygen escaping from the thin membrane into the buffer, since the emission lifetime was significantly shortened by adding azide ion or water to the deuterium oxide buffer.

The lifetime of singlet oxygen within the red cell ghosts membrane was estimated by dispersing the ghosts with detergent and then measuring the singlet oxygen lifetime in deuterium oxide buffers containing various dilutions of the dispersed ghosts. Apparent singlet‐oxygen quenching constants were measured using four different photosensitizing dyes and two different detergents. The apparent quenching constant was independent of the dye used, but varied significantly with different detergents. Extrapolation of this data to “100%” ghost concentration gave a singlet oxygen lifetime from 24 and 130 ns. A ghost concentration of “100%” was defined as that concentration of red cell ghost molecules which would be contained within a red cell ghost membrane pellet containing no buffer solutions. Most of the singlet oxygen quenching was due to proteins. Lipids extracted from red cell ghosts accounted for only 2‐7% of the total singlet oxygen quenching.
A COMPARISON OF FLUORESCENCE METHODS USED IN THE PHARMACOKINETIC STUDIES OF Zn(II)PHTHALOCYANINE IN MICE
Authors: BIOLO R. , JORI G. , KENNEDY J. C. , NADEAU P. , POTTIER R. , REDDI E. , WEAGLE G.
Published: January 2008

Abstract— The pharmacokinetics of Zn phthalocyanine (ZnPc) encapsulated in dipalmitoyl‐phosphatidyl‐choline (DPPC) liposomes, injected intravenously in Skh:HR‐1 nude mice, was monitored by two in vitro techniques and one in vivo technique, all based on fluorescence spectroscopy. The in vitro methods involve either fluorescence measurements on thin tissue sections or on extracts from these tissues. The in vivo method involves the fluorescence measurement at the skin surface. Both in vitro techniques gave similar results which are consistent with previous findings on the pharmacokinetic behavior of ZnPc. The liver and spleen showed rapid ZnPc concentration increases, reaching a maximum level in 30 min. or less post drug administration. Relatively little ZnPc was detected in the skin, fat or muscle, the maximum concentration occurring at 12h. In vivo fluorescence reached a maximum intensity approx. 6 h post injection at the mid‐chest analysis site and at 12 h in the thigh. The in vivo measurements at two different anatomical sites showed pharmacokinetic behavior that reflects an overall integrated fluorescence originating from several tissue sites.
PSORALENS CLEAVE pBR322 DNA UNDER ULTRAVIOLET RADIATION
Authors: Kagan Jacques , Chen Xinsheng , Wang Tian P. , Forlo P.
Published: January 2008

Abstract—

supercoiled (SC) pBR322 was used to probe the recent claim that 5‐geranoxylpsoralen (5‐GOP) did not photoreact with DNA. Contrary to expectations, 5‐GOP was found to damage DNA in the presence of UV‐A through two competing pathways: (a) single strand breaks, identified by the conversion of supercoiled into open circular and linear DNA, and (b) cross‐linking, revealed by the fluence‐dependent decrease in the extent of denaturation of the double stranded supercoiled DNA to single stranded circular DNA. In addition, a fluence‐dependent modification reduced the ability of the restriction enzyme EcoR I to linearize the photosensitized DNA, and alkali‐labile lesions were generated.

Psoralen, 5‐methoxypsoralerl, and 8‐methoxypsoralen, which are well‐known to undergo cycloaddi‐tion to DNA, had a more pronounced effect on supercoiled DNA. Single strand breaks occurred more readily than with 5‐GOP, and the surviving SC form remaining had reduced electrophoretic mobility in agarose gels. In all cases, the DNA damage was more prominent when oxygen was absent.
LASER MEDIATED RELEASE OF DYE FROM LIPOSOMES
Authors: Meulen David L. Vander , Misra Prabhakar , Michael Jason , Spears Kenneth G. , Khoka Mustafa
Published: January 2008

Abstract—

Liposomes made from phospholipids and containing sulforhodamine dye (1–50 mM) have been irradiated with nanosecond and picosecond laser pulses. Individual liposomes were locally heated by laser absorption of dye dimers during a single laser pulse, and heating was sufficient to release the liposome contents. The extent of dye release produced by a single laser pulse was shown to be quantitatively dependent on several interdependent variables, including dye concentration, liposome size, laser excitation parameters and initial temperature of the dye‐liposome system. Fluorescence lifetime data having three components have been obtained and analyzed in terms of three dye environments. Quantitative estimates support a photo‐induced thermal mechanism for liposome lysis and release of its contents. These results may be useful for laser induced delivery of therapeutic agents or other applications of lasers in biological systems.