bluuebunny/crossref_metadata_2025 huggingface dataset:
PHOTOINDUCED ELECTRON TRANSFER
Authors: Fox Marye Anne
Published: January 2008

Abstract— Given the pre‐eminent roles of photoinduced electron transfer and energy transfer as primary events in photobiology, it is incumbent on practitioners of the science to understand those principles which govern these elementary events. Recent developments in both theory and experiment on photoinduced electron transfer have allowed for important insights into understanding the factors governing such steps. For example, shown in Fig. 1 is a representation of the positions of the chromophores in the photosynthetic reaction center of Rhodopseudomonas sphaeroides, as determined from crystallographic measurements (Chang et al., 1986), showing that its three dimensional arrangement within an intact membrane is analogous to that observed earlier in Rhodopseudomonas viridis (Deisenhofer et al., 1984). In both systems, the critical event of photosynthesis is the transfer of an electron from the photoexcited special pair of bacteriochlorophylls located at the top via the pheophytin at the far right to the quinone at the bottom which acts as an ultimate repository for the separated charge. Of great importance is a determination of those factors which govern the efficiency and the rate of electron transfer through this photoinduced cascade and a better understanding of how this fixed, prearranged structure maximizes the efficiency of photochemical energy storage.

Although the reaction center represents nature's most graphic and most detailed connection between the experimental and theoretical models of photoinduced electron transfer, much of the physical insight into this process has been developed on simpler organic molecules. Rattier than focusing on the details of photosynthesis, this article will concentrate on recent developments in model systems which evaluate the relative importance of factors influencing the efficiency and rates of excited state induced electron transfer. We introduce these concepts at a level appropriate for the scientifically literate biologist who has not heretofore been concerned with such details. Since this is an overview article, few citations of the original literature will appear, and the interested reader should refer to any number of excellent topical reviews which consider specific aspects of photoinduced electron transfer for further investigation (Fox and Chanon, 1989; Pac and Oshitani, 1989).
QUINONE SENSITIZED ELECTRON TRANSFER PHOTOOXIDATION OF NUCLEIC ACIDS: CHEMISTRY OF THYMINE AND THYMIDINE RADICAL CATIONS IN AQUEOUS SOLUTION*
Authors: Wagner J. R. , Lier J‐ E. van , JOHNSTON L. J.
Published: January 2008

Abstract—

The 2‐methyl‐l,4‐naphthoquinone (MQ) sensitized photooxidation of nucleic acid derivatives has been studied by laser flash photolysis and steady state methods. Thymine and thymidine, as well as other DNA model compounds, quench triplet MQ by electron transfer to give MQ radical anions and pyrimidine or purine radical cations. Although the pyrimidine radical cations cannot be directly observed by flash photolysis, the addition of N,N,N',N'‐tetramethyl‐l,4‐phenylenediamine (TMPD) results in the formation of the TMPD radical cation via scavenging of the pyrimidine radical cation. The photooxidation products for thymine and thymidine are shown to result from subsequent chemical reactions of the radical cations in oxygenated aqueous solution. The quantum yield for substrate loss at limiting substrate concentrations is 0.38 for thymine and 0.66 for thymidine. The chemistry of the radical cations involves hydration by water leading to C(6)‐OH adduct radicals of the pyrimidine and deprotonation from the N(l) position in thymine and the C(5) methyl group for thymidine. Superoxide ions produced via quenching of the quinone radical anion with oxygen appear to be involved in the formation of thymine and thymidine hydroperoxides and in the reaction with N(l)‐thyminyl radicals to regenerate thymine. The effects of pH were examined in the range pH 5–8 in both the presence and absence of superoxide dismutase. Initial C(6)‐OH thymine adducts are suggested to dehydrate to give N(l)‐thyminyl radicals.
PHOTO REACTION OF 4,5‘,8‐TRIMETHYLPSORALEN WITH ADENOSINE
Authors: Shim Sang Chul , Choi Seung Ju
Published: January 2008

Abstract— The near‐UV induced photoreaction of 4,5′,8‐trimethylpsoralen (TMP) with adenosine was investigated in a dry film state. Four major photoadducts were isolated and purified by reverse‐phase liquid chromatography. The structures of the photoproducts were elucidated on the basis of spectroscopic methods, including UV, FT‐IR, mass spectrometry (FAB and EI methods) and H‐NMR analysis. These photoproducts were characterized to be TMP‐adenosine 1:1 adducts, which resulted from the covalent bond formation between the carbon C(4) of TMP and ribose 1′ or 5′ carbon of adenosine. Of the photoadducts, one photoadduct (V) was the major product, reflecting some selectivity in the photoreaction of TMP with adenosine in the solid state.
IS SINGLET OXYGEN FORMATION DOMINANT IN TRIPLET QUENCHING PROCESSES? MEASUREMENT OF THE QUANTUM YIELD OF SINGLET OXYGEN FORMATION BY THE TIME‐RESOLVED THERMAL LENS METHOD
Authors: Terazima Masahide , Tonooka Mizuho , Azumi Tohru
Published: January 2008

The quantum yields of singlet oxygen formation (ØΔ) by the quenching of triplet states of organic sensitizers are measured at various concentrations of the sensitizers by using the time‐resolved thermal lens method. Above a certain concentration, ØΔ is independent of the sensitizer concentration. Below the threshold, ØΔ gradually decreases as the concentration of the sensitizer decreases. The extrapolation of ØΔ to zero concentration indicates that singlet oxygen formation is not necessarily dominant in the quenching process even for the 3ππ* state in benzene.
SPECTROSCOPIC OBSERVATION OF SOLVENT INTERACTION WITH SELECTED RETINAL SCHIFF BASES*
Authors: Blatz Paul E. , Mohler JonathanH. , Ahmed Wasi
Published: January 2008

Iodide salts of several N‐retinylidenedialkylamines were prepared and their UV‐VIS spectra recorded. Their γmax values increased as the number of hydrogen atoms on the carbons alpha to nitrogen increased. In separate experiments, iodide salts of N‐retinylidene‐n‐butylammonium (1) and N‐retinylidene‐n‐butylmethylammonium (2) were prepared, and their excitation energies (ΔE) were measured in selected solvents of varying dielectric constant Data from each compound gave a straight line which converged at ε= 0. On the other hand, when ΔE values of the iodide and bromide of 2 were plotted vs solvent e, parallel rather than convergent lines were obtained. When γmax values of 1 and 2 were measured in a greater number of solvents, the solvents fell into four main groups. The first group, regular solvents, are rigid, have fixed dipoles, neither donate nor accept H‐bonds, and the δE of 1 and 2 decreases linearly as solvent e increases. This line for 2 is taken as a standard against which other solvents are judged. A second class of solvents that are good H‐bond donors like CHCl3, whose dipole moment coincides with the CH bond axis, is located in an area below the standard line. A third group, nucleophilic solvents like tetrahydrofuran, whose dipole moment is coincident with a strongly nucleophilic oxygen atom are good H‐bond acceptors and are found above the standard line. Solvents with unpredictable spectroscopic behavior are classed as anomalous.
EXCITED‐STATE PROPERTIES OF THE ALTERNATING POLYNUCLEOTIDE POLY(dA‐dT)POLY(dA‐dT)
Authors: Ge G. , Georghiou S.
Published: January 2008

References

Measurements of the steady‐state fluorescence spectrum and anisotropy, r, of the alternating polynucleotide poly(dA‐dT)‐poly(dA‐dT) were carried out in order to characterize its photophysical properties at room temperature. The shape of the fluorescence spectrum depends on the excitation wavelength, namely, the relative fluorescence intensity of the short‐wavelength peak decreases for excitation at short wavelengths. When monitoring the emission at short wavelengths, r is 0.18 and independent of the excitation wavelength. When monitoring the emission at long wavelengths, however, r is very low, about 0.03. These results suggest that: (i) the short‐wavelength emission stems from thymine; and (ii) the long‐wavelength emission stems from an excited‐state complex (excimer), with the same one being formed regardless of whether thymine or adenine is excited. The corresponding fluorescence spectra have been resolved. The occurrence of transfer of electronic energy is discussed.
NON‐DIMER DNA DAMAGE IN CHINESE HAMSTER V‐79 CELLS EXPOSED TO ULTRAVIOLET‐B LIGHT
Authors: Matsumoto Kumi , Sugiyama Masayasu , Ogura Ryohei
Published: January 2008

Abstract—

To understand and characterize non‐dimer DNA damage and cytotoxicity induced by ultraviolet‐B light (UV‐B,290–320 nm), an alkaline elution technique for analysis of DNA damage was used on Chinese hamster V‐79 cells. Ultraviolet‐B exposure produced a dose‐dependent induction of DNA single strand breaks and DNA‐protein crosslinks; however, there was an absence of DNA‐DNA interstrand crosslinks. Neither of these types of DNA damage were repaired within a 24 h incubation of the cells following a single UV‐B exposure; rather the damage increased. Using a colony forming assay, we found that UV‐B exposure resulted in an increase of cytotoxicity in a dose‐dependent fashion. In addition, UV‐B exposure inhibited DNA and RNA synthesis. The role of non‐dimer DNA damage in the cytotoxicity induced by UV‐B is discussed.
LATITUDINAL AND SEASONAL VARIATION IN CALCULATED ULTRAVIOLET‐B IRRADIANCE FOR RICE‐GROWING REGIONS OF ASIA*
Authors: Bachelet D. , Barnes P. W. , Brown D. , Brown M.
Published: January 2008

Ultraviolet‐B (UV‐B,280–320 nm) irradiance was calculated for more than 1200 sites in Asia to characterize the spatial and temporal variation in the present UV‐B climate for rice‐growing regions. The analytical model of Green et al. (Photochem. Photobiol.31,59–65, 1980) was used to compute UV‐B irradiance for clear skies using satellite‐observed ozone column thickness and local elevation data. Ground‐based observations of cloud cover were then used to approximate the average effect of cloud cover on UV‐B irradiance using the approach of Johnson et al. (Photochem. Photobiol.23,179–188, 1976). Over the geographic range of rice cultivation, the maximum daily effective UV‐B irradiance (UV‐BBE), when weighted according to a general plant action spectrum, was found to vary approx. 2.5‐fold under both clear and cloudy sky conditions. Under clear skies, the timing of maximum solar UV‐BBE changed with latitude and varied from February‐March near the equator to July‐August at temperate locations. Cloud cover was found to alter the season of maximum UV‐BBE in many tropical regions, due to the pronounced monsoonal climate, but had little effect on UV‐B seasonality at higher latitudes. Under a climate resulting from a doubling of atmospheric carbon dioxide, estimated UV‐B using predicted cloud cover was found to change by up to 17% from present conditions in Thailand. Both latitudinal and seasonal variation in solar UV‐B radiation may be important aspects of the UV‐B climate for rice as cultivars differ in sensitivity to UV‐B and are grown under diverse conditions and locations.
CHARACTERIZATION OF THE (6‐4) PHOTOPRODUCT OF 2′‐DEOXYCYTIDYLYL‐(3′‐>5′)‐THYMIDINE AND OF ITS DEWAR VALENCE ISOMER
Authors: DOUKI T. , VOITURIEZ L. , CADET J.
Published: January 2008

Abstract—

Far‐UV irradiation of dCpT in aqueous solution was found to generate the corresponding pyrimidine (6‐4) pyrimidone photoadduct and the related Dewar valence isomer. The two photoproducts of dCpT were found to undergo deamination in aqueous solution, giving rise to the corresponding dUpT derivatives at a relatively slow rate. It was also shown that the Dewar isomer is much more alkali‐labile than its (6‐4) precursor.
PHOTOSENSITIZATION BY SYNTHETIC DIPORPHYRINS AND DICHLORINS in vivo AND in vitro
Authors: KESSEL DAVID , DOUGHERTY T. J. , CHANG C. K.
Published: January 2008

Abstract—

A group of polycarboxylic diporphyrins, two dichlorins and a porphyrin‐chlorin dimer, with rings linked by methylene groups, were examined to help identify structures which can mediate photodynamic tumor eradication in vivo. Among the features sought were short persistence of normal tissue photosensitization and substantial absorbance at wavelengths longer than 630 nm. Both objectives were achieved, with pertinent structure‐activity relationships partly characterized. The relative hydrophobicity of the different sensitizers was an important determinant of their accumulation in cell culture, but not of in vivo effectiveness. These compounds showed affinity for protein and high‐density lipoprotein components of serum. Their distribution may be mediated by a different mechanism than that which occurs with more hydrophobic sensitizers like hematoporphyrin derivative which have greater affinity for low‐density lipoproteins and less for protein components of serum, as compared with the products examined in this study.
DO PYRIMIDINE DIMER YIELDS CORRELATE WITH ERYTHEMA INDUCTION IN HUMAN SKIN IRRADIATED in situ WITH ULTRAVIOLET LIGHT (275–365 nm)?
Authors: HACHAM H. , FREEMAN S. E. , GANGE R. W. , MAYTUM D. J. , SUTHERLAND J. C. , SUTHERLAND B. M.
Published: January 2008

Abstract—

Ultraviolet radiation produces erythema in human skin, and damages the DNA of living cells in skin. Previous work showed that broad‐band UV‐B (290–320 nm) radiation produced higher levels of cyclobutyl pyrimidine dimers in DNA of individuals with high UV‐B sensitivity (low minimal erythema dose) than in subjects of low UV‐B sensitivity [Freeman et al. (1986) J. Invest. Dermatol., 86, 34–36]. We examined the relationship between erythema induction and dimer yields in DNA of human skin irradiated in situ with narrow band radiation spanning the wavelength range 275–365 nm. We find that, in general, higher dimer yields are produced per incident photon in volunteers with higher susceptibility to erythema induced by radiation of the same wavelength.
PHOTOACOUSTIC CALORIMETRY OF CYCLOHEPTENE DERIVATIVES. RELAXED TRIPLET ENERGIES OF 1‐PHENYLCYCLOHEPTENE AND 1, 3‐CYCLOHEPTADIENE AND THE ENERGETICS OF GROUND‐STATE cis‐trans ISOMERIZATION
Authors: BRENNAN COLIN M. , CALDWELL RICHARD A.
Published: January 2008

Abstract— The heat of isomerization Ect of cis‐1‐phenylcycloheptene (c‐PC7) to its highly strained trans isomer has been determined by a combination of a quantitative study of acid‐catalyzed trapping of the trans isomer with time‐resolved photoacoustic calorimetry. The relaxed triplet energy has been determined for PC7 and for cis, cis‐1, 3‐cycloheptadiene. The triplet energies are in line with previous studies of other alkenes but the Ect value is significantly higher than that calculated by molecular mechanics calculations for cycloheptene. The significance of the results for cis‐trans thermal isomerization is discussed.
UNSCHEDULED DNA SYNTHESIS: A QUANTITATIVE INDICATOR OF RESIDUAL IMMUNODETECTABLE PYRIMIDINE DIMERS IN HUMAN FIBROBLASTS AFTER ULTRAVIOLET‐B IRRADIATION
Authors: PLAZA SERGE , BOULLARD ANNIE , PELÉ DOMINIQUE , CORNELIS JAN J. , ROMMELAERE JEAN , GIACOMONI PAOLO U. , PRUNIERAS MICHEL
Published: January 2008

Abstract— We have addressed the question whether the level of UV‐B induced DNA damage can be accurately assessed by the measurement of the rate of unscheduled DNA synthesis (UDS). Cultured human fibroblasts were irradiated with UV radiation at 290, 313 or 365 nm. The LD50 was 85 J/m2 at 290 nm, 4500 J/m2 at 313 nm, and 70 kJ/m2 at 365 nm. The analysis of UDS measurements indicate complete arrest of repair processes within 24 h after irradiation, irrespective of the dose (in the range 10–60 J/m2 at 290 nm, and 250–1000 J/m2 at 313 nm). Irradiation at 365 nm failed to yield detectable evidence of UDS. Incubation of irradiated cells with an antiserum directed against both 6–4 type and cyclobutane‐type pyrimidine dimers shows a clear parallelism between the disappearance of the antibody‐binding determinants and the variation of the rate of UDS vs time after the end of the irradiation. Thus it is concluded that in UV‐B irradiated normal cultured human fibroblasts, the lack of UDS reflects the absence of immunodetectable pyrimidine dimers.
RED‐BLUE‐INTERACTION IN Mesotaenium CHLOROPLAST MOVEMENT: BLUE SEEMS TO STABILIZE THE TRANSIENT MEMORY OF THE PHYTOCHROME SIGNAL
Authors: KRAML M. , HERRMANN H.
Published: January 2008

Abstract— Fast chloroplast orientation in Mesotaenium from profile position to face position cannot be induced by either red (R) or blue (BL) light (in contrast to Mougeotia). Rather interaction of light signals mediated by phytochrome and blue‐light photoreceptor(s) is essential for the response. If both light treatments are separated in time, the irradiation sequence R‐BL is much more effective than BL‐R, i. e. a gradient of the far‐red (FR)‐absorbing form of phytochrome (Pfr) renders following BL highly effective, but BL cannot increase the responsiveness to following Pfr. The memory of a R irradiation before BL holds only for some minutes, indicating that the physiological activity of Mesotaenium‐Pfr and its photoproducts is very short‐lived. This transient signal mediated by Pfr can be transformed to a more stable internal signal by interaction with BL. The interaction process does not occur at the level of photoperception. Rather, early products of the phytochrome‐initiated signal transduction chain interact with excited cryptochrome or an early product of it; Pfr can be removed by FR before the onset of BL. The internal signal stores the directional information of the Pfr‐gradient, so that BL is now fully effective and induces chloroplast movement.
GLOBAL ANALYSIS OF THE TIME‐RESOL VED FLUORESCENCE OF α‐CHYMOTRYPSINOGEN A AND α‐CHYMOTRYPSIN POWDERS AS A FUNCTION OF HYDRATION
Authors: VERMUNICHT GEERT , BOENS NOËL , SCHRYVER FRANS C. DE
Published: January 2008

Abstract— The time‐resolved tryptophyl fluorescence of α‐chymotrypsinogen A and α‐chymotrypsin in the crystalline state and in buffer solution at room temperature was analyzed globally. Tripleexponential decay functions are necessary to adequately describe the tryptophyl fluorescence decay surfaces of the protein powders as a function of hydration and in solution. The fluorescence lifetimes of α‐chymotrypsinogen A (τ1= 0.32 ns. τ2= 1.30 ns. τ3= 3.98 ns) and α‐chymotrypsin (τ1= 0.66 ns. τ2= 2.26 ns. τ3= 5.40 ns) are constant over the entire hydration range. The spectral positions of the decay‐associated spectra of the hydrated powders do not shift as a function of hydration. This indicates that the structures of the zymogen and the active enzyme are unaffected by hydration. The lifetimes of α‐chymotrypsinogen A in phosphate buffer pH 7.4 are τ1= 0.37 ns, τ2= 1.17 ns and τ3= 3.44 ns while the respective values of α‐chymotrypsin are τ1= 0.47 ns. τ2= 1.40 ns and τ3= 3.89 ns.
THE EFFECT OF HIGH AND LOW ULTRAVIOLET‐B DOSE EXPOSURE ON THE DEGREE OF HAIRLESS MOUSE SKIN WRINKLING
Authors: KISS ILONA , CHEN SIMON , TRAMPOSCH KENNETH M.
Published: January 2008

Abstract— Chronic exposure of hairless mice to ultraviolet light (UVB 290‐320 nm) causes degradative changes in the dermal matrix and wrinkle production. We compared the effects of two different UVB dosing regimens on wrinkle production and dermal damage in female Skh:HR‐1 hairless mice using a bank of unfiltered FS‐40 lamps. One group of mice, the low dose group, was exposed to a suberythemal UVB dose of 12 mJ/cm2 (1 MED = 14 mJ/cm2), 3 times per week for 20 weeks (total dose = 0.72 J/cm2). A second group, the high dose group, was exposed also 3 times per week for 15 weeks to a UVB dose which started with the sub‐erythemal dose of 12 mJ/cm3 at Week 1. and J MED at week 2. The dose was then increased weekly by 1 MED until reaching 4 MED at week 5. The animals were then dosed at 4 MED for 10 additional weeks (total dose = 2.1 J/cm2). Visual results indicate that, as expected, within the same group, the degree of wrinkling was generally dependent on the total UVB dose administered. However, comparison between the low dose and high dose groups shows that equal cumulative UVB doses did not always result in identical wrinkle grades. For example. at a cumulative dose of 0.5 J/cm2, the mean wrinkle grade for the low dose group was 1.75 compared to that of 1.2 for the high dose group (age‐matched = 0). This observation may suggest that there are other factors in addition to total cumulative dose which are important for the appearance of wrinkling in this model.
COVALENTLY LINKED TYROSINE‐PYROPHEOPHORBIDE a AND TRYPTOPHAN‐PYROPHEOPHORBIDE a COMPOUNDS: SYNTHESIS AND PHOTO‐INDUCED CROSS COUPLING WITH 1, 4‐BENZOQUINONE
Authors: MARUYAMA KAZUHIRO , YAMADA HIROKO , OSUKA ATSUHIRO
Published: January 2008

Abstract— Tyrosine‐linked pyropheophorbide a (2) and tryptophan‐linked pyropheophorbide a (3) were synthesized. Neither the phenol group of the tyrosine end nor the indole group of the tryptophan end showed upfield shifts as observed for the tyrosine‐linked mesoporphyrin II (17) and the tryptophanlinked mesoporphyrin II (18). When the keto group at the C‐9 of 2 and 3 was reduced to methylene group [tyrosine‐linked 9‐deoxopyropheophorbide a (5) and tryptophan‐linked 9‐deoxopyropheophorbide a (6)], the phenol group of the tyrosine and the indole group of the tryptophan showed upfield shifts, indicating the intramolecular hydrogen bonds between amino acid moieties and the keto group at the C‐9 in 2 and 3. Irradiation of 2 and 1,4‐benzoquinone (BQ) in benzene led to a clean formation of a quinone‐linked pyropheophorbide a (8) in 56% yield. Triplet radical pair composed of tyrosine radical and semiquinone radical was assigned as the reaction intermediate for the formation of 8 by means of CIDNP technique. Irradiation of 5 under the identical conditions led to the formation of benzoquinone‐linked 9‐deoxo‐mesopyropheophorbide a (10) and benzoquinone‐linked 9‐deoxophylloerythrin a (11) in 45 and 22%, respectively. Magnesium and zinc complexes of 2 underwent the similar photoaddition reaction much less efficiently. However, irradiation of the tryptophan‐linked model compounds 3 and 6 in the presence of BQ did not give the coupling product.
ANALYSIS OF PHOTO‐OXIDIZED AMINO ACIDS IN TRYPTIC PEPTIDES OF CALF LENS γ‐II CRYSTALLIN
Authors: Hott J. L. , Borkman R. F.
Published: January 2008

Abstract—

Insoluble and crosslinked proteins and increased pigmentation in the eye lens are features of aging and cataracts. Determining the amino acids which are involved in insolubilization, crosslinking and visible light scattering will shed light on the mechanisms by which cataracts form. Calf lens γ‐II crystallin was irradiated at 295 nm, digested and separated into tryptic peptides. Additional tryptic peptides were found in the digest of irradiated γ‐II which were not present in the dark control digest. These peptides were identified by amino acid sequencing and shown to correspond to expected tryptic fragments of the protein, indicating more facile digestion in the UV‐irradiated protein than in dark controls. Amino acid analysis of the irradiated protein and peptides showed losses of histidine. methionine and cysteine residues as compared to control samples. Tryptophan, which is not detected by amino acid analysis, was also found to be reactive since losses in its fluorescence intensity were observed after irradiation. Some of the photochemically active amino acids had lower than expected responses in amino acid sequencing experiments. This suggested specific sites of photochemical activity in the various peptides. The evidence for peptide crosslinks is also discussed.
INDUCTION OF A TRANSIENT ENHANCEMENT OF LOW LEVEL CHEMILUMINESCENCE IN INTACT LEAVES BY ANAEROBIC TREATMENT
Authors: Roschger P. , Devaraj B. , Scott R. Q. , Inaba H.
Published: January 2008

Abstract—

Intrinsic low level chemiluminescence of dark adapted intact leaves exhibits a transient enhancement of light emission when ambient air is replaced with an anaerobic atmosphere. Re establishing aerobic conditions gives rise to a complex kinetic behavior of the light emission in the post‐anoxic phase. Metabolic changes within the leaf are suggested to be responsible for this phenom enon, where intactness of the leaf is found to be of crucial importance. Leaf homogenate showed nearly oxygen independent chemiluminescence. In contrast, low level chemiluminescence of UV‐light damaged leaves and of chloroplast preparations was inhibited by oxygen depletion. Spectral analyses of the ultraweak light emission from the intact leaf indicates that in both aerobic and anaerobic cases, the source of the ultraweak light is the same. The similarity to the spectrum of delayed fluorescence also obtained from the leaf suggests that chlorophyll is the light emitting species.
In vivo EXPOSURE TO ULTRAVIOLET RADIATION ENHANCES PATHOGENIC EFFECTS OF MURINE LEUKEMIA VIRUS, LP‐BMS, IN MURINE ACQUIRED IMMUNODEFICIENCY SYNDROME
Authors: Brotek Celestyn M. , Shopp George M. , Ryan Sharon L , Gillespie Patricia M. , Kusewitt Donna F. , Rajagopalan M. S. , Ley Kenneth D. , Ley Ronald D.
Published: January 2008

Abstract—

LP‐BM5 murine leukemia virus (MuLV) induces an immunodeticiiency syndrome (MAIDS) in C57BL/6 mice which resembles immunological abnormalities observed in early stages of human AIDS. In our study, MAIDS virus‐infected mice were exposed to low doses of ultraviolet radiation (UVR) before and after virus inoculation and compared with MAIDS‐infected but not UVRcxposed mice. In all tested parameters (blood IgM levels; mitogenic responses to PHA. ConA, LPS and anti‐μ MLR antigenic response to SRBC, enlargement and histopathologic changes of the spleen) we observed the same trend: changes due to MAIDS infection were more pronounced in the UVR‐eposed group than in the unexposed group. Statistically significant differences between these two groups were Seen for mitogenic responses at two different time points after virus inoculation. These results demonstrate that in vivo UVR exposure enhances the immunosuppressive effects of a retroviral infection. UVR exposure may affect the progression of AIDS in a similar manner.
A MODEL FOR THE MOLECULAR STRUCTURE AND ORIENTATION OF THE CHROMOPHORE IN A DIMERIC PHYTOCHROME MOLECULE*
Authors: Tokutomi Satoru , Sugimoto Tohru , Mimuro Mamoru
Published: January 2008

Abstract—

A model for the molecular structure and orientation of red‐light absorbing form of phytochrome (P,) chromophores in a dimeric molecular model of Pr is proposed. A chromophore model with probable molecular structures was generated to reproduce the absorption spectrum produced by its π‐electron conjugating system. The model has C5‐Z, syn, C10‐E, anti and C15‐Z, syn configurations and a protonation at a C‐ring nitrogen. Orientation of the chromophore model in the dimeric phytochrome molecular was analyzed by displaying the atoms of the chromophore, the coordinates of which were converted into those with respect to the molecular axes to the dimeric molecule, on a 3‐D graphic workstation. The conversions were performed by using the azimuthal angles between the Z axis of the dimeric molecule (axis of 2‐fold rotational symmetry) and the dipole moments of the electronic transition at the blue‐ (384 nm) and red‐ (667 nm) absorbing bands of the chromophore, which were calculated as 55.5° and 59.3°, respectively, based on linear dichroism of the oriented phytochrome molecules. The result demonstrates that the long axis of the P, chromophore lies almost parallel to the Y axis of the molecular model, and that the tetrapyrrolic chromophore is well contained within the flat chromophoric domain without protruding from it, a configuration that assures that the chromophore is protected against aqueous environments. The model may explain the rotation angle of the transition moment of the red‐absorbing band, induced by the phototransformation from Pr to Prr which we measured as smaller than that measured in nonoriented preparations by a photoselection technique. The model also suggests a molecular basis for the polarotropic response of phytochrome.
In vivoPHYTOCHROME‐MEDIATED PERCEPTION OF REFLECTED LIGHT SIGNALS
Authors: Mancinelli Alberto L. , Hobert Oliver , Nikas George
Published: January 2008

Abstract—

The spectrophotometric assay of phytochromein vivoin etiolated plant material was used to determine the effects of changes in reflected light on the state of the photoreceptor in etiolated seedlings exposed simultaneously to direct and reflected light. Changes in reflected light that were small in terms of the total (direct + reflected) radiation incident on the seedlings produced detectable changes in the state of phytochromein vivo. The contribution of reflected light to the state of phytochrome in vertical organs was greater than expected from its low contribution to total incident light. These data from laboratory studies complement and are consistent with results of field studies on the effects of light reflected from neighboring vegetation on plant growth under natural radiation conditions.
PHYTOCHROME PHOTOCONVERSIONin vivo. EFFECT OF THE INITIAL Pfr/Ptot RATIO
Authors: Mancinelli Alberto L. , Rossr Federica , Moroni Anna
Published: January 2008

Abstract—

The equation for phytochrome photoconversion, derived from photoconversion kinetics of purified phytochrome, predicts that the rates of photoconversions starting from low and high Pfr/Ptot(0), (initial Pfr/Ptot) should be the same for light of the same quality and fluence rate. The situation might be differentin vivo. Phytochrome photoconversion rates were measured in excised cotyledons ofCucurbita pepoL. exposed to BL (blue; ϕBL= 0.39; ϕ, Pfr/Ptot at photoequilibrium) and RI (mixture of red and far red; ϕRI= 0.46) after saturating preirradiations with red and far‐red to establish high (0.78) and low (0.02) Pfr/Ptot(0), respectively. Under BL, the rate of photoconversion is faster when starting from a high than a low Pfr/Ptot(0); under RI, the rate of photoconversion is faster when starting from a low than a high Pfr/Ptot(0)., No effects of Pfr/Ptot(0), on photoconversion rates were found in phytochrome solutions exposed to BL and RI. These data provide another indication of the discrepancies between phytochrome photconversion kineticsin vivoandin vitro.
NITRATE EFFECT ON Pfr‐MEDIATED AND GA3‐INDUCED GERMINATION IN SPORES OF Anemia phyllitidis (L.) Sw*
Authors: Haas Christian J. , Kopp Hannelore , Scheruerlein Robert
Published: January 2008

Abstract—

Spore germination in Anemia phyllitidis can be induced by red light (R) via the phytochrome system and by gibberellic acid (GA3) in the dark. An enhancing effect of NO3‐ions on the Pfr‐mediated germination could be demonstrated. This NO3‐effect was found to be pronounced during the preinduction phase and could be described by biphasic kinetics depending on the formation of Pfr by the R‐irradiation. Besides NO3, other electron accepting substances also increased germination significantly. In contrast to Pfr‐mediated germination, no enhancing effect by NO3 could be obtained for the GA3‐induced germination response. The application of an inhibitor of gibberellic acid synthesis, AMO1618, as well as the analysis of combined R and GA3 treatment, support the hypothesis that for germination of Anemia phyllitidis spores no synergism between the factors exists. Thus, it is proposed that the gibberellic acid receptor starts a signal‐transduction pathway resulting in germination which is in part independent of the Pfr‐mediated signal‐transduction chain. The NO3‐effect is specific for the Pfr‐mediated signal‐transduction chain.
PHYTOCHROME REGULATION OF MORPHOGENESIS IN GREEN PLANTS: FROM THE BELTSVILLE SPECTROGRAPH TO COLORED MULCH IN THE FIELD*
Authors: Kasperbauer Michael J.
Published: January 2008

Abstract—

Development of the theory and use of photon ratios reflected from colored mulches to regulate plant morphogenesis in the field utilized information obtained on the Beltsville Spectrograph, in controlled environments and in field plant spacing studies. An upwardly reflected far‐red to red (FR/R) ratio higher than the ratio in incoming sunlight resulted in larger shoots and a higher shoot/root biomass ratio. A reflected FR/R ratio lower than the ratio in incoming sunlight resulted in larger roots and a lower shoot/root biomass ratio.
PHYCOERYTHROCYANINS FROMWestiellopsis prolificaANDNostoc rivulare: CHARACTERIZATION OF THE PHYCOVIOLOBILIN CHROMOPHORE IN BOTH STATES*
Authors: Sai P. S. Maruthi , Siebzehnrübl S. , Mahajan S. , Scheer H.
Published: January 2008

Abstract—Phycoerythrocyanin or fractions enriched in it have been isolated from the filamentous cyanobacteria,Westiellopsis prolificaARM 365 andNostoc rivulareARM 212. Both show the photoreversible photochromism (difference maxima at 503 and 570 nm) characteristic of this pigment, which is related to the phycoviolobilin chromophore on the α‐subunit. Native phycoerythrocyanin and its β‐subunit show little if any reversible photochemistry in the 600–620 nm region, where the phycocyanobilin chromophores absorb maximally. Instead the phycocyanobilin chromophores are bleached irreversibly. At the same time, the data show that reversible photochemistry is a useful analytical tool to detect phycoerythrocyanin in cyanobacterial extracts. Fluorescence measurements indicate that: (i) the 510 nm absorbing isomer of the violobilin chromophore has only little fluorescence; and (ii) the energy transfer from the violobilin chromophores to the cyanin chromophores is efficient only in the 570 nm form.
WAVELENGTH DEPENDENCE OF PHOTOINDUCED PEROXIDATION AND CYTOTOXICITY OF HUMAN LOW DENSITY LIPOPROTEINS
Authors: Nègre‐Salvayre Anne , Paillous Nicole , Dousset Nicole , Bascoul Jacques , Salvayre Robert
Published: January 2008

Abstract— The relative abilities of UV‐A, B and C radiations to initiate lipid peroxidation and apolipoprotein (apo) B modification of human purified low density lipoproteins have been compared. Ultraviolet‐B and C (at 310 and 254 nm, respectively) exhibited similar efficacy as shown by the increase in lipid peroxidation markers (conjugated dienes, thiobarbituric acid reactive substances and fluorescent lipid soluble products) and in oxysterols, as well as by the decrease of the contents of natural antioxidants (tocopherols and carotenes) and in polyunsaturated fatty acids. In contrast, UV‐A (at 360 nm) was found poorly effective and only at very high radiation intensities. Under all the conditions used, apoB was not affected by the UV radiations as shown by the stability of amino acid composition (except tryptophan level) and of trinitrobenzenesulfonic acid reactive amino group content. Similarly, the low density lipoprotein size was not altered. By comparison, low density lipoproteins oxidized by transition metal presented strong alterations of apoB and major changes of the apparent low density lipoprotein size.

Finally, low density lipoproteins irradiated by UV‐B or C exhibited a much higher cytotoxicity on cultured cells than those irradiated by UV‐A. Under the conditions used in this paper, the cytotoxic effect of the irradiated low density lipoproteins was positively correlated with their content in lipid peroxidation products and inversely correlated with their tocopherol content.
THE INFLUENCE OF FLUORESCENCE CONCENTRATION QUENCHING ON THE EMISSION ANISOTROPY OF FLAVINS IN GLYCERINE‐WATER SOLUTIONS
Authors: Grajek H. , Bojarski C. , Zurkowska G. , Drabent R.
Published: January 2008

Abstract— The measurements of the emission anisotropy r/r0 of flavomononucleotide (FMN) within a range of concentrations of 10–5–10‐1mol/L in glycerine‐water solutions of different viscosities‐0.056 Pa/s (system I) and 0.256 Pa/s (system II) have been carried out.

In the range of high concentrations the repolarization effect due to the sharp drop of the quantum yield has been observed.

The experimental results have been compared with theoretical expressions evaluated by taking into account both concentration and rotation depolarization. A good agreement on the values of the theoretical parameters obtained from independent measurements has been found.

It has been stated that in the investigated systems the excitation energy transfer may be treated as a Markov process.
CYCLIC VOLTAMMETRY MEASUREMENTS OF THE PHOTOELECTROGENIC REACTIONS OF THYLAKOID MEMBRANES
Authors: Agostiano Angela , Goetze D. Christopher , Carpentier Robert
Published: January 2008

Abstract— In this paper, the technique of cyclic voltammetry has been used in a photoelectrochemical cell in order to follow the redox species formed in solution by the photo‐induced electron transfer between the thylakoids and various acceptors and donors. The photoelectrochemical behavior of artificial electron acceptors (such as 2,5‐dichlorobenzoquinone and methylviologen) and donors (such as sym‐diphenylcarbazide and durohydroquinone) specific for either Photosystem I or Photosystem II has been investigated. The influence of inhibiting agents (such as 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea and Tris) on the cell photoresponse has also been characterized, together with the capability of donors to restore the photocurrent. Evidence for H2O2 formation by way of a Mehler‐type reaction has been provided and an electrochemical model of its coupled photochemical and electrochemical reactions in solution is reported.
A NOVEL PHOTOADDUCT OF 4,5',8‐TRIMETHYLPSORALEN AND ADENOSINE
Authors: Yun Mi Hong , Choi Seung Ju , Shim Sang Chul
Published: January 2008

Abstract— A novel photoadduct of 4,5',8‐trimethylpsoralen (TMP) and adenosine was isolated and purified by reverse‐phase liquid chromatography. The structure of the photoproduct was determined by various spectral methods and found to be a TMP‐adenosine 1:1 adduct resulting from the covalent bond formation between the carbon C(4) of TMP and ribose 4'‐carbon of adenosine.
DISTRIBUTION OF DI‐SULFONATED ALUMINUM PHTHALOCYANINE AND PHOTOFRIN II IN LIVING CELLS: A COMPARATIVE FLUOROMETRIC STUDY
Authors: Bottiroli G. , Croce A. C. , Ramponi R. , Vaghi P.
Published: January 2008

Abstract— Microspectrofluoromeric and fluorescence imaging techniques have been employed to study the internalization and intracellular distribution of both Photofrin II, an experimental drug used in photodynamic therapy, and di‐sulfonated aluminum phthalocyanine, a very promising photosensitizer. The results obtained by microscopic techniques in living cells have been compared with those obtained in solution on cell extracts. Experimental results indicated that the complexity of the drug‐cell interaction can be explained according to the chemico‐physical nature of the drugs. In particular, the presence of both monomeric and aggregated fractions, which are supposed to be internalized through different mechanisms, accounts for the intracellular distributions observed for both drugs, depending on the treatment conditions. Equilibria among the drug fractions take place within the cells, resulting in the persistence of the intracellular fluorescence. On the whole, the behavior of the two drugs appears very similar, except for some aspects related to the intracellular distribution, which can be explained in terms of different degree of lipophilicity of the drugs.
UPTAKE AND RETENTION OF PHOTOFRIN® BY CULTIVATED HUMAN LYMPHOBLASTIC CELLS (Reh6): PREFERENTIAL AFFINITY OF THE CELLS FOR A MINOR COMPONENT DEMONSTRATED BY NORMAL PHASE CHROMATOGRAPHY
Authors: Dellinger M. , Brault D.
Published: January 2008

Abstract— The uptake of Photofrin® by the human cultivated lymphoblastic cell line Reh6 was studied using normal phase high performance liquid chromatography (HPLC) techniques. Relative cellular uptake of eight fractions (uptake/amount of component initially present in the incubation solution) was determined. After 4 h of incubation, protoporphyrin and a small fraction (denoted 4) were incorporated to a greater relative extent than the other fractions. Weakly incorporated components (hematoporphyrin and aggregate‐like components) were better retained by cells than the hydrophobic monomeric porphyrins (protoporphyrin and hydroxyethylvinyldeuteroporphyrin). Thus, any benefit gained from a higher uptake was mostly cancelled by a fast release—a situation observed for all fractions except for fraction 4, which displayed both high uptake and good cellular retention. This pattern was not modified when Photofrin® concentration or serum percentage was changed. Fraction 4 was further resolved using a gradient system on normal silica. A single component appeared to be mostly responsible for the favorable properties presented by fraction 4, i.e. high uptake and retention within cells. This component was found to correspond to a late eluted peak in the typical reverse‐phase HPLC profile of Photofrin®. These results emphasize the possible role of minor Photofrin® components.
IRON‐SULFUR CENTERS AS ENDOGENOUS BLUE LIGHT SENSITIZERS IN CELLS: A STUDY WITH AN ARTIFICIAL NON‐HEME IRON PROTEIN
Authors: Kim Chang Sook , Jung Jin
Published: January 2008

Abstract— The possible involvement of Fe‐S clusters in photodynamic reactions as endogenous sensitizing chromophores in cells has been investigated, by using an artificial non‐heme iron protein (ANHIP) derived from bovine serum albumin and ferredoxins isolated from spinach and a red marine algae. Ferredoxins and ANHIP, when exposed to visible light, generate singlet oxygen, as measured by the imidazole plus RNO method. Irradiation with intense blue light of the ANHIP‐entrapped liposomes caused severe membrane‐damage such as liposomal lysis and lipid peroxidation. In the presence of ANHIP, isocitrate dehydrogenase and fructose‐l, 6‐diphosphatase were photoinactivated by blue light. However, all of these photosensitized reactions were significantly suppressed by a singlet oxygen (1O2) quencher, azide, but enhanced by a medium containing deuterium oxide. Further, the Fe‐S proteins with the prosthetic groups destroyed did not initiate the blue light‐induced reactions. In addition, the action spectrum for 1O2 generation from ANHIP was very similar to the visible absorption spectrum of Fe‐S centers. The results obtained in this investigation appear consistent with the suggestion that Fe‐S centers are involved in photosensitization in cells via a singlet oxygen mechanism.
ROOM‐TEMPERATURE STEADY‐STATE FLUORESCENCE PROPERTIES OF POLY(dG‐dC).SPOLY(dG‐dC)
Authors: Huang C.‐R. , Georghiou S.
Published: January 2008

Abstract— We report the steady‐state fluorescence properties of the alternating polynucleotide poly(dG‐dC).poly(dG‐dC) in low‐salt solution at room temperature for excitation at the Hg lines 265, 280 and 297 nm. Its fluorescence spectrum peaks at about 325 nm and, within the experimental error, its shape does not change significantly with the excitation wavelength. The fluorescence anisotropy is found to decrease strongly for short‐wavelength excitation, a behavior which is very similar to that exhibited by free guanine. In view of the fact that the anisotropy for free cytosine is virtually constant at the aforementioned three excitation wavelengths, the results suggest that in this polynucleotide the emission stems from guanine. The values of the fluorescence quantum yield for the three excitation wavelengths are found to be very low, 0.8 times 10‐5 0.8 times 10‐5 2.8 times 10‐5 respectively; these are compatible with transfer of energy from the lower‐energy electronic state of guanine, before vibronic relaxation is established, to cytosine. Upon denaturation, the fluorescence spectrum becomes very broad and the fluorescence quantum yield increases; these observations support the authenticity of the emission from the nondenatured polynucleotide.
LIFETIMES OF BACTERIOCHLOROPHYLL FLUORESCENCE IN Rhodopseudomonas viridis AND Heliobacterium chlorum AT LOW TEMPERATURES
Authors: Kleinherenbrink F. A. M. , Cheng P. , Amesz J. , Blankenship R. E.
Published: January 2008

Fluorescence lifetimes of isolated membranes of Rhodopseudomonas viridis were measured in the temperature range of 77 K to 25 K. At room temperature, the main component of the fluorescence decay of bacteriochloro‐phyll (BChl) b had a time constant of 50 ps. In contrast to other purple bacteria, the emission at low temperature was spectrally homogeneous and showed essentially single lifetimes of 140 ps at 77 K and 180 ps at 25 K, with the primary electron donor in the oxidized state. Taking into account the relative fluorescence yields with open and closed reaction centers, we arrive at numbers of 125 ps and 215 ps, respectively, for open reaction centers. These numbers are significantly smaller than expected on the basis of measurements of the efficiency of charge separation, perhaps suggesting that the excitation decay in the absence of reaction centers is considerably faster at low temperature than at room temperature. At least four different spectral components with different lifetimes were observed at 25 K in the emission of Heliobacterium chlorum, a short‐wavelength component of about 30 ps and three longer‐wavelength components of about 100 ps, 300 ps, and 900 ps. This indicates a strong heterogeneity in the emitting pigment, BChl g‐808. The component with the shortest lifetime does not appear to be affected by the redox state of the reaction center and might reflect energy transfer to BChl g species which are connected to the reaction center.
THE MAJOR INTRINSIC LIGHT‐HARVESTING PROTEIN OF Amphidinium: CHARACTERIZATION AND RELATION TO OTHER LIGHT‐HARVESTING PROTEINS
Authors: Hiller Roger G. , Wrench Pamela M. , Gooley Andrew P. , Shoebridge Grant , Breton Jacques
Published: January 2008

A major light‐harvesting complex (LHC) has been obtained from thylakoids of Amphidinium carterae solubilized with digitonin or decylmaltoside and separated by sucrose‐gradient centrifugation. The digitonin‐LHC forms a dark brown band at ‐17% sucrose and the decylmaltoside LHC one at ‐7% sucrose. Excellent energy transfer is retained from chlorophyll c and carotenoid to chlorophyll a. Absorbance and fluorescence excitation spectra show the existence of two major forms of chlorophyll c, one absorbing at 634 nm and the other at 649 nm. Linear dichroism spectra show the Qy transition of both forms of chlorophyll c to be aligned at <35° to the membrane plane. On sodium dodecylsulfate polyacrylamide gels the complex resolves as a single band of 19 kDa. A partial amino acid sequence shows the N‐terminus to be unblocked but modified; there is a persistent ambiguity of Ser/Asn at residue 4 and evidence for multiple but very similar polypeptides within the 19 kDa band. The peptide has strong identity with the N‐terminal regions of LHC from Phaeodactylum and Pavlova and LHC 1 of higher plants. Antibodies to the 19 kDa peptide react weakly with LHC of brown algae, diatoms and Prymnesiophytes but not with those of higher plants or Cryptophytes.
STRUCTURAL RELATIONSHIPS OF THE PHOTOSYSTEM I AND PHOTOSYSTEM II CHLOROPHYLL a/b AND a/c LIGHT‐HARVESTING APOPROTEINS OF PLANTS AND ALGAE
Authors: Plumley F. Gerald , Martinson Tracey A. , Herrin David L. , Ikeuchi Masahiko , Schmidt Gregory W.
Published: January 2008

Polyclonal antibodies against four different apoproteins of either the chlorophyll (Chl) a/b light‐harvesting antenna of photosystem I or II, or a chlorophyll‐protein complex homologous to CP26 from Chlamydomonas reinhardtii, crossreact with11–13 thylakoid proteins of Chlamydomonas, Euglena gracilis and higher plants. The number of antigenically‐related proteins correlates with the quantity of light‐harvesting chlorophyll‐protein complex (LHC) gene types that have been sequenced in higher plants. The antibodies also react specifically with Chi a/c‐binding proteins of three diatoms and Coccolithophora sp. as determined by immunoblot and Ouchterlony assays. Four to six crossreacting proteins are observed in each chromophyte species and a functional role for some can be deduced by antibody reactivity. It appears that despite major differences in the structures of their pigment ligands, at least some domains of Chl‐binding LHC apoproteins have been conserved during their evolution, possibly functioning in protein: protein, as opposed to pigment: protein, interactions in photosynthetic membranes.