bluuebunny/crossref_metadata_2025 huggingface dataset:
DIFFERENTIAL SPECTROPHOTOMETRY OF Phycomyces MUTANTS WITH ABNORMAL PHOTORESPONSES
Authors: Horwitz Benjamin A. , Trad Chafia H. , Lipson Edward D.
Published: January 2008

Abstract— The unidentified receptor pigments responsible for phototropism and other blue light responses of Phycomyces are expected to contribute only a minuscule fraction of the in vivo absorption spectra, even for carotene‐deficient (car genotype) albino strains. The variable amount of residual carotenoids in strains with mutations in the carA gene precluded their use for the comparison of phototropism (mad) mutants with phototropically normal controls. We turned instead to carB albino strains, all of which have negligible carotene content. For various mad genes, we isolated carB mad strains by crosses and mutagenesis, and compared them with carB controls, in search of spectral differences associated with the mad photoreception defects. The spectra and their second derivatives show cytochrome bands, as well as a minor peak near 480 nm. This peak was present in carB strains, so it is probably not due to carotenoids. Strains L26 and L136 (both carB madE, but with different genetic backgrounds) showed modifications in the480–500 nm region. Sporangiophores that lacked the green material that usually interferes with in vivo spectroscopy were obtained by the addition of potassium iodide to the culture medium. Dark‐grown carB sporangiophores have a more pronounced second‐derivative peak at 480 nm than do light‐grown sporangiophores. Growth in the light, though, did not significantly alter the spectra of sporangiophores of L131 (carB madB) or L130 (carB madC). The spectral differences may be useful in the biochemical search for the receptor pigments.
AN EXTENDED SEMI‐EMPIRICAL MOLECULAR ORBITAL STUDY OF THE * EXCITED STATES OF NUCLEIC ACID BASES
Authors: Callis Patrik R.
Published: January 2008

Spectroscopic CNDO/S and INDO/S calculations of the * spectra of the nucleic acid bases uracil, cytosine, adenine and guanine were performed. Oscillator strengths, polarizations and transition densities are displayed for transitions to 140 nm using several parameter sets and demonstrating the effect of doubly excited configurations. Inclusion of near‐neighbor off‐diagonal transition density elements greatly assists in making state correlations and assignments. Interesting effects regarding electron repulsion parameterization are noted. The results are compared with recently reported experimental results and several serious points of disagreement are noted.
A MICROSPECTROFLUOROMETRIC STUDY OF PORPHYRIN‐PHOTOSENSITIZED SINGLE LIVING CELLS—II. METABOLIC ALTERATIONS
Authors: Kohen E. , Reyftmann J. P. , Morliere P. , Santus R. , Kohen C. , Mangel W. F. , Dubertret L. , Hirschberg J. G.
Published: January 2008

The transient change in the NAD(P)H NAD(P) equilibrium following microinjection of mitochondrial (malate) or extra‐mitochondrial (6‐phosphogluconate) substrates into single living cells is strongly modified a few seconds after the onset of 365 nm irradiation in the presence of hematoporphyrin. There is no major difference in the time frame for the alterations of the Krebs cycle and pentose pathway. In view of the complex interrelationships between mitochondrial and extramitochondrial pathways, there is a reasonable chance that effects on both pathways are not unrelated‐ However there is no definite evidence for a direct correlation between the photoeffects on these two pathways.
PHOTOTAUTOMERISM OF HARMALINE AND HARMALOL IN THE EXCITED SINGLET STATE
Authors: Krishnamurthy Mannam , Dogra Sneh K.
Published: January 2008

Unusual behaviour of harmaline and harmalol by excited state proton transfer has been studied and the acidity constants for the different prototropic equilibria in the ground and excited singlet states have been reported.
ON THE ASSESSMENT OF MELANIN IN HUMAN SKIN in vivo*, †.
Authors: Kollias N. , Baqer Ali
Published: January 2008

Abstract— A method for estimating the amount of pigment in normal human skin in uivo is presented. This method is based on remittance spectroscopy. The spectrum of normal skin is compared to amelanotic skin and the logarithm of the ratio is fitted with a straight line in the range 620‐720 nm. The parameters obtained are strongly correlated for all the volunteers in this study. therefore each spectrum determines one parameter for each individual. When similar analysis was performed on DOPA‐melanin we obtained the same strong correlation among different concentrations. We are thus able to determine a relation between the coefficient obtained from the remittance spectrum from normal skin and an equivalent concentration of DOPA‐melanin in aqueous solution. We can thus estimate. to a first approximation, the total melanin mass in human skin non‐invasively, and can determine a parameter that is uniquely correlated to the amount of melanin pigment in the skin.
ULTRA‐LOW‐LIGHT LEVEL CAMERA FOR PHOTON COUNTING IMAGING
Authors: Hayakawa Tsuyoshi , Kinoshita Katsuyuki , Miyaki Sueo , Fujiwake Hideshi , Ohsuka Shinji
Published: January 2008

Abstract— A new ultra‐low‐light level camera svstem has been developed to detect a single photon. Operation principles and some characteristics are presented.
STOICHIOMETRY OF THE REDOX CHANGES OF MANGANESE DURING THE PHOTOSYNTHETIC WATER OXIDATION CYCLE
Authors: Lavergne J.
Published: January 2008

Abstract—The UV absorbance change associated with the oxygen‐evolution cycle is investigated as to its correlation with the successive redox (S‐) states of the system. This change is probably due to a manganese oxidation within a multinuclear Mn‐cluster. The stoichiometry of its formation and destruction during the S‐cycle has been a matter of controversy: (0,1,0,‐1) according to velthuys, B. R. (1981) inPhotosynthesis II, (Edited by G. Akoyunoglou), pp. 75–85. Balaban International Science Services, Philadelphia, or (1, 1, 1, ‐3) according to Dekker, J. P., Van Gorkom, H. J., Wensink, J. and Ouwehand, L. (1984)Biochim. Biophys. Acta767, 1–9. We show that the data obtained in flash‐series experiments on dark‐adapted material may be fitted as satisfactorily by both models. More discriminating tests were devised, varying parameters such as the double‐hits probability or the initial distribution of the S‐states. These experiments clearly indicate that no (or little) absorbance change occurs both upon S0→S1and S2→S3transitions. This suggests that the correct stoichiometry is (0,l,0,‐1). The possibility of a non‐integer stoichiometry may also be considered.
ACUTE EFFECTS OF LOW‐FLUENCE ULTRAVIOLET LIGHT ON HUMAN T‐LYMPHOCYTE SUBSETS
Authors: Mcgrath Hugh , WILSON Wendella , Scopelitis Eve
Published: January 2008

Abstract‐The acute effects of low‐fluence ultraviolet light, primarily between wavelengths 280 and 320 nm (ultraviolet B) on T‐lymphocyte subsets were assessed in virro and in vivo by quantitative cytofluorometric analysis. In virro, 90J/m2 of ultraviolet irradiation of human mononuclear cells produced a significant increase in the OKT4 (helper‐inducer)/OKT8 (suppressor‐cytotoxic) ratio (P>0.008), due primarily to a decrease in the OKT8 subset. In vivo, 24 h after whole‐body UV irradiation of human subjects with one half of a minimal erythemal dose of ultraviolet B the OKT4/OKT8 ratios again increased (P > 0.002), again with somewhat greater effects on the OKT8 subset. These results indicate that suberythemal exposure to UV light increases OKT4/OKT8 ratios in normal human subjects because of differential effects on lymphocyte subsets. They suggest that casual exposure to sunlight mediates immunologic changes in normal human subjects.
DIRECT DETECTION OF SINGLET OXYGEN SENSITIZED BY HAEMATOPORPHYRIN AND RELATED COMPOUNDS
Authors: Keene J. P. , Kessel D. , Land E. J. , Redmond R. W. , Truscott T. G.
Published: January 2008

Abstract— Direct time‐resolved detection of the luminescence at 1270 nm from ‘singlet oxygen’ was used to estimate the quantum yield of singlet oxygen production (ΦΔ) from a series of related porphyrins in benzene and in D2O. From this and available data the fraction of oxygen quenching interactions leading to singlet oxygen production (SΔ) was derived in most cases. A marked increase in ΦΔ value was observed for di‐haematoporphyrin ester (DHE) in cetyltrimethyl ammonium bromide/D2O solution in comparison to D2O alone, this increase is attributed to a major structural alteration of DHE on introduction of the detergent.
STUDIES OF THE EFFICIENCY and MECHANISM OF FLUORESCENCE QUENCHING REACTIONS USING ACRYLAMIDE and SUCCINIMIDE AS QUENCHERS
Authors: Eftink Maurice R. , Selva Thomas J. , Wasylewski Zygmunt
Published: January 2008

Abstract Here we report data for the quenching by acrylamide and succinimide of the fluorescence of a number of simple aromatic fluorophores in aqueous solution. Acrylamide is an efficient quencher of the fluorescence of most of these aromatic fluorophores, but succinimide is less efficient for all fluorophores and shows a very crude dependence on the ionization potential of the fluorophore. When the solvent is ethanol, the quenching efficiency by acrylamide and succinimide is found to decrease for the fluorophores, indole, naphthalene, and carbazole. These studies are consistent with an electron transfer quenching mechanism for the two quenchers. Quenching parameters (by acrylamide, succinimide, and iodide) are also reported for a number of fluorescent probes commonly used in biochemical studies. In general, the efficiency of acrylamide and succinimide quenching of these probes is low in aqueous solution.
STRATEGIES FOR SELECTIVE CANCER PHOTOCHEMOTHERAPY: ANTIBODY‐TARGETED and SELECTIVE CARCINOMA CELL PHOTOLYSIS*
Authors: Oseroff A. R. , Ara G. , Ohuoha D. , Aprille J. , Bommer J. C. , Yarmush M. L. , Foley J. , Cincotta L.
Published: January 2008

Abstract A principle objective in chemotherapy is the development of modalities capable of selectively destroying malignant cells while sparing normal tissues. One new approach to selective photochemo‐therapy, antibody‐targeted photolysis (ATPL) uses photosensitizers (PS) coupled to monoclonal antibodies (MAbs) which bind to eel) surface antigens on malignant cells. Selective destruction of human T leukemia cells (HBP‐ALL) was accomplished by coupling the efficient PS chlorin e6 to an anti‐T cell MAb using dextran carriers. Conjugates with chlorin : MAb ratios of 30 : 1 retained > 85% MAb binding activity, and had a quantum yield for singlet oxygen production of 0.7 ±0.1, the same as that of free chlorin e6. Cell killing was dependent on the doses of both MAb‐PS and 630‐670 nm light, and occurred only in target cell populations which bound the MAb. On the order of 1010 singlet oxygen molecules were necessary to kill a cell.

A second approach to specific photochemotherapy, selective carcinoma cell photolysis (SCCP), relies on preferential accumulation of certain cationic PS by carcinoma cell mitochondria. We have evaluated several classes of cationic dyes, and in the case of N,N′‐bis‐(2‐ethyl‐1,3‐dioxolane)‐krypto‐cyanine (EDKC) and some of its analogs, have demonstrated highly selective killing of human squamous cell, bladder and colon carcinoma cells in vitro. In isolated mitochondria, EDKC uptake and fluorescence depended on membrane potential, and the dye specifically photosensitized damage to Complex I in the electron transport chain. N,N′‐bis‐(2‐ethyl‐1,3‐dioxolane)‐kryptocyanine and some of its analogs accumulated within subcutaneous xenografts of human tumors in nude mice with tumor : skin ratios > 8. Photoirradiation caused significant inhibition of tumor growth, without cutaneous phototoxicity.
QUANTUM EFFICIENCIES OF THE REVERSIBLE PHOTOREACTION OF OCTOPUS RHODOPSIN
Authors: Dixon Sheila F. , Cooper Alan
Published: January 2008

Abstract The classic method of photometric curves for photosensitivity determination has been extended to the case of photoreversible reactions and applied to the octopus rhodopsin → acid metarhodopsin photoreaction. In such cases, measurements at one irradiation wavelength yield the sum of the photosensitivities of the forward and reverse processes. However, by using different irradiation wavelengths, together with appropriate molar extinction coefficients, the quantum efficiencies for both reactions may be resolved. For detergent‐solubilized octopus rhodopsin at room temperature, pH 7, the quantum yields are found to be 0.69 (± 0.03) for rhodopsin → metarhodopsin, in line with values observed in a range of vertebrate visual pigments, and 0.43 (± 0.02) for the reverse photoregeneration process. The similarities in overall photosensitivities of the forward and reverse reactions in the visible region are consistent with a significant physiological role for photoreversal in the cephalopod visual cycle.
ESR DETECTION OF ENDOGENOUS ASCORBATE FREE RADICAL IN MOUSE SKIN: ENHANCEMENT OF RADICAL PRODUCTION DURING UV IRRADIATION FOLLOWING TOPICAL APPLICATION OF CHLORPROMAZINE
Authors: Buettner Garry R. , Motten Ann G. , Hall Robert D. , Chignell Colin F.
Published: January 2008

Using electron spin resonance spectroscopy, we observed that UV radiation (330 nm) increased the endogenous ascorbate free radical concentration in hairless mouse (HRS/J) skin. When the skin was topically treated with a chlorpromazine solution prior to illumination, UV irradiation caused the ascorbate free radical concentration to increase even more. This observation suggests that there is an increased UV‐induced oxidative stress in the presence of chlorpromazine, probably caused by the production of free radicals from chlorpromazine.
SINGLET OXYGEN GENERATING EFFICIENCY OF α‐TERTHIENYL and SOME OF ITS SYNTHETIC ANALOGUES*
Authors: Scaiano J. C. , MacEachern A. , Arnason J. T. , Morand P. , Weir D.
Published: January 2008

The singlet oxygen generating efficiency of several thiophenic compounds, including oc‐terthienyl (αT) and some of its synthetic analogues, has been determined using laser flash photolysis techniques. The method, which is based on the time‐resolved bleaching of 1,3‐diphenylisobenzofuran, led to relatively high efficiencies for all the substrates examined; for example the values were 0.86, 0.69 and 0.63 for αT, DBrαT and TNP, respectively in chloroform‐d at 293K. Our results also indicate that high intersystem crossing efficiencies must be a common characteristic in these compounds. The variations in singlet oxygen yields were found to be modest in comparison with changes in the biological activity of these compounds, therefore suggesting that other factors are also quite important in determining the latter.
WAVELENGTH DEPENDENCE OF THE QUANTUM YIELD FOR THE STRUCTURAL ISOMERIZATION OF BILIRUBIN
Authors: Greenberg Jordan W. , Malhotra Vinay , Ennever John F.
Published: January 2008

The quantum yield and the relative photochemical yield for lumirubin formation from bilirubin bound to human albumin were determined at eight wavelengths from 410 to 520 nm. The quantum yield averaged 0.0015 for irradiation between 450 and 490 nm. At 410 and 430 nm the quantum yield was slightly lower. At the long wavelength end of the absorption band, from 500 to 520 nm, the quantum yield averaged 0.003. The relative photochemical yield, normalized to constant fluence, was greatest at 500 nm.
INVOLVEMENT OF SINGLET OXYGEN IN THE PHOTOTOXICITY MECHANISM FOR A METABOLITE OF PIROXICAM
Authors: Western A. , Camp J. R. Van , Bensasson R. , Land E. J. , Kochevar I. E.
Published: January 2008

It has been previously shown that a metabolite of piroxicam but not piroxicam itself causes phototoxicity to cells in vitro after exposure to UVA (320–400 nm) radiation. The phototoxicity mechanism for this metabolite, 2‐methyl‐4‐oxo‐2H‐l,2‐benzothiazine‐l,l‐dioxide (Compound I), was investigated. In vitro phototoxicity to human mononuclear cells was assayed using 0.5 mM Compound I and UVA radiation. The UVA fluence required for phototoxicity of Compound I was lower by a factor of 2‐3 in D2O buffer compared to H2O buffer. Superoxide dismutase and mannitol, which remove O2‐ and OH”, respectively, do not decrease the phototoxicity. The photodecomposition of Compound I was inhibited by sodium azide, enhanced by human serum albumin and unaffected by mannitol. Stable photoproducts of Compound I were not toxic to the cells. The quantum yield of singlet oxygen based on its emission at 1270 nm was 0.19 and 0.35 for Compound I and s2 ± 10‐3 and 10‐2 for piroxicam in D2O and C6H6, respectively. While the extremely low quantum yield for singlet oxygen from piroxicam appears to account for its lack of phototoxicity, the phototoxicity mechanism for its metabolite, Compound I, most likely does involve singlet oxygen.
PHTHALOCYANINE PHOTOSENSITIZATION OF MAMMALIAN CELLS: BIOCHEMICAL and ULTRASTRUCTURAL EFFECTS
Authors: Ben‐Hur E. , Green M. , Prager A. , Kol R. , Rosenthal I.
Published: January 2008

AbstractThe incorporation of thymidine, uridine and leucine into DNA, RNA and proteins, respectively, was measured in log‐phase Chinese hamster cells photosensitized by chloroaluminum phthalo‐cyanine tetrasulfonate (A1PCS). Post‐treatment synthesis of all macromolecules was inhibited. The inhibition became progressively more pronounced with time, reaching a maximum atca.3 h after treatment. The differences between relative sensitivity of protein, RNA and DNA syntheses to A1PCS photosensitization, were not statistically significant. Some of the observed inhibition was due to a reduced uptake of the labeled precursors from the growth medium. Energy metabolism, as reflected by glucose oxidation, was sensitive to A1PCS plus light. Inhibition of glucose oxidation was evident immediately after treatment, and became more pronounced with time. Following a sublethal light fluence, maximum inhibition was observed at 3 h and there was a gradual recovery at later times. Inhibition of glucose oxidation was about two fold higher in plateau‐phase compared to log‐phase cells. The former were also twice as sensitive with respect to cell killing. These results suggest that inhibition of glucose oxidation induced by mitochondrial damage as seen in human lymphocytes, may be a primary cause for AlPCS‐photosensitized cell killing.
IN VITRO STUDIES ON THE PHOTOSENSITIZED OXIDATION OF LENS PROTEINS BY PORPHYRINS
Authors: Roberts Joan E. , Dillon James
Published: January 2008

Abstract Porphyrins, which may be introduced into the eye as a result of abnormal porphyrin metabolism (uroporphyrin–Uro) or when used in the diagnosis or photodynamic therapy of certain tumors, including intraocular tumors (hematoporphyrin–Hp and‘hematoporphyrin derivative’–Hpd and mesotetra(P‐sulfonatophenyl)porphyrin–TPPS) are efficient photosensitizers in biological systems. We have been studying the potential phototoxic side effects of these drugs in the lens of the eye. Encapsulated in the human lens is a mixture of soluble protein crystallins. With little turnover of protein in the lens, any photosensitized modifications will accumulate and may result in an opacification of the lens. To evaluate the potential of different porphyrins to induce such damage, a series of porphyrins were photolyzed (transmission above 295 nm) in the presence of calf lens protein (2 mg m−1). Marked photopolymerization and histidine destruction were observed for the lens protein photolyzed in the presence of all of the drugs. We have found that the relative effectiveness of the following porphyrins to induce that damage is: Uro = TPPS Hpd = Hp. Both the singlet oxygen quencher, azide, and the free radical scavenger, penicillamine, decrease this photosensitized oxidative damage to lens protein. TPPS binds significantly to lens protein and this binding leads to conformational changes in that protein.
THERMODYNAMICS OF PORPHYRIN BINDING TO SERUM ALBUMIN: EFFECTS OF TEMPERATURE, OF PORPHYRIN SPECIES and OF ALBUMIN‐CARRIED FATTY ACIDS
Authors: Rotenberg Michal , Cohen Smadar , Margalit Rimona
Published: January 2008

Abstract Porphyrin binding to serum albumin was studied at the molecular level probing the effects of: porphyrin self‐aggregation, porphyrin species, temperature and protein‐bound fatty acids. Human serum albumin was found to have a single high‐affinity site for porphyrin monomers, with binding constants of 2 x 106, 5 x 107 and 3 x 108 (37o C, neutral pH, M−1), for hemato‐, deutero‐ and protoporphyrins, respectively. Three equilibria models for the dimer binding were developed and tested. The data were found to fit best with a model proposing a single high‐affinity binding site for the dimer, independent of and different than the monomer site. The binding constants of the hematoporphyrin and deuteroporphyrin dimers to human serum albumin (37o C, neutral pH, M−l) being 4 x 10* and 5 x 108 respectively. The temperature dependence (Dp and HSA, 22‐37o C) of the monomer binding showed the process to be entropy‐driven (δGo= ‐45 kJ mol−1; δSo=+146 kJ mol−1; δHo= 0 kJ mol−1). For the dimer binding, the enthalpy change was found to be highly temperature‐dependent implying continuous changes in the heat capacity of the system over the entire temperature range, the trend at the 37o C region fitting an entropy‐driven process. The monomer vs dimer differences in temperature dependence strongly support separate and independent binding sites for these species. Similar thermodynamics were determined for fatty‐acid carrying as well as for fatty‐acid free HSA, with mild quantitative (but not qualitative) shifts.
A FLUORESCENCE IMAGING DEVICE FOR ENDOSCOPIC DETECTION OF EARLY STAGE CANCER – INSTRUMENTAL and EXPERIMENTAL STUDIES
Authors: Baumgartner R. , Fisslinger H. , Jocham D. , Lenz H. , Ruprecht L. , Stepp H. , Unsold E.
Published: January 2008

Abstract Visible detection of early stage cancer labelled with the fluorescing porphyrin mixture of dihematoporphyrin‐ether and dihematoporphyrin‐ester (DHE) is often limited by a high and inhomogeneously distributed level of autofluorescence. A new imaging method for reducing autofluo‐rescence is described. The method uses alternating fluorescence excitation with laser light in the violet and blue spectral ranges. Subtraction of the corresponding fluorescence images results in contrast enhancement due to an effective reduction in the autofluorescence contribution. A prototype version of a highly sensitive fluorescence imaging device including a modified krypton ion laser, an image‐intensified solid‐state TV‐camera, a digital image‐processing system, and video recording and monitoring has been developed.

Experiments performed with this fluorescence imaging system on a tumorous dog bladder showed that a dose of 0.2 mg DHE kg−1 body wt, which is far below the dose administered for photodynamic therapy (2‐5 mg kg−’body wt), is sufficient to give a high‐contrast fluorescence image. The corresponding excitation power density was about 1 W m−2. Photobleaching of DHE was observed during fluorescence detection at excitation power densities exceeding 1 kW m−2. At these high excitation levels DHE fades out nearly completely within 0.25 min.
QUANTITATIVE in vivo MEASUREMENT OF THE FLUORESCENT COMPONENTS OF PHOTOFRIN II
Authors: Schneckenburger Herbert , Feyh Jens , Gotz Alwin , Frenz Martin , Brendel Walter
Published: January 2008

AbstractPhotofrin II which contains the most efficient components of hematoporphyrin derivative with regard to photodynamic therapy of cancer, was measured fluorometrically in tumor and tumor‐free tissuesin vivoover a period up to 8 days. Using time‐resolving (nanosecond and picosecond) microscopic techniques, the fluorescence of different components was quantitated and attributed to monomelic, dimeric, and possibly aggregated porphyrin species. The long‐lasting retention of the porphyrins in live tissues was in contrast to the rapid removal from cultured cells. This might be due to monomerization or dimerization of non‐fluorescent aggregates. Tumor‐selective accumulation was found to be similar for two different (probably monomeric and dimeric) components. This indicates that the integral fluorescence of these components may also correlate with the distribution of the main photosensitizing species.
EARLY BIOCHEMICAL RESPONSES TO PHOTODYNAMIC THERAPY MONITORED BY NMR SPECTROSCOPY
Authors: Hilf Russell , Gibson Scott L. , Penney David P. , Ceckler Toni L. , BRYANT Robert G.
Published: January 2008

Abstract Studies directed at determining the biochemical events that lead to tumor cytotoxicity following photodynamic therapy, a promising new approach for treatment of neoplasia, have demonstrated that exposure of R3230AC mammary tumors to hematoporphyrin derivative or Photofrin II plus visible light caused marked impairment of mitochondrial enzymes functioning in oxidative phosphorylation and electron transport. 31P‐NMR spectroscopy has now demonstrated that a rapid and striking decrease in NTP (ATP) levels, concomitant with a marked increase in P;, occurs in tumors shortly after photodynamic therapy. These effects appear to be fluence related. Possible changes in tumor vascularity, as detected by 2H‐NMR measurements of the uptake of D20, were not observed under the conditions studied. Taken together with our earlier results, we conclude that the reduction in tumor ATP levels in situ, probably via inhibition of mitochondrial function, is a direct and early response of neoplastic tissue to porphyrin‐induced photosensitization.
PHOTODYNAMIC THERAPY OF A MURINE TUMOR FOLLOWING SENSITISATION WITH CHLORO ALUMINUM SULFONATED PHTHALOCYANINE
Authors: Chan W.‐S. , Marshall J. F. , Hart I. R.
Published: January 2008

Abstract Syngeneic mice bearing a colorectal carcinoma (Colo 26) growing subcutaneously in the flank region received photodynamic therapy (PDT) when the tumor was 7‐12 mm diameter. Light (emission at 675 nm from an argon ion pumped dye laser, laser energy 100 J, power 50 mW) was delivered to the tumor 24‐28 h after the i.v. injection of a single dose of chloro aluminum sulfonated phthalocyanine (ClAlSPc) at 5 mg kg1 body weight. Control tumor‐bearing animals received (1) phosphate buffered saline (PBS) but not PDT, (2) ClAlSPc but not PDT, or (3) PBS injection plus PDT. Five days later PDT tumors of the ClAlSPc + PDT group were markedly reduced in size (mean weight 0.075 ± 0.027 g) as compared with those from control groups 1 (0.408 ± 0.167 g), 2 (0.475 ± 0.143 g) or 3 (0.376 ± 0.153 g). Histological examination revealed that ClAlSPc + PDT induced severe necrosis and cytotoxicity of neoplastic cells with viable tumor limited to a small peripheral margin. Animals in the ClAlSPc + PDT group in a repeat experiment survived significantly longer than animals in the three control groups suggesting that ClAlSPc may be a useful photosensitiser for PDT of cancer.
CLOSURE OF EXPERIMENTAL SUBRETINAL NEOVASCULAR VESSELS WITH DIHEMATOPORPHYRIN ETHER AUGMENTED ARGON GREEN LASER PHOTOCOAGULATION
Authors: Thomas Edgar L. , Langhofer Mikayo
Published: January 2008

Abstract Natural history studies of patients with macular subretinal neovascularization as a complication of age‐related macular degeneration have shown a poor visual outcome, with 77% losing more than 4 lines of vision and 64% losing 6 lines at 24 months after presentation. The Macular Photocoagulation Study, a randomized clinical trial of selected cases of extramacular subretinal neovascularization has proven argon laser photocoagulation therapy to be effective in reducing visual loss. Unfortunately, many patients with macular subretinal neovascularization were excluded from this study because of the risk of laser damage to the surrounding retina and choroid.

We have developed a potentially more efficacious and safe treatment for experimental subretinal neovascularization in the cynomolgus monkey using a combination of dihematoporphyrin ether pre‐treatment and sub‐threshold argon green laser photocoagulation. Closure of the subretinal neovascular complex was attained with reduced destruction to the surrounding retina and choroid. Our data have potential import for improved treatment in humans of macular subretinal neovascularization which lie beneath the foveal avascular zone. This preliminary study suggests the photosensitivity of the vasculature of the subretinal neovascular complex to laser photoradiation may be increased selectively by the use of dihematoporphyrin ether.
PHOTOBLEACHING OF PHOTOFRIN II AS A MEANS OF ELIMINATING SKIN PHOTOSENSITIVITY*
Authors: Boyle D. G. , Potter W. R.
Published: January 2008

One of the effects of using Photofrin II as a sensitizer in clinical photodynamic therapy is skin photosensitivity. Avoiding the harmful effect of this photosensitivity typically requires the patient to remain indoors during daylight hours for 4 weeks post injection. Photosensitivity can last up to 8 weeks. A possible method of quickly eliminating skin photosensitivity is the use of photobleaching to eliminate the DHE (dihematoporphyrin ether, the active agent in Photofrin II) from the skin. The Photofrin II was used as supplied (Photomedica, Raritan, NJ) and will be referred to as DHE.

We report a series of experiments using Swiss mice which demonstrate the ability to reduce the period of photosensitivity to 1 week. The Swiss mice received 5 mg kg‐1 DHE intraperitoneal. Beginning at 24 h post injection they were given daily increasing light doses starting with 18 J cm‐2 (at 630 nm). Only the left hind feet were treated with light. At 7 days post injection both hind feet were treated with 135 J cm‐2. The pretreated left foot showed no reaction to this treatment whereas the right foot reacted as strongly as control mice which had received no pretreatment with light. The control mice were also injected 7 days prior to treatment.

As a check for tolerance animals received a second injection of 5 mg kg‐1 DHE intraperitoneally 96 h after the conclusion of the bleaching protocol. Twenty‐four h later the left hind foot (previously desensitized by light) reacted to 135 J cm‐2 as strongly as controls which had received the 5 mg kg‐1 of DHE but no pretreatment.
PHOTOREACTIVATION OF ULTRAVIOLET RADIATION DAMAGE IN DARK REPAIR DEFICIENT PHR MUTANTS OF Escherichia coli K‐12
Authors: Smith A. W. , Davies D. J. G. , Moss S. H.
Published: January 2008

There is uncertainty in the literature concerning the genetic control of photoreactivation in E. coli. Two genetic loci, phrA and phrB have been proposed, and two photolyase molecules have been isolated, but in vivo evidence for the activity of the former is controversial. We have studied photoreactivation after 254 nm UV in a dark‐repair‐deficient phrB mutant and in a strain deleted at the proposed phrA locus. We show apparent photoenzymatic repair in the phrB mutant, which is abolished when the mutation is transduced into the proposed phrA deletion mutant. We conclude that there is a gene in the region of the proposed phrA locus which affects photoenzymatic repair.
PHOTOSENSITIZATION OF PYRIMIDINE DIMER SPLITTING BY A COVALENTLY BOUND INDOLE
Authors: Van Camp John R. , Young Tish , Hartman Rosemarie F. , Rose Seth D.
Published: January 2008

Abstract— Photosensitized pyrimidine dimer splitting characterizes the enzymatic process of DNA repair by the DNA photolyases. Possible pathways for the enzymatic reaction include photoinduced electron transfer to or from the dimer. To study the mechanistic photochemistry of splitting by a sensitizer representative of excited state electron donors, a compound in which an indole is covalently linked to a pyrimidine dimer has been synthesized. This compound allowed the quantitative measurement of the quantum efficiency of dimer splitting to be made without uncertainties resulting from lack of extensive preassociation of the unlinked dimer and sensitizer free in solution. Irradiation of the compound with light at wavelengths absorbed only by the indolyl group (approximately 280 nm) resulted in splitting of the attached dimer. The quantum yield of splitting of the linked system dissolved in N20‐saturated aqueous solution was found to be 0.04 ± 0.01. The fluorescence typical of indoles was almost totally quenched by the attached dimer. A splitting mechanism in which an electron is efficiently transferred intramolecularly from photoexcited indole to ground state dimer has been formulated. The surprisingly low quantum yield of splitting has been attributed to inefficient splitting of the resulting dimer radical anion. Insights gained from this study have important mechanistic implications for the analogous reaction effected by the DNA photolyases.
RELATIVE REACTIVITIES OF THE EXCITED STATES OF FUROCOUMARINS FOR [2+2] PHOTOCYCLOADDITION REACTION WITH TETRAMETHYLETHYLENE
Authors: Shim Sang Chul , Kang HO Kwon
Published: January 2008

Abstract—The Stern‐Volmer constants for fluorescence quenching by tetramethylethylene decrease in the order DMC ≫ DHP > F‐2 > 8‐MOP. The same order was observed for the quantum yields of [2+2] cycloaddition reaction with tetramethylethylene on direct irradiation. In [2+2] photocycloaddition of F‐2 with tetramethylethylene in ethanol, the ratio of quantum yields deduced from singlet and triplet states of F‐2; φ30/φ10, is about 5. The excited triplet state is the reactive state for the [2+2] photocycloaddition of F‐2 with tetramethylethylene in solution but the excited singlet state of F‐2 becomes very important in biological conditions.
CHARACTERIZATION OF ANTIBODIES SPECIFIC FOR UV‐DAMAGED DNA BY ELISA
Authors: Eggset Guri , Volden Gunnar , Krokan Hans
Published: January 2008

Abstract— The specificity of affinity purified antibodies raised against UV‐irradiated DNA was examined using an enzyme‐linked immunosorbent assay. DNA irradiated with UV doses higher than needed for saturation with pyrimidine dimers bound increasing amounts of antibody. Photosensitized DNA, containing high amounts of pyrimidine dimers, showed very poor binding of antibody. When UV‐irradiated DNA was given a second dose of 340‐nm UV light, the binding of antibodies was abrogated. Taken together, this indicates a major specificity for (6‐4)‐photoproducts, which are photochemically reversed by UV light in the 340‐nm region. The antibodies also showed little but detectable binding to pyrimidine glycols produced in DNA by oxidation with OsO4. Previously, we have used these antibodies for the detection of UV‐induced DNA damage and its repair in human skin in vivo. These findings indicate that (6‐4)‐photoproducts, considered highly mutagenic, are repaired in human skin.
EFFECT OF HUMIDITY ON PHOTOINDUCED ESR SIGNAL FROM HUMAN HAIR
Authors: Jahan M. S. , Drouin T. R. , Sayre R. M.
Published: January 2008

Abstract— Human red hairs, equilibrated at 79.8%, 58.0%, 32.3% humidity and at dry conditions, were irradiated with UV‐visible (Λ > 290 nm) light. ESR intensity of the photo‐induced transient free radicals was measured, at room temperature, as a function of time during and after exposure to light. Photoenhancement was found to be most pronounced in 79.8%‐humidity conditioned hair and least in dry hair. The lifetimes of the transient free radicals in these samples were measured as 360s (79.8%), 180s (58.0%), 140s (32.3%), and 50s (dry). The gradual increase in lifetime as a function of humidity conditions was attributed to an increasing number of decay rates of the centers varying from fast to slow, the slow ones being unable to decay unless the fast ones do. This process is best described by a stretched exponential time function, I(t) =Ioexp[‐(t/to)α].
CHARACTERIZATION OF THE TRANSIENT SPECIES IN THE 266‐nm LASER PHOTOLYSIS OF ADENINE AND ITS DERIVATIVES
Authors: Arce R.
Published: January 2008

Abstract. Transient absorption spectra produced by 266‐nm ns laser flash photolysis of aqueous solutions of adenine, 2′‐deoxyadenosine, 2′‐deoxyadenosine‐5′‐phosphate, adenosine‐5′‐phosphate, 2′‐deoxyadenylyl‐(3′‐5′)‐2‐deoxyadenosine, 7‐methyladenine and 9‐methyladenine have been measured under different pH conditions. The transients observed after excitation consisted mainly of the hydrated electron, the radical cation, the radical anion and/or neutral radicals resulting from its protonation, and a minor contribution from the excited triplet state. The photoionization occurs mainly through an excited singlet state. For adenine, the cation and anion radical absorption spectra were determined using laser and pulse radiolysis techniques. The triplet state presence was established through sensitization experiments. The hydrated electron decays following a pseudo‐first‐order reaction with the neutral base.
PHOTOSENSITISING ACTIVITY OF PHTHALOCYANINE DYES SCREENED AGAINST TISSUE CULTURE CELLS
Authors: Chan W.‐S. , Marshall J. F. , Svensen R. , Phillips D. , Hart I. R.
Published: January 2008

Abstract. A series of phthalocyanine (Pc) dyes were screened for their ability to photosensitise murine embryonic fibroblasts or fibrosarcoma cells. Cells were cultured in the presence of the dyes for 24 h. following which they were irradiated with either room light or red light and cultured for a further 72‐h period. Eleven water‐insoluble Pc (including a free‐base Pc) and 6 water‐soluble sulfonated derivatives were screened in this fashion. Free base (H2), copper (Cu), copper di‐. tri‐, tetra‐sulfonated (CuS2, CuS3. CuS4), fiuoro chromium (FCr), iron (Fe), cobalt (Co), palladium tetra‐sulfonated (PdS4). nickel (Ni) and nickel tetra‐sulfonated (NiS4)Pc dyes had no cytotoxic activity in these assays under conditions of either room‐light or red‐light exposure. Magnesium (Mg), zinc (Zn) and zirconium (Zr) Pc dyes were highly toxic to cells, producing 0% survival at 72 h, following exposure to both light sources. In contrast, chloro aluminum (C1AI). chloro aluminum sulfonated (C1A1S) and dichloro tin (Cl2Sn) Pc dyes exhibited differential phototoxicity, producing total cell death following red‐light irradiation but no or little cytotoxic effect after exposure to room light, raising the possibility that these dyes might prove useful for photo‐dynamic therapy of cancer.
A REVIEW OF SOME TOPICS CONCERNING MUTAGENESIS BY ULTRAVIOLET LIGHT
Authors: Hutchinson Franklin
Published: January 2008

This paper is not a systematic review of the entire field of mutagenesis by ultraviolet light, but coverage of certain areas in which there have been significant developments in the past few years, and which are of particular interest to the author. Some general reviews still widely referred to are those by Witkin (1976), Harm (1980), and Hall and Mount (1981). In this paper, UV means 254 nm light, unless otherwise stated.
C4‐CYCLODIMERS OF PSORALEN ENGAGING THE 4′,5′‐ DOUBLE BOND
Authors: Caffieri Sergio , Dall'acqua Francesco
Published: January 2008

Abstract—By irradiating psoralen (the parent linear furocoumarin) in thin solid film two new fluorescent photodimers. compounds I and II, have been isolated and characterized. Unlike previously isolated dimers of furocoumarins which showed a ‘pyrone‐pyrone’ structure involving in the C4‐cycloaddition the 3,4‐double bond of the furocoumarinic moiety, the new dimers show respectively a ‘furan‐furan’ and a ‘furan‐pyrone’ structure, involving therefore the 4′,5′‐double bond. By analogy with the photocycloaddition reactions between furocoumarins and pyrimidine bases of DNA, in this case too the 4′,5′‐double bond of the furocoumarin can be involved. The experimental conditions, however, in which irradiation is carried out play an important role.
THREE EXPONENTIAL FLUORESCENCE DECAY OF HORSE LIVER ALCOHOL DEHYDROGENASE REVEALED BY IODIDE QUENCHING
Authors: Demmer David R. , James Douglas R. , Steer Ronald P. , Verrall Ronald E.
Published: January 2008

Abstract— The time resolved fluorescence decay of horse liver alcohol dehydrogenase was measured using a frequency doubled picosecond dye laser and time‐correlated single‐photon counting detection. A flow‐cell technique is described which eliminates the photodegradation artifacts which commonly occur with laser excitation. A procedure is introduced which uses fluorescence quenching to reveal minor fluorescence lifetime components. The decay of the unquenched tryptophanyl fluorescence could be described by a double exponential decay law, but experiments conducted in the presence of iodide ion showed that the fluorescence decay must be more complex than this. A model is presented in which the fluorescence decay consists of three exponential components, only two of which are susceptible to quenching by iodide ion. Several possibilities are presented for the origin of this minor decay component, the most reasonable of which is that it arises from conformational heterogeneity in the solvent‐exposed tryptophanyl residue.
DYNAMICS OF EXCITED FLAVOPROTEINS—PICOSECOND LASER PHOTOLYSIS STUDIES
Authors: Karen Akiya , Sawada Michiko Takagi , Tanaka Fumio , Mataga Noboru
Published: January 2008

Abstract— Molecular mechanism of fluorescence quenching of flavins in flavodoxin from Desulfovibrio vulgaris, strain Miyazaki, and riboflavin binding protein from egg white has been investigated by means of picosecond laser photolysis technique. In the case of flavodoxin, a transient absorption band characteristic of the non‐fluorescent exciplex formed by electron transfer from indole to excited flavins in model systems has been observed around 600 nm at the delay time of 33 ps from exciting ps pulse pulse width, 25 ps). In the case of riboflavin binding protein, the transient absorption spectra were different from those of flavin‐indole exciplex and rather similar to the spectra of the model system of flavin‐phenol. These results suggest that tryptophan residue exists near the isoalloxazine nucleus in flavodoxin, and in riboflavin binding protein, tyrosine residue exists near the flavin. Direct measurements of the ultrafast process of the electron transfer in flavoproteins as developed here could provide useful information for elucidating protein dynamics, associated with redox reaction, in the picosecond time region.
PHOTOCHEMICAL PROPERTIES OF FLAVIN DERIVATIVES
Authors: Fritz Bernhard J. , Kasai Sabu , Matsui Kunio
Published: January 2008

Abstract— The triplet yields of 15 derivatives of riboflavin modified either in position 8 or in the ribityl side chain have been determined. The triplet yields measured range from 0.002 to 0.9. In addition, estimates for the rate constants of the photoreaction with EDTA and for the complex formation constants with EDTA at pH 7.0 are given. Evidence for an interaction in solution of at least the 2′ and 5′ hydroxyl groups of RF with the isoalloxazine ring is presented.
PICOSECOND TIME‐RESOLVED EMISSION SPECTRA OF PHOTOINHIBITED AND PHOTOBLEACHED Anabaena variabilis
Authors: Bittersmann E. , Holzwarth A. R. , Agel G. , Nultsch W.
Published: January 2008

Abstract— Time resolved emission spectra have been measured of Anabaena variabilis cells which were grown under different light conditions. The spectra of algae photoinhibited with strong white light for 6 h as well as of algae irradiated with blue light are similar to those of the control (weak white light). Cells that were photobleached with strong white light or red light (5 days each) show dramatic changes in their time resolved emission spectra. The contributions of long‐lived components to the time resolved emission spectra are large in photobleached cells. In both the reference sample and in photoinhibited cells the short‐lived components with lifetimes in the picosecond range prevail which indicates efficient energy transfer within the antenna pigments. The results upon photobleaching are discussed in terms of a functional decoupling of the phycobilisome rods from the core while photoinhibition does not influence the pigment composition and the molecular organization of the antenna pigments.
BASE‐SPECIFIC DAMAGE INDUCED BY 4‐THIOURIDINE PHOTOSENSITIZATION WITH 334‐nm RADIATION IN M13 PHAGE DNA
Authors: Ito A. , Robb F. T. , Peak J. G. , Peak M. J.
Published: January 2008

Abstract— Site‐specific DNA damage caused by 334‐nm radiation in the presence of the rare Escherichia coli base 4‐thiouridine was investigated in vitro by detecting the sites of the termination of DNA synthesis with irradiated M13 phage DNA used as a template. Single‐strand breakage was also examined. The results indicate that 334‐nm radiation at very low fluences in the presence of 4‐thiouridine induces termination of strand synthesis at thymine base sites and at the base immediately prior to thymine. Termination at these sites was diminished by treatment with hot piperidine. Strand cleavage by piperidine treatments was observed preferentially at the guanine site, but only after irradiation at much larger fluences. It is hypothesized that at low fluences 4‐thiouridine forms photoadducts with thymine that block DNA synthesis, while at high fluences the guanine site is damaged via oxygen species.
CHLOROPHYLL PHOTOSENSITIZED ELECTRON TRANSFER IN PHOSPHOLIPID VESICLE SYSTEMS: COMPARISON OF INSIDE‐OUTSIDE ASYMMETRY BETWEEN LARGE AND SMALL UNILAMELLAR VESICLES*
Authors: Rong Shouyu , Tollin Gordon
Published: January 2008

Abstract— We have determined the chlorophyll triplet quenching efficiencies, the chlorophyll cation radical yields and the conversion efficiencies of chlorophyll triplet to radical in large and small unilamellar phosphatidylcholine vesicles (LUV and SUV, respectively) in the presence of electrically‐charged electron acceptors (ferricyanide and oxidized cytochrome c) located in either the inner or outer aqueous compartments of the vesicles. Both types of vesicles displayed inside‐outside asymmetry, although the properties were reversed. Triplet quenching in SUV was more efficient when ferricyanide was located within the vesicle interior, whereas the reverse was true in LUV. When ferricyanide was located on the outside of the vesicles, the extent of triplet quenching in LUV was about two times that in SUV and the amount of cation radical formed in LUV was about two times that in SUV. Under these conditions, the conversion efficiencies of chlorophyll triplet to radical were 12.2% for LUV and 8.5% for SUV. With cytochrome c as an electron acceptor in negatively charged vesicles (25 mol per cent dixhexadecylphosphate incorporated) similar results were obtained. Again, the triplet quenching and radical yield inside‐outside asymmetry properties were reversed between the two types of vesicles, and radical formation efficiencies when cyt c was located outside the vesicles were higher in LUV (11.7%) than in SUV (4.2%). We conclude that the inside‐outside asymmetric photochemical behavior of unilamellar phosphatidylcholine vesicles is influenced by factors in addition to the difference in radius of curvature between the inside and outside surfaces. It is suggested that transmembrane electrostatic potentials may be involved. Furthermore, in the present system the properties of LUV were more favorable to photochemical electron transfer product formation than those of SUV.
FOURIER TRANSFORM INFRARED SPECTROELECTROCHEMISTRY OF THE BACTERIOCHLOROPHYLL a ANION RADICAL
Authors: MÁNTELE W. , WOLLENWEBER A. , Rashwan F. , Heinze J. , Nabedryk E. , Berger G. , Breton J.
Published: January 2008

Abstract— Fourier transform infrared (FTIR) difference spectroscopy of the electrochemically generated anion radical of bacteriochlorophyll a was used to follow the molecular changes upon one‐electron reduction. An IR spectroelectrochemical cell was constructed, allowing in situ electrolysis in connection with spectroscopic investigations from 200 to 10 000 nm. FTIR difference spectra of the BChl a anion formation in THF d8 at U=+0.9 V (as determined by ferrocene calibration) were obtained. After complete formation of the radical, the reverse process was followed. Comparison of visible and IR spectra of the reduction and re‐oxidation processes indicates that more than 90% of the BChl a anion could be formed with 90% of it being reversible. The main IR absorbance changes are observed for the conjugated and even for the non‐conjugated C=O groups of BChl a. These results demonstrate the use of the combination of FTIR spectroscopy and electrochemistry for the characterization of radicals of the isolated pigments and of their in vivo bonding to the protein environment.