bluuebunny/crossref_metadata_2025 huggingface dataset:
8‐Methoxypsoralen and Ultraviolet A Radiation Activate the Human Elastin Promoter in Transgenic Mice: In vivo and in vitro Evidence for Gene Induction
Authors: Bernstein Eric F. , Gasparro Francis P. , Brown Douglas B. , Takeuchi Tsunemichi , Kong Sung K. , Uitto Jouni
Published: January 2008

Treatment of skin diseases with the combination of 8‐methoxypsoralen and ultraviolet A radiation (PUVA) results in clinical alterations in treated skin that resemble those observed in chronically photodamaged skin. The PUVA‐treated patients develop nonmelanoma skin cancers, pigmentary alterations and wrinkling characteristic of sun‐induced changes. The major alteration in the dermis of sun‐damaged skin is the deposition of abnormal elastic fibers, termed solar elastosis. Up‐regulation of elastin promoter activity in dermal fibroblasts explains the excess elastic tissue but not the reason for the aberrant morphology of the elastotic material. In order to study photoaging in an experimental system, we utilized a transgenic mouse line that expresses the human elastin promoter/chloramphenicol acetyltransferase construct in a tissue‐specific and developmentally regulated manner. Although UVB radiation has been demonstrated to increase promoter activity in vitro, UVA fails to demonstrate a similar effect at the doses utilized. In this study, we demonstrate the ability of PUVA treatment to up‐re‐gulate elastin promoter activity both in vitro and in vivo. These data help to explain the development of photoaging in sun‐protected PUVA‐treated skin. We attribute the up‐regulation of elastin promoter activity in response to PUVA to the formation of DNA photoadducts, which do not occur in response to UVA radiation alone.
Effect of Photosensitizer Delivery System and Irradiation Parameters on the Efficiency of Photodynamic Therapy of B16 Pigmented Melanoma in Mice
Authors: Biolo Roberta , Jori Giulio , Soncin Marina , Rihter Boris , Kenney Malcolm E. , Rodgers Michael A. J.
Published: January 2008

Abstract— Previous studies (Biolo et al., Photochem. Photobiol. 59, 362‐365, 1994) showed that liposome‐delivered Si(IV)‐na‐phthalocyanine (SiNc) photosensitizes B16 pigmented melanoma subcutaneously transplanted in C57 mice to the action of 776 nm light. However, the efficacy of the phototreatment was limited by a lack of selectivity of tumor targeting by SiNc as well as by incomplete necrosis of the neoplastic mass. The present investigations show that the use of a different delivery system (Cremophor emulsion vs liposomes of dipalmitoylphosphatidylcholine) causes no significant increase in the selectivity of tumor targeting for three injected doses of SiNc (0.5, 1, 2 mg/kg). However, upon 776 nm light irradiation (300 mW/cm2; 520 J/cm2), the delay in the rate of tumor growth was maximal (7‐8 days) for the highest naphthalocyanine dose. On the other hand, a remarkable improvement in the tumor response was obtained by inducing an intratumoral temperature increase to 44°C immediately after PDT. The thermal effect appeared to be due to photoexcitation of melanin by 776 nm light (550 mW/cm2; 520 J/cm2) and subsequent partial conversion of absorbed energy into heat.
Transformation of the Photoacoustic Signal after Treatment of Barley Leaves with Methylviologen or High Temperatures
Authors: Bukhov Nikolai G. , Boucher Nathalie , Carpentier Robert
Published: January 2008

Abstract— The photoacoustic (PA) signal at the modulation frequency of 35 Hz was studied in MV‐treated barley leaves or leaves preheated at different temperatures. Saturating illumination enhanced the magnitude of the PA signal in MV‐treated leaves in contrast with the opposite result usually found in untreated intact leaves where saturating illumination abolishes the photobaric component of the PA signal due to oxygen evolution and thus decreases the total PA signal. A linear relationship was found between the changes induced by continuous background light in the negative response of PA signal to saturating light in intact leaves and in the positive response in MV‐treated leaves. A linear relationship was also observed in MV‐treated leaves between the positive changes in the PA signal and the changes in the rate of electron transport through photosystem II (PSII) calculated from chlorophyll fluorescence data. The conclusion was drawn that only the thermal component contributes to the PA signal measured at low modulated frequency in MV‐treated leaves because the enhanced O2 uptake provides a zero net oxygen exchange by superimposing with O2 evolution. The leaves preheated at temperatures above 43°C demonstrated the positive response of the PA signal to saturating light at 35 Hz. In leaves preheated at 41.5°C, the first and second saturating pulses induced the enhancement of PA signal, whereas other pulses decreased the PA signal due to onset of oxygen evolution. The energy storage activity measured in the absence of oxygen evolution in heat‐treated leaves is proposed to be associated with cyclic electron transport activities around PSII and PSI.
Modulation of 8‐Methoxypsoralen‐Photoinduced Cutaneous Inflammatory Reactions by Various Chemotherapeutic Agents in vivo
Authors: Kumar Janak R. , Haberman Herbert F. , Ranadive Narendranath S.
Published: January 2008

Abstract— Exposure of albino rabbits to UVA‐VIS (320‐700 nm) radiation after the topical application of 8‐methoxypsor‐alen (8‐MOP) cream is associated with acute cutaneous inflammatory reactions in situ. In the present studies the effects of various agents on 8‐MOP plus light induced cutaneous inflammatory response viz. increase in vascular permeability (iVP), accumulation of polymorphonuclear leukocytes (aPMN) and erythema formation were investigated. The inflammatory reactions were induced by a single exposure of 8‐MOP‐sensitized sites to UVA‐VIS (9.4J/cm2) light. Indomethacin, p‐bromophenacyl bromide (BPAB), MK886 (trade name of Merck Sharpe & Dome), ibuprofen (IB), nordihydroguaiaretic acid (NDGA) or quinacrine were applied topically in cream base at various times prior to 8‐MOP application. The iVP and aPMN were quantitated 24 h postirradiation using 12SI‐HSA and 51Cr‐labeled PMN respectively, while erythema was graded visually. The rate of iVP, aPMN and erythema was inhibited almost completely by indomethacin (7.5‐10%) when applied twice, 18 h and 3 h prior to 8‐MOP. At lower concentrations of indomethacin (5%) iVP was inhibited whereas aPMN was augmented. The BPAB (0.25%) inhibited more than 90% of 8‐MOP‐photoinduced iVP and aPMN while there was partial reduction in erythema. The MK886 (0.1%) cream inhibited about 50% of iVP and aPMN but erythema persisted. The agents that are somewhat nonspecific such as IB, quinacrine and NDGA inhibited 8‐MOP‐photoinduced inflammation only marginally at the concentrations tested. The fact that iVP, aPMN and erythema can be dissociated suggests that there are independent variables in 8‐MOP‐photoinduced reactions, which involve multifactorial mechanisms probably controlled by different cell‐signalling pathways and mediators.
Hydrogen Atoms Are Produced When Tryptophan within a Protein Is Irradiated with Ultraviolet Light
Authors: Angiolillo Paul J. , Vanderkooi Jane M.
Published: January 2008

Abstract— The UV photolysis of the aromatic amino acid, tryptophan (Trp), in the Ca2+‐binding protein, cod paralbumin, type III, was studied using electron paramagnetic resonance (EPR) spectroscopy in the temperature range 4–80 K. For the Ca2+‐bound protein, irradiation with UV light (250–400 nm) resulted in the generation of atomic hydrogen with a hyperfine splitting of 50.9 mT, whereas in the Ca2+‐free form, where the Trp is exposed to solvent, the trapped atomic hydrogen was not in evidence. In the same spectra, the radical signal in the g = 2.00 region could be detected. The line shape of the Ca2+‐bound form is similar to the EPR line shape obtained for Trp in micellar systems. In contrast, the EPR line shape for the Ca2+‐free form is essentially featureless up to 80 K. The EPR spectra of the photoproducts of Trp and the nature of the photoreactions are therefore sensitive to the environment of Trp within the protein.
Damage to UV‐Sensitive Cells by Short UV in Photographic Flashes
Authors: Menezes S. , Monteiro C.
Published: January 2008

Abstract— Light emitted by electronic photographic flash units is shown to damage bacteria and human skin fibroblasts deficient in repair systems, with survival curves very similar to those produced by 254 nm short UV. The lesions induced by these flashes are as photorepairable by the photolyase enzyme as those induced by 254 nm UV and result in equivalent survival rates. Biological dosimetry performed with microorganisms highly sensitive to UV (Escherichia coli K12 AB2480, deficient in excision and recombinational‐dependent repair systems and Bacillus subtilis UVSSP spores, deficient in excision and in a specific spore repair process) revealed that each 1 ms flash of light from the photographic unit used in this work contained the equivalent of 0.25 J m−2 of 254 nm UV, when measured at a distance of 7.0 cm. This dose of UV was found to be lethal to both repair‐deficient E. coli bacteria and repair‐deficient human skin fibroblasts obtained from xeroderma pigmentosum donors, as well as mutagenic in B/r wild‐type and HCR‐mutant bacteria.
The Lack of Efficacy of 4,6,4′‐Trimethylangelicin to Induce Immune Suppression in an Animal Model for Photopheresis: a Comparison with 8‐MOP
Authors: Van Iperen H. P. , Brun B. M. , Caffieri S. , Dall'Acqua F. , Gasparro F. P. , Van Henegouwen G. M. J. Beijersbergen
Published: January 2008

Photopheresis is an extracorporeal form of photochemo‐therapy with 8‐methoxypsoralen (8‐MOP) and UVA (PUVA). Patients ingest 8‐MOP and then a psoralen‐rich buffy coat is obtained by centrifugation and mixed with saline. This mixture is recirculated through a UVA radiation field and then reinfused. Photopheresis appears to be effective for several T cell‐mediated disorders, because the treatment results in a specific immune response against the pathogenic clone of T cells involved. With PUVA therapy, the whole body of the patient is exposed to UVA, after ingestion of 8‐MOP. Upon UVA exposure 8‐MOP binds to, amongst others, DNA and induces DNA monoadducts and interstrand cross‐links. As a result of these photoadducts photocarcinogenicity is a risk in PUVA. In PUVA for psoriasis, it proved that angular furocoumarins, although almost incapable of inducing DNA cross‐links (less carcinogenic), are still effective. In order to determine if monoadducts induced by photopheresis could also be effective we used, specifically, 4,6,4′‐trimethylangelicin (TMA). In this report, we compare the photodegradation of both TMA and 8‐MOP under conditions relevant to the in vivo situation, as well as the effect both compounds have on the viability of rat lymphocytes as measured with the 3–(4,5‐dimethylthia‐zol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assay. We show that TMA did not induce immunosuppression in vivo, even after extensive irradiation. In addition a dose dependency of 8‐MOPNVA versus the induced immune suppression was carried out. It was shown that there is a log doselresponse correlation of r = 0.9205.
Photorepair of Ultraviolet Radiation (UVR)‐lnduced Pyrimidine Dimers in Lens Epithelial DNA of Monodelphis domestica
Authors: Tafoya Gregory B. , Gale James M. , Ley Ronald D.
Published: January 2008

Abstract— The repair of UV radiation‐induced pyrimidine dimers has been measured in lens epithelial DNA of the marsupial Monodelphis domestica using a pyrimidine dimerspecific endonuclease from Micrococcus luteus. Approximately 40% of the initially induced dimers were repaired during 90 min exposures to photoreactivating light. This capacity of the lens epithelium to photorepair pyrimidine dimers may provide a means with which to determine whether pyrimidine dimers in lens epithelial DNA are involved in UV radiation‐induced pathologic changes of the lens.
Dramatic Effect of Magnetite Particles on the Dynamics of Photogenerated Free Radicals
Authors: Scaiano J. C. , Monahan Sarah , Renaud Jocelyn
Published: January 2008

Abstract— Polymeric particles of about 1 u.m in diameter and containing around 40% magnetite have a dramatic influence on the dynamics of triplet radical pair reactions occurring in micelles in their vicinity. The effect has been monitored with laser flash photolysis techniques and results in a decrease of the number of radicals that separate from their geminate partner and an acceleration of radical pair geminate reactions. The effect involves remote interactions because the solution contains ca 1011micelles for each polymeric particle. Magnetite also perturbs the way in which the radicals interact with an external magnetic field.
Bacterial Cadmium Sulfide Semiconductor Particles: An Assessment of their Photoactivity by EPR Spectroscopy
Authors: Holmes Justin D. , Farrar Jacqueline A. , Richardson David J. , Russell David A. , Sodeau John R.
Published: January 2008

Abstract— The bacterium Klebsiella aerogenes produces extracellular particles of cadmium sulfide in the presence of cadmium ions. The photoactivity of these particles has been studied using electron paramagnetic resonance (EPR) spectroscopy. Bacterial samples containing these semiconductor particles were irradiated with visible light in the presence of a spin trap, either phenyl‐tert‐butylnitrone (PBN) or 5,5‐dimethyl‐l‐pyrroline‐N‐oxid(eD MPO). The results obtained reveal that a number of radicals, both oxygen and carbon based, are generated. Bacterial samples grown in the absence of cadmium ions exhibit weak, irradiation‐independent EPR signals. These bacterially produced radicals are quenched when CdS particles are present. The observation of light‐induced radicals provides evidence that the bacterial CdS particles are photoactive, behaving in a similar manner to inorganic CdS particles, and therefore could be used to mediate photocatalytic reactions.
EPR and Spectrophotometric Studies of Free Radicals (O2°−, °OH, BPD‐MA°−) and Singlet Oxygen (1O2) Generated by Irradiation of Benzoporphyrin Derivative Monoacid Ring A
Authors: Hadjur Christophe , Wagnieres Georges , Monnier Philippe , van den Bergh Hubert
Published: January 2008

Abstract— Benzoporphyrin derivative monoacid ring A (BPD‐MA), a chlorin‐type molecule, is a new photosensitizer currently in phase II clinical trials for the treatment by pho‐todynamic therapy of cancerous lesions, psoriasis and pathologic neovascularization. The photochemistry (type I and/or II) of BPD‐MA has been studied in homogeneous solution and in aqueous dispersions of unilamellar liposomes of dipalmitoylphosphatidylcholine (DPPC) using electron paramagnetic resonance and spectrophotometric methods. When oxygen‐saturated solutions of BPD‐MA were illuminated with 690 nm light, singlet oxygen (1O2), superoxide anion radical (O2−), hydroxyl radical (OH) and hydrogen peroxide (H2O2) were formed. The BPD‐MA generates 1O2 with a quantum yield of ca 0.81 in ethanolic solution. The quantum yield does not change upon incorporation of BPD‐MA into liposomes of DPPC. The superoxide anion radical was generated by the BPD‐MA anion radical (BPD‐MA−) via electron transfer to oxygen, and this process was significantly enhanced by the presence of electron donors. The rate of production of 02 was also dependent on the concentration of BPD‐MA used (3‐100 μM). The quantum yield of O2−was found to be 0.011 and 0.025 in aqueous solution and DPPC liposomes, respectively. Moreover, O2_upon dis‐proportionation can generate H2O2 and ultimately the highly reactive OH via the Fenton reaction. In anaerobic homogeneous solution, BPD‐MA−was predominantly photoproduced via the self‐electron transfer between the excited‐ and ground‐state species. The presence of an electron donor significantly promotes the reduced form of BPD‐MA. These findings suggest that the photodynamic action of BPD‐MA may proceed via both type I and type II mechanisms.
Singlet Oxygen‐Mediated Inactivation of Acetylcholinesterase: A Comparison of Purified Enzyme in Solution and Enzyme Bound to K562 Leukemia Cells
Authors: Deadwyler Gail , Sima Paul D. , Fu Yingxian , Kanofsky Jeffrey R.
Published: January 2008

Abstract— We have compared the singlet oxygen‐mediated inactivation of acetylcholinesterase (ACE) in solution with the inactivation of ACE on the surface of K562 leukemia cells. In solution, the actions of the singlet‐oxygen quenchers, methionine, azide, disodium [N,N'‐ethylene‐bis(5‐sulfosalicylideneinuninato)]nickelate(II) (Ni‐chelate 1) and disodium [(N,N'‐2,3‐propionic acid)bis(5‐sulfosal‐icylideneimminato)]nickelate(II) (Ni‐chelate 2) could be explained quantitatively by assuming their only mechanism of action was to quench singlet oxygen. The singlet oxygen quenchers, azide, Ni‐chelate 1 and Ni‐chelate 2, caused smaller inhibitions in the rate of singlet oxygenmediated inactivation of ACE on K562 cells than ACE in solution. The effects of these quenchers and of deuterium oxide were interpreted using a mathematical model of singlet‐oxygen quenching and diffusion to estimate the lifetime of singlet oxygen near the cell surface. The azide quenching data and the deuterium‐oxide data gave lifetimes of 0.9 ± 0.2 μs and 0.45 ± 0.15 μs, respectively. The increases in ACE inactivation lifetime caused by the nickel chelates were anomalously large. The unexpectedly large quenching due to the nickel chelates may have been due to a nonuniform distribution of the chelates in the cytoplasm with a large concentration of the chelate near the cell membrane.
Energy Transfer Spectroscopy for Measuring Mitochondrial Metabolism in Living Cells
Authors: Schneckenburger Herbert , Gschwend Michael H. , Strauss Wolfgang S. L. , Sailer Reinhard , Kron Martina , Steeb Ulrike , Steiner Rudolf
Published: January 2008

Abstract— Microscopic energy transfer spectroscopy was established using mixed solutions of reduced nicotinamide adenine dinucleotide (NADH) and the mitochondrial marker rhodamine 123 (R123). This method was applied to probe mitochondrial malfunction of cultivated endothelial cells from calf aorta incubated with various inhibitors of specific enzyme complexes of the respiratory chain. Autofluorescence of the coenzyme NADH as well as energy transfer efficacy from excited NADH molecules (energy donor) to R123 (energy acceptor) were measured by time‐gated fluorescence spectroscopy. Because intermo‐Iecular distances in the nanometer range are required for radiationless energy transfer, this method is suitable to probe selectively mitochondrial NADH. Autofluorescence of endothelial cells usually exhibited a weak increase after specific inhibition of enzyme complexes of the respiratory chain. In contrast, pronounced and statistically significant changes of energy transfer efficacy were observed after inhibition of the same enzyme complexes. Detection of NADH and R123 in different nanosecond time gates following the exciting laser pulses enhances the selectivity and improves quantification of fluorescence measurements. Therefore, time‐gated energy transfer spectroscopy is suggested to be an appropriate tool for probing mitochondrial malfunction.
A Preparative Method for Crosslinking Proteins to DNA in Nuclei by Single‐pulse UV Laser Irradiation
Authors: Mutskov Vesco , Angelov Dimitar , Pashev Lliya
Published: January 2008

Abstract— Photocrosslinking of proteins to DNA by single‐pulse UV laser has been used only in analytical experiments, carried out with reconstituted complexes of a single DNA binding protein and a labeled target sequence. Here we propose a large‐scale technique for irradiation of nuclei, generating preparative quantities of covalently linked protein‐DNA complexes for further analysis of the partner molecules. The use of a flow cuvette allows a milligram of DNA in either nuclei or chromatin to be irradiated by a single pulse within few minutes. The efficiency of crosslinking varies from 6 to 12% of the total nuclear proteins. The presence of histones and other chromosomal proteins in the crosslinked protein‐DNA complexes was demonstrated by using specific antibodies. The irradiation procedure can be fully automated using a microcomputer.
In Situ Action Spectra Suggest that DNA Damage is Involved in Ultraviolet Radiation‐induced Immunosuppression in Humans
Authors: Hurks H. Monique H. , Out‐Luiting Coby , Vermeer Bert‐Jan , Claas Frans H. J. , Mommaas A. Mieke
Published: January 2008

Abstract— The mixed epidermal cell lymphocyte reaction (MECLR) is a commonly used method to study the immunomodulatory effects of UV radiation. The in vitro action spectrum for the MECLR showed that the UV‐induced suppression of the MECLR responses is associated with UV‐induced DNA damage. To investigate whether in vivo DNA damage also leads to the abrogation of the MECLR, in situ action spectra were made for the MECLR and the induction of thymine dimers (T<>T). Human skin, obtained from plastic surgery, was exposed to monochromatic light of 254, 297, 302 and 312 nm. After irradiation, epidermal cells were isolated and used as stimulator cells in the MECLR or processed for flow cytometric detection of T<>T. On the basis of dose‐response curves for each wavelength, the action spectra for suppression of the MECLR and the induction of T<>T were calculated. These spectra showed close similarities, suggesting that, also in situ, UV‐induced DNA damage is involved in the UV‐induced suppression of the MECLR. Both action spectra showed a small decline from 254 nm to 302 nm, followed by a steep decline to 312 nm. These data show that, in situ, UVC can efficiently induce DNA damage and modulate cutaneous immune responses.
Rapid Tyrosine Phosphorylation of HS1 in the Response of Mouse Lymphoma L5178Y‐R Cells to Photodynamic Treatment Sensitized by the Phthalocyanine Pc 4
Authors: Xue Liang‐yan , He Jin , Oleinick Nancy L.
Published: January 2008

Abstract— The ability of photodynamic treatment (PDT) with the phthalocyanine Pc 4 to activate cellular signal transduction pathways in murine lymphoma L5178Y‐R cells has been assessed by observing increases in protein tyrosine phosphorylation at early times post‐PDT. Western blot analysis with an anti‐phosphotyrosine antibody revealed a dramatic increase in phosphorylation of two major protein bands of Mr ‐80000 and ‐55000 in response to PDT. The increase was PDT dose‐dependent, occurred as early as 20 s after initiation of light exposure of Pc 4‐pre‐loaded cells and was amplified by the presence of the protein tyrosine phosphatase inhibitor, sodium ortho‐vanadate (NaV04). By immunoprecipitation, one of the Mr –80000 phosphorylated proteins has been identified as HS1, a substrate of nonreceptor‐type protein tyrosine kinases. Although vanadate greatly enhanced the level and extent of PDT‐induced phosphorylation, it had no influence on overall photocytotoxicity or on the rate of apoptotic DNA fragmentation. Genistein, an inhibitor of protein tyrosine kinases, diminished tyrosine phosphorylation of the Mr –80000 and other proteins and dramatically potentiated cell killing induced by PDT but did not significantly affect PDT‐induced apoptosis. The results suggest that PDT rapidly activates a membrane‐associated src family kinase(s) in L5178Y‐R cells, one substrate of which is HS1, and that protein tyrosine phosphorylation is part of a stress response, protecting a portion of the cells from the lethal effects of PDT but not altering the mechanism by which they die.
Synthesis of a New Cationic Pyropheophorbide Derivative and Studies of its Aggregation Process in Aqueous Solution
Authors: Fabiano Anne‐Sylvie , Allouche David , Sanejouand Yves‐Henri , Paillous Nicole
Published: January 2008

Abstract— A new water‐soluble cationic pyropheophorbide was prepared from pyropheophorbide a by a Curtius rearrangement. The self‐aggregation process of this chlorhydrate of aminopyropheophorbide was investigated from the changes observed in its spectroscopic properties when passing from ethanol to aqueous solutions. The formation of aggregates was characterized in the absorption spectrum by a broadening of the Qy band, which is slightly shifted to the red, a significant increase in signals of circular dichroism and a drastic quenching of the fluorescence intensity at 674 nm. Analysis of the nonlinear variation of the fluorescence intensity with the dye concentration in Tris‐buffered solutions shows that dimerization is the dominant aggregation process. The dimerization equilibrium constant(at 25AoC, pH 7.5 in 5 mM Tris buffer, 10 mM NaCl) was determined to be 3.106M‐l. NMR measurements performed in DMSO at various dye concentrations showed that only the chemical shifts of some atoms are affected by these changes, indicating the part of the ring involved in the overlap of the two molecules in the dimer.A molecular modeling study of the packing arrangement of the aminopyropheophorbide molecules in aggregates performed by both semi‐empirical quantum chemical PM3 and force field MM2 methods provided a structure consistent with these spectroscopic data.
Intraperitoneal Photodynamic Therapy: Comparison of Red and Green Light Distribution and Toxicity
Authors: Veenhuizen Ruth B. , Ruevekamp Marjan C. , Oppelaar Hugo , Ransdorp Brigitte , van de Vijver Mark , Helmerhorst Theo J. M. , Kenemans Peter , Stewart Fiona A.
Published: January 2008

Abstract— The aim of this study was to compare red (652 nm) and green (514 nm) light for photodynamic therapy (PDT) of the peritoneal cavity with emphasis on light distribution and toxicity. Red‐light PDT was limited by intestinal toxicity and it was hypothesized that less penetrating green light would allow higher light doses to be used in the peritoneal cavity. Female non‐tumor‐bearing rats were photosensitized with mTHPC (meta‐tetrahydroxyphenylchlorin, Foscan®) intravenously or intraperitoneally and the peritoneum was illuminated using a minimally invasive technique. For both red and green light, the time of illumination was varied to give the required dose. Light fluence rate was measured in situ at multiple sites within the abdominal cavity. The toxicity experiments were carried out with a total of 160 J incident red or 640 J incident green light and a drug dose of 0.15 mg/kg Foscan® For red light a mean fluence rate of 55.2 38.5 mW cm 2 was measured, with a peak fluence rate of 128 mW cm 2 on the intestines. For green light the mean and peak fluence rates were 8.2 9.0 (i.e. including zero fluence rate measurements) and 28 mW cm 2, respectively. Intestines were most vulnerable to red light illumination. The intravenous injection route resulted in increased toxicity for red light, but for green light there were no major differences between intravenous and intraperitoneal routes. The 4 h interval between drug and illumination resulted in very little toxicity for both wavelengths. We conclude that for intraperitoneal PDT green light allows higher light doses than red light, but the light distribution over the peritoneum is much less favorable and may not be suitable for whole peritoneal illumination using a minimal‐access technique.
A Sequence‐specific Alkali‐labile Photolesion Mapping to Adenine in Single‐stranded DNA
Authors: Bowden Gemma M. , Davies R. Jeremy H.
Published: January 2008

Abstract— Following UV irradiation at 254 nm and treatment with hot piperidine, single‐stranded 49‐mer and 12‐mer oligodeoxyribonucleotides have been shown by gel‐sequencing experiments to contain a prominent alkali‐labile cleavage site that maps to adenine in the sequence element 5′‐TTGATC‐3′. This behavior is abolished by single base substitutions within the photoreactive tract and does not occur with duplex DNA. The distinctive properties of the photolesion are consistent with the formation of an abasic site through initial loss of a photomodified adenine base of unknown structure. The presence of an abasic site is supported by the observations that the alkaline cleavage fragments are terminally phosphorylated and that strand scission can also be effected by spermidine and the tripeptide Lys‐Trp‐Lys.
Light Emission Resulting from Hydroxylamine‐Induced Singlet Oxygen Formation of Oxidizing LDL Particles
Authors: Liu Yang , Stolze Klaus , Dadak Agnes , Nohl Hans
Published: January 2008

Abstract— Oxidation of low‐density lipoprotein (LDL) by low amounts of cupric ions resulted in the formation of singlet oxygen (1O2, 1DLg) when hydroxylamine (NH2OH) was added. Direct evidence on this excited species came from partial spectral resolution of the emitted light in the red spectral region (634 nm and 703 nm), which can be attributed to the dimol decay of singlet oxygen. Additional evidence for the existence of singlet oxygen came from the enhancing effect of deuterium oxide buffer (D20) on chemiluminescence intensity and the quenching effect of sodium azide. A linear correlation between NH2OH‐de‐pendent chemiluminescence intensity and the amount of diene conjugates (DC) formed in this reaction was observed. Removal of adventitious transition metals by adequate chelators prevented chemiluminescence in this system; NH2OH was also found to efficiently decrease metabolites of lipid peroxidation (LPO). Our findings are consistent with a sequence of reactions in which NH2OH first converts transition metals to their reduced state, thereby stimulating the formation of alkoxy‐ and peroxy‐radicals. Peroxyradicals decompose in a bimolecular Russel reaction to hydroxyl compounds and singlet oxygen while the majority of alkoxy radicals are eliminated by a secondary reaction with NH2OH. Identical effects were observed when reducing antioxidants such as ascorbic acid or trolox C were used instead of hydroxylamine.
The Effects of Thrombocytopenia on Vessel Stasis and Macromolecular Leakage after Photodynamic Therapy Using Photofrin
Authors: Fingar Victor H. , Wieman T. Jeffery , Haydon Pamela S.
Published: January 2008

Abstract— Several studies have reported thrombus formation and/or the release of specific vasoactive eicosanoids, suggesting that platelet activation or damage after photodynamic therapy (PDT) may contribute to blood flow stasis. The role of circulating platelets on blood flow stasis and vascular leakage of macromolecules during and after PDT was assessed in an intravital animal model. Sprague‐Daw‐ley rats bearing chondrosarcoma on the right hind limb were injected intravenously (i.v.) with 25 mg/kg Photofrin 24 h before light treatment of 135 J/cm2 at 630 nm. Thrombocytopenia was induced in animals by administration of 3.75 mg/kg of rabbit anti‐rat platelet antibody i.v. 30 min before the initiation of the light treatment. This regimen reduced circulating platelet levels from 300000/mm3 to 20000/mm3. Reductions in the luminal diameter of the microvasculature in normal muscle and tumor were observed in control animals given Photofrin and light. Venule leakage of macromolecules was noted shortly after the start of light treatment and continued throughout the period of observation. Animals made thrombocytopenic showed none of these changes after PDT in either normal tissues or tumor. The lack of vessel response correlated with the absence of thromboxane release in blood during PDT. These data suggest that platelets and eicosanoid release are necessary for vessel constriction and blood flow stasis after PDT using Photofrin.
An Insertion or Deletion in the Extramembrane Loop Connecting Helices E and F of Archaerhodopsin‐1 Affects in vitro Refolding and Slows the Photocycle
Authors: Sugiyama Yasuo , Koyanagi Takayuki , Yamada Naohisa , Mukohata Yasuo
Published: January 2008

Abstract— Upon addition of retinal, archaeopsin‐1 expressed in Escherichia coli (ecaO‐1002) regenerated the chromophore in dimyristoyl phosphatidylcholine (DMPC), 3‐[(3‐cholamidopropyl) dimethylammonio]‐l‐propanesulfonate (CHAPS) and sodium dodecyl sulfate(SDS) mixed micelles as efficiently as the same opsin prepared from halobacteria. Introduction of an insertion or a deletion of five amino acids into the surface loop connecting helices E and F changed the secondary and tertiary structures of ecaO‐1002 in SDS, and diminished regeneration of the chromophore. The effect of the insertion and deletion on the in vitro refolding was specific to archaeopsin because the same insertion introduced at the corresponding position of bacterioopsin (bO) did not affect chromophore regeneration. The photocycle of the regenerated ecaR‐1002 decreased in DMPC/CHAPS/SDS mixed micelles compared with that of aR‐1 in the claret membrane, which was consistent with the reported behavior of bO. Unexpectedly, the insertion and deletion in loop EF perturbed the photocycle of the regenerated ecaR‐1002. The accumulation of long‐lived N‐ and O‐like intermediates suggested that the insertion and deletion slowed down the proton uptake steps at the cytoplasmic surface.
Remarkable Suppression of [2+2] Cycloaddition during Nonresonant Two‐photon Photoreaction of trans‐Stilbene in the Presence of Tetramethylethylene
Authors: Miyazawa Takashi , Liu Chengyou , Koshihara Shin‐ya , Kira Mitsuo
Published: January 2008

Abstract— Nonresonant two‐photon excitation of /rans‐stilbene in the presence of an excess amount of tetramethylethylene induced predominantly cis‐trans isomerization; the [2+2] intermolecular cycloaddition pathway was remarkably suppressed, in contrast to the one‐photon excitation under similar conditions, where the cycloaddition is known to be the major pathway.
Spectroscopic Mimicry for the Protonated Retinal Schiff Base in vivo with Modified Amphiphilic Clay Interlayers as a Possible Model of Opsin Environment
Authors: Sasaki Masako , Fukuhara Taro
Published: January 2008

Abstract— We have found that clay acts as a novel model matrix for the amphiphilic protein‐opsin to mimic the visible absorption spectrum of a protonated retinal Schiff base (RSB) in vivo. Without strong acids at ambient temperature, a visible broad absorption spectrum with a LDmax at 530 nm covering the range from 400 to 680 nm was achieved for the protonated RSB with cationic surfactant‐modified montmorillonite clay. The interlayers of the dimethyloctadecylamine (DOA) modified clay were found to provide amphiphilic space allowing the amphiphilic RSB to be intercalated easily and sequentially and protonated by the DOA. It is proposed that the visible absorption spectrum at LD, 530 nm was attributable to electrostatic effects, permitting the appropriate distance between the nitrogen of the protonated RSB and the negatively charged clay interlayers and also to the anisotropic orientation of the RSB molecules in the interlayers.
A Resonance Raman Study Of the C=C Stretch Modes in Bovine and Octopus Visual Pigments with Isotopically Labeled Retinal Chromophores
Authors: Huang L. , Deng H. , Koutalos Y. , Ebrey T. , Groesbeek M. , Lugtenburg J. , Tsuda M. , Callender R. H.
Published: January 2008

Abstract— Previous resonance Raman spectroscopic studies of bovine and octopus rhodopsin and bathorhodopsin in the C–C stretch fingerprint region have shown drastically different spectral patterns, which suggest different chromophore‐protein interactions. We have extended our resonance Raman studies of bovine and octopus pigments to the C=C stretch region in order to reveal a more detailed picture about the difference in retinal‐protein interactions between these two pigments. The C=C stretch motions of the protonated retinal Schiff base are strongly coupled to form highly delocalized ethylenic modes located in the 1500 to 1650 cm−1 spectral region. In order to decouple these vibrations, a series of 11,12‐D2‐labeled retinals, with additional 13C labeling at C8, C10, C11 and C14, respectively, are used to determine the difference of specific C=C stretch modes between bovine and octopus pigments. Our results show that the C9=C10 and C13=C14 stretch mode are about 20 cm−1 lower in the Raman spectrum of octopus bathorhodopsin than in bovine bathorhodopsin, while the other C=C stretch modes in these two bathorhodopsins are similar. In contrast, only the C9=C10 stretch mode in octopus rhodopsin is about 10 cm−1 lower than in bovine rhodopsin, while other C=C stretches are similar.
The Photochemical Isomerization Kinetics of Urocanic Acid and Their Effects upon the in vitro and in vivo Photoisomerization Action Spectra
Authors: Hanson Kerry M. , Simon John D.
Published: January 2008

Abstract— The kinetic rate equation for the photoreversible photoisomerization between trans ‐urocanic acid (UA) and cis‐UA following absorption of UV radiation has been solved and used to show that the maximum of the trans ‐UA photoisomerization action spectrum depends upon both the initial trans‐UA concentration irradiated in an experiment and upon the irradiation dose used to determine the amount of cis‐UA generated. This kinetic model can be used to explain current discrepancies between in vitro and in vivo photoisomerization action spectra reported in the literature.
Polarization Filter for Biomedical Tissue Optical Imaging
Authors: Demos S. G. , Papadopoulos A. J. , Savage H. , Heerdt Alexandra S. , Schantz S. , Alfano R. R.
Published: January 2008

Abstract— A technique based on the degree that light is depolarized when propagating inside tissues is demonstrated for optical imaging in biomedical systems. The difference in the degree of polarization of the emerging light allows for the discrimination of different types of tissues. The technique was investigated in the transillumination and back‐scattering geometry and in both cases the potential of this method to image and separate out different types of tissues is demonstrated.
Photodynamic Action: From Paramecium to Photochemotherapy*
Authors: Spikes John D.
Published: January 2008

It has been a most interesting and often exciting experience to have been involved in the study of photodynamic reactions during this period of rapid expansion of research and the development of so many promising applications of photosensitized reactions to biomedical problems. As indicated above, the present level of activity is overwhelming at times. I should probably not admit it, but occasionally, after going through masses of new literature, I become a bit nostalgic, and reminisce a little on the earlier days when the study of photodynamic reactions was a quiet, noncompetitive, relaxing and gentlemanly pursuit.
Investigations of the Enhancer Effect of a High‐Salt Concentration Medium on the Luminol Chemiluminescent Reaction
Authors: Collaudin Agnès Berger , Blum Loïc J.
Published: January 2008

The enhancer effect of a high‐salt concentration medium on the luminol chemiluminescence reaction catalyzed by either soluble or immobilized peroxidase has been investigated. Some widely used salts were tested at high concentration (up to 3 mol L): potassium chloride, sodium chloride, ammonium sulfate and calcium chloride. The magnitude of the light intensity enhancement depends on the nature of the salt and on the form of the peroxidase, i.e. free in solution or immobilized. The enhancement is observed whether the catalyst of the chemiluminescence reaction is peroxidase or ferricyanide. Both the enhanced or nonenhanced luminol chemiluminescence spectra have a maximum wavelength emission at around 425 nm. The results reported in this study are in favor of an action of the salts on the nonenzymatic steps of the luminol chemiluminescence reaction rather than a modification of the enzymatic process.
The Photobiology of Melanin
Authors: Hill Helene Z.
Published: January 2008

Introduction
Photobiological Properties of Methylene Violet*
Authors: Morrison Harry , Mohammad Taj , Kurukulasuriya Ravi
Published: January 2008

The interaction of methylene violet (MV) and 4‐bromo‐methylene violet (BrMV) with calf thymus and super‐coiled φX174 phage RF I DNA is reported. Measurements employing UV‐visible absorption spectroscopy and equilibrium dialysis give evidence for the formation of complexes by each dye with DNA in the dark. They covalently bind to DNA, and MV nicks DNA, when the nucleic acid/dye mixtures are irradiated with visible light in a deoxygenated environment. Quantum efficiencies for singlet oxygen formation are 0.27 and 0.25 for MV and BrMV, respectively. A higher value (0.49) is observed for 4‐iodomethyIene violet (IMV).

The MV and BrMV interact with DNA in the dark to form complexes that are observable by absorption and emission spectroscopy and by equilibrium dialysis. When mixtures of the dyes and DNA are irradiated with visible light, both incorporation of the dye into the nucleic acid and nicking of the DNA are observed. These dyes generate singlet oxygen with quantum yields ranging from 0.25 for MV to 0.49 for IMV.
Blue Light‐induced Acidification of the Medium and the Uptake of Nitrate in a Nitrate‐starved Chlorella
Authors: Kamiya Akio
Published: January 2008

When cells of nitrate‐starved Chlorella kessleri (Fott et Novakova, no. 211‐11h) were suspended in phosphate buffer containing nitrate, they could barely take up nitrate in the dark. The addition of glucose resulted in the initiation of nitrate uptake by Chlorella. Irradiation with blue light stimulated the uptake of nitrate about two‐fold as compared with those of glucose‐treated cells and the acidification of the suspension medium, which, after 60‐90 min of blue irradiation, turned to alkalinization. These effects of blue light on the uptake of nitrate and pH changes were also observed in nitrate‐starved colorless (Fott et Novakova, no. 9.80) and yellow (Fott et Novakova, no. 211‐11h/20) mutants of C. kessleri. Staurosporine and K252a, potent inhibitors of protein kinase C, inhibited the blue light‐induced acidification of the medium and nitrate uptake. The data are discussed with regard to transduction of the signal for blue light‐induced acidification and nitrate uptake.
Kinetics and Yield of Singlet Oxygen Photosensitized by Hypericin in Organic and Biological Media
Authors: Ehrenberg Benjamin , Anderson Jamey L. , Foote Christopher S.
Published: January 2008

The spectroscopy and photophysics of the photosensitizer hypericin when in homogeneous solutions and when bound to liposomes were studied. Hypericin was found to partition efficiently into DMPC liposomes, with a binding constant of 58 (mg lipid/mL)−1. In these liposomes the singlet oxygen production quantum yield was 0.43 ± 0.09. To determine the deactivation constant of singlet oxygen in lipid bilayers for the first time, we calculated extrapolated values from its quenching by DMPC and lecithin in homogeneous solutions and obtained decay times of 36.4 and 12.2 μs, respectively. We also measured the quenching of singlet oxygen, sensitized by hypericin in DMPC liposomes, by NaN3, diphenyl isobenzofuran and H2,O: D2O mixtures and explained the results on the basis of singlet oxygen diffusing rapidly out of the lipid bilayer into the aqueous medium. The observed temperature effect on the lifetime of singlet oxygen of about 50% over a 15°C range in liposome suspension contrasts with a 3% change in a homogeneous solution in 1‐nonanol and is explained by the temperature effect on the diffusion out of the liposome. A strong pH effect was observed, indicating that the deprotonated species formed above about pH 10 is a much weaker photosensitizer of singlet oxygen than the native, protonated species.
Preferential Relative Porphyrin Enrichment in Solar Keratoses upon Topical Application of ^‐Aminolevulinic Acid Methylester
Authors: Fritsch Clemens , Homey Bernhard , Stahl Wilhelm , Lehmann Percy , Ruzicka Thomas , Sies Helmut
Published: January 2008

Topically applied δ‐aminolevulinic acid is used efficiently for the treatment of solar keratoses by photodynamic therapy. Recent animal studies suggest that porphyrin sensitization of epithelial tissue is improved by using esters rather than free δ‐aminolevulinic acid. The present study examines porphyrin metabolite formation after topical application of δ‐aminolevulinic acid or δ‐aminolevulinic acid methylester in human solar keratoses versus adjacent normal skin. Levels of total porphyrins, porphyrin metabolites and protein were measured in skin samples excised after 1 and 6 h. Higher levels of porphyrins were observed in solar keratoses than in normal skin with both substances. Maximum porphyrin levels were present in solar keratoses treated with δ‐aminolevulinic acid for 6 h. However, the ratio of porphyrins in solar keratoses versus adjacent normal skin was higher with 8‐aminolevulinic acid methylester. The pattern of porphyrins showed no significant difference between normal and afflicted skin, protoporphyrin being predominant. The results suggest that application of free δ‐aminolevulinic acid may be more effective in sensitizing solar keratoses. However, treatment with 8‐aminolevulinic acid methylester leads to a preferential enrichment of porphyrins within lesional skin.
Photoinduced Charge Separation in Reverse Micelles Prepared with Benzylhexadecyldimethylammonium Chloride (BHDC). The Electron‐Transfer Reaction between Pyrene and N,N‐Dimethylaniline*
Authors: Borsarelli Claudio D. , Cosa Juan J. , Previtali Carlos M.
Published: January 2008

Laser flash photolysis was used to investigate the formation of radical ions produced in the quenching of the pyrene‐N,N'‐dimethylaniline exciplex by reverse micelles made with benzylhexadecyldimethylammonium chloride (BHDC) dispersed in benzene or chlorobenzene. The radical ion quantum yields, φion, were determined as a function of BHDC concentration and the amount of water dispersed. They were strongly dependent on the composition of the media. The charge separation was more effective in the BHDC‐benzene than in the BHDC‐chlorobenzene system. The results are discussed in terms of the properties of the micellar interface and the fast exchange of material produced by collisions between reverse micelles.
4‐Terf‐Butylperoxymethyl‐9‐Methoxypsoralen as Intercalating Photochemical Alkoxyl‐Radical Source for Oxidative DNA Damage
Authors: Adam Waldemar , Arnold Markus A. , Grimm Günther N. , Saha‐Mölter Chantu R. , Dall'Acqua Francesco , Miolo Gorgia , Vedaldi Daniela
Published: January 2008

We describe the synthesis of a novel psoralen peroxide 1 that generates on irradiation (350 nml alkoxyl radicals, namely tert‐butoxyl radicals, as confirmed by electron spin resonance studies with the spin trap 5,5‐dimethyl‐pyrroline‐N‐oxide. The radical source intercalates into the DNA, which has been demonstrated by linear‐flow‐dichroism measurements. Thus, the alkoxyl radicals are formed advantageously directly in the DNA matrix. In supercoiled pBR322 DNA, the generation of strand breaks by the photochemically or metal‐catalyzed generated alkoxyl radicals is demonstrated. Photosensitization by the psoralen chromophore was excluded because similar substances that do not release radicals caused no DNA damage, nor were the photoproducts of the peroxide 1 active. With calf thymus DNA, 8‐oxoGua and small amounts of guanidine‐releasing products, e.g. oxazolone, were observed. However, in these reactions the photoproduct also displayed some DNA‐oxidizing capacity.
Estimation of Pigment Stoichiometries in Photosynthetic Systems of Purple Bacteria: Special Reference to the (Absence of) Second Carotenoid in LH2
Authors: Arellano Juan B. , Raju B. Bangar , Naqvi K. Razi , Gillbro Tomas
Published: January 2008

Abstract— In this short communication we present the stoichiometric ratio of bacteriochlorophyll, bacteriopheophytin and carotenoids in a few photosynthetic purple bacteria complexes (whose two‐dimensional or three‐dimensional structures are well known) determined using the spectrum‐reconstruction method (SRCM). An important conclusion of our pigment stoichiometric analysis is the evidence for the absence of the second carotenoid in the light‐harvesting complex 2 (LH2). In the process, we also highlight the useful application of SRCM in determining the molar extinction coefficients of carotenoids present in LH1, LH2 or reaction centers for which these values are not known due to isolation problems and/or stability.