bluuebunny/crossref_metadata_2025 huggingface dataset:
LONG‐WAVELENGTH UVA RADIATION INDUCES OXIDATIVE STRESS, CYTOSKELETAL DAMAGE and HEMOLYSIS*
Authors: Godar Dianne E. , Thomas Delma P. , Miller Sharon A. , Lee Wah
Published: January 2008

Abstract— We investigated the ability of the different wavelength regions of UV radiation, UVA(320–400 nm), UVB(290–320 nm) and UVC(200–290 nm), to induce hemolysis. Sheep erythrocytes were exposed to radiation from either a UVA1 (>340 nm) sunlamp, a UVB sunlamp, or a UVC germicidal lamp. The doses used for the three wavelength regions were approximately equilethal to the survival of L5178Y murine lymphoma cells. Following exposure, negligible hemolysis was observed in the UVB‐ and UVC‐irradiated erythrocytes, whereas a decrease in the relative cell number (RCN), indicative of hemolysis, was observed in the UVA 1‐exposed samples. The decrease in RCN was dependent on dose(0–1625 kj/m2), time(0–78 h postirradiation) and cell density (106‐107 cells/mL). Hemolysis decreased with increasing concentration of glutathione, hemoglobin or cell number, while the presence of pyruvate drastically enhanced it. Because scanning spectroscopy(200–700 nm) showed that hemoproteins and nicotinamide adenine dinucleotides were oxidized, cytoplasmic oxidative stress was implicated in the lytic mechanism. Further evidence of oxidation was obtained from electron micrographs, which revealed the formation of Heinz bodies near the plasma membrane. The data demonstrate that exposure of erythrocytes to UVA1, but not UVB or UVC, radiation causes oxidation of cytoplasmic components, which results in cytoskeletal damage and hemolysis.
DETECTION OF THE EXCITED SINGLET STATE OF A DEPROTONATED, REDUCED FLAVIN
Authors: Heelis Paul F. , Hartman Rosemarie F. , Rose Seth D.
Published: January 2008

Abstract— The excited singlet state of a deprotonated, reduced flavin [1, 5‐dihydro‐N(3)‐carboxymethyllumiflavin] in aqueous solution at pH 8 has been detected by laser flash photolysis. The broad absorption band maximized at ∼ 490 nm (ε= 9.9 × 103M‐1 cm‐1). The lifetime of the transient was found to be 100 ± 15 ps. The lifetime was not affected by the presence of pyrimidine dimers, which would be monomerized under these conditions. A longer‐lived transient, tentatively identified as the solvated electron, was also detected. The neutral reduced flavin did not give a detectable transient.
DRAMATIC IMPROVEMENTS IN VIRAL INACTIVATION WITH BROMINATED PSORALENS, NAPHTHALENES AND ANTHRACENES
Authors: Rai Saroj , Kasturi Chandrika , Grayzar Jennifer , Platz Matthew S. , Goodrich Raymond P. , Yerram Nagender R. , Wong Victoria , Tay‐Goodrich Boon H.
Published: January 2008

Amino or polyamino derivatives of naphthalene (N‐H), anthracene (A‐H) and 8‐alkoxypsoralen (PSR‐H) were prepared along with their monobrominatcd analogs (N‐Br, A‐Br and PSR‐Br). The ammonium salts of these compounds are all water soluble and bind strongly to calf thymus DNA and to λ phage, a double‐helical DNA, protein‐coated virus. Binding of the sensitizer to DNA occurs, presumably by a mixture of hydrophobic, intercalative and electrostatic interactions. Relative binding constants to calf thymus DNA and to λ phage were measured by the cthidium bromide fluorescence quenching assay. In general the brominated analogs bind more tightly to calf thymus DNA and to the virus than to the nonhalogenated analogs. It is demonstrated that the brominated aromatics are much more effective at inactivating λ phage upon photoactivation (λ 310 or 350 nm) than are their nonbrominated analogs. At identical sensitizer concentrations (by weight) and light flux N‐Br, A‐Br, and PSR‐Br produce 5–6 more logs of viral inactivation than their nonbrominated counterparts (N‐H, A‐H and PSR‐H, respectively). The bromine effect may originate from light‐induced electron transfer and subsequent cleavage of the C‐Br bond of the sensitizer radical anion bonds to form aryl radicals. Singlet oxygen cannot be responsible for the viral inactivation because the brominated sensitizers are equally effective in the presence and absence of oxygen. Dithiothreitol does not protect λ phage from light‐induced inactivation by the brominated sensitizer thereby demonstrating that the photogenerated reactive intermediates responsible for the effect are complcxed to the virus and are not generated free in solution.
IMINIUM SALT OF COPPER BENZOCHLORIN (CDS1), A NOVEL PHOTOSENSITIZER FOR PHOTODYNAMIC THERAPY: MECHANISM OF CELL KILLING
Authors: Hampton James A. , Skalkos Dimitris , Taylor Paula M. , Selman Steven H.
Published: January 2008

The mechanism of cell killing by CDS1, an iminium salt of octaethylbenzochlorin with copper in the aromatic ring, in combination with light from a noncoherent light source was investigated. Using a standard clonogenic assay and the AY‐27 FANFT turnor line. photoactivation of CDS1 was shown to be cytotoxic. The photodynamic cell killing ability of CDS1 required the presence of molecular oxygen. The reactive species generated by light activation of CDS1 were effectively quenched by N.N'‐diphenyl‐p‐phenylenediamine. Additionally, the photodynamic effect of CDS1 was not cnhanced by dcuterium oxide. To characterize the reactive oxygen species generated by the photoactivation of CDS1 the well‐characterized erythrocyte ghost model was used. Superoxide dismutase and catalase were potcnt inhibitors of CDS1‐induced lipid peroxidation of erythrocyte membranes. Sodium azide only partially inhibited lipid peroxidation. These findings differed from the known singlet oxygen generator, tin (II) etiopurpurin dichloride (SnET2). Sodium azide was a potent inhibitor of SnET2‐induced lipid peroxidation, whereas superoxide dismutase and catalase were totally ineffective. Based on these results, we conclude that CDS1 requires the presence of molecular oxygen for cell killing to occur but appcars to act primarily through a non‐singlet oxygen mechanism.
PHOTODEGRADATION AND in vitro PHOTOTOXICITY OF FENOFIBRATE, A PHOTOSENSITIZING ANTI‐HYPEIUIPOPROTEINEMIC DRUG
Authors: Vargas Franklin , Canudas Nleves , Miranda Miguel A. , Boscar Francisco
Published: January 2008

The phototoxic anti‐hyperlipoproteinemic drug fenofibrate was found to be photolabile under aerobic and anaerobic conditions. Irradiation under argon of a methanol solution of this drug produced the photoproducts isopropyl 4‐(1‐[4‐chlorophenyl]‐1,2‐dihydroxy)ethylphenoxyisobutyrate, 1,2‐bis(4‐chlorophenyl)‐1,2‐bis(4‐[isopro‐poxycarbonylisopropoxy]phenyl)ethane‐1,2‐diol and 4‐(4‐chlorobenzoyl)phenol, while under oxygen the photoproducts were 4‐chloroperbenzoic acid, methyl 4‐chlorobenzoate, 4‐chlorobenzoic acid and singlet oxygen, as evidenced by trapping with 2,5‐dimethylfuran. These results can be rationalized through hydrogen abstraction by excited fenofibrate, to afford a free radical as key intermediate. Biologically active antioxidants such as glutathione and cysteine efficiently reduced 4‐chloroperbenzoic acid to 4‐chlorobenzoic acid. The involvement of an electron transfer mechanism is suggested by detection (UV‐vis spectrophotometry) of the radical cation TMP+ during the oxidation of tetramethylphenylenediamine (TMP) with 4‐chloroperbenzoic acid. Fenofibrate was phototoxic in vitro when examined by the photohemolysis test, both under oxygen and argon atmosphere, although the photohemolysis rate was markedly lower under anaerobic conditions. The photoproducts 4‐(1‐[4‐chlorophenyl]‐1,2‐dihy‐droxy)ethylphenoxyisobutyrate and 4‐chloroperbenzoic acid induced hemolysis in the dark however, this effect was quantitatively less important than photohemolysis by fenofibrate. On the other hand, fenofibrate photosensitized peroxidation of linoleic acid, monitored by the UV detection of dienic hydroperoxides. Based on the inhibition of this process upon addition of butylated hydroxyanisole, a radical chain (type I) mechanism appears to operate. In summary, fenofibrate is phototoxic in vitro. This behavior can be explained through the involvement of free radicals, singlet oxygen and stable photoproducts.
PRIMARY DNA DAMAGE, HPRT MUTATION AND CELL INACTIVATION PHOTOINDUCED WITH VARIOUS SENSITIZERS IN V79 CELLS
Authors: Noodt Barbara B. , Kvam Egil , Steen Harald B. , Moan Johan
Published: January 2008

DNA strand breaks and hypoxanthine guanine phosphoribosyl transferase (HPRT) mutants were measured in parallel in photochemically treated (PCT) cells and compared at the same level of cell survival. Chinese hamster fibroblasts (V79 cells) were either incubated with the lipophilic dyes tetra(3—hydroxyphenyl)porphyrin (3THPP) and Photofrin II (PII), the anionic dye meso‐tetra(4—sulfonatophenyl)porphine (TPPS4) or the cationic dye meso‐tetra(N‐methyl‐4‐pyridyl)porphine (p‐TMPyPH2 before light exposure. In the cells, the lipophilic dyes were localized in membranes, including the nuclear membrane, while the hydrophilic dyes were taken up primarily into spots in the cytoplasm. In addition, the hydrophilic TPPS4 was distributed homogeneously throughout the whole cytoplasm and nucleoplasm. According to the HPRT mutation test, the mutagenicity of light doses survived by 10% of the cells was a factor of six higher in the presence of 3THPP than of PII, whereas for X‐rays it was a factor of three higher than for PCT with 3THPP. Light exposure in the presence of the hydrophilic dyes TPPS4 and p‐TMPyPH2 was not significantly mutagenic. There was no correlation between the induced rates of HPRT mutants and of DNA strand breaks. Thus, TPPS4 was the most efficient sensitizer with regard to DNA strand breaks when compared at the same level of cell survival, followed by 3THPP, PII and p‐TMPyPH2. Hence, the rate of DNA strand breaks cannot be used to predict the mutagenicity of PCT.
ANALYZING THE RED‐SHIFT CHARACTERISTICS OF AZULENIC, NAPHTHYL, OTHER RING‐FUSED AND RETINYL PIGMENT ANALOGS OF BACTERIORHODOPSIN*
Authors: Liu R. S. H. , Krogh Erik , Li Xiao‐Yuan , Mead Dennis , Colmenares L. U. , Thiel J. R. , Ellis Jeannette , Wong Darren , Asato A. E.
Published: January 2008

Prompted by the near infrared‐absorbing properties of some of the azulenic bacteriorhodopsin (bR) analogs, we have analyzed their absorption characteristics along with 11 new related ring‐fused analogs and the corresponding Schiff bases (SB) and protonated Schiff bases (PSB). The following three factors are believed to contribute to the total red shift of each of the pigment analogs (αRS): perturbation of the basic chromophore (SB shift, ΔSB), protonation of the SB (PSB shift, PSBS) and protein perturbation (the opsin shift, OS). For each factor, effects of structural modifications were examined. For the red‐shifted pigments, percent OS has been suggested as an alternate way of measuring protein perturbation. Computer‐simulated chromophores provided evidence against any explanation involving altered shapes of the binding pocket as a major cause for absorption differences. Implications of the current bR results on preparation of further red‐shifted bR and possible application to visual pigment analogs are discussed.
SPECTROSCOPIC CHARACTERIZATION OF TWO FORMS OF THE D1‐D2‐CYTOCHROME b559 COMPLEX FROM SUGAR BEET
Authors: Montoya Guillermo , Cases Rafael , Yruela Inmaculada , Picorel Rafael
Published: January 2008

Two D1‐D2‐cytochrome b559 complex forms, called RCIIa and RCIIb, with different pigment stoichi‐ometry were characterized using absorption and surface‐enhanced resonance Raman scattering spectroscopy and spectral gaussian deconvolution. Electronic absorption spectra of the RCIIb at 277 K showed significant differences compared to RCIIa, i.e. a strong decrease in the absorbance due to carotenoid and chlorophyll for the same amount of pheophytin. A reduced carotenoid and chlorophyll content in RCIIb was also observed in the surface‐enhanced resonance Raman scattering spectra. Spectral deconvolution elicited three main absorption bands at 680, 672 and 669–670 nm, which were ascribed to P680, pheophytin and accessory chlorophyll, respectively. In addition, a minor component around 667 nm was observed in the RCIIb, most probably due to some reaction center inactivation. Calculation of the relative area under the gaussians together with pigment stoichiometry data suggest that the 680, 672 and 669–670 nm components contain, respectively, two chlorophylls, two pheophytins and four chlorophylls for the RCIIa, and two chlorophylls, two pheophytins and two chlorophylls for the RCIIb.
LASER PHOTOLYSIS STUDY ON POLY(N‐VINYLCARBAZOLE) ADSORBED ON CELLULOSE SUBSTRATE
Authors: Mizuma Hirokazu , Fukumura Hiroshi , Masuhara Hiroshi
Published: January 2008

Abstract Triplet state and photoinduced charge separation dynamics under adsorption was Confirmed for the first time for the polymer without or with coadsorbed electron acceptor, respectively. The absorption spectrum of the triplet polymer is similar to the Tn← T1 band of N‐ethylcarbazole, showing no appreciable interchromophoric interaction. Absorption spectra of the coadsorbed systems comprise the polymer cation and electron acceptor anion. The ion radicals on the cellulose substrate undergo mutual recombination, and simple uni‐ and bimolecular decay kinetics do not hold. This mechanism was compared with that for poly(N‐vinylcarbazole) film.
EFFECTS OF N‐PHENYLIMIDE S‐23142 AND N‐METHYL MESOPORPHYRIN IX ON THE SYNTHESIS OF THE PHYTOCHROME CHROMOPHORE IN PEA EMBRYONIC AXES
Authors: Konomi Koji , Li He‐Sheng , Kuno Norihito , Furuya Masaki
Published: January 2008

Abstract Treatment of imbibed embryonic axes taken from seeds of Pisum sativum with N‐phenylimide S‐23142, a herbicide that has been suggested to inhibit protoporphyrin synthesis, or with N‐methyl mesoporphyrin IX, an inhibitor of the iron chelatase for heme, resulted in a significant decrease in the amount of spectrophotometrically detectable phytochromc in the axes in both cases. However, the amount of immunochemically detectable phytochrome was not affected by either treatment. If S‐23142 inhibits the synthesis of protoporphyrin IX in pea, it appears that the conversion of protoporphyrinogen IX to protoporphyrin IX is involved in the biosynthesis of the phytochrome chromophore. The conversion of protoporphyrin IX to heme (Fe‐protoporpbyrin) also appears to be a step in the biosynthesis of the chromophore, since N‐methyl mesoporphyrin IX prevented the synthesis of spectrophotometrically detectable phytochrome but did not affect the magnesium chelatase activity required for the synthesis of chlorophyll in pea embryonic axes. The results suggest that protoporphyrinogen IX, protoporphyrin IX and heme are intermediates in the biogenesis of the phytochromc chromophore. The pathway to phytochromobilin might become fixed after protoporphyrin IX, being directed toward the Fe branch for heme rather than to the Mg branch for chlorophyll.
PHOTOSENSITIZED FORMATION OF ASCORBATE RADICALS BY RIBOFLAVIN: AN ESR STUDY
Authors: Kim Heasook , Kirschenbaum Louis J. , Rosenthal Ionel , Riesz Peter
Published: January 2008

Abstract— The riboflavin‐sensitized photooxidation of ascorbate ion (HA‐) to ascorbate radical (A‐) was followed by electron spin resonance (ESR) spectroscopy in conjunction with oxygen depletion measurements. In air‐saturated aqueous media, steady‐state amounts of A‐ are rapidly established upon irradiation. The ESR signal disappears within a few seconds after the light is extinguished–more slowly under constant irradiation as oxygen is depleted. No photooxidation was observed in deaerated media. Similar results were obtained with other flavins and when ascorbyl palmitate was substituted for HA‐. The effect of added superoxide dismutase, catalase, desferrioxamine, and singlet oxygen scavengers (NaN3 and tryptophan) was studied, as was replacement of water by D2O and saturation with O2. The results are indicative of ascorbate free radical production via direct reaction between ascorbate ion and triplet riboflavin in the presence of O2. While the presence of superoxide ion tends to reduce the steady‐state concentration of A‐, competition from the reaction of HA‐ with singlet oxygen is less apparent in this system (at HA‐≥ 1 mM) than in the previously studied aluminum phthalocyanine tetrasulfonate‐photosensitized reaction.
DETERMINATION OF RESIDUAL 4‐AMINOMETHYL‐4,5‘,8‐TRIMETHYLPSORALENAND MUTAGENICITY TESTING FOLLOWING PSORALEN PLUS UVA TREATMENT OF PLATELET SUSPENSIONS
Authors: Wagner Stephen J. , White Randy , Wolf Ludwig , Chapman John , Robinette Daniel , Lawlor Timothy E. , Dodd Roger Y.
Published: January 2008

Abstract— Psoralens and UVA light have been used in the laboratory to study the inactivation of viruses that may be infrequently present in platelet concentrates that are prepared for transfusion. In order to evaluate safety aspects of the treatment of platelet suspensions with 4'‐aminomethyl‐4,5',8‐trimethylpsoralen (AMT), we have investigated the residual levels and mutagenic potential of AMT after UVA phototreatment. 4'‐aminomethyl‐4,5',8‐trimethylpso‐ralen, at a final concentration of 40 μg/mL, was added to platelet suspensions which contained 16% plasma and a synthetic medium. Platelet suspensions containing AMT were irradiated with up to 7.2 J/cm2 UVA light under normal oxygen levels. Residual levels of AMT were determined by HPLC and a bioassay based on bacteriophage 0.6 inactivation. The photodestruction of AMT or its activity by UVA was characterized by a D37 value of 0.6 and 0.3 J/cm2 with HPLC or bioassay, respectively. At 2.4 J/cm2 UVA, which results in approximately 5 log10 inactivation of vesicular stomatitis virus (VSV) and retention of platelet in vitro properties, 12% (HPLC) to 9% (bioassay) AMT remained.

Like other psoralens, AMT was found to bind to serum proteins as shown by ultrafiltration. Results are consistent with approximately 36% of the initial drug load binding primarily to serum albumin. It was determined using 3H‐AMT that 9 to 18% of radioactivity was bound to platelets in the absence of irradiation. Similar fractions (13 to 18%) of AMT were bound to platelets after 3.6 J/cm2 UVA irradiation, and 8 to 10% of total AMT was associated with saline‐washed irradiated platelets and is presumably tightly bound.

Mutagenicity testing (Ames test, in the absence of UVA) was also carried out on the UVA irradiated platelet samples. With Salmonella tester strains which detect primarily base substitution mutations (TA100, TA1535 and TA102), no increase from background mutagenesis levels was observed with any of the samples. However, tester strains which detect frameshift mutations (TA98, TA1537, and TA1538) displayed significant increases in histidine revertants over background levels for irradiated and non‐irradiated AMT‐containing samples tested in the presence of S9 microsomal enzymes. In the absence of S9 activation, a mutagenic response was observed only with tester strain TA1537. All frameshift tester strains exhibited decreased numbers of induced revertants with lower residual AMT concentrations (which correlated with higher UVA dose). Significant mutagenesis was still observed for platelet suspensions irradiated with virucidal levels of UVA which maintain platelet in vitro function (2.4 J/cm2). These results suggest that residual available AMT is mutagenic in the Ames test and that the observed frameshift mutations may be caused by binding of AMT or its metabolites to nucleic acids in the absence of UVA light.
ELECTRONIC EFFECTS ON THE FLUORESCENCE OF TYROSINE IN SMALL PEPTIDES
Authors: Seidel Claus , Orth Andreas , Greulich Karl‐Otto
Published: January 2008

Abstract— It is shown for a series of tyrosine‐derivatives and tyrosine‐containing peptides that the amide group in combination with electron‐withdrawing substituents quenches the fluorescence of the phenol moiety. The ammonium group has the strongest electron‐withdrawing effect and thus the largest influence on the quenching rate. The peptide group itself does not quench the fluorescence. In a series of peptides with an increasing number of alanines the decreasing quenching efficiency or the peptide group due to the greater distance of the ammonium group is demonstrated. In tyrosine‐containing di‐ and tripeptides a linear correlation between the 13C‐NMR chemical shift δ of the C2 atom of various aliphatic amino acids and the fluorescence‐quenching constant confirms the hypothesis that electron‐withdrawing and donating groups are modulating the fluorescence‐quenching efficiency of the peptide group. In small peptides the fluorescence lifetime of tyrosine is characteristic for the neighboring amino acids. Using model substances the redox properties of a peptide group and the phenol ring were studied electrochemically. The highest occupied molecular orbital of the tyrosine (1.4 V vs saturated calomel electrode [SCE]) and the lowest unoccupied molecular orbital of the peptide group (‐3.12 V vs SCE) have appropriate energies for a photoinduced electron transfer reaction. For solute‐quenching experiments quencher molecules can be systematically selected.
PHOTOSENSITIZATION WITH BACTERIOCHLORINS
Authors: Kessel David , Smith Kevin M. , Pandey R. K. , Shiau F.‐Y. , Henderson Barbara
Published: January 2008

Abstract— Biophysical and photobiological properties of a group of bacteriochlorins were compared with efficacy of these products for photodynamic therapy of murine tumors. Predictive factors for selective photosensitization in vivo include affinity binding to lipoproteins greater than albumin, extinction coefficient at the wavelength of irradiation and tumor/skin distribution. Efficacy was correlated with circulating plasma levels of the different sensitizers but not with the photodynamic therapy response in cell culture.
ULTRAVIOLET LIGHT‐INDUCED FREE RADICAL FORMATION IN SKIN: AN ELECTRON PARAMAGNETIC RESONANCE STUDY
Authors: Jurkiewicz Beth Anne , Buettner Garry R.
Published: January 2008

It has been suggested that ultraviolet light induces free radical formation in skin, leading to photoaging and cancer. We have demonstrated by electron paramagnetic resonance that the ascorbate free radical is naturally present in unexposed skin at a very low steady state level. When a section of SKH‐1 hairless mouse skin in an EPR cavity is exposed to UV light (4,500 J m−2−1, Xe lamp, 305 nm cutoff and IR filters), the ascorbate free radical signal intensity increases. These results indicate that UV light increases free radical oxidative stress, consistent with ascorbate's role as the terminal, small‐molecule antioxidant. The initial radicals produced by UV light would have very short lifetimes at room temperature; thus, we have applied EPR spin trapping techniques to detect these radicals. Using α‐[4‐pyridyl 1‐oxide]‐N‐tert‐butyl nitrone (POBN), we have for the first time spin trapped a UV light‐produced carbon‐centered free radical from intact skin. The EPR spectra exhibited hyperfine splittings that are characteristic of POBN/alkyl radicals, aN= 15.56 G and aH= 2.70 G, possibly generated from membrane lipids as a result of β‐scission of lipid alkoxyl radicals. Iron can act as a catalyst for free radical oxidative reactions; chronic exposure of skin to UV radiation causes increased iron deposition. Using our spin trapping system, we have shown that topical application of the iron‐chelator, Desferal, to a section of skin reduces the UV light‐induced POBN adduct radical signal. These results provide direct evidence for free radical generation and a role for iron in UV light‐induced dermatopathology. We suggest that iron chelators can serve as photoprotective agents by preventing these oxidations.
FLUORESCENCE QUENCHING OF PYRENE DERIVATIVES BY NITROXIDES IN MICROHETEROGENEOUS SYSTEMS
Authors: Encinas M. V. , Lissi E. A. , Alvarez J.
Published: January 2008

Abstract Fluorescence quenching of pyrene derivatives by 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO), 4‐oxo‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy and 4‐hydroxy‐2,2,6,6‐tetramethylpiperidinyl‐1‐oxy has been measured in homogeneous solvents and microheterogeneous systems: cetyltrimethylammonium chloride micelles, large unilamellar vesicles of dioctadecyldimethylammonium chloride and dipalmitoylphosphatidylcholine (DPPC) and rat liver microsomes. The extent of intraaggregate quenching is mostly determined by the quencher incorporation to the micro‐phases. In particular, it is observed that quenching by TEMPO in vesicles is considerably faster when the bilayer is in the liquid crystalline state. This significant increase in quenching rate with the melting of the bilayer is not observed for the other TEMPO derivatives, indicating that the effect of the lipid organization upon the solubility is related to the hydrophobicity of the solute. The data obtained in rat liver microsomes at 37°C show a pattern very similar to that observed in DPPC vesicles in the liquid crystalline state.
HYPERICIN PHOTOSENSITIZATION IN AQUEOUS MODEL SYSTEMS
Authors: Senthil Velu , Jones Linda Ramball , Senthil Kannakj , Grossweiner Leonard I.
Published: January 2008

Abstract Photosensitization of lysozyme, liposomes, ghosts and intact red blood cells (RBC) was investigated for aqueous hypericin. The effects of azide ion, 1,4‐diazabicyclo(2.2.2)octane, and superoxide dismutase on photosensitized inactivation of lysozyme in 0.5% Triton X‐100 indicate that singlet oxygen is the major inactivating intermediate with a contribution from superoxide. The singlet oxygen quantum yield (ΦΔ) scaled to methylene blue is 0.49 ± 0.06 at monochromatic wavelengths from 514 to 600 nm. Relative values of ΦΔ based on lysozyme inactivation for different vehicles are: 0.5% Triton X‐100 (1.13), human serum albumin (0.65), Cremophor‐EL(0.76), Cremophor‐RH40 (0.98), egg phosphatidylcholine (EPC) liposomes (0.04), hydrogenated soy phosphatidylcholine (HSPC) liposomes (<0.01). Hypericin photosensitized lipid peroxidation of EPC liposomes and RBC ghosts. Extensive cross‐linking of ghost membrane proteins occurred during the initial stages of lipid peroxidation. Prompt photohemolysis was used as the assay of RBC membrane damage. The photohemolysis curves are modeled with multihit target theory based on the “hit number” (n) and the target cross section (v). The values of v and the conventional “1/t50” parameter are equivalent determinants of the photohemolysis rate. The photohemolysis curves are in good agreement with n = 15 for incubation in phosphate‐buffered saline at different hypericin concentrations and with additives. The measurements for other vehicles led to n = 19 for Cremophor‐EL and n = 3 for EPC and HSPC liposomes, indicating that the kinetics of photohemolysis depend on the conditions of incubation.
LONG‐WAVE ULTRAVIOLET RADIATION INDUCES PROTEIN KINASE C IN NORMAL HUMAN KERATINOCYTES
Authors: Steidl Matsui Mary , Wang Nianci , Macfarlane Deborah , Deleo Vincent A.
Published: January 2008

Abstract Skin tumor promotion by phorbol ester is believed to be mediated by the phospholipid‐dependent ser/ thr kinase, protein kinase C (PKC). Long‐wave ultraviolet radiation (320‐400 nm, UVA), which has also been shown to promote skin tumors, induces elevated levels of PKC in murine fibroblasts, suggesting that UVA may promote the development of basal and squamous cell skin cancers by a mechanism involving PKC. To examine UVA effects on PKC in a model relevant to skin, we maintained normal human epidermal keratinocytes (NHEK) in serum‐free medium and exposed the cultured cells to various doses of UVA or to the phorbol ester, 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA). Fifty minutes after exposure to UVA (5‐20 J/cm2), PKC activity was elevated up to three‐fold in NHEK cytosolic fractions, and membrane‐associated PKC activity was elevated up to two‐fold by UVA. The TPA treatment induced a 10‐fold increase in membrane‐associate PKC activity only. Immunoblot analysis suggested that a UVA‐induced increase in PKC protein occurred. Both UVA and TPA reduced the cell number by 50‐75% in the first 24‐48 h; however, irradiated cultures began to recover at 72 h post‐UVA due to an increased proliferative rate beginning after 48 h. Treatment with TPA induced a high level of differentiation as measured by cornified envelope formation. Ultraviolet A irradiation exposure was not followed by increased differentiation. These findings suggest that acute UVA exposure elevates PKC activity in human keratinocytes and may act through PKC to promote actinic skin cancer. The molecular mechanism is like to differ from that of the phorbol esters, however.
PHOTOSENSITIZATION SYSTEMS OF COVALENTLY LINKED PHTHALOCYANINE COMPLEXES IN BOTH BILAYER LIPID MEMBRANES AND TIN OXIDE PHOTOVOLTAIC CELL
Authors: Bi Zhi‐Chu , Qian Yue‐Ying , Zhao Xin‐Li , Shen Shu‐Yin , Yu Jia‐Yong , XU Hui‐Jun , Tien H. Ti
Published: January 2008

Abstract Zinc phthalolocyanine photosensitized donor‐acceptor systems for light energy conversion and for the design of photoelectrochemical molecular devices are presented. Covalently linked phthalocyanine complexes were incorporated in bilayer lipid membranes (BLM) and deposited on SnO2 transparent electrodes. Their photovoltages were measured and compared. It has been found that a more favorable orientation and closer proximity are attained in the diad compounds between the donor (phthalocyanine)‐acceptor (anthraquinone) pair than in the reference compound for efficient light‐induced charge separation and transfer. The triad compound is the best among all tested compounds. The decrease in the fluorescence yield and lifetime induced by quinones was examined and the apparent electron‐transfer rate constants were calculated.
THE EFFECT OF LASER IRRADIATION ON THE RELEASE OF bFGF FROM 3T3 FIBROBLASTS
Authors: Yu Wei , Naim John O. , Lanzafame Raymond J.
Published: January 2008

Studies have shown that low‐level laser irradiation increases the proliferation of fibroblasts in cell culture. The mechanism of action is unknown. Basic fibroblast growth factor (bFGF) is a multifunctional polypeptide that has been detected in most tissues and which supports cell proliferation and differentiation. The purpose of this study was to determine whether laser irradiation (660 nm) can stimulate production of bFGF from fibroblast cells in cell culture. Our study showed that fibroblasts irradiated with laser energy at 2.16 J/cm2 demonstrated increased cell proliferation and enhanced production of bFGF, whereas fibroblasts irradiated with laser energy at 3.24 J/cm2 neither demonstrated increased cell proliferation or an enhanced release of bFGF as compared to the control group. These results provide direct evidence that the proliferation of fibroblasts as a result of stimulation by low level laser irradiation may be associated with the autocrine production of bFGF from fibroblasts.
IMINIUM SALT BENZOCHLORINS: STRUCTURE‐ACTIVITY RELATIONSHIP STUDIES
Authors: Skalkos Dimitris , Hampton James A. , Keck Rick W. , Wagoner Miriam , Selman Steven H.
Published: January 2008

An iminium salt of copper(II) octaethylbenzochlorin (CDS1) is an effective new photosensitizer despite the fact that it does not produce singlet oxygen, does not fluoresce and the triplet state lifetime can only be less than 20 ns. A number of octaethylbenzochlorin derivatives were synthesized in order to determine the structural component(s) that is(are) responsible for the photodynamic action of these new photosensitizers. Studies utilizing the N‐(4‐[5‐nitro‐2‐furyl]‐2‐thiazolyl)formamide‐induced urothelial tumor revealed that the coexistence of the copper inside the aromatic ring and the iminium group at the meso position are required for the photodynamic effect.
PHOTOSENSITIZED INACTTVATION OF INFECTIOUS DNA BY UROCANIC ACID, INDOLEACRYLIC ACID AND RHODIUM COMPLEXES
Authors: Mohammad Taj , Tessman Irwin , Morrison Harry , Kennedy Matthew A. , Simmonds Stephen W.
Published: January 2008

Naked, infectious single‐stranded (ss) and double‐stranded (ds) DNA from phages SI3 and G4 were irradiated with 308 nm UV radiation in the absence and presence of several photobiologically active compounds: E‐ and Z‐urocanic acid (E‐ and Z‐UA), their methyl esters (E‐ and Z‐MU), E‐ and Z‐indoleacrylic acid (E‐ and Z‐IA), cis‐dichlorobis(1,10‐phenanthroline)rhodium(III) chloride (cDCBPR) and tris(1,10‐phenanthroline)rhodium (III) perchlorate (TPR). E‐urocanic acid protects against cyclobutane pyrimidine dimer formation in ssDNA but concomitantly photosensitizes the formation of other lesions that inactivate ssDNA. Z‐urocanic acid also protects ssDNA against such dimerization but without the associated sensitized damage. The methyl ester isomers behave similarly. There is no such differential activity observed for the IA isomers, both of which sensitize the inactivation of ssDNA. Photostationary state mixtures of both UA and IA efficiently sensitize the inactivation of dsDNA, and cDCBPR strongly protects ssDNA from UV damage, while TPR is a significant sensitizer. Both of these metal complexes sensitize the inactivation of dsDNA slightly. For all compounds, cyclobutane pyrimidine dimers were the predominant lethal lesions produced by sensitization of the dsDNA, but they were not the major lethal lesions created by sensitization of the ssDNA. In the case of dsDNA, both UA and IA created pyrimidine dimers with a high degree of potential for mutagenesis, as determined by an assay that monitors the frequency of mutations following the spontaneous deamination of cytosine in photodimers.
4′,5′‐SUBSTITUTED METHYLANGELICINS: PHOTOCYCLOADDUCTS WITH PYRIMIDINE BASES OF DNA
Authors: Miolo Giorgia , Lucchini Vittorio , Rodighiero Paolo , Dall'Acqua Francesco , Caffieril Sergio
Published: January 2008

The isolation and characterization of photocycloadducts with pyrimidine bases from DNA samples irradiated (365 nm) in the presence of four 4′,5′‐substituted methylangelicins was performed. All these furocoumarins yielded mainly the cis‐syn furan‐side cycloadduct with thymine. For 4′,5′‐dimethyl‐, 5,4′,5′‐trimethyl‐ and 6,4′,5′‐trimethylangelicin this adduct was accompanied by two pyrone‐side adducts (cis‐syn and cis‐anti), whereas the 4,4′,5′‐trimethyl derivative gave the furan‐side adduct with cytosine.

The characterization of the regio‐ and stereochemistry of the adducts was accomplished by 1H NOE (nuclear Overhauser effect) and 1H‐13C HMBC (heteronuclear multiple‐bond connectivity) spectroscopies.

The formation of different cycloadducts in DNA by the various derivatives highlights the role of the methyl groups in determining the regio‐ and stereochemistry of the cycloaddition.
TARGETED PHOTOCHEMICAL MODIFICATION OF HIV‐DERIVED OLIGORIBONUCLEOTIDES BY ANTISENSE OLIGODEOXYNUCLEOTIDES LINKED TO PORPHYRINS
Authors: Mastruzzo Lidia , Woisard Anne , Ma David D. F. , Rizzarelli Enrico , Favre Alain , Doan Trung Le
Published: January 2008

Abstract Antisense oligodeoxynucleotides directed against a 24‐mer RNA derived from the long terminal repeat (LTR) region of HIV were linked to proto‐ and methylpyrroporphyrin and their zinc derivatives. The oligonucleotide‐porphyrin conjugates were tested for their ability to induce photodamage on the target RNA. Upon hybridization followed by irradiation at 405 nm, the photochemical reaction led to photocross‐linking of the antisense derivative to the RNA substrate. The protoporphyrin exhibited a much higher cross‐linking yield than the methylpyrroporphyrin while the Zn‐porphyrin derivatives were found to be less efficient than their corresponding nonmetallated congeners. The specificity of the photocross‐linking reaction between the porphyrin‐oligomer and its target RNA was demonstrated by the following evidence: (1) hybrid formation was required for photocross‐linking to occur, (2) the sites of cross‐linking on the target RNA were identified at G residues located in close proximity to the porphyrin photoactive center in the hybrid and (3) addition of bulk calf liver RNA did not affect the photocross‐linking efficiency.
FACILE CHARACTERIZATION OF THE SPECTRA OF cis AND trans PHOTOISOMERS IN A MIXTURE OF ACYL‐ENZYMES BY RAMAN DIFFERENCE SPECTROSCOPY
Authors: Doran John D. , Tonge Peter J. , Kim Munsok , Carey Paul R.
Published: January 2008

Abstract Raman difference spectroscopy is used to provide the spectra of both the cis and trans forms of acryloyl‐based acyl enzymes from a mixture without resorting to purification. A mixture of cis and trans, about the‐C=C‐C(=O) ethylenic linkage, is generated photochemically and by subtracting the Raman spectrum of the mixture from the spectrum of the pure trans form prior to photochemical irradiation, Raman peaks of the trans acyl‐enzyme appear as “negative” features and of the cis form appear as “positive” features. No operator intervention is required to scale the spectra for subtraction, and thus information on the relative Raman scattering efficiencies of the cis and trans isomers can be obtained immediately from the data. Results for 5‐methylthienylacryloyl chymotrypsin confirm earlier data for the purified cis and trans forms and data for cis indoleacryloyl chymotrypsin are presented for the first time.
MOLECULAR BASIS OF DRUG PHOTOTOXICITY: PHOTOSENSITIZED CELL DAMAGE BY THE MAJOR PHOTOPRODUCT OF TIAPROFENIC ACID
Authors: Castell Jose V. , Gomez‐Lechon Maria J. , Hernandez Daniel , Martinez Luis A. , Miranda Miguel A.
Published: January 2008

Abstract Tiaprofenic acid is a photosensitizing nonsteroidal anti‐inflammatory drug, whose major photoproduct (decarboxytiaprofenic acid) is also a potent photosensitizer. Because of the lack of the carboxylate moiety, this photoproduct is more lipophilic and might bind more efficiently to cell membranes, thereby causing phototoxic damage. To verify the feasibility of this hypothesis, we have prepared the 3H‐labeled analogs of tiaprofenic acid and its photoproduct and examined the binding, persistence and phototoxicity of the photoproduct using poorly metabolizing (fibroblasts) and actively metabolizing cells (hepatocytes). The photoproduct of tiaprofenic acid accumulates in both cell types as it is formed. Upon removal of the photoproduct from the culture medium, it rapidly disappears from hepatocytes but not from fibroblasts. Consequently, irradiation of fibroblasts previously incubated with the photoproduct and kept in culture in the dark for 20 h results in generalized cell damage while this effect is not observed in hepatocytes. Because of its long persistence in poorly metabolizing skin cells and its reluctance to photobleaching, the formation of this photoproduct in skin may be of relevance to explain the in vivo phototoxicity of tiaprofenic acid.
REPRODUCIBLE PREPARATION OF SILVER SOLS WITH UNIFORM PARTICLE SIZE FOR APPLICATION IN SURFACE‐ENHANCED RAMAN SPECTROSCOPY
Authors: Schneider Siegfried , Halbig Peter , Grau Harald , Nickel Ulrich
Published: January 2008

Abstract This paper describes a new method for the preparation of silver colloids with a narrow range of particle size to be used in surface‐enhanced Raman spectroscopy. Using malachite green as a strongly adsorbing dye, it can be shown that colloids from different preparation batches exhibit the same enhancement factor within an error margin of about 15%. By varying the number of nucleation centers, the particle size can be determined at will. An increase in particle diameter from about 38 to about 76 nm leads to an estimated five‐fold increase in surface enhancement.
MODEL FOR THE RATIONALIZATION OF MAGNETIC FIELD EFFECTS IN VIVO. APPLICATION OF THE RADICAL ‐ PAIR MECHANISM TO BIOLOGICAL SYSTEMS
Authors: Scaiano J. C. , Cozens Frances L. , McLean Jack
Published: January 2008

Abstract: :A model for magnetic field effects in biological systems is proposed. This model employs the basic concepts of the radical pair mechanism, and predicts that magnetic fields will increase the average radical concentration, lengthen their lifetime and enhance the probability of radical reactions with cellular components. The relevance of these effects in relation to cancer initiation, promotion and progression is discussed.
THE USE OF TETRAZOLIUM SALTS TO DETERMINE SITES OF DAMAGE TO THE MITOCHONDRIAL ELECTRON TRANSPORT CHAIN IN INTACT CELLS FOLLOWING in vitro PHOTODYNAMIC THERAPY WITH PHOTOFRIN II
Authors: Musser David A. , Oseroff Allan R.
Published: January 2008

Abstract A method is described utilizing the tetrazolium salts neotetrazolium chloride (NTC), triphenyltetrazolium chloride (TTC), C,N‐diphenyl‐N'‐4,5‐dimethylthiazol‐2‐yltetrazolium bromide (MTT) and various substrates to elucidate damage to the mitochondrial electron transport chain of intact cells following in vitro photodynamic therapy (PDT). Using this methodology, a portion of the dark toxicity manifested by Photofrin II (PII) was found to occur prior to entry of electrons into the transport chain through Complex I, as evidenced by the fact that the inhibition of MTT reduction was reversible by the addition of malic acid to the culture media. A second site of dark toxicity was found to be Complex IV (cytochrome oxidase). After photoirradiation of the cells, Complex I was found to be affected since malic acid could no longer reverse the inhibition of MTT reduction but it could be reversed by the addition of succinic acid, whose electrons enter the transport chain at Complex II. A second and more sensitive site of photoirradiation damage was found to be Complex IV. A region near cytochrome C was also affected by photoirradiation but appreciably less so than noted for Complexes I and IV. A kinetic analysis of MTT and TTC reduction following photoirradiation indicated that MTT reduction was sustained at a normal rate for 1 h after which it slowed down and eventually plateaued. In contrast, TTC reduction was found to be inhibited almost immediately indicating Complex IV is extremely susceptible to photoirradiation damage. Compared to other assays of mitochondrial function requiring subcellular fractionation, the use of tetrazolium salts is simpler to perform and can be done using physiologically relevant conditions.
CORRELATION OF UVC AND UVB CYTOTOXICITY WITH THE INDUCTION OF SPECIFIC PHOTOPRODUCTS IN T‐LYMPHOCYTES AND FIBROBLASTS FROM NORMAL HUMAN DONORS
Authors: Clingen Peter H. , Arlett Colin F. , Cole Jane , Waugh Alastair P. W. , Lowe Jillian E. , Harcourt Susan A. , Hermanova Nadezda , Roza Len , Mori Toshio , Nikaido Osamu , Green Michael H. L.
Published: January 2008

Abstract— By using specific monoclonal antibodies in situ and a computer‐assisted image analysis system we have determined the relative induction of cyclobutane dimers, (6–4) photoproducts and Dewar isomers in human mononuclear cells and fibroblasts following irradiation with UVC, broad‐spectrum UVB and narrow‐spectrum UVB. The lamps produced these lesions in different proportions, with broad‐spectrum UVB inducing a greater combined yield of (6–4) photoproducts and Dewar isomers per cyclobutane dimer than UVC or narrow‐spectrum UVB. The relative induction ratios of (6–4) photoproducts compared to cyclobutane dimers were 0.15, 0.21 and 0.10 following irradiation with UVC, broad‐ or narrow‐spectrum UVB, respectively. Although Dewar isomers were induced by UVC, their relative rate of formation compared to cyclobutane dimers was significantly greater after irradiation with either broad‐spectrum or narrow‐spectrum UVB. These values were 0.001, 0.07 and 0.07, respectively. With each lamp source, we have determined the survival of normal human T‐lymphocytes and fibroblasts at fiuences, which induce equivalent yields of cyclobutane dimers, (6–4) photoproducts or (6–4) photoproducts plus Dewar isomers. Killing of fibroblasts appears to be associated with (6–4) photoproduct formation, whereas killing of T‐lymphocytes seems to be mediated by combined (6–4) plus Dewar yields. These results emphasize the need to study the biological effects of UVB because cellular responses may be different from those following UVC irradiation.
THE EFFECT OF CHRONIC LOW‐DOSE UVB RADIATION ON LANGERHANS CELLS, SUNBURN CELLS, UROCANIC ACID ISOMERS, CONTACT HYPERSENSITIVITY and SERUM IMMUNOGLOBULINS IN MICE
Authors: El‐Ghorr Ali A. , Norval Mary , Lappin Michael B. , Crosby John C.
Published: January 2008

Abstract— C3H mice were irradiated three times a week for up to 6 weeks with either 500 J/m2 or 1000 J/m2 broadband UVB (270–350 nm) or 3000 J/m2 narrowband UVB (311–312 nm; TL01 source). Each dose was suberythemal to the mouse strain used. The number of Langerhans cells (LC) in the epidermis was reduced by over 50% after 2 weeks of irradiation with the UVB source and by 20% following TL01 irradiation. Continued irradiation for up to 6 weeks resulted in no further decrease in LC numbers in the case of the UVB source but a steady decline to 40% in the case of the TL01 source. Sunburn cells were detected following irradiation with both sources but the numbers were very low in comparison with acute exposure. Ultraviolet‐B exposure resulted in doubling of the thickness of the epidermis throughout the 6 weeks of irradiation while TL01 exposure did not alter epidermal thickness. Conversion of trans‐ to ew‐urocanic acid (UCA) was observed with both UVB and TL01 sources. The percentage of cis‐UCA started to return to normal after 4 weeks of TL01 exposure despite continued irradiation. As observed following a single exposure, the contact hypersensitivity (CH) response was significantly reduced following 6 weeks of UVB irradiation but was unaffected by TL01 exposure, indicating no correlation between cis‐UCA levels and CH response. Total serum immunoglobulin levels remained unchanged throughout the 6 weeks of UVB or TL01 irradiation but IgE titers significantly increased in all cases in the first 2 weeks of irradiation, indicating a possible shift to a TH2 cytokine profile. The IgE levels started to return to normal at later times. Thus chronic broadband UVB exposure induces a number of cutaneous and systemic responses that are likely to be dose dependent, while chronic TL0I exposure induces only some of the these responses.
In vivo EXCITATION OF PHOTOSENSITIZERS BY INFRARED LIGHT
Authors: Lenz P.
Published: January 2008

Abstract— Use of near infrared instead of visible light would markedly improve tissue penetration, making larger tumors candidates for photochemotherapy. Because common photosensitizers exhibit virtually no absorption in this wavelength region, conditions are required where the simultaneous action of two photons is possible. Healthy tissue (rat ears), sensitized by hematoporphyrin derivative, sulfonated chloroaluminum phthalocyanine or pheophorbide a, was irradiated (1064 nm, 10 ns) with power densities up to 200 MW cm‐2 and total energy densities up to 200 kJ cm‐2. No reproducible photodynamic lesions were observed, but there was sensitizer fluorescence that depended quadratically on the excitation intensity.