bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE ORIENTATION OF THE TRANSITION DIPOLE MOMENTS OF CHLOROPHYLLaand PHEOPHYTIN a IN THEIR MOLECULAR FRAME
Authors: Zandvoort M. A. M. J. van , Wróbel D. , Lettinga P. , Ginkel G.van , Levine Y. K. 
Published: January 2008

Abstract—In this paper we describe the determination of the orientation of the absorption and emission transition dipoles of chlorophyllaand pheophytinain their molecular frame. For this purpose we have embedded the pigments in anhydrous nitrocellulose films with a concentration of 2 × 10‐7mol/g. We have shown previously that under these conditions the pigments are in a purely monomeric state, are distributed uniformly both before and after stretching and that no intermolecular energy transfer among the molecules takes place.Using a combination of steady‐state anisotropy experiments on unstretched films and angle‐resolved fluorescence depolarization measurements on stretched films, we obtain the orientation of the transition dipole moments of both pigments in their molecular frame and the orientational distribution function of the molecules relative to the stretching direction of the film.The steady‐state anisotropy measurements indicate that chlorophyllahas two distinct emission dipole moments and that excitation in the Soret‐region results in simultaneous excitation of two or more absorption transition dipole moments. On the other hand, excitation in the QY‐band involves only a single dipole moment. The directions of the transition dipole moments in the molecular frame are obtained from the angle‐resolved measurements. Pheophytinaalso exhibits two emission dipole moments, but the angle between them is much smaller than that between the corresponding dipoles for chlorophylla. As a consequence the dipole moments contributing to the Soret‐region could not be resolved and only an effective absorption transition dipole moment in the Soret‐region is extracted.
Mechanism of UVB‐Induced Suppression of the Immune Response to Mycobacterium bovis Bacillus Calmette‐Guerin: Role of Cytokines on Macrophage Function
Authors: Jeevan Amminikutty , Ullrich Stephen E. , Gracia Maria De , Shah Rupa , Sun Yan 
Published: January 2008

AbstractPreviously we demonstrated that treatment of mice with either UVB radiation or supernatants derived from UVB‐irradiated PAM 212 keratinocytes decreased the induction of the delayed‐type hypersensitivity (DTH) response to Mycobacterium bovis bacillus Calmette‐Guerin (BCG), impaired the clearance of bacteria from their lymphoid organs and also altered macrophage functions. In order to characterize the cytokines involved in these phenomena, UV‐irradiated mice were injected with antibodies to interleukin‐10 (IL‐10), transforming growth factor‐β1 (TGF‐β1), or tumor necrosis factor‐α (TNF‐α). Injection of UVB‐irradiated mice with anti‐IL‐10 immediately after UV irradiation restored the DTH response and reversed the UV‐induced inhibition of bacterial clearance. Injection of UV‐irradiated mice with anti‐TGF‐β only partially restored the DTH response although it allowed a better clearance of BCG than injection of mice with the control antibody. In contrast, injection of anti‐TNF‐α did not affect the UVB‐induced suppression of DTH or impaired bacterial clearance. Similarly, the ability of macrophages to phagocytose BCG and kill the intracellular organisms was restored to almost normal levels after injecting UV‐irradiated mice with antibodies specific for IL‐10 or TGF‐β. Injection of mice with either recombinant IL‐10 or TGF‐β mimicked the effect of whole‐body UV irradiation on immune function. These results suggest that IL‐10 has a major role in UV‐induced suppression of both DTH to BCG and impairment in the clearance of bacteria and that TGF‐β has a more significant role in blocking bacterial clearance. Furthermore, these cytokines seem to modulate immune responses by altering macrophage functions in UVB‐irradiated mice.
Spectroscopic and Biological Testing of Photobleaching of Porphyrins in Solutions*
Authors: Bezdetnaya L. , Zeghari N. , Belitchenko I. , Barberl‐Heyob M. , Merlin J. ‐L. , Potapenko A. , Gulllemin F. 
Published: January 2008

AbstractThe photobleaching of protoporphyrin IX (PP IX) and hematoporphyrin derivative (HpD) solutions was followed using three different methods: spectrophotometry, fluorometry and photodynamically induced cytotoxicity. The latter entails photoirradiation of HT29 human colon adenocarcinoma cells in the presence of preirradiated solutions of HpD and PP IX (λ 415 nm). The highest cytotoxicity was observed in the presence of unirradiated dye and decreased with the time of preirradiation. This decay in photocytotoxicity was further used to determine the porphyrin photobleaching kinetics in solution. For both sensitizers, quantum yields of photobleaching obtained by matching fluoresence were higher than that obtained from absorbance measurements (10 and 11 times for HpD and PP IX, respectively). This difference reflects preferential photobleaching of photolabile monomeric forms compared to aggregates. The highest quantum yield was obtained in the biological test (decay in cytotoxicity) which was 14 times higher for HpD and 30 times higher for PP IX than the quantum yield obtained from absorbance measurements. The absence of correlation between biological and fluorescence measurements has to be taken into account in the in vivo situation. Dark storage of preirradiated sensitizers (37°C, 24 h) completely restored photocytotoxity for PP IX but only partially for HpD, whereas fluorescence patterns were partially restored for both sensitizers.
Structure and Biodistribution Relationships of Photodynamic Sensitizers*
Authors: Boyle Ross W. , Dolphin David 
Published: January 2008

Abstract— Photodynamic therapy (PDT) has, during the last quarter century, developed into a fully fledged biomedical field with its own association, the International Photodynamic Association (IPA) and regular conferences devoted solely to this topic. Recent approval of the first PDT sensitizer, Photofrin® (porfimer sodium), by health boards in Canada, Japan, the Netherlands and United States for use against certain types of solid tumors represents, perhaps, the single most significant indicator of the progress of PDT from a laboratory research concept to clinical reality.The approval of Photofrin® will undoubtedly encourage the accelerated development of second‐generation photo‐sensitizers, which have recently been the subject of intense study. Many of these second‐generation drugs show significant differences, when compared to Photofrin®, in terms of treatment times postinjection, light doses and drug doses required for optimal results. These differences can ultimately be attributed to variations in either the quantum efficiency of the photosensitizer in situ, which is in turn affected by aggregation state, localized concentration of endogenous quenchers and primary photophysics of the dye, or the intratumoral and intracellular localization of the photosensitizer at the time of activation with light. The purpose of this review is to bring together data relating to the biodistribution and pharmacokinetics of second‐generation sensitizers and attempt to correlate this with structural and electronic features of these molecules. As this requires a clear knowledge of photosensitizer structure, only chemically well‐characterized compounds are included, e.g. Photofrin® and crude sulfonated phthal‐ocyanines have been excluded as they are known to be complex mixtures. Nonporphyrin‐based photosensitizers, e.g. rose bengal and the hypericins, have also been omitted to allow meaningful comparisons to be made between different compounds. As the intracellular distribution of photosensitizers to organelles and other subcellular structures can have a large effect on PDT efficacy, a section will be devoted to this topic.
Effects of Ultraviolet‐B Exposure on the Resistance to Listeria monocytogenes in the Rat
Authors: Goettsch Wim , Garssen Johan , De Klerk Arja , Herremans Tineke M. P. T. , Dortant Paul , De Gruijl Frank R. , Van Loveren Henk 
Published: January 2008

ABSTRACTA rat infection model using the bacterial pathogen Listeria monocytogenes was employed to analyze the im‐munosuppressive activity of UVB radiation. Rats were exposed to suberythemal doses of UVB radiation for 5 or 7 consecutive days, using Kromayer or FS40 lamps respectively. Subsequently, the rats were infected subcuta‐neously or intravenously with Listeria. Exposure to UVB resulted in an increased number of bacteria in the spleen 4 days after infection. Listeria‐specific lymphocyte proliferation assays as well as delayed‐type hypersensitivity reactions demonstrated that T cell‐mediated immunity to Listeria was impaired by UVB as measured 4 and 8 days after infection. In addition, UVB exposure decreased phagocytotic activity of peripheral blood macrophages. This study demonstrated that suberythemal doses of UVB radiation caused a delay in the clearance of Listeria bacteria from the spleen of the rats and that this was probably caused by impaired nonspecific phagocytosis of Listeria by macrophages in addition to an impaired activity of Listeria‐specific T cells.
Melanocyte‐stimulating Properties of Secretory Phospholipase A2
Authors: Maeda Kazuhisa , Naganuma Masako 
Published: January 2008

Abstract— Phospholipase A2 (PLA2) catalyzes the release of free fatty acids from membrane phospholipids, and its products derived from these fatty acids, such as prostaglandins and leukotrienes, significantly up‐regulate the key mela‐nogenic enzyme, tyrosinase, in melanocytes. This has led to suggestions that PLA2 itself triggers melanin synthesis in melanogenesis following UV irradiation or inflammation.We have examined the effect of secretory PLA2 (sPLA2) on melanogenesis in cultured human melanocytes. Secretory PLA2 stimulated DNA synthesis and melanin synthesis, and these phenomena were completely inhibited by treatment with a phospholipase inhibitor, p‐bromophenacyl bromide, demonstrating that the catalytic activity of sPLA2 is required for melanogenesis. Secretory PLA2 also stimulated tyrosinase activity, increased the amount of tyrosinase‐related protein‐1 and up‐regulated the expression of both mRNA. These findings suggest that sPLA2 is an important mediator of UV‐induced or postinflammatory pigmentation.
Ultraviolet Radiation in a High Mountain Lake of the Austrian Alps: Air and Underwater Measurements
Authors: Sommaruga Ruben , Psenner Roland 
Published: January 2008

ABSTRACTGlobal UV radiation was measured with a portable multichannel filter radiometer at the surface and underwater in a high mountain lake (2417 m above sea level) of the Austrian Alps during 16 days in summer 1995. During this period, total column ozone values that changed only by 34 Dobson units explained a significant part of the variability in UVB radiation at 305 nm as indicated by the negative correlation with the ratio 305:340 nm (rs= ‐0.810, P < 0.01). High radiation at the surface combined with high water transparency allowed substantial UVB radiation to reach the bottom of this lake. The diffuse attenuation coefficient for downward irradiance at 305 nm changed within 2 weeks from 0.24 m‐1 (10% at 9.6 m depth) to 0.32 m‐1 (10% at 7.2 m depth). This change in attenuation was related to the development of phytoplankton after the ice break‐up as indicated by a six‐fold increase in chlorophyll‐a concentrations during this period. Our results suggest that phytoplankton and/ or phytoplankton‐derived organic substances are important for the UV attenuation in this oligotrophic lake.
Effect of Dosimetric and Physiological Factors on the Lethal Photosensitization of Porphyromonas gingivalis in vitro
Authors: Bhatti Manpreet , MacRobert Alexander , Meghji Sajeda , Henderson Brian , Wilson Michael 
Published: January 2008

ABSTRACTThe aims of this study were to (1) determine the effect of dosimetric and physiological factors on the lethal photosensitization of Porphyromonas gingivalis using tolui‐dine blue O (TBO) and light from a helium/neon (HeNe) laser; (2) determine the influence of sensitizer concentration, preirradiation time, serum and growth phase on sensitizer uptake by P. gingivalis. The dosimetric factors studied were concentration of TBO, light dose and preirradiation time. The physiological factors were presence of serum, pH and bacterial growth phase. Sensitizer uptake by P. gingivalis under various conditions was determined using tritiated TBO (3H‐TBO). In the presence of TBO, a light dose‐dependent increase in kill was attained (100% kill at 4.4 J). There was no significant effect on the numbers killed when TBO was increased from 12.5 to 50 µg/mL. An increase in preirradiation time gave slightly increased kills. High kills were achieved at all three pH (6.8–8.0). Although kills were substantial in the presence of serum, they were significantly less than those obtained in the presence of saline. Cells in all three growth phases were susceptible to lethal photosensitization, although stationary phase cells were slightly less susceptible. Maximum uptake of TBO occurred within 60 s and uptake in serum was less than in saline. The uptake by the log phase cells was greater at lower concentrations of sensitizer (50 µg/mL), compared to the other two phases.
Ultrasonic Modulation of Scattered Light in Turbid Media and a Potential Novel Tomography in Biomedicine
Authors: Wang Lihong V. 
Published: January 2008

ABSTRACTUltrasonic modulation of scattered laser light was used to image objects buried in tissue‐simulating turbid media. The ultrasonic wave focused into the turbid media modulated the laser light passing through the ultrasonic field. The modulated laser light collected by a photomultiplier tube reflected primarily the local mechanical and optical properties in the zone of ultrasonic modulation. A raster scanning over a heterogeneous turbid medium yielded an image of the medium based on the ultrasound‐modulated optical signal. The detectability of modulated signal was estimated using diffusion theory. The dependence of the modulated signal on the off‐axis distance of the detector from the optic axis and on the amplitude of ultrasound was studied. The mechanisms of ultrasonic modulation of scattered light are discussed. A theory based on the field autocorrelation function is reviewed as well.
Potential Mechanisms of Photodynamic Inactivation of Virus by Methylene Blue I. RNA–Protein Crosslinks and Other Oxidative Lesions in Qβ Bacteriophage
Authors: Schneider J. Edward , Tabatabaie Tahereh , Maidt Lindsay , Smith Renee Horning , Nguyen Xuan , Pye Quentin , Floyd Robert A. 
Published: January 2008

ABSTRACTA spectrum of oxidative lesions was observed in a bacteriophage‐based model system that is very sensitive to the photodynamic activity of selected dyes. When suspensions of the intact bacteriophage Qβ were exposed to methylene blue plus light (MB+L), inactivating events, or "hits" occurred that were oxygen‐dependent and that were associated with the formation of several specific lesions: (1) carbonyl moieties on proteins, (2) 8‐oxo‐7,8‐dihydroguanine (8‐oxoGua), and (3) single‐strand breaks (ssb) in the RNA genome and (4) RNA‐protein crosslinks. Formation of carbonyl groups associated with protein in the Qβ phage preparation correlated positively with photoinactivation of the phage with increasing doses of either of the sensitizers MB or rose bengal. Strand breaks in the Qβ genomic RNA were observable at high MB concentrations but appeared not to be significant at the lower concentrations of MB, as full‐length Qβ RNA was observable well beyond the 99% inactivation point in MB dosage. It was shown that the number of 8‐oxoGua lesions were unlikely to be sufficient to account for the number of lethal events. Following exposure to MB+L, crosslink formation between Qβ RNA and protein was observed by virtue of the location of RNA at the interface of phenol‐aqueous extractions of phage suspensions. A significant increase over background of RNA‐protein complexes (including full‐length Qβ RNA) was observed at the lowest concentration of MB tested (0.5 μM), which corresponded roughly to an average of 2 lethal hits per phage or approximately 13% survival compared to the zero MB control (100% survival). Due to its close correlation with Qβ inactivation and its expected lethality, RNA‐protein crosslink formation may be important as an inactivating lesion in bacteriophage Qβ following MB+L exposure.
The Effect of Fluence Rate on Tumor and Normal Tissue Responses to Photodynamic Therapy
Authors: Sitnik Theresa M. , Henderson Barbara W. 
Published: January 2008

ABSTRACTPhotodynamic therapy (PDT), carried out at low fluence rates, may enhance tumor response as well as affect treatment selectivity. We have studied the effects of fluence rate on the response of the murine radiation‐induced fibrosarcoma (RIF) to PDT using Photofrin® (5 mg/kg). Tumor response was tested over a large range of fluence rates (10‐200 mW/cm2) and fluences (25‐378 J/ cm2). Low fluence rates were more efficient; ‐60 J/cm2 at 10 mW/cm2 was needed to achieve the same tumor growth delay as ‐100 J/cm2 at 150 mW/cm2 and ‐150 J/cm2 at 200 mW/cm2. Despite this increased efficiency, lower fluence rates still required longer treatment times for equivalent anti‐tumor effects: 95 min for 57 J/cm2 at 10 mW/cm2versus 11 min for 100 J/cm2 at 150 mW/cm2. Effects of fluence rate on the PDT toxicity to normal tissue were examined through the response of the murine (C311) foot to Photofrin® PDT. Treatment with conditions that produced equivalent tumor responses, i.e. 57 J/cm2 at 10 mW/cm2 and 100 J/cm2 at 150 mW/cm2, resulted in a more severe foot response at the higher fluence rate (median peak response: 0.9 at 10 mW/cm2, 1.5 at 150 mW/cm2) with more time required for tissue to return to normal (8 days at 10 mW/cm2, at least 30 days at 150 mW/cm2). However, when feet were treated with an equal fluence of 100 J/cm2 at various fluence rates, longer healing times accompanied the lower fluence rate treatments. Overall, this paper demonstrates that lower PDT fluence rates are associated with increased efficiency of tumor response. If this increased efficiency is accounted for by lowering treatment fluence, lower fluence rates also may result in a more favorable normal tissue response to treatment.
Further Characterization of UVB Radiation Effects on Langerhans Cells: Altered Expression of the Costimulatory Molecules B7‐1 and B7‐2
Authors: Denfeld Ralf W. , Tesmann Jens P. , Dittmar Henning , Weiss Johannes M. , Schöpf Erwin , Weltzien Hans U. , Simon Jan C. 
Published: January 2008

ABSTRACTWe have reported previously that low‐dose UVB radiation (UVBR, 50‐200 J/m2) perturbs the antigen‐presenting cell (APC) function of murine Langerhans cells (LC) by interfering with yet undefined costimulatory signals. In this study, we investigated (1) the effects of UVBR on the expression of the costimulatory molecules B7‐1 and B7‐2 on murine LC, (2) the functional consequences of defective B7‐1 and B7‐2 signalling on primary and secondary T‐cell responses induced by LC and (3) the mechanism by which UVBR interferes with B7‐1 and B7‐2 expression. Ultraviolet‐B radiation dose‐dependently inhibited the culture‐induced upregulation of B7‐1 and B7‐2 on LC from both UVB‐susceptible (UVBs, C57BL/6) and UVB‐resistant (UVBR, Balb/c) mice and abrogated their capacity to stimulate proliferation of naive alloreactive T cells and of the KLH (keyhole limpet hemocyanin)‐specific T helper (Th)1 clone HDK‐1. The UVBR‐induced suppression of B7‐1 and B7‐2 on LC and their perturbed APC function were related, because exogenous triggering of the B7/CD28 pathway with a stimulatory monoclonal antibody (mAb) for CD28 to UVB‐irradiated LC partially restored T‐cell proliferation. Such reconstitution was not observed when the mAb was added to killed LC, indicating that the UVBR‐induced suppression of APC function was not due to lethal effects on LC. Conditioned supernatants from UVB‐irradiated epidermal cells did not inhibit the functional upregulation of B7‐1 and B7‐2, suggesting that UVBR inhibits B7‐1 and B7‐2 upregulation by acting directly on LC and not by altering LC costimulatory function via release of soluble immunosuppressive factors. In conclusion, UVBR distorts the functional expression of B7‐1 and B7‐2 on LC from both UVBs and UVBR mice, thereby contributing to the failure of UVB‐irradiated LC to stimulate resting alloreactive T cells or KLH‐specific Thl cells.
Photogeneration of Hydrated Electrons, Nitrogen‐Centered Radicals and Singlet Oxygen from Naphazoline: A Laser Flash Photolysis Study
Authors: Sortino S. , Scaiano J. C. 
Published: January 2008

AbstractThe transient intermediates involved in the photochemistry of naphazoline (NP, 2‐[1‐naphthylme‐thyl]imidazoline) have been examined using laser flash photolysis techniques. The photoreactivity of the drug is characterized by a photoionization process occurring through a mixture of mono‐ and biphotonic pathways. An intramolecular electron transfer involving both the imidazoline and the naphthalene moieties leads to the formation of nitrogen‐centered radicals. The generation of singlet oxygen from the lowest excited triplet state of NP is also observed. The results obtained demonstrate the potential for NP to act as a both a type I and type II photosensitizer.
The Temperature Dependence of Protoporphyrin IX Production in Cells and Tissues
Authors: Moan Johan , Berg Kristian , Gadmar Øystein B. , Iani Vladimir , Ma LiWei , Juzenas Petras 
Published: January 2008

AbstractThe formation of protoporphyrin IX (PpIX) in human skin during topical application of 5‐aminolevulinic acid (ALA) was found to be strongly temperature dependent, with an activation energy of about 17 kcal/mol. This temperature dependence is mainly related to porphyrin production and not to ALA penetration into the skin. The penetration of ALA into mouse and human skin was almost temperature independent. The activation energy of PpIX production in mouse skin was practically identical with that in human skin. The activation energy of ALA uptake by cells in vitro was about 10 kcal/mol and that for PpIX production was about 13 kcal/mol. The latter activation energy was within the error limits similar to that for the activity of the enzyme porphobilinogen deaminase, suggesting that this enzyme might represent a rate‐limiting step for PpIX production in living tissue.
Color Tuning Mechanism of Human Red and Green Visual Pigments
Authors: Kakitani Toshiaki , Beppu Yoshitaka , Yamada Atsushi 
Published: January 2008

AbstractWe investigated the molecular mechanism of a rather large red shift of 31 nm in a human red pigment compared with a human green pigment. In this analysis, we paid special attention to the phenomenon of nonadditivity of spectral shifts due to substitution of the key amino acids (OH‐bearing amino acids) and the phenomenon of cooperativity by which the spectral shifts due to substitution of the key amino acids in the protein environment of red pigment are about 1.5 times larger than that in the protein environment of green pigment. The analysis was made by using a model of three active sites on which the key amino acids are located and four effective sites by which the effect of the key amino acids is modified. As a result, we found that the interaction between the active sites that occurs through the repolarization of the chromophore induced by the key amino acid is essential for the nonadditivity phenomenon. We also found that the interaction between the active site and the effective site plays a major role in the cooperativity phenomenon. More directly, we say that the highly polarizable property of the chromophore is the origin of the rather large red shift in red pigment. Based on these analyses, we conclude that the interaction between the polarizable chromophore and the protein moiety has the capability of producing a significant spectral shift, at least 1000 cm1, even by substitution of moderate polar residues of the OH‐bearing amino acids.