摘要:

Abstract—Formation of uracil and orotic acid photodimers, uridine and 5′‐UMP photohydrates, TpT photodimers and (6‐4)photoproducts, dCpT photohydrates and (6‐4)photo‐products and UpU, CpC and CpU photohydrates were studied in neutral deoxygenated aqueous solution at room temperature upon irradiation at either 193 or 254 nm. The photoproducts were identified and quantified and the contribution from photoionization to substrate decomposition, using λirr= 193 nm, was separated. The ratio of the quantum yields of respective stable products,η=φ193/φ254is indicative of the yield of internal conversion from the second to the first excited singlet state, S2→ S1. For the observed photodimers η decreases from 0.94 for uracil to 0.7 for TpT and further to 0.55 for orotic acid. For the (6‐4)photoproducts of TpT and dCpT T| = 0.5‐0.8 and for the photohydrates in the cases of UpU, CpC, CpU and dCpT TJ

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03006.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—The intensity dependence of the rose bengal (RB)‐photosensitized inhibition of red blood cell acetylcholinesterase has been studied experimentally and the results compared to a quantitative excitation/deactivation model of RB photochemistry. Red blood cell membrane suspensions containing 5 μMRB were irradiated with 532 nm, 8 ns laser pulses with energies between 1 and 98.5 mJ. A constant dose (7 J) was delivered to all samples by varying the total number of pulses. At incident energies greater than ∼ 4.5 mJ/pulse, the efficiency for photosensitized enzyme inhibition decreased as the energy/pulse increased. The generation of RB triplet state was monitored as a function of laser energy and the triplet‐triplet absorption coefficient was determined to be 1.9 × 104M−1cm−1at 530 nm. The number of singlet oxygen molecules produced at each intensity was calculated from both the physico‐mathematical model and from laser flash photolysis results. The results indicated that the photosensitized inhibition of acetylcholinesterase was exclusively mediated by singlet oxygen, even at the highest laser inten

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03007.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—The synthesis of some bromine‐substituted rhodamine derivativesviz., 4,5‐dibromorhodamine methyl ester (dye 2) and 4,5‐dibromorhodaminen‐butyl ester (dye 3) are reported. These dyes were synthesized to promote a more efficient cancer cell photosensitizer for potential use inin vitrobone marrow purging in preparation for autologous bone marrow transplantation. Spectroscopic and photo‐physical characterization of these dyes together with rhodamine 123 (dye 1) are reported in water, methanol, eth‐anol and also in a microheterogeneous system, sodium dodecyl sulfate. The possible mechanism of photosensi‐tization is characterized in terms of singlet oxygen efficiency of these dyes. Singlet oxygen quantum yields for bromine‐substituted dyes are in the range of 0.3‐0.5 depending on the solvent. For dye 1 no singlet oxygen production is found. The photodynamic actions of these dyes in different cell lines are tested. It was found that dye 2 and dye 3 are efficient photosensitizers and mediate eradication of K562, EM2, myeloid cell lines (CML) and the SMF‐AI

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03008.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—Near UV absorbance and fluorescence spectroscopy show conformational changes of a recombinant cutinase fromFusarium solaniincorporated in sodium‐di‐2‐ethylhexyl sulfosuccinate (AOT)‐iso‐octane reversed micelles with W0= [H2O]/[AOT]= 20. Excitation spectra were used to decompose cutinase absorbance in its Trp and Tyr components, showing that the latter absorb red‐shifted in the native cutinase in aqueous solution as compared to free Tyr, whereas in reverse micelles and denatured cutinase no shift is detected. Emission maxima variations (λmax303, 311 and 335 nm, respectively in aqueous, reverse micelles and thermally denatured cutinase) reflect progressive changes in the micropolarity of the environment and exposure of Trp residues at the protein surface. The encapsulation of cutinase in AOT‐iso‐octane reversed micelles induces a time‐dependent denaturation measured by fluorescence intensity changes at 330 nm, which match the profile of enzyme activit

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03009.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—In order to investigate the intramolecular “quenching” of the photoexcitation of some 5‐alkenyloxypsoralen derivatives, we have prepared model compounds in which a psoralen moiety was linked at position 5 to a terminal double bond via a polymethylenic chain of various length (n = 2‐9). The isolation and characterization of photocycloadducts obtained for each compound after irradiation at 365 nm in a polar solvent was performed. The results on the photoreactivity of this series of compounds show that the 3,4‐pyrone double bond of 5‐alkoxypsoralens is the most reactive. Four kinds of intramolecular photocycloadducts between the 3,4‐pyrone double bond and the chain unsaturation were obtained according to the length of the linking chain:cis‐syn, trans‐syn, cis‐antiandtrans‐anti.Their structures were established by a combination of1H and13C NMR and fully assigned bylH NOE (nuclear Overhauser effect) and1H‐13C HMQC (heteronuclear multiquantum correlation) spectroscopies. No traces of 4

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03010.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—The singlet and triplet excited state parameters (φf, Tfand SpHT) of psoralen (PSO) and derivatives 4,6,4′‐trimeth‐ylangelicin (TMA) and 4,5′,8‐trimethylpsoralen (TMP) show an extreme sensitivity to solvation in dioxane/water mixtures. These effects are attributed to the variation of the Si → S0internal conversion rate constantkic, which is the nonradiative deactivation path dominating their photophysical behavior. Depending on the compound,kicis very high, (∼1 times 1010s_1) in nonpolar solvents and then decreases to a low value (3 times 108s−1) with increasing solvent polarity. This work shows that dioxane/water mixtures display the same solvent‐induced changes in the electronic structure of psoralens during solvation as those induced by the biological microenvironment sensed by the drug's localization. This mixture matches the photophysical parameters of psoralens observed in protic and aprotic pure solvents, in micelles, in liposomes and in human serum low‐density lipoproteins (LDL). They can be used to probe the solvating ability of the interaction site in macrocyclic hosts. A particular localization site,i.e.the more (TMA and TMP) or less (PSO) lipophilic sites found when in interaction with LDL, determines the amount of the triplet reactive state of psoralens and the molecular mechanism available for photoreac‐tion: oxic (type I and type II) or an

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03011.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—Replication continues in wild‐type (but notradmutant)Caenorhabditis elegansembryos even after exposure to massive fluences of UV radiation. It is of interest to elucidate the mechanism(s) for this “damage‐resistant” DNA synthesis. In this study, DNA from unirradiated and UV‐irradiated wild‐type embryos was examined using the electron microscope. Large fluences of UV radiation (180 J m−2) had little effect on either replication bubble size or distances between bubbles in wild‐type embryos, indicating that the damage‐resistant DNA synthesis was not grossly aberrant. Conversely, UV irradiation significantly decreased center‐to‐center distances between bubbles in excision‐repair‐deficientrad‐3embryos. This suggests that the decreased DNA synthesis observed after UV irradiation inrad‐3embryos is due largely to blockage

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03012.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—The transmittance of cloudiness was examined for the daily totals of global erythemal effective irradiance and global total irradiance in Innsbruck (577 m above sea level [a.s.l.], Western Austria) for the periods 1981‐1988 and 1993‐1994 and at Jungfraujoch (3576 m a.s.l., Switzerland) for the period 1981‐1990. The influence of varying cloudiness on the daily totals of global erythemal effective irradiance is considerably greater than the influence of varying ozone. The lowest transmittance for daily totals of global erythemal effective irradiance is 9.4% in Innsbruck (577 m a.s.l.) and 23.5% at Jungfraujoch (3576 m a.s.l.); the median and the 25‐75 percentile range at 10/10 cloudiness are 41.8% (28.9‐56.7%) and 76.8% (63.5‐86.1%), respectively. The greater transmittance of global erythemal effective irradiance at Jungfraujoch originates from smaller thickness of the cloud layer in high mountains than in valleys. Similar transmittances were obtained for the daily totals of global total irradiance (300‐3000 nm) as a functio

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03013.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—Resonance‐enhanced coherent anti‐Stokes Raman (CARS) spectra are reported for trimers of phycoerthrocyanin (PEC) dissolved in H2O and D2O. The CARS spectra are significantly different when recorded with pump wavelength either at 585 nm or 630 nm. By comparison of the 630 nm spectra with those of phycocyanin one can conclude that there is a change in the relative location of the lowest excited states of the β84 and β155 chromophores. Upon additional illumination with 514.5 nm laser light, only the spectra recorded with 585 nm pump wavelength change. This is in accordance with earlier observations that the phycoviolobilin chromophore of the a‐subunit exhibits photochromic behavior. The changes in the CARS spectra provide evidence that it is the methine bridge between rings C and D that undergoes the geometrical changes. Furthermore, it is suggested that there are different types of photoinduced rearrangements operative and that the isomeric distribution is different in H2

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03014.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—Light‐activated psoralens can covalently modify DNA and are widely used to study nucleic acid secondary structure and mutagenesis. Sequence specificity can be added to the photoaddition reaction by attaching the psoralen to an oligonucleotide designed to recognize a double‐stranded DNA binding site through formation of a triple helix. We have previously used this strategy to study targeted psoralen modification of a triplex binding site within the bacterialsupFgene carried in viral genomes. In the present work we report the targeting of psoralen photoadductsin vitroto a specific site in the genome of a transgenic mouse. Both 10 base and 16 base oligonucleotide‐psoralen conjugates were capable of sequence‐specific modification of genomic mouse DNA, while a truncated 8 base conjugate was not. Light activation was necessary, and a dose dependence was demonstrated for target site modification and mutagenesis. The 10 base conjugate rapidly found its target, with sequence‐specific binding occurring after just 10 min incubation in the presence of mouse DNA. The ability to target psoralen photoadducts within mammalian genomes may prove useful in the study of chromatin structure and DNA repair. Moreover, this work may lead to potentialin vivoapplications of targeted psoralen m

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb03015.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY