摘要:

AbstractThe binding of the tetrapeptide lysyl‐tryptophyl‐glycyl‐lysinet‐butyl ester to native DNA and DNA photochemically modified by 5‐methoxypsoralen has been investigated by fluorescence spectroscopy. The peptide exhibits a higher affinity for the modified DNA than for the undamaged DNA. This is due to the presence of strong stacking sites in the vicinity of 5‐methoxypsoralen monoadducts. Upon irradiation at 365 nm of the peptide‐modified DNA complexes, a cross‐linking of the peptide to the nucleic acid is observed. This photochemical addition requires the presence of oxygen and involves, in part,

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04689.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractUV‐vis absorption and fluorescence spectroscopy were used to show that in alcoholic solutions (methanol, ethanol, 2‐methylbutan‐1‐ol, and 2‐octanol) concentration, temperature, and sonication affect the relative populations of the more rigid stretched and the more flexible helically coiled conformers of biliverdin dimethyl ester. In aromatic solvents, e.g. toluene, no such effects could be detected. At concentrations larger than 3 10‐5Min the alcoholic solvents aggregates and monomeric coiled species prevail. Upon dilution, the fraction of stretched monomeric conformers increases. Heating and sonication at concentrations smaller than 3 10‐5Mfurther and irreversibly increase the fraction of the stretched conformers. The activation parameters for this change are compatible with the assessment that no equilibrium is attained between the two families of conformers even after several hours at room temperature, since the barriers arc higher thankTat this temperature. The present results and those previously reported on the excited‐state processes of biliverdin dimethyl esters are explained on the basis of a scheme in which the eight possible ring B/C isomers of biliverdin dimethyl ester are interconverted through intra‐and intermolecular proton transfers, rotations around C‐C single bonds, andE‐Zphotoisomerizations arou

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04690.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe photochemistry of α‐terthienyl (αT) and its mono‐ and dodo derivatives has been examined using nanosecond laser Hash photolysis techniques. The triplet states of these intermediates have been characterized, and show strong triplet‐triplet absorptions with maxima in the 450 to 490 nm region. The triplet lifetimes are normally reduced by efficient triplet‐triplet annihilation and self‐quenching both of which approach diffusion control. Triplet lifetimes in methanol obtained by extrapolation to zero laser dose and zero concentration are 30, 12.5 and 9.4 μs for αT and its mono‐ and dodo derivatives, respectively; the effect of iodo substitution on the lifetimes is attributed to heavy atom effects. The triplet states are efficiently quenched by oxygen and the electron acceptor methyl viologen, while amines tire very poor triplet quenchers. The iodo derivatives are photolabile. undergoing C‐I bond cleavage from the singlet state, a process that was studied in benzene solvent, where the complex between iodine atoms and benzene can be readily characterized.Modification of αT by replacement of the central thiophene ring by an aromatic ring (i.e. DTB) causes drastic changes in the triplet and singlet state kinetic and spectroscop

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04691.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractEncapsulating a xanthene dye in phospholipid vesicles produces vesicle solutions that contain dye at very high microscopic concentrations, but have a low overall optical density, thereby eliminating reabsorption. Using this system, we have studied the effects of concentration on the fluorescence lifetime of one such dye, sulforhodamine 101. We have observed that the lifetime decreases as a function of encapsulated dye concentration, which is indicative of collisional quenching. The lifetime decreases from 4.5 nsec for sulforhodamine in dilute aqueous solution to 0.69 ns at an encapsulated concentration of 33 mM. The bimolecular rate constant for this event is 2.6 1010M‐1s‐1, consistent with a diffusion controlled event. However, the quenching constant calculated from changes in intensity is 2.2 1011M‐1s‐1. Thus, collisional quenching is not the predominant mechanism of quenching. The absorption spectra of dye in vesicles indicate an important contribution from static complex formation. Förster distance calculations indicate that energy transfer can also occur to a significant extent, with a predicted efficiency of transfer of 34% at a dye concentration of

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04692.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractMicrospectrofluorometry on single living cells reveals that the primary effects of porphyrin‐photosensitization on membranes results in the production of fluorescent lipofuscin‐like pigments implying important lipid photoperoxidation. These fluorescent products (max450 nm) can also be formed in the dark after the irradiation of the cell. Their formation is abolished not only by crocetin and Tigason, two long‐chain polyenes, but also by chloroquine. The latter, although a lysosomotropic drug, cannot inhibit the photosensitized permeation of lysosomal membranes which occurs at the beginning of the irradiation as shown by the splitting of fluorogenic substrates by lysosomal proteinases or by β‐galactosidase when added before or after irr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04693.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe transient change in the NAD(P)H NAD(P) equilibrium following microinjection of mitochondrial (malate) or extra‐mitochondrial (6‐phosphogluconate) substrates into single living cells is strongly modified a few seconds after the onset of 365 nm irradiation in the presence of hematoporphyrin. There is no major difference in the time frame for the alterations of the Krebs cycle and pentose pathway. In view of the complex interrelationships between mitochondrial and extramitochondrial pathways, there is a reasonable chance that effects on both pathways are not unrelated‐ However there is no definite evidence for a direct correlation between the photoeffects on these two pat

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04694.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe naturally occurring thiophene, α‐terthienyl, was investigated for phototoxicity against several viruses and a line of mouse cells. The compound was extremely phototoxic to the two‐membrane‐containing animal viruses, murine cytomegalovirus (MCMV) and Sindbis virus (SV). Antiviral activity was detected at 105μg/m in the presence of UVA. However, no effect was seen in the absence of UV‐A, even at 0.1 μg/m of αT. Mouse cells were much more resistant to αT, as was the bacterial virus T4, which does not contain a membrane. Murine CMV, which had been inactivated by αT and UVA, penetrated mouse cells efficiently; but the viral DNA could not replicate, and late viral proteins were not made. Thus viral gene expression was inhibited in the photoinactivated virus. In order to account for all these data we suggest that αT may interact with viral proteins in addition to m

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04695.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe UV‐A mediated antiviral effect of harmine was investigated using murine cytomegalovirus (MCMV) as the target. Virus, which had been inactivated by harmine + UVA, was used to infect cultured mouse cells, and various stages in the viral replication cycle were examined. No viral protein synthesis or RNA synthesis (as measured by polyacrylamide gel electrophoresis or DNA‐RNA hybridization) could be detected, and the viral DNA did not replicate (measured by DNA‐DNA hybridization). In contrast virus which had been treated with harmine in the dark promoted a complete growth cycle in mouse cells.An attempt was made to identify the primary target of harmine + UVA activity by examining the bacteriophages T4 and M13, which unlike MCMV do not possess membranes. Both bacteriophages were sensitive, but the single‐stranded DNA phage M13 was considerably more so. These results, together with others discussed in the text, suggest that DNA and possibly other macromolecules can serve as targets for harmine photoa

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04696.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractLeukemia L1210 cells were incubatedin vitrowith the tumor‐localizing product HPD (hem‐atoporphyrin derivative) for 0.5. 4 and 18 h. Effects of subsequent irradiation on viability, membrane transport and integrity, DNA synthesis and intracellular ATP concentration were assessed. Intracellular porphyrin pools were analyzed by HPLC. A 30 min incubation led to concentration of a readily‐exchangeable pool of monomeric HPD components at plasma membrane loci; irradiation resulted in photodamage to membrane transport and a loss in capacity for dye exclusion. In contrast, increasing the incubation time led to a corresponding increase in the size of a non‐exchangeable intracellular pool of other HPD components. Subsequent irradiation led to depletion of intracellular ATP and loss of capacity for biosynthesis of DNA, but little plasma membrane

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04697.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractEosin‐isothiocyanate (EYNCS) is 50 to 100 times more effective in sensitizing delayed photo‐hemolysis of human erythrocytes than is eosin when matched for absorbance in the reaction medium. These dyes are equally efficient in generating singlet oxygen, a potent membrane oxidant. When cells are treated with sensitizer and washed extensively prior to illumination, EYNCS phototoxicity persists, while that of eosin is lost. SDS‐gel electrophoresis of membranes from EYNCS‐exposed cells shows a large fluorescence signal coincident with band 3 protein that is abolished by pretreatment with H2DIDS, the inhibitor of anion exchange by band 3. This treatment reduces the photohemolytic potency of EYNCS by over 90%. The marked enhancement of photohemolytic activity upon binding sensitizer to band 3 implicates band 3 itself as a site of photodamage leading t

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04698.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY