摘要:

Abstract—The photodestruction of purine free base used as a model for the purine bases in DNA has been studied in order to better understand the effect of UV light on these molecules. Photodestruction yields have been determined in glassy aqueous solutions at 77 K and at room temperature at different pH's. The yield decreases in the order of 0.04, 0.01, 0.001 in 8MNaOH, 8MNaCIO4and 6MH3PO4, respectively, while at room temperature the highest destruction yield is 0.005 for the unbuffered neutral solution. These yields have been determined by measuring the initial decrease in the purine absorption maximum as a function of irradiation time. During the illumination stable photoproducts, as well as reactive intermediates, such as trapped electrons, radical anions and cations, are formed and have been characterized from their absorption spectra. The addition of triplet quenchers and an electron scavenger resulted in a decrease in the yield, implying the participation of the purine triplet state and a radical anion in the reactions leading to the photodestruction of purin

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02564.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Phosphorescence emission and excitation spectra, as well as decay profiles of human serum albumin, were investigated in the wavelength regions of the tryptophan and tyrosine absorption and emission spectra in potassium phosphate buffer at 77 K. Emission and excitation spectra were found to be linear superpositions of the contributions of the tryptophan and tyrosine residues. It is suggested, therefore, that there is no significant tyrosine to tryptophan energy transfer in this protein at low temperature. The phosphorescence decay is, in general, multiexponential with lifetime components of 5.95, 2.7, and 1.2 s. The longest lifetime is characteristic of tryptophan, whereas the two short components are attributed to two types of tyrosine residues located in different environments within the protein. The latter is confirmed by a detailed analysis of the phosphorescence decay profiles determined at different emission wavelengths, and utilizing different wavelengths of excitation favoring either the tryptophan or tyrosine residue

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02565.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—A series of alkyltrimethylammonium bromides containing terminal phosphorescent chromo‐phores have been prepared and characterized. 10‐(4‐bromo, l‐naphthoyl)decyltrimethylammonium bromide(BND–10) has a critical micelle concentration (CMC) of 14 mM and a micellar mean aggregation number () of 105. Analogous detergents,BND–11, ‐8, and ‐5 have also been prepared; in each case, the naphthoyl group is located at the terminal carbon of an alkyl chain of the indicated length. The normal behavior of increasing and decreasing CMC with increasing aliphatic chain length is observed. When compared with unsubstituted alkyltrimethylammonium bromides, the 4‐bromo, 1‐naphthoyl chromo‐phore is roughly equivalent to 6 methylenes with respect to hydrophobic contribution. A broad phosphorescence maximizing at about 590 nm is readily detected upon photoexcitation of the BND molecules in various solvents. The weak fluorescence of the probes is consistent with efficient intersystem crossing of the BND molecules. BND–10 has a phosphorescence yield of 0.023 and a lifetime of 1 ms in water at 250C. The probes are useful for the study of micelle‐

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02566.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Phospholipid vesicles of saturated and unsaturated phosphatidylcholines have been prepared with phenanthrenequinone incorporated into the hydrocarbon region of the lipid bilayer. Blue or ultraviolet light exposure of these vesicles causes a loss of quinone absorbance and the corresponding formation of new absorbance bands due to addition products. In vesicles composed of unsaturated phospholipids, cycloaddition is preferred over R‐H addition. The quantum yield for quinone disappearance is ‐0.25 in vesicles which contain unsaturated phospholipids and decreases to 0.08 when the photolysis is conducted below the lipid characteristic temper

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02567.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The photochemistry of a series of aryl azides used in, or closely related to some of those used in photoaffinity labeling studies, has been investigated by flash photolysis, continuous irradiation and low‐temperature irradiation with IR and UV spectroscopic analysis. Results indicate that labeling preferentially takes place via singlet species. The reactive intermediates appear to be cycloazaheptatetraenes and/or the corresponding benzazirines. The reactive intermediates have τ½of the order of milliseconds or shorter and oxygen may act as a quencher, thereby interfering with the affinity lab

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02568.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—The emission of several 1,3‐bichromophoric(BC) systems has been investigated in aqueous solutions containing various cyclodextrins (CD's). In all cases where molecular models reveal that the correspondence of the size and shape of the eclipsed conformation of the BC system and the cavity CD is high, a stable CD (host)‐BC (guest) complex is formed and in these cases, the ratio of excimer to monomer emission intensityUE/IM)is much larger than that found in homogeneous solution. The effect of application of high pressure on the IE/IMratio was investigated, as was the influence of 02quenching of excimer and monomer in homogeneous solutions, in aqueous micellar solutions, and in aqueous solutions of CD complexes. A strong protection from 02quenching is observed in the latter

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02569.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Ultraviolet inactivation ofHaemophilus influenzaetransforming DNA followed inverse square root kinetics in both mismatch repair‐proficient(hex+) and deficient(hex‐1)recipients. No DNA concentration effect was seen with UV‐excision repair‐deficient(uvr‐) strains. Low‐efficiency genetic markers remained more sensitive than high‐efficiency ones when they were assayed on excision repair‐deficienthex+uvr‐strains. They were equally resistant whenhex+uvr‐recipients were used. We explain this by assuming that recombinational repair of UV lesions in the donor strand and mismatch repair of the recipient strand may overlap and cause double strand interruptions. This will eliminate low‐e

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02570.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—We have recently described the construction and some properties ofHaemophilus influenzaeRd strains with long and different R plasmid‐derived DNA segments (nonhomologous inserts) at the same site in the HP1 prophage. These inserts can be added to a recipient's genome by genetic transformation, they can be deleted from the recipient genome, or they can be replaced by another insert. We report here that the UV inactivation of all three phenomena followed single hit kinetics. Deletion was roughly 10 times more resistant; its UV‐sensitivity equaled that of a high‐efficiency point mutation. There was an inverse correlation between UV‐sensitivity and additive transformation efficiency of the various inserts; sensitivity may thus be a measure of insert size. This correlation was not seen for deletion. All three phenomena were more sensitive when they were measured on excision repair‐deficient uvr‐recipients. The dose‐reduction factor for addition was about 1.5 while it was about 2

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02571.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Relative potency of 10 fluorescein derivatives as sensitizers of delayed photohemolysis of human erythrocytes has been assessed. Dilute suspensions of washed cells were illuminated in the presence of sensitizer at different concentrations for 1 h and analyzed for percent hemolysis following 23 h of dark incubation. Plots of percent hemolysis versus concentration showed a steep dependence on concentration for all sensitizers. Additional measurements of octanol/water partition coefficients, photon absorption in octanol and in saline and photobleach rates were made. After correction for absorption cross section, the effectiveness values ranged over more than three orders of magnitude with fluorescein being the least potent and rose bengal the most. A reasonable prediction of potency is obtained by taking the product of partition coefficient, relative absorption in octanol versus water and molecular weight of the substituents added to the fluorescein skeleton. The results suggest that the influence of halogen substitution on sensitizing potency is exerted by four factors; (1) distribution of sensitizer into a low polarity region of the cell membrane, (2) absorption efficiency in a low polarity region, (3) triplet quantum yield, and (4) photobleach rat

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02572.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract—Protriptyline (PTL; N‐methyl‐5H‐dibenzo[a,d]cycloheptene‐5‐propylamine) hydrochloride is a skin photosensitizing agent in humans. The fluorescence and photochemical behavior of PTL varies with the solvent. In water, 40% ethanol and ethanol in the hydrochloride salt of PTL has a fluorescence quantum yield of 0.81. The fluorescence quantum yield of PTL free base in selected organic solvents is between 0.41 and 0.17; in ethanol it remains at 0.81. Photolysis of PTL in acidic aqueous solution yields at least five photoproducts which were separated by high‐performance liquid chromatography. Three of these photoproducts lysed red blood cells. One of the photoproducts has been identified as a cyclobutyl photodimer of PTL based on its mass spectrum and UV absorption and its ability to undergo photore‐versal with 254 nm irradiation. The others were not cyclobutyl dimers. The yield of lytic products decreased as the ethanol content was increased and were not formed from PTL free base

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb02573.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY