ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07415.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—Electronic spectra of indoles are very sensitive to solvents. These solvent effects are particularly pronounced in the case of the fluorescence spectra of indoles. In order to elucidate the solvent band shifts during the relaxation of the excited states, particularly in polar solvents, the dipole moments of the excited singlet states have been estimated from the data of solvent‐dependent Stokes shifts. In addition to indole, indole‐5‐carboxylic acid, indole‐3‐carboxylic acid, indole‐2‐carboxylic acid, 5‐cyano‐ and 5‐bromo‐indoles have been investigated. All indoles showed a substantial increase in dipole moment upon excitation to the emitting state. These results are generally consistent with the Pariser‐Parr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07416.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—The major photoproduct from UV‐irradiation of polynucleotides containing bromouracil has been identified as 5,5′‐diuridinyl by comparingRfvalues and UV and fluorescence spectra with a synthetic c

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07417.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—The spectroscopy and photochemistry of brilliant green leucocyanide1awere investigated at room and low temperature, in polar and nonpolar solvents. At 77 K,1aexhibits solvent independent absorption, fluorescence (φf= 0.1), and phosphorescence (φp= 0.5). Solvent effects become important at room temperature; in polar solvents, φf, decreases and photodissociation yielding brilliant green dye 3 occurs [φdis,(EtOH) ˜0.91. Dye formation and1afluorescence can be quenched by 0.1Mcrotononitrile. Attempts to sensitize dye formation with triplet sensitizers were unsuccessful. The spectroscopy of 3 was also ex

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07418.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—The lifetimes of the triplet excited states of thionine and methylene blue were measured in aqueous and 50 v/v% aqueous acetonitrile solutions acidified with 0.01Nsulfuric or trifluoromethyl‐sulfonic acid. The rate constants for reaction of the triplet excited dyes with ferrous ions were measured in the same solutions. The triplet lifetimes in the absence of added quenchers were insensitive to a change in acid from trifluoromethylsulfonic to sulfuric or to a change in solvent from water to 50v/v% aqueous acetonitrile (τ for triplet thionine ˜7.5 μs, τ for triplet methylene blue ˜4.5 μs). In contrast, the rate constant for reaction of the triplet dyes with ferrous ions increased by nearly a factor of 10 with a change in acid from trifluoromethylsulfonic to sulfuric. In solutions containing sulfate ions this reaction rate constant increased with increasing sulfate concentration and with a change in solvent from water to 50 v/v% aqueous acetonitrile. The results are discussed in terms of the possibility of association of the positively charged reactive ions with sulfate anions. Quenching of the triplet excited dyes by ferric ions or by ground state dye molecules was shown to be negligible at the concentration used for the ferrous ion quench

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07419.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—Previous studies have shown that the relative yields of photoproducts produced in the DNA ofEscherichia colicells UV irradiated at ‐79°C differ from those produced at +21°C; the yield of DNA‐protein cross‐links was markedly enhanced at ‐79°C while the yield of thymine dimers was reduced. In the present studies, cells ofE. coliB/rthywere frozen at ‐79°C, and then UV irradiated (254nm) while frozen(4.7 J m‐2), or after thawing (22 Jm‐2). Essentially the same survival, cell division delay, and DNA synthesis kinetics were observed for these two samples after irradiation, even though the UV fluence differed by a factor of ˜5. This supports previous observations that a correlation exists between the magnitude of the effects of UV radiation upon DNA synthesis kinetics and on cell survival. The weight average molecular weight of the pulse labeled DNA in the sample irradiated at +21°C was one‐half that of the sample irradiated at ‐79°C, and complete repair of daughter‐strand gaps was observed in both cases. Thus, UV‐induced lesions produced in cells at ‐79°C (i.e. DNA‐protein cross‐links) appear to be amenable to post‐replicational repair. While the overall DNA synthesis kinetics were the same for the two irradiation procedures, the apparent number of lesions produced per unit length of DNA was not. This suggests that each of the lesions produced in frozen cells, although apparently fewer in number, must cause a longer local delay in DNA synthes

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07420.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—The energies of the lowest excited singlet, Es, and triplet, Et, states, and singlet‐triplet splitting energies, ΔEs,t, were determined on 18 carcinogenic and 31 noncarcinogenic polycyclic aromatics. A highly significant correlation was found between carcinogenic activity and the energy of the excited singlet state. Compounds with anEs<312 kJ/mol were 4.8 times more likely to be carcinogens than those compounds withEs312 kJ/mol (P= 0.015). Compounds whose singlet energies fell within the narrow range of 297 ≤Es≤ 310 kJ/mol were 22.8 times more likely to be carcinogens than those compounds which fell outside this range (P= 0.00006). A significant correlation between carcinogenic activity andEtenergies was not found, while the correlation involving ΔEs,tenergies was intermediate between theEsandEtcorrelations. The phosphorescence lifetimes, τp, of the 18 carcinogenic aromatics and 27 of the noncarcinogenic aromatip were determined, and were shown not to be correlated with carcinogenic activity. When either theEtor ΔEs,tenergies were plotted as a function ofEsit was found that the carcinogens tended to form in an elliptical cluster. Compounds whoseEsandEtenergies placed them within the ellipse were 9.7 times more likely to be carcinogens than those compounds which fell outside the ellipse (P= 0.002), while with theEs, ΔEs,tellipse, compounds which fell inside were 20.6 times more likely to be carcinogens than those which fell outside (P= 0.0004).Es, Et, ΔEs,tand τpvalues were also determined on 12 carcinogenic and 4 noncarcinogenic alkyl substituted benz[a]anthracenes. There was no significant difference between the carcinogens and noncarcinogens and the “elliptical” correlation predicted both the carcinogens and noncarcinogens to be carcinogenic. The results suggest that either some property(ies) of the lowest excited singlet state, but not its energy, or some molecular property(ies) which runs parallel to singlet state energies may be important in determining carcinogenic activity in po

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07421.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—The rates of the photosensitized immobilization of the nauplii of the crustaceanArtemia salinawere measured as a function of irradiation time and the amount of light absorbed by the sensitizers. The nauplii were incubated in the dark in dilute solutions of the sensitizers for periods of 2 and 22 h prior to irradiation. Nineteen carcinogenic and 22 noncarcinogenic polycyclic aromatic hydrocarbons were used as sensitizers. Relative photodynamic activities (RPA) were determined from the rates of immobilization using benz[c]acridine as a standard (RPA = 1). High RPA was restricted to carcinogenic compounds with 4 and 5 fused rings, compounds with 6 or more fused rings had low RPA regardless of their carcinogenic activities. The correlation of RPA with carcinogenic activity was excellent (P= 0.006 and 0.009 for the 2 and 22 h dark incubations, respectively). It is suggested that carcinogenesis by polycyclic aromatics may result from sublethal photodynamic effect

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07422.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—Toluidine blue, a thiazine dye, was shown to havein vivophotodynamic activity through singlet oxygen (O21Δg) production. This was based mainly on the effective protection by N‐3and the marked enhancement in D2O for the sensitized inactivation of yeast cells. The mode of thein vivoactivity was, however, quite different from that of acridine orange, for which the singlet oxygen mechanism has also been proposed. The most characteristic feature in the toluidine blue‐sensitization was the total lack of the induction of gene conversion (attrp5), while the survival went down below 10%. The non‐induction of genetic changes was confirmed at several pH's in the neutral region, whereas the inactivation was seen in parallel to the reported pH dependence of singlet oxygen productionin vitro. Direct measurements by microspectrophotometry showed none of the toluidine blue was accumulated in the cell. It was also ascertained from acridine‐sensitized induction of gene conversion that toluidine blue never interfered with the binding of acridine orange to cellular DNA. These findings suggested that the unique mode of photodynamic activity of toluidine blue is attributable to its action from outside of the cell. Furthermore, comparisons between the photodynamically treated cells (with toluidine blue) and non‐treated cells with respect to the response to UV irradiation excluded certain cell functions relating to the expression of gene conversion from the possible damage sites. The photo‐reactivation process of UV induced gene conversion was not disturbed by the pre‐toluidine blue sensitition. In view of the foregoing results, the plasma membrane was tentatively suggested as the most likel

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07423.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Abstract—The hemolysis of human erythrocytes by irradiation at 254 nm has been studied. Neither superoxide radicals nor singlet oxygen play a significant rôle and it is likely that the major species involved are hydroxyl radicals and, indirectly, carbonate anion or formate radicals. Similarly, when erythrocytes are treated with a system commonly used as source of superoxide radicals (photoreduction of riboflavin) it has been demonstrated that O‐2does not participate in lysis, but that singlet oxygen (possibly with hydroxyl radicals) is a major oxygen species involved in destruction of the cell memb

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1977.tb07424.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY