1,721,519 research outputs found
Studies on the photoreactions (365 nm) between DNA and some methylpsoralens.
No full textWhile many methyl derivatives of psoralen are very active as skin photosensitizers, others have a small activity or are practically inactive. This difference is not explicable in terms of different capacity ofphotobinding to deoxyribonucleic acid (DNA). Other factors are important, especially the ability to form cross linkings in DNA. As a result of a comparison of a group of methylpsoralen derivatives, a good correlation was found between the skin photosensitizing potencies of the various compounds, as evaluated by determining the minimum irradiation time necessary for the production of erythema on guinea pig skin, and the amounts of cross linking formed in DNA as a function of the time of irradiation
Redshift evolution of the H2/H I mass ratio in galaxies
Full text linkIn this paper, we present an attempt to estimate the redshift evolution of the molecular to neutral gas mass ratio within galaxies (at fixed stellar mass). For a sample of five nearby grand design spirals located on the main-sequence (MS) of star-forming galaxies, we exploit maps at 500 pc resolution of stellar mass and star formation rate (M⋆ and SFR). For the same cells, we also have estimates of the neutral (MH I) and molecular ( MH2 ) gas masses. To compute the redshift evolution, we exploit two relations: (i) one between the molecular-to-neutral mass ratio and the total gas mass (Mgas), whose scatter shows a strong dependence with the distance from the spatially resolved MS, and (ii) the one between log(MH2/M⋆) and log (MH I/M⋆). For both methods, we and that MH2 /MH I within the optical radius slightly decreases with redshift, contrary to common expectations of galaxies becoming progressively more dominated by molecular hydrogen at high redshifts. We discuss possible implications of this trend on our understanding of the internal working of high-redshift galaxies
Studies on the mechanism of action of mitomycin C.
No full textThe in vitro formation and properties of the molecular complex between mitomycin C and native DNA were examined by means of various experimental methods; the data obtained indicate that the complex is extremely weak and that the chromophoric moiety of the antibiotic is not involved in its formation. The alkylating activity of mitomycin C was also studied using 3H-mitomycin C; while monofunctional alkylation increases almost in parallel with the concentration of the antibiotic, the difunctional alkylation, causing inter-strand cross-linkages in DNA, rapidly reaches a maximum and then remains constant even when increasing the concentration of the antibiotic and monofunctional alkylation. On the basis of these results, the currently accepted molecular model of the mitomycin--DNA interaction must be revised; a new model of this interaction is presented, which is in better agreement with the properties of mitomycin C and with the latest findings on the subject
Rivisitazioni del vanto epico del guerriero nell'Orestea
No full textA peculiar feature of Aeschylus’s Oresteia, a trilogy characterized by a pervasive blending and overlapping of different linguistic registers, is represented by the reprise and refunctionalisation of the boast of epic warriors on the lying body of a defeated enemy. This paper analyses how the topoi of Homeric boast are applied by Aeschylus to characters who, in different ways, either come into conflict with the epic model (Clytemnestra, Aegisthus, Orestes) or are not up for it because of a disastrous unawareness of the real situation (Agamemnon). This allows the poet to cast light on essential nuances of his new dramatic construction
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