Roberto Improta

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The excited-state properties of uracil, thymine, and nine other derivatives of uracil have been studied by steady-state and time-resolved spectroscopy. The excited-state lifetimes were measured using femtosecond fluorescence upconversion in the UV. The absorption and emission spectra of five representative compounds have been computed at the TD-DFT level,(More)
A thorough study of the acid-base behavior of the four histidines and the other titratable residues of the structured domain of human prion protein (125-228) is presented. By using multi-tautomer electrostatic calculations, average titration curves have been built for all titratable residues, using the whole bundles of NMR structures determined at pH 4.5(More)
The role of acidic pH in the conversion of human prion protein to the pathogenic isoform is investigated by means of molecular dynamics simulations, focusing the attention on the effect of protonation of histidine residues on the conformational behavior of human PrPC globular domain. Our simulations reveal a significant loss of alpha-helix content under(More)
The photophysics and photochemistry of DNA is of great importance due to the potential damage of the genetic code by UV light. Quantum mechanical studies have played a key role in interpretating the results of modern time-resolved pump-probe spectroscopy, and in elucidating the main photoactivated reactive paths. This review provides a concise, complete(More)
The first comprehensive quantum mechanical study of solvent effects on the behavior of the two lowest energy excited states of uracil derivatives is presented. The absorption and emission spectra of uracil and 5-fluorouracil in acetonitrile and aqueous solution have been computed at the time-dependent density-functional theory level, using the polarizable(More)
The nuclear DNA content of 23 selachian species (10 Batoidea, 11 Galeomorphii, and 2 Squalomorphii) was histophotometrically studied. Their genome sizes range from 7.5 pg/N in Raja fillae (Batoidea) to 34.1 pg/N in Oxynotus centrina (Squalomorphii). Results show slight differences in the pattern of quantitative variations between the superorders Batoidea(More)
The authors present a new method for the computation of vibrationally resolved optical spectra of large molecules, including the Duschinsky rotation of the normal modes and the effect of thermal excitation. The method automatically selects the relevant vibronic contributions to the spectrum, independently of their frequency, and it is able to provide fully(More)
The excited states of deoxyadenosine (dA) and 9-methyladenine (9Me-Ade) were studied in water and acetonitrile by a combination of steady-state and time-resolved spectroscopy and quantum chemical calculations. Femtosecond fluorescence upconversion experiments show that the decays of dA and 9Me-Ade after excitation at 267 nm are very similar, confirming that(More)
We demonstrate here that tetracycline (TC) can strongly interact (KD' = 189 +/- 7 nM) with model peptides derived from the C-terminal globular domain of the prion protein, hPrP [173-195], and that interaction concerns residues within the C-terminal half of the helix 2, a short region previously indicated as endowed with ambivalent conformational behavior(More)
The photoisomerisation of 1,1'-diethyl-2,2'-pyridocyanine, regarded by Brooker as the simplest cyanine, is examined in methanol by time-resolved experiments and PCM/TD-CAM-B3LYP calculations. Femtosecond transient absorption, fluorescence upconversion, and stimulated Raman scattering, all with broadband coverage, provide a panoramic view of the(More)