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Moustafa E.M.,American University in Cairo | Ritacco I.,University of Calabria | Ritacco I.,Centro Of Calcolo Ad Alte Prestazioni Per Elaborazioni Parallele E Distribuite | Sicilia E.,University of Calabria | And 6 more authors.
Physical Chemistry Chemical Physics | Year: 2015

Collision-induced dissociation (CID) experiments on protonated carnosine, [carnosine + H]+, with several collision energies were shown to yield eleven different fragment ions with the generation of product ions [carnosine-H2O + H]+ and [carnosine-NH3 + H]+ being the lowest energy processes. Energy-resolved CID showed that at slightly higher collision energies the ions [histidine + H]+ and [histidine-H2O-CO + H]+ are formed. At even higher energies four other product ions were observed, however, attained relatively lower abundances. Quantum chemistry calculations, carried out at different levels of theory, were employed to probe fragmentation mechanisms that account for all the experimental data. All the adopted computational protocols give similar energetic trends, and the range of the calculated free energy barrier values for the generation of all the observed product ions is in agreement with the fragmentation mechanisms offered here. © the Owner Societies 2015.


Ritacco I.,University of Calabria | Ritacco I.,Centro Of Calcolo Ad Alte Prestazioni Per Elaborazioni Parallele E Distribuite | Moustafa E.M.,American University in Cairo | Sicilia E.,University of Calabria | And 4 more authors.
Dalton Transactions | Year: 2015

Collision-induced dissociation (CID) experiments on the protonated carnosine-oxaliplatin complex, [Carnosine + OxPt + H]+ using several collision energies were shown to yield nine different fragment ions. Energy-resolved CID experiments on [Carnosine + OxPt + H]+ showed that the generation of the product ion [Carnosine - H + Pt(dach)]+ (where dach is 1,2-diaminocyclohexane) is the lowest energy process. At slightly higher collision energies, the loss of neutral carnosine from [Carnosine + OxPt + H]+ to produce [OxPt + H]+ was observed, followed by the loss of oxaliplatin from the same precursor ion to produce [Carnosine + H]+. At significantly higher energies, the ion [OxPt - CO2 + H]+ was shown to be formed, while the last two investigated ions [Carnosine + OxPt - CO2 + H]+ and [Carnosine - NH3 - H + Pt(dach)]+ did not attain any significant relative abundance. Density functional calculations at the B3LYP/LANL2DZ level were employed to probe the fragmentation mechanisms that account for all experimental data. The lowest free energy barriers for the generation of each of the ions [Carnosine - H + Pt(dach)]+, [OxPt + H]+, [Carnosine + H]+, [Carnosine + OxPt - CO2 + H]+ and [Carnosine - NH3 - H + Pt(dach)]+ from [Carnosine + OxPt + H]+ according to the fragmentation mechanisms offered here were calculated to be 31.9, 38.8, 49.3, 75.2, and 85.6 kcal mol-1, respectively. This journal is © The Royal Society of Chemistry 2015.


Alberto M.E.,University of Calabria | Alberto M.E.,Centro Of Calcolo Ad Alte Prestazioni Per Elaborazioni Parallele E Distribuite | Butera V.,University of Calabria | Butera V.,Centro Of Calcolo Ad Alte Prestazioni Per Elaborazioni Parallele E Distribuite | And 2 more authors.
Inorganic Chemistry | Year: 2011

The platination processes of DNA bases with second- and third-generation Pt(II) anticancer drugs have been investigated using density functional theory (DFT) combined with the conductor-like dielectric continuum model (CPCM) approach, in order to describe their binding mechanisms and to obtain detailed data on the reaction energy profiles. Although there is no doubt that a Pt-N7 bond forms during initial attack, the energetic profiles for the formation of the monofunctional adducts are not known. Herein, a direct comparison between the rate of formation of the monofunctional adducts of the second- and third-generation anticancer drugs with guanine (G) and adenine (A) DNA bases has been made in order to spotlight possible common or different behavior. The guanine as target for platination process is confirmed to be preferred over adenine for all the investigated compounds and for both the hydrolyzed forms considered in our investigation. The preference for G purine base is dominated by electronic factors and promoted by a more favorable hydrogen-bonds pattern, confirming the important role played by H-bonds in determining both structural and kinetic control on the purine platination process. © 2011 American Chemical Society.

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