• vibrational spectroscopy
• anticancer drug
• computational modeling
• electronic spectroscopy

The aim of the study that is here described is the modeling of structural and spectroscopic properties of doxorubicin (DOX) interacting with complex environments, in particular with water and DNA. The attention is especially focused on resonance Raman (RR) spectroscopy, which is widely used to probe the interaction between a molecular system and the external environment. In particular, RR has been reported to be able to provide information on the intercalation of DOX between DNA base pairs, through the comparison of RR spectra measured for DOX-DNA complexes and DOX in aqueous solution.
Raman scattering can be defined as the inelastic scattering of an electromagnetic radiation by a molecular system. When the incident radiation is resonant with the sample, the RR spectroscopy is obtained. Both resonant and non-resonant Raman can be regarded as vibro-electronic phenomenona: both provide information on the vibrational structure of the molecular system.

To obtain a reliable modeling of RR spectra, a physically consistent description of the target molecule (the solute), of the solvent and of the interaction between the solvated system and the external radiation are needed. In the framework that we have adopted, DOX is treated at the quantum mechanical (QM) level, by exploiting approaches rooted in the Density Functional Theory (DFT), as implemented in a widely used computational chemistry software. The presence of the external environment (either an aqueous solution or DNA) has been taken into account through a continuous description. In particular, the Polarizable Continuum Model (PCM) has been employed, in which the environment is treated as a continuum polarizable dielectric medium surrounding the solute molecule, treated quantum mechanically, and which is hosted within a molecule-shaped cavity.
The comparison between the calculated results with experimental findings taken from the literature shows that our approach is able to describe the main features of vibrational RR spectra, as well as vibrational infrared (IR) and absorption UV-Vis spectra.
As a further test of the effectiveness of the continuous description of the aqueous environment, and to possibly explain some of the discrepancies between calculated and experimental results, the solvation of DOX in aqueous solution has also been studied by means of simulations techniques rooted in the Molecular dynamics (MD), where an atomistic description of the solvent is exploited.