Effects of Femtosecond UV Laser Pulses on the Structure and Surface Dynamics of Medicinal Plants DNA, Monitored by Surface-Enhanced Raman Spectroscopy

Abstract

Potential medical application of UV laser pulses for cancer treatment is one of the main motivations behind this study. Surface-enhanced Raman signatures-based structural and (sub)picosecond dynamical characterization of genomic DNAs from different medicinal plants are presented. Moreover, structural and surface dynamical changes induced in genomic DNAs from selected medicinal plants species by UV femtosecond laser pulses (λ=280 nm, 170 fs) were investigated between 300 and 1800 cm−1. As a general observation, after nucleic acids irradiation some modes became higher in intensity especially in the wavenumber range between 1050 cm−1–1650 cm−1 or new profiles appeared in this interval in the surface-enhanced Raman spectroscopy (SERS) characteristics. Changes in the structure of dA, dG, dC dT residues, nucleic acid backbone and deoxyribose or unstacking of DNA bases were found. Large wavenumber shifts of the marker bands, which appear in the SERS spectra upon nucleic acids irradiation might be associated with loss of essential structural organization of DNA. As far as surface dynamics of DNA is concerned, for control nucleic acids functional groups, the global relaxation times varied between 0.39–1.77 ps and for UV femtosecond laser pulses-irradiated DNAs, this parameter was slower than 0.35 ps and faster than 1.63 ps. A decrease of the limit values of global relaxation times variation interval is to be observed upon UV treatment of nucleic acids. This faster surface dynamics might be explained by the presence of broken bonds (lesions) in DNA systems after laser pulses irradiation.