Energy Loss Function for Biological Material: Poly (CSP)

Abstract

In this paper calculated cross sections are presented for the interaction of electrons with poly(CSP), a single-stranded chain that contains one cytosine sugar phosphate unit in the elementary cell. To model a single strand of helical DNA (e.g. the base stacking), the Watson-Crick model for the geometry of poly(CSP) has been used. The use, for computational simplicity, of a single, rather than a double stranded polynucleotide may be justified on the basis of previous calculations indicating that - to a good approximation - the electronic structure (other than excitation states) of complementary base pairs may be described as a superposition of the corresponding structures of the individual components. The cross sections are obtained from the dielectric response function of the system, _(q,?), which is calculated with the aid of a semi-empirical Hamiltonian, the parameters of which have been adjusted to fit available optical and electron scattering data on DNA and related systems.