engleski

Dielectric spectroscopy of genomic DNA solutions

Physical properties and biological functions of the key biological molecule Deoxyribonucleic acid (DNA) are strongly affected by its aqueous environment, like electrolyte concentration, counter-ion and pH. Thus, a profound understanding of the dynamical properties of native DNA as a function of its aqueous environment, imposes as one of key challenges in the life sciences today. In order to characterize the polarization response of DNA, we employed low frequency dielectric spectroscopy (LFDS). This direct and non-destructive technique has been proved to be powerful tool to probe charge entities and their background structure in various synthetic molecular materials, as well as in bio-macromolecular structures. The home-made device that consists of the capacitive chamber and temperature control unit, was designed for measurement of samples in solution with small volume of 50-200 ml and with conductivities in the range of 2- 2000 mS/cm. This device in conjunction with the Agilent 4294A precision impedance analyzer enables measurements accross a broad frequency (from 40 Hz to100 MHz) and temperature (from 0 oC to +60 oC) range. We present results obtained on a wide range of solutions (0.014 – 17.8 mg/ml) of salmon sperm Na-DNA in pure water and of pure lyophilized (no buffer) calf thymus DNA in pure water and in NaCl electrolyte. We analyze the observed relaxation modes using the generalized Debye function and discuss possible assignments inside the framework of the standard double layer model for polarization response of charged biopolymers in solution.

DNA; dielectric spectroscopy; persistence length

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