SELF-ASSEMBLING PROPERTIES OF GUANOSINE AND DEOXYGUANOSINE DERIVATIVES IN AQUEOUS SOLUTIONS

B. Črnko, I. Drevenšek-Olenik, L. Spindler, J. Cerar, F. Federiconi, P. Mariani

Faculty of Mathematics and Physics, University of Ljubljana; J. Stefan Institute, Ljubljana; Faculty of Chemistry and Chemical Technology, University of Ljubljana , Slovenia; Istituto di Scienze Fisiche, Universita di Ancona, Italy

We performed a comparative study of the self-assembling features of the guanosine and analogous deoxyguanosine derivatives in aqueous solutions. The solutions were investigated by dynamic light scattering (DLS) and 31P-NMR spectroscopy. The work was focused on the specific type of the self-assembled nanosize aggregates, i.e. the G-quartet stacks, which are formed in the pretransitional region of the lyomesomorphic phase transition from the isotropic (I) to the cholesteric phase (Ch). The observations by optical polarization microscopy show that in the guanosine-5'-monophosphate (GMP) solutions the stacking process and the I-Ch phase transition start at significantly lower concentrations than in the deoxyguanosine-5'-monophosphate (dGMP). The concentration region of the pretransitional phase in the GMP is also narrower than in dGMP. These features, however, strongly depend also on the type of the ions present in the solution. For instance, the ammonium ions strongly stimulate the aggregation, while a presence of the sodium ions is much less favorable. The observed properties can be explained by the larger length of the stacks formed in the GMP solutions, which was revealed from the DLS measurements.

Email: brincek@hotmail.com

Address: c.o. Irena Drevensek-Olenik, Faculty of Mathematics and Physics, Jadranska 19, SI-1000 Ljubljana