[Positron lifetime studies of sodium- and zinc-hyaluronates]

The aim of this work was to test the positron lifetime technique (PLT) as a tool of the structure study of sodium- and zinc-hyaluronates. The information based on the PLT measurements (outlined as follows) proved that this method can be useful in this field as well. The lifetime of ortho-positronium (o-Ps) significantly increased and its intensity decreased in the samples containing Zn2+, comparing to Na-hyaluronates. It showed that the electronic orbitals are more closed in the case of Zn2+ cation that means the overlapping between the wave functions of the positron and of the electrons decreased. (See equation No 1.) The study of the effect of water content suggested that the hydrogen-bridge-bonds "localised" the free electron pairs. The increasing pressure increased the lifetime and it is an evidence that the effect of the cations (Na+ and Zn2+) can be explained rather with the change of the electronic structure than with the altering of the free volumes of the samples.