STRUCTURAL STUDY OF THE AGGREGATES FORMED BY THE DINUCLEOSIDE PHOSPHATE-G2 IN AQUEOUS-SOLUTION

X-ray diffraction results in magnetically oriented samples of aqueous solutions of the sodium salt of the dinucleoside phosphate G2 in the cholesteric N* phase are presented. The symmetry of the diffraction confirms a model of stacking of tetrameric disks forming cylindrical aggregates in the N* phase. A weak band at 7 angstrom not previously observed gives further information on the inner structure of the cylindrical aggregates. Analysis of the diffraction peak position in low angle evidences a change in functional behaviour of the distance a between cylinder axes as a function of the volume concentration c(v) of G2. In the H phase, a is-proportional-to c(v)-1/2 as it should for infinite cylinders; in the N* phase, a is-proportional-to c(v)-1/3, typical of finite cylinders. The cross-over of functional behaviour occurs at the N*-H phase transition. There is therefore cylinder growth along the N* phase.