Local NMR Relaxation of Dendrimers in the Presence of Hydrodynamic Interactions

Abstract

We study the role of hydrodynamic interactions for the relaxation of segments' orientations in dendrimers. The dynamics is considered in the Zimm framework. It is shown that inclusion of correlations between segments' orientations plays a major role for the segments' mobility, that reveals itself in the NMR relaxation functions. The enhancement of the reorientation dynamics of segments due to the hydrodynamic interactions is more significant for the inner segments. This effect is clearly pronounced in the reduced spectral density ωJ(ω), whose maximum shifts to higher frequencies when the hydrodynamic interactions are taken into account.

NMR studies of excluded volume interactions in peptide dendrimers

“…It was established that the local orientational mobility of NMR active groups in a dendrimer depends on their topological distance from the periphery. This regularity is practically independent of the excluded volume (EV) 38 and the hydrodynamic interactions 45 . Note that in ref.…”

NMR relaxation in semiflexible Vicsek fractals

“…periphery. Thus, we see that the local orientational behavior of fractal hyperbranched macromolecules differs very much from that of dendrimers, for which the maximum of the reduced spectral density clearly indicates the remoteness of the segments from the dendrimer's periphery [32,33,37,38,[40][41][42][43].…”

“…In Fig. 6 we present a direct comparison of [J(ω)] for SVF and semiflexible dendrimers (SD) [32,43] is always at lower frequencies for higher m; there is no saturation for high m as for SVF. Moreover, the global maxima of [J(ω)] for SD have a much narrower shape than those for SVF.…”

“…[42]. Also it has been shown that the hydrodynamic interactions do not change the qualitative picture [43]. Thus, for dendrimers the viscoelastic model extended by inclusion of bending rigidity can fairly describe the local orientational mobility manifested by the NMR relaxation.…”

“…Comparison of the reduced spectral densities [J(ω)] for SVF and semiflexible dendrimer (SD), both of functionality F = 3, generation G = 5, and stiffness parameter q br = 0.45. The data for SD are taken from Ref [43]…”