Self-contacts in fractal macromolecules
Par Maxim Dolgushev, Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée (LPTMC), Paris
Mardi 05 Mars, 14h00, Salle des séminaires (215), 2ème étage, Bâtiment A4N
Abstract :
This talk is presenting our investigations on the role of complex connectivity of fractal macromolecules for contact formation and contact density. Fractals provide typical models, e.g., for hyperbranched polymers, proteins, sol-gel branched clusters, and colloidal aggregates.
In works [1,2] we have considered the so-called marginally compact fractals. These special structures use very effectively the available space by filling it densely, but at the same time they have almost all their monomers on the surface. They are of a particular interest in connection with melts of ring polymers as well as with chromatin. However, their existence has been questioned theoretically because of a logarithmic divergence of their self-contact density. We have shown that such a divergence can be removed in practice by introducing linear spacers [1] or semiflexibility constraints [2] and we have characterized the dynamics of these structures.
Also, we have studied the impact of the connectivity on the cyclization kinetics (i.e. on the contact formation) of macromolecules with a fractal structure [3]. We have shown that the non-Markovian effects (i.e. memory) of the tagged monomer motion in a macromolecule are reflected in the out-of-equilibrium conformations at the instant of the first contact. We have connected the multiscale monomer dynamics to the corresponding behavior of the mean-first contact times and have demonstrated that the memory effects increase with the degree of branching.
[1] M. Dolgushev, J. P. Wittmer, A. Johner, O. Benzerara, H. Meyer, J. Baschnagel. Marginally compact hyperbranched polymer trees. Soft Matter 13, 2499—2512 (2017).
[2] M. Dolgushev, A. L. Hauber, P. Pelagejcev, J. P. Wittmer. Marginally compact fractal trees with semiflexibility. Phys. Rev. E 96, 012501 (2017).
[3] M. Dolgushev, T. Guérin, A. Blumen, O. Bénichou, R. Voituriez. Contact kinetics in fractal macromolecules. Phys. Rev. Lett. 115, 208301 (2015).