Abstract
This work reports an all-atom molecular dynamics study of the first stages of aggregation of poly(gamma-benzyl-L-glutamate)—PBLG—polymers end-capped with C60. PBLG self-assembles in water and shows polymorphism when specific changes in the molecular structure are made. Three variants of PBLG are compared, which differ for the location of the C60 moiety: N-terminus, C-terminus, or both. The aim of the computational experiments was to rationalize the key molecular properties that are relevant to the supramolecular polymorphism. Single-peptide simulations in tetrahydrofuran and in water allowed to quantify the strength of the self-assembly driving force in terms of the overall order parameter of the phenyl rings that are “coating” the peptides. Two-peptide simulations for the singly capped peptides showed that two kinds of aggregates can be formed: one “slow” thermodynamically more stable, and one “fast” kinetically favoured. These first-stage aggregates are interpreted as the seeds leading to different self-assemblies.Graphical abstract
Highlights
Self-assembly, one of the most amazing phenomena in nature [1,2,3], is a central field of study in materials science [4,5,6,7], nanochemistry [8, 9], and biomimetic chemistry [2, 10,11,12,13,14,15,16]
This work reports an all-atom molecular dynamics study of the first stages of aggregation of poly(c-benzyl-L-glutamate)—PBLG—polymers end-capped with C60
A plethora of approaches to accelerate these calculations are available: (1) Monte Carlo methods [18], (2) coarse-grained [19] and mesoscopic [20] deterministic molecular dynamics (MD) simulations; (3) stochastic approaches such as dissipative particle dynamics [16, 21,22,23,24], and Brownian dynamics [25] simulations; (4) mean-field approaches, like the self-consistent field theory [26], which is purely thermodynamic, based on the minimization of a phenomenological expression for the overall free energy of the system, and (5) multiscale methods such as external potential dynamics [26] and MesoDyn [27], in which the building blocks are described at some level of detail, while the medium is treated at a mean-field level
Summary
Self-assembly, one of the most amazing phenomena in nature [1,2,3], is a central field of study in materials science [4,5,6,7], nanochemistry [8, 9], and biomimetic chemistry [2, 10,11,12,13,14,15,16]. Of particular interest is the non-covalent self-assembly in systems where the single building block includes all necessary ‘‘information’’ to control, on the one hand, the size of the self-assembled structure (e.g. by modifying one or more dimensions of the building block), and on the other hands, the supramolecular shape by applying small, directed chemical changes to the building blocks. The latter characteristic is referred to as supramolecular polymorphism [17]. On the other hands, rationalizing how the geometrical properties of the self-assembled structures are related to the chemical details of the building blocks is a second important issue, which is concerned with the parametrization of the force fields of the computational approaches mentioned above
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