4,127 research outputs found
Beyond icosahedral symmetry in packings of proteins in spherical shells
The formation of quasi-spherical cages from protein building blocks is a
remarkable self-assembly process in many natural systems, where a small number
of elementary building blocks are assembled to build a highly symmetric
icosahedral cage. In turn, this has inspired synthetic biologists to design de
novo protein cages. We use simple models, on multiple scales, to investigate
the self-assembly of a spherical cage, focusing on the regularity of the
packing of protein-like objects on the surface. Using building blocks, which
are able to pack with icosahedral symmetry, we examine how stable these highly
symmetric structures are to perturbations that may arise from the interplay
between flexibility of the interacting blocks and entropic effects. We find
that, in the presence of those perturbations, icosahedral packing is not the
most stable arrangement for a wide range of parameters; rather disordered
structures are found to be the most stable. Our results suggest that (i) many
designed, or even natural, protein cages may not be regular in the presence of
those perturbations, and (ii) that optimizing those flexibilities can be a
possible design strategy to obtain regular synthetic cages with full control
over their surface properties.Comment: 8 pages, 5 figure
Influence of Metal, Ligand and Solvent on Supramolecular Polymerizations with Transition-Metal Compounds: A Theoretical Study
The nature of intermolecular interactions governing supramolecular polymerizations is very important to control their cooperativity. In order to address this problem, supramolecular columns made of Pt(II) and Pd(II) complexes of oligo(phenyleneethynylene)-based pyridine (OPE) and tetrazolyl-pyridine ligands (TEP) were investigated through the dispersion-corrected PM6 method. Aromatic, CH-π, M-Cl and metallophilic interactions helped stabilize the supramolecules studied, and their geometries and associated cooperativities were in excellent agreement with experimental data. The OPE ligand and/or the presence of Pt(II) have led to stronger metallophilic interactions and also to cooperative supramolecular polymerizations, which clearly suggests that metallophilic interactions are a key factor to control cooperativity. The results indicate that sequential monomer addition is in general less spontaneous than the combination of two larger pre-formed stacks. The present theoretical investigations contribute to the further understanding of the relation between the thermodynamics of supramolecular polymerizations and the nature of different synthons
- …