Showing papers by "Paul van der Schoot published in 2013"
TL;DR: A combination of in situ investigations are presented, which show that for the crystallization of calcium phosphate these nanometre-sized units are in fact calcium triphosphate complexes and demonstrate how the existence of these complexes lowers the energy barrier to nucleation and unites classical and non-classical nucleation theories.
Abstract: Despite its importance in many industrial, geological and biological processes, the mechanism of crystallization from supersaturated solutions remains a matter of debate. Recent discoveries show that in many solution systems nanometre-sized structural units are already present before nucleation. Still little is known about the structure and role of these so-called pre-nucleation clusters. Here we present a combination of in situ investigations, which show that for the crystallization of calcium phosphate these nanometre-sized units are in fact calcium triphosphate complexes. Under conditions in which apatite forms from an amorphous calcium phosphate precursor, these complexes aggregate and take up an extra calcium ion to form amorphous calcium phosphate, which is a fractal of Ca(2)(HPO(4))(3)(2-) clusters. The calcium triphosphate complex also forms the basis of the crystal structure of octacalcium phosphate and apatite. Finally, we demonstrate how the existence of these complexes lowers the energy barrier to nucleation and unites classical and non-classical nucleation theories.
580 citations
TL;DR: For systems with a sufficiently high degree of polydispersity, it is found that Z(c) can become smaller than unity, in analogy with observations reported for generalized and complex networks.
Abstract: The connectedness percolation threshold (� c) and critical coordination number (Zc) of systems of penetrable spherocylinders characterized by a length polydispersity are studied by way of Monte Carlo simulations for several aspect ratio distributions. We find that (i) � c is a nearly universal function of the weight-averaged aspect ratio, with an approximate inverse dependence that extends to aspect ratios that are well below the slender rod limit and (ii) that percolation of impenetrable spherocylinders displays a similar quasiuniversal behavior. For systems with a sufficiently high degree of polydispersity, we find that Zc can become smaller than unity, in analogy with observations reported for generalized and complex networks.
52 citations
TL;DR: A nanoparticle-templated assembly approach was employed here to determine how different polymorphs of the Hepatitis B virus icosahedral capsid respond to a gradual change in the encapsulated cargo size, and it was found that assembly into complete virus-like particles occurs cooperatively around a variety of core diameters, albeit the degree of cooperativity varies.
Abstract: Protein cages providing a controlled environment to encapsulated cargo are a ubiquitous presence in any biological system. Well-known examples are capsids, the regular protein shells of viruses, which protect and deliver the viral genome. Since some virus capsids can be loaded with nongenomic cargoes, they are interesting for a variety of applications ranging from biomedical delivery to energy harvesting. A question of vital importance for such applications is how does capsid stability depend on the size of the cargo? A nanoparticle-templated assembly approach was employed here to determine how different polymorphs of the Hepatitis B virus icosahedral capsid respond to a gradual change in the encapsulated cargo size. It was found that assembly into complete virus-like particles occurs cooperatively around a variety of core diameters, albeit the degree of cooperativity varies. Among these virus-like particles, it was found that those of an outer diameter corresponding to an icosahedral array of 240 proteins (T = 4) are able to accommodate the widest range of cargo sizes.
29 citations
TL;DR: The Brownian dynamics simulations of hard semiflexible particles mimic the experiments and indicate that full-length jumps must be due to collective dynamics in which particles move in stringlike fashion in and between neighboring columns, while half jumps arise as a result of particles moving into defects.
Abstract: We report on single-particle dynamics of strongly interacting filamentous fd virus particles in the liquid-crystalline columnar state in aqueous solution. From fluorescence microscopy, we find that rare, discrete events take place, in which individual particles engage in sudden, jumplike motion along the main rod axis. The jump length distribution is bimodal and centered at half- and full-particle lengths. Our Brownian dynamics simulations of hard semiflexible particles mimic our experiments and indicate that full-length jumps must be due to collective dynamics in which particles move in stringlike fashion in and between neighboring columns, while half jumps arise as a result of particles moving into defects. We find that the finite domain structure of the columnar phase strongly influences the observed dynamics.
14 citations