Parameter inversion of a polydisperse system in small-angle scattering.

A general method to invert parameter distributions of a polydisperse system using data acquired from a small-angle scattering (SAS) experiment is presented. The forward problem, calculating the scattering intensity given the distributions of any causal parameters of a theoretical model, is generalized as a multi-linear map, characterized by a high-dimensional Green tensor that represents the complete scattering physics. The inverse problem, finding the maximum-likelihood estimation of the parameter distributions (in free form) given the scattering intensity (either a curve or an image) acquired from an experiment, is formulated as a constrained nonlinear programming (NLP) problem.

Dynamical Accuracy of Water Models on Supercooling.

Molecular dynamics (MD) simulations are commonly used to explore the structural and dynamical properties of supercooled bulk water in the so-called "no man's land" (NML) (150-227 K), where crystallization occurs almost instantaneously. This approach has provided significant insight into experimentally inaccessible phenomena. In this paper, we compare the dynamics of simulations using one-, three-, and four-body water models to experimentally measured quasielastic neutron scattering spectra.

Structural studies of P-type ATPase-ligand complexes using an X-ray free-electron laser.

Membrane proteins are key players in biological systems, mediating signalling events and the specific transport of e.g. ions and metabolites.

Effects of self-seeding and crystal post-selection on the quality of Monte Carlo-integrated SFX data.

Serial femtosecond crystallography (SFX) is an emerging method for data collection at free-electron lasers (FELs) in which single diffraction snapshots are taken from a large number of crystals. The partial intensities collected in this way are then combined in a scheme called Monte Carlo integration, which provides the full diffraction intensities. However, apart from having to perform this merging, the Monte Carlo integration must also average out all variations in crystal quality, crystal size, X-ray beam properties and other factors, necessitating data collection from thousands of crystals.

Diffusion-equation method for crystallographic figure of merits.

Global optimization methods play a significant role in crystallography, particularly in structure solution from powder diffraction data. This paper presents the mathematical foundations for a diffusion-equation-based optimization method. The diffusion equation is best known for describing how heat propagates in matter.

Three-centre hydrogen bonds in triphenyl-phosphine oxide-hydro-quinone (1/1).

The title cocrystal, C(18)H(15)OP·C(6)H(6)O(2), belongs to a series of mol-ecular systems based on triphenyl-phosphine P-oxide. The O atom of the oxide group acts as an acceptor for hydrogen bonds from OH groups of two hydro-quinone mol-ecules which lie on inversion centres [O⋯O = 2.7451 (17) and 2.

Conformational analysis by solid-state NMR and its application to restrained structure determination from powder diffraction data.

Solid-state NMR is used to dramatically improve the efficiency and reliability of molecular crystal structure determination from X-ray powder diffraction data.

A hybrid Monte Carlo method for crystal structure determination from powder diffraction data.

A hybrid Monte Carlo algorithm for crystal structure determination from powder diffraction data is presented. The algorithm combines the key components of molecular dynamics and Monte Carlo simulations to achieve efficient sampling of phase space, allowing the crystal structure of capsaicin to be determined from powder diffraction data more effectively than by a simulated-annealing approach. The implementation of the algorithm, the choice of the simulation parameters and the performance of the algorithm are discussed.

A maximum-likelihood method for global-optimization-based structure determination from powder diffraction data.

A maximum-likelihood algorithm has been incorporated into a crystal structure determination from a powder diffraction data framework that uses an integrated-intensity-based global optimization technique. The algorithm is appropriate when the structural model being optimized is not a complete description of the crystal structure under study.