Crystal structures of the amino-terminal domain of N-cadherin provide a picture at the atomic level of a specific adhesive contact between cells. A repeated set of dimer interfaces is common to the structure in three lattices. These interactions combine to form a linear zipper of molecules that mirrors the linear structure of the intracellular filaments with which cadherins associate. This cell-adhesion zipper may provide a mechanism to marshal individual molecular adhesive interactions into strong bonds between cells.

One of the most fundamental tasks in nanoscience is the accurate determination of particle sizes. Various methods have been developed to elucidate the mean particle diameter and the standard deviation for an ensemble of nanocrystals. However, good agreement between the results from different methods is not always encountered in the literature. In this study, we investigate colloidally prepared, highly monodisperse CoPt3 nanoparticles by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and powder X-ray diffraction (XRD). The results are compared in order to examine to which extent agreement is obtained by the different techniques when applied to small nanocrystals in the size range below 10 nm. In particular, the applicability of the simple Scherrer formula for size determination from the broadening of XRD reflections is checked. When the different techniques are correctly applied, the results from all methods are in good agreement.

Water exists in high- and low-density amorphous ice forms (HDA and LDA), which could correspond to the glassy states of high- (HDL) and low-density liquid (LDL) in the metastable part of the phase diagram. However, the nature of both the glass transition and the high-to-low-density transition are debated and new experimental evidence is needed. Here we combine wide-angle X-ray scattering (WAXS) with X-ray photon-correlation spectroscopy (XPCS) in the small-angle X-ray scattering (SAXS) geometry to probe both the structural and dynamical properties during the high-to-low-density transition in amorphous ice at 1 bar. By analyzing the structure factor and the radial distribution function, the coexistence of two structurally distinct domains is observed at = 125 K. XPCS probes the dynamics in momentum space, which in the SAXS geometry reflects structural relaxation on the nanometer length scale. The dynamics of HDA are characterized by a slow component with a large time constant, arising from viscoelastic relaxation and stress release from nanometer-sized heterogeneities. Above 110 K a faster, strongly temperature-dependent component appears, with momentum transfer dependence pointing toward nanoscale diffusion. This dynamical component slows down after transition into the low-density form at 130 K, but remains diffusive. The diffusive character of both the high- and low-density forms is discussed among different interpretations and the results are most consistent with the hypothesis of a liquid-liquid transition in the ultraviscous regime.

During ultrafast demagnetization of a magnetically ordered solid, angular momentum has to be transferred between the spins, electrons, and phonons in the system on femto- and picosecond timescales. Although the intrinsic spin-transfer mechanisms are intensely debated, additional extrinsic mechanisms arising due to nanoscale heterogeneity have only recently entered the discussion. Here we use femtosecond X-ray pulses from a free-electron laser to study thin film samples with magnetic domain patterns. We observe an infrared-pump-induced change of the spin structure within the domain walls on the sub-picosecond timescale. This domain-topography-dependent contribution connects the intrinsic demagnetization process in each domain with spin-transport processes across the domain walls, demonstrating the importance of spin-dependent electron transport between differently magnetized regions as an ultrafast demagnetization channel. This pathway exists independent from structural inhomogeneities such as chemical interfaces, and gives rise to an ultrafast spatially varying response to optical pump pulses.