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Reaction chemistry & engineering 4, 1691–1870 (2019). doi:10.1039/C9RE00191C, Detailed analysis of reaction mechanisms by in situ techniques are important for detecting metastable intermediates, analysing polymorphic transitions and thereby for the discovery of new compounds. This article presents the first combination of serial crystallography with in situ luminescence and X-ray diffraction (XRD) measurements to monitor the synthesis of [Eu(phen)2(NO3)3] (phen = 1,10-phenanthroline). In a batch reaction, it is found that this complex is polymorphic, crystallizing into two distinct monoclinic structures. We track the evolution of the synthesis conditions for these phases using in situ XRD combined with real time measurements of pH value, ion conductivity, infrared (IR) spectroscopy and in situ luminescence analysis of coordination sensors (ILACS). However, in a flow reactor a different combination of phases is produced. A serial crystallography experiment utilizing a nanofocused synchrotron X-ray beam to identify individual crystallites reveals the simultaneous formation of the two phases, as well as, a third unknown phase. This showcases the feasibility of phase detection on an individual crystallite level to track the synthesis of new materials., Published by Royal Society of Chemistry, Cambridge

The formation of stable and functional surface layers (S-layers) via self-assembly of surface-layer proteins on the cell surface is a dynamic and complex process. S-layers facilitate a number of important biological functions, e.g., providing protection and mediating selective exchange of molecules and thereby functioning as molecular sieves. Furthermore, S-layers selectively bind several metal ions including uranium, palladium, gold, and europium, some of them with high affinity. Most current research on surface layers focuses on investigating crystalline arrays of protein subunits in Archaea and bacteria. In this work, several complementary analytical techniques and methods have been applied to examine structure–function relationships and dynamics for assembly of S-layer protein slp-B53 from Lysinibacillus sphaericus: (1) The secondary structure of the S-layer protein was analyzed by circular dichroism spectroscopy; (2) Small-angle X-ray scattering was applied to gain insights into the three-dimensional structure in solution; (3) The interaction with bivalent cations was followed by differential scanning calorimetry; (4) The dynamics and time-dependent assembly of S-layers were followed by applying dynamic light scattering; (5) The two-dimensional structure of the paracrystalline S-layer lattice was examined by atomic force microscopy. The data obtained provide essential structural insights into the mechanism of S-layer self-assembly, particularly with respect to binding of bivalent cations, i.e., Mg2+ and Ca2+. Furthermore, the results obtained highlight potential applications of S-layers in the fields of micromaterials and nanobiotechnology by providing engineered or individual symmetric thin protein layers, e.g., for protective, antimicrobial, or otherwise functionalized surfaces.

Many systems in nature are perfectly optimized for their function. Good examples therefore are surface layer (S-layer) proteins. These proteins form two-dimensional lattices acting as interfaces between prokaryotic cells and their environment and as such as selective and protecting barrier. Outstanding properties are their autocatalytic self-assembly, high physicochemical stability, many different and regular arranged functional groups and their nanoscale fine structure. Understanding the dynamic and complex process of self-assembly is not only highly interesting from a scientific point of view but also for the technical application of this group of proteins. Their use is particularly promi­sing for nanotechnology, and here especially for surface modification creating metal selective filter materials, bio-sensors or improved catalytic materials. Especially challenging within an industrial process is controlling the speed of the lattice formation and the formation of large areas of undisturbed lattices. For the examination of the structure-function relationship and the process dynamics of the protein self-assembly of the S-layer from Lysinibacillus sphaericus JG-B53 several complementary analytical techniques and methods have been applied: 1) The secondary structure of the S-layer protein was analyzed by CD spectroscopy. 2) Small-angle X-ray scattering (SAXS) was applied to gain insights into the three dimensional structure in solution. 3) The interaction with bivalent cations was followed by differential scanning calorimetry (DSC). 4) The dynamics and time-dependent assembly of S-layers was also investigated applying dynamic light scattering. 5) The two dimensional structure of the para-crystalline S-layer lattice was additionally examined by atomic force microscopy (AFM). The data obtained provide essential structural insights into the mechanism of the S-layer self-assembly, particularly with respect to the binding of the bivalent cations Mg2+ and Ca2+.

Structural dynamics 2(4), 041717(2015). doi:10.1063/1.4922648, A major challenge in high-resolution x-ray free-electron laser-based coherent diffractive imaging is the development of aerosol injectors that can efficiently deliver particles to the peak intensity of the focused X-ray beam. Here, we consider the use of a simple convergent-orifice nozzle for producing tightly focused beams of particles. Through optical imaging we show that 0.5 μm particles can be focused to a full-width at half maximum diameter of 4.2 μm, and we demonstrate the use of such a nozzle for injecting viruses into a micro-focused soft-X-ray FEL beam., Published by AIP Publishing LLC, Melville, NY