The effect of the pathological V72I, D109N and T190M missense mutations on the molecular structure of α-dystroglycan.

Dystroglycan (DG) is a highly glycosylated protein complex that links the cytoskeleton with the extracellular matrix, mediating fundamental physiological functions such as mechanical stability of tissues, matrix organization and cell polarity. A crucial role in the glycosylation of the DG α subunit is played by its own N-terminal region that is required by the glycosyltransferase LARGE. Alteration in this O-glycosylation deeply impairs the high affinity binding to other extracellular matrix proteins such as laminins.

FIB-fabricated complex-shaped 3D chiral photonic silicon nanostructures.

Technologies capable of fabricating complex shaped silicon metasurfaces attract increasing attention. The focused ion beam fabrication technique is considered traditionally as causing thick damaged layers in silicon resulting in a significant rise of the optical absorption loss. We examine the structure of the FIB-fabricated nanostructures on the silicon-on-sapphire (SOS) platform and its optical characteristics before and after thermal oxidation.

A new Mo(iv) complex with the pentadentate (NO) Schiff-base ligand: the first non-cyanide pentagonal-bipyramidal paramagnetic 4d complex.

A heptacoordinate complex [Mo(DAPBH)Cl] (HDAPBH is 1,1'-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene)dibenzohydrazine) has been synthesized and characterized structurally and magnetically. It exhibits a slightly distorted pentagonal bipyramidal geometry and reveals paramagnetic behaviour resulting from two unpaired electrons (S = 1) with large positive zero-field splitting (D = +50 cm) and pronounced temperature-independent paramagnetism.

Combination of Functional Nanoengineering and Nanosecond Laser Texturing for Design of Superhydrophobic Aluminum Alloy with Exceptional Mechanical and Chemical Properties.

Industrial application of metallic materials is hindered by several shortcomings, such as proneness to corrosion, erosion under abrasive loads, damage due to poor cold resistance, or weak resistance to thermal shock stresses, etc. In this study, using the aluminum-magnesium alloy as an example of widely spread metallic materials, we show that a combination of functional nanoengineering and nanosecond laser texturing with the appropriate treatment regimes can be successfully used to transform a metal into a superhydrophobic material with exceptional mechanical and chemical properties. It is demonstrated that laser chemical processing of the surface may be simultaneously used to impart multimodal roughness and to modify the composition and physicochemical properties of a thick surface layer of the substrate itself.

Structural flexibility of human α-dystroglycan.

Dystroglycan (DG), composed of α and β subunits, belongs to the dystrophin-associated glycoprotein complex. α-DG is an extracellular matrix protein that undergoes a complex post-translational glycosylation process. The bifunctional glycosyltransferase like-acetylglucosaminyltransferase (LARGE) plays a crucial role in the maturation of α-DG, enabling its binding to laminin.

Block and Gradient Copoly(2-oxazoline) Micelles: Strikingly Different on the Inside.

Herein, we provide a direct proof for differences in the micellar structure of amphiphilic diblock and gradient copolymers, thereby unambiguously demonstrating the influence of monomer distribution along the polymer chains on the micellization behavior. The internal structure of amphiphilic block and gradient co poly(2-oxazolines) based on the hydrophilic poly(2-methyl-2-oxazoline) (PMeOx) and the hydrophobic poly(2-phenyl-2-oxazoline) (PPhOx) was studied in water and water-ethanol mixtures by small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), static and dynamic light scattering (SLS/DLS), and H NMR spectroscopy. Contrast matching SANS experiments revealed that block copolymers form micelles with a uniform density profile of the core.

Octamer formation in lysozyme solutions at the initial crystallization stage detected by small-angle neutron scattering.

Solutions of lysozyme in heavy water were studied by small-angle neutron scattering (SANS) at concentrations of 40, 20 and 10 mg ml with and without the addition of precipitant, and at temperatures of 10, 20 and 30°C. In addition to the expected protein monomers, dimeric and octameric species were identified in solutions at the maximum concentration and close to the optimal conditions for crystallization. An optimal temperature for octamer formation was identified and both deviation from this temperature and a reduction in protein concentration led to a significant decrease in the volume fractions of octamers detected.

A Spring-Loaded Mechanism Governs the Clamp-like Dynamics of the Skp Chaperone.

The trimeric periplasmic holdase chaperone Skp binds and stabilizes unfolded outer membrane proteins (OMPs) as part of bacterial OMP biogenesis. Skp binds client proteins in its central cavity, thereby reducing its backbone dynamics, but the molecular mechanisms that govern Skp dynamics and adaptation to differently sized clients remains unknown. Here, we employ a combination of microsecond timescale molecular dynamics simulation, small-angle X-ray scattering, and nuclear magnetic resonance spectroscopy to reveal that Skp is remarkably flexible, and features a molecular spring-loaded mechanism in its "tentacle" arms that enables switching between two distinct conformations on sub-millisecond timescales.

Crystal structure of recombinant phosphoribosylpyrophosphate synthetase 2 from Thermus thermophilus HB27 complexed with ADP and sulfate ions.

Phosphoribosylpyrophosphate synthetase (PRPPS) from the thermophilic bacterial strain Thermus thermophilus HB27 catalyzes the synthesis of phosphoribosylpyrophosphate from ribose 5-phosphate and ATP, and belongs to the class I PRPPSs. The three-dimensional structure of the recombinant enzyme was solved at 2.2 Å resolution using crystals grown in microgravity from protein solution containing ATP, magnesium and sulfate ions.

Activity modulation of the oligopeptidase B from Serratia proteamaculans by site-directed mutagenesis of amino acid residues surrounding catalytic triad histidine.

Oligopeptidase B (OpdB; EC 3.4.21.

Isolated Potato Virus A coat protein possesses unusual properties and forms different short virus-like particles.

In our previous study, we have observed that the isolated coat proteins (CP) of the Potyvirus Potato Virus A (PVA) virions exhibit an intrinsic tendency to self-associate into various multimeric forms containing some fractions of cross-β-structure. In this report, we studied the effect of solution conditions on the structure and dissociation of isolated PVA CP using a number of complementary physicochemical methods. Analysis of the structure of PVA CP in solution was performed by limited proteolysis with MALDI-TOF mass spectrometry analysis, transmission electron microscopy, intrinsic fluorescence spectroscopy, and synchrotron small angle X-ray scattering (SAXS).

AFM reconstruction of complex-shaped chiral plasmonic nanostructures.

A significant part of the optical metamaterial phenomena has the plasmonic nature and their investigation requires very accurate knowledge of the fabricated structures shape with a focus on the periodical features. We describe a consistent approach to the shape reconstruction of the plasmonic nanostructures. This includes vertical and tilted spike AFM probes fabrication, AFM imaging and specific post-processing.

Ordering of anisotropic nanoparticles in diblock copolymer lamellae: Simulations with dissipative particle dynamics and a molecular theory.

Local distribution and orientation of anisotropic nanoparticles in microphase-separated symmetric diblock copolymers has been simulated using dissipative particle dynamics and analyzed with a molecular theory. It has been demonstrated that nanoparticles are characterized by a non-trivial orientational ordering in the lamellar phase due to their anisotropic interactions with isotropic monomer units. In the simulations, the maximum concentration and degree of ordering are attained for non-selective nanorods near the domain boundary.

Incommensurately modulated twin structure of nyerereite NaKCa(CO).

The incommensurately modulated twin structure of nyerereite NaKCa(CO) has been first determined in the (3 + 1)-dimensional symmetry group Cmcm(α00)00s with modulation vector q = 0.383a*. Unit-cell values are a = 5.

Structure of the carboxypeptidase B complex with N-sulfamoyl-L-phenylalanine - a transition state analog of non-specific substrate.

Carboxypeptidase B (EC 3.4.17.

Topological Quantum Phase Transition and Superconductivity Induced by Pressure in the Bismuth Tellurohalide BiTeI.

A pressure-induced topological quantum phase transition has been theoretically predicted for the semiconductor bismuth tellurohalide BiTeI with giant Rashba spin splitting. In this work, evolution of the electrical transport properties in BiTeI and BiTeBr is investigated under high pressure. The pressure-dependent resistivity in a wide temperature range passes through a minimum at around 3 GPa, indicating the predicted topological quantum phase transition in BiTeI.

Acoustic streaming in two-dimensional freely suspended smectic liquid crystal films.

We study horizontal streaming excited by means of a low-frequency and low-intensity acoustic wave in 2D freely suspended films of thermotropic smectic liquid crystals. Acoustic pressure induces fast periodic transverse oscillations of the film, which produce in-plane stationary couples of vortices slowly rotating in opposite directions owing to hydrodynamic nonlinearity. The parameters of the vortices are measured using a new method, based on tracking solidlike disk-shaped islands.

Re-entrant cholesteric phase in DNA liquid-crystalline dispersion particles.

In this research, we observe and rationalize theoretically the transition from hexagonal to cholesteric packing of double-stranded (ds) DNA in dispersion particles. The samples were obtained by phase exclusion of linear ds DNA molecules from water-salt solutions of poly(ethylene glycol)-PEG-with concentrations ranging from 120 mg ml to 300 mg ml. In the range of PEG concentrations from 120 mg ml to 220 mg ml at room temperature, we find ds DNA molecule packing, typical of classical cholesterics.

Spatial distribution and nematic ordering of anisotropic nanoparticles in lamellae and hexagonal phases of block copolymers.

Orientational and translational ordering of anisotropic nanoparticles in the lamellae and hexagonal phases of diblock copolymers have been considered theoretically in the case of strong segregation taking into account the anisotropic interaction between the nanoparticles and the monomers in different blocks. It has been shown that anisotropic nanoparticles are orientationally ordered in the boundary region between the blocks and the nematic order parameter possesses opposite signs in different blocks: the nanoparticles align parallel to the boundary in one block and perpendicular to it in the other. In the hexagonal phase, a weak biaxial ordering of nanoparticles is also induced in the boundary region.

Design of a multilayer-based collimated plane-grating monochromator for tender X-ray range.

Collimated plane-grating monochromators (cPGMs), consisting of a plane mirror and plane diffraction grating, are essential optics in synchrotron radiation sources for their remarkable flexibility and good optical characteristics in the soft X-ray region. However, the poor energy transport efficiency of a conventional cPGM (single-layer-coated) degrades the source intensity and leaves reduced flux at the sample, especially for the tender X-ray range (1-4 keV) that covers a large number of K- and L-edges of medium-Z elements, and M-edges of high-Z elements. To overcome this limitation, the use of a multilayer-based cPGM is proposed, combining a multilayer-coated plane mirror with blazed multilayer gratings.

More Than 50 Years after Its Discovery in SiO Octahedral Coordination Has Also Been Established in SiS at High Pressure.

SiO exhibits a high-pressure-high-temperature polymorphism, leading to an increase in silicon coordination number and density. However, for the related compound SiS such pressure-induced behavior has not been observed with tetrahedral coordination yet. All four crystal structures of SiS known so far contain silicon with tetrahedral coordination.

Rapid automated superposition of shapes and macromolecular models using spherical harmonics.

A rapid algorithm to superimpose macromolecular models in Fourier space is proposed and implemented (). The method uses a normalized integrated cross-term of the scattering amplitudes as a proximity measure between two three-dimensional objects. The reciprocal-space algorithm allows for direct matching of heterogeneous objects including high- and low-resolution models represented by atomic coordinates, beads or dummy residue chains as well as electron microscopy density maps and inhomogeneous multi-phase models ( of protein-nucleic acid complexes).