saxs

Localized surface plasmon resonance (LSPR) effect relies on the shape, size, and dispersion state of metal nanoparticles and can potentially be employed in many applications such as chemical/biological sensor, optoelectronics, and photocatalyst. While complicated synthetic approaches changing shape and size of nanoparticles can control the intrinsic LSPR effect, here we show that controlling interparticle interactions with silica-coated gold nanoparticles (Au@SiO2 NPs) is a powerful approach, permitting wide range of optical bandwidth of gold nanoparticles with great stability...

Pathogen avoidance behaviors are found throughout the animal kingdom and are important for animal's survival in nature. As a free-living nematode, C. elegans is exposed to a variety of microorganisms, including toxic or pathogenic bacteria, in soil. C. elegans can develop efficient avoidance responses to pathogenic bacteria to minimize the infection risk. However, the role of microRNAs (miRNAs) in pathogen avoidance in C. elegans remains unclear. In this report, we showed that the miRNA mir-67 was involved in a behavioral avoidance response to P...

In this study, cellulose-II nanospheres (CNS) were extracted from flax fibers and analyzed to understand the crystalline, functional and morphological properties by means of X-ray Diffraction (X-RD), Fourier Transform Infrared (FT-IR) and Scanning Electron Microscopy (SEM). FT-IR and SEM results indicate the effective removal of extractives, lignin and hemicellulose. X-RD results clearly show the transformation from cellulose-I to cellulose-II during the mercerization process. Further, the resulting cellulose fibers were treated with sulfuric acid in order to obtain cellulose nanospheres (CNS)...

By combining NMR (yielding 1H chemical shift, spin relaxation and self-diffusion data) and SAXS experiments, we investigate the complex temperature dependence of the molecular and aggregate states in aqueous solutions of the surfactant [CH3(CH2)17(OCH2CH2)20OH], abbreviated C18E20, and hexamethyldisiloxane HMDSO. The latter molecule serves as a model for hydrophobic solubilizates. Previously, the pure micellar solution was demonstrated to exhibit core freezing at approx. 7-8 °C. At room temperature, we find that HMDSO solubilizes at a volume fraction of approx...

Protein biosensors are widely used for the monitoring of metabolite concentration and enzymatic activities inside living cells and in in vitro applications. Neutrophil elastase (NE) is a serine protease of relevance in inflammatory diseases whose activity can lead to pathological conditions if unregulated. This study focuses on the structural characterization of a biosensor for NE activity based on Förster resonance energy transfer (FRET). The cleavage by NE results in dissociation of the FRET fluorescent protein pair and alteration of the fluorescent emission spectrum...

Small-angle X-ray scattering is an increasingly popular technique used to detect protein structures and ensembles in solution. However, the refinement of structures and ensembles against SAXS data is often ambiguous due to the low information content of SAXS data, unknown systematic errors, and unknown scattering contributions from the solvent. We offer a solution to such problems by combining Bayesian inference with all-atom molecular dynamics simulations and explicit-solvent SAXS calculations. The Bayesian formulation correctly weights the SAXS data versus prior physical knowledge, it quantifies the precision or ambiguity of fitted structures and ensembles, and it accounts for unknown systematic errors due to poor buffer matching...

Rotation of the bacterial flagellum is powered by a proton influx through the peptidoglycan (PG)-tethered stator ring MotA/B. MotA and MotB form an inner-membrane complex that does not conduct protons and does not bind to PG until it is inserted into the flagellar motor. The opening of the proton channel involves association of the plug helices in the periplasmic region of the MotB dimer into a parallel coiled coil. Here, we have characterised the structure of a soluble variant of full-length Helicobacter pylori MotB in which the plug helix was engineered to be locked in a parallel coiled coil state, mimicking the open state of the stator...

Here we recount the standard two-level model that describes saturated excitation (SAX) in multiphoton microscopy (MPM), a new technique for super-resolution fluorescence microscopy in scattering tissue, which requires no special chemistry and only simple modifications to a commercial MPM microscope. We use the model to study conditions required for improvements in MPM SAX resolution and experimental implementation strategies. Simulation results find zeros, or nodes, in the frequency response, which generate highly irregular point-spread functions (PSFs), such as rings and ripples, that contain spatial frequency content >3× larger than allowed by diffraction...

Polypeptides and polynucleotides are natural programmable biopolymers that can self-assemble into complex tertiary structures. We describe a system analogous to designed DNA nanostructures in which protein coiled-coil (CC) dimers serve as building blocks for modular de novo design of polyhedral protein cages that efficiently self-assemble in vitro and in vivo. We produced and characterized >20 single-chain protein cages in three shapes-tetrahedron, four-sided pyramid, and triangular prism-with the largest containing >700 amino-acid residues and measuring 11 nm in diameter...

Background: The US National HIV/AIDS Strategy (NHAS) aims for 72% (90% diagnosed times 80% of those virally suppressed) viral suppression among persons with human immunodeficiency virus (HIV) by 2020. We examined the clinical and economic impact of reaching this target, in the general US population and among black men who have sex with men (MSM), the group with the highest HIV prevalence. Methods: Using a mathematical simulation, we project the 5- and 20-year clinical outcomes, costs, and incremental cost-effectiveness ratios for (1) Current Pace of detection, linkage, retention, and virologic suppression and (2) NHAS investments in expanded testing ($24-$74 per test) and adherence ($400 per person-year), calibrated to achieve 72% suppression by 2020...

Studies on supramolecular gel aggregates via supramolecular interactions are very fascinating and impressive. The interactions of gelator with solvent and inorganic salt can functionalize, activate, or control the properties of supramolecular gels. A lot of work on this area has been done, but all these contributions are only at an early stage. In this work, we tuned the gel formation conditions and properties by using low-molecular-weight gelator (LMWGs), amide-functionalized imidazolium-based surfactant, viz...

In situ gels containing sinomenine hydrochloride (SMH) for intra-articular (IA) administration to treat rheumatoid arthritis (RA) were designed and investigated in this study. Glycerol monooleate (GMO) was used due to the potential to generate viscous crystalline phase structures upon water absorption. The gels were evaluated using different parameters: syringeability, gelation, viscosity, and drug release. And, polarized light microscopy (PLM), small-angle X-ray scattering investigation (SAXS), and rheological studies were used to analyze their internal structures...

Bilirubin acts as a potent endogenous antioxidant, with higher concentrations associated with lower rates of CVD; the antiretroviral drug atazanavir (ATV) increases bilirubin levels but may also increase von Willebrand factor levels. We tested the hypothesis that increasing endogenous bilirubin using ATV would improve cardiometabolic risk factors and vascular function in older patients with HIV. Ninety participants were enrolled in two study protocols. In protocol 1, we evaluated markers of inflammation, thrombosis, and conduit artery endothelial function in subjects on non-ATV containing regimens...

BioXTAS RAW is a graphical-user-interface-based free open-source Python program for reduction and analysis of small-angle X-ray solution scattering (SAXS) data. The software is designed for biological SAXS data and enables creation and plotting of one-dimensional scattering profiles from two-dimensional detector images, standard data operations such as averaging and subtraction and analysis of radius of gyration and molecular weight, and advanced analysis such as calculation of inverse Fourier transforms and envelopes...

This paper presents the first worldwide inter-laboratory comparison of small-angle X-ray scattering (SAXS) for nanoparticle sizing. The measurands in this comparison are the mean particle radius, the width of the size distribution and the particle concentration. The investigated sample consists of dispersed silver nanoparticles, surrounded by a stabilizing polymeric shell of poly(acrylic acid). The silver cores dominate the X-ray scattering pattern, leading to the determination of their radius size distribution using (i) the generalized indirect Fourier transformation method, (ii) classical model fitting using SASfit and (iii) a Monte Carlo fitting approach using McSAS...

The structures of micelles and microemulsions consisting of polyglycerol polyricinoleate (PGPR) were investigated by small-angle X-ray scattering (SAXS) and rheological measurements. The SAXS results show that amphiphilic PGPR molecules form stable micelles in glycerol. When vitamin E is added to the PGPR micelles, it is encapsulated in the micelles and forms an emulsion. These micelles are stable towards mechanical shearing up to a shear rate of 1000 s(-1), with shear thinning occurring in the emulsion above 100 s(-1), indicating that the emulsion may undergo break up by shearing, but recovers the structure by releasing shear strain...

A novel preparation route for layered hydroxide based hybrid phases has been investigated combining the polyol route with the in situ generation of inorganic platelets, in the presence of an amphiphilic polymer as well as bola-amphiphiles. The polyol route consists of hydrolysis in an alcoholic medium containing acetate metal cations as precursor(s), to yield an LDH Zn2Al cation composition or LSH-Zn (layered single hydroxide). A bola amphiphile is described as hydrophobic polymer segment-telechelic-chains terminated by two anionic hydrophilic end groups, using volatile ammonium cations as counter ions...

Heterogeneity of protein glycosylation poses great challenges for analysis that is key to understand structure and function of glycoproteins. Resolving this conundrum requires efficient and specific enrichment of intact glycopeptides for identification and quantitation. To this end, hydrophilic interaction chromatography (HILIC) has been commonly used to enrich intact N- and O-linked glycopeptides. However, its effectiveness to enrich isobarically labeled glycopeptides remains unclear. Here, we studied three different enrichment methods for enrichment of N- and O-linked glycopeptides...

Due to their lower production cost compared with monoclonal antibodies, single-chain variable fragments (scFvs) have potential for use in several applications, such as for diagnosis and treatment of a range of diseases, and as sensor elements. However, the usefulness of scFvs is limited by inhomogeneity through the formation of dimers, trimers, and larger oligomers. The scFv protein is assumed to be in equilibrium between the closed and open states formed by assembly or disassembly of VH and VL domains. Therefore, the production of an scFv with equilibrium biased to the closed state would be critical to overcome the problem in inhomogeneity of scFv for industrial or therapeutic applications...

The structural behavior in aqueous mixtures of negatively charged silver nanoparticles (Ag NPs) together with the cationic surfactants cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium chloride (DTAC), respectively, has been investigated using SANS and SAXS. From our SANS data analysis we are able to conclude that the surfactants self-assemble into micellar clusters surrounding the Ag NPs. We are able to quantify our results by means of fitting experimental SANS data with a model based on cluster formation of micelles with very good agreement...