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Bile acids (BA), with their large hydrophobic steroid nucleus and polar groups are amphipathic molecules. In bile, these exist as micelles above their critical micellar concentration (CMC). In blood at low concentrations, these exist as monomers, initiating cellular signals. This micellar to monomer transition may involve complex thermodynamic interactions between bile salts alone or with phospholipids, i.e. mixed micelles and the aqueous environment. We therefore went on to test if therapeutically relevant changes in temperature could influence micellar behavior of bile salts, and in turn whether this affected the biological responses in cells, and in vivo. Sodium taurocholate (STC) belongs to a major class of bile salts. STC has a CMC in the 5–8 mM range and its infusion into the pancreatic duct is commonly used to study pancreatitis. We thus studied micellar breakdown of STC using isothermal titration calorimetry (ITC), dynamic light scattering and cryogenic transmission electron microscopy. Under conditions relevant to the in vivo environment (pH 7.4, Na 0.15 M), ITC showed STC to have a U shaped reduction in micellar breakdown between 37 °C and 15 °C with a nadir at 25 °C approaching ≈90% inhibition. This temperature dependence paralleled pancreatic acinar injury induced by monomeric STC. Mixed micelles of STC and 1-palmitoyl, 2-oleyl phosphatidylcholine, a phospholipid present in high proportions in bile, behaved similarly, with ≈75% reduction in micellar breakdown at 25 °C compared to 37 °C. In vivo pancreatic cooling to 25 °C reduced the increase in circulating BAs after infusion of 120 mM (5%) STC into the pancreatic duct, and duct ligation. Lower BA levels were associated with improved cardiac function, reduced myocardial damage, shock, lung injury and improved survival independent of pancreatic injury. Thus micellar breakdown of bile salts is essential for their entry into the systemic circulation, and thermodynamic interference with this may reduce their systemic entry and consequent injury during cholestasis, such as from biliary pancreatitis.

In this work, a water-soluble gold nanoparticle-encapsulated polyaniline nanocomposite (AuNP-PANI) was prepared in the presence of an ionic surfactant such as cetyltrimethylammonium bromide (CTAB) using versatile two steps method. The prepared nanoparticles (AuNPs) were characterized by UV–Visible spectroscopy, Transmission Electron Microscope (TEM) and Dynamic Light Scattering (DLS). The nanocomposite (AuNP-PANI) were initially characterized using UV–Visible spectroscopy, Transmission Electron Microscope (TEM), Scanning Transmission Electron Microscope (STEM) and DLS. The structure and composition of AuNP-PANI further characterized using Fourier Transmission Infrared Spectroscopy (FTIR), X-ray diffraction study (XRD), Energy Dispersive X-ray Spectroscopy (EDS) and Thermogravimetric analysis (TGA). Electrochemical properties of AuNP-PANI were studied using Cyclic Voltammetry (CV). The prepared nanocomposite exhibited good surface enhanced Raman scattering (SERS) of 4-amino thiophenol (4-ATP) and 4- (dimethyl amino) pyridine (4-DMAP) for which the enhancement factor (EF) were found to be1.95 × 105 and 2.016 × 105, respectively. The nanocomposite also showed excellent catalytic activity for the chemical degradation of Congo red (CR) and methylene blue (MB) as evidenced from the calculated rate constants which were determined to be 0.30 s−1 and 0.33 s−1, respectively. Keywords: Gold nanoparticle-polyaniline nanocomposite, Cetyltrimethylammonium bromide, Surface enhanced Raman scattering, Catalytic activity, Organic dye

Protic ionic liquids (PILs) are made by proton transfer from a Bronsted acid to a base and are of interest for their solvent and electrolyte properties such as high ionic conductivity. Unfortunately, many PILs have been misnamed, because their ionic content is minimal due to an insufficient driving force for the proton transfer. Here we review this problem and introduce a new method, using 15N NMR spectroscopy, of characterizing the relation between the extent of proton transfer to a given base and the strength of the proton-donating acid. The experimental data reveal a sigmoid "titration type" curve that indicates clearly the acid strength, at which molecule bases, of substituted pyridine type, are fully protonated. We compare results for two bases of similar shape but different basicity, protonated by equimolar amounts of the different acids. The extent of protonation is also reflected in the ionic conductivity, and we show that the important part of the protonation sigmoid is quantitatively reproduced by data for conductivity and viscosity displayed in the form of a Walden plot (log equivalent conductivity vs log fluidity). The acid strength, for this study, is based on gas phase proton affinities, but we note that a similar sigmoid is obtained if we use the condensed phase Hammett acidity functions instead. Our findings allow us to rank the AlCl4- anion as the weakest proton acceptor in use in IL studies, consistent with its role in the most conductive ILs.

Many natural silks produced by spiders and insects are unique materials in their exceptional toughness and tensile strength, while being lightweight and biodegradable–properties that are currently unparalleled in synthetic materials. Myriad approaches have been attempted to prepare artificial silks from recombinant spider silk spidroins but have each failed to achieve the advantageous properties of the natural material. This is because of an incomplete understanding of the in vivo spidroin-to-fiber spinning process and, particularly, because of a lack of knowledge of the true morphological nature of spidroin nanostructures in the precursor dope solution and the mechanisms by which these nanostructures transform into micrometer-scale silk fibers. Herein we determine the physical form of the natural spidroin precursor nanostructures stored within spider glands that seed the formation of their silks and reveal the fundamental structural transformations that occur during the initial stages of extrusion en route to fiber formation. Using a combination of solution phase diffusion NMR and cryogenic transmission electron microscopy (cryo-TEM), we reveal direct evidence that the concentrated spidroin proteins are stored in the silk glands of black widow spiders as complex, hierarchical nanoassemblies (∼300 nm diameter) that are composed of micellar subdomains, substructures that themselves are engaged in the initial nanoscale transformations that occur in response to shear. We find that the established micelle theory of silk fiber precursor storage is incomplete and that the first steps toward liquid crystalline organization during silk spinning involve the fibrillization of nanoscale hierarchical micelle subdomains.

Gold nanoparticles have attracted considerable attention in recent research because of their wide applications in various fields such as material science, electrical engineering, physical science, and biomedical engineering. Researchers have developed many methods for synthesizing different kinds of gold nanoparticles, where the sizes and surface chemistry of the nanoparticles are considered to be the two key factors. Traditionally, the sizes of nanoparticles are determined by electron microscopy whereas the surface chemistry is characterized by optical spectroscopies such as infrared spectroscopy and Raman spectroscopy. Compared with that, nuclear magnetic resonance (NMR) spectroscopy provides a more advanced and convenient way for size determination and surface chemistry investigations by combining one- and multiple-dimensional NMR spectroscopy and diffusion-order NMR spectroscopy. Here, we show a thorough study that NMR spectroscopy can be applied to characterize small thiol-protected gold nanoparticles, including size determination, surface chemistry investigation, and structural study. The results show that the nanoparticles' sizes determined by NMR agree well with transmission electron microscopy results. Furthermore, the ligand densities of nanoparticles were determined by quantitative NMR spectroscopy, and the structures of ligands capped on the surfaces were studied thoroughly by one- and multiple-dimensional NMR spectroscopy. In this work, we establish a general method for researchers to characterize nanostructures by using NMR spectroscopy.

In this work, thermal condensation of alanine adsorbed on fumed silica nanoparticles is investigated using thermal analysis and multiple spectroscopic techniques, including infrared (IR), Raman, and nuclear magnetic resonance (NMR) spectroscopies. Thermal analysis shows that adsorbed alanine can undergo thermal condensation, forming peptide bonds within a short time period and at a lower temperature (∼170 °C) on fumed silica nanoparticle surfaces than that in bulk (∼210 °C). Spectroscopic results further show that alanine is converted to alanine anhydride with a yield of 98.8% during thermal condensation. After comparing peptide formation on solution-derived colloidal silica nanoparticles, it is found that fumed silica nanoparticles show much better efficiency and selectivity than solution-derived colloidal silica nanoparticles for synthesizing alanine anhydride. Furthermore, Raman spectroscopy provides evidence that the high efficiency for fumed silica nanoparticles is likely related to their unique surface features: the intrinsic high population of strained ring structures present at the surface. This work indicates the great potential of fumed silica nanoparticles in synthesizing peptides with high efficiency and selectivity.

Solid acids as a class are of much interest in areas such as acid catalysis, and exotic protonation chemistries. They include the strongest acids yet identified. A subclass exhibits very high protonic conductivity and its members have been investigated as possible fuel cell electrolytes, as first demonstrated by Haile's group in 2001 with CsHSO4. These superprotonic plastic crystals bring a “true solid state” alternative to polymer electrolytes, operating at mild temperatures (150–200 °C) without the requirement of humidification. However, they suffer from the narrow operating temperature range, and other problems. Here we describe a new class of solid acids based on silicon, which are of general interest. Its members have extraordinary conductivities, as high as 21.5 mS cm−1 at room temperature, orders of magnitude above any previous reported case. We discuss possible applications. Although the present electrolytes are not suitable for H2/O2 fuel cell applications due to hydrolizable components, a proof of principle short term fuel cell test is shown to produce a maximum (short circuit) current of 640 mA cm−2 at 87 °C despite a low open circuit voltage.

Background Many pipeline drugs have low solubility in their crystalline state and require compounding in special dosage forms to increase bioavailability for oral administration. The use of amorphous formulations increases solubility and uptake of active pharmaceutical ingredients. These forms are rapidly gaining commercial importance for both pre-clinical and clinical use. Methods Synthesis of amorphous drugs was performed using an acoustic levitation containerless processing method and spray drying. The structure of the products was investigated using in-situ high energy X-ray diffraction. Selected solvents for processing drugs were investigated using acoustic levitation. The stability of amorphous samples was measured using X-ray diffraction. Samples processed using both spray drying and containerless synthesis were compared. Results We review methods for making amorphous pharmaceuticals and present data on materials made by containerless processing and spray drying. It was shown that containerless processing using acoustic levitation can be used to make phase-pure forms of drugs that are known to be difficult to amorphize. The stability and structure of the materials was investigated in the context of developing and making clinically useful formulations. Conclusions Amorphous compounds are emerging as an important component of drug development and for the oral delivery of drugs with low solubility. Containerless techniques can be used to efficiently synthesize small quantities of pure amorphous forms that are potentially useful in pre-clinical trials and for use in the optimization of clinical products. General significance Developing new pharmaceutical products is an essential enterprise to improve patient outcomes. The development and application of amorphous pharmaceuticals to increase absorption is rapidly gaining importance and it provides opportunities for breakthrough research on new drugs. There is an urgent need to solve problems associated with making formulations that are both stable and that provide high bioavailability. This article is part of a Special Issue entitled “Science for Life” Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazu and Dr. Federica Migliardo.

Iridium oxide (IrOx) is one of the best water splitting electrocatalysts, but its active site details are not well known. As with all heterogeneous catalysts, a strategy for counting the number of active sites is not clear, and understanding their nature and structure is remarkably difficult. In this work, we performed a combined study using optical spectroscopy, magnetic resonance and electrochemistry to characterize the interaction of IrOx nanoparticles (NPs) with a probe molecule, catechol. The catalyst is heterogeneous given that the substrate is in a different phase, but behaves as a homogeneous catalyst from the point of view of electrochemistry since it remains in colloidal suspension. We find two types of binding sites: centers A which bind catechol irreversibly making up 21% of the surface, and centers B which bind catechol reversibly making up 79% of the surface. UV-vis absorption spectroscopy shows that the A sites are responsible for the characteristic blue color of the NPs. Electrochemical experiments indicate that the B sites are catalytically active and we give the number of active sites per nanoparticle. We conclude by performing a survey of ligands used in solar cell architectures and show which ones bind well to the surface and which ones inhibit the catalytic activity when doing so, presenting quantitative guidelines for the correct handling of IrOx nanoparticles during their incorporation into multifunctional solar energy harvesting architectures. We suggest ligands binding on the surface oxygen atoms allow for large bound ligand densities with no detrimental effect on the catalytic activity.

Silk is a protein-based natural polymer that has attracted considerable attention in recent research due to its outstanding mechanical properties and broad applications in biomedical research. This chapter presents an overview of NMR techniques used for elucidating the molecular structures and dynamics of silk, with a primary focus on silkworm silk, spider silk, and silk-mimic peptides. The rapid NMR technology development allows opportunities not only for characterizing structures of silk materials at high molecular/atomic resolution, but also for studying the silk protein dynamics and structural transition of silk protein in vivo and in vitro In this chapter, several recently developed NMR techniques along with classical techniques are discussed.

High-energy photon diffraction minimizes many of the corrections associated with laboratory x-ray diffractometers, and enables structure factor measurements to be made over a wide range of momentum transfers. The method edges us closer toward an ideal experiment, in which coordination numbers can be extracted without knowledge of the sample density. Three case studies are presented that demonstrate new hard x-ray methods for studying the structure of glassy and amorphous materials. First, the methodology and analysis of high-energy grazing incidence on thin films is discussed for the case of amorphous In2O3. The connectivity of irregular InO6 polyhedra are shown to exist in face-, edge- and corner-shared configurations in the approximate ratio of 1:2:3. Secondly, the technique of high-energy small and wide angle scattering has been carried out on laser heated and aerodynamically levitated samples of silica-rich barium silicate (20BaO:80SiO2), from the single phase melt at 1500 oC to the phase separated glass at room temperature. Based on Ba–O coordination numbers of 6 to 7, it is argued that the although the potential of Ba is ionic, it is weak enough to cause the liquid–liquid immiscibility to become metastable. Lastly, high-energy small and wide angle scattering has also been applied to high water content (up to 12 wt.%) samples of hydrous SiO2 glass quenched from 1500 oC at 4 GPa. An increase of Si1–O2 correlations at 4.3 Å is found to be consistent with an increase in the population of three-membered SiO4 rings at the expense of larger rings.

Catechol on TiO2 is a model system for a class of molecules that bind and interact very strongly with metal oxides. This interaction gives rise to a marked charge-transfer absorption band that can be used to sensitize the complex to visible light. In solar cells, these are called type II sensitizers in contrast with type I sensitizers where an excitation of the molecule with subsequent charge injection is the main mechanism for placing an electron in the conduction band of the semiconductor. The adsorption geometry of these molecules is critical in their functioning. Nuclear magnetic resonance (NMR) spectroscopic methods can be used to elucidate structural information about the local geometry at the substrate–molecule interface. NMR methods coupled with density functional theory (DFT) allow for the detailed characterization of molecular binding modes. In the present work, we report a solid-state NMR and DFT study of catechol on TiO2. DFT-GIPAW chemical shift predictions for the 13C CP-MAS experiments unam...

Cacti thrive in xeric environments through specialized water storage and collection tactics such as a shallow, widespread root system that maximizes rainwater absorption and spines adapted for fog droplet collection. However, in many cacti, the epidermis, not the spines, dominates the exterior surface area. Yet, little attention has been dedicated to studying interactions of the cactus epidermis with water drops. Surprisingly, the epidermis of plants in the genus Opuntia, also known as prickly pear cacti, has water-repelling characteristics. In this work, we report that surface properties of cladodes of 25 taxa of Opuntia grown in an arid Sonoran climate switch from water-repelling to superwetting under water impact over the span of a single season. We show that the old cladode surfaces are not superhydrophilic, but have nearly vanishing receding contact angle. We study water drop interactions with, as well as nano/microscale topology and chemistry of, the new and old cladodes of two Opuntia species and use this information to uncover the microscopic mechanism underlying this phenomenon. We demonstrate that composition of extracted wax and its contact angle do not change significantly with time. Instead, we show that the reported age dependent wetting behavior primarily stems from pinning of the receding contact line along multilayer surface microcracks in the epicuticular wax that expose the underlying highly hydrophilic layers.

At the MRS Fall 2014 Meeting, Symposium E, we reported on morphologies, fragmentation, and hardness in synthetic hydrogen urate monohydrate (monosodium urate monohydrate, MSUM, or MSU) crystals. We are now presenting further characterization results, including some from the biomaterial that forms in humans with gout disease: The fanning of radiating blades (needles) in spherulitic grains of synthetic MSUM was examined by microscopy techniques. These and previous data are consistent with an interpretation in terms of the crystallographic parameters in the unit cell, and the presence of dislocation arrays at low angle boundaries. The kinetics of such branched growth is here related to thermodynamic properties and super-saturation levels. Secondary nucleation is an additional mechanism leading to more complex morphologies. Differences in overall growth rates, under conditions of either branched or single needle growth, are considered in relation to gout. Novel powder XRD and solid state NMR data show, respectively, preferred orientation in the biomaterial, and the potential of NMR for identifying and characterizing MSUM in specific environments, helping to resolve pending questions in gout. Present results are anticipated to be useful for designing bio-inspired and bio-mimetic materials, regarding morphologies, overall growth rates, and mechanical properties.

The ionicity and transport properties of a series of diethylmethylamine (DEMA) based protic ionic liquids (PILs) were characterized, principally utilizing nuclear magnetic resonance (NMR) spectroscopy. PILs were formed via the protonation of DEMA by an array of acids spanning a large range of acidities. A correlation between the (1)H chemical shift of the exchangeable proton and the acidity of the acid used for the synthesis of the PIL was observed. The gas phase proton affinity of the acid was found to be a better predictor of the extent of proton transfer than the commonly used aqueous ΔpKa. Pulsed field gradient (PFG) NMR was used to determine the diffusivity of the exchangeable proton in a subset of the PILs. The exchangeable proton diffuses with the acid if the PIL is synthesized with a weak acid, and with the base if a strong acid is used. The ionicity of the PILs was characterized using the Walden analysis and by comparing to the ideal Nernst-Einstein conductivity predicted from the (1)H PFG-NMR results.

The search for fuel cell membranes has focused on carbon backbone polymers, among which Nafion seems to best survive the most severe of the degradation mechanisms – attack by peroxide radicals. Less attention has been given to inorganic membranes because of their generally inflexible nature and lower conductivity, though some SiO 2 -Nafion composites have shown improved properties. Nafion dominates, despite needing hydration, which then restricts operation to below 100 °C (so CO poisoning problems persist). Described herein is a low cost, flexible, and all-inorganic fiberglass reinforced gel membrane with conductivity exceeding that of Nafion at any temperature above 60 °C. Using Teflon fuel cells, maximum currents > 1 Acm −2 and OCV of 1.03 V at 150 °C are demonstrated. No detectable loss of cell potential was observed over 24 h during 50 mAcm −2 constant current operation at 120 °C while, at 150 °C and maximum power, the degradation rate is intermediate among other high conductivity H 3 PO 4 -PBI type membranes. The structure of the membrane is deduced, mainly from 29 Si solid state-NMR. The −115 ppm resonance, which is extreme for Q 4 Si(O) structures, identifies a zeolite-like SiO 2 network, which is “floppy”. 31 P and 1 H NMR establish nano-permeating H 3 PO 4 as the source of the exceptional conductivity.

Here we describe a dual detector system for high-energy X-ray, simultaneous, small and wide-angle X-ray scattering (SAXS and WAXS), designed to extract extended-range pair distribution functions (ER-PDF) for disordered materials. The hardware and software provides continuous reciprocal space coverage over atomic to nanometer length-scales. Details of the varying resolution, splicing of data and normalization on an absolute scale are outlined. In addition, the combination of SAXS and WAXS theory is considered with a view to enabling a direct Fourier transformation of the structure factor spanning multiple length-scales into real space. Important distinctions between the ER-PDF and the pair distance distribution function (PDDF) representations are demonstrated. It is shown that when the SAXS intensity in the structure factor, S(Q), is similar to the WAXS intensity, the contributions to the ER-PDF are minimal. However, when the SAXS S(Q) intensities are substantially stronger than the WAXS, the ER-PDF can provide important structural information on the local, intermediate and nanometer length-scales. Notably, the ER-PDF method provides direct information on particle sizes and their density distributions, overcoming the limitations of PDDF analysis for densely packed systems.

Tissue approximation and repair have been conventionally performed with sutures and staples, but these means are inherently traumatic. Tissue approximation using laser-responsive nanomaterials can lead to rapid tissue sealing and repair, and is an attractive alternative to existing clinical methods. Here, we demonstrate the use of laser-activated nanosealants (LANS) with gold nanorods (GNRs) embedded in silk fibroin polypeptide matrices. The adaptability of LANS for sealing soft tissues is demonstrated using two different modalities: insoluble thin films for internal, intestinal tissue repair, and semi-soluble pastes for external repair, shown by skin repair in live mice. Laser repaired intestinal tissue held over seven times more fluid pressure than sutured intestine and also prevented bacterial leakage. Skin incisions in mice closed using LANS’ showed indication of increased mechanical strength and faster repair compared to suturing. Laser-activated silk-GNR nanosealants rapidly seal soft-tissue tears and show high promise for tissue approximation and repair in trauma and routine surgery.

All spiders produce protein-based biopolymer fibres that we call silk. The most studied of these silks is spider dragline silk, which is very tough and relatively abundant compared with other types of spider silks. Considerable research has been devoted to understanding the relationship between the molecular structure and mechanical properties of spider dragline silks. In this Review, we overview experimental and computational studies that have provided a wealth of detail at the molecular level on the highly conserved repetitive core and terminal regions of spider dragline silk. We also discuss the role of the nanocrystalline β-sheets and amorphous regions in determining the properties of spider silk fibres, endowing them with strength and elasticity. Additionally, we outline imaging techniques and modelling studies that elucidate the importance of the hierarchical structure of silk fibres at the molecular level. These insights into structure–function relationships can guide the reverse engineering of spider silk to enable the production of superior synthetic fibres. Experimental and computational studies reveal numerous aspects of the molecular and hierarchical structure of spider silk and of its molecular dynamics. In this Review, we discuss the structure–function relationships of spider silk that can be elucidated from these studies and how this knowledge may enable the reverse engineering of spider silk.

Silkworm silk has attracted considerable attention in recent years due to its excellent mechanical properties, biocompatibility, and promising applications in biomedical sector. However, a clear understanding of the molecular structure and the relationship between the excellent mechanical properties and the silk protein sequences are still lacking. This study carries out a thorough comparative structural analysis of silk fibers of four silkworm species ( Bombyx mori, Antheraea pernyi, Samia cynthia ricini, and Antheraea assamensis). A combination of characterization techniques including scanning electron microscopy, mechanical test, synchrotron X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and NMR spectroscopy was applied to investigate the morphologies, mechanical properties, amino acid compositions, nanoscale organizations, and molecular structures of various silkworm silks. Furthermore, the structure-property relationship is discussed by correlating the molecular structural features of silks with their mechanical properties. The results show that a high content of β-sheet structures and a high crystallinity would result in a high Young's modulus for silkworm silk fibers. Additionally, a low content of β-sheet structures would result in a high extensibility.

A potential cathode material for lithium ion batteries has been developed using a boron polyanion substituted lithium iron manganese phosphate, LiFe0.4Mn0.6(PO4)1 − x(BO3)x (x = 0 to 0.03). Without any external carbon source, the material has been synthesized by solid-state reaction using ball-mill and was subsequently characterized by X-ray diffraction, scanning electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge measurement. The LiFe0.4Mn0.6(PO4)1 − x(BO3)x samples show a single-phase crystalline nature with X-ray diffraction analysis, and enhanced discharge capacity at various C-rates as compared to that of pure LiFe0.4Mn0.6PO4. Among several LiFe0.4Mn0.6(PO4)1 − x(BO3)x samples, LiFe0.4Mn0.6(PO4)0.995(BO3)0.005 demonstrated the best cycleability, exhibiting an initial discharge capacity of 159.4 mAh g− 1 at 0.1 C and 113 mAh g− 1 at 3 C. LiFe0.4Mn0.6(PO4)1 − x(BO3)x demonstrates enhanced electrochemical properties with excellent reversible cycling via boron polyanion substitution.

We synthesize monodispersed zwitterionic microgel (ZI-MG) particles that undergo an extensive, reversible change in volume in response to environmental stimuli such as pH and temperature. These aqueous ZI-MG dispersions exhibit a minimum hydrodynamic diameter value at an adjustable isoelectric point (IEP). In addition, the study elucidates the controlled uptake and release of ionic and nonionic surfactants from these particle systems. The extent of surfactant loading and the ensuing relative swelling/deswelling behaviors within the colloidal polymer networks are explained in terms of their binding interactions.

In this work, we present a novel rapid method for fabricating biocompatible, biodegradable gold nanoparticle-embedded silk films (AuNP–silk films) that have potential applications in bioengineering and biomedical research. Thin AuNP–silk films are prepared from a AuNP–silk nanocomposite and characterized by scanning electron microscopy (SEM), solid-state nuclear magnetic resonance (NMR) spectroscopy, and UV-visible spectroscopy. Results indicate that the size and distribution of AuNPs can be well controlled in AuNP–silk films, which may have great significance in developing novel biosensors. As a proof of principle, we further demonstrate that the prepared AuNP–silk films can serve as an excellent substrate for surface-enhanced Raman scattering in trace analysis. Moreover, the solid-state NMR results show that the AuNP–silk films possess a structure similar to natural silk, indicating that the fabrication process has little effect on silk protein. Surface plasmon absorption study of AuNPs shows that the optical properties of AuNPs vary when embedded into silk films because of the higher refractive index of silk, which is demonstrated by theoretical simulation.

Lithium-beryllium metal hydrides, which are structurally related to their parent compound, BeH2, offer the highest hydrogen storage capacity by weight among the metal hydrides (15.93 wt. % of hydrogen for LiBeH3). Challenging synthesis protocols have precluded conclusive determination of their crystallographic structure to date, but here we analyze directly the hydrogen hopping mechanisms in BeH2 and LiBeH3 using quasielastic neutron scattering, which is especially sensitive to single-particle dynamics of hydrogen. We find that, unlike its parent compound BeH2, lithium-beryllium hydride LiBeH3 exhibits a sharp increase in hydrogen mobility above 265 K, so dramatic that it can be viewed as melting of hydrogen sublattice. We perform comparative analysis of hydrogen jump mechanisms observed in BeH2 and LiBeH3 over a broad temperature range. As microscopic diffusivity of hydrogen is directly related to its macroscopic kinetics, a transition in LiBeH3 so close to ambient temperature may offer a straightforward and effective mechanism to influence hydrogen uptake and release in this very lightweight hydrogen storage compound.

Spider dragline silk is an outstanding biopolymer with a strength that exceeds steel by weight and a toughness greater than high-performance fibers like Kevlar. For this reason, understanding how a spider converts the gel-like, aqueous protein spinning dope within the major ampullate (MA) gland into a super fiber is of great importance for developing future biomaterials based on spider silk. In this work, the initial state of the silk proteins within Black Widow MA glands was probed with solution-state NMR spectroscopy. 15 N relaxation parameters, T 1 , T 2 and 15 N-{ 1 H} steady-state NOE were measured for twelve backbone environments at two spectrometer frequencies, 500 and 800 MHz. The NMR relaxation parameters extracted for all twelve environments are consistent with MA silk protein backbone dynamics on the fast sub-nanosecond timescale. Therefore, it is concluded that the repetitive core of spider MA proteins are in an unfolded, highly flexible state in the MA gland.

Nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) experiments reveal the structural importance of divalent cation-phosphate complexes in the formation of β-sheet nanocrystals from phosphorylated serine-rich regions within aquatic silk from caddisfly larvae of the species Hesperophyla consimilis. Wide angle XRD data on native caddisfly silk show that the silk contains a significant crystalline component with a repetitive orthorhombic unit cell aligned along the fiber axis with dimensions of 5.9 Å × 23.2 Å × 17.3 Å. These nanocrystalline domains depend on multivalent cations, which can be removed through chelation with ethylenediaminetetraacetic acid (EDTA). A comparison of wide angle X-ray diffraction data before and after EDTA treatment reveals that the integrated peak area of reflections corresponding to the nanocrystalline regions decreases by 15-25% while that of the amorphous background reflections increases by 20%, indicating a partial loss of crystallinity. (31)P solid-state NMR data on native caddisfly silk also show that the phosphorylated serine-rich motifs transform from a rigid environment to one that is highly mobile and water-solvated after treatment with EDTA. The removal of divalent cations through exchange and chelation has therefore caused a collapse of the β-sheet structure. However, NMR results show that the rigid phosphorus environment is mostly recovered after the silk is re-treated with calcium. The (31)P spin-lattice (T1) relaxation times were measured at 7.6 ± 3.1 and 1 ± 0.5 s for this calcium-recovered sample and the native silk sample, respectively. The shorter (31)P T1 relaxation times measured for the native silk sample are attributed to the presence of paramagnetic iron that is stripped away during EDTA chelation treatment and replaced with diamagnetic calcium.

Spider silk is a biomaterial with impressive mechanical properties, resulting in various potential applications. Recent research has focused on producing synthetic spider silk fibers with the same mechanical properties as the native fibers. For this study, three proteins based on the Argiope aurantia Major ampullate Spidroin 2 consensus repeat sequence were expressed, purified and spun into fibers. A number of post-spin draw conditions were tested to determine the effect of each condition on the mechanical properties of the fiber. In all cases, post-spin stretching improved the mechanical properties of the fibers. Aqueous isopropanol was the most effective solution for increasing extensibility, while other solutions worked best for each fiber type for increasing tensile strength. The strain values of the stretched fibers correlated with the length of the proline-rich protein sequence. Structural analysis, including X-ray diffraction and Raman spectroscopy, showed surprisingly little change in the initial as-spun fibers compared with the post-spin stretched fibers.

Embiopterans produce silken galleries and sheets using exceptionally fine silk fibers in which they live and breed. In this study, we use electron microscopy (EM), Fourier-transform infrared (FT-IR) spectroscopy, wide angle X-ray diffraction (WAXD) and solid-state nuclear magnetic resonance (ssNMR) techniques to elucidate the molecular level protein structure of webspinner (embiid) silks. Silks from two species Antipaluria urichi and Aposthonia ceylonica are studied in this work. Electron microscopy images show that the fibers are about 90–100 nm in diameter, making webspinner silks among the finest of all known animal silks. Structural studies reveal that the silk protein core is dominated by β-sheet structures, and that the protein core is coated with a hydrophobic alkane-rich surface coating. FTIR spectra of native embiid silk shows characteristic alkane CH2 stretchings near 2800–2900 cm−1, which decrease approximately 50% after washing the silk with 2 : 1 CHCl3 : MeOH. Furthermore, 13C ssNMR data shows a significant CH2 resonance that is strongly affected by the presence of water, supporting the idea that the silk fibers are coated with a hydrocarbon-rich layer. Such a layer is likely used to protect the colonies from rain. FTIR data also suggests that embiid silks are dominated by β-sheet secondary structures similar to spider and silkworm silk fibers. NMR data confirms the presence of β-sheet nanostructures dominated by serine-rich repetitive regions. A deconvolution of the serine Cβ NMR resonance reveals that approximately 70% of all seryl residues exist in a β-sheet structure. This is consistent with WAXD results that suggest webspinner silks are 70% crystalline, which is the highest crystalline fraction reported for any animal silks. The work presented here provides a molecular level structural picture of silk fibers produced by webspinners.

XISF is a MATLAB program developed to separate intermolecular structure factors from total X-ray scattering structure factors for molecular liquids and amorphous solids. The program is built on a trust-region-reflective optimization routine with the r.m.s. deviations of atoms physically constrained. XISF has been optimized for performance and can separate intermolecular structure factors of complex molecules.

Acoustic levitation was used to trap 1–3 mm diameter drops of Probucol and other pharmaceutical materials in containerless conditions. Samples were studied in situ using X-ray diffraction and ex situ using neutron diffraction, NMR and DSC techniques. The materials were brought into non-equilibrium states by supersaturating solutions or by supercooling melts. The glass transition and crystallization temperatures of glassy Probucol were 29 ± 1 and 71 ± 1 °C respectively. The glassy form was stable with a shelf life of at least 8 months. A neutron/X-ray difference function of the glass showed that while molecular sub-groups remain rigid, many of the hydrogen correlations observed in the crystal become smeared out in the disordered material. The glass is principally comprised of slightly distorted Form I Probucol molecules with disordered packing rather than large changes in the individual molecular structure. Avoiding surface contact-induced nucleation provided access to highly non-equilibrium phases and enabled synthesis of phase-pure glasses.

Solid-state nuclear magnetic resonance (NMR) has been extensively used to elucidate spider silk protein structure and dynamics. In many of these studies, site-specific isotope enrichment is critical for designing particular NMR methods for silk structure determination. The commonly used isotope analysis techniques, isotope-ratio mass spectroscopy and liquid/gas chromatography-mass spectroscopy, are typically not capable of providing the site-specific isotope information for many systems because an appropriate sample derivatization method is not available. In contrast, NMR does not require any sample derivatization or separation prior to analysis. In this article, conventional liquid-state 1H NMR was implemented to evaluate incorporation of 13C/15N-labeled amino acids in hydrolyzed spider dragline silk. To determine site-specific 13C and 15N isotope enrichments, an analysis method was developed to fit the 1H–13C and 1H–15N J-splitting (J CH and J NH) 1H NMR peak patterns of hydrolyzed silk fiber. This is demonstrated for Nephila clavipes spiders, where [U–13C3,15N]-Ala and [1-13C,15N]-Gly were dissolved in their water supplies. Overall, contents for Ala and Gly isotopomers are extracted for these silk samples. The current methodology can be applied to many fields where site-specific tracking of isotopes is of interest.

Spider silks possess nature's most exceptional mechanical properties, with unrivalled extensibility and high tensile strength. Unfortunately, our understanding of silks is limited because the complete elastic response has never been measured-leaving a stark lack of essential fundamental information. Using non-invasive, non-destructive Brillouin light scattering, we obtain the entire stiffness tensors (revealing negative Poisson's ratios), refractive indices, and longitudinal and transverse sound velocities for major and minor ampullate spider silks: Argiope aurantia, Latrodectus hesperus, Nephila clavipes, Peucetia viridans. These results completely quantify the linear elastic response for all possible deformation modes, information unobtainable with traditional stress-strain tests. For completeness, we apply the principles of Brillouin imaging to spatially map the elastic stiffnesses on a spider web without deforming or disrupting the web in a non-invasive, non-contact measurement, finding variation among discrete fibres, junctions and glue spots. Finally, we provide the stiffness changes that occur with supercontraction.

Two-dimensional (2D) cross-polarization magic angle spinning (CP-MAS) 2 H– 13 C heteronuclear correlation (HETCOR) experiments were utilized to indirectly detect site-specific deuterium MAS powder patterns. The 2 H– 13 C cross-polarization efficiency is orientation-dependent and non-uniform for all crystallites. This leads to difficulty in extracting the correct 2 H MAS quadrupole powder patterns. In order to obtain accurate deuterium line shapes, 13 C spin lock rf field, spin lock rf ramp and CP contact time were carefully calibrated with the assistance of theoretical simulations. The extracted quadrupole patterns for U-[ 2 H/ 13 C/ 15 N]-alanine indicate that the methyl deuterium undergoes classic, three-site jumping in the fast motion regime (10 −8 –10 −12 s) and the methine deuterium has a rigid deuterium powder pattern. For U-[ 2 H/ 13 C/ 15 N]-phenylalanine, indirectly detected deuterium line shapes illustrate that the aromatic ring undergoes 180° flips in the fast motion regime while 2 Hβ and 2 Hα are completely rigid. The experimental deuterium line shapes for U-[ 2 H/ 13 C/ 15 N]-proline reflect that 2 Hβ, 2 Hγ and 2 Hδ are subjected to fast, two-site reorientations at an angle of (15 ± 5)°, (30 ± 5)° and (25 ± 10)° respectively. In addition, an approach that combines a composite inversion pulse with 2 H– 13 C CP-MAS is applied to measure 2 H spin–lattice relaxation times in a site-specific, 13 C-detected fashion.

Solid-state NMR and molecular dynamics (MD) simulations are presented to help elucidate the molecular secondary structure of poly(Gly-Gly-X), which is one of the most common structural repetitive motifs found in orb-weaving dragline spider silk proteins. The combination of NMR and computational experiments provides insight into the molecular secondary structure of poly(Gly-Gly-X) segments and provides further support that these regions are disordered and primarily non-β-sheet. Furthermore, the combination of NMR and MD simulations illustrate the possibility for several secondary structural elements in the poly(Gly-Gly-X) regions of dragline silks, including β-turns, 310-helicies, and coil structures with a negligible population of α-helix observed.

Insects of the order Embioptera, known as embiopterans, embiids, or webspinners, weave silk fibers together into sheets to make shelters called galleries. In this study, we show that silk galleries produced by the embiopteran Antipaluria urichi exhibit a highly hydrophobic wetting state with high water adhesion macroscopically equivalent to the rose petal effect. Specifically, the silk sheets have advancing contact angles above 150°, but receding contact angle approaching 0°. The silk sheets consist of layered fiber bundles with single strands spaced by microscale gaps. Scanning and transmission electron microscopy (SEM, TEM) images of silk treated with organic solvent and gas chromatography mass spectrometry (GC-MS) of the organic extract support the presence of a lipid outer layer on the silk fibers. We use cryogenic SEM to demonstrate that water drops reside on only the first layer of the silk fibers. The area fraction of this sparse outer silk layers is 0.1 to 0.3, which according to the Cassie-Baxter equation yields an effective static contact angle of ∼130° even for a mildly hydrophobic lipid coating. Using high magnification optical imaging of the three phase contact line of a water droplet receding from the silk sheet, we show that the high adhesion of the drop stems from water pinning along bundles of multiple silk fibers. The bundles likely form when the drop contact line is pinned on individual fibers and pulls them together as it recedes. The dynamic reorganization of the silk sheets during the droplet movement leads to formation of "super-pinning sites" that give embiopteran silk one of the strongest adhesions to water of any natural hydrophobic surface.

The need for reliable means of ordering and quantifying the Lewis basicity of anions is discussed and the currently available methods are reviewed. Concluding that there is need for a simple impurity-insensitive tool, we have sought, and here describe, a new method using NMR spectroscopy of a weak base, a substituted urea, 1,3-dimethyl-2-imidazolidinone (DMI), as it is protonated by Brønsted acids of different strengths and characters. In all cases studied the product of protonation is a liquid (hence a protic ionic liquid). NMR spectroscopy detects changes in the electronic structure of the base upon interaction with the proton donors. As the proton-donating ability, that is, acidity, increases, there is a smooth but distinct transition from a hydrogen-bonded system (with no net proton transfer) to full ionicity. The liquid state of the samples and high concentration of nitrogen atoms, despite the very low natural abundance of its preferred NMR-active isotope ((15) N), make possible the acquisition of (15) N spectra in a relatively short time. These (15) N, along with (13) C, chemical shifts of the carbonyl atom, and their relative responses to protonation of the carbonyl oxygen, can be used as a means, sensitive to anion basicity and relatively insensitive to impurities, to sort anions in order of increasing hydrogen bond basicity. The order is found to be as follows: SbF6 (-)BF4 (-)NTf2 (-)ClO4 (-)FSO3 (-)TfO(-)HSO4 (-)Cl(-)MsO(-) .

The primary objective of this research is to elucidate the interactions, mechanisms and biochemistry of the spider silk producing process at the molecular level. Our primary focus is to characterize the protein-rich fluid in the various spider silk producing glands. We have been using a battery of magnetic resonance methods including solution and solid-state nuclear magnetic resonance (NMR) and micro imaging (MRI) in combination with wide angle and small angle X-ray diffraction (WAXD and SAXD) techniques at Argonne National Laboratory (ANL) to probe silk protein structure and dynamics prior to and following fiber formation. We have established a number of methods for isotopically (2H/13C/15N) enriching the silk proteins during the course of our AFOSR funding that have allowed us to investigate the structure, dynamics, and organization of spider silk protein within the silk gland and in the final spun fiber with a range of magnetic resonance methods. We successfully developed magnetic resonance imaging (MRI) techniques with localized spectroscopy to probe the silk glands of spiders and map protein structure through out the silk gland.

Hydrogen-bonding plays a key role in the structure and dynamics of a wide range of materials from small molecules to complex biomolecules. 1H NMR has emerged as a powerful tool for studying hydrogen-bonding because the proton isotropic chemical shift exhibits a dependence on the interatomic distances associated with the hydrogen bond. In the present work, we illustrate the use of ultrafast magic angle spinning at high magnetic field (800 MHz) for resolving multiple hydrogen-bonding sites in a set of crystalline phosphonic acids that contain various functional groups (−COOH, −PO3H2, and −NH3+). Trends are observed between the proton chemical shift of the hydrogen-bonded proton and the associated hydrogen-bonding distances (O–H···X) from X-ray crystallography. Density functional theory calculations conducted on the phosphonic acid structures illustrate that the experimental proton chemical shift dependence on hydrogen-bond distance agrees with the expected theoretical trends. Further, it is shown that the c...

Structural transitions in amorphous red phosphorus were studied at ambient temperature and pressures up to 12 GPa. Amorphous (red) phosphorus was observed to transform into crystalline black phosphorus at 7.5 ± 0.5 GPa using diamond anvil cell Raman spectroscopy, x-ray diffraction and a direct equation of state (EoS) measurement. The transition was found to be irreversible and the material recovered upon pressure cycling to 10 to 12 GPa was crystalline orthorhombic black phosphorus. A third order Birch–Murnaghan EoS was fit to the data and a bulk modulus (B0) of 11.2 GPa was measured for amorphous red phosphorus.

Spider silk is renowned for its extraordinary mechanical properties, having a balance of high tensile strength and extensibility. To date, the majority of studies have focused on the production of dragline silks from synthetic spider silk gene products. Here we report the first mechanical analysis of synthetic egg case silk fibers spun from the Latrodectus hesperus tubuliform silk proteins, TuSp1 and ECP-2. We provide evidence that recombinant ECP-2 proteins can be spun into fibers that display mechanical properties similar to other synthetic spider silks. We also demonstrate that silks spun from recombinant thioredoxin-TuSp1 fusion proteins that contain the conserved C-terminal domain exhibit increased extensibility and toughness when compared to the identical fibers spun from fusion proteins lacking the C-terminus. Mechanical analyses reveal that the properties of synthetic tubuliform silks can be modulated by altering the postspin draw ratios of the fibers. Fibers subject to increased draw ratios showed elevated tensile strength and decreased extensibility but maintained constant toughness. Wide-angle X-ray diffraction studies indicate that postdrawn fibers containing the C-terminal domain of TuSp1 have more amorphous content when compared to fibers lacking the C-terminus. Taken together, these studies demonstrate that recombinant tubuliform spidroins that contain the conserved C-terminal domain with embedded protein tags can be effectively spun into fibers, resulting in similar tensile strength but increased extensibility relative to nontagged recombinant dragline silk proteins spun from equivalently sized proteins.

Spider silks display some of the most impressive mechanical properties of known fibrous materials. However, a molecular level understanding of how spiders store and convert the highly concentrated protein-rich fluid in the gland to an insoluble super fiber at the spinneret remains unanswered. In this report, we demonstrate the utility of High-Resolution Magic Angle Spinning (HR-MAS) NMR spectroscopy to study the molecular structure of the proteins within excised major ampullate (MA) glands from two orb weaving spiders, Nephila clavipes and Argiope aurantia. The spiders were fed various 13C-enriched amino acids to target different regions of the proteins and enable multi-dimensional, multinuclear HR-MAS NMR experiments. Comparisons are made between these HR-MAS results on MA glands and previous solid-state NMR data on spider dragline silk. The conformation-dependent 13C and 1H isotropic chemical shifts obtained in this study indicate that both dragline silk proteins, major ampullate spidroin 1 (MaSp1) and 2 (MaSp2), are present in a random coil conformation in the MA gland prior to fiber formation for both spider species.

High-energy X-ray diffraction experiments have been performed on GeSe{sub 4} glass up to pressures of 8.6 GPa, and the equation of state has been measured up to 10 GPa. The X-ray structure factors reveal a decrease in the first sharp diffraction peak intensity and broadening with pressure, which signifies a break-up of the intermediate range order in the glass. In contrast, the principal peak in the structure factor shows an increase in intensity and a sharpening with pressure, which is attributed to an increase in extended range order and coherence of the compacted units. The average nearest neighbor coordination number is found to remain constant in GeSe{sub 4} glass (within experimental error) over the pressure range measured. This is in contrast with the gradual increase found in GeSe{sub 2} glass. Rather, in GeSe{sub 4} glass the densification mechanism is shown to be associated with large inward shifts of the second neighbor and higher coordination shells. These features appear as additional correlations at 3.3 and 5.3 {angstrom} in the differences taken between adjacent pair distribution functions with increasing pressure.

27Al NMR is used to quantify coordination changes in CaAl2O4 glass pressure cycled to 16 GPa. The structure and coordination environments remain unchanged up to 8 GPa, at which 93% of the recovered glass exists as four-fold Al, whereas the remaining population exists as [5,6]Al. Upon densification, [5,6]Al comprises nearly 30% of observed Al, most likely through the generation of three-coordinated oxygen. Negligible changes are observed for the isotropic chemical shift ([4]Al ≈ 78.8 ppm, [5]Al ≈ 46.3 ppm, [6]Al ≈ 12.6 ppm) and average quadrupole coupling strengths with pressure. 3QMAS spectra suggest less distortion within the newly formed Al environments in comparison with [4]Al. The chemical shift of [4]Al suggests that the aluminate network remains fully polymerized in glasses quenched from pressures up to 16 GPa.

The structure factors of Mg2SiO4 glass have been measured using high energy x-ray diffraction up to pressures of 30.2 GPa, and the equation of state measured up to 12.8 GPa. The average Mg–O coordination numbers were extracted from the experimental pair distribution functions assuming two cases (i) there is no change in Si–O coordination number with pressure and (ii) the average Si–O coordination number increases the same as for pure SiO2 glass. Both analyses give similar results and show a gradual increase in the average Mg–O coordination number from 5.0 at ambient pressure to ~ 6.6(6) at 30.2 GPa. There is good qualitative agreement between the experimental structure and equation of state data for the glass compared to several recent molecular dynamics simulations carried out on liquid Mg2SiO4.