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D- and L-arginine-based polyamidoamino acids, called D- and L-ARGO7, retain the chirality and acid/base properties of the parent -amino acids and show pH-dependent self-structuring in water. The ability of the ARGO7 chiral isomers to selectively interact with chiral biomolecules and/or surfaces was studied by choosing sodium deoxycholate (NaDC) as a model chiral biomolecule for its ability to self-assembly into globular micelles, showing enantio-selectivity. To this purpose, mixtures of NaDC with D-, L- or D,L-ARGO7, respectively, in water were analysed by circular dichroism (CD) spectroscopy and small-angle neutron scattering (SANS) at different levels of acidity expressed in terms of pD and concentrations. Differences in the CD spectra indicated chiral discrimination for NaDC/ARGO7 mixtures in the gel phase (pD 7.30) but not in the solution phase (pD 9.06). SANS measurements confirmed large scale structural perturbation induced by this chiral discrimination in the gel phase yet no modulation of the structure in the solution phase. Together, these techniques shed light on the mechanism by which ARGO7 stereoisomers modify the morphology of NaDC micelles as a function of pH. This work demonstrates chirality-dependent interactions that drive structural evolution and phase behaviour of NaDC, opening the way for designing novel smart drug delivery systems.

In this study, polymeric microneedle patches were fabricated by stereolithography, a 3D printing technique, for the transdermal delivery of insulin. A biocompatible resin was photopolymerized to build pyramid and cone microneedle designs followed by inkjet print coating of insulin formulations. Trehalose, mannitol and xylitol were used as drug carriers with the aim to preserve insulin integrity and stability but also to facilitate rapid release rates. Circular dichroism and Raman analysis demonstrated that all carriers maintained the native form of insulin, with xylitol presenting the best performance. Franz cell release studies were used for in vitro determination of insulin release rates in porcine skin. Insulin was released rapidly within 30 min irrespectively of the microneedle design. 3D printing was proved an effective technology for the fabrication of biocompatible and scalable microneedle patches.

Thermomechanical engineering of pharmaceutical salts in the solid state using continuous extrusion processing (ssTME) is a new novel manufacturing approach. In the present work, we introduce a paradigm for the synthesis of ketoconazole – oxalic acid and ciprofloxacin – maleic acid salts by imparting temperature, shear rate and stress in comparison to liquid assisted grinding (LAG) approach. We demonstrated that thermomechanical synthesis is advantageous by producing high quality and pure, solvent-free pharmaceutical salts by tailoring extrusion processing variables.

Heavy minerals are typically rare but important components of siliciclastic sediments and rocks. Their abundance, proportions, and variability carry valuable information on source rocks, climatic, environmental and transport conditions between source to sink, and diagenetic processes. They are important for practical purposes such as prospecting for mineral resources or the correlation and interpretation of geologic reservoirs. Despite the extensive use of heavy mineral analysis in sedimentary petrography and quite diverse methods for quantifying heavy mineral assemblages, there has never been a systematic comparison of results obtained by different methods and/or operators. This study provides the first interlaboratory test of heavy mineral analysis. Two synthetic heavy mineral samples were prepared with considerably contrasting compositions intended to resemble natural samples. The contributors were requested to provide (i) metadata describing methods, measurement conditions and experience of the operators and (ii) results tables with mineral species and grain counts. One hundred thirty analyses of the two samples were performed by 67 contributors, encompassing both classical microscopic analyses and data obtained by emerging automated techniques based on electron-beam chemical analysis or Raman spectroscopy. Because relatively low numbers of mineral counts (N) are typical for optical analyses while automated techniques allow for high N, the results vary considerably with respect to the Poisson uncertainty of the counting statistics. Therefore, standard methods used in evaluation of round robin tests are not feasible. In our case the 'true' compositions of the test samples are not known. Three methods have been applied to determine possible reference values: (i) the initially measured weight percentages, (ii) calculation of grain percentages using estimates of grain volumes and densities, and (iii) the best-match average calculated from the most reliable analyses following multiple, pragmatic and robust criteria. The range of these three values is taken as best approximation of the 'true' composition. The reported grain percentages were evaluated according to (i) their overall scatter relative to the most likely composition, (ii) the number of identified components that were part of the test samples, (iii) the total amount of mistakenly identified mineral grains that were actually not added to the samples, and (iv) the number of major components, which match the reference values with 95% confidence. Results indicate that the overall comparability of the analyses is reasonable. However, there are several issues with respect to methods and/or operators. Optical methods yield the poorest results with respect to the scatter of the data. This, however, is not considered inherent to the method as demonstrated by a significant number of optical analyses fulfilling the criteria for the best-match average. Training of the operators is thus considered paramount for optical analyses. Electron-beam methods yield satisfactory results, but problems in the identification of polymorphs and the discrimination of chain silicates are evident. Labs refining their electron-beam results by optical analysis practically tackle this issue. Raman methods yield the best results as indicated by the highest number of major components correctly quantified with 95% confidence and the fact that all laboratories and operators fulfil the criteria for the best-match average. However, a number of problems must be solved before the full potential of the automated high-throughput techniques in heavy mineral analysis can be achieved. info:eu-repo/semantics/publishedVersion

Hypothesis:\ud The presence of surfactant modulates the surface-chemistry-specific interaction of hard colloidal particles (latex) with HEUR polymers, principally through introducing a preferential solution interaction rather than a competitive surface interaction; addition of surfactant leads to a preponderance of polymer/surfactant solution complexes rather than surface-bound complexes.\ud \ud Experiments:\ud A range of model formulations comprising a hexyl end-capped urethane polymer (C6-L-(EO100-L)9-C6), sodium dodecylsulfate (SDS) and a series of polystyrene-butylacrylate latices (PS-BA-L) have been characterised in terms of rheology, particle surface area (solvent relaxation NMR), polymer conformation (small-angle neutron scattering) and solution composition to build up a detailed picture of the distribution of the HEUR in the presence of both surfactant and latex.\ud \ud Findings:\ud There is very weak adsorption of C6-L-(EO100-L)9-C6 to only the most hydrophobic latex surface studied, an adsorption that is further weakened by the addition of low levels of surfactant. Macroscopic changes in the hydrophobic latex system may be interpreted in terms of bridging flocculation at low polymer concentrations. No adsorption of C6-L-(EO100-L)9-C6 is observed in the case of hydrophilic surfaces. In most cases, the observed behaviour of the ternary system (polymer/surfactant/particle) is highly reminiscent of the binary (polymer/surfactant) system at the appropriate composition, suggesting that the polymer/surfactant solution interaction is the dominant one.

Hypothesis \ud Adsorption of hydrophobically modified ethoxylated urethane polymers (HEURs) at the soft colloid interfaces of emulsion droplets will stabilise oil-in-water emulsions (a) via steric stabilisation induced by adsorption of the polymer at the droplet surfaces through the hydrophobic groups, and (b) via continuous phase viscosity enhancement through polymer self-association. Both of these mechanisms will be modulated by the presence of the surfactant, sodium dodecylsulfate (SDS).\ud \ud Experiments\ud Dodecane-in-water emulsions stabilised by three HEUR polymers with different structural composition were examined in the absence and presence of SDS by NMR spectroscopy and small-angle neutron scattering (SANS). The effect of adsorption of the polymer to the dodecane droplet surfaces, and the conformation of the self-associating polymer in the aqueous solution were quantified.\ud \ud Findings\ud All emulsions were stable for days-weeks. Diffusion data showed the formation of oil droplets of hundreds of nm in size in the presence of all three HEURs, here denoted C6-L-(EO100-L)9-C6, C10-L-(EO200-L)4-C10, and C18-L-(EO200-L)7-C18, where EOx represents a block of ethylene oxide of x monomers, L denotes the linker group, and Cn the length of the hydrophobic end-group. No significant changes in droplet size across this series of polymers was observed. Collectively, the results point to adsorption of the polymer to the droplet surfaces, which results in a small decrease in the effective polymer solution concentration, thereby driving to significant changes in the structure and dynamics of the system. Evident in the SANS data in particular, is a subtle balance between the characteristic features reflecting polymer self-association, and those associated with polymer structures commensurate with a larger length-scale, dependent on the system composition. Surprisingly, the polymer and polymer/SDS complex in the presence of oil show slightly greater diffusive rates relative to the analogous systems in the absence of the oil. Finally, the partitioning of the three polymers in phase-separated samples was studied by 1H NMR, and it was shown that the C18-L-(EO200-L)7-C18 exhibited a greater partitioning in the oil phase compared with C6-L-(EO100-L)9-C6 and C10-L-(EO200-L)4-C10, an observation that may be understood in terms of the structural composition of the HEURs. The SDS showed a positive correlation between its partitioning in the two layers with the polymer partitioning, evidence of a strong interaction between the surfactant and the polymer, consistent with the behaviour observed in the oil-free system.

Despite the importance of membrane proteins in cellular processes, studies of these hydrophobic proteins present major technical challenges, including expression and purification for structural and biophysical studies. A modified strategy of that proposed previously by Saidijam et al. (2005) and others, for the routine expression of bacterial membrane proteins involved in environmental sensing and antimicrobial resistance (AMR), is proposed which results in purification of sufficient proteins for biophysical experiments. We report expression successes amongst a collection of enterococcal vancomycin resistance membrane proteins: VanTG, VanTG-M transporter domain, VanZ and the previously characterised VanS (A-type) histidine protein kinase (HPK). Using the same strategy, we report on the successful amplification and purification of intact BlpH and ComD2 HPKs of Streptococcus pneumoniae. Near-UV circular dichroism revealed both recombinant proteins bound their pheromone ligands BlpC and CSP2. Interestingly, CSP1 also interacted with ComD. Finally, we evaluate the alternative strategy for studying sensory HPKs involving isolated soluble sensory domain fragments, exemplified by successful production of VicKESD of Enterococcus faecalis VicK. Purified VicKESD possessed secondary structure post-purification. Thermal denaturation experiments using far-UV CD, a technique which can be revealing regarding ligand binding, revealed that: (a) VicKESD denaturation occurs between 15 and 50 °C; and (b) reducing conditions did not detectably affect denaturation profiles suggesting reducing conditions per se are not directly sensed by VicKESD. Our findings provide information on a modified strategy for the successful expression, production and/or storage of bacterial membrane HPKs, AMR proteins and sensory domains for their future crystallisation, and ligand binding studies.

Hypothesis:\ud Hydrophobically modified ethoxylated urethane polymers (HEURs) are widely used to control the rheological profile of formulated particulate dispersions through associative network formation, the properties of which are perturbed by the presence of surfactants. At high polymer concentrations and in the presence of surfactants, it is hypothesised that the dominant factors in determining the rheological profile are the number and composition of the mixed hydrophobic aggregates, these being defined by the number and distribution of the hydrophobic linkers along the polymer backbone, rather than the end-group hydrophobe characteristics per se that dominate the low polymer concentration behaviour. \ud \ud Experiments:\ud Three different HEUR polymers with formulae (C6-L-(EO100-L)9-C6, C10-L-(EO200-L)4-C10 and C18-L-(EO200-L)7-C18 (where L = urethane linker, Cn = hydrophobic end-group chain length, and EO = ethylene oxide block) have been studied in the absence and presence of SDS employing techniques that quantify (a) the bulk characteristics of the polymersurfactant blend, (b) the structure and composition of the hydrophobic domains, (c) the dynamics of the polymer and surfactant, and (d) the polymer conformation. Collectively, these experiments demonstrate how molecular-level interactions between the HEURs and sodium dodecylsulphate (SDS) define the macroscopic behaviour of the polymer/surfactant mixture.\ud \ud Findings:\ud Binding of the SDS to the polymer via two mechanisms - monomeric anti-cooperative and micellar cooperative - leads to surfactant-concentration-specific macroscopic changes in the viscosity. Binding of the surfactant to the polymer drives a conformational rearrangement, and an associated redistribution of the polymer end-groups and linker associations throughout the hydrophobic domains. The composition and size of these domains are sensitive to the polymer architecture. Therefore, there is a complex balance between polymer molecular weight, ethylene oxide block size, and number of urethane linkers, coupled with the size of the hydrophobic end-groups. In particular, the urethane linkers are shown to play a hitherto largely neglected but important role in driving the polymer association.

Circular dichroism (CD) spectroscopy has been used extensively for the investigation of the conformation and configuration of chiral molecules, but its use for evaluating the mode of self-assembly in soft materials has been limited. Herein, we report a protocol for the study of such materials by electronic circular dichroism (CD) spectroscopy using commercial/benchtop instruments and synchrotron radiation (SR) using the B23 beamline available at Diamond Light Source. The use of B23 beamtime for SRCD was advantageous due to the unique enhanced spatial resolution achieved because of its highly collimated and small beamlight cross-section (ca 250 μm) and higher photon flux in the far UV region (175-250 nm) enhancing the signal-to-noise ratio relative to benchtop CD instruments. A set of low molecular weight (LMW) hydrogelators, comprising two Fmoc-protected enantiomeric monosaccharides and one Fmoc-dipeptide (Fmoc-FF) were studied. The research focused on the optimization of sample preparation and handling, which then enabled the characterisation of sample conformational homogeneity and thermal stability. CD spectroscopy, in combination with other spectroscopic techniques and microscopy, will allow a better insight into the self-assembly of chiral building blocks into higher order structural architectures.

This work aims to study the behavior of temperature-responsive p(NIPAM) and temperature/pH-responsive p(NIPAM)/acrylic acid (AA) microgels. Three microgels were synthesized using surfactant free emulsion polymerization technique, these are p(NIPAM), p(NIPAM)-co-AA 95:5% (w/w) and p(NIPAM)-co-AA 90:10% (w/w). Dynamic light scattering was used to study the behavior of diluted microgel dispersions (0.5%, w/w p(NIPAM)), while rheology was used to study the viscosity of 2% (w/w) p(NIPAM) dispersions. The characterization data indicate the swelling/deswelling and flocculation/deflocculation behavior of the microgels. The conditions required for flocculation were used to test the ability of the microgel dispersions to block a membrane of pore size 5 μm. In 3 h, p(NIPAM), p(NIPAM) 5% AA (w/w) and p(NIPAM)10% AA (w/w) blocked the membrane (decrease the flow rate) by 96.16, 59.44 and 59.8% respectively. Thus, the controlled flocculation of microgels may be used in applications where pore blocking is important such as the treatment of dentinal hypersensitivity, given that the VPTT of p(NIPAM) is ≈34 °C, which is very close to the human body temperature.

UV--visible (UV-vis) absorption spectroscopy is widely used as a primary means of assaying concentrations and in characterizing the kinetics of reactions and chemical processes; it is ubiquitously used for chromatographic detection. Although currently somewhat less widely used as a first means of structural analysis, compared to spectroscopies such as nuclear magnetic resonance, it remains pre-eminent for a wide range of specialist areas, especially those involving distinctive chromophoric compounds such as dyes, indicators, and filters. Its ability to probe the electronic states of molecules also ensures its wide use for detailed physical studies. The focus of this article is on the qualitative and quantitative application of UV-vis spectroscopy to organic compounds and practical guidance for the preparation of samples, interpretation of spectra, and understanding of the variables that can occur or be utilized. Typical spectral data for representative classes of compound are indicated and discussed.

A comprehensive understanding of the mechanisms of interaction between proteins or peptides and nanomaterials is crucial for the development of nanomaterial-based diagnostics and therapeutics. In this work, we systematically explored the interactions between citrate-capped gold nanoparticles (AuNPs) and islet amyloid polypeptide (IAPP), a 37-amino acid peptide hormone co-secreted with insulin from the pancreatic islet. We utilized diffusion-ordered spectroscopy, isothermal titration calorimetry, localized surface plasmon resonance spectroscopy, gel electrophoresis, atomic force microscopy, transmission electron microscopy (TEM), and molecular dynamics (MD) simulations to systematically elucidate the underlying mechanism of the IAPP–AuNP interactions. Because of the presence of a metal-binding sequence motif in the hydrophilic peptide domain, IAPP strongly interacts with the Au surface in both the monomeric and fibrillar states. Circular dichroism showed that AuNPs triggered the IAPP conformational transition from random coil to ordered structures (α-helix and β-sheet), and TEM imaging suggested the acceleration of IAPP fibrillation in the presence of AuNPs. MD simulations revealed that the IAPP–AuNP interactions were initiated by the N-terminal domain (IAPP residues 1–19), which subsequently induced a facet-dependent conformational change in IAPP. On a Au(111) surface, IAPP was unfolded and adsorbed directly onto the Au surface, while for the Au(100) surface, it interacted predominantly with the citrate adlayer and retained some helical conformation. The observed affinity of AuNPs for IAPP was further applied to reduce the level of peptide-induced lipid membrane disruption.

International audience; The ability to accurately constrain the secular record of high- and ultra-high pressure metamorphism on Earth is potentially hampered as these rocks are metastable and prone to retrogression, particularly during exhumation. Rutile is among the most widespread and best preserved minerals in high- and ultra-high pressure rocks and a hitherto untested approach is to use mineral inclusions within rutile to record such conditions. In this study, rutiles from three different high- and ultrahigh-pressure massifs have been investigated for inclusions. Rutile is shown to contain inclusions of high-pressure minerals such as omphacite, garnet and high silica phengite, as well as diagnostic ultrahigh-pressure minerals, including the first reported occurrence of exceptionally preserved monomineralic coesite in rutile from the Dora–Maira massif. Chemical comparison of inclusion and matrix phases show that inclusions generally represent peak metamorphic assemblages; although rare prograde phases such as titanite, omphacite and corundum have also been identified implying that rutile grows continuously during prograde burial and traps mineralogic evidence of this evolution. Pressure estimates obtained from mineral inclusions, when used in conjunction with Zr-in-rutile thermometry, can provide additional constraints on the metamorphic conditions of the host rock. This study demonstrates that rutile is an excellent repository for high- and ultra-high pressure minerals and that the study of mineral inclusions in rutile may profoundly change the way we investigate and recover evidence of such events in both detrital populations and partially retrogressed samples.

The catechin, epigallocatechin gallate (eGCG), found in green tea, has inhibitory activity against a number of protein toxins and was investigated in relation to its impact upon ricin toxin (RT) in vitro. The IC50 for RT was 0.08 ± 0.004 ng/mL whereas the IC50 for RT + 100 μM eGCG was 3.02 ± 0.572 ng/mL, indicating that eGCG mediated a significant (p

The aim of this study was to enhance the apparent solubility and dissolution properties of flurbiprofen through inclusion complexation with cyclodextrins. Especially, the efficacy of supercritical fluid technology as a preparative technique for the preparation of flurbiprofen-methyl–β–cyclodextrin inclusion complexes was evaluated. The complexes were prepared by supercritical carbon dioxide processing and were evaluated by solubility, differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, practical yield, drug content estimation and in vitro dissolution studies. Computational molecular docking studies were conducted to study the possibility of molecular arrangement of inclusion complexes between flurbiprofen and methyl-β-cyclodextrin. The studies support the formation of stable molecular inclusion complexes between the drug and cyclodextrin in a 1:1 stoichiometry. In vitro dissolution studies showed that the dissolution properties of flurbiprofen were significantly enhanced by the binary mixtures prepared by supercritical carbon dioxide processing. The amount of flurbiprofen dissolved into solution alone was very low with 1.11 ± 0.09% dissolving at the end of 60 min, while the binary mixtures processed by supercritical carbon dioxide at 45 °C and 200 bar released 99.39 ± 2.34% of the drug at the end of 30 min. All the binary mixtures processed by supercritical carbon dioxide at 45 °C exhibited a drug release of more than 80% within the first 10 min irrespective of the pressure employed. The study demonstrated the single step, organic solvent-free supercritical carbon dioxide process as a promising approach for the preparation of inclusion complexes between flurbiprofen and methyl–β–cyclodextrin in solid-state.

This study investigated the development of a novel approach to surface characterisation of drug polymorphism and the extension of the capabilities of this method to perform ‘real time’ in situ measurements. This was achieved using diffuse reflectance visible spectroscopy (DRV spectroscopy) and dye deposition, using the pH sensitive dye, thymol blue (TB). Two polymorphs, SFN-β and SFN-γ, of the drug substance sulfanilamide (SFN) were examined. The interaction of adsorbed dye with polymorphs showed different behavior, and thus reported different DRV spectra. Consideration of the acid/base properties of the morphological forms of the drug molecule provided a rationalization of the mechanism of differential coloration by indicator dyes. The kinetics of the polymorphic transformation of sulfanilamide polymorphs was monitored using treatment with TB dye and DRV spectroscopy. The thermally-induced transformation fitted a first-order solid-state kinetic model (R2 = 0.992), giving a rate constant of 2.43 x 10−2 s−1.

There are currently no techniques that allow facile on-line determination between amorphous and crystalline material. Herein, a new colorimetric method, perichromism, has been developed to distinguish between amorphous and crystalline material, based on diffuse reflection ultraviolet–visible (UV-visible) spectroscopy. A probe molecule, phenol red, at 0.1% w/w concentration was added to sucrose and dissolved in water. The solution was freeze-dried, which resulted in an amorphous excipient with the probe molecule incorporated in an intimate mixture. The samples were then stored at a selected controlled temperature and relative humidity to allow control of crystallization of the sucrose. The amorphous or crystalline nature of each sample, both with and without the addition of the phenol red probe molecule, was monitored through X-ray diffraction, differential scanning calorimetry, and Raman spectroscopy. It was found that sucrose remained amorphous when stored in an atmosphere with a relative humidity below 32%; above this level, crystallization occurred. It was found that the presence of the probe molecule did not alter the extent of crystallinity of sucrose. Analysis of the samples containing the phenol red probe by diffuse reflection spectroscopy revealed that spectra could be classified into two groups depending on the λmax. Furthermore, correlation of the diffuse reflection spectra with X-ray diffraction and differential scanning calorimetry data showed that sucrose was amorphous in one group and crystalline in the other group, thereby revealing that diffuse reflection spectroscopy can, when phenol red is used as a probe molecule, quickly and easily determine whether sucrose is crystalline or amorphous.

Transient absorption spectroscopy (TAS) has been employed to identify the spectra of photogenerated electrons and holes on WO3. WO3 is a widely studied photoanode for the oxidation of water, and by measuring the decay of photoholes on the milliseconds to seconds time scale in the presence of an electron scavenger, we provide a lower limit for the required lifetime of holes for water oxidation on WO3. The rate of electron/hole recombination on WO3 has also been examined at a range of excitation intensities and is found to be nonlinear with excitation intensity.

FeVO 4 was synthesised using a low temperature, aqueous precipitation reaction. The material prepared directly from this synthesis was found to be predominantly amorphous and required a thermal treatment. The resultant material was characterised using XRD, FT-IR, Raman spectroscopy and magnetic susceptibility measurements. Materials annealed above 600 °C were found to consist mainly of FeVO 4 , although traces of hematite were found following annealing at higher temperatures. Diffuse-reflectance UV spectroscopy and subsequent Tauc plots revealed a band gap of ca . 2.00 eV corresponding to an indirect transition. Photocurrent–voltage characteristics recorded under simulated solar illumination indicate that photocurrents are sensitive to annealing temperature and the number of layers deposited on an electrode surface.

N-acetyl-l-glutamic acid, crystallizes in the orthorhombic space group P212121 with unit cell parameters a = 4.747(3), b = 12.852(7), c = 13.906(7) A, V = 848.5(8) A3, Z = 4, density (calculated) = 1.481 mg/m3, linear absorption coefficient 0.127 mm−1. The crystal structure determination was carried out with MoKα X-ray data measured with liquid nitrogen cooling at 100(2) K temperature. In the final refinement cycle the data/restraints/parameter ratios were 1,691/0/131; goodness-of-fit on F2 = 1.122. Final R indices for [I > 2sigma(I)] were R1 = 0.0430, wR2 = 0.0878 and R indices (all data) R1 = 0.0473, wR2 = 0.0894. The largest electron density difference peak and hole were 0.207 and −0.154 eA−3. Details of the molecular geometry are discussed and compared with a model DFT structure calculated using Gaussian 98. The low temperature X-ray structure of N-acetyl-l-glutamic acid, including absolute configuration, is described. Comparison with the DFT structure is also discussed. Molecular conformation of N-acetyl-l-glutamic acid: (a) drawn with MERCURY [22] and (b) surfaces drawn with VMD [26].

With the aim of improving the performance and extending the range of applications of mesoporous WO3 films, which were initially developed for the photoelectrochemical oxidation of water, we investigated the effect of a number of dopants (lithium, silicon, ruthenium, molybdenum and tin) upon the transparency, crystallinity, porosity and conductivity of the modified films. Tin, molybdenum and silicon were shown to improve the electrochromic behaviour of the layers whereas ruthenium enhanced considerably the electronic conductivity of the WO3 films. Interestingly, most of the dopants also affected the film morphology and the size of WO3 nanocrystals. X-ray photoelectron spectra revealed absence of significant segregation of doping elements within the film. Raman analyses confirmed that the monoclinic structure of WO3 films does not change upon substitutional cation doping; thus, the crystallinity of WO3 films is maintained.

Experimental vibrational spectroscopic studies and density functional theory (DFT) calculations of the amino acid derivatives N-acetyl-L-Asp and N-acetyl-L-Glu have been undertaken. Raman and IR spectra have been measured in the solid state for both molecules. DFT simulations were conducted using the B3-LYP correlation functional and the cc-pVDZ basis set in order to determine their energy minimized/geometry optimized structures (based on a single isolated molecule in the gaseous state), and vibrational spectra were computed at the optimized geometry in each case. Normal coordinate calculations have provided vibrational assignments for fundamental modes, including their potential energy distributions. Significant differences are observed in the computed structures and in the vibrational spectra of N-acetyl-L-Asp and N-acetyl-L-Glu. The combination of experimental and calculated results provides an insight into the structural and vibrational spectroscopic properties of N-acetylated amino acid derivatives.

Experimental vibrational spectroscopic studies and density functional theory (DFT) calculations of the di-amino acid peptide derivatives alpha- and beta-N-acetyl-L-Asp-L-Glu have been undertaken. Raman and infrared spectra have been recorded for samples in the solid state. DFT simulations were conducted using the B3-LYP correlation functional and the cc-pVDZ basis set to determine energy minimized/geometry optimized structures (based on a single isolated molecule in the gaseous state). Normal coordinate calculations have provided vibrational assignments for fundamental modes, including their potential energy distributions. Significant differences are observed between alpha- and beta-N-acetyl-L-Asp-L-Glu both in the computed structures and in the vibrational spectra. The combination of experimental and calculated spectra provide an insight into the structural and vibrational spectroscopic properties of di-amino acid peptide derivatives.

Structures of the [M(bpy)3]2+ complexes (M = Fe and Ru) have been calculated at the B3-LYP/DZVP level. IR and Raman spectra were calculated using the optimised geometries, employing a scaled quantum chemical force field, and compared with an earlier normal coordinate analysis of [Ru(bpy)3]2+ which was based upon experimental data alone, and the use of a simplified model. The results of the calculations provide a highly satisfactory fit to the experimental data and the normal coordinate analyses, in terms of potential energy distributions, allow a detailed understanding of the vibrational spectra of both complexes. Evidence is presented for Jahn-Teller distortion in the 1E MLCT excited state.

The absorption spectra. cyclic voltammetry and spectroelectrochemistry of [Ni(II)DPTAA] and [Co(II)DPTAA] (DPTAA = 6,13-diphenyldibenzo[b,i][1,4,8,11] tetraaza[14]annulene) complexes in DMF are reported in detail. The ligand oxidation is observed for [Ni(II)DPTAA] at +0.70 V vs. SCE whereas Ni2(+/+) occurs at - 1.60 V. For [Co(II)DPTAA], a ligand oxidation redox couple is seen at +0.56 V while the Co2+/+ and Co2+/3+ redox couples appear at -1.21 and +0.24 V, respectively. All observed redox couples are assigned to reversible one-electron processes on account of peak separations and scan-rate dependency. These processes were further investigated by spectroelectrochemistry for [Co(II)DPTAA]. For [Co(II)DPTAA], axial ligation of pyridine was found to shift the Co2+/3+ redox couple more negative. while the ligand oxidation was shifted to more positive potentials. From a spectrophotometric titration of [Co(II)DPTAA] with pyridine an equilibrium constant, K-f, was determined for the binding of pyridine to [Co(II)DPTAA]. This was found to be 10.2 dm(3) mol(-1), slightly lower than that of [Co(II)TAA], indicating the influence of the phenyl groups. From this value and shifts in the Co2+/3+ redox couple upon ligation, an equilibrium constant for the binding of pyridine to [Co(III)DPTAA], K'(f), was found to be 5.06 x 10(6) dm(3) mol(-1). (c) 2007 Elsevier B.V. All rights reserved.

The purpose of this study was to evaluate a single-step, organic solvent-free supercritical fluid process for the preparation of olanzapine-methyl-β-cyclodextrin complexes with an express goal to enhance the dissolution properties of olanzapine. The complexes were prepared by supercritical carbon dioxide processing, co-evaporation, freeze drying and physical mixing. The prepared complexes were then analysed by differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, solubility and dissolution studies. Computational molecular docking studies were performed to study the formation of molecular inclusion complexation of olanzapine with methyl-β-cyclodextrin. All the binary mixtures of olanzapine with methyl-β-cyclodextrin, except physical mixture, exhibited a faster and greater extent of drug dissolution than the drug alone. Products obtained by the supercritical carbon dioxide processing method exhibited the highest apparent drug dissolution. The characterisation by different analytical techniques suggests complete complexation or amorphisation of olanzapine and methyl-β-cyclodextrin complexes prepared by supercritical carbon dioxide processing method. Therefore, organic solvent-free supercritical carbon dioxide processing method proved to be novel and efficient for the preparation of solid inclusion complexes of olanzapine with methyl-β-cyclodextrin. The preliminary data also suggests that the complexes of olanzapine with methyl-β-cyclodextrin will lead to better therapeutic efficacy due to better solubility and dissolution properties.

The preparation of mesoporous tungsten trioxide from tungstic acid and tungstic hexaethoxide precursors containing an added organic stabiliser via a sol–gel method is reported. The effect of annealing temperature and precursor species on the photoelectrochemical performance and the electrochromic colouration efficiencies has been discussed with the help of the characterisation of crystalline structure (through Raman microscopy) and surface morphology (through SEM imaging). To cite this article: R. Solarska et al., C. R. Chimie 9 (2006).

The fabrication of thin-film Fe(2)O(3) photoanodes from the spray pyrolysis of Fe(III)-containing solutions is reported along with their structural characterization and application to the photoelectrolysis of water. These films combine good performance, measured in terms of photocurrent density, with excellent mechanical stability. A full investigation into the effects that modifications of the spray-pyrolysis method, such as the addition of dopants or structure-directing agents and changes in precursor species or carrier solvent, have on the performance of the photoanodes has been realized. The largest photocurrents were obtained from photoanodes prepared from ferric chloride precursor solutions, simultaneously doped with Ti(4+) (5%) and Al(3+) (1%). Doping with Zn(2+) also shows promise, cathodically shifting the onset potential by approximately 0.22 V.

Surface-enhanced resonance Raman scattering (SERRS) from the alpha-diimine complexes [Ru(bpm)(3)](2+) and [Ru(bpz)(3)](2+) is reported for the first time at a roughened silver electrode. In both cases, a possible adsorbate orientation has been proposed involving binding through nitrogen lone pair electrons to the silver surface, based on changes in band positions upon adsorption. The SERRS spectra of [Ru(bpm)(3)](2+) were found to change slightly with a change in applied potential. The relative intensity of the nu(C6C6') band was found to be dependent on both excitation wavelength and applied potential. This was ascribed to an active charge transfer (CT) mechanism operating synergistically with the electromagnetic mechanism. No such CT activity was observed in [Ru(bpz)(3)](2+). It is tentatively suggested that this behavior may arise from the different modes of adsorption of the two complexes.

For the first time, a full scaled quantum chemical normal coordinate analysis has been performed on [Ru(LL')(3)](2+) complexes, where LL' = 2,2'-bipyrazine (bpz) or 2,2'-bipyrimidine (bpm). Geometric structures were fully optimized using density functional theory and an effective core potential basis set. The infrared and Raman spectra were calculated using the optimized geometries. The results of the calculations provide a highly satisfactory fit to the experimental infrared and Raman spectra, and the potential energy distributions allow a detailed understanding of the vibrational bands therein.

To facilitate an objective comparison of the efficacy of the simulation of structural parameters and vibrational spectra of transition-metal complexes of commonly used ab initio methods, the geomet...

Thin film Fe 2 O 3 photoanodes deposited onto conducting glass substrates were employed for the light-induced splitting of water. The effects of the employed precursor (inorganic or co-ordination compounds), dopants (Ti(IV) and Al(III)) and preparation conditions upon photoelectrochemical characteristics of the films are discussed. A photoelectrolysis cell including an arrangement of three thin film Fe 2 O 3 photoanodes placed one behind another is shown to improve considerably the light harvesting efficiency.

The main objective of this study was to investigate different manufacturing processes claimed to promote inclusion complexation between indomethacin and cyclodextrins in order to enhance the apparent solubility and dissolution properties of indomethacin. Especially, the effectiveness of supercritical carbon dioxide processing for preparing solid drug–cyclodextrin inclusion complexes was investigated and compared to other preparation methods. The complexes were prepared by physical mixing, co-evaporation, freeze drying from aqueous solution, spray drying and supercritical carbon dioxide processing methods. The prepared complexes were then evaluated by scanning electron microscopy, differential scanning calorimetry, X-ray powder diffraction, solubility and dissolution studies. The method of preparation of the inclusion complexes was shown to influence the physicochemical properties of the formed complexes. Indomethacin exists in a highly crystalline solid form. Physical mixing of indomethacin and methyl-β-cyclodextrin appeared not to reduce the degree of crystallinity of the drug. The co-evaporated and freeze dried complexes had a lower degree of crystallinity than the physical mix; however the lowest degree of crystallinity was achieved in complexes prepared by spray drying and supercritical carbon dioxide processing methods. All systems based on methyl-β-cyclodextrin exhibited better dissolution properties than the drug alone. The greatest improvement in drug dissolution properties was obtained from complexes prepared using supercritical carbon dioxide processing, thereafter by spray drying, freeze drying, co-evaporation and finally by physical mixing.\ud \ud Supercritical carbon dioxide processing is well known as an energy efficient alternative to other pharmaceutical processes and may have application for the preparation of solid-state drug–cyclodextrin inclusion complexes. It is an effective and economic method that allows the formation of solid complexes with a high yield, without the use of organic solvents and problems associated with their residues.

Recently, responsive surfaces have attracted attention due to their potential applications. Reported research have studied the deposition of environmentally responsive particles on different surfaces, qualitatively tested their response to environmental conditions and studied their possible applications. In this work, novel fluorescent temperature-sensitive nanoparticles were synthesized using a surfactant free emulsion polymerization technique: poly(N-isopropylacrylamide-co-5% vinyl cinnamate) (p(NIPAM)5%VC). The new particles were characterized using dynamic light scattering and fluorescence spectroscopy. A novel sensitive method for the quantitative analysis of p(NIPAM) 5% VC using fluorescence spectroscopy was developed to determine the concentration of nanoparticle dispersions. This was further used to quantitatively determine the mass of nanoparticles deposited per unit area of glass pre-treated with acid, glass pre-treated with base, quartz, stainless steel, gold and teflon at 25 °C and 60 °C. Factors affecting the adsorption/desorption of the nanoparticles were studied, including the effect of substrate surface charge, surface roughness (using atomic force microscopy, AFM), hydrophilicity/hydrophobicity and the temperature at which the adsorption/desorption experiments were carried out. The results show that the effect of surface charge is the most significant, followed by that of surface roughness and temperature. Meanwhile, the influence of the hydrophobicity/hydrophilicity of the surface on the adsorption/desorption of nanoparticles appears to be far less significant than the previously mentioned factors.

An increasing human population requires a secure food supply and a cost effective, oral vaccine delivery system for livestock would help facilitate this end. Recombinant antigen adsorbed onto silica beads and coated with myristic acid, was released (∼15% (w/v)) over 24h at pH 8.8. At pH 2, the myristic acid acted as an enteric coating, protecting the antigen from a variety of proteases. The antigen adsorbed onto silica particles, coated in myristic acid had a conserved secondary structure (measured by circular dichroism (CD) spectroscopy) following its pH-triggered release. Small angle neutron scattering (SANS) was used to measure the thickness of the adsorbed antigen, finding that its adsorbed conformation was slightly greater than its solution radius of gyration, i.e. 120–160Å. The addition of myristic acid led to a further increase in particle size, with scattering data consistent with an acid thickness slightly greater than a monolayer of fully extended alkyl chains and a degree of hydration of around 50%. Whilst adsorbed onto the silica and coated in myristic acid, the protein was stable over 14 days at 42°C, indicating a reduced need for cold chain storage. These data indicate that further investigation is warranted into the development of this technology.

Peptoids (N-substituted glycines, i.e. a-peptoids) are artificial oligoamides which are closely related structurally to a-peptides with the side chains located on the amide nitrogen rather than the a-carbon (Fig. 1). A major advantage of a-peptoids is their ease of synthesis, particularly by the so-called ‘submonomer method’. A further benefit is the vast potential for diversity as the side chains on the amide nitrogens are introduced by primary amines. Therefore a-peptoids are particularly well suited for the construction of peptidomimetic libraries in the context of drug discovery as they have been shown to be resistant to proteolytic enzymes. Peptoids occupy a unique position as peptidomimetic foldamers since their backbones are deprived of free NH amides and thus have decreased capacity to form intramolecular H-bonding interactions. Although unnatural, a peptoid residue is structurally related to a proline as the coupling of residues gives tertiary amide bonds which can populate cis and trans conformations. These features confer greater flexibility to oligopeptoids but interestingly they maintain the propensity to form ordered secondary structures. a-Peptoids containing aromatic or aliphatic a-chiral side chains can fold into stable helical structures. For example, homo-peptoids with (S)-1-cyclohexylethyl or (S)-1-naphthylethyl side chains (s1npe) were reported to adopt, both in the solid

Solar hydrogen production through photocatalytically assisted water splitting has attracted a great deal of attention since its first discovery almost 30 years ago. The publication of investigations into the use of TiO 2 photoanodes has continued apace since and a critical review of current trends is reported herein. Recent advances in the understanding of the behaviour of nanoparticulate TiO 2 films is summarized along with a balanced report into the utility and nature of titania films doped with non-metallic elements and ordered, nanostructured films such as those consisting of nanotubes. Both of these are areas that have generated a not insignificant degree of activity. One goal of doping TiO 2 has been to extend the photoresponse of the material to visible light. A similar goal has seen a resurgence in interest in Fe 2 O 3 photoanodes. Herein, the influence of dopants on the photocurrent density observed at Fe 2 O 3 photoanodes and, in this regard, the role of silicon has attracted much attention, and a little debate. Finally, we look beyond the binary oxides. Photoanodes made from new materials such as mixed metal oxides, perovskite structured semiconductors, metal (oxy)nitrides or composite electrodes offer the potential to either tailor the optical band gap or tune the conduction or valence band energetics. Recent work in this area is detailed here.

International audience; The solution-phase synthesis and cyclisation of three alpha,beta-peptoid octamers with differing side chain patterns is reported. One of these, compound C, showed a significantly greater resolution by NMR relative to the other two structurally related octamers. This observation was studied in detail by circular dichroism at a synchrotron light source to facilitate the correlation between the side chain patterns and conformational preference of these three peptoids. The X-ray crystal structure of cyclic octamer C, the first high-resolution structure for the α,β-peptoid backbone, was also obtained from methanol. Combined solid- and solution-phase studies allowed the identification of the N-2-(benzyloxy)ethyl side chain on the β-residue of the heterogeneous backbone as a key structural feature driving the increased conformational stability for octamer C

This article charts the development of the use of thin films of nanoparticulate WO3 and how they have been used to overcome problems associated with other photocatalytic materials and bulk WO3. Current technology is described and the authors' views on the outlook for future development is suggested.

UV--visible (UV-vis) absorption spectroscopy is widely used as a primary means of assaying concentrations and in characterizing the kinetics of reactions and chemical processes; it is ubiquitously used for chromatographic detection. Although currently somewhat less widely used as a first means of structural analysis, compared to spectroscopies such as nuclear magnetic resonance, it remains pre-eminent for a wide range of specialist areas, especially those involving distinctive chromophoric compounds such as dyes, indicators, and filters. Its ability to probe the electronic states of molecules also ensures its wide use for detailed physical studies. The focus of this article is on the qualitative and quantitative application of UV-vis spectroscopy to organic compounds and practical guidance for the preparation of samples, interpretation of spectra, and understanding of the variables that can occur or be utilized. Typical spectral data for representative classes of compound are indicated and discussed.

Sugar amino acids and their oligomers, known as carbopeptoids, are commonly studied as foldamers. However, study of their conformational preference is often challenging when the adopted conformations are extended and/or disordered. This study is the first to explore the disordered nature of such carbopeptoids by utilizing a family of 2,5-trans carbopeptoids. An array of spectroscopic techniques has been used to investigate the conformational preference of these carbopeptoids. However, using this data alone it has not been possible to assign conformational preference as an ordered extended conformation or as a disordered family of closely related conformations. Computational methods need to be employed to achieve reliable interpretation of the spectroscopic data. Chirality, 2008. © 2008 Wiley-Liss, Inc.

Photoelectrocatalysis driven by visible light offers a new and potentially powerful technology for the remediation of water contaminated by organo-xenobiotics. In this study, the performance of a visible light-driven photoelectrocatalytic (PEC) batch reactor, applying a tungsten trioxide (WO3) photoelectrode, to degrade the model pollutant 2,4-dichlorophenol (2,4-DCP) was monitored both by toxicological assessment (biosensing) and chemical analysis. The bacterial biosensor used to assess the presence of toxicity of the parent molecule and its breakdown products was a multicopy plasmid lux-marked E. coli HB101 pUCD607. The bacterial biosensor traced the removal of 2,4-DCP, and in some case, its toxicity response suggests the identification of transient toxic intermediates. The loss of the parent molecule, 2,4-DCP determined by HPLC, corresponded to the recorded photocurrents. Photoelectrocatalysis offers considerable potential for the remediation of chlorinated hydrocarbons, and that the biosensor based toxicity results identified likely compatibility of this technology with conventional, biological wastewater treatment.

The preparation of electrochromic films of mesoporous tungsten trioxide from tungstic acid and tungstic hexaethoxide precursors with the addition of an organic stabiliser via a sol-gel method is reported. These films have been structurally characterised and both the film morphology and crystalline composition of the films were found to be significantly dependent on the temperature at which the films were annealed and upon the choice of precursor. Films annealed at lower temperatures consisted of amorphous and hexagonal tungsten trioxide, whereas films annealed above 500 °C comprised solely of monoclinic WO3. The electrochromic activity of the films was found to be equally dependent on method of preparation, and both the composition and the structure of the WO3 films were shown to clearly influence the colouration efficiency of the films.

Solid state IR and Raman as well as aqueous solution state Raman spectra are reported for the linear di-amino acid peptide L-aspartyl-L-glutamic acid (L-Asp-L-Glu); the solution state Raman spectrum has also been obtained for the N,O-deuterated derivative. SCF-DFT calculations at the B3-LYP/cc-pVDZ level established that the structure and vibrational spectra of L-Asp-L-Glu can be interpreted using a model of the peptide with ten hydrogen-bonded water molecules, in conjunction with the conductor-like polarizable continuum solvation method. The DFT calculations resulted in the computation of a stable zwitterionic structure, which displays trans-amide conformation. The vibrational spectra were computed at the optimised molecular geometry, enabling normal coordinate analysis, which yielded satisfactory agreement with the experimental IR and Raman data. Computed potential energy distributions of the normal modes provided detailed vibrational assignments.

The development of sustainable hydrogen production is a key target in the further facilitation of a hydrogen economy. Solar hydrogen generation through the photolytic splitting of water sensitised by semiconductor materials is attractive as it is both renewable and does not lead to problematic by-products, unlike current hydrogen sources such as natural gas. Consequently, the development of these semiconductor materials has undergone considerable research since their discovery over 30 years ago and it would seem prescient to review the more practical results of this research. Among the critical factors influencing the choice of semiconductor material for photoelectrolysis of water are the band-gap energies, flat band potentials and stability towards photocorrosion; the latter of these points directs us to focus on metal oxides. Careful design of thin films of photocatalyst material can eliminate potential routes of losses in performance, i.e., recombination at grain boundaries. Methods to overcome these problems are discussed such as coupling a photoanode for photolysis of water to a photovoltaic cell in a “tandem cell” device.

Surface enhanced resonance Raman (SERRS) spectra of two water-insoluble metalloporphyrins, nickel(II) octaethylporphyrin (NiOEP) and nickel(II) tetraphenylporphyrin (NiTPP), are reported at a range of excitation energies and applied potentials. By comparison of the RR and SERRS spectra, it was determined that NiOEP adsorbs onto a silver electrode surface in an edge-on orientation, most probably with the meso-carbon atoms closest to the electrode surface. SERRS spectra were independent of applied potential, indicating that the porphyrin layer is stable throughout the potential range employed and that enhancement principally occurs through the electromagnetic mechanism. By contrast, the Raman spectra of NiTPP at the electrode surface suggest little affinity of NiTPP for the silver surface and possibly arise from RR scattering, rather than SERRS.