Structural Study of the Partially Disordered Full‐Length δ Subunit of RNA Polymerase from Bacillus subtilis

The partially disordered δ subunit of RNA polymerase was studied by various NMR techniques. The structure of the well‐folded N‐terminal domain was determined based on inter‐proton distances in NOESY spectra. The obtained structural model was compared to the previously determined structure of a truncated construct (lacking the C‐terminal domain). Only marginal differences were identified, thus indicating that the first structural model was not significantly compromised by the absence of the C‐terminal domain. Various ¹⁵N relaxation experiments were employed to describe the flexibility of both domains. The relaxation data revealed that the C‐terminal domain is more flexible, but its flexibility is not uniform. By using paramagnetic labels, transient contacts of the C‐terminal tail with the N‐terminal domain and with itself were identified. A propensity of the C‐terminal domain to form β‐type structures was obtained by chemical shift analysis. Comparison with the paramagnetic relaxation enhancement indicated a well‐balanced interplay of repulsive and attractive electrostatic interactions governing the conformational behavior of the C‐terminal domain. The results showed that the δ subunit consists of a well‐ordered N‐terminal domain and a flexible C‐terminal domain that exhibits a complex hierarchy of partial ordering.     

Influence of particle size and fluid fraction on rheological and extrusion properties of crosslinked hyaluronic acid hydrogel dispersions

Crosslinked hyaluronic acid (HA) hydrogels are widely used in gel/HA fluid formulations as a viscosupplement to treat joint diseases; thus, it is important to characterize these hydrogels in terms of their particle size and to investigate the effects of the gel/fluid mixtures on their rheological properties and extrusion force. Hydrogels previously crosslinked with divinyl sulfone were sheared in an Ultra‐Turrax unit to produce particles with mean diameters ranging from 20 to 200 μm. Hydrogels with 75–100 μm mean diameters were also evaluated in dispersions containing a 20–40% mass fraction of HA fluid. The mean diameters were measured by laser light scattering and the rheological behavior was determined by oscillatory and steady measurements in parallel plate geometry. The HA hydrogels exhibited the typical behavior of so‐called weak gels, as analyzed by the storage and loss moduli G′ and G″, respectively. The viscoelasticity, the viscosity, and the extrusion force increased with the hydrogel particle size. The fluid phase dispersions decreased both moduli. At 40% fluid fraction, the gel characteristics were lost and the dispersion behaved as a fluid. Based on these results, the particle size and HA fluid fraction in hydrogel dispersions may be optimized to develop more efficient viscosupplement formulations. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dewetting and Adsorption in Homopolymer Films Containing Triblock Copolymers: Role of Chain Architecture and Anchoring Block Molar Fraction

Triblock copolymer additives are found to stabilize thin-film dewetting of B-type homopolymers with degree of polymerization (DOP) P deposited on silicon oxide. The triblock copolymers’ architectures are ABA and BAB, where A and B represent anchoring and nonadsorbing blocks with DOP's N _A and N _B, respectively. Upon adding 1 vol.% of the ABA additive, dewetting is only observed for anchoring block molar fractions, f _A, below 4%. Dewetting is arrested in films containing 1 vol.% ABA, BAB, or AB that have similar values of f _A ～ 8%, showing that chain architecture is not the only indicator of a successful additive. Compared with films containing diblock copolymers, the interfacial excess, z*, of triblock copolymers at the melt/substrate interface is relatively small as measured by low-energy forward-recoil spectrometry. Because adsorbed copolymers can reduce the capillary driving force for dewetting and participate in entanglements with matrix chains, the higher coverage and grafting density observed for diblock copolymers suggests that diblocks are more effective than triblocks in improving thin-film stability.     

From coffee industry waste materials to skin‐friendly products with improved skin fat levels

Spent coffee grounds (SCG), which are the residue obtained from the treatment of coffee with hot water or steam, can be used for industrial applications, due to the high content in lipids. The cosmetic products might be a suitable application for these types of residues because the barrier properties of the stratum corneum (SC) are largely dependent on the intactness of the lipid lamellae that surrounds the corneocytes. The purpose of this work was to assess the feasibility of using the lipid fraction of SCG extracted with supercritical carbon dioxide in the development of new cosmetic formulations with improved skin lipids (sebum) and hydration. The use of spent coffee lipid extract in cosmetic industry seems to be a suitable approach to recycle the wastes from coffee industry. Emulsion containing 10% of the lipid fraction of SCG (SpentCofOil cream) presented promising characteristics in the improvement of sebum skin levels with a good acceptance by consumers when compared to an emulsion containing 10% w/w of green coffee oil (GreenCofOil cream) and a placebo without coffee oil (NoCofOil cream). Practical applications: In this work, the authors develop and characterize a cream containing 10% of the lipid fraction of SCG extracted with supercritical carbon dioxide with improved skin lipids (sebum) and hydration.     

Spray-dried nanoparticle-loaded pectin microspheres for dexamethasone nasal delivery

Abstract

In this study, we present the development of an innovative dry powder dexamethasone (Dex) nasal delivery system comprising Dex-loaded lipid/alginate nanoparticles incorporated within pectin microspheres (Dex/NPs-loaded pectin microspheres; DNM). DNM microspheres were characterized by the mean diameter of 2.76?±?0.10?µm, zeta-potential of –36.2?±?1.1?mV, and drug loading of 3.3?±?0.3%. The morphology study revealed irregular microsphere surface forming external voids. In contact with simulated nasal fluid, DNM microspheres demonstrated desirable property of moderate swelling and ensured stronger mucoadhesion compared with conventional Dex-loaded pectin microspheres. The strategy of Dex incorporation within the lipid/alginate NPs resulted in prolonged Dex release in relation to Dex being directly entrapped within the conventional pectin microspheres. DNM microspheres showed excellent biocompatibility and rendered Dex permeation across the selected epithelial cell model similar to that of Dex solution. In conclusion, balanced biopharmaceutical properties of the proposed nasal Dex delivery system provides the potential for prolonged contact time with nasal mucosa, prolonged therapeutic effect, and improved patient compliance.     

Application of Modified Lignosulfonates in Adhesives for Insulation Board Manufacture Based on Mineral Wool

Extensive laboratory investigations and mill scale trials confirmed the applicability of ultrafiltrated high molecular weight Ca-ligno-sulfonates in adhesive composition with phenolic resin for insulation board manufacture based on mineral wool. Insulation materials produced with adhesive components with a formulation of lignosulfonate/PF resin between 10/90 and 30/70 have appropriate technical and commercial properties.     

Assessing Optical Properties and Refractive Index of Combustion Aerosol Particles Through Combined Experimental and Modeling Studies

The variability of optical properties of combustion particles generated from a propane diffusion flame under varying fuel-to-air (C/O) ratios was studied with a three-wavelength nephelometer, a particle soot absorption photometer, and an integrating sphere photometer. Information on particle size distribution, morphology, and elemental carbon to total carbon (EC/TC) ratios were obtained from scanning mobility particle sizer measurements, transmission electron microscopy analyses, and thermal-optical analyses. Particles generated under a low C/O ratio (0.22) showed high elemental carbon fraction (EC/TC = 0.77) and low brown carbon to equivalent black carbon (BrC/EBC) ratio (0.01), and were aggregates composed of small primary particles. Rayleigh–Debye–Gans theory reproduced experimental single-scattering albedo, ω, absorption, and scattering Ångström exponents within 56, 3, and 18%, respectively. In contrast, particles produced under a high C/O ratio (0.60) showed low elemental carbon fraction (EC/TC = 0.09) and high BrC/EBC ratio >100, and were smaller and spherical in shape. Their optical properties were better modeled with Mie theory. By minimizing the difference between calculated and measured ω and Ångström exponents, refractive indices of OC at three visible wavelengths were deduced. Contrary to the widely accepted assumption that refractive index of BC is wavelength independent, BC-rich particles exhibited absorption Ångström exponent >1.0 which implies some degree of wavelength dependence.

Copyright 2015 American Association for Aerosol Research     

Thermodynamics of Nitric Acid Extraction with Iso-Butanol. I. Water Activity In Iso-Butanol

A numerical procedure was employed to evaluate hydrated water attached to the extractable nitric acid/iso-butanol complex. The hydratation number was found to be 11, a value favourable in comparison to the hydratation numbers published for straight chain alcohols extractants. Of several tested approaches, the fourth order interaction Scatchard equation offers water activity coefficients in the alcohol phase which are in close agreement with the measured ones.     

Siting and Distribution of Framework Aluminium Atoms in Silicon-Rich Zeolites and Impact on Catalysis

Siting of Al atoms in the framework T sites, in zeolite rings and channel/cavity system, and the distribution of Al atoms between single Al atoms and close Al atoms in various Al-O-(Si-O)_n-Al sequences in Si-rich zeolites represent key parameters controlling properties of counter ion species. Framework Al siting and distribution is not random or controlled by simple rules and depends on the conditions of the zeolite synthesis. Al in Al-O-(Si-O)₂-Al in one 6-MR and single Al atoms predominate in Si-rich zeolites and their population can be varied to a large extent. The siting and distribution of framework Al atoms dramatically affect catalytic activity/selectivity both of protonic and transition metal ion-containing zeolite catalysts.