Thermal and utility properties of amide clay modifying agents

This article presents the results of investigation into receiving amide modification agents of smectic clays, used as nanofillers in polymer nanocomposites. Prepared materials were obtained on the base of terephthalic and isophthalic acids and simple aliphatic amines. Such structure makes them good layered silicates modifying agents as well as makes them well affiliate to structure of polymers containing aromatic, carbonyl, amide, etc. groups. Obtained compounds were introduced into clays’ structure in protonated form, according to formulated method. Conducted research confirmed that the modification of montmorillonite clay (MMT) with received compounds had taken place. In order to establish that fact elementary analysis and X-ray diffraction (XRD) methods were used. Modificator molecules must display thermal resistance in full range of polymer processing temperatures. To investigate these properties the Thermogravimetric analysis (TG) of obtained compounds was carried out. These studies indicate that among the obtained compounds there were the ones with thermal stability over 523 K. Thermal resistance makes it possible for these substances to be used in poly(ethylene terephthalate) processing.     

Radiation Damage in Macromolecular Crystallography

Interest in radiation damage to macromolecules during structural experiments has a long history dating back to 1962, when the first room-temperature study of the phenomenon was carried out on crystals of myoglobin [1 C.C.F. Blake and D.C. Philips, Vienna: International Atomic Energy Agency, 183–191 (1962). [Google Scholar]], and this interest has not abated over the last few years, since there remains a need to understand both the parameters that affect radiation damage progression and also the artifacts produced by it. Although there is now a growing body of literature pertaining to this topic, clear and foolproof methods for experimenters to routinely minimize damage have yet to emerge. Additionally, radiation damage is also a concern and limiting problem in other methods used in structural biology, such as electron microscopy [2 A. Bartesaghi, Proceedings of the National Academy of Sciences of the United States of America 111, 11709–11714 (2014).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]] and SAXS [3 S. Kuwamoto, S. Akiyama, and T. Fujisawa, J Synchrotron Radiat 11, 462–468 (2004).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar], 4 S.P. Meisburger, Biophys J 104, 227–236 (2013).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]]. However, the recently available free electron lasers (FELs) have presented the possibility and promise that samples will give “diffraction before destruction”; is this indeed the “cure” for the challenges of radiation damage?     

Internal waves from a body accelerating in a thermocline

Many papers study the steady wave system around bodies moving in thermoclines but little attention has been given to unsteady wave systems. This paper concentrates on the unsteady wave systems around accelerating bodies in thermoclines. The wave shapes are calculated using a theory derived from a dispersion relation based on an exp-tanh density profile. All modes of oscillation can be determined and it is shown that for the lowest mode both oblique and transverse waves occur whereas for the higher modes the presence of transverse waves depends on the background conditions and on the speed of the body. Cauchy-Poisson impulsive start waves are included. The theoretical wave shapes compare quite well with those calculated using finite-difference formulations of the full Navier-Stokes equations when a body accelerates from rest.It is also shown how the dispersion relation =N sin together with the WKB approximation can produce the same plan-view wave forms as those obtained using the thermocline wave dispersion relation given by [17, 30].     

The molecular basis of pharmacological chaperoning in human α-galactosidase

Fabry disease patients show a deficiency in the activity of the lysosomal enzyme α-galactosidase (α-GAL or α-Gal A). One proposed treatment for Fabry disease is pharmacological chaperone therapy, where a small molecule stabilizes the α-GAL protein, leading to increased enzymatic activity. Using enzyme kinetics, tryptophan fluorescence, circular dichroism, and proteolysis assays, we show that the pharmacological chaperones 1-deoxygalactonojirimycin (DGJ) and galactose stabilize the human α-GAL glycoprotein. Crystal structures of complexes of α-GAL and chaperones explain the molecular basis for the higher potency of DGJ over galactose. Using site-directed mutagenesis, we show the higher potency of DGJ results from an ionic interaction with D170. We propose that protonation of D170 in acidic conditions leads to weaker binding of DGJ. The results establish a biochemical basis for pharmacological chaperone therapy applicable to other protein misfolding diseases.     

Radiative decays of unbound levels in 20Ne

Nine levels in the range 8.7 to 12.5 MeV in ²⁰Ne have been investigated with the ¹⁶O(α, γ)²⁰Ne and ¹⁶O(α, α')¹⁶O¹(6.13 MeV) reactions using a differentially pumped windowless gas target. Three of the levels have not been observed previously in these reactions, and new information has been obtained for most of the others. In particular, the 11.27 MeV 1^? level is shown to have T = 1, a result of relevance to a proposed parity violation experiment, and the analogue of the 1.97 MeV (3^?T = 1) level in ²⁰F is shown to lie at 12.25 MeV in ²⁰Ne rather than at 12.39 MeV as proposed previously. In addition, the 12.25 MeV level has a width Γ < 1 keV, in contrast to the value Γ ～ 5 keV reported in other work. The electromagnetic transition rates for positive parity T = 1 states in ²⁰Ne are compared with shell-model calculations.     

Absorbed dose calculations for macromolecular crystals: improvements to RADDOSE

Radiation damage is an unwelcome and unavoidable aspect of macromolecular crystallography. In order to quantify the extent of X‐ray‐induced changes, knowledge of the dose (absorbed energy per unit mass) is necessary since it is the obvious metric against which to plot variables such as diffraction intensity loss and B factors. Significant improvements to the program RADDOSE for accurately calculating the dose absorbed by macromolecular crystals are presented here. Specifically, the probability of energy loss through the escape of fluorescent photons from de‐excitation of an atom following photoelectric absorption is now included. For lighter elements, both the probability of fluorescence and of its subsequent escape from the crystal are negligible, but for heavier atoms the chance of fluorescence becomes significant (e.g. 30% as opposed to Auger electron decay from a K‐shell excited iron atom), and this has the effect of reducing the absorbed dose. The effects of this phenomenon on dose calculations are presented for examples of crystals of an iron‐containing protein, 2‐selenomethionine proteins, a uranium derivatised protein, and for a nucleic acid sample. For instance, the inclusion of fluorescent escape results in up to a 27% decrease in the calculated absorbed dose for a typical selenomethionine protein crystal irradiated at the selenium K‐edge.     

Influence of ozone treatment on structure and thermal properties of bis-2-hydroxyethyl terephthalate-based copolymers

Polyesters are a particularly interesting group of polymers because of their ester bonds in the main chain, which are sensitive to degradation. It has been shown that aromatic polyesters [eg. poly(ethylene terephthalate) (PET)] can be degraded when they are copolymerized with aliphatic polyesters. In this regard, the objective of our previous study was to obtain and investigate new copolymers with some fragments of PET and its hydrolytic degradation. In this work, the impact of ozone degradation on properties of bis-2-hydroxyethyl terephthalate-based copolymers was researched. Apart from the bis-2-hydroxyethyl terephthalate, the copolymers comprised oligomers of lactic acid and glycolic acid in different combination. During ozone degradation, samples were kept for 24 h in atmosphere containing 0.51 vol.% of ozone. Structure changes were determined by means of FTIR spectroscopy. In the IR spectra of ozonised samples, new bonds characteristic for ozonised polymers were observed. Thermal properties of copolymers before and after degradation process were reviewed based on differential scanning calorimetry (DSC) and thermogravimetry. DSC results revealed that melting point increased, especially for copolymers displaying higher quantity of PET units.     

Synthesis of alkylcarbazole aminoderivatives

New alkylcarbazole aminoderivatives were prepared with various alkyl chain lengths. Syntheses were evaluated and procedures simplified. Producing alkylcarbazole aminoderivatives is a two‐step process, where—in the first step—alkycarbazol is obtained in the alkyl chain substitution reaction and the appropriate aminoderivative of alkylcarbazole is synthesized in direct amination of aromatic compounds as the second step. The products were verified with nuclear magnetic resonance analysis, and general thermal properties were determined by thermogravimetric analysis. Alkylcarbazole aminoderivatives are amphiphilic molecules, therefore expanding the list of known surfactants, compatibilizing agents, and other surface modifiers. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:1–4, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/.20742     

Thermal properties of nanocomposites based on polyethylene and n-heptaquinolinum modified montmorillonite

The aim of the research was obtaining and application of smectic clay modifying agent. The organophilic clay is used as nanofiller in polymer nanocomposites [1]. A microwave-assisted reaction led to obtaining N-heptaquinolinum, which is amphiphilic compound, containing both hydrophobic (alkyl and aromatic) and hydrophilic sections in its structure [2]. N-heptaquinolinum was used as a montmorillonite clay modifying agent. Modification was carried out in formulated way [3, 4]. Modification efficiency was determined by X-ray diffraction (XRD) analysis and elementary analysis. Organophilic clay (Ch7) was introduced, using the extrusion method, into polyethylene matrix in different mass relations (1.5, 3 and 5?%) [3]. The structure of obtained materials was studied by means of XRD and SEM. To evaluate potential applications thermal properties of received nanocomposites were tested with thermogravimetric analysis and differential scanning calorimetry. The thermal stability of PE/clay composites can be improved in the case of loading 1.5 and 5?mass%.