Investigating the interactions of the first 17 amino acid residues of Huntingtin with lipid vesicles using mass spectrometry and molecular dynamics

The first 17 amino acid residues of Huntingtin protein (Nt17 of htt) are thought to play an important role in the protein's function; Nt17 is one of two membrane binding domains in htt. In this study the binding ability of Nt17 peptide with vesicles comprised of two subclasses of phospholipids is studied using electrospray ionization ‐ mass spectrometry (ESI‐MS) and molecular dynamics (MD) simulations. Overall, the peptide is shown to have a greater propensity to interact with vesicles of phosphatidylcholine (PC) rather than phosphatidylethanolamine (PE) lipids. Mass spectra show an increase in lipid‐bound peptide adducts where the ordering of the number of such specie is 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) > 1‐palmitoyl‐2‐oleoyl‐glycero‐3‐phosphocholine (POPC) > 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3 phosphoethanolamine (POPE). MD simulations suggest that the compactness of the bilayer plays a role in governing peptide interactions. The peptide shows greater disruption of the DOPC bilayer order at the surface and interacts with the hydrophobic tails of lipid molecules via hydrophobic residues. Conversely, the POPE vesicle remains ordered and lipids display transient interactions with the peptide through the formation of hydrogen bonds with hydrophilic residues. The POPC system displays intermediate behavior with regard to the degree of peptide‐membrane interaction. Finally, the simulations suggest a helix stabilizing effect resulting from the interactions between hydrophobic residues and the lipid tails of the DOPC bilayer.     

A Short and Elegant Synthesis of (±)‐Streptopyrrolidine

A brief and efficient approach for the synthesis of (±)‐5‐benzyl‐4‐hydroxy‐2‐pyrrolidine ( 1 ) from phenylalanine racemate is described. The key step is the stereocontrolled reduction of the keto functionality of benzylated pyrrolidinone intermediate ( 6 ) via sodium borohydride in carboxylic acid medium furnishing both (R,R)‐ and (S,S)‐configured diastereomers. The natural (R,R) enantiomer ( 2 ), however, crystallized out from its racemic mixture. Structure of 2 was confirmed by NMR, IR, elemental analyzer, and single crystal X‐ray crystallographic techniques.     

A new signal processing method to observe weak P and O NMR peaks

In NMR spectroscopy, situations may arise where sample concentrations are below the threshold for FT NMR detection, or sample lability constrains allowable acquisition times. In ³¹P NMR, for example, observation of ¹³C satellites may not be practical under given conditions. For ¹⁷O NMR, which is useful to characterize ¹⁷O-labeled phosphate derivatives, similar considerations may apply, and added factors are the cost of isotopically enriched samples and the requirement to obtain spectra at relatively high temperatures if narrow spectral peak line widths are desired. We report here application of a new signal processing method [S.D. Kunikeev, H.S. Taylor, J. Phys. Chem. A 108, 2004 743] to observation of weak ³¹P and ¹⁷O NMR peaks.     

Optimization and validation of RP-HPLC-UV method with solid-phase extraction for determination of buparvaquone in human and rabbit plasma: application to pharmacokinetic study

A simple, sensitive and specific reversed-phase high-performance liquid chromatographic method with UV detection at 251 nm was developed for quantitation of buparvaquone (BPQ) in human and rabbit plasma. The method utilizes 250 microL of plasma and sample preparation involves protein precipitation followed by solid-phase extraction. The method was validated on a C18 column with mobile phase consisting of ammonium acetate buffer (0.02 m, pH 3.0) and acetonitrile in the ratio of 18:82 (v/v) at a flow rate of 1.1 mL/min. The calibration curves were linear (correlation coefficient>or=0.998) in the selected range. The method is specific and sensitive with limit of quantitation of 50 ng/mL for BPQ. The validated method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions and BPQ was found to be stable. Partial validation studies were carried out using rabbit plasma and intra- and inter-day precision and accuracy were within 7%. This method is simple, reliable and can be routinely used for preclinical pharmacokinetic studies for BPQ.     

Simultaneous determination of potassium clavulanate and cefixime in synthetic mixtures by high-performance liquid chromatography

A simple, precise, and sensitive high-performance liquid chromatographic method was developed and validated for the simultaneous determination of potassium clavulanate and cefixime in synthetic mixture form. The analytes were separated on a C18 column by using 0.03 M disodium hydrogen phosphate buffer (pH 6.5)-methanol (84 + 16, v/v) as the mobile phase with detection at 220 nm. The method exhibited high sensitivity and good linearity in the concentration ranges of 12.5-62.5 and 20-100 microg/mL for potassium clavulanate and cefixime, respectively. The total run time for the 2 components was <8 min, and the average recovery was >101.5% with a relative standard deviation of <1.0%. The proposed method was validated according to guidelines of the International Conference on Harmonization by evaluation of linearity, recovery, selectivity, robustness, limits of detection and quantitation, and within- and between-day precision. The results obtained for the synthetic mixture show that the method is highly precise and accurate for the simultaneous determination of potassium clavulanate and cefixime.     

Chaos and complexity in mine grade distribution series detected by nonlinear approaches

In this article, the underlying dynamics of treating grade distribution is interpreted as a chaotic system instead of a stochastic system for a better understanding. Here, we study the behavior of grade distribution spatial series acquired at the Chadormalu mine in Bafgh city of Iran to distinguish the possible existence of low‐dimensional deterministic chaos. This work applies a variety of nonlinear techniques for detecting the chaotic nature of the grade distribution spatial series and adopts a nonlinear prediction method for predicting the future of the grade distributions. First, the delay time dimension is computed using auto mutual information function to reconstruct the strange attractors. Then, the dimensionality of the trajectories is obtained using Cao's method and, correspondingly, the correlation dimension method is adopted to quantify the embedding dimension. The low embedding dimensions achieved from these methods show the existence of low dimensional chaos in the mining data. Next, the high sensitivity to initial conditions is evaluated using the maximal Lyapunov exponent criterion. Positive Lyapunov exponents obtained demonstrate the exponential divergence of the trajectories and hence the unpredictability of the data. Afterward, the nonlinear surrogate data test is done to further verify the nonlinear structure of the grade distribution series. This analysis provides considerable evidence for the being of low‐dimensional chaotic dynamics underlying the mining spatial series. Lastly, a nonlinear prediction scheme is carried out to predict the grade distribution series. Some computer simulations are presented to illustrate the efficiency of the applied nonlinear tools. © 2016 Wiley Periodicals, Inc. Complexity 21: 355–369, 2016     

Lanthanide complexes with pyridine-2,6-dicarboxylic acid: synthesis,crystal structure,thermal and magnetic properties of [LnPDA)2(PDAH2)] · (DMAH2)2(DMAH0.5)2

Mild solvothermal synthesis, structures, thermal and magnetic properties of coordination complexes [Ln(PDA)₂(PDAH₂)] · (DMAH₂)₂(DMAH_0.5)₂(I–IV) (PDA = pyrdine-2,6-dicarboxylate anion, DMAH = dimethylamine, Ln = Ce, Nd, Sm, and Ho) are described. The DMAH molecules in I–IV, generated in situ from hydrolysis of N,N-dimethylformamide, are responsible to assemble three dimensional coordination polymers through N–H···O and C–H···O hydrogen bonds. Distorted tricapped trigonal prismatic LnO₆N₃ geometry having 14 triangular faces is attributed to mean deviation of dihedral angles while nitrogen shows fairly triangular faces having dihedral angle close to 60°C (CIF files CCDC nos. 872065 (I), 872070 (II), 872069 (III), and 872066 (IV)). Curie–Weiss law and the overall magnetic behavior are typical for the presence of antiferromagnetic exchange coupling interactions between lanthanide. Thermal decomposition analyses reveal removal of ammonia and resultant complexes showthermal stability. Complexes have been further characterized by using elemental analyzer and FT-IR spectroscopy.     

Prebiotic Impacts of Soybean Residue (Okara) on Eubiosis/Dysbiosis Condition of the Gut and the Possible Effects on Liver and Kidney Functions

Okara is a white-yellow fibrous residue consisting of the insoluble fraction of the soybean seeds remaining after extraction of the aqueous fraction during the production of tofu and soymilk, and is generally considered a waste product. It is packed with a significant number of proteins, isoflavones, soluble and insoluble fibers, soyasaponins, and other mineral elements, which are all attributed with health merits. With the increasing production of soy beverages, huge quantities of this by-product are produced annually, which poses significant disposal problems and financial issues for producers. Extensive studies have been done on the biological activities, nutritional values, and chemical composition of okara as well as its potential utilization. Owing to its peculiar rich fiber composition and low cost of production, okara might be potentially useful in the food industry as a functional ingredient or good raw material and could be used as a dietary supplement to prevent varied ailments such as prevention of diabetes, hyperlipidemia, obesity, as well as to stimulate the growth of intestinal microbes and production of microbe-derived metabolites (xenometabolites), since gut dysbiosis (imbalanced microbiota) has been implicated in the progression of several complex diseases. This review seeks to compile scientific research on the bioactive compounds in soybean residue (okara) and discuss the possible prebiotic impact of this fiber-rich residue as a functional diet on eubiosis/dysbiosis condition of the gut, as well as the consequential influence on liver and kidney functions, to facilitate a detailed knowledge base for further exploration, implementation, and development.     

Morphology‐Dependent Electrochemical Properties of CuS Hierarchical Superstructures

Hierarchical superstructures formed by self‐assembled nanoparticles exhibit interesting electrochemical properties that can potentially be exploited in Li‐ion batteries (LIBs) as possible electrode materials. In this work, we tested two different morphologies of CuS superstructures for electrodes, namely, tubular dandelion‐like and ball‐like assemblies, both of which are composed of similar small covellite nanoparticles. These two CuS morphologies are characterized by their markedly different electrochemical performances, suggesting that their complex structures/morphologies influence the electrochemical properties. At 1.12 A g^?1, the cells made with CuS tubular structures delivered about 420 mAh g^?1, and at 0.56 A g^?1, the capacity was as high as about 500 mAh g^?1 with good capacity retention. Their ease of preparation and processing, together with good electrochemical performance, make CuS tubular dandelion‐like clusters attractive for developing low‐cost LIBs based on conversion reactions.     

The stability of a shearing viscous star with an electromagnetic field

We analyze the role of the electromagnetic field for the stability of a shearing viscous star with spherical symmetry. Matching conditions are given for the interior and the exterior metrics. We use a perturbation scheme to construct the collapse equation. The range of instability is explored in Newtonian and post Newtonian (pN) limits. We conclude that the electromagnetic field diminishes the effects of the shearing viscosity in the instability range and makes the system more unstable in both Newtonian and post Newtonian approximations.