Extensional flow of hyaluronic acid solutions in an optimized micofluidic cross-slot device

We utilize a recently developed microfluidic device, the Optimized Shape Cross-slot Extensional Rheometer (OSCER), to study the elongational flow behavior and rheological properties of hyaluronic acid (HA) solutions representative of the synovial fluid (SF) found in the knee joint. The OSCER geometry is a stagnation point device that imposes a planar extensional flow with a homogenous extension rate over a significant length of the inlet and outlet channel axes. Due to the compressive nature of the flow generated along the inlet channels, and the planar elongational flow along the outlet channels, the flow field in the OSCER device can also be considered as representative of the flow field that arises between compressing articular cartilage layers of the knee joints during running or jumping movements. Full-field birefringence microscopy measurements demonstrate a high degree of localized macromolecular orientation along streamlines passing close to the stagnation point of the OSCER device, while micro-particle image velocimetry is used to quantify the flow kinematics. The stress-optical rule is used to assess the local extensional viscosity in the elongating fluid elements as a function of the measured deformation rate. The large limiting values of the dimensionless Trouton ratio, Tr ∼ O(50), demonstrate that these fluids are highly extensional-thickening, providing a clear mechanism for the load-dampening properties of SF. The results also indicate the potential for utilizing the OSCER in screening of physiological SF samples, which will lead to improved understanding of, and therapies for, disease progression in arthritis sufferers

Ligand-Induced Proton Transfer and Low-Barrier Hydrogen Bond Revealed by X-ray Crystallography

Ligand binding can change the pKa of protein residues and influence enzyme catalysis. Herein, we report three sub-Angstrom resolution X-ray crystal structures of CTX-M \u3b2-lactamase, representing three stages of the enzymatic pathway, apo protein (0.79 \uc5), pre-covalent complex (0.89 \uc5), and acylation transition state analog (0.84 \uc5). The binding of a non-covalent ligand induces a proton transfer from the catalytic Ser70 to the general base Glu166, and the formation of a low-barrier hydrogen bond (LBHB) between Ser70 and Lys73. QM/MM reaction path calculations determined the proton transfer barrier between Ser70 and Lys73 to be 1.53 kcal/mol, further confirming the presence of a LBHB. This LBHB is absent in the other two structures. Our data represents the first evidence of a direct and transient LBHB stabilizing a nucleophilic serine, as hypothesized by Cleland and Kreevoy. These results have important implications for the study of enzyme mechanisms as well as protein-inhibitor interactions

Crystal Structures of (\u3cem\u3eZ\u3c/em\u3e)-5-[2-(benzo[\u3cem\u3eb\u3c/em\u3e]thiophen-2-yl)-1-(3,5-dimethoxyphenyl)ethenyl]-1\u3cem\u3eH\u3c/em\u3e-tetrazole and (\u3cem\u3eZ\u3c/em\u3e)-5-[2-(benzo[\u3cem\u3eb\u3c/em\u3e]thiophen-3-yl)-1-(3,4,5-trimethoxyphenyl)ethenyl]-1\u3cem\u3eH\u3c/em\u3e-tetrazole

(Z)-5-[2-(Benzo[b]thio­phen-2-yl)-1-(3,5-di­meth­oxy­phen­yl)ethen­yl]-1H-tetrazole methanol monosolvate, C19H16N4O2S·CH3OH, (I), was prepared by the reaction of (Z)-3-(benzo[b]thio­phen-2-yl)-2-(3,5-di­meth­oxy­phen­yl)acrylo­nitrile with tri­butyl­tin azide via a [3 + 2]cyclo­addition azide condensation reaction. The structurally related compound (Z)-5-[2-(benzo[b]thio­phen-3-yl)-1-(3,4,5-tri­meth­oxy­phen­yl)ethen­yl]-1H-tetra­zole, C20H18N4O3S, (II), was prepared by the reaction of (Z)-3-(benzo[b]thio­phen-3-yl)-2-(3,4,5-tri­meth­oxy­phen­yl)acrylo­nitrile with tri­butyl­tin azide. Crystals of (I) have two mol­ecules in the asymmetric unit (Z′ = 2), whereas crystals of (II) have Z′ = 1. The benzo­thio­phene rings in (I) and (II) are almost planar, with r.m.s deviations from the mean plane of 0.0084 and 0.0037 Å in (I) and 0.0084 Å in (II). The tetra­zole rings of (I) and (II) make dihedral angles with the mean planes of the benzo­thio­phene rings of 88.81 (13) and 88.92 (13)° in (I), and 60.94 (6)° in (II). The di­meth­oxy­phenyl and tri­meth­oxy­phenyl rings make dihedral angles with the benzo­thio­phene rings of 23.91 (8) and 24.99 (8)° in (I) and 84.47 (3)° in (II). In both structures, mol­ecules are linked into hydrogen-bonded chains. In (I), these chains involve both tetra­zole and methanol, and are parallel to the b axis. In (II), mol­ecules are linked into chains parallel to the a axis by N—H⋯N hydrogen bonds between adjacent tetra­zole rings

Detailed Bathymetric Surveys in the Central Indian Basin

Over 420,000 line kilometers of echo-sounding data was collected in the Central Indian Basin. This data was digitized, merged with navigation data and a detailed bathymetric map of the Basin was prepared. The Basin can be broadly classified into three regions as high relief area, medium relief area and plain area represented by western, eastern and central portions of the Basin, respectively. The bathymetric map prepared from this survey is the first of its kind for this region and will in the future be used as a base by navigators and researchers

Cervical Mucus Properties Stratify Risk for Preterm Birth

Background: Ascending infection from the colonized vagina to the normally sterile intrauterine cavity is a well-documented cause of preterm birth. The primary physical barrier to microbial ascension is the cervical canal, which is filled with a dense and protective mucus plug. Despite its central role in separating the vaginal from the intrauterine tract, the barrier properties of cervical mucus have not been studied in preterm birth. Methods and Findings: To study the protective function of the cervical mucus in preterm birth we performed a pilot case-control study to measure the viscoelasticity and permeability properties of mucus obtained from pregnant women at high-risk and low-risk for preterm birth. Using extensional and shear rheology we found that cervical mucus from women at high-risk for preterm birth was more extensible and forms significantly weaker gels compared to cervical mucus from women at low-risk of preterm birth. Moreover, permeability measurements using fluorescent microbeads show that high-risk mucus was more permeable compared with low-risk mucus. Conclusions: Our findings suggest that critical biophysical barrier properties of cervical mucus in women at high-risk for preterm birth are compromised compared to women with healthy pregnancy. We hypothesize that impaired barrier properties of cervical mucus could contribute to increased rates of intrauterine infection seen in women with preterm birth. We furthermore suggest that a robust association of spinnbarkeit and preterm birth could be an effectively exploited biomarker for preterm birth prediction.Massachusetts Institute of Technology. Charles E. Reed Faculty Initiative FundBurroughs Wellcome Fund (Preterm Birth Research Grant)National Science Foundation (U.S.). Graduate Research Fellowship Progra

Effective Extraction of Heavy Metals from their Effluents Using Some Potential Ionic Liquids as Green Chemicals

Synthesis of nine Task Specific Ionic liquids (TSILs), their characterization using 1H NMR spectral studies and other physical properties and potential applications in the removal of certain heavy metals such as Nickel, Iron, Zinc, Copper and Lead has been studied. The removal of these heavy metals from the industrial effluents / contaminated water bodies using these ionic liquids has been proved to be more successful than conventional methods such as precipitation, cementation, reverse osmosis, ion exchange and adsorption

Eye of horus – Erratum revealed a prescription survey

Background: The aim of this study was to survey the quality and the content of prescription of practitioners and also assess the legibility of alphabet, and short form of the drug.Methods: A survey of all prescription received by the patients that were written by general practitioners, consulting physicians and dentists in and around Virajpet and Madikeri (south Coorg) was included.The prescriptions were photocopied and returned back to the patients. The prescription was scored and analyzed by a qualified medical investigator.Results: A total of 171 prescription samples were collected. In most prescriptions, one or more aspects of patient’s personal details were missing. Concerned doctor’s details also lacked in most cases. 40.3% of the prescriptions were obtained wherein short form of the drug was used for prescribing drug. Legibility of alphabet was also evaluated and the most confusing letter noted in our study was letter “C”; followed by A, T, S, O, G, and D in this study the letter Rx was written in 7% of the prescription and in 19% prescription it was replaced by word “Adv” and 74% of prescription without symbol of Rx.Conclusions: The present data shows most prescriptions in the study was inadequate and important details were lacking, legibility of prescription was poor in rating

Relation between land cover parameters and BRDF model coefficients: a case study using MODIS BRDF product over parts of Western India

In this paper, the BRDF data product from Moderate Resolution Imaging ,Spectrometer (MODIS) on EOS is used along with IRS - ID WiFS and IRS ID LISS-III sensors to explore relations between land cover classes, LAI and the BRDF model coefficients. The IRS -ID WiFS data was aggregated to the spatial resolution of MODIS (- l krn) and the three BRDF model parameters corresponding to isotropic, volume and geometric components of surface reflectance for sand, water and crop classes are extracted and analyzed in this study. Using field measurements of LAI carried out at the Central State Farm, Suratgarh, Rajasthan along with LISS-lII image of the same area, an LAI image of the farm was generated and the LA! values were correlated with the three MODIS BRDF model parameters. Small but significant negative correlations (- 0.5) were found between LAI and angle independent isotropic term at both red and near infrared wavelengths and higher significant correlations were observed among the BRDF model coefficients

Coarse-Grained Descriptions

Coarse-grained approaches are widely considered for analyzing multiatomic systems. They are based on the used of simplified interatomic potentials, that allow deriving most of the macroscopic thermomechanical properties of materials. Molecular dynamics can coarsened at its turn leading to dissipative particle dynamics and multi-particle collision dynamics. Finally, for addressing larger systems, Langevin and diffusion equations are usually considered; the last in very close connection with Brownian mechanics and its fractional variant. This chapter revisits all these physical descriptions