Purification and characterization of lamb pregastric lipase

Lamb pregastric lipase was purified from a commercial source using delipidation, solubilization with KSCN, acid-precipitation, pepsin-digestion, affinity chromatography with agarose-Cibacron Blue F3GA, gel filtration, and elution from a native 10% (w/v) polyacrylamide gel. The enzyme had a single subunit of 68,000 Da with maximum esterase activity when measured at pH 6.0 and 30 degrees C. The enzyme preferentially hydrolyzed short- and medium-chain (C4, C6, and C8) synthetic esters and short-chain (C4 and C6) monoacid triglycerides. The NH2-terminal sequence demonstrated high homology with gastric and lingual lipases.     

Switchable electrical conductivity in a three-dimensional metal–organic framework via reversible ligand n-doping

Redox-active metal–organic frameworks (MOFs) are promising materials for a number of next-generation technologies, and recent work has shown that redox manipulation can dramatically enhance electrical conductivity in MOFs. However, ligand-based strategies for controlling conductivity remain under-developed, particularly those that make use of reversible redox processes. Here we report the first use of ligand n-doping to engender electrical conductivity in a porous 3D MOF, leading to tunable conductivity values that span over six orders of magnitude. Moreover, this work represents the first example of redox switching leading to reversible conductivity changes in a 3D MOF.

Redox-active ligands are used to reversibly tune electrical conductivity in a porous 3D metal–organic framework (MOF).     

Bioconversion of acrylonitruke to acrylamide using a thermostable nitrile hydratase

Although providing an attractive route for production of crrylamide from acrylonitrile, utilization of nitrile hydratase en zymes has been limited by the requirement for low temperatu rebioconversion conditions. Thisrreportsummarizes a search for thermostable nitrile hydratases from aerobic moderate thermophiles screened for ability to grow on acrylonitrileatt concentrations to 1% at elevated temperatures. A new isolate Bacillus sp. BR449 constitutively expresses a thermostble nitrile hydratase with properties iccluding low substrate inhibition and broad temperature range with optimal activity at 55°C. With prolonged exposure, BR449 nitrile hydratase exhibited temperature-dependent inactivation by acrylonitrile, which is attributed to alkylation of nucleophilic sites on the enzymes/     

Mechanistic aspects of photoinactivation of Candida albicans by exogenous porphyrins

The mechanism of photoinactivation of Candida albicans by 3.5 μM uncharged, cationic or anionic porphyrins under blue light (407-420 nm) was found to be dependent on the uptake of porphyrins into yeast cells, and was also dependent on the presence or absence of proteins in the photosensitization medium. In a very protein-rich medium, a decrease in viability was observed only with the uncharged porphyrin. Photoinactivation by uncharged or cationic porphyrins in a protein-poorer medium resulted in total eradication, whereas no significant decrease was observed with the anionic porphyrin. Phototreatment in PBS resulted in eradication with all three porphyrins. X-ray microanalysis after phototreatment by the uncharged or cationic porphyrins in the protein-poor medium exhibited ion loss, indicating cell-membrane damage. Transmission electron microscopy indicated cellular and chromosomal damage. No ion loss or cell damage was observed in this medium with the anionic porphyrin. The efficiency of photoeradication of C. albicans is dependent on porphyrin uptake, which might lead (upon illumination) to processes that facilitate the formation of reactive oxygen species that damage the cells. Uptake of charged porphyrins is dependent on protein quantity and quality in the photosensitization microenvironment. This fact must be taken into account when using charged photosensitizers.     

Cobalt activation of Bacillus BR449 thermostable nitrile hydratase expressed in Escherichia coli

Expression of nitrile hydratase enzymes utilized in a new “green” process for acrylamide production has proven difficult in Escherichia coli owing to lack of a cobalt transport system to introduce the required cobaltion into this host. We describe the expression of a thermostable nitrile hydratase from a moderatethermophile Bacillus sp. BR449 in E. coli in which the cobaltrequired for enzyme activation is introduced by incubation, of the apoenzyme in the presence of Co⁺⁺ ion at 50°C, yielding active and thermostable, enzyme.     

Investigation of transverse galloping in the presence of structural nonlinearities: theory and experiment

Nonlinear Dynamics - We formulate and experimentally validate a theoretical reduced-order model for the transverse galloping of nonlinear structures, namely a pair of identical, parallel-oriented...     

In vitro inhibition of protein glycation and advanced glycation end products formation by hydroethanolic extract and two fractions of Simaba trichilioides roots

Abstract

Long-term hyperglycemia maintenance is responsible for increased protein glycation and formation of advanced glycation end products (AGEs), both are associated with the onset of diabetes mellitus complications. Efforts have been made to discover new agents having antiglycation potential. The aim of this study was to investigate the effects of the hydroethanolic extract and the ethyl acetate and methanolic fractions of Simaba trichilioides roots on the formation of AGEs. In an in vitro model system of protein glycation, incubations with hydroethanolic extract, ethyl acetate or methanolic fractions of S. trichilioides decreased the fluorescent AGEs, and markers of tyrosine and tryptophan oxidation. Protein crosslinking was reduced in the presence of the ethyl acetate fraction of S. trichilioides. Simaba trichilioides roots seem to be a promising source of compounds having ability to prevent glycoxidation changes, with potential applications in complementary therapies for management of diabetic complications.     

Tuning linear and nonlinear characteristics of a resonator via nonlinear interaction with a secondary resonator

Nonlinear Dynamics - We conside the dynamics of a nonlinear resonator that is nonlinearly coupled to a linear resonator that has a relatively short decay time. In this case, the secondary (linear)...     

Nonholonomic dynamics of the Twistcar vehicle: asymptotic analysis and hybrid dynamics of frictional skidding

Nonlinear Dynamics - The Twistcar vehicle is a classic example of a nonholonomic dynamical system. The vehicle model consists of two rigid links connected by an actuated rotary joint and supported...     

Theoretical aspects of transverse galloping

Nonlinear Dynamics - We investigate theoretical aspects of a reduced-order model for transverse galloping, which is derived directly from the full governing equations, i.e., the fluid mass and...