Search results for "Function"
showing 10 items of 14432 documents
Epoxide Hydrolases: Structure, Function, Mechanism, and Assay
2005
Epoxide hydrolases are a class of enzymes important in the detoxification of genotoxic compounds, as well as in the control of physiological signaling molecules. This chapter gives an overview on the function, structure, and enzymatic mechanism of structurally characterized epoxide hydrolases and describes selected assays for the quantification of epoxide hydrolase activity.
Catalytic Diastereo- and Enantioselective Synthesis of 2-Imidazolinones.
2019
Chiral cyclic ureas (2-imidazolinones) were prepared by the reaction of nitrones and isocyanoacetate esters using a multicatalytic system that combines a bifunctional Brønsted base-squaramide organocatalyst and Ag+ as a Lewis acid. The reaction could be achieved with a range of nitrones derived from aryl- and cycloalkylaldehydes with moderate diastereo- and good enantioselectivity. A plausible mechanism involving an initial formal [3 + 3] cycloaddition of the nitrone and isocyanoacetate ester, followed by rearrangement to an aminoisocyanate and cyclization to the imidazolinone, is proposed.
Viscosity of Polymer Solutions over the Full Range of Composition: A Thermodynamically Inspired Two-Parameter Approach
2015
The approach yields the following relation for the relative viscosity η rel as a function of polymer concentration c (mass/volume): ln ηrel = c/(1 + pc + qc2). Reduced concentrations c (defined as c = c[η], where [η] is the intrinsic viscosity) are used instead of c to incorporate thermodynamic information. The parameters p and q account for changes in the free volume of the solvent caused by the polymer. The analysis of literature data for seven very dissimilar systems discloses the following common feature: p > 0 and q < 0. This means that the curves in the plots of ln ηrel as a function of c are normally located below the tangent at low c and above it at high c. The values of p and q cor…
Silicatein: from chemical through enzymatic silica formation, to synthesis of biomimetic nanomaterials
2012
Silicateins are the enzymes that had been identified in sponges, then sequenced and expressed. They are not only the enzymes facilitating biosilica synthesis but also function as structure-guiding and structure-forming proteins. The three minireviews highlight the principles of silicatein-mediated biosilica formation and outline the bionic strategies which might be used for the design and fabrication of novel materials.
Understanding Noncovalent Interactions of Small Molecules with Carbon Nanotubes
2017
We combine experimental methods, density functional theory (DFT) calculations, and molecular dynamics (MD) simulations in the quantitative analysis of noncovalent interactions between (6,5)-enriched single-walled carbon nanotubes (SWNTs), as hosts, and a set of pyrene derivatives with different electronic properties and surface areas, as guests. The experiments and calculations were carried out in two solvents with markedly different polarities, namely 1,1',2,2'-tetrachloroethane (TCE) and N,N-dimethylformamide (DMF). Our results show that dispersion forces govern the supramolecular association of small molecules with (6,5)-SWNTs, with negligible contributions from ground-state charge-trans…
Relationship between conformation and physicochemical properties of polypeptides. I. Synthesis of homo- and co-oligopeptides by the liquid-phase meth…
1980
The synthesis of the following oligo- and co-oligopeptides by the liquid-phase method is described: (L-Met)15 (I), [L-Glu(OBzl)]20 (II), (L-Val)8-Gly (IV), (L-Ile)8-Gly (V), (L-Ile)4-Gly-(L-Ile)4 (VI), (L-Ile)4-Pro-(L-Ile)4 (VII), (L-Met)5-L-Pro-(L-Met)5 (VIII), [L-Glu(OBzl)]7-L-Pro-[L-Glu(OBzl)]7 (IX). The oligomers are covalently bound to bifunctional polyethylene glycol (PEG) and monofunctional PEG-M of Mr 5 × 103−2 × 104. Analytical controls were carried out after each step of synthesis in order to ensure quantitative coupling yields. All products could be obtained in high purity as indicated by amino acid analysis, thin-layer chromatography and chiroptical methods. The solubility of th…
Electrochemical synthesis of sulfamides.
2021
Herein we demonstrate the first electrochemical synthesis protocol of symmetrical sulfamides directly from anilines and SO2 mediated by iodide. Sulfamides are an emerging functional group in drug design. Highlights are the direct use of SO2 from a stock solution and no necessity of any supporting electrolyte. Overall, the reaction has been demonstrated for 15 examples with yields up to 93%.
Separation studies of amino acids, proteins and enzymes on bonded 1,2-dihydroxy-, 1,2-hydroxylamino-and amino silica packings
1979
1,2-dihydroxy-3-propoxypropyl (HPPS), 1-amino-2-hydroxy-3-propoxypropyl (AHPS) and 1-aminoethyl-3-aminopropyl (AEAPS) silica were synthesized by means of both a surface modification procedure (I) and a bulk modification procedure (II). Method (I) gave a surface concentration, α, of functional groups of 2–3 μmole/m2, whereas method (II) gave values up to 5 μmole/m2. Retention times, peak asymmetries and plate heights of thiamine and ascorbic acid eluted with aqueous buffer solutions ranging from pH 5.3 to 9.2 gave only a±5% variation over periods of 12 hours and more. The recoveries of selected enzymes and proteines examined under static and dynamic conditions were between 60% and 100% depen…
Heterogeneity at the glass transition: a review
1999
Theoretical concepts and experimental evidence of heterogeneity in glass-forming liquids and polymers are reviewed. The main purpose is to provide an introduction to theoretical developments and recent experiments which have led to rapidly increasing knowledge. Realizing that there is no consensus in regard to the various scenarios of the glass transition starting from rather different assumptions we try to give a balanced overview although we also compare and interrelate some of the approaches. The experimental part describes recent nuclear magnetic resonance, dielectric, and optical experiments from which dynamically distinguishable subensembles can be selected thus proving the existence …
The glass transition in (KI)0.5(ND4I)0.5 mixed crystals as studied by deuteron spin-lattice relaxation
1993
Abstract Nuclear spin resonance has been used to study the deuteron magnetization recovery in (KI)0.5(ND4I)0.5 mixed crystals. At high temperatures the spin-lattice-relaxation is exponential. For T ⪅ 45 K deviations from this simple behaviour occur, signalling the onset of spatial inhomogeneities due to the formation of an orientational glass. The results demonstrate that the transition of (KI)0.5(ND4I)0.5 into the glassy state is driven by the freezing of random bonds.