Search results for "substrate"

Chemistry of Enzyme Visualization

1994

The basic principle of enzyme visualization in situ is to present an enzyme with a solution containing an enzyme specific substrate. Demonstration of an enzyme is achieved if the catalytic action of the enzyme on this substrate produces a coloured reaction product. Often, however, the primary reaction products are colourless and require coupling with a visualizing agent to generate a coloured, preferably insoluble, final reaction product.

Reactions of Peroxides on Solid Surfaces

2014

This article describes the different roles that solid surfaces play in heterogeneous reactions involving peroxides, namely, (i) the solid surface interacts with the peroxide in the absence of any other substrate, (ii) the solid surface promotes the reaction activating either the peroxide or the substrate, (iii) the peroxide forms part of the solid active surface, and (iv) the substrate forms part of the active surface. The chapter covers reactions involving peroxides or discrete peroxydic transient species on solid surfaces or at solid–liquid and solid–gas interfaces, and provides general descriptions of different solid materials, details on reaction conditions, and synthetic procedures for…

Back Cover: Chemoselective, Substrate-directed Fluorination of Functionalized Cyclopentane β-Amino Acids (Chem. Asian J. 23/2016)

2016

Synthesis of 4-amino-5-fluoropyrimidines and 5-amino-4-fluoropyrazoles from a β-fluoroenolate salt

2020

A synthesis of fluorinated pyrimidines under mild conditions from amidine hydrochlorides and the recently described potassium 2-cyano-2-fluoroethenolate was developed. A broad substrate scope was tested and mostly excellent yields were obtained. The synthesis of fluorinated aminopyrazoles from the same fluorinated precursor could be demonstrated but proceeded with lower efficiency.

Enzymatic Resolution of 3-oxodicyclopentadiene on a Decagram Scale

2018

The chiral building block 3-oxodicyclopentadiene (1) can be readily resolved on a decagram scale by a short sequence consisting of (1) reduction to the corresponding endo-alcohol, (2) enzymatic oxidative resolution with a ketoreductase enzyme to give (+)-1 and the (+)-form of the endo-alcohol, and (3) reoxidation of the (+)-endo-alcohol with another ketoreductase to give (–)-1. With a selectivity factor of 310, the enantiomeric ratios of the resolved (+)-endo-alcohol and (+)-ketone are both >99:1. Both enzymatic oxidations could be performed with a at least 300:1 substrate/catalyst ratio (w/w).

An Insight into Substrate-Dependent Fluorination of some Highly Substituted Alicyclic Scaffolds

2017

The substrate-dependent fluorination of some highly-functionalized cyclopentane derivatives with multiple chiral centers has been investigated. The key steps of the stereocontrolled syntheses are the oxidative cleavage of the ring carbon–carbon double bond of readily available diexo or diendo norbornene β-amino acid derivatives followed by transformation of the resulted dialdehyde stereoisomers by reduction. Finally, substrate-directable chemodifferentiation of different types of hydroxy groups under fluorination procedures gave various densely functionalized alicyclic derivatives or heterocycles.

Photocatalytic oxidation of acetonitrile in aqueous suspension of titanium dioxide irradiated by sunlight

2004

The photocatalytic oxidation of acetonitrile (CH3CN) was carried out in aqueous suspensions of polycrystalline TiO2 P25 Degussa irradiated by sunlight. A plug flow photoreactor in a total recycle loop was used for carrying out reactivity experiments in which the concentrations of acetonitrile, of its intermediate oxidation products and of not-purgeable organic carbon (NPOC) were monitored. The influence of the presence of strong oxidant species (H2O2, S2O82−, ClO−) on the process rate was studied. The dependence of acetonitrile photo-oxidation rate on the substrate concentration and on the catalyst amount was also investigated. The photodegradation rate of substrate and NPOC followed first …

Buckwheat based substrate fermentation - possibilities for non-traditional alcoholic beverage production

2010

Effect of Mn Doping on the Optical Properties of Chalcogenide Compounds ZnS and ZnTe

2020

In this paper, the influence of the addition of Mn on the optical properties of the binary compounds ZnS and ZnTe deposited by a close-spaced vacuum sublimation method onto nonoriented glass at different substrate temperatures was considered. The spectral dependences of the transmittance T (λ), reflectance R (λ) and the absorption α (λ), as well as the bandgap for each material (Eg) were measured and calculated.

TISSUE pH-DISTRIBUTION WITHIN MALIGNANT TUMORS AS MEASURED WITH ANTIMONY MICROELECTRODES

1981

Publisher Summary Recent experiments using glass microelectrodes have demonstrated that very low tissue pH-values are prevalent in C3H mouse mammary carcinomas. The acidification of the tumor tissue is the result of an elevated lactic acid production and its inadequate removal. As a consequence of heterogeneities in tumor blood flow and in substrate supply, tissue pH values are distributed heterogeneously within solid tumors. Although glass microelectrodes with tip diameters of about 1 μm and a sensitive length of 10–50 μm have been used, the spatial resolution can be improved utilizing glass coated antimony microelectrodes the sensitive areas of that are restricted to their very tips. This…