Chemical reactivity of potassium permanganate and diethyl pyrocarbonate with B DNA: specific reactivity with short A-tracts

Biochemistry ◽  
1990 ◽  
Vol 29 (25) ◽  
pp. 6071-6081 ◽  
Author(s):  
James G. McCarthy ◽  
Loren Dean Williams ◽  
Alexander Rich
Keyword(s):  
Potassium Permanganate ◽  
Chemical Reactivity ◽  
Diethyl Pyrocarbonate ◽  
Specific Reactivity

scholarly journals Local Polarization, Charge Compensation, and Chemical Interactions on Ferroelectric Surfaces: a Route Toward New Nanostructures

2001 ◽  
Vol 688 ◽  
Author(s):  
Dawn A. Bonnell ◽  
Sergei V. Kalinin
Keyword(s):  
Chemical Reactivity ◽  
Charge Compensation ◽  
Switching Behavior ◽  
New Approach ◽  
Domain Specific ◽  
Ferroelectric Surfaces ◽  
Local Polarization ◽  
Enthalpy And Entropy ◽  
Specific Reactivity ◽  
Entropy Of Adsorption

AbstractThe local potential at domains on ferroelectric surfaces results from the interplay between atomic polarization and screening charge. The presence of mobile charge affects surface domain configuration, switching behavior, and surface chemical reactions. By measuring the temperature and time dependence of surface potential and piezo response with scanning probe microscopies, thermodynamic parameters associated with charge screening are determined. This is illustrated for the case of BaTiO3 (100) in air, for which the charge compensation mechanism is surface adsorption and enthalpy and entropy of adsorption are determined. The local electrostatic fields in the vicinity of the domains have a dominant effect on chemical reactivity. Photoreduction of a large variety of metals can be localized to domains with the appropriate surface charge. It has been demonstrated that proximal probe tips can be used to switch polarization direction locally. Combining the ability to ‘write’ domains of local polarization with domain specific reactivity of metals, vapors of small molecules, and organic compounds leads to a new approach to fabricating complex nanostructures.

scholarly journals The chemical reactivity of the histidine-195 residue in lactate dehydrogenase thiomethylated at the cysteine-165 residue

1981 ◽  
Vol 193 (1) ◽  
pp. 93-97 ◽  
Author(s):  
D P Bloxham
Keyword(s):  
Lactate Dehydrogenase ◽  
Rate Constants ◽  
Ternary Complex ◽  
Chemical Reactivity ◽  
Binary Complex ◽  
Histidine Residue ◽  
Nucleophilic Reaction ◽  
Carbonyl Ligands ◽  
Diethyl Pyrocarbonate ◽  
Lysine Residues

The specific thiomethylation of cysteine-165 (insertion of a methylthio group, CH3-S-) in pig heart lactate dehydrogenase results in a decreased affinity for carbonyl ligands that is accompanied by a decreased nucleophilic reaction of histidine-195 with diethyl pyrocarbonate. The rate constants at 10 degrees C for the modification of native and thiomethylated lactate dehydrogenase by diethyl pyrocarbonate were 173 M-1 . s-1 and 8.7 M-1 . s-1 respectively. It was found that 0.86 +/- 0.07 histidine residue per subunit reacted with diethyl pyrocarbonate in thiomethylated lactate dehydrogenase. This reaction was not affected in the enzyme-NADH binary complex, but was diminished in the enzyme-NADH-oxamate ternary complex. In the enzyme-NADH complex the reaction of diethyl pyrocarbonate was controlled by two groups with pKa 6.8 and 7.9. The decreased reactivity of histidine-195 was selective in thiomethylated lactate dehydrogenase, since the reactivity of arginine and/or lysine residues was enhanced.

Spatially Resolved Photoelectron Spectroscopy: Recent Progress and Future Plans

1990 ◽  
Vol 48 (2) ◽  
pp. 388-389
Author(s):  
A. M. Bradshaw
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Reactivity ◽  
Target Material ◽  
Orbital Energy ◽  
Light Sources ◽  
Analytical Technique ◽  
Hartree Fock ◽  
Spatially Resolved ◽  
Koopmans Theorem ◽  
Surface Analytical Technique

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).

Cluster analysis for large data sets: applications to individual aerosol particles from the mid-pacific

1992 ◽  
Vol 50 (2) ◽  
pp. 1488-1489
Author(s):  
Thomas W. Shattuck ◽  
James R. Anderson ◽  
Neil W. Tindale ◽  
Peter R. Buseck
Keyword(s):  
Cluster Analysis ◽  
Chemical Reactivity ◽  
Large Data ◽  
Large Data Sets ◽  
Particle Analysis ◽  
Data Sets ◽  
Halogen Chemistry ◽  
Complete Study ◽  
Components Analysis ◽  
Automated Scanning

Individual particle analysis involves the study of tens of thousands of particles using automated scanning electron microscopy and elemental analysis by energy-dispersive, x-ray emission spectroscopy (EDS). EDS produces large data sets that must be analyzed using multi-variate statistical techniques. A complete study uses cluster analysis, discriminant analysis, and factor or principal components analysis (PCA). The three techniques are used in the study of particles sampled during the FeLine cruise to the mid-Pacific ocean in the summer of 1990. The mid-Pacific aerosol provides information on long range particle transport, iron deposition, sea salt ageing, and halogen chemistry.Aerosol particle data sets suffer from a number of difficulties for pattern recognition using cluster analysis. There is a great disparity in the number of observations per cluster and the range of the variables in each cluster. The variables are not normally distributed, they are subject to considerable experimental error, and many values are zero, because of finite detection limits. Many of the clusters show considerable overlap, because of natural variability, agglomeration, and chemical reactivity.

A potassium permanganate fixative for membranes in sections

1990 ◽  
Vol 48 (3) ◽  
pp. 722-723
Author(s):  
Jindan Song
Keyword(s):  
Potassium Permanganate ◽  
Cultured Cells ◽  
Calf Serum ◽  
Trisodium Citrate ◽  
Membrane System ◽  
Adenocarcinoma Cell Line ◽  
Mouse Embryo Fibroblast ◽  
African Green Monkey Kidney ◽  
Adenocarcinoma Cell ◽  
Green Monkey

Potassium permanganate has been used as a fixative for the botanical specimen and membrane system in thin section by Glauert (1975). A new potassium permanganate fixative ( Trisodium citrate 60mM, Potassium chloride 25mM, Magnesium chloride 35mM, and Potassium permanganate 125mM ) for localizing membranous system in whole_mount cultured cells with standard trasmission electron microscopy and phase_contrast microscopy has been developed). Here, we report that using this new potassium permanganate fixative for membranous system in sections.Cultured cells, CV_1 (African green monkey kidney epithelial cells), Balb/c 3T3 ( Mouse embryo fibroblast ) and MCF_7 (Human adenocarcinoma cell line) were used for this study. All cells were grown on 35mm plastic dishes in DME medium containing 5% calf serum at 37 c with 100% humidity and 5% CO2. Using the potassium permanganate fixative to fix the cells for about 7 minutes. After fixation, the cells were dehydrated in a graded series of ethanol.

Etching of LLDPE and LLDPE/HDPE blends

1996 ◽  
Vol 54 ◽  
pp. 200-201
Author(s):  
M. S. Bischel ◽  
J. M. Schultz
Keyword(s):  
Potassium Permanganate ◽  
Morphological Features ◽  
Narrow Fraction ◽  
Potassium Permanganate Solution ◽  
Commercial Applications ◽  
Microscopy Techniques

Despite its rapidly growing use in commercial applications, the morphology of LLDPE and its blends has not been thoroughly studied by microscopy techniques. As part of a study to examine the morphology of a LLDPE narrow fraction and its blends with HDPE via SEM, TEM and AFM, an appropriate etchant is required. However, no satisfactory recipes could be found in the literature. Mirabella used n-heptane, a solvent for LLDPE, as an etchant to reveal certain morphological features in the SEM, including faint banding in spherulites. A 1992 paper by Bassett included a TEM micrograph of an axialite of LLDPE, etched in a potassium permanganate solution, but no details were given.Attempts to use n-heptane, at 60°C, as an etchant were unsuccessful: depending upon thickness, samples swelled and increased in diameter by 5-10% or more within 15 minutes. Attempts to use the standard 3.5% potassium permanganate solution for HDPE were also unsuccessful: the LLDPE was severely overetched. Weaker solutions were also too severe.

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