Polarographische Untersuchungen zur Bestimmung der Stabilität von Metall-Protein-Bindungen / Polarographic Investigations for the Determination of the Stability of Metal-Protein Bonds

1989 ◽  
Vol 44 (7) ◽  
pp. 767-771 ◽  
Author(s):  
H. Reinecke ◽  
L. Dunemann ◽  
G. Schwedt
Keyword(s):  
Oxalic Acid ◽  
Chelating Agents ◽  
Binding Capacity ◽  
Soya Bean ◽  
Buffer System ◽  
Bean Flour ◽  
Model Substances ◽  
The Stability ◽  
Derivatives Of

Bonds between metals (especially copper) and a protein fraction (18,100 g/mol) of a soya bean flour extract have been investigated. The binding capacity (304 nmol Cu/mg protein) and the binding stability (K = 1,046·103 in an ammonia buffer system) were determined by polarographic investigations. Changes in the polarogram caused by spiking the protein with metal ions were compared with effects in model substances. Cysteine, ethylenediamine, oxalic acid and derivatives of benzoic acid were used as chelating agents. The effects of functional groups on the metalprotein bonds were estimated by the determination of their different binding stabilities.

Binding of calcium and lead ions to carboxystarch prepared by action of nitrogen dioxide on native starch and its 2,3-dialdehyde derivatives

1986 ◽  
Vol 51 (6) ◽  
pp. 1340-1351 ◽  
Author(s):  
Rudolf Kohn ◽  
Karol Tihlárik
Keyword(s):  
Nitrogen Dioxide ◽  
Alkaline Medium ◽  
Binding Capacity ◽  
Lead Ions ◽  
Carbonyl Groups ◽  
Weakly Alkaline ◽  
Exchange Cations ◽  
Counter Ions ◽  
The Stability ◽  
Derivatives Of

The binding of calcium and lead ions to carboxy derivatives of starch prepared by allowing nitrogen dioxide to act on native maize starch (procedure A) and on starch 2,3-dialdehyde derivatives of degrees of oxidation DO(d.a.) ≥ 0.94 (procedure B) was studied. The carboxy group content of the samples in the H+ form was 4.6 - 12.1 mmol g-1. The effect of alkaline medium on the stability of the carboxy derivatives and on their ability to bind and exchange cations was examined. The Ca2+ → 2K+ exchange was evaluated in terms of the decrease in the electrostatic free enthalpy Δ(Gel/N)KCa, determined by alkalimetric potentiometric titrations, and the binding of Pb2+ ions was evaluated in terms of the activity of the Pb2+ counter-ions determined in suspensions of Pb salts of the carboxy derivatives by means of an ion specific electrode. The IR and CD spectra revealed that the carboxystarch preparations obtained by procedure A contained, in addition to free carboxy groups, a considerable amount of carbonyl groups. During the conversion of the latter groups to the former, even in a weakly alkaline medium, the carboxy derivatives undergo an appreciable degradation and lose, to a great extent, their ability to bind and exchange cations. Procedure B, on the other hand, leads to highly selective starch and amylose carboxy derivatives, exhibiting a small amount of carbonyl groups and featuring a relative stability towards alkaline medium; their binding capacity is as high as 12 milliequivalents of cations per g of sample.

Determination of Stability Derivatives by Impulse-Response Techniques

1977 ◽  
Vol 14 (02) ◽  
pp. 265-275
Author(s):  
Carl A. Scragg
Keyword(s):  
Memory Effect ◽  
Impulse Response ◽  
Traditional Method ◽  
Equations Of Motion ◽  
Experimental Results ◽  
Regular Motion ◽  
Stability Derivatives ◽  
The Stability ◽  
Derivatives Of

This paper presents a new method of experimentally determining the stability derivatives of a ship. Using a linearized set of the equations of motion which allows for the presence of a memory effect, the response of the ship to impulsive motions is examined. This new technique is compared with the traditional method of regular-motion tests and experimental results are presented for both methods.

scholarly journals Phytochemical Molecules from the Decarboxylation of Gomphrenins in Violet Gomphrena globosa L.—Floral Infusions from Functional Food

2020 ◽  
Vol 21 (22) ◽  
pp. 8834
Author(s):  
Natalia Drobnicka ◽  
Katarzyna Sutor ◽  
Agnieszka Kumorkiewicz-Jamro ◽  
Aneta Spórna-Kucab ◽  
Michał Antonik ◽  
...  
Keyword(s):  
Citric Acid ◽  
High Resolution Mass Spectrometry ◽  
Potential Health ◽  
Gomphrena Globosa ◽  
Brewing Process ◽  
Health Promoting ◽  
The Stability ◽  
Kinetics Of ◽  
Derivatives Of

Herein, the generation of decarboxylated derivatives of gomphrenin pigments exhibiting potential health-promoting properties and the kinetics of their extraction during tea brewing from the purple flowers of Gomphrena globosa L. in aqueous and aqueous citric acid solutions were investigated. Time-dependent concentration monitoring of natural gomphrenins and their tentative identification was carried out by LC-DAD-ESI-MS/MS. The high content of acylated gomphrenins and their principal decarboxylation products, 2-, 15-, 17-decarboxy-gomphrenins, along with minor levels of their bidecarboxylated derivatives, were reported in the infusions. The identification was supported by the determination of molecular formulas of the extracted pigments by liquid chromatography coupled with high-resolution mass spectrometry (LCMS-IT-TOF). The influence of plant matrix on gomphrenins’ stability and generation of their derivatives, including the extraction kinetics, was determined by studying the concentration profiles in the primary and diluted infusions. Isolated and purified acylated gomphrenins from the same plant material were used for the preliminary determination of their decarboxylated derivatives. The acylated gomphrenins were found to be more stable than nonacylated ones. Citric acid addition had a degradative influence on natural gomphrenins mainly during the longer tea brewing process (above 15 min); however, the presence of plant matrix significantly increased the stability for betacyanins’ identification.

The pyridinium–dihydropyridine system. I. Synthesis of a series of substituted pyridinium ions and their 1,4-dihydro reduction products and a determination of their stabilities in aqueous buffers

1977 ◽  
Vol 55 (10) ◽  
pp. 1687-1695 ◽  
Author(s):  
Donald J. Norris ◽  
Ross Stewart
Keyword(s):  
Acetic Acid ◽  
Acidic Solution ◽  
Buffer System ◽  
Pyridinium Salts ◽  
Acetyl Group ◽  
Acid Catalyzed ◽  
Derivatives Of ◽  
Rate Controlling Step ◽  
Pyridinium Ions

Fourteen pyridinium salts, substituted at the 1- and 3-positions, have been prepared and their stabilities determined in aqueous acetate and tris(hydroxymethyl)aminomethane (Tris) buffers. The 1,4-dihydro derivatives of eleven of these have been prepared and characterized and their stabilities likewise determined. The pyridinium ions are stable in acidic solution but undergo either ring attack or amide or ester hydrolysis under basic conditions, whereas the dihydropyridines undergo covalent hydration in acid solution. For only four pairs of compounds and one buffer system (Tris) are there pH-ranges in which the pyridinium and dihydropyridine forms are simultaneously stable (less than 10% decomposition in 24 h). These compounds have a carbamoyl or acetyl group at the 3-position and either a methoxymethyl, acetonyl, or carbamoylmethyl group at the 1-position. The acetic acid catalyzed rates of hydration of the 1-alkyl-3-carbamoyl-1,4-dihydropyridines are correlated by σ* values with a ρ* of −2.00, consistent with protonation being the rate-controlling step.

The determination of N,N-dimethyl-4-aminoazobenzene and its reduction products by anodic voltammetry at a glassy carbon electrode

1991 ◽  
Vol 56 (6) ◽  
pp. 1210-1220
Author(s):  
Jiří Barek ◽  
Tibor J. Pastor ◽  
Jiří Zima
Keyword(s):  
Glassy Carbon ◽  
Differential Pulse ◽  
Determination Limit ◽  
Carbon Electrode ◽  
Disk Electrode ◽  
Model Substances ◽  
Pulse Voltammetry ◽  
Anodic Voltammetry ◽  
Derivatives Of

The oxidation of N,N-dimethl-4-aminoazobenzene at a rotating and stationary glassy carbon disk electrode in a medium of 40% (v/v) acetic acid was studied in the framework of a systematic study of methods for determing the efficiency of the destruction of the genotoxic derivatives of this substance; conditions were found for the determination using direct current and differential pulse voltammetry. Analogous conditions were used to determine aniline, N,N-dimethylaniline and N,N-dimethyl-p-phenylendiamine as model substances representing possible products of the reductive splitting of genotoxic azocompounds. The determination limit of the method is less than 1 . 10-5 mol l-1 and its selectivity is completely satisfactory for controlling the efficiency of the destruction.

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