Electrochemical methods for quantification and characterization of metallothioneins induced in Mytilus galloprovincialis

The quantification of the purified metallothionein (MT) component, isolated from the digestive gland of cadmium-exposed Mytilus galloprovincialis, is described based on the analysis of Cd(II) and SH-groups content, applying electrochemical methods. Advantages and disadvantages of the Brdicka procedure for the determination of the MT content is discussed. The saturation of binding positions of purified MT with Cd(2+) ions can be directly followed voltammetrically. Irrespective of the MT concentration, the saturation with Cd(2+) of in vivo induced mussel MT is achieved at a molar ratio of 5. Cd(2+) ions are rapidly displaced from the Cd-Th complex after the addition of Pb(2+) ions, which indicates the kinetically labile type of the complex.     

2-[3-(Trifluoromethyl)phenyl]furo[3,2-b]pyrroles: synthesis and reactions

The synthesis and reactions of methyl 2-[3-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrole-5-carboxylate (1a) are described. Upon reaction with methyl iodide, benzyl chloride, or acetic anhydride, this compound gave N-substituted products 1b-d. By hydrolysis of compounds 1a-c, the corresponding acids 2a-c were formed, or by reaction with hydrazine-hydrate, the corresponding carbohydrazides 3a-c were formed. By heating 2-[3-(trifluoromethyl)phenly]-4H-furo[3,2-b]pyrrole-5-carboxylic acid (2a) in acetic anhydride, 4-acetyl-2-[3-(trifluoromethyl)phenyl]furo[3,2-b]pyrrole (4) was formed. By hydrolysis of 4, 2-[3-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrole (5a) was formed, and reactions with methyl iodide or benzyl chloride gave N-substituted products 5b-c. The reaction of 4 with dimethyl butynedioate gave substituted benzo[b]furan 6. Compound 3a reacted with triethyl orthoesters giving 7a-c, which afforded with phosphorus (V) sulphide the corresponding thiones 8a-c. The thiones 8a-c reacted with hydrazine hydrate to form hydrazine derivatives 9a-c. The reaction of triethyl orthoformiate with compounds 9a-c led to furo[2′,3′: 4,5]pyrrolo[1,2-d][1,2,4]triazolo[3,4-f][1,2,4]triazines 10a-c. Hydrazones 11a-c were formed from 3a-c and 5-[3-(trifluoromethyl)phenyl]furan-2-carboxaldehyde. The effect of microwave irradiation on some condensation reactions was compared with “classical” conditions. The results showed that microwave irradiation shortens the reaction time while affording comparable yields.     

β-Tricarbonyl compounds. I. 2,4-Disubstituted 1,3-cyclopentanediones

Summary Stable enolic isomers of 2-aroyl-4-aracyl-1,3-cyclopentanediones such as3 and4 were prepared by condensation of aryl methyl ketones and diethyl maleate using an excess of sodium ethoxide (Aryl=C₆H₅, 4-C₆H₄CH₃, 4-C₆H₄Br and 4-C₆H₄Cl).

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-Tricarbonyl Verbindungen. I. 2,4-Disubstituierte 1,3-Cyclopentandione

Zusammenfassung Stabile Enol-Isomere von 2-Aroyl-4-aracyl-1,3-cyclopentandionen wie3 und4 wurden durch Kondensation von Arylmethylketonen und Diethylmaleat mit einem Überschuß von Natriumethoxid dargestellt (Aryl=C₆H₅, 4-C₆H₄CH₃, 4-C₆H₄Br und 4-C₆H₄Cl).

     

Synthesis of 5-Methyluridine and Its 5′-Mercapto-, 2-Amino-, and 4′,5′-Unsaturated Analogues

The stereospecific cis-hydroxylation of 1-(2,3-dideoxy-β-D -glyceropent-2-enofuranosyl)thymine (1) into 1-β-D -ribofuranosylthymine (2) by osmium tetroxide is described. Treatment of 2′,3′-O, O-isopropylidene-5-methyl-2,5′-anhydrouridine (8) with hydrogen sulfide or methanolic ammonia afforded 5′-deoxy-2′,3′-O, O-isopropylidene-5′-mercapto-5-methyluridine (9) and 2′,3′-O, O-isopropylidene-5-methyl-isocytidine (10) , respectively. The action of ethanolic potassium hydroxide on 5′-deoxy-5′-iodo-2′,3′-O, O-isopropylidene-5-methyluridine (7) gave rise to the corresponding 1-(5-deoxy-β-D -erythropent-4-enofuranosyl)5-methyluracil (13) and 2-O-ethyl-5-methyluridine (14) . The hydrogenation of 2 and its 2′,3′-O, O-isopropylidene derivative 4 over 5% Rh/Al₂O₃ as catalyst generated diastereoisomers of the corresponding 5-methyl-5,6-dihydrouridine ( 17 and 18 ).     

Anodic Sampling and TLC Identification of Dental Alloys

JPC – Journal of Planar Chromatography – Modern TLC - Knowledge of the composition of an incorporated alloy is a precondition for avoiding polymetallism in subsequent prosthetic...     

A theoretical study of the vibronic structure in the electronic spectrum of HNO+

The results of an ab initio study of the vibronic and rotational structure in the ²Π state of HNO⁺ are presented. It is shown that the absorption spectrum at 7200 Å observed by Herzberg could be caused by the transition from the ground to the first excited electronic state of HNO⁺     

On free semilattice-ordered semigroups satisfying x n =x

Let B(k,0,n) denote the group with k generators which is free in the group variety defined by the identity x ⁿ =1. Let B _slo (k,1,n) denote the semilattice-ordered semigroup with k generators which is free in the semilattice-ordered semigroup variety defined by the identity x ⁿ =x. We prove a generalization of the Green-Rees theorem: B _slo (k,1,n) is finite for all k≥1 if and only if B(k,0,n−1) is finite for all k≥1. We find a formula for card(B _slo (1,1,n)). We construct B _slo (k,1,n) for some concrete values of k and n.     

Torsional potential and strain energy distribution in an extended chain under stress

Torsional potentialV() for the single bond transformation in an extended hexadecane, subjected to elongation, has been determined by molecular mechanics calculations. The stored elastic energy significantly modifies the potentialV(), the conformational energies and the barriers of transition. Apart from the soft torsional coordinate, elastic energy is also dissipated considerably by bond stretching and angle bending. Maximal variations of the valence coordinates occur in the vicinity of the torsional defect and dampen along the chain. At higher elongation, the gauche minimum on the potentialV() disappears and the calculations predict the abrupt gauche to trans transition. The energetics of torsion of a deformed chain are compared with the experimental data on the hydrodynamic extension of polymers in dilute solution by elongational flow. The calculations also provide details of a single bond transformation mechanism at conformational interconversions in a long chain, proposed by Helfand.     

Some possibilities of an analysis of complex samples by a mass spectrometry with a sample pretreatment by an offline coupled preparative capillary isotachophoresis

This work deals with an analysis of biologically important compounds in complex matrices using preparative isotachophoresis (pITP) in column coupling configuration as a sample pretreatment technique followed by a direct infusion mass spectrometry with nano‐electrospray ionization (DI‐nESI‐MS). Busereline was chosen as a model analyte, and urine was chosen as an example of complex matrix. In pITP experiments, sodium cation (10 mmol/L concentration) was used as a leading ion and β‐alanine as terminating ion (20 mmol/L concentration). The fractions, obtained by pITP pre‐separation with the assistance of the mixture of discrete spacers, were finally analyzed by DI‐nESI‐MS. It was shown that pITP performed before DI‐nESI‐MS analysis can significantly simplify complex matrix, and, due to its concentration power, pITP can consequently decrease the concentration limit of detection. The concentration of buserelin in the urine samples analyzed by pITP‐DI‐nESI‐MS was 10 μg/L (reflecting at a 8.10^?9 mol/L concentration) in our work but from the ion intensities obtained in MS as well as MS/MS analyses, it is clear that this concentration level could be several orders of magnitude lower for reliable detection and identification of buserelin in urine analyzed using pITP with DI‐nESI‐MS detection.