Tast polarography of europium(III)-l-histidine complex

Study of europium(III)-l-histidine complex has been made in sodium perchlorate at μ=0.1 by tast polarography. The reduction process appears to be quasi irreversible. The apparent rate constants have been determined byGellings method¹. With the knowledge ofE ₁ ^2/r and use ofLingane's method, one complex Eu(Histd)²⁺ with the instability constant 6.77×10^?5 is reported.     

Development of a direct radioimmunoassay for serum progesterone

A direct radioimmunoassay for the measurement of progesterone in human serum is described. Progesterone 11-hemisuccinate was conjugated to tyrosine methyl ester (TME) by the mix anhydride method and then iodinated using chloramine-T. The radiochemical purity of different batches of¹²⁵I-progesterone was greater than 95% and showed 70–75% binding with excess antibody. Progesterone 11-hemisuccinate was coupled with BSA and injected to rabits. Antisera collected after three booster injections and having aK value of 1·10⁹1/M was selected for the assay. Significant reduction in binding with antibody was seen when hormone free serum was used in the assay system. Various blocking agents were tried to reduce the serum effects and none of them were found satisfactory. From a series of optimization experiments, an assay was developed without the use of blocking agents. This assay used a much higher concentration of antibody along with lower amount of serum sample (50 l). The optimized assay has a sensitivity of 0.5 nj/ml and a working range of 0.5 to 100 ng/ml. Serum samples were analyzed analysis showed good correlation between the results obtained from the present system and the DPC kit. (Y=0.93X+0.5,r=0.93, forn=25).     

Electro-kinetic transport of acetone,water and their binary mixtures

Summary Electroosmosis of acetone, water and their binary mixtures through thorium oxide (ThO₂) plug membrane has been studied and the data analysed using non-equilibrium thermodynamics. The phenomenological coefficients,L ₁₁ andL ₁₂ have been found to vary nonlinearly with composition. Excess phenomenological coefficients have therefore been evaluated and the results explained in terms of the membrane permeant and permeant-permeant interactions. The results on the measurement of electrophoretic velocity of ThO₂ particles dispersed in acetone-water mixtures also lead to the conclusion that the components of the mixture interact appreciably.

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Zusammenfassung Die Elektroosmose von Aceton, Wasser and deren binären Gemische durch eine ThO₂-Pflock-Membran wurde untersucht; die Daten wurden mit Hilfe der Nichtgleich-gewichts-Thermodynamik analysiert. Die phänomenologischen KoeffizientenL ₁₁ undL ₁₂ ändern sich hiernach nichtlinear mit der Zusammensetzung. Es wurden daher Exzess-L ₁₁-und -L ₁₂-Werte berechnet; die Ergebnisse wurden auf Grund der Membran-Permeant- und Permeant-Permeant-Wechselwirkungen diskutiert. Aus der Messung der elektrophoretischen Geschwindigkeit von ThO₂-Teilchen, die in Aceton-Wasser-Gemischen dispergiert sind, folgt, daß eine merkliche Wechselwirkung zwischen den Komponenten der Mischung vorliegt.

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With 8 figures and 1 table     

A growing string method for determining transition states: comparison to the nudged elastic band and string methods

Interpolation methods such as the nudged elastic band and string methods are widely used for calculating minimum energy pathways and transition states for chemical reactions. Both methods require an initial guess for the reaction pathway. A poorly chosen initial guess can cause slow convergence, convergence to an incorrect pathway, or even failed electronic structure force calculations along the guessed pathway. This paper presents a growing string method that can find minimum energy pathways and transition states without the requirement of an initial guess for the pathway. The growing string begins as two string fragments, one associated with the reactants and the other with the products. Each string fragment is grown separately until the fragments converge. Once the two fragments join, the full string moves toward the minimum energy pathway according to the algorithm for the string method. This paper compares the growing string method to the string method and to the nudged elastic band method using the alanine dipeptide rearrangement as an example. In this example, for which the linearly interpolated guess is far from the minimum energy pathway, the growing string method finds the saddle point with significantly fewer electronic structure force calculations than the string method or the nudged elastic band method.     

Osmotic and activity coefficients at 25°C for tetraalkylammonium bromides in deuterium oxide

Earlier work by Lindenbaum and Boyd has demonstrated the important role of hydrophobic interactions involving the water solvent in determining the osmotic coefficients and properties of aqueous solutions of the tetraalkylammonium halides. Osmotic coefficients of solutions of tetramethyl-, tetraethyl-, tetrapropyl-, and tetrabutylammonium bromides in the more highly structured solvent D₂O have now been determined by the gravimetric isopiestic method, using reference solutions of NaCl in D₂O. The data were fitted to the Rush-Johnson and Pitzer equations. Satisfactory agreement with the results for aqueous solutions at comparable concentrations indicates that the solution chemistry of these quaternary ammonium bromides is not highly dependent on the degree of structure of the pure solvents. Supplementary data for mixtures of Me₄NBr with Et₄NBr, Pr₄NBr, or Bu₄NBr in both H₂O and D₂O are consistent with this conclusion.On leave 1980–82 from Banaras Hindu University, India     

Recent applications of sample preparation techniques in food analysis

Even with the emergence of advanced techniques of separation and identification, it is rarely possible to analyse food without manipulation. The traditional techniques for sample preparation are time consuming and require large amount of reagents, which are expensive, generate considerable waste, contaminate the sample and can enrich it for analytes. The more analytical techniques have become highly developed, the more has sample clean-up become important in order to fully take advantage of them. Due to the multiplicity of food matrices, it is not possible to use one sample preparation technique, so many methods have been proposed for meeting all the requirements. The newest variations of wet digestion, solvent and sorbent extraction and membrane separation are summarised and their most recent applications to food analysis are provided.     

New Cu(II) complexes with polydentate chelating Schiff base ligands: Synthesis, structures, characterisations and biochemical activity studies

We have reported herein the synthesis of three new Cu(II) complexes of tri- and tetradentate Schiff base ligands containing N₃ or N₄ donor set along with terminal NNN⁻ or SCN⁻ ligands: [L¹Cu(NCS)]ClO₄ (1), [L²Cu(NCS)₂] (2) and [L³Cu(NNN)]ClO₄ (3) [L¹ = NC₅H₄C(CH₃)=N(CH₂)₃N=C(CH₃)C₅H₄N, L²= Me₂N–(CH₂)₃–N=C(CH₃)C₅H₄N and L³ = NC₅H₄CH=N–(CH₂)₄–N=CHC₅H₄N]. The complexes have been systematically characterised by elemental, spectroscopic and electrochemical techniques. Antimicrobial activities of the Schiff base ligands and their metal complexes have been studied using the disc diffusion method on the strains of Candida tropicalis and Bacillus megaterium. Structures of all the complexes have been unequivocally established from single crystal X-ray diffraction analyses that show the monomeric units containing a five-coordinated copper center in highly distorted square pyramidal geometry with thiocyanate or azide anion coordinated as terminal ligand. The complexes 1 and 3 crystallise in monoclinic (P2₁/c) and 2 in triclinic (P-1) space group, respectively.     

Preliminary Study on the Effect of pH on Thermal Transformation of Some Diphasic Al2O3-SiO2 Gels

Diphasic Al₂O₃-SiO₂ gels have been synthesized by hydrolyzing ethyl orthosilicate at three different pH ranges in presence of colloidal boehmite. Result shows that dominant mullitization process are sensitive to pH of the gelation process. At highly acidic pH range, solid state reaction between corundum and cristobalite occurs, and develops liquid phase for mullite nucleation. At moderately acidic pH, nucleation and crystallization are most operative for nucleation in aluminosilicate matrix. In highly basic pH region, Al-Si spinel phase develops by incorporation of Si in aluminous phase as intermediary phase. Polymorphic transformation of it may be the cause of sudden mullitization. The changes in crystallization sequence in three distinct processes may be due to variation in the nature and size of silicic acid particle formed by hydrolysis and condensation of TEOS at different pH.     

A novel nitrate-selective electrode based on precipitated nitron nitrate

Summary A nitrate-selective electrode based on precipitated nitron nitrate in an epoxy resin matrix has been prepared. The lower detection limit is 10^–5 M, the optimum pH range is 2.0–8.5, and the response time is 1 min. The electrode is selective in presence of CH₃COO^–, SO₄ ^2–, C₂O₄ ^2–, PO₄ ^3–, NO₂ ^–, Cl^– and Br^–, but I^– interferes. Results for nitrate in soil samples were in agreement with values obtained spectrophotometrically.

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Eine neue nitrat-spezifische Elektrode auf der Basis gefällten Nitronnitrats

Zusammenfassung Eine nitrat-spezifische Elektrode auf der Basis gefällten Nitronnitrats in einer Epoxyharz-Matrix wurde hergestellt. Die untere Nachweisgrenze ist 10^–5 M, das pH-Optimum liegt zwischen 2,0 und 8,5, die Reaktionszeit beträgt 1 Minute. Die Elektrode ist selektiv in Gegenwart von Acetat, Sulfat, Oxalat, Phosphat, Nitrit, Chlorid und Bromid; aber Jodid stört. Ergebnisse der Nitratbestimmung in Bodenproben stimmen mit spektrophotometrischen Resultaten überein.

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Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Self-assembled amphiphilic fluorescent probe: detecting pH-fluctuations within cancer cells and tumour tissues

Abnormal anaerobic metabolism leads to a lowering of the pH of many tumours, both within specific intracellular organelles and in the surrounding extracellular regions. Information relating to pH-fluctuations in cells and tissues could aid in the identification of neoplastic lesions and in understanding the determinants of carcinogenesis. Here we report an amphiphilic fluorescent pH probe (CS-1) that, as a result of its temporal motion, provides pH-related information in cancer cell membranes and selected intracellular organelles without the need for specific tumour targeting. Time-dependent cell imaging studies reveal that CS-1 localizes within the cancer cell-membrane about 20 min post-incubation. This is followed by migration to the lysosomes at 30 min before being taken up in the mitochondria after about 60 min. Probe CS-1 can selectively label cancer cells and 3D cancer spheroids and be readily observed using the green fluorescence channel (λ_em = 532 nm). In contrast, CS-1 only labels normal cells marginally, with relatively low Pearson''s correlation coefficients being found when co-incubated with standard intracellular organelle probes. Both in vivo and ex vivo experiments provide support for the suggestion that CS-1 acts as a fluorescent label for the periphery of tumours, an effect ascribed to proton-induced aggregation. A much lower response is seen for muscle and liver. Based on the present results, we propose that sensors such as CS-1 may have a role to play in the clinical and pathological detection of tumour tissues or serve as guiding aids for surgery.

A self-assembled amphiphilic fluorescent probe allows pH-fluctuations within cancer cells and tumour tissues to be readily detected.