[en] Polarographic study of complexation of cadmium with a Schiff base derived from vanillin and trisbuffer was carried out in DMF-water media of three different compositions (viz. 0%, 30% and 50% v/v of DMF). 1:1, 1:2 and 1:3 complex species are present in the solution. Overall stability constants were calculated using DeFord and Hume treatment at three different temperatures (viz. 30⁰, 40⁰ and 50⁰). Free energy change ΔG, enthalpy change ΔH and entropy change ΔS were also calculated for all the three media. A new, methamatical model, recently developed by Mihailov, to calculate stability constants from nbar values was used to check the data obtained from DeFord and Hume method. (author)

[en] Three Schiff base complexes of Cd²⁺ have been investigated polarographically in 60% menthanol-water medium at 26⁰C. The Schiff bases used are salicyladehyde tris buffer (ST), benzaldehydetris buffer (BT) and vanillin tris buffer (VT). Cd-ST and Cd-VT complexes produce reversible reduction wave at dme, while Cd-BT gives a quasi reversible wave. Stability constants of the complexes have been determined and the standard overall electrode reaction rate constant (ksub(e)sup(o)) B of the Cd-BT complex is determined by three different methods. The log β values of complexes are : Cd-ST, 2.72; Cd-VT, 4.90; and Cd-BT, 4.41. (author)

[en] Polarographic behaviour of Cd²⁺ with a schiff base salicylaldehyde trisbuffer has been studied in DMF water media of three different compositions (viz. 0%, 30% and 50% v/v of DMF). Stability constant, free energy change ΔG, enthalpy change ΔH and entropy change ΔS of the systems are calculated for all the three media at three different temperatures (viz. 30deg, 40deg and 50deg C). A relation of halfwave potential of the system with the dielectric constant of the medium has also been verified. (auth.)

[en] The complexation of Cd²⁺ with the Schiff base bis-p-methoxy benzylimino ethene, has been investigated polarographically in dimethyl formanide water mixtures. The metal to ligand ratio of the complex is found 1 : 1 in the mixed solvent used. Stability constants are calculated at three different temperatures and thermodynamic functions ΔG, ΔH and ΔS for the complexation have been reported. A relationship between pH and Esub(.5) of the system is shown by empirical equation similar to the polarographic wave equation. Ligand proton stability constant is evaluated by utilizing this equation and verified potentiometrically. The effect of solvent on complex composition is discussed. (author)

[en] The authors have shown previously that the activity of the pyruvate dehydrogenase complex (PDC) increased several fold during differentiation of 3T3-L1 preadipocytes into adipocytes. The increase in total activity correlated with coordinated increases in the relative rates of synthesis (RRS) of α and β subunits of the pyruvate dehydrogenase component. They now report investigations of the changes in the activity of E₃, another component of PDC, in 3T3-L1 cells during differentiation initiated by exposing cells to insulin, dexamethasone and 1-methyl-3-isobutylxanthine for 48 h followed by continued exposure to insulin alone. The specific activity (SA) of E₃ increased 3 to 4-fold during the differentiation. The amount of immunoprecipitable E₃ protein similarly increased in the differentiated cells. Immunotitrations of E₃ indicated that the SA of E₃ remained the same in both cell types. Pulse labeling of cells with ³⁵S-methionine revealed a 3.5-fold increase in the RRS of E₃ in adipocytes compared to preadipocytes. The apparent degradation rates of E₃ were not significantly different in the two cells types. E₃ mRNA content, measured using an E₃ cDNA clone, was also increased during the differentiation. The increase in the RRS of E₃ is the primary determinant for increased enzyme protein in adipocytes

[en] A cDNA clone (1,423 base pairs) comprising the entire coding region of the precursor form of the α subunit of pyruvate dehydrogenase (E₁α) has been isolated from a human liver cDNA library in phage λgt11. The first 29 amino acids deduced from the open reading frame correspond to a typical mitochondrial targeting leader sequence. The remaining 361 amino acids, starting at the N terminus with phenylalanine, represent the mature mitochondrial E₁α peptide. The cDNA has 43 base pairs in the 5' untranslated region and 210 base pairs in the 3' untranslated region, including a polyadenylylation signal and a short poly(A) tract. The nucleotide sequence of human liver E₁α cDNA was confirmed by the nucleotide sequences of three overlapping fragments generated from human liver and fibroblast RNA by reverse transcription and DNA amplification by the polymerase chain reaction. This consensus nucleotide sequence of human liver E₁α cDNA resolves existing discrepancies among three previously reported human E₁α cDNAs and provides the unambiguous reference sequence needed for the characterization of genetic mutations in pyruvate dehydrogenase-deficient patients

[en] cDNA clones comprising the entire coding region for human dihydrolipoamide dehydrogenase have been isolated from a human liver cDNA library. The cDNA sequence of the largest clone consisted of 2082 base pairs and contained a 1527-base open reading frame that encodes a precursor dihydrolipoamide dehydrogenase of 509 amino acid residues. The first 35-amino acid residues of the open reading frame probably correspond to a typical mitochondrial import leader sequence. The predicted amino acid sequence of the mature protein, starting at the residue number 36 of the open reading frame, is almost identical (>98% homology) with the known partial amino acid sequence of the pig heart dihydrolipoamide dehydrogenase. The cDNA clone also contains a 3' untranslated region of 505 bases with an unusual polyadenylylation signal (TATAAA) and a short poly(A) track. By blot-hybridization analysis with the cDNA as probe, two mRNAs, 2.2 and 2.4 kilobases in size, have been detected in human tissues and fibroblasts, whereas only one mRNA (2.4 kilobases) was detected in rat tissues