Journal of the Iranian Chemical Society
Volume:3 Issue: 3, Sept 2006

During the past decade, isothermal titration calorimetry (ITC) has developed from a specialist method to a major, commercially available tool in the arsenal directed at understanding molecular interactions. At present, ITC is used to study all types of binding reactions, including protein-protein, protein-ligand, DNA-drug, DNA-protein, receptor-target, and enzyme kinetics, and it is becoming the method of choice for the determination of the thermodynamic parameters associated with the structure transformation of one molecule or non-covalent interaction of two (or more) molecules. Here, the new applications of ITC in protein folding/unfolding and misfolding, as well as its traditional application in molecular interaction/recognition are reviewed, providing an overview of what can be achieved in these fields using this method and what developments are likely to occur in the near future

The basic characteristics of the flow-through cell apparatus (USP Apparatus IV) including the assembly and open/closed configuration of the apparatus have been described. The relative advantages of the flow-through cell apparatus over other release setups have been summarized. Finally, potential applications of this setup are presented.

To determine the kinetic parameters of the reactions between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of an NH-acid, such as 2,3-di-hydroxybenzaldehyde, the reactions were monitored by UV spectrophotometry. The second order fits were automatically drawn and the values of the second order rate constants (k2) were calculated using standard equations as part of the program. The dependence of the second order rate constant (lnk2) on the reciprocal temperature was in agreement with the Arrhenius equation, in the temperature range studied, providing the relevant plots to calculate the activation energy of all reactions. Furthermore, we evaluated the effects of solvent, structure of different alkyl groups within the dialkyl acetylenedicarboxylates, and their concentration on the rates of reactions. The proposed mechanism was confirmed by experimental results and steady-state approximation. The first step (k2) of the reaction was recognized as the rate determining step on the basis of experimental data

The synthesis of 4-thiazolidinones 4a-j in a good yields from the heterocyclization reaction of 2-(benzothiazol-2-ylthio)-N’-benzylideneacetohydrazide 3a-j with SHCH2COOH in DMF in the presence of a catalytic amount of anhydrous ZnCl2 under microwave irradiation is described and compared with conventional synthesis methods. All structures of the newly synthesized compounds were elucidated by elemental analysis and spectral data. Some of the new compounds were tested against bacteria (Gram- ve and Gram+ ve) and fungi.

Mg-Cu-Zn ferrite was prepared through a wet synthetic method by a self-combustion reaction directly from a citrate precursor. The as-synthesized powders were sintered at 750 °C for only 2 h. XRD patterns and FTIR spectra confirm the formation of single phase Mg-Cu-Zn ferrite after combustion. To the best of our knowledge, this is the first time that Mg-Cu-Zn ferrite is sintered at such a low temperature. The sintering process increased the crystallinity of the solid and the domain sizes.

The equilibrium constants and the thermodynamic parameters were spectrophotometrically measured for the 1:1 adduct formation of [Co(Salen)(PPh3)]ClO4.H2O, and [Co(7,7’-Me2Salen)(PPh3)]ClO4.H2O as acceptors, with P(OR)3 (R = methyl, ethyl, and i-propyl) as donors, in acetonitrile (CH3CN) and dimethylformamide (DMF) as solvents at constant ionic strength (I = 0.1 M NaClO4), and various temperatures (t = 10-50 °C). Our results revealed the following trends: stability of the cobalt(III) Schiff base complexes toward a given phosphite donor, [Co(7,7’-Me2Salen)(PPh3)]+ < [Co(Salen)(PPh3)]+; binding of the donors (phosphites) toward a given cobalt(ΙΙΙ) Schiff base complex, P(OEt)3 > P(OMe)3 > P(O-iPr)3; influence of solvent on the stability of a given cobalt(III) Schiff base complex toward a given phosphite donor, CH3CN < DMF.

A simple and rapid method for synthesis of mesoporous zirconium silicate with high thermal stability has been developed using sodium silicate in place of costly silicon alkoxides as a silica source. The product was characterized by means of X-ray diffraction, Nitrogen sorption isotherms, FT-IR spectroscopy, transmission electron microscopy (TEM) and thermogravimetry analysis (TGA).

Bay leaves (BL) (Laurus nobilis L., Family: Lauraceae) are traditionally used orally to treat the symptoms of gastrointestinal problems, such as epigastric bloating, impaired digestion, eructation, and flatulence. In this study, lyophilized extracts (both water and ethanol) of BL were studied for their antioxidant properties. The antioxidant activity, reducing power, free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities were evaluated to determine the total antioxidant capacity of both BL extracts. Both extracts exhibited strong total antioxidant activity in linoleic acid emulsion. Concentrations of 20, 40, and 60 µg ml-1 showed 84.9, 95.7, 96.8, and 94.2, 97.7, and 98.6% inhibition of lipid peroxidation of linoleic acid emulsion, for water and ethanol extracts, respectively. On the other hand, 60 µg ml-1 of the standard antioxidants butylated hydroxyianisole (BHA), butylated hydroxytoluene (BHT), and α-tocopherol exhibited 96.6, 99.1, and 76.9% inhibition of lipid peroxidation in linoleic acid emulsion, respectively. In addition, the both BL extracts had effective reducing power, DPPH· free radical scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities at 20, 40, and 60 µg ml-1. The total amount of phenolic compounds in each BL extractwas determinedas gallic acid equivalents.

Lead oxide is used as an efficient oxidizing agent in the oxidation and condensation reaction of hydroxy ketone with diamine leading to form quinoxaline derivatives. The method is simple, cost effective and gives good yields in shorter reaction times.

New triazolo[4,3-b]pyridazinones were synthesized and evaluated for their potential in vitro cytotoxic antitumor properties. The compounds were prepared by 1,3-dipolar cycloaddition of pyridazin-3-ones with N-aryl-C-ethoxycarbonylnitrile imines, generated in situ from ethylhydrazono-α-bromoglyoxylates. The peri- and regioselectivity of the reaction were ascertained by 1H and 13C NMR spectroscopy of the cycloadducts.

A new spectrophotometric method has been developed for the assay of nadolol in pure form and in tablets. The assay procedure is based on a derivatization methodology employing 4-carboxyl-2,6-dinitrobenzene diazonium ion (CDNBD) as a diazo coupling reagent. The azo dye formed between nadolol and CDNBD absorbed visible light at the wavelength maximum of 416 nm (λmax) demonstrating a bathochromic shift from the absorption maximum of nadolol. Optimization studies established an optimal reaction time of 10 min at 60 °C. The assays were linear over 1.25-10 µg ml-1 of nadolol, and the reaction occurred by a 3:1 reagent/drug stoichiometric ratio. The method is found to be selective and has a lower detection limit of 0.29 µg ml-1. Recovery studies over three days gave mean recovery of 101.4% (RSD 3.0%). This new method has been successfully applied in the determination of nadolol and nadolol/bendroflumethiazide tablets with accuracy and precision similar to the official (USP) HPLC procedure (p > 0.05). The new procedure has the advantages of high sensitivity, lower limit of detection and could find application as an in-process quality control method for nadolol.

Photosensitized oxidation of unsymmetrically substituted 1,4-dihydropyridines using dye sensitizers methylene blue, rose bengal and tetraphenylporphyrin by taking visible light source resulted in the aromatization of dihydropyridine ring and formation of the corresponding pyridine derivatives. Comparison of the results obtained under photosensitized reaction with those obtained by direct photo-oxidation indicated a very fast and smooth reaction of these compounds and formation of pyridine derivatives using theses dyestuffs.

Lithium perchlorate-mediated double crossed aldol condensations of a variety of aromatic aldehydes with cycloalkanones at room temperature in the presence of (trimethylsilyl)diethylamine and under solvent-free conditions are described. High to excellent yields of bis(arylmethylidene)cyclohexanones and bis(arylmethylidene)cyclopentanones are achieved within a few minutes in this facile one-pot procedure.