Use of 2-aminopurine as a fluorescent tool for characterizing antibiotic recognition of the bacterial rRNA A-site

Spectroscopic and calorimetric techniques have been employed to characterize the impact on an Escherichia coli rRNA A-site model oligonucleotide of incorporating the fluorescent base analog 2-aminopurine into the 1492- or the 1493-position, as well as the energetics and dynamics associated with recognition of this A-site model oligomer by aminoglycoside antibiotics. The results of these studies indicate that incorporation of 2AP into either the 1492- or the 1493-position does not perturb the structure or stability of the host RNA or its aminoglycoside binding affinity. In addition, the results also highlight drug-induced reduction in the mobilities of the bases at both the 1492- and 1493-positions as a potentially key determinant of bactericidal potency.     

Chromatographic determination of itopride hydrochloride in the presence of its degradation products

Two sensitive and reproducible methods are described for the quantitative determination of itopride hydrochloride (IH) in the presence of its degradation products. The first method is based on HPLC separation on a reversed phase Kromasil column [C18 (5-microm, 25 cm x 4.6 mm, ID)] at ambient temperature using a mobile phase consisting of methanol and water (70:30, v/v) adjusted to pH 4.0 with orthophosphoric acid with UV detection at 258 nm. The flow rate was 1.0 mL per min with an average operating pressure of 180 kg/cm2. The second method is based on HPTLC separation on silica gel 60 F254 using toluene:methanol:chloroform:10% ammonia (5.0:3.0:6.0:0.1, v/v/v/v) as mobile phase at 270 nm. The analysis of variance (ANOVA) and Student's t-test were applied to correlate the results of IH determination in dosage form by means of HPLC and HPTLC methods. The drug was subjected to acid and alkali hydrolysis, oxidation, dry heat, wet heat treatment, UV, and photodegradation. The proposed HPLC method was utilized to investigate the kinetics of the acidic, alkaline, and oxidative degradation processes at different temperatures and the apparent pseudo-first-order rate constant, half-life, and activation energy were calculated. In addition the pH-rate profile of degradation of IH in constant ionic strength buffer solutions in the pH range 2-11 was studied.     

Übergangsmetall-substituierte phosphane,arsane und stibane: XXXVI. Diastereomere dreikernkomplexe mit verbrückenden dimethylarsino-, dimethylstibino- oder dimethylbismutino-einheiten

Interaction of the chiral organometallic Lewis bases Cp(CO)(Me₃P)Fe—EMe₂ (E = As, Sb, Bi) (1a–1c) with the norbornadiene metal complex (C₇H₈)Mo(CO)₄ yields the first examples of trinuclear complexes [Cp(CO)(Me₃P)Fe—EMe₂]₂Mo(CO)₄ (2a–2c), bearing two chiral metal atoms separated by a E—Mo—E-linkage. 2a–2c are generated as a mixture of two diastereomers (RS/SR, RR/SS), which gives rise to a resonance doubling in their ¹H and ³¹P NMR spectra. This phenomenon is not observed for the achiral, in part sterically more crowded derivatives [Cp(CO)₂Fe—SbMe₂]₂Mo(CO)₄ (4) and [Cp(CO)₂(Me₃P)Mo—EMe₂]₂Mo(CO)₄ (E = As, Sb (6a, 6b)), which excludes the existence of conformers resulting from restricted rotation about the FeE or MoE bond in the case of 2a–2c.     

Phase equilibria and thermodynamics of coexisting phases in rare-earth element-iron-oxygen systems. I. The cerium-iron-oxygen system

In the present work it is shown that in the CeFeO system only one ternary compound with a perovskite structure, the orthoferrite CeFeO₃, is formed. We define the crystallographic properties of cerium ferroperovskite more accurately. The thermodynamics of its oxidation and reduction over a temperature range of 900–1200°C are studied using the emf method with a solid electrolyte.It is shown that the free energy of cerium orthoferrite formation from the oxides according to the reaction $\text{1}\text{2}\text{Ce}{}_2\text{O}{}_3\text{+}\text{1}\text{2}\text{Fe}{}_2\text{O}{}_3\text{=}\text{CeFeO}{}_3$, derived from data on the equilibrium oxidation of CeFeO₃, differs very little from the value of ΔG°, calculated from the magnitude of the equilibrium pressure of oxygen over the orthoferrite and reduction products coexisting with it.Phase equilibria and the thermodynamics of coexisting phases in the CeFeO system have been investigated. Equilibrium diagrams are constructed which define the character of the changes taking place in the CeFeO system during changes in partial oxygen pressure, temperature, and composition of the initial oxide mixture. Thus, we have equilibrium diagrams of the type P_O2 = f(composition) with T = constant; with one composition parameter fixed; and T = f(composition) with P_O2 = constant.     

Some generalizations of Lindelöf and paracompact spaces

In this paper notions ofm-Lindelöf, meta-m-Lindelöf, para-m-Lindelöf andm-closure preserving property are defined, wherem is any infinite cardinal. The main results are the following:

1. A topological space ism-Lindelöf if and only if it is meta-m-Lindelöf and it ism-Lindelöf in the sense of complete accumulation point.
2. A regular topological space is paracompact if and only if it is para-m-Lindelöf and it hasm-closure preserving property for somem.

     

Thermogravimetric studies of dipyridinium complexes of cerium(IV), thorium(IV) and zirconium(IV)

The TG curves of dipyridinium complexes of Ce(IV), Th(IV) and Zr(IV) have been reported. The mode of decomposition of the cerium and thorium complexes is broadly comparable but the decomposition of Zr complex shows some variation.     

Gas‐phase pyrolysis in organic synthesis. Part 3: Novel cyclization of 2‐arylhydrazonopropanals into cinnolines1

3‐oxo‐3‐aryl‐2‐arylhydrazonopropanals (1) have been converted under thermal gas‐phase conditions cleanly into cinnolines (2) . A plausible mechanism is suggested to account for this transformation based on the kinetics and products of reaction. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 402–406, 2001