DNA Aptamers are Functional Molecular Recognition Sensors in Protic Ionic Liquids

The function and structural changes of an AMP molecular aptamer beacon and its molecular recognition capacity for its target, adenosine monophosphate (AMP), was systematically explored in solution with a protic ionic liquid, ethylammonium nitrate (EAN). It could be proven that up to 2 M of EAN in TBS buffer, the AMP molecular aptamer beacon was still capable of recognizing AMP while also maintaining its specificity. The specificity was proven by using the guanosine monophosphate (GMP) as target; GMP is structurally similar to AMP but was not recognized by the aptamer. We also found that in highly concentrated EAN solutions the overall amount of double stranded DNA formed, as well as its respective thermal stability, diminished gradually, but surprisingly the hybridization rate (k_h) of single stranded DNA was significantly accelerated in the presence of EAN. The latter may have important implications in DNA technology for the design of biosensing and DNA‐based nanodevices in nonconventional solvents, such as ionic liquids.     

Poly(dialkoxyethyl itaconates)

The oxidative and non-oxidative degradation of poly(di-methoxy-), poly(di-ethoxy-), poly(di-iso-propoxy-) and poly(di-n-butoxyethyl itaconate) were investigated by thermogravimetry. Characteristic degradation temperatures and apparent activation energies of degradation were determined for the non-oxidative degradation of all the investigated polymers. It was not possible to determine these characteristics in the presence of oxygen as the degradation was accompanied by a secondary exothermic reaction. Based on examination of the monomers, it is supposed that the exothermic reaction is a repolymerisation of the monomers released during the earlier stages of polymer degradation.     

Topologies of some new sequence spaces, their duals, and the graphical representations of neighborhoods

Many interesting topologies arise in the theory of FK spaces. Here we present some new results on the topologies of certain FK spaces and the determinations of their dual spaces. We also apply our software package for visualization and animations in mathematics and its extensions to the representation of neighborhoods in various topologies.     

Influence of high-frequency modulation on Mössbauer resonance: Experiments with67Zn

Hyperfine Interactions - Temporal aspects related to the Mössbauer resonance are reviewed, in particular time-dependent transient effects produced by high-frequency modulation of the...     

Evaluation of the Lipophilicity of Some 1-Arylpiperazines by Planar Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - The lipophilic character of some biologically active 1-arylpiperazines has been studied. A reversed-phase planar chromatographic...     

Determination of Carvedilol and its Impurities in Pharmaceuticals

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed for separation of carvedilol and its impurities from Karvileks tablets. The best separation was achieved on a 100 mm × 4.6 mm, 5 µm particle size, Chromolit RP 8e column. Use of acetonitrile-water, 45:55 (v/v), adjusted to pH 2.5 with formic acid, as mobile phase at a flow rate of 0.5 mL min^?1 enabled acceptable resolution of carvedilol, in large excess, from possible impurities, in a short elution time. UV detection was performed at 280 nm. Linearity, accuracy, precision, selectivity, and robustness were validated and found to be satisfactory. Overall, the proposed method was found to be highly sensitive, suitable, and accurate for quantitative determination of carvedilol and its impurities in dosage forms and in raw materials.     

Formation of positive cluster ions Li(n) Br (n = 2-7) and ionization energies studied by thermal ionization mass spectrometry

Clusters of the type Li(n)X (X = halides) can be considered as potential building blocks of cluster-assembly materials. In this work, Li(n)Br (n = 2-7) clusters were obtained by a thermal ionization source of modified design and selected by a magnetic sector mass spectrometer. Positive ions of the Li(n)Br (n = 4-7) cluster were detected for the first time. The order of ion intensities was Li(2)Br(+) > Li(4)Br(+) > Li(5)Br(+) > Li(6)Br(+) > Li(3)Br(+). The ionization energies (IEs) were measured and found to be 3.95 ± 0.20 eV for Li(2)Br, 3.92 ± 0.20 eV for Li(3)Br, 3.93 ± 0.20 eV for Li(4)Br, 4.08 ± 0.20 eV for Li(5)Br, 4.14 ± 0.20 eV for Li(6)Br and 4.19 ± 0.20 eV for Li(7)Br. All of these clusters have a much lower ionization potential than that of the lithium atom, so they belong to the superalkali class. The IEs of Li(n)Br (n = 2-4) are slightly lower than those in the corresponding small Li(n) or Li(n)H clusters, whereas the IEs of Li(n)Br are very similar to those of Li(n) or Li(n)H for n = 5 and 6. The thermal ionization source of modified design is an important means for simultaneously obtaining and measuring the IEs of Li(n)Br (n = 2-7) clusters (because their ions are hermodynamically stable with respect to the loss of lithium atoms in the gas phase) and increasingly contributes toward the development of clusters for practical applications.     

Synthesis, spectroscopic and redox properties of the copper(II) complexes of N-(di-methylphenyl)-3,5-Bu2t-salicylaldimines

A series of copper(II) complexes (CuL2x) with new N-di-methylphenyl-3,5-Bu2t-salicylaldimines (L(x)H) were prepared and characterized by IR, UV/vis, 1H NMR, ESR, cyclic voltammetry techniques and chemical oxidation. L(x)H ligands have been found selectively bind to a Cu(II), rather than to Ni(II), Co(II), Mn(II), VO(IV), Zn(II) and Cd(II). ESR examinations of the CuL2x complexes demonstrate that they exist in magnetically diluted mononuclear or coupled triplet-state structures in the solid. The temperature dependent (113-283 K) intensity of the powder ESR spectra for some CuL2x is characteristic of ferromagnetic coupling (J > 0). The reduction potentials of CuL2x in DMSO are sensitive to aniline moieties. Chemical oxidation of CuL2x with (NH4)2[Ce(NO3)6] in CHCl3 and MeCN solutions at 300 K affords gradually disappearance of their ESR signals and dramatic changes in the electronic spectra as well as the appearance of new maximum bands at 530-672 (CHCl3) and 670-700 nm (MeCN), suggesting generation of Cu(II)-phenoxyl radical species.