Hydrogen Bonds at Silica – Polyvinylpyrrolidone – Water Interfaces

The effect of the adsorption of polyvinylpyrrolidone on the surface of highly dispersed silica on the state of interfacial water was studied by ¹H NMR spectroscopy and thermally stimulated depolarization with freezing out of the bulk water.     

SPIROPHOSPHORANES – STRUCTURE REACTIVITY

Abstract

The first part of this article will deal with the reactions of spirophosphoranes with a P[sbnd]H bond. These compounds contain two five-membered rings and have four oxygen atoms, or three oxygen atoms and one nitrogen atom, or two oxygen and two nitrogen atoms directly bonded to the phosphorus atom, which in all cases bears an hydrogen atom (Scheme 1). The most remarkable property of these compounds is undoubtedly their ability to give rise to a tautomeric equilibrium between the tri- and penta-coordinated structures P_III→P_V.     

Lotus-Effect® – surfaces

Surfaces are often characterized with phrases like “easy to clean”, “dirt repellent”, “dirt resistant”, “self cleaning” or “ Lotus -Effect^®”. Every one of those phrases is used to describe a behavior of surfaces - similar to each other but still different. This article is providing the definition of the Lotus -Effect^®, techniques to manufacture self cleaning surfaces and methods to characterize them as well. How to generate a self cleaning surface depends on the substrate and the use later on. It can be as easy as a spray on but on the other hand as complicated as a three step process. Self cleaning surfaces are defined by four parameters - contact angle, roll-off angle, hystereses and C.I.E-Lab Δ-L value.     

Fiber-optic biosensors – an overview

This article reviews progress and developments during the past five years in the field of optical fiber biosensors. Because of the expense and time constraints associated with modern laboratory analysis, there is a growing need for real-time, low-cost technology that can be used industrially, environmentally, and clinically, and to monitor food processing. Miniaturization, integrated systems, and multianalyte determination have become key aspects of sensor development and efforts in this direction will also be discussed, with some pointers to likely directions of future research in the area. The review will provide information about the analytical characteristics and applications of fiber-optic biosensors classified depending on the biorecognition element employed - enzymes, whole cells, antibodies, nucleic acids, and biomimetic polymers.     

Antiviral Agents – Benzazine Derivatives

Chemistry of Heterocyclic Compounds - The review outlines the results of studies of the antiviral activity of quinoline, quinoxaline, and quinazoline derivatives published over the past 5 years....     

Synthesis and characterization of 10-hydroxycamptothecin – sebacate – layered double hydroxide nanocomposites

10-Hydroxycamptothecin (HCPT) as a hydrophobic anticancer drug brings many challenges in the clinical applications due to its poor water solubility and the presence of a chemically unstable lactone ring. In this work, the nanocomposites of HCPT intercalated layered double hydroxide (LDH) were prepared by a secondary intercalation method, and the encapsulated HCPT could keep the biologically active lactone form. A Zn–Al–NO₃ LDH was pillared with sebacate anions by a co-precipitation method in an aqueous medium, and then HCPT was intercalated into the LDH's gallery via hydrophobic interaction in an ethanol medium. The parallel alkyl chains of perpendicularly arranged sebacate anions in the LDH gallery provide a hydrophobic space for the drug intercalation. The in vitro release kinetics of HCPT from the nanocomposites could be fitted with the pseudo-second-order kinetic model, and the diffusion of HCPT through the LDH particles played an important role in controlling the drug release. The nanocomposites can be considered as a potential drug delivery system.     

SeqFold – fully automated fold recognition and modeling software – evaluation and application

SeqFold is a fold recognition program based on sequence-similarity detection aided by predicted secondary structure [1–3]. Critical validation and evaluation of SeqFold fold recognition performance based on the latest Critical Assessment of protein Structure Prediction (CASP2) targets has been performed. It has revealed that four out of seven CASP2 threading targets were assigned a correct fold using this method. SeqFold has also been applied to the problem of fold recognition for leptin. Mice with a defective leptin gene are extremely obese and diabetic. Leptin does not exhibit clear sequence homology to any protein with known structure. SeqFold predicts that leptin belongs to the class of short-chain four-helical cytokines. The structure of leptin, which has recently been solved by X-ray crystallography, reveals that leptin is a long-chain four-helical cytokine. The 3D model of leptin demonstrates that SeqFold alignment-based homology modeling captures essential features of the leptin structure. Received: 25 May 1998 / Accepted: 4 August 1998 / Published online: 2 November 1998     

SPME – Quo vadis?

Solid phase microextraction (SPME) has experienced rapid development and growth in number of application areas since its inception over 20 years ago. It has had a major impact on sampling and sample preparation practices in chemical analysis, bioanalysis, food and environmental sciences. A significant impact is expected in clinical analysis as well as pharmaceutical and medical sciences in the near future. In this review, recent developments of SPME and related technologies are discussed including an in-vial standard gas system for calibration of SPME in high throughput mode; a thin film geometry with high extraction efficiency SPME for gas chromatography (GC) and liquid chromatography (LC) analyses; and couplings of SPME with portable instruments permitting on-site measurements. Also, the latest advances in the preparation of sorbents applicable for direct extraction from complex biological matrices as well as applications of these extraction phases in food analysis and biomedical studies such as therapeutic drug monitoring and pharmacokinetics are described. Finally, recent trends in metabolomics analysis and examples of clinical monitoring of biomarkers with SPME are reviewed.     

Determination of Some Pharmaceutically – Important Aminoquinoline Antimalarials,via Charge – Transfer Complexes

Abstract

A simple and rapid spectrophotometric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primaquine phosphate is described. The method is based on the interaction of the drug with 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) as a π-electron acceptor, forming a highly coloured stable radical anion. The molecular ratios of the reactants in the complexes as well as the experimental conditions leading to maximum charge-transfer bands have been studied. Beer's Law is obeyed over aminoquinoline antimalarials concentration range of 0.4–4.0 ug.ml^?1. The proposed procedure has been applied successfully to the analysis of antimalarials in their dosage forms and the results are in agreement with those of official methods.     

Coordination of Heterovalent Iron Atoms in SrCo1 – yFeyO3 – zSolid Solutions

Mössbauer spectroscopy was used to study hyperfine interactions on ⁵⁷Fe nuclei of SrCo_{1 – y} Fe _y O_{3 – z} solid solutions (0.2 y 0.8). The ⁵⁷Fe spectra measured in the paramagnetic temperature range look like a superposition of two quadrupole doublets whose parameters correspond to high-spin Fe⁴⁺cations ( = 0.1 mm/s; = 0.4 mm/s) in the anion surrounding with coordination number 5 (tetragonal pyramid) and to Fe³⁺cations ( = 0.3 mm/s; = 0.4 mm/s) in the distorted octahedral environment. The relative number and pattern of distribution of heterovalent cations (Co⁴⁺, Co³⁺, Fe⁴⁺, and Fe³⁺) in the B-sublattice of perovskites were determined. The values of the electronic exchange constants in the solid solutions obtained through Mössbauer spectroscopy were compared with those obtained from thermodynamic calculations. The oxygen penetration in perovskites was found to depend on their composition and structure.     

Gel permeation chromatography – Atmospheric pressure chemical ionization – Mass spectrometry for oligomer characterization

The study presents the possibility to use gel permeation chromatography (GPC) with atmospheric pressure chemical ionization (APCI)–mass spectrometry (MS) for the analysis of oligomeric structures having molecular weights up to 2000?g?mol^?1. Polymethylmethacrylate and polystyrene oligomers were analyzed in chloroform using 2.1-mm-internal diameter GPC columns. The low flow rate of 50?µL?min^?1 and the ionization with chlorine allow a fast optimization of the method parameters. Excellent correlation with the expected isotope distributions and linear calibration curves were obtained for both types of oligomers.     

Towards oligoclusters – chemistry and properties

The recent progress of the author's research group in the syntheses, electronic properties and optical properties of monomeric and oligomeric organotransition metal cluster-containing systems is reviewed.     

Immunochromatographic techniques – a critical review

Hyphenated techniques have become very popular during the last decade. Nevertheless, the use of biochemical methods, such as immunoassays, in conjunction with instrumental methods, such as chromatography, have not gained widespread acceptance. This review critically discusses many of the implemented and potential options for such coupled systems or components, which might be useful for such systems, including immunoaffinity extraction, immunoaffinity chromatography, immunochemical detectors, immunoblotting, receptor assays, enzyme inhibition assays, displacement assays, flow-injection immunoassays, miniaturized techniques and stationary phases such as restricted access materials or molecularly imprinted polymers. The performance of immunochromatographic systems is discussed regarding their ability to solve highly complex and demanding analytical problems. Received: 7 September 1999 / Revised: 4 November 1999 / Acepted: 8 November 1999     

Reference materials – an industry perspective

Biotechnologically enhanced plants and products derived thereof continue to be the reason for much dispute. In order to address concerns raised by the public, several countries have imposed mandatory labeling schemes indicating the presence of products derived from modern biotechnology, while others rely on voluntary labeling codes. Mandatory labeling triggers the need for methods that can be used to check compliance with and enforcement of the corresponding labeling legislation. In order to ensure the proper validation and implementation of a detection method in a specific laboratory, reference materials play a crucial role.Electronic Supplementary Material Supplementary material is available for this article if you access the article at . A link in the frame on the left on that page takes you directly to the supplementary material.Presented at the CCQM Workshop on Comparability and Traceability in Food Analysis, 18–19 November 2003, BIPM, Sèvre, France.