Fluorometric sensors based on chemically modified enzymes Glucose determination in drinks

In this paper an enzymatic fluorometric sensor for glucose determination in drinks is presented. The sensor film was obtained by immobilisation of glucose oxidase chemically modified with a fluorescein derivative (GOx-FS) in a polyacrylamide polymer. During the enzymatic reaction the changes in the fluorescence intensity of the GOx-FS are related to the glucose concentration. Working in FIA mode, the optimum conditions found were: 0.7 ml min(-1) flow rate, 300 mul sample injection and pH 6.5. The sensor responds to glucose concentrations ranging from 400 to 2000 mg l(-1), the reproducibility is around 3% and the life-time is at least 3 months (more than 350 measurements). The sensor was applied to direct glucose determination in drinks with good accuracy; interference caused by the filter effect was avoided by the kinetics of the reaction.     

Unusual synthesis of azines and their oxidative degradation to carboxylic acid using iodobenzene diacetate

Reaction of 3-hydrazonobutan-2-one oxime with aromatic aldehydes resulted in the formation of 1,2-bis(arylidene)hydrazine commonly referred as azine as an unexpected product, instead of expected product 3-(aryl)methylenehydrazonobutan-2-one oxime, which were subsequently oxidized to corresponding aromatic acids with an ecofriendly oxidizing agent iodobenzene diacetate. Azines and carboxylic acids were characterized by IR and NMR (¹H, ¹³C, HMBC, and HMQC) studies.     

The structure of glibenclamide in the solid state

The structure of glibenclamide, 5‐chloro‐N‐(2‐{4‐[(cyclohexylamino)carbonyl] aminosulfonyl}phenyl) ethyl)‐2‐methoxybenzamide, an important antidiabetic drug, has been studied both in solution and in the solid state by a combination of NMR spectroscopy and theoretical calculations. The possibility that glibenclamide suffers a tautomerization under melting to afford a desmotrope was rejected. Copyright © 2012 John Wiley & Sons, Ltd.     

An Adjustable Cleft Based on an 8-Sulfonamide-2-Naphthoic Acid with Oxyanion Hole Geometry

Cleft type receptors showing the oxyanion hole motif have been prepared in a straightforward synthesis starting from the commercial 3,7-dihidroxy-2-naphthoic acid. The double H-bond donor pattern is achieved by the introduction of a sulfonamide group in the C-8 position of naphthalene and a carboxamide at the C-2 position. This cleft, for which the geometry resembles that of an oxyanion hole, is able to adjust to different guests, as shown by the analysis of the X-ray crystal structures of associates with methanol or acetic acid. Combination of hydrogen bonds and charge-transfer interactions led to further stabilization of the complexes, in which the electron-rich aromatic ring of the receptor was close in space to the electron-deficient dinitroaromatic guests. Modelling studies and bidimensional NMR experiments have been carried out to provide additional information.     

Exploring the Reactivity of α‐Lithiated Aryl Benzyl Ethers: Inhibition of the [1,2]‐Wittig Rearrangement and the Mechanistic Proposal Revisited

By carefully controlling the reaction temperature, treatment of aryl benzyl ethers with tBuLi selectively leads to α‐lithiation, generating stable organolithiums that can be directly trapped with a variety of selected electrophiles, before they can undergo the expected [1,2]‐Wittig rearrangement. This rearrangement has been deeply studied, both experimentally and computationally, with aryl α‐lithiated benzyl ethers bearing different substituents at the aryl ring. The obtained results support the competence of a concerted anionic intramolecular addition/elimination sequence and a radical dissociation/recombination sequence for explaining the tendency of migration for aryl groups. The more favored rearrangements are found for substrates with electron‐poor aryl groups that favor the anionic pathway.     

M?ssbauer spectroscopic study of iron�Cnickel nitrides thin films prepared by ion beam assisted deposition

An overview is given of the present status of parity violation tests in neutron decay and nuclear beta decay. Prospects for improved and new measurements are discussed as well.     

Intermolecular spin–spin coupling constants between P atoms

This paper reports the study by NMR spectroscopy and ab initio methods of the structure of 3,4-dimethyl-1-cyanophosphole and its dimer. The dimer presents a P···P interaction of the pnictogen type due to the presence of σ-holes. NMR of the monomer was recorded in CDCl₃ solution while NMR of the dimer corresponds to the solid state (CPMAS) experiments. The ^2pJ_PP spin–spin coupling constant has not been measured, but calculated at the B3LYP level. AIM, NBO and ELF methodologies have been used to describe the electronic structure of the dimer.     

Identification of bioactive peptides in hypoallergenic infant milk formulas by CE‐TOF‐MS assisted by semiempirical model of electromigration behavior

Biologically active peptides derived from complex bovine milk protein hydrolysates are of particular interest in food science and nutrition because they have been shown to play different physiological roles, providing benefits in human health. In this study, we used CE‐TOF‐MS for separation and identification of bioactive peptides in three hypoallergenic infant milk formulas. An appropriate sample cleanup using a citrate buffer with DTT and urea followed by SPE with Sep‐Pack® C18 and StrataX^TM cartridges allowed the detection of a large number of low molecular mass bioactive peptides. This preliminary identification was solely based on the measured experimental monoisotopic molecular mass values (M_exp). Later, we evaluated the classical semiempirical relationships between electrophoretic mobility and charge‐to‐mass ratio (m_e vs. q/M^α, α = 1/2 for the classical polymer model) to describe their migration behavior. The assistance of migration prediction proved to be useful to improve reliability of the identification, avoiding misinterpretations and solving some identity conflicts. After revision, the identity of 24, 30, and 38 bioactive peptides was confirmed in each of the three infant milk formulas. A significant number of these peptides were reported as inhibitors of angiotensin‐converting enzyme, however, the presence of sequences with other biological activities such as antihypertensive, antithrombotic, hypocholesterolemic, immunomodulation, cytotoxicity, antioxidant, antimicrobial, antigenic, or opioid was also confirmed.