13C and 1H NMR spectral studies of N-alkylmethylquinolinium salts

¹³C and ¹H chemical shifts of fourteen N-alkylmethylquinolinium salts in DMSO-d₆ are reported, and compared with those of the eleven corresponding methylquinoline bases. The influence of ring substitution by methyl groups in the salts and substitution at the nitrogen atom and the effect of the anion are discussed.     

Quotients of peripherally continuous functions

We characterize the family of quotients of peripherally continuous functions. Moreover, we study cardinal invariants related to quotients in the case of peripherally continuous functions and the complement of this family.     

Highly enantioselective hydrogenation of 3,5-diketo esters: a formal synthesis of tetrahydrolipstatin

Compound 4, obtained via a sequence of two consecutive alkylations of methyl 3,5-dioxohexanoate (5), was transformed into the enantiomerically pure lactone (3S,4S,6R)-2 being the precursor of tetrahydrolipstatin (1). The reaction sequence involves asymmetric catalytic hydrogenation of 4 as a crucial step.     

Allosteric inhibition of the protein-protein interaction between the leukemia-associated proteins Runx1 and CBFbeta

The two subunits of core binding factor (Runx1 and CBFbeta) play critical roles in hematopoiesis and are frequent targets of chromosomal translocations found in leukemia. The binding of the CBFbeta-smooth muscle myosin heavy chain (SMMHC) fusion protein to Runx1 is essential for leukemogenesis, making this a viable target for treatment. We have developed inhibitors with low micromolar affinity which effectively block binding of Runx1 to CBFbeta. NMR-based docking shows that these compounds bind to CBFbeta at a site displaced from the binding interface for Runx1, that is, these compounds function as allosteric inhibitors of this protein-protein interaction, a potentially generalizable approach. Treatment of the human leukemia cell line ME-1 with these compounds shows decreased proliferation, indicating these are good candidates for further development.     

Cyclic chronopotentiometric determination of sugars at Au and Pt microelectrodes in flowing solutions

The main advantage of the application of cyclic chronopotentiometry (CCP) in end-column CE detection arises from the fact that the detection parameters and the magnitude of the analytical signal are (in contrast with other electrochemical detection methods) independent of the ohmic polarization of the solution caused by the separation current at the detection end of the capillary. CCP was used to determine sugars on platinum and gold microelectrodes after separation by CE. The results obtained with a gold microelectrode were better. Subsequently this detection method was used for quantitative determination of sugars in honeys and for their authentication.     

Determination of β-blockers and β-agonists using gas chromatography and gas chromatography-mass spectrometry--a comparative study of the derivatization step

There is a growing demand for the rapid screening of multiple β-blockers and β-agonists in a single analytical run in clinical toxicology, antidoping control, forensic and environmental science. Although GC-MS is very often used to determine pharmaceuticals from these groups of drugs, the literature data on the derivatization and MS analysis of mixtures of these compounds is limited. This paper compares and evaluates derivatization procedures for the determination of six β-blockers (acebutolol, atenolol, metoprolol, nadolol, propranolol, pindolol) and two β-agonists (salbutamol, terbutaline) using GC techniques. Nineteen different derivatizing reagents (nine of them used for the first time with almost all the drugs) were employed in order to obtain a single derivative for each target compound with the greatest effectiveness of this reaction. Trimethylsilylation, tert-butyldimethylsilylation, acylation (e.g. trifluoroacetylation), combined trimethylsilylation and acylation, and the formation of cyclized silyl derivatives were carried out and the mass spectra (EI, 70 eV) recorded. The influence of the reaction time and temperature on these procedures was investigated. Additionally, the effects of the type of solvent and the amount of added trimethylchlorosilane (TMCS) on the silylation of the target compounds using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) were tested. Among of the five mentioned above derivatization procedures applied - trimethylsilylation was found to be the most effective for derivatizing the analytes. The best results were obtained with a 1:1 (v/v) mixture of 99% BSTFA+1% TMCS and ethyl acetate at 60 °C for 30 min. The MS data for different types of β-blocker and β-agonist derivatives is presented. The information in this paper is valuable for scientists working on the determination of β-blockers and β-agonists in biological and environmental matrices.     

Properties and determination of pesticides in fruits and vegetables

The intensive development of agriculture means that more and more toxic organic and inorganic compounds are entering the environment. Because of their widespread use, stability, selective toxicity and bioaccumulation, pesticides are among the most toxic substances contaminating the environment. They are particularly dangerous in fruit and vegetables, by which people are exposed to them. It is therefore crucial to monitor pesticide residues in fruit and vegetables using all available analytical methods.We set out the problems in the determination of organonitrogen and organophosphorus pesticides in samples of fruit and vegetables, including the complexity and the diversity of matrices in biological materials, and the very low level of pesticides present, as a result of which target analytes have to be isolated and then enriched prior to final determination.We discuss the various stages in the determination of pesticide residues in fruit and vegetables. We present results from the literature in the context of Maximum Residue Levels (MRLs) of target pesticides in fruit and vegetable samples. We discuss the merits of the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) technique and two-dimensional gas chromatography.     

Flocculation of Bacillus amyloliquefaciens H Disintegrates with Cationized Starch and Aminated Hydroxyethylcellulose

The ability of cationized hydroxyethylated starch (CHES) and aminated hydroxyethylcellulose (DEAE-HEC) to flocculate cell disintegrate of Bacillus amyloliquefaciens H (BamHI) was investigated. The efficiency of flocculation was compared to that of synthetic polymer polyethyleneimine (PEI) and natural polysaccharide chitosan. The influence of salt concentration and biomass concentration on flocculation efficiency was investigated. It was found that the efficiency of flocculation with CHES and DEAE-HEC was similar to that of PEI but better compared to chitosan. Recovery of total soluble proteins at higher than 0.3% concentration of flocculant decreased by more than 18.8% and 42.3% compared to PEI and chitosan, respectively. The yield of BamHI restriction endonuclease activity with all flocculants was similar except for chitosan where 13.1% lower yield was obtained. Meanwhile, efficiency of flocculation with CHES and DEAE-HEC depends drastically on the salt concentration, that is, flocculation diminishes if NaCl concentrations higher than 0.2 M (for CHES) or 0.1 M (for DEAE-HEC) are used. The results have shown that CHES and DEAE-HEC are promising flocculants of cell disintegrates if higher yield of protein is of great concern.