Elemental analysis of Korean women’s blood serums using instrumental neutron activation analysis

Instrumental neutron activation analysis was used to assess the concentration of the inorganic trace elements in Korean women’s blood serums. It was found that a high concentration of Na and Cl incurs an analytical interference, but the 12 elements such as Br, Ca, Cl, Co, Cr, Cs, Fe, K, Na, Rb, Se and Zn could be determined under the condition of an interference minimization. Serum samples collected from 63 women were analyzed and the concentration level and range of the elements were evaluated. NIST SRMs were analyzed simultaneously for quality control. The average values of the Na and Cl determined in the serum samples were 3,365 and 3,533 mg/l, Ca was 96.4 mg/l and K was 191 mg/l. Besides, Br, Se and Zn have a concentration level of 6.46, 0.13 and 0.98 mg/l, respectively. It was found that there is no significant difference between the present values and the reported values.     

Characterisation of poly(neutral red) modified carbon film electrodes; application as a redox mediator for biosensors

The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing with PNR-mediated electrochemical degradation of H₂O₂ formed during the enzymatic process. This paper is dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday.     

Technological quality determination of pharmaceutical disintegrant by DSC cooling and DSC photovisual

A number of disintegrants are available on the market. They improve tablets’ disintegration. The objective of this work is the comparison of the technological quality parameters of disintegrants using different analytical techniques. Three batches of disintegrants and their binary mixtures (water:disintegrants) were investigated. Cooling experiments were used from –30 up to 200°C. The data obtained showed calorimetric differences between the samples. In the binary mixtures water showed different crystallization behaviour from the one found in the literature. According to the results DSC technique helped the quality control of different disintegrants.     

Thermodynamic characterization of different actin isoforms

Summary The thermodynamic properties of the cardiac and skeletal a-actin isoforms were studied to characterize the molecular bases of the functional differences between them with the method of differential scanning calorimetry (DSC). The thermal properties of the actin filaments were described in the presence of calcium and magnesium ions as well. Based on the calculated free energy changes the α-cardiac actin filaments appeared to be more stable in its physiologically more relevant, magnesium saturated form. The magnesium saturated form of the α-cardiac actin filaments seemed to be more stable compared to the calcium saturated form of it. The enthalpy and entropy changes could differentiate between the α-cardiac and α-skeletal actin isoforms and between the calcium and magnesium saturated cardiac actin isoforms as well. Our results can demonstrate that the few differences between the amino acid sequences of the α-actin isoforms have an influence on the thermal properties and maybe on the function of these proteins as well.     

Lewis acid promoted cyclization of enyne triesters and diesters

Reactions of enynes with three or two ester groups (1-4) in the presence of halogen-ligand Lewis acids gave cyclized products with halide incorporation (5-8) with high generality. The cyclization process was also analyzed in a theoretical study. Facile isomerization and dehydrohalogenation of five-membered products 5 and 8 by Al(2)O(3) or Et(3)N were also observed; this process introduces conjugated moieties into the products.     

Enantioselectively catalyzed oxidation of 3,4-dihydroxy-l-phenylalanine by N-lauroyl L or D-histidine-Cu(II) complex in CTABr micelles.

In order to investigate the enzyme model reaction the oxidation of 3,4-dihydihydroxy-L-phenylalanine(L-DOPA) was carried out using optically active catalyst, N-lauroyl L or D-histidine-Cu(II) complex(L or D-LauHis-Cu(II)), showing appreciable enantioselectivity in the presence of the mixed micelles with CTABr.     

Molecular basis for antifreeze activity difference of two insect antifreeze protein isoforms

The insect spruce budworm(Choristoneura fumiferana) produces antifreeze protein(AFP) to assist in the protection of the over-wintering larval stage and contains multiple isoforms. Structures for two isoforms,known as CfAFP-501 and CfAFP-337,show that both possess similar left-handed β-helical structure,although thermal hysteresis activity of the longer isoform CfAFP-501 is three times that of CfAFP-337. The markedly enhanced activity of CfAFP-501 is not proportional to,and cannot be simply accounted for,by the increased ice-binding site resulting from the two extra coils in CfAFP-501. In or-der to investigate the molecular basis for the activity difference and gain better understanding of AFPs in general,we have employed several different computational methods to systematically study the structural properties and ice interactions of the AFPs and their deletion models. In the context of intact AFPs,a majority of the coils in CfAFP-501 has better ice interaction and causes stronger ice lattice disruption than CfAFP-337,strongly suggesting a cooperative or synergistic effect among β-helical coils. The synergistic effect would play a critical role and make significant contributions to the anti-freeze activity β-helical antifreeze proteins. This is the first time that synergistic effect and its implica-tion for antifreeze activity are reported for β-helical antifreeze proteins.     

Catalytic asymmetric Michael reaction of beta-keto esters: effects of the linker heteroatom in linked-BINOL

We describe the development of a general catalytic asymmetric Michael reaction of acyclic beta-keto esters to cyclic enones, in which asymmetric induction occurs at the beta-position of the acceptors. Among the various asymmetric catalyst systems examined, the newly developed La-NR-linked-BINOL complexes (R = H or Me) afforded the best results in terms of reactivity and selectivity. In general, the NMe ligand 2 was suitable for the combination of small enones and small beta-keto esters, and the NH ligand 1 was suitable for bulkier substrates (steric tuning of the catalyst). Using the La-NMe-linked-BINOL complex, the Michael reaction of methyl acetoacetate (8a) to 2-cyclohexen-1-one (7b) gave the corresponding Michael adduct 9ba in 82% yield and 92% ee. The linker heteroatom in linked-BINOL is crucial for achieving high reactivity and selectivity in the Michael reaction of beta-keto esters. The amine moiety in the NR-linked-BINOL can also tune the Lewis acidity of the central metal (electronic tuning of the catalyst), which was supported by density functional studies and experimental results. Another advantage of the NR-linked-BINOL ligand as compared with O-linked-BINOL is the ease of modifying a substituent on the amine moiety, making it possible to synthesize a variety of NR-linked-BINOL ligands for further improvement or development of new asymmetric catalyses by introducing additional functionality on the linker with the amine moiety. The efficiency of the present asymmetric catalysis was demonstrated by the synthesis of the key intermediate of (-)-tubifolidine and (-)-19,20-dihydroakuammicine in only five steps compared to the nine steps required by the original process from the Michael product of malonate. This strategy is much more atom economical. On the basis of the results of mechanistic studies, we propose that a beta-keto ester serves as a ligand as well as a substrate and at least one beta-keto ester should be included in the active catalyst complex. Further improvement of the reaction by maintaining an appropriate ratio of the La-NMe-linked-BINOL complex and beta-keto esters is also described.     

Do proficiency tests always verify laboratories’ performance? The case of FAPAS PT 0270

In this paper, the case of FAPAS PT 0270 “Doramectin and Oxfendazole in Sheep Liver” is discussed. During evaluation of the data received from participants (determination of total, oxidised oxfendazole residue and calculation of the sum of oxfendazole and oxfendazole sulfone residues), significant differences were observed between the results obtained by use of two analytical approaches. This phenomenon can be explained by the route of oxfendazole metabolism, which results in the presence of fenbendazole in the sample. This was not predicted by the provider; consequently, not all the necessary tests on the material were conducted. Due to the high uncertainty of the z-scores in this test, the results of the PT cannot be used for purposes of evaluation, and the benefits of participation in PT 0270 are questionable.     

Evaluation of chiral bidentate ligand–metal complexes in asymmetric 1,3-dipolar cycloaddition reaction of nitrones with 3-alkenoyl-2-oxazolidinones

For evaluation of a chiral C₂-symmetric bis(oxazoline) ligand, its Lewis acid complexes-catalyzed asymmetric 1,3-dipolar cycloaddition reactions of nitrones with electron-deficient dipolarophiles, 3-(2-alkenoyl)-1,3-oxazolidin-2-ones, have been investigated and it was found that the cycloadditions using a Cu(II)-bis(oxazoline) complex under optimized reaction conditions induced extremely high enantioselectivity.