Fractionation and purification of antioxidant peptides from Chinese sturgeon (Acipenser sinensis) protein hydrolysates prepared using papain and alcalase 2.4L

Protein hydrolysates have the potential to be natural and safer sources of bioactive peptides. In this study, two proteases were used to hydrolyze Chinese sturgeon (Acipenser sinensis) protein, and the hydrolysates were then purified to yield antioxidant peptides. The degree of hydrolysis of 23.56 % and 18.14 % was obtained using papain and alcalase 2.4L, respectivly, and hydrolysates had 96.80 % and 87.24 % total amino acid content, respectivly. The papain hydrolysate (PH) and alcalase 2.4L hydrolysate (AH) showed good antioxidant activity against DPPH^? (IC₅₀ of 3.64 and 3.15 mg/mL) and ABTS^?+ (IC₅₀ of 1.92 and 1.58 mg/mL), respectively. The low-molecular-weight (<1000 Da) fraction of both hydrolysates demonstrated the highest antiradical activity (IC₅₀ of 2.59 and 2.31 mg/mL, DPPH) and (IC₅₀ of 1.54 and 1.36 mg/mL, ABTS), respectively. Nine peptides were separated from both hydrolysates using reverse phase high performance liquid chromatography (RP-HPLC). The IC₅₀ for ABTS^?+ scavenging activity of peptide P5 with valine, glycine and asparagine (MW of 282.13 Da) from PH, and peptide P3 with histidine, glycine and alanine (MW of 302.74 Da) from AH was 0.89 and 0.72 mg/mL, respectively. The fractions and purified peptides obtained from Chinese sturgeon hydrolysates could be utilized as natural antioxidant substitutes in pharmaceuticals and food products.     

Wavelength-modulated,continuum-source excited atomic fluorescence spectrometric system for wear metals in jet engine lubricating oils using electrothermal atomization

A system for measuring atomic fluorescence of atoms produced via an electrically-heated graphite filament in a flame (acetylene/air or acetylene/nitrous oxide) and excited with a 300-W Eimac xenon are lamp is described. The experimental system also included wavelength modulation for background emission/fluorescence/scatter correction and an optically-triggered electronic integrator for efficient monitoring of the analyte fluorescence signal. Copper, aluminum and molybdenum were determined in jet engine lubricating oil samples (1 μl) with no pretreatment. The determinations are evaluated with respect to the accuracy and repeatability criteria of the U.S. Joint Oil Analysis Program.     

Thermal Decomposition of Bi(III), Cd(II), Pb(II) and Cu(II) Thiocyanates

Thermal decomposition of Bi(SCN)₃, Cd(SCN)₂, Pb(SCN)₂ and Cu(SCN)₂ has been studied. The thermal analysis curves and the diffraction patterns of the solid intermediate and final products of the pyrolysis are presented. The gaseous products of the decomposition (SO₂ and CO₂) were detected and quantitatively determined. Thermal, X-ray and chemical analyses have been used to establish the nature of the reactions occurring at each stage in the decomposition.This revised version was published online in November 2005 with corrections to the Cover Date.     

2-Polyfluoroalkylchromones. 9. Synthesis and structures of 5-(2-hydroxyaryl)-7-polyfluoroalkyl-1,4,8-triazabicyclo[5.3.0]dec-4-enes

2-Polyfluoroalkylchromones reacted with diethylenetriamine at 20 °C to form the corresponding 1,4,8-triazabicyclo[5.3.0]dec-4-ene derivatives. The crystal structures of 5-(2-hydroxyphenyl)-7-trifluoromethyl-1,4,8-triazabicyclo[5.3.0]dec-4-ene and 1-(2-aminoethyl)-7-(2-hydroxy-5-methoxyphenyl)-5-(1,1,2,2-tetrafluoroethyl)-2,3-dihydro-1H-1,4-diazepine were established by X-ray diffraction analysis.     

Molecular structures of β-amino-α-bromovinyl trifluoromethyl ketones

The molecular structures of β-amino-α-bromovinyl trifluoromethyl ketones was studied by UV, IR, ¹H, ¹³C, and ¹⁵N NMR spectroscopy and using the density functional (B3LYP/6-31G(d,p) and PBE/QZ3P) and ab initio riMP2/cc-pVTZm quantum-chemical calculations. Factors affecting stabilization of the EZE-conformation of the molecules, which is atypical of analogous unsubstituted amino enones, are considered.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 102–106, January, 2005.     

Thermal decomposition of cobalt nitrato compounds: Preparation of anhydrous cobalt(II)nitrate and its characterisation by Infrared and Raman spectra

The thermal decomposition of Co(NO₃)₂·6H₂O (1) as well as that one of NO[Co(NO₃)₃] (Co(NO₃)₂·N₂O₄) (2) was followed by thermogravimetric (TG) measurements, X-ray recording and Raman and IR spectra. The stepwise decomposition reactions of 1 and 2 leading to anhydrous cobalt(II)nitrate (3) were established. In N₂ atmosphere, cobalt oxides are finally formed whereas in H₂/N₂ (10% H₂) cobalt metal is produced. Rapid heating of cobalt(II)nitrate hexahydrate causes melting (formation of a hydrate melt) and therefore side reactions in the hydrate melt by incoupled reactions and evolution/evaporation of different species as, e.g., HNO₃, NO₂, etc. In case of larger amounts in dense packing in the sample container, the formation of oxo(hydoxo)nitrates is possible at higher temperature. For 2, its thermal decomposition to 3 was followed and its decomposition mechanism is proposed.     

Use of 1-alkyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquids as chelate extraction solvent with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione

Possible use of room temperature ionic liquids (RTILs) as chelate extraction solvent was evaluated by using 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF₆]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF₆]). These RTILs showed high extraction performance for divalent metal cations with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htta). The extracted metals were back-extracted into 1 mol dm⁻³ nitric acid quantitatively. Furthermore, the extracted species were estimated as neutral hydrated complexes M(tta)₂(H₂O)_n (n= 1 or 2) for M = Ni, Cu and Pb and anionic complexes M(tta)₃⁻ for M = Mn, Co, Zn and Cd.     

β-Ketoaldehydes in the synthesis of 6-alkyl-3-cyano-2(1H)-pyridinethiones

An efficient synthesis of 6-alkyl-3-cyano-2(1H)-pyridinethiones by the reactions of the sodium salts of -ketoaldehydes with cyanothioacetamide was developed. Pyridinethiones undergo selectiveS-alkylation with haloacetonitriles and haloacetophenones followed by cyclization to the corresponding thieno[2,3-b]pyridines.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 727–731, April, 1995.This study was financially supported by the Russian Foundation for Basic Research (Project No. 94-03-08-823).     

Ab initio studies of the protonation of CO,N2 and NO+: Calculation of the minimum energy reaction paths

Ab initio molecular orbital calculations employing a 4-31G basis set have been used to study the minimum energy paths for the formation of HCO⁺, COH⁺, and HCOH²⁺ from CO by protonation. The protonation of N₂ to give NNH⁺ and HNNH²⁺ and of NO⁺ to form HNO²⁺ and NOH²⁺ have also been investigated. All species formed have linear equilibrium geometries and the minimum energy path for approach of the proton is along the line-of-centers of the heavy atoms. Energy barriers to the formation of the various species are given, where appropriate, and changes in geometry, ordering of molecular orbitals and orbital occupancy are discussed.     

New insight into the oxidative chemistry of noradrenaline: competitive o-quinone cyclisation and chain fission routes leading to an unusual 4-[bis-(1H-5,6-dihydroxyindol-2-yl)methyl]-1,2-dihydroxybenzene derivative

Oxidation of 5×10⁻³ M noradrenaline in aqueous phosphate buffer, pH 7.4, with K₃Fe(CN)₆, NaIO₄ or Fe²⁺/EDTA/H₂O₂ followed by extraction with ethyl acetate and acetylation with Ac₂O/Pyr led to a main reaction product which was isolated and identified as 4-[bis-(1H-5,6-diacetoxyindol-2-yl)methyl]-1,2-diacetoxybenzene, an unprecedented [bis-(indol-2-yl)methyl]-benzene derivative unsubstituted on the 3-position of the indole rings. This product was also obtained in 40% yield by reaction of 5,6-dihydroxyindole with 3,4-dihydroxybenzaldehyde. Other components of the oxidation mixture were 1-acetyl-3,5,6-triacetoxyindole, derived from noradrenolutin, and 5,6-diacetoxyindole, originating from cyclisation/dehydration of the o-quinone of noradrenaline, along with some 3,4-diacetoxybenzaldehyde. Inspection of the aqueous phase revealed the presence of 3,4-dihydroxymandelic acid and 3,4-dihydroxybenzaldehyde, derived from oxidative breakdown of the 2-amino-1-hydroxyethyl chain via a p-quinomethane intermediate. These results disclose new aspects of the oxidative chemistry of noradrenaline beyond the aminochrome stage and provide a route to novel [bis-(indol-2-yl)methyl]-benzene derivatives of potential pharmacological interest.