Synthesis and spectral characterization of some oxo-centered,trinuclear mixed-valence iron thiocarboxylates

Some mixed-valence Fe(II) Fe(III) complexes of thiocarboxylic acids and straight chain fatty acids with general formula [Fe(II)Fe(III)(2)O(SOCR)(6)(H(2)O)(3)] and [Fe(II)Fe(III)(2)O(SOCR)(3)(OOCR')(3)(CH(3)OH)(3)] (where, R=CH(3) or C(6)H(5) and R'=C(13)H(27), C(15)H(31) or C(17)H(35)) were synthesized and characterized by elemental analyses, spectral (infrared, electronic and M?ssbauer) studies, molar conductance and magnetic susceptibility measurements. The infrared spectra suggested bridging nature of carboxylate and thiocarboxylate anions along with upsilon(asym)(Fe(3)O) vibrations in the complexes. M?ssbauer studies revealed two resolved quadrupole doublets at 120-315 K confirming the presence of Fe(II) and Fe(III) moieties in the complexes. This was supported by the observed electronic spectral bands in the complexes at room temperature. The spectrum showed a band at around 13,800 cm(-1) which indicated an intervalence-transfer. Magnetic susceptibility measurements showed weak antiferromagnetic coupling related to mixed-valence pairs with S(2)=2, em leader S(1)=S(3)=5/2 spin exchange model. Conductance data indicated, the complexes were non-electrolytes in nitrobenzene. A structure has been established on the basis of these studies.     

Characterization of oligosaccharide moieties of intact glycoproteins by microwave-assisted partial acid hydrolysis and mass spectrometry

A method, which utilizes microwave-assisted partial acid hydrolysis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), to elucidate oligosaccharide composition of intact glycoproteins is presented here. Glycoproteins, such as ribonuclease B, avidin, alpha1-acid glycoprotein, and fetuin, are used as model systems to demonstrate this technique. Partial cleavage of oligosaccharides from whole intact glycoproteins with trifluoroacetic acid was observed after a short exposure to microwaves. Due to the high-resolution mass spectra obtained by MALDI-TOFMS from glycoproteins with molecular weights less than 20 kDa, the compositions of oligosaccharides are readily derived for ribonuclease B and avidin. The data agree with the proposed oligosaccharide structures of ribonuclease B (five glycoforms) and avidin (eight glycoforms). Larger glycoproteins such as alpha1-acid glycoprotein (many glycoforms) and fetuin (many glycoforms) exhibited only broad peaks with no glycoform resolution. Nevertheless, this method can be used successfully for analysis of glycoproteins with molecular weights greater than 20 kDa to determine the presence or absence of glycosylation.     

Reversibly soluble macroaffinity ligand in aqueous two-phase separation of enzymes

Use of alginate as a free bioligand incorporated in an aqueous two-phase system of polyethylene glycol 6000-salt resulted in considerable purification of wheat germ alpha-amylase and sweet potato beta-amylase from their crude extracts. The elution of the enzyme from the free bioligand was facilitated by exploiting the fact that alginate can be reversibly precipitated in the presence of Ca2+. alpha-Amylase could be purified 42-fold with 92% activity recovery. beta-Amylase on the other hand could be purified 43-fold with 90% recovery. Both purified enzymes showed a single band on sodium dodecylsulfate-polyacrylamide gel electrophoresis.     

A new glycoside, 3-O-demethylcolchicine-3-O-alpha-d-glucopyranoside, from Gloriosa superba seeds

A new colchicine glycoside, 3-O-demethylcolchicine-3-O-alpha-D-glucopyranoside, has been isolated from Gloriosa superba seeds. The assigned structure has been corroborated by spectroscopic data and enzymatic hydrolysis.     

Determination of the rare earths, yttrium and scandium in silicate rocks and four new geological reference materials by electrothermal atomization from graphite and tantalum surfaces

An improved graphite furnace atomic-absorption method has been developed for the determination of Sc, Y and the rare-earth elements in silicate rocks and related materials. The method, which involves the separation of the lanthanides by ion-exchange followed by their determination by electrothermal atomization, with use of an automatic sampling device, is more rapid than a previous method based on separation by co-precipitation with calcium oxalate and hydrous ferric oxide followed by normal injection of the solution into the furnace. Greater sensitivity (~ 10-40-fold) for La, Ce, Pr, Gd, Tb and Lu is also achieved by using a tantalum foil-lined graphite furnace instead of a pyrolytically-coated furnace. Results obtained for five international reference rock samples, NIM-G, SCo-1, MAG-1, SDC-1 and BHVO-1, are compared with those obtained previously by the oxalate-hydrous oxide co-precipitation method and with other published values. Results are given for four new Canadian iron-formation reference materials, FeR-1 to FeR-4.     

Oscillatory behavior in the reaction of 3-alizarin-sulfonic acid sodium salt with acidic bromate

Uncatalyzed and catalyzed oscillatory behavior in the redox potential in the oxidation of 3-alizarin-sulfonic acid sodium salt with acidid (H₂SO₄) bromate is reported. Optimum and boundary conditions for each reactant exhibiting oscillatory behavior have been studied and a probable mechanism is suggested.

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- 3-- (H₂SO₄) . , .

     

On the Stable Radical of Some Non-Domestic String Algebras

Algebras and Representation Theory - We introduce the concept of a prime band in a string algebra Λ and use it to associate to Λ its finite bridge quiver. Then we introduce a new...