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- EkRylander, B, et al.
(författare)
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Comparative studies of rat recombinant purple acid phosphatase and bone tartrate-resistant acid phosphatase
- 1997
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Ingår i: The Biochemical journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 321321 ( Pt 2), s. 305-311
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Tidskriftsartikel (refereegranskat)abstract
- The tartrate-resistant acid phosphatase (TRAP) of rat osteoclasts has been shown to exhibit high (85Ő94%) identity at the amino acid sequence level with the purple acid phosphatase (PAP) from bovine spleen and with pig uteroferrin. These iron-containing purple enzymes contain a binuclear iron centre, with a tyrosinate-to-Fe(III) charge-transfer transition responsible for the purple colour. In the present study, production of rat osteoclast TRAP could be achieved at a level of 4.3 mg/litre of medium using a baculovirus expression system. The enzyme was purified to apparent homogeneity using a combination of cation-exchange, hydrophobic-interaction, lectin-affinity and gel-permeation chromatography steps. The protein as isolated had a purple colour, a specific activity of 428 units/mg of protein and consisted of the single-chain form of molecular mass 34 kDa, with only trace amounts of proteolytically derived subunits. The recombinant enzyme had the ability to dephosphorylate bone matrix phosphoproteins, as previously shown for bone TRAP. Light absorption spectroscopy of the isolated purple enzyme showed a λmax at 544 nm, which upon reduction with ascorbic acid changed to 515 nm, concomitant with the transition to a pink colour. EPR spectroscopic analysis of the reduced enzyme at 3.6 K revealed a typical Ɓ-hydr(oxo)-bridged mixed-valent Fe(II)Fe(III) signal with g-values at 1.96, 1.74 and 1.60, proving that recombinant rat TRAP belongs to the family of PAPs. To validate the use of recombinant PAP in substituting for the rat bone counterpart in functional studies, various comparative studies were carried out. The enzyme isolated from bone exhibited a lower Km for p-nitrophenyl phosphate and was slightly more sensitive to PAP inhibitors such as molybdate, tungstate, arsenate and phosphate. In contrast with the recombinant enzyme, TRAP from bone was isolated predominantly as the proteolytically cleaved, two-subunit, form. Both the recombinant enzyme and rat bone TRAP were shown to be substituted with N-linked oligosaccharides. A slightly higher apparent molecular mass of the monomeric form and N-terminal chain of bone TRAP compared with the recombinant enzyme could not be accounted for by differential N-glycosylation. Despite differences in specific post-translational modifications, the recombinant PAP should be useful in future studies on the properties and regulation of the mammalian PAP enzyme.
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- Karlsson, M, et al.
(författare)
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Equilibrium and structural studies of silicon(IV) and aluminium(III) in aqueous solution. 33. The Al(methylmalonate)(2)(H2O)(2)(-) complex crystallised as a double salt with Al(H2O)(6)(3+) and Cl-
- 1998
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Ingår i: Acta Chemica Scandinavica. - 0904-213X .- 1902-3103. ; 52:8, s. 995-999
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of hexaaquaaluminium(III) trans-diaquabis(2-methylpropanedionate)aluminate(III) dichloride tetrahydrate, [Al(H2O)(6)(3+)] [Al(C4H4O4)(2)(H2O)(2-)][Cl-](2 .)4H(2)O, was determined by single-crystal X-ray diffraction. The compound crystallises in the triclinic space group , with a = 6.956(1), b = 8.413(2), c = 10.737(2) Angstrom, alpha = 89.78(2), beta = 106.90(2), gamma = 95.25(2)degrees and Z = 1. The refinement of 148 parameters on 2563 reflections [I > 2.0 sigma(I)] gave a final R-value of 0.076 (R-w = 0.052, S = 1.082). The double salt was crystallised from aqueous solution and contains two different octahedral aluminium complexes, an Al(H2O)(6)(3+) complex and an AlL2(H2O)(2)(-) complex with two methylmalonate ions equatorially coordinated and with two molecules of water at the apices. The structure is built up from layers of the Al complexes alternated with layers of chloride ions and water molecules parallel to the (010) plane.
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- Karlsson, M, et al.
(författare)
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Equilibrium and structural studies of silicon(IV) and aluminium(III) in aqueous solution. 34. A crystal structure determination of the Al(methylmalonate)(2)(CH3OH)(2)(-) complex with Na+ as counter-ion
- 1998
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Ingår i: Acta Chemica Scandinavica. - 0904-213X .- 1902-3103. ; 52:9, s. 1116-1121
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of sodium bis(trans)-2-methylpropanedionatedimethanolaluminate(III), [Na+][Al(C4H4O4)(2)(CH3OH)(2)(-)], has been determined by single crystal X-ray diffraction. The compound crystallises in the trigonal space group R (3) over bar, with a = 12.046(2), c= 28.705(6) Angstrom and Z= 9. The refinement of 103 parameters on 946 reflections [1>2.0 sigma(I)] gave a final R-value of 0.064 (R-w= 0.066, S= 1.000). The structure consists of octahedral Al(C4H4O4)(2)(CH3OH)(2)(-) complexes and sodium ions. In these complexes, methylmalonate coordinates to Ak(3+) bidentately in the equatorial plane of the octahedron, while methanol coordinates at the apices. As such, it represents a rare single-crystal example of direct aluminium( III)-methanol coordination. The complexes, arranged in layers, are connected to each other by octahedrally coordinated sodium ions, in special position 6c, and hydrogen bonds. The layers, with the methyl group of methylmalonate pointing out from the layers, are stacked perpendicular to the [001] direction and are held together by other octahedrally coordinated sodium ions, in special position 3b.
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