Mineralogy and geochemistry of clay fractions in soils developed from different parent rocks in Limpopo Province, South Africa.

This study investigates the mineralogical and geochemical characteristics of clay fractions in soils developed from different parent rocks in Limpopo Province, South Africa using the X-ray diffraction (XRD), X-ray Fluorescence (XRF) Spectrometry, Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS), Fourier Transform Infrared (FTIR) Spectrophotometry, Thermogravimetric Analysis and Differential Scanning Calorimetry (TGA-DSC) analytical techniques. Health risk associated with the presence of some trace elements was also investigated. The results revealed that the clay fractions had kaolinite as the dominant clay component occurring with other weatherable minerals. The crystallinity based on FTIR for the soil kaolinites correspond to partially - poorly ordered structures. The geochemical data showed appreciable accumulation of trace elements in the clay fractions. The absence of negative Ce anomaly in the chrondrite-normalised rare earth elements (REE) pattern in the clay fractions suggest the alteration of the primary minerals took place under suboxic conditions. The average non-carcinogenic hazard index (HI) were 1.52, 1.08, and 2.01 for children and 0.18, 0.13, and 0.24 for adults in the clay fractions from basalt, granite, and arkosic sandstone, respectively. The HI > 1 for children suggest non-carcinogenic health risk to children with ingestion pathway contributing the highest. The average carcinogenic risk index values were >10-3 for children and adults with respect to Cr, Ni, and Pb in the clay fractions. This suggests very high carcinogenic risk to children and adult population in decreasing order from clay fractions in arkosic sandsone > basalt > granite, respectively.

N-acetyl alpha-D-glucosaminidase from the venom of African puff adder (Bitis arietans).

The activity of N-acetyl-alpha-D-glucosaminidase from venom of the African puff adder (Bitis arietans) has been detected. The enzyme from the venom was purified by chromatography on Q-sepharose, CM-cellulose, and N-acetyl-alpha-D-glucosamine-agarose affinity column. The enzyme has a molecular weight of 102 kDa determined by size exclusion chromatography on Sephacryl 200. It migrated as a 51-kDa band on SDS polyacrylamide gels. The enzyme is maximally active at pH 5.5 and 40 degrees C. The B. arietans NAGase hydrolyzed exclusively terminally linked alpha-(1-4) GlcNAc residues from nonreducing ends of oligosaccharides. It hydrolysed chito-oligosaccharide, MU-GlcNAc and chitobiose with K(M) values of 0.15 mM and 1.22 mM, respectively. Swollen chitin and oligosaccharide above (GlcNAc)(4) were not hydrolysed by the enzyme. B. arietans NAGase was strongly inhibited noncompetitively by Hg(2+), competitively by 1-thio-beta-D-GlcNAc and N-acetyl glucosamine (NAG) with K(i) of 0.55, 0.25 and 8 mM, respectively. Colombin the active component of antivenom preparation from Aristolodia albida inhibited the enzyme competitively with K(i) of 0.6 mM. Delineation of the active site by chemical modification revealed the involvement of His and Trp in the catalysis of the enzyme.