Cultures thermal stability

The liver (Cu,Zn)-SOD of old rats (27 months) showed a 60% reduction of specific activity, the presence of antigenically cross-reacting material, and a decreased thermal stability in comparison with the enzyme of young rats (6 months) . Similar observations were made with ageing human fibroblasts in culture, whereby the absence of a cytosolic stabilizing factor was suspected in old cells... 

The factors which Influence the choice of formulation are pesticide physical properties (melting point, solubility, volatility), pesticide chemical properties (hydrolytic stability, thermal stability), soil application vs. foliar application, crop and cultural practice, pesticide biological properties (crop selectivity, transport), and economics. 

Brazzain. Polypeptide of 54 amino acids, Mr 6473, from the west African tree Pentadiplandra brazzeana (llliaceae). In a 2% solution it is 2000 times sweeter than cane sugar and shows good thermal stability (no loss of activity after 4 h at 80 °C), compare with mo-nellin, thaumatin. B. can also be obtained by synthesis (solid phase method) or biotechnologic ly in genetically engineered Escherichia coli cultures, lit.- Biopolymers 39, 95-101 (1996). PaL WO 9531 547 (publ. 23.11.1995). gen. FEBS Utt. 355,106 ff. (1994). 

Four distinct exo-cellobiohydrolases (1,4-p-o-glucan cellobiohydrolases) have been isolated from cultures of TYichoderma viride They have similar u.v. spectra, amino-acid and amino-sugar compositions, thermal stabilities, molecular weights, specific activities, and COjH-terminal residues, but have different contents and compositions of hexoses. 

The levels of a-D-mannosidase activity in skin fibroblasts from cases of cystic fibrosis and controls have been compared. The effects of pH, metal ions, and heat have been studied on a-D-mannosidase from normal and mannosidosis fibroblasts and in culture medium derived from these. The results showed that enzymes secreted from mannosidosis fibroblasts behaved identically to the enzymes present in culture medium from normal fibroblasts. The implication of this finding was discussed. Two acidic forms of a-D-mannosidase activity, A and B have been separated and characterized from fibroblasts from controls and patients with mannosidosis. In normal cells, A and B differ in adsorption on DEAE-cellulose, electrophoretic mobility, stability at 70 °C, and resistance to freezing at — 20 °C, In five of six mutant cell lines, A and B both exhibited altered K s for artificial substrates, and decreased thermal stability. Zn had no effect on A or B in mutant or normal cells. In contrast, Co + slightly inhibited B in normal cells but markedly enhanced the activity of B in mutant cells. It was concluded that the mutation in mannosidosis results... 

For methyl-methan-sulphonate besides confirming its already known actions (that is methylation of the bases, formation of labile apur-inic sites and therefore intrastrand breakage (see data of thermal stability and viscosity) that are at the basis of its genotoxicity (18), we can add that in our experimental conditions the breakage formation is more evident in direct treatment of DNA than adding the compound to cell cultures. 

---