Degradation variable resistance

This paper has provided the reader with an introduction to a class of polymers that show great potential as reverse osmosis membrane materials — poly(aryl ethers). Resistance to degradation and hydrolysis as well as resistance to stress Induced creep make membranes of these polymers particularly attractive. It has been demonstrated that through sulfonation the hydrophilic/hydrophobic, flux/separation, and structural stability characteristics of these membranes can be altered to suit the specific application. It has been Illustrated that the nature of the counter-ion of the sulfonation plays a role in determining performance characteristics. In the preliminary studies reported here, one particular poly(aryl ether) has been studied — the sulfonated derivative of Blsphenol A - polysulfone. This polymer was selected to serve as a model for the development of experimental techniques as well as to permit the investigation of variables... 

Incubation in soils showed that polybrominated biphenyls were resistant to degradation, but were apparently not taken up by plants or leached into groundwater [261]. Commercial formulations of brominated aromatic flame retardants had variable composition some contained highly brominated phenols, but no evidence of contamination with dibenzodioxins and dibenzofurans was found [198]. 

There does not appear to be any significant proteolytic degradation by enzymes in the extracellular fluid in normal human airways and alveoli. However, the presence of peptidases makes absorption of small peptides variable and difficult to predict. Peptidase-resistant peptides generally show better bioavailabilities than other peptides with comparable molecular weights. ° Difference in metabolism and absorption of d and L forms of peptides glycyl-D-phenylalanine and glycyl-L-phenylalanine was demonstrated by Morimoto et al.f The l peptide was subject to metabolism, and it had significant paracellular transport with a smaller transcellular component. In contrast, the... 

Light chains may cause tubular dysfunction, especially of the proximal tubular cells. Characteristically the fight chain variable domain is resistant to degradation by proteases in lysosomes in the tubular cells. The variable domain fragments accumulate in proximal tubular cells, and cfinical features include RTA and phosphate wasting. 

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