Study of permeation and blocker binding in TMEM16A calcium-activated chloride channels

We studied the effects of mutations of positively charged amino acid residues in the pore of X. tropicalis TMEM16A calcium-activated chloride channels: K613E, K628E, K630E; R646E and R761E. The activation and deactivation kinetics were not affected, and only K613E showed a lower current density. K628E and R761E affect anion selectivity without affecting Na⁺ permeation, whereas K613E, R646E and the double mutant K613E + R646E affect anion selectivity and permeability to Na⁺. Furthermore, altered blockade by the chloride channel blockers anthracene-9-carboxylic acid (A-9-C), 4, 4''-Diisothiocyano-2,2''-stilbenedisulfonic acid (DIDS) and T16inh-A01 was observed. These results suggest the existence of 2 binding sites for anions within the pore at electrical distances of 0.3 and 0.5. These sites are also relevant for anion permeation and blockade.     

Neutralization of the activity of eight disinfectants by organic matter

The effect of organic matter on the activity of eight disinfectants was evaluated. Three types of interfering substrates (whole milk powder, dried beef blood and fish meal) were tested according to the method of Whitmore and Miner adapted to the AOAC use-dilution method. Glutaraldehyde and to a certain extent, chlorhexidine acetate and the amphoteric surfactant kept their disinfecting activity after contact with high concentrations of organic matter. The quaternary ammonium compound as well as the quaternary ammonium-glutaraldehyde complex were more readily neutralized whereas anionic acid, iodophor and sodium hypochlorite did not tolerate the presence of organic matter. The neutralizing activity of powders was correlated to their solubility and composition.