An organic solvent and surfactant stable α-amylase was obtained from soybean seeds. The direct and indirect effect of various organic solvents (non-polar, polar protic, and polar aprotic) and surfactants on the activity and stability of free enzyme was determined. The enzyme showed a very high catalytic efficiency and stabilization against most of the organic solvents and surfactants tested, except for few. Those organic solvents and surfactants (like chloroform, dimethyl formamide, n-butanol, and Tween 20), which caused an inhibition in enzyme activity, were used to study their effects on immobilized enzyme. The inhibitory effect was found to be decreased in immobilized enzyme as compared to free enzyme indicating that immobilization imparted stability to the enzyme. Moreover, the possibility of reuse of the enzyme in the presence of the organic solvents and surfactants was increased upon immobilization. The stability of soybean α-amylase towards organic solvents and surfactants shows that it is a potential candidate for use in organic-solvent biocatalysis as well as in detergent industries.
We studied the ability of di-cationic gemini surfactantsdi (amphiphiles), i.e. 1,4-butanediammonium-N,N-dialkyl-N,N,N',N'-tetramethyl bromides (Di-Cm-di-QAS (s = 4), where m = 8,11,13,16 and s = the number of alkyl groups in the spacer) to induce shape alteration, vesiculation, haemolysis and phosphatidylserine exposure in human erythrocytes, and to protect erythrocytes against hypotonic haemolysis. At high sublytic concentrations the Di-Cm-di-QAS (s = 4) amphiphiles rapidly induced echinocytic (spiculated) shapes and a release of exovesicles, mainly in the form of tubes, from the cell surface. Following 60 min incubation erythrocytes were sphero-echinocytic and a few cells with invaginations/endovesicles were observed. No phosphatidylserine exposure was detected. The haemolytic potency increased with an increase of the alkyl chain length. At sublytic concentrations the Di-Cm-di-QAS (s = 4) amphiphiles protected erythrocytes against hypotonic haemolysis. It is suggested that the Di-Cm-di-QAS (s = 4) amphiphiles perturb the membrane in a similar way as single-chain cationic amphiphiles, but that they do not easily translocate to the inner membrane leaflet.
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