Solvent tolerance hydrophobicity

The MAbs and EIA we have developed provide a means of detecting avermectins at the level of sensitivity now possible with HPLC and gas chromatography. The EIA employs standard methods, and it is stable, reproducible, and economical. The solvent tolerance exhibited by the MAbs makes the assay compatible with methods for recovering residues of these very hydrophobic compounds. Monoclonal antibodies have the well-known advantages of defined affinity, specificity, and potentially infinite supply. The IgGi subclass of all of the avermectin MAbs makes them easy to purify to near-homogeneity by well-documented methods. This could facilitate tests of their usefulness in other immunoassay formats. 

Unlike Gram-positive bacteria, Gram-negative bacteria such as Pseudomonas have an outer membrane. The outer membrane has been shown to play a role in the protection of the cell from solvent toxicity. Ions such as Mg or Ca stabilize the organization of the outer membrane and contribute to solvent tolerance. Low cell surface hydrophobicity caused by changes in the lipopolysaccharide (LPS) content has been reported to serve as a defensive mechanism. " It has also been reported that the porins which are embedded in the outer membrane are relevant to solvent tolerance. ... 

Hydrolysis of substrates is performed in water, buffered aqueous solutions or biphasic mixtures of water and an organic solvent. Hydrolases tolerate low levels of polar organic solvents such as DMSO, DMF, and acetone in aqueous media. These cosolvents help to dissolve hydrophobic substrates. Although most hydrolases require soluble substrates, lipases display weak activity on soluble compounds in aqueous solutions. Their activity markedly increases when the substrate reaches the critical micellar concentration where it forms a second phase. This interfacial activation at the lipid-water interface has been explained by the presence of a... 

Reversible, non-competitive inhibition of polymerase is also afforded by a series of N-benzoyl pyrrolidines. Substitution on the benzoyl moiety with a para-trifluoromethyl group is optimal in this series. Bulky, hydrophobic groups at the 2-position of the pyrrolidine ring increase activity, and the 5-position tolerates a wide range of substituents, indicative of a solvent exposed portion of the inhibitor. Compound (+)-38, containing a 2-thienyl moiety at the 5-position, has an IC50 of 190 nM in the enzyme assay while its enantiomer is almost 100-fold less active [83]. 

Immobilisation of an Acetobacter aceti strain in calcium alginate resulted in improvement of the operational stability, substrate tolerance and specific activity of the cells and 23 g phenylacetic acid was produced within 9 days of fed-batch cultivation in an airlift bioreactor [133]. Lyophilised mycelia of Aspergillus oryzae and Rhizopus oryzae have been shown to efficiently catalyse ester formation with phenylacetic acid and phenylpropanoic acid and different short-chain alkanols in organic solvent media owing to their carboxylesterase activities [134, 135] (Scheme 23.8). For instance, in n-heptane with 35 mM acid and 70 mM alcohol, the formation of ethyl acetate and propylphenyl acetate was less effective (60 and 65% conversion yield) than if alcohols with increased chain lengths were used (1-butanol 85%, 3-methyl-l-butanol 86%, 1-pentanol 91%, 1-hexanol 100%). This effect was explained by a higher chemical affinity of the longer-chain alcohols, which are more hydrophobic, to the solvent. 

Large differences in sensitivity toward interfacial inactivation were observed between a-chymotrypsin and Candida rugosa lipase [56]. The lipase was most rapidly inactivated by 1-butanol and tolerated the hydrophobic hydrocarbons quite well, while the opposite was true for a-chymotrypsin. A detailed study of interfacial inactivation by 12 different solvents, all having log P values around 4, revealed... 

Polytetrafluoroethylene (PTFE) (MF only) an extremely hydrophobic membrane, with high tolerance of acids, alkalis, and solvents can be used at temperatures up to 260°C. 

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