Membrane permeabilizing action

The titanium compounds CpTiCl3, Cp2TiCl2, and CH2(C5H4)2TiCl2 have been used as catalysts for the diastereoselective epoxidation of allylic alcohols.1932 [TiCp2(LL)]2+ (LL = 1,10-phenantroline, 2,2 -bipyridine) (Scheme 758) have been studied in order to determine the importance of the ancillary chelated ligands versus the metal center for the membrane-permeabilizing action and their effects on lipid epoxidation reactions.1933... 

The mode of action of amphidinols can be accoimted for by their membrane permeabilizing actions. The polyene and polyhydroxy moieties play important roles in binding lipid bilayer membrane and in forming ion-permeable pore/lesion across membrane. The central part involving two tetrahydropyran rings comprises a large hydrophilic part with a hairpin conformation and the polyolefin moiety penetrates deep into membrane. The size of the pore formed in the membrane is influenced by the polyhydroxy region [ 123]. 

Some of the compounds have been evaluated for their ability to induce mitochondrial membrane permeabilization, which is believed to play a fundamental role in the regulation of programmed cell apoptosis. The effects observed are not in line with a conventional model of action related to the accumulation of the lipophilic compounds in the cell, and further studies are necessary.281... 

Busse H-J, Wostmann C, Bakker EP The bactericidal action of streptomycin Membrane permeabilization caused by the insertion of mistranslated proteins into the cytoplasmic membrane of Escherichia coli and subsequent caging of the antibiotic inside the cells due to degradation of these proteins. J Gen Microbiol 1992 138 551. [PMID 1375623]... 

Another study tested to what extent antibiotics affect the membrane integrity of Escherichia coli and hence inhibit the ChemChrome V6 labelhng. Inhibition of the fluorescent staining was only observed for membrane permeabilizing antibiotics, even at concentrations below the MIC but not for antibiotics with other mechanisms of action e. g. 6-lactams. As an application, colistin could be determined in milk by measuring the decrease in the number of labelled Escherichia coli cells relative to the initial number that had been added to the milk (D Haese and Nelis 2000). 

Helander, I. M., Latva, K. K., and Lounatmaa, K. 1998. Permeabilizing action of polyethyleneknine on Salmonella typhimurium involves disruption ot the outer membrane and interactions with Hpopolysac-charide. Microbiology, 144 385-390. 

DSC has also been used to study the effects of a wide variety of antimicrobial peptides on the thermotropic phase behavior of different lipid bilayers. These studies again are highly biologically relevant because the primary mode of action of most antimicrobial peptides is the perturbation and permeabilization of the lipid bilayers of the target membrane, and these agents have considerable promise as antibiotics, especially to treat multiple dmg-resistant pathogenic bacteria. Again, the reader should consult recent reviews for more information on this topic (30, 31). 

Bhakdi S, Greulich S, Muhly M etal. (1989) Potent leukocidal action of Escherichia coli hemolysin mediated by permeabilization of target cell membranes. In J Exp Med 169 737-754. 

Defensins are variably cationic, relatively arginine-rich, nonglycosylated peptides comprised of 29-34 amino acid residues. Human (HNP-1) and rabbit (NP-5) defensins have been studied by NMR techniques and showed that they are rich in beta sheet structure. Although both types of defensins permeabilize the outer membrane of E. coli [31], they differ from other peptides with similar action but rich in alpha helices such as magainin, mellitin and cecropin. 

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