Pore-forming Material Research Articles

Pore-forming peptide of pathogenic Entamoeba histolytica.

A polypeptide that causes pore formation in target-cell membranes is implicated in the potent cytolytic activity of pathogenic Entamoeba histolytica. Pore-forming material was purified to apparent homogeneity by a multistep procedure, and its analysis by NaDodSO4/PAGE revealed one peptide of 4-5 kDa under nonreducing or under reducing conditions. Pore-forming activity was measured by depolarization of liposome membrane potential and was found to be optimally expressed at low pH. Active material preferentially inserted into negatively charged lipid vesicles. Treatment of purified amoeba peptide in solution or bound to liposomes with glutaraldehyde revealed oligomers upon NaDodSO4/PAGE, suggesting functionally relevant peptide-peptide interactions. The NH2-terminal amino acid sequence of the amoeba peptide was determined by protein sequencing and revealed a structural similarity to melittin, the membranolytic peptide of bee venom.

A gradient matrix system as a controlled release device. Release from a slab model system

The in vitro release of a model drug compound, acetaminophen, from ethylcellulose matrices was studied. The systems were prepared by spraying a solution of acetaminophen and polymer on to flat tablet surfaces in a spray box. The release from the slabs showed a square root of time dependency for systems containing up to 75% of acetaminophen by weight (relative to weight of ethylcellulose). Addition of a pore-forming material, xylitol, increased the release rate of acetaminophen. Linear release rates were observed by applying a positive concentration gradient of acetaminophen in the direction of the core of the matrix. Xylitol was added with an inverse concentration gradient. Formation of a barrier layer at the outer surface of the device was thus avoided.

Properties of the capillary structure of copper powder

The properties of capillary structures of type PMS copper powder of different particle size composition obtained by sintering of freely poured material and by pressing with and without a poreforming material with subsequent sintering were investigated experimentally. It was shown that the capillary structures obtained by pressing with a pore-forming material possess uniformly high transport properties and a good quality of interparticle contacts.

Characterization of a membrane pore-forming protein from Entamoeba histolytica.

We describe the partial purification and characterization of a pore-forming material (PEM) from Entamoeba histolytica. The formation of ion channels by PFM was examined in three systems. (a) PFM depolarizes J774 macrophages and mouse spleen lymphocytes as measured by [3H]TPP+ uptake. (b) PFM induces rapid monovalent cation flux across the membrane of phosphatidylcholine-cholesterol vesicles. (c) PFM confers a voltage-dependent conductance to artificial planar bilayers, which is resolved as a summation of opening of individually conducting steps of 67 pS in 0.1 M KCl. Monomers of PFM are functional; however, a preferential aggregation occurs in the planar bilayer. Activity is pronase, trypsin, and heat sensitive and is stable between pH 5-8. PFM is not secreted by unstimulated amoebae but after exposure to the calcium ionophore A23187, concanavalin A, and E. coli lipopolysaccharide, 5-10% of the total cell content of PFM is released into the medium within 5-10 min. High-performance gel filtration results in an approximately 1,000-fold purification of PFM and gives an Mr of 30,000. This protein may play a role in the cytotoxicity mediated by E. histolytica.