Quantifying the effects of melittin on liposomes

Abstract

Melittin, the soluble peptide of bee venom, has been demonstrated to induce lysis of phospholipid liposomes. We have investigated the dependence of the lytic activity of melittin on lipid composition. The lysis of liposomes, measured by following their mass and dimensions when immobilised on a solid substrate, was close to zero when the negatively charged lipids phosphatidyl glycerol or phosphatidyl serine were used as the phospholipid component of the liposome. Whilst there was significant binding of melittin to the liposomes, there was little net change in their diameter with melittin binding reversed upon salt injection. For the zwitterionic phosphatidyl choline the lytic ability of melittin is dependent on the degree of acyl chain unsaturation, with melittin able to induce lysis of liposomes in the liquid crystalline state, whilst those in the gel state showed strong resistance to lysis. By directly measuring the dimensions and mass changes of liposomes on exposure to melittin using Dual Polarisation Interferometry, rather than following the florescence of entrapped dyes we attained further information about the initial stages of melittin binding to liposomes.

On the Mechanism of Pore Formation by Melittin

“…This asymmetric accumulation would lead to membrane thinning and nonselective membrane damage (14, 30 -33). At very high concentrations of melittin, the peptide might disrupt PC membranes in a similar fashion as PG membranes (18,34). However, these concentrations are much higher than needed for pore formation (e.g.…”

Identification of a Region That Assists Membrane Insertion and Translocation of the Catalytic Domain of Bordetella pertussis CyaA Toxin

“…We therefore explored the membrane binding process under steady-state conditions (i.e. without any fractionation steps) by using DPI, a relevant technique for the study of interactions of proteins with planar single lipid bilayers, which are spontaneously formed on the silicon oxynitride surface of the DPI analytical channels (43)(44)(45)(46). DPI uses polarized light from a laser passing down stacked waveguides to monitor changes in the thickness and mass of immobilized molecules through changes in the resulting optical interference pattern.…”

Direct and label-free monitoring oligonucleotide immobilization, non-specific binding and DNA biorecognition

“…All chemical and photochemical methods gave rise to a probe density 19 immobilization in the order of 1.0-2.5·10 other chemistries. The obtained data suggest that DNA strands are anchored in a different 21 conformation depending on the immobilization method employed. In order to avoid non-22 specific binding of target molecules, ethanolamine and inert proteins were assayed, and 23 successful results were obtained when using small size proteins such as gelatine.…”

“…14 Applications of DPI can be found in any area where microscopic surface properties need 15 to be monitored, provided that silicon-based chips act as a supports. Interesting reports are the 16 monitoring of lipids [18], polyelectrolytes [19] and other multilayers [20], events happening in 17 liposomes [21], as well as the study of induced conformational changes in proteins [22] Silicon oxynitride chips (FB 100, Farfield, UK) were used for measurements. The sensor 7 surface has two fluidic interfaces, 2 µL dead volume each, named channel 1 and channel 3, with 8 an additional waveguide reference area, channel 2, having a dielectric cover with constant 9 refractive index.…”