1 research outputs found
3D-Membrane Stacks on Supported Membranes Composed of Diatom Lipids Induced by Long-Chain Polyamines
Long-chain polyamines
(LCPAs) are intimately involved in the biomineralization
process of diatoms taking place in silica deposition vesicles being
acidic compartments surrounded by a lipid bilayer. Here, we addressed
the question whether and how LCPAs interact with lipid membranes composed
of glycerophospholipids and glyceroglycolipids mimicking
the membranes of diatoms and higher plants. Solid supported lipid
bilayers and monolayers containing the three major components that
are unique in diatoms and higher plants, i.e., monogalactosyldiacylglycerol
(MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol
(SQDG), were prepared by spreading small unilamellar vesicles. The
integrity of the membranes was investigated by fluorescence microscopy
and atomic force microscopy showing continuous flat bilayers and monolayers
with small protrusions on top of the membrane. The addition of a synthetic
polyamine composed of 13 amine groups separated by a propyl spacer
(C3N13) results in flat but three-dimensional membrane stacks within
minutes. The membrane stacks are connected with the underlying membrane
as verified by fluorescence recovery after photobleaching experiments.
Membrane stack formation was found to be independent of the lipid
composition; i.e., neither glyceroglycolipids nor negatively charged
lipids were required. However, the formation process was strongly
dependent on the chain length of the polyamine. Whereas short polyamines
such as the naturally occurring spermidine, spermine, and the synthetic
polyamines C3N4 and C3N5 do not induce stack formation, those containing
seven and more amine groups (C3N7, C3N13, and C3N18) do form membrane
stacks. The observed stack formation might have implications for the
stability and expansion of the silica deposition vesicle during valve
and girdle band formation in diatoms