3D-Membrane Stacks on Supported Membranes Composed of Diatom Lipids Induced by Long-Chain Polyamines

Abstract

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.

Multilayered Lipid Membrane Stacks for Biocatalysis Using Membrane Enzymes

“…Such similar rates of diffusion imply that the two membranes in the double membrane patches are interconnected via a lipid phase. Similar patches of membrane stacks that are connected to an underlying bilayer have previously been observed after the addition of lipopolysaccharide and, very recently, long chain polyamines …”

Correlated fluorescence quenching and topographic mapping of Light-Harvesting Complex II within surface-assembled aggregates and lipid bilayers

“…Several preliminary experiments were performed to optimize the lipid composition and buffer conditions for the thylakoid liposomes in order to achieve a high-quality, contiguous supported lipid bilayer comparable to those of 100% DOPC. After initial tests with either the native mixture of thylakoid lipids or 100% DGDG were unsuccessful, 25% DOPC was incorporated into the thylakoid lipid mixture to promote formation of planar bilayers [ 44 ] which are amenable to surface-based work. This gave a final adapted mixture comprised 35% MGDG, 20% DGDG, 12% SQDG, 8% Soy PG, 25% DOPC (w/w%).…”

“…Proteoliposomes containing LHCII and thylakoid lipids are stable due to the inherent curvature of a vesicle and are becoming the standard for in vitro studies of NPQ in solution [ 27 , 40 , 41 , 43 , 66 , 75 , 76 ], however, proteoliposomes are not conducive to high resolution imaging. Few studies have achieved the formation of planar bilayers of thylakoid lipids on a solid support as required for high resolution microscopy, due to the high curvature of MGDG [ 44 ]. We have demonstrated that it is possible to generate membranes including LHCII with thylakoid lipid mixtures on solid supports, and found similar protein rearrangements and similar intermediate levels of quenching as when using DOPC phospholipids ( Fig.…”

“…For the model phospholipid system the lipids used were 100% DOPC. For the model thylakoid system, a mixture similar to those previously described as natural ratios [ 43 ] was adapted for use with planar surfaces as described by Gräb and co-workers [ 44 ], comprising: 35% MGDG, 20% DGDG, 12% SQDG, 8% Soy PG, 25% DOPC (w/v%), for further methodological details see the Supplementary information. Lipids were dissolved in 5:1 chloroform: methanol and mixed to the desired ratios in glass vials in and dried under nitrogen flow for 30 min and then in a vacuum desiccator overnight.…”

Continuum modelling of structure formation of biosilica patterns in diatoms

“…Boundary interaction. A recent experimental study [33] focused on the influence of the boundary of the SDV on the aggregation of biomolecules. In particular, the interaction of long-chain polyamines with lipid membranes was analyzed.…”