Conjugation of native membranes via linear oligo-amines

[Display omitted] •Oligo-amines with +3 to +6 positive charges efficiently conjugate lipid bilayers.•Conjugation did not cause any significant denaturation of the two membrane proteins studied.•Membrane conjugation is fully reversible upon addition of NaCl.•Membrane conjugation can be achieved between pH 2.5 to pH 7.•Membrane conjugation is achieved in the absence of polymers (e.g. PEGs) or metals (e.g. Ca2+). We report the first observation of an efficient, native membrane conjugation mechanism via positively charged, linear oligo-amines. Clustering of membrane fragments relies on electrostatic interactions between the net negative charge of the membranes and the positively charged, water-soluble mediators. This conjugation principle is demonstrated with two different bacterial membranes in which are embedded either the intrinsic membrane protein (MP) bacteriorhodopsin (bR) or the more recently identified xanthorhodopsin (XR). As determined by their characteristic UV–vis absorption spectra and by circular dichroism, the MPs are not significantly perturbed by the oligo-amines carrying from +3 to +6 positive charges. Light microscopy and scanning electron microscope (SEM) imaging provide direct evidence for membrane conjugation. Process efficiency was found to be correlated with the net charge of the oligo-amine used. Membrane conjugation is accomplished within a wide range of pH values (7−2.5); is reversed by NaCl; and does not require the presence of a precipitant (e.g. PEG) nor Ca2+ ions. Some evidence for bilayer fusion is also observed, but only in the presence of the +6 oligo-amine analog.