Lipid Membrane Reorganization Induced by Chemical Recognition

Abstract

Nanoscale structural reorganization of a lipid bilayer membrane induced by a chemical recognition event has been imaged using in situ atomic force microscopy (AFM). Supported lipid bilayers, composed of distearylphosphatidylcholine (DSPC) and a synthetic lipid functionalized with a Cu(2+) receptor, phase-separate into nanoscale domains that are distinguishable by the 9 A height difference between the two molecules. Upon binding of Cu(2+) the electrostatic nature of the receptor changes, causing a dispersion of the receptor molecules and subsequent shrinking of the structural features defined by the receptors in the membrane. Complete reversibility of the process was demonstrated through the removal of metal ions with EDTA.

In Situ Scanning Probe Microscopy Studies of Tetanus Toxin-Membrane Interactions

“…We note that the TIRFM and AFM data sets are not perfectly correlated. This is likely a consequence of a nonuniform distribution of the GT 1 B receptor in the fluid phase of the supported bilayer and hence, the distribution of the FITC-Tet C molecules bound to G T1b (49,50). We also cannot discount the possibility that the dynamics of the lipid bilayer may be better resolved on TIRFM timescales rather than on AFM imaging timescales (33).…”

Supramolecular Chemistry in the Biomembrane

“…Complete reversibility was shown by removal of the metal ions with ethylenediaminetetraacetic acid (EDTA). This strategy has been successfully demonstrated with iminodiacetic acid 1 as a receptor for Cu 2+ and Fe 3+ , with dithioamide 2 for Hg 2+ , and with [18]crown‐6 3 for Pb 2+ . Notably, the authors found that the binding affinity of the iminodiacetic acid head group in 1 with various metal cations in vesicles paralleled the affinity in solution, albeit reduced by a factor of 100–1000 …”

Molecular recognition on the supported and on the air/water interface-spread protein monolayers

“…The same group of researchers had earlier imaged, using the in situ AFM, a nanoscale structured reorganization of a lipid bilayer membrane composed of distearyl phosphatidyl choline (DSPC) and a synthetic lipid functionalized with a Cu 2+ receptor (pyrenenoyl steryl-glycero-imidodiacetic acid) upon binding Cu 2+ . The observed dispersion of the receptor molecules in the membrane was reversible through the removal of metal ions with EDTA [48]. The in situ recognition of hydrogen bonding [49], avidin-biotin pairs [50], antibody-antigen pairs [51] and DNA strands [52] with AFM by probe-surface adhesion measurements and topography imagery has been shown to be a powerful tool to locate specific molecular interaction with a sensitivity to single molecular bonding forces.…”