Coupling of the Orientations of Thermotropic Liquid Crystals to Protein Binding Events at Lipid-Decorated Interfaces

Abstract

We report a study of the interactions of proteins with monolayers of phospholipids (D/L-alpha-dipalmitoyl phosphatidylcholine and L-alpha-dilauroyl phosphatidylcholine) spontaneously assembled at an interface between an aqueous phase and a 20-microm-thick film of a nematic liquid crystal (4'-pentyl-4-cyanobiphenyl). Because the orientation of the liquid crystal is coupled to the organization of the lipids, specific interactions between phospholipase A2 and the lipids (binding and/or hydrolysis) that lead to reorganization of the lipids are optically reported (using polarized light) as dynamic orientational transitions in the liquid crystal. In contrast, nonspecific interactions between proteins such as albumin, lysozyme, and cytochrome-c and the lipid-laden interface of the liquid crystal are not reported as orientational transitions in the liquid crystals. Concurrent epifluorescence and polarized light imaging of labeled lipids and proteins at the aqueous-liquid crystal interface demonstrate that spatially patterned orientations of the liquid crystals observed during specific binding of phospholipase A2 to the interface, as well as during the subsequent hydrolysis of lipids by phospholipase A2, reflect the lateral organization (micrometer-sized domains) of the proteins and lipids, respectively, at the aqueous-liquid crystal interface.

Liquid Crystal Emulsions as the Basis of Biological Sensors for the Optical Detection of Bacteria and Viruses

“…Recent reports have demonstrated that it is also possible to tailor the interfaces of LCs at aqueous interfaces in ways that lead to changes in the orientational order of the LCs. For example, recent studies on thin films of supported LCs have demonstrated that orientational ordering transitions in LCs can be triggered by the presence of lipids, [1,8,13,14] surfactants, [15][16][17] proteins, [3,18,19] and viruses. [10,20] These changes in orientational order arise from coupling between the aliphatic tails of the adsorbed amphiphiles and the mesogens of the LCs.…”

“…The nature and extent of these changes is influenced by the structure of the amphiphiles (e.g., tail length or head group structure) [15,17] or by chemical or physical events in the aqueous phase that disrupt or perturb these assemblies (such as the binding or enzymatic action of a protein). [18,19] Additionally, LC-based reporting offers potential advantages over conventional techniques because it does not require complex instrumentation or labels (enzymatic or fluorescent).…”

Liquid Crystal Enabled Early Stage Detection of Beta Amyloid Formation on Lipid Monolayers

“…In fact, the liquid crystal acts as an amplifi er for molecular binding events. [ 10 ] Note, however, that past research in this area has been limited to reporting the adsorption of biomaterials at LC interfaces, including biological toxin, [ 11 ] proteins, [ 12 ] and stem cells. [ 13 ] In this work we go beyond that, and demonstrate that LCs can serve as faithful reporters of distinct molecular motifs, such as the alpha helices or beta sheets of protein aggregates.…”

Beyond displays: The recent progress of liquid crystals for bio/chemical detections

“…Over incubation for 2 h, a monolayer of L-DLPC was laden at LC-aqueous interface and resulted in a complete anchoring transition from planar to homeotropic alignment ( Figure 5(d)). Aside from lipids [29,30], it has been shown that amphiphilic molecules, such as surfactants [31][32][33][34][35][36][37] and polymers [38][39][40][41] at these interfaces are strongly coupled to the ordering of the LCs, and the presence and organization of these molecules can be reported through changes in the optical appearance of the LCs. It was noted that LCs are fluid-like and possess mobility, combined with liquid crystallinity, assembling biological amphiphiles at the LC-aqueous interface promises a possibility for mimicking cell membrane, which is mobile and composed of a large amount of lipids in liquid crystalline phase.…”