Cellular membrane separates the cytosol from the extracellular space and contains the molecules that facilitate transmission of life-sustaining signals exhibiting lateral heterogeneity through the compartmentalization of lipids, proteins, and carbohydrate molecules. Micro-domains of cholesterol and sphingolipid-rich membranes, called lipid rafts, have attracted much attention from their critical roles in cellular processes through the structural organization and the regulation of protein activation, signaling, and pathogenesis/treatment of neurological and psychiatric disorders. Using supported lipid membranes on wedge-shape substrates with alternating positive and negative curvatures, we represent the curvature-mediated asymmetry of lipid raft domains across the membrane leaflets accompanied by glycolipid receptor localization such as GM1 and GT1b. The raft domains initially appear only in membrane leaflets possessing negative curvature. In the presence of the inter-leaflet coupling, they evolve to generate the transverse registry across the membrane bilayer. We show that a human recombinant anti-body rHIgM12, known to be therapeutic in a mouse model of a neurologic disease, is co-localized with the rafts formed at the peaks and valleys of the wedge substrate, indicating that the spatial distribution of its receptor (GT1b) is indeed manifested by the site-specific formation of asymmetric raft domains through the curvature elasticity. Our methodological platform is a powerful tool of clarifying the mechanism for the leaflet asymmetry and lipid sorting in terms of the membrane curvature, the composition, and the receptor presentation.
Optical trapping using nanoapertures in metal films has advanced significantly in recent years, allowing for the trapping of nanoparticles in the single digit nanometer range, including proteins. It has been recognized previously by theoretical studies coaxial that apertures with small gaps in a metal film can provide extremely large trapping potentials for such nanoparticles. However, past approaches to nanofabrication, such as focussed ion beam milling, do not reliably produce sub-10 nm features. Here we demonstrate the use of a combined electron-microscopy and atomic layer deposition approach to reliably fabricate sub-10 nm gaps on the wafer scale.
We achieve trapping of polystyrene nanoparticles and proteins using these apertures. Numerical simulations show the steep trapping potential achieved in a resonantly tuned coaxial structure. The coaxial structures fabricated are also measured to ensure the wavelength of the resonance is close to the trapping laser wavelength.
As nanogap structures are also promising for surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption, our devices can act as a multifunctional platform to integrate single-molecule manipulation and spectroscopic analysis.
We propose a method of optical data storage that exploits the small dimensions of metallic nano-particles
and/or nano-structures to achieve high storage densities. The resonant behavior of these particles (both individual and in
small clusters) in the presence of ultraviolet, visible, and near-infrared light may be used to retrieve pre-recorded
information by far-field spectroscopic optical detection. In plasmonic data storage, a femtosecond laser pulse is focused
to a diffraction-limited spot over a small region of an optical disk containing metallic nano-structures. The digital
information stored in each bit-cell modifies the spectrum of the femtosecond light pulse, which is subsequently detected
in transmission (or reflection) using an optical spectrum analyzer. We present theoretical as well as preliminary
experimental results that confirm the potential of plasmonic nano-structures for high-density optical storage applications.
Large-scale studies of biomolecular interactions required for proteome-level investigations can benefit from a new class of emerging surface plasmon resonance (SPR) sensors: nanohole arrays and surface plasmon (SP) enhanced optical transmission. In this paper we present a real-time, label-free multiplex SPR imaging sensor in a microarray format. The system presented is built around a low-cost microscope with laser illumination, integrated with microfluidics. The specific binding kinetics of biotin and streptavidin are measured from several sensing elements simultaneously, demonstrating the feasibility of using nanohole arrays as a high-throughput SPR microarray sensor.
Conference Committee Involvement (1)
Plasmonics in Biology and Medicine XVI
3 February 2019 | San Francisco, California, United States