Knowing the topology and location of protein segments at water-membrane interfaces is critical for rationalizing their biological functions, but their characterization is challenging under physiological conditions. Here, we present a novel spectroscopic approach by employing the hydration dynamics gradient found across the liposomal bilayer as a high-resolution molecular ruler for determining the topology, immersion depth, and orientation of protein segments at water-membrane interfaces. This is achieved through the site-specific quantification of translational diffusion of hydration water using an emerging tool, 1H Overhauser dynamic nuclear polarization (ODNP) amplified-NMR relaxometry. We will present ODNP and electron paramagnetic resonance (EPR) studies of the lipid membrane-bound form of a-synuclein (aS), the assembly of the seven a-helix trans-membrane protein, proteorhodopsin (PR), and the conformational changes as triggered by the light-activation of PR. Remarkably, ODNP can reveal previously unresolvable structure and location of protein segments well above the lipid phosphate, whose structure and dynamics critically contribute to the understanding of the functional versatility of membrane proteins. Furthermore, ODNP reveals that different lipid constituents, cholesterol, osmolytes and Hofmeister ions directly and sensitively modulate the characteristic lipid membrane hydration landscape that can be rationalized to modulate the adhesion potential between the lipid membrane surface and biological constituents.

Hydration dynamics to probe protein structure, assembly, and adhesion at lipid membrane interfaces

248th National Meeting (2014)

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