Oxovanadates: a novel probe for studying lipid-water interfaces

How water, metabolites and proteins associate and traverse the lipid interface is generally investigated by using probes with spectroscopic handles. Cellular confinement limits the tools of investigation to indirect approaches. Studies of a variety of different probes become important to understand the effects of confinement on chemical reactions and biological function. Confinement of water affects the properties of water and this effect is important for cellular systems. A versatile model system for studying the effect of water confinement on biological processes uses reverse micelles (RMs). Molecular probes are also used to investigate environments that are not readily accessible to direct measurements. Most of the dyes in use contain large hydrophobic chromophores and do not have size and structural flexibility to probe a surface that is both hydrophobic and hydrophilic as common in biological systems. We present the use of vanadium-containing probes for exploration of the fundamental properties of restricted water and lipid interfaces in RMs. The presence of a vanadium atom in these probes provides multiple handles such as chemical shifts, signal linewidth and lifetime experiments in the quadrupolar V-51 nuclei as well in H-1 and C-13 nuclei for investigations. The quadrupolar nuclei have a greater battery of useful spectroscopic parameters and combined with the conventional methods provide multiple handles in one probe. Furthermore, the vanadium-containing probe structure, charge and polarity can be modified for use in various biological settings. Here we introduce the concept and describe a few applications of this approach. (c) 2006 Elsevier SAS. All rights reserved.