Differential modes of incorporation of probe molecules in micelles and in bilayer vesicles

Abstract

Spin-labeled fatty acids, fluorescent amphiphiles, and similar bifunctional probe molecules are used to monitor the interior of micelles, bilayers, and biomembranes. It is usually assumed that the probe moiety of these molecules is inserted in the interior of the host assembly, an assumption that needs to be verified. We show here that these molecules are incorporated in different ways in spherical micelles, rodlike micelles, and bilayer assemblies. Looping back of the probe molecule and the consequent placing of the probe moiety in the interfacial region appear to be common in spherical micelles whereas the same molecule is incorporated in a straight-chain configuration in bilayer vesicles. The reason behind this differential incorporation appears to be related to the surface area to volume ratio of the host assemblies and their intermolecular packing differences. Micelles promote self-coiling of these molecules while membranes appear not to do so.

Exploring membrane organization and dynamics by the wavelength-selective fluorescence approach

“…It is fairly well established that practically all types of molecules have a surface-seeking tendency in micelles (due to very large surface area to volume ratio) and that the interfacial region is the preferred site for solubilization, even for hydrophobic molecules (Mukerjee and Cardinal, 1978;Ganesh et al, 1982;Shobha and Balasubramanian, 1986;Shobha et al, 1989). The suitability of micellar systems for studies employing wavelength-selective fluorescence was therefore tested using the interfacial fluorescence probe NBD-PE .…”

A novel method for dissolution and stabilization of non‐mulberry silk gland protein fibroin using anionic surfactant sodium dodecyl sulfate

“…Surfactants are soluble amphiphiles and above a critical concentration level, called the critical micelle concentration (CMC), surfactants self associate to form stable non-covalent aggregates called micelles (Tanford, 1978). It is well known that molecules have a surface-seeking tendency in micelles, the interfacial region being the preferred site for solubilization, even for hydrophobic molecules (Shobha et al, 1989). The success of anionic surfactants in solubilization has been attributed to their ability to disrupt the hydrogen bonds present in b-sheet structures (D'Auria et al, 2001).…”

Effect of micellar charge on the conformation and dynamics of melittin

“…The organization and dynamics of micellar environments, namely the core, the interface, and the immediate layers of water on the interface, have been investigated using experimental (Sarkar et al 1996;Maiti et al 1997;Rawat et al 1997;Rawat and Chattopadhyay 1999) and theoretical (MacKerell 1995) approaches. It is fairly well established now that practically all types of molecule have a surface-seeking tendency in micelles (due to very large surface area to volume ratio) and that the interfacial region is the preferred site for solubilization, even for hydrophobic molecules (Shobha et al 1989).…”