D. F. Evans

Spontaneous Vesicles Formed from Hydroxide Surfactants: Evidence from Electron Microscopy

Dialkyldimethylammonium hydroxide surfactants are highly soluble in water and form spontaneous stable vesicles. These vesicles can be grown to size with added acid, and appear to provide an ideal membrane mimetic system for the study of fusion and ion transport. These phenomena are a consequence of strong hydration forces that are not necessarily limited to the hydroxide ions. The forces can be used to design a variety of model systems whose behavior differs from that of systems in which double-chained surfactants form insoluble liquid crystalline phases in water and unstable vesicle suspensions on prolonged sonication.

Video enhanced differential interference contrast microscopy: a new tool for the study of association colloids and prebiotic assemblies

Abstract Progress in our understanding of molecular forces enables some rules to be formulated for design of surfactant systems. Competition between electrostatic and hydration head group forces, hydrocarbon chain interactions, associated oil penetrability, and interaggregate forces can be put to work to dictate prescribed curvature and other properties of association colloids. Such aggregates can be visualized directly and quickly by a new light microscopy technique. The power of this technique which complements QELS, neutron scattering, electron microscopy, and other methods is illustrated by a study on several surfactant-water systems.

Interaction of amphiphilic aggregates with cells of the immune system

The cell membrane - its composition, integrity, and function - is central to many biological processes, ranging from cell adherence and contact inhibition, to the cell-cell interactions involved in many immunological responses. While great progress has been made in understanding the biological and biochemical mechanisms responsible for cellular functions and interactions, similar strides have been taken in dissecting and quantifying the chemical and physical forces that govern the shape and structure of membranes(1). Here, Robert Ashman and his colleagues discuss principles derived from theory and experimentation in colloid and surface chemistry, the insights they may provide into the mechanisms of membrane function, and the means by which these membrane functions may be modified.

Vesicle and micelle formation in a double-chained anionic surfactant: Counterion complexation by a macrocyclic ligand

Abstract Addition of the macrocyclic sodium complexing agent cryptand [2.2.2] to aqueous solutions of sodium 8-phenyl-n-hexadecyl-p-sulfonate (Texas No. 1) causes a dramatic decrease in aggregate size, with the formation of unilamellar vesicles and micelles at cryptand to surfactant mole ratios exceeding 0.6. The results can be explained in terms of an increased head group repulsion due to the removal of the Na+ counterion from the aggregate surface.

Rapid characterization of colloidal systems by video-enhanced light microscopy

Abstract A new microscopy technique, Video-Enhanced Contrast-Differential Interference Contrast Microscopy, is used to characterize colloidal systems by direct visualization on a TV screen. The method allows rapid characterization of colloidal surfactant aggregates and other macromolecules in the size range 500–10,000 A and offers a number of advantages over classical methods.