Anette Strömberg

Molecular engineering: Networks of nanotubes and containers

We have constructed complex two-dimensional microscopic networks of phospholipid bilayer nanotubes and containers in which we are able to control the connectivity, container size, nanotube length, and angle between the nanotube extensions. Containers within these networks can be chemically differentiated and materials successfully routed between two containers connected by a common nanotube. These networks will enable model systems to be devised for studying confined biochemical reactions, intracellular transport phenomena and chemical computations.

Manipulating the biochemical nanoenvironment around single molecules contained within vesicles

A method to study single-molecule reactions confined in a biomimetic container is described. The technique combines rapid vesicle preparation, optical trapping and fluorescence confocal microscopy for performing simultaneous single-vesicle trapping and single-molecule detection experiments. The collisional environment between a single enzyme and substrate inside a vesicle is characterized by a Brownian dynamics Monte Carlo simulation. q 1999 Elsevier Science B.V. All rights reserved.

Confining and Probing Single Molecules in Synthetic Liposomes

As organisms, we are amazingly complex living laboratories. As we move, breathe, think, and eat, seemingly endless chemical reactions and interactions occur inside us. The test tubes, beakers, and flasks used to separate and selectively mix the myriad of reactants involved are cells, vesicles, and organelles. Taking the analogy further, whereas chemists typically mix chemicals milliliters or more in volume, biological systems carry out their biochemistry in containers that are femtoliters or less in volume. As researchers we assume, with good reason, that the material surfaces of our laboratory test tubes do not substantially affect the kinetics we measure. This assumption might not hold were we to shrink our containers to the femtoliter scale. At such a small scale, collision rates between reactants and their container walls become significant [1], and the inner surface, particularly in biological containers, is chemically complex. The bilayers of cells and organelles are composed of a variety of lipids. These varieties assemble into domains [2] in a process partly controlled by the transmembrane proteins in them [3]. Cellular and organellar control of chemical reactions may thus come, in part, from alterations in the composition and arrangement of the molecular species making up the bilayer membrane [4]. How do systematic alterations to the bilayer composition of a liposome alter the kinetics of reactions within the liposome interior? We may find that the potential physiological significance of lipid domains within bilayers to the kinetics of in-plane reactions [5] (i.e., for proteins and other molecules moving within the bilayer) has applications to molecules within liposomes that interact with the inner bilayer surface.