Kinetics of vesicle formation

It is then of interest to investigate how the final salt concentration influences the kinetics of vesicle formation. The increase in salt concentration provides the driving force for the reaction, and it is apparent that the larger the salt jump, the greater the tendency will be to form vesicles, which we would expect to be reflected in the observed rates. It should be... 

Thermodynamics and Kinetics of Spontaneous Formation and Breakdown of Vesicles in Aqueous Media ... 

The kinetics of vesicle fusion, followed by monitoring the position of the minimum of the SPR reflectivity curves, depends on the composition and molecular shape ofthe vesicular lipids and on the nature ofthe substrate. As a rule, bilayer formation by vesicle unrolling onto a hydrophilic surface is faster than monolayer formation by vesicle fusion onto a hydrophobic surface. This is probably due to the fact that the processes involved in forming a planar bilayer starting from a vesicular bilayer are considerably less complex than those involved in forming a planar monolayer [8, 9]. 

Many studies investigated the kinetics of the process of vesicle break up upon addition of a micelle-forming surfactant and the reverse process of vesicle formation when a system containing a micelle-forming surfactant is... 

The stopped-flow method has been used to study the kinetics of micelle formation/breakdown in surfactant solutions (see Chapter 3), of the exchange process in micellar solutions of amphiphihc block copolymers (see Chapter 4, Sections IV and V), and also of colhsions between droplets in microemulsions (see Chapter 5, Section VI.F). It has been also used to study the kinetics of the vesicle-to-micelle transformation (see Chapter 6) and of various types of chemical reactions performed in micelles or microemulsion droplets (see Chapter 10). The stopped-flow method has also been used to study the rate of dissolution of oil or water in microemrdsions (see Chapter 5, Section VII.C). In such studies the syringe that contains the oil or water to be solubilized is of a much smaller diameter than that containing the microemulsion. 

Theoretical aspects relating to vesicle formation have been addressed in a series of papers by Lasic, and his papers should be consulted for details since the main emphasis in this chapter is on experimental work. Indeed, until recently there have been very few kinetic studies of vesicle formation and/or breakdown, but the field is now being extensively investigated. 

The kinetic control of vesicle transport, from vesicle budding in the Golgi (and other origins) to fusion of the vesicle with the target membrane, is currently a vigorous area of research. The formation of COP-coated vesicles... 

New glycolipids have to be synthesized to get further insights into liquid crystal properties (mainly lyotropic liquid crystals), surfactant properties (useful in the extraction of membrane proteins), and factors that govern vesicle formation, stability and tightness. New techniques have to be perfected in order to allow to make precise measurements of thermodynamic and kinetic parameters of binding in 3D-systems and to refine those already avalaible with 2D-arrays. Furthermore, molecular mechanics calculations should also be improved to afford a better modeling of the conformations of carbohydrates at interfaces, in relation with physical measurements such as NMR. 

In this article, some of the fundamental kinetic ideas relating to spontaneous vesicle formation and breakdown by surfactants in aqueous media are described. The work is related to liposome formation and breakdown using phospholipids, and the induced rupture of membranes. 

We have studied in this contribution the kinetics of formation and breakdown of vesicles on changing the salt and surfactant concentration with a view to elucidating the mechanism of the reaction., and the intermediate structures which are likely to be involved. 

A typical kinetic profile for the reaction leading to spontaneous formation of vesicles is shown in Fig. 19.10, both for 6-SLABS and 7-SLABS. It can be seen that the kinetics are relatively simple in this configuration and the formation of vesicles occurs on the time scale of about a minute. 

Beyond the thermodynamic control, the kinetics of chain rearrangement can dramatically influence the phase behavior leading to kinetically trapped structures, which do not necessarily correspond to an absolute free energy minimum of the system. Thus, the formation of block copolymer vesicles, from a kinetic point of view, can be a result of a transition from rod-like aggregates via flat, nonclosed lamellar structures. The kinetics of such transitions has been explored in [8], The transition steps are represented as follows ... 

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