supramolecular structure and the strain energy [26]. In addition, most self-assembled
objects are near-equilibrium systems and then evolve slowly with time and with local
variations in the surrounding of the supramolecular structures. These different steps
could explain why the rate of supramolecular structure formation through protein
self-assembly is relatively slow. The final state depends on the equilibrium of
attractive and repulsive interaction between proteins inside the overall structure and
the forces between the supramolecular structures [17]:
– Repartition of attractive and repulsive zones onto the protein surface is responsible
for the shape and size of the supramolecular structure; hence, depending on the
protein system and the physicochemical conditions of the medium, the size (from
nanometre to micrometre) and shape (fibres, spheres, etc.) are able to change.
– Energy and nature of attractive and repulsive interactions between selfassembled proteins control the stability and reversibility of the formed supramolecular structures.
4.1 Oppositely Charged Proteins and Polyelectrolytes
Several recent reviews deal with the fundamental self-assembly between proteins
and natural polyelectrolytes, e.g. DNA and polysaccharides [30, 31, 34, 111]. The
applications in the food sector of protein and polysaccharide complexes and
coacervates are also well covered elsewhere [35, 112]. Given these abundant recent
reviews, this field is deliberately excluded from the present review.
The literature on the interactions and assembly between synthetic polyelectrolytes
and proteins with opposite charges is also abundant (for reviews see [31, 113, 114]).
The initial interactions in these systems involve short-range interactions like van der
Waals and longer-range interactions, especially electrostatic interactions. At the
thermodynamic level, for oppositely charged systems of protein and polyelectrolyte,
interaction and assembly is generally found to be an exothermic process due to
favourable electrostatic interactions [115], although an endothermic process has
been reported for a BSA/polyelectrolyte system [116]. In addition to electrostatic
interactions, the entropic contribution of the release of small counterions and water
molecules has also been reported. For synthetic polyelectrolytes interacting with
proteins, it is postulated that the interaction process is the result of a competition
between the attractive electrostatic interactions between polyelectrolytes and proteins
in one hand, and the polymer characteristics on the other hand. This was modelled by
Muthukumar [117], taking into account the charge densities, size, Debye length and
the molecular weight of involved macromolecules.
Control of these interactions is of importance for the design of a variety of
supramolecular structures with different intrinsic properties. Before considering the
cross-assembly between proteins, we first present some general elements on the
interaction of proteins with linear polyelectrolytes. Some examples published
during the last 10 years on dual systems involving a mixture of protein and
82
S. Bouhallab and T. Croguennec
objects are near-equilibrium systems and then evolve slowly with time and with local
variations in the surrounding of the supramolecular structures. These different steps
could explain why the rate of supramolecular structure formation through protein
self-assembly is relatively slow. The final state depends on the equilibrium of
attractive and repulsive interaction between proteins inside the overall structure and
the forces between the supramolecular structures [17]:
– Repartition of attractive and repulsive zones onto the protein surface is responsible
for the shape and size of the supramolecular structure; hence, depending on the
protein system and the physicochemical conditions of the medium, the size (from
nanometre to micrometre) and shape (fibres, spheres, etc.) are able to change.
– Energy and nature of attractive and repulsive interactions between selfassembled proteins control the stability and reversibility of the formed supramolecular structures.
4.1 Oppositely Charged Proteins and Polyelectrolytes
Several recent reviews deal with the fundamental self-assembly between proteins
and natural polyelectrolytes, e.g. DNA and polysaccharides [30, 31, 34, 111]. The
applications in the food sector of protein and polysaccharide complexes and
coacervates are also well covered elsewhere [35, 112]. Given these abundant recent
reviews, this field is deliberately excluded from the present review.
The literature on the interactions and assembly between synthetic polyelectrolytes
and proteins with opposite charges is also abundant (for reviews see [31, 113, 114]).
The initial interactions in these systems involve short-range interactions like van der
Waals and longer-range interactions, especially electrostatic interactions. At the
thermodynamic level, for oppositely charged systems of protein and polyelectrolyte,
interaction and assembly is generally found to be an exothermic process due to
favourable electrostatic interactions [115], although an endothermic process has
been reported for a BSA/polyelectrolyte system [116]. In addition to electrostatic
interactions, the entropic contribution of the release of small counterions and water
molecules has also been reported. For synthetic polyelectrolytes interacting with
proteins, it is postulated that the interaction process is the result of a competition
between the attractive electrostatic interactions between polyelectrolytes and proteins
in one hand, and the polymer characteristics on the other hand. This was modelled by
Muthukumar [117], taking into account the charge densities, size, Debye length and
the molecular weight of involved macromolecules.
Control of these interactions is of importance for the design of a variety of
supramolecular structures with different intrinsic properties. Before considering the
cross-assembly between proteins, we first present some general elements on the
interaction of proteins with linear polyelectrolytes. Some examples published
during the last 10 years on dual systems involving a mixture of protein and
82
S. Bouhallab and T. Croguennec