| AVS 62nd International Symposium & Exhibition | |
| Biomaterials Plenary Session | Sunday Sessions |
| Session BP-SuA |
| Session: | Biomaterials Plenary Session |
| Presenter: | Jacob Israelachvili, University of California at Santa Barbara |
| Correspondent: | Click to Email |
I will try to consider some key fundamental questions and challenges in the interactions of biomolecules and biosurfaces – what important interactions we still don’t understand, what is known but is subtle and often misunderstood, and current experimental and theoretical limitations that need to be overcome – all with examples to illustrate the points being made.
The hydrophobic interaction is one of the most important for determining biomolecular organization (of membranes, proteins) but is still not understood both at the experimental and theoretical levels; for example, there is still no generally accepted “interaction potential” or “force law” for this interaction, although it appears to be an exponential functions of the separation between surfaces (but as yet totally unknown between molecules or hydrophobic groups).
Perhaps more importantly for biological interactions, given that living systems are never at rest, or at thermodynamic equilibrium, or even necessarily tending toward the equilibrium state, the issue of non-equilibrium interactions is still a very dark area. I am not referring here to viscous forces, but to interaction potentials that are inherently rate or time-dependent. Some ligand-receptor binding and unbinding interactions present good examples of such “dynamic” interactions.
A very commonly misunderstood feature in the area of bioadhesion is the difference between strong and weak bonds, or high adhesion and low adhesion. Without specifying whether one is talking about the energy or the force, any comparisons can be meaningless. Examples will be given of real situations where the same change in energy can result in 8 orders of magnitude difference in the forces (pressures or stresses) depending on the geometry, i.e., structure and mechanical properties of the adhering (bio)material surfaces. There are also many practical situations where friction and adhesion forces are involved simultaneously, for example, when geckos run on walls and ceilings, giving rise to very subtle effects.
Experimental and theoretical (e.g., simulation) challenges involving complex biological interactions will also be discussed: these involve ‘scaling effects of size’ (converting the interactions of single or a few molecules or bonds to those between biological surfaces that involve the correlated interactions of many molecules or bonds, usually at different locations), and ‘scaling effects of time’ where the time scales of a biological process involving multiple (sequential) interactions that evolve both in space and time over large distances and long times are currently inaccessible by computers.