21.1. INTRODUCTION: WATER, CELL INSPIRATIONS, AND COPOLYMERS

H ₂O is the predominant compound of most biological systems typically ~70% by mass, and so it is not surprising that a major driving force for molecular assembly in biology exploits water. The hydrophobic effect that makes oil coalesce in water drives proteins to fold into functional forms and also bind one another. Such binding generates complex machines such as protein-synthesizing ribosomes, reinforcing scaffolds like filamentous cytoskeletons, and many other structures. The membranes that define and delimit both cells and cellular sub-compartments like the nucleus and mitochondria also form largely due to the hydrophobic effect. All of these many structures form because the constituent molecules, lipids, are generally polymers (if small) composed of both oily, hydrophobic monomers and water-soluble, polar monomers. For example, of the nineteen natural amino acids that make up polypeptides or proteins, nine are hydrophobic and thus more soluble in carbon-based oils and solvents than in H ₂O. Likewise, the lipids that make up cell membranes have a dual hydrophobic-polar (or H-P) nature, but this is generally arranged in a more segmented or block fashion (e.g., HHH-PP) than found for the amino acids in proteins. The sequential or block arrangement is generally referred to as amphiphilic. What emerges from such simplistic overviews of hydrophobicity in molecular biology are na ve templates for creating biomimetic nanostructures through aqueous self-assembly.

Whether one is conjuring synthetic mimics...