Physical thoughts, biological systems

The most obvious stimulus to ehiral induction is the use of stereogenie eenters, but external perturbation, such as physical fields ean also be used to induce chirality. The term is applied to traditional asymmetric synthesis through covalent bonds as well as to supramolecular synthesis, which is our interest here. Mention the word "chirality" to any chemist, and thoughts will be conjured of the right-handed B-DNA double helix, the right-handed a-helices formed by peptides of the natural L-amino acids, of thalidomide, and other emblematic and dramatic examples of the importanee of stereochemistry. It is clear that the chirality of the eomponents of biological systems play a key role in their function, in which induction of chirality through noncovalent bonds is inherent. But beyond natural systems and related phenomena, there is a wealth of unnatural chemical systems that display remarkable and important properties. 

This should not lead to any reductionist view of biological or social systems. If some part of the complexity which was thought to be an exclusive attribute of these systems can be found in physical and chemical systems, we may hope to get a better understanding of the specificity of social and biological systems. 

Matter includes everything that is tangible, from our bodies and the stuff of our everyday lives to the grandest objects in the universe. Some call chemistry the central science. It rests on the foundation of mathematics and physics and in turn underlies the life sciences—biology and medicine. To understand living systems fully, we must first understand the chemical reactions and chemical influences that operate within them. The chemicals of our bodies profoundly affect even the personal world of our thoughts and emotions. 

In this chapter we introduced the basic physical chemistry that governs catalytic reactivity. The catalytic reaction is a cycle comprised of elementary steps including adsorption, surface reaction, desorption, and diffusion. For optimum catalytic performance, the activation of the reactant and the evolution of the product must be in direct balance. This is the heart of the Sabatier principle. Practical biological, as well as chemical, catalytic systems are often much more complex since one of the key intermediates can actually be a catalytic reagent which is generated within the reaction system. The overall catalytic system can then be thought of as nested catalytic reaction cycles. Bifunctional or multifunctional catalysts realize this by combining several catalytic reaction centers into one catalyst. Optimal catalytic performance then requires that the rates of reaction at different reaction centers be carefully tuned. 

---