Building single-molecule machines
Virtually all cell processes that rely on interactions between two molecules involve the need for recognition in order for interaction to take place. Many important biological molecules are chiral, having two forms consisting of the same atoms but whose structures are non-superimposable mirror images of each other. Others exist exclusively in one chiral form (they exhibit homochirality), for example the building blocks of proteins (amino acids) and the sugars that make up deoxyribonucleic acid (DNA). Obviously, chirality plays a critical role in the efficiency of recognition. Many scientists believe that without uniform chirality as exhibited by amino acids and some sugars, life as we know it could not exist. Active transport is one cellular function that relies on locking and unlocking of molecules, like a train on its tracks. In order for molecules and other cell constituents to be moved within cells or across their cell membranes against their concentration gradients, the process requires energy. Active transport is driven by molecular (protein) motors. In order to ‘build’ future molecular machines and molecular motors, scientists must develop a thorough understanding of how two molecules ‘shake hands’ through mutually induced conformational changes at the single-molecule level. European scientists therefore initiated the ‘Molecular machines - design and nano-scale handling of biological antetypes and artificial mimics’ (Biomach) project. Researchers employed scanning tunnelling microscopy (STM) to make ‘movies’ of how two molecules of the same chirality form pairs and chains while molecules with different chirality cannot form stable structures. Insight obtained through Biomach experiments should not only enhance basic understanding of physiological processes but also facilitate the development of single-molecule biomimetic working devices.
