Structural biology

Structural biology is a branch of molecular biology concerned with the study of the architecture and shape of biological macromolecules&mdash;proteins and nucleic acids in particular&mdash;and what causes them to have the structures they have. This subject is of great interest to biologists, because macromolecules carry out most of the functions of a cell, and because typically it only is by coiling into a specific three-dimensional shape that they are able to perform their functions. This shape, which is called the "tertiary structure" of a molecule, depends in a complicated way on the molecule's basic composition, or "primary structure."

Biomolecules are too small to see in detail even with the most advanced light microscopes. The methods that structural biologists use to determine their structures generally involve measurements on vast numbers of identical molecules at the same time. These methods include crystallography, NMR, ultra fast laser spectroscopy, electron microscopy, electron cryomicroscopy (cryo-EM), Dual Polarisation Interferometry and circular dichroism. Most often researchers use them to study the static "native states" of macromolecules. But variations on these methods are also used to watch nascent or denatured molecules assume or reassume their native states (see e.g. protein folding).

A third approach that structural biologists take to understanding structure is bioinformatics to look for patterns among the diverse sequences that give rise to particular shapes. Researchers often can deduce aspects of the structure of integral membrane proteins based on the membrane topology predicted by hydrophobicity analysis. See: protein structure prediction.

In the past few years it has become possible for highly accurate physical molecular models to complement the in silico study of biological structures.