Structural biology is a branch of molecular biology that focuses on the study of the three-dimensional structures of biological molecules, particularly proteins and nucleic acids. The ultimate goal of structural biology is to understand the relationship between the structure of a molecule and its function, and to use this knowledge to design new drugs, enzymes, and other biomolecules with improved properties.

Structural biology employs a wide range of techniques to determine the structures of biological molecules, including X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, cryo-electron microscopy (cryo-EM), and computational modeling. Each technique has its own strengths and limitations, and is used depending on the size and complexity of the molecule being studied, as well as the resolution and accuracy required for the study.

X-ray crystallography is the most widely used method for determining the structures of proteins and other biological macromolecules. In this technique, a crystal of the molecule is bombarded with X-rays, which are diffracted by the atoms in the crystal. The resulting diffraction pattern is used to determine the positions of the atoms in the molecule.

NMR spectroscopy is used to determine the structures of proteins and other molecules in solution. In this technique, the molecule is placed in a strong magnetic field, which causes the nuclei of the atoms to align. A radiofrequency pulse is then used to excite the nuclei, and the resulting signals are used to determine the distances between atoms in the molecule.

Cryo-electron microscopy is a newer technique that allows the determination of high-resolution structures of large, complex biological molecules, including macromolecular complexes and viruses. In this technique, the molecule is rapidly frozen and imaged using an electron microscope. The resulting images are combined to create a 3D map of the molecule.

Computational modeling is also an important tool in structural biology, allowing the prediction of protein structures from amino acid sequences, as well as the refinement of experimentally determined structures.

Overall, structural biology plays a critical role in our understanding of the molecular basis of life and the development of new drugs and therapies for a wide range of diseases.