Table 2.

Main techniques for obtaining the 3D structure of macromolecules

Experimental	Technique	Definition
	X-Ray crystallography	One of the most used technique for structure determination of proteins and macromolecules. A purified sample at high concentration is crystallized and exposed to an x-ray beam. Those results can be processed allowing to obtain the 3D structure of the molecule [71]
	Nuclear Magnetic Resonance Spectroscopy	Analytical chemistry technique that reveals the atomic structure of macromolecules in highly concentrated solutions based on the fact that certain atomic nuclei (such as H, 13C, 19F, 23Na, or 31P) are intrinsically magnetic [72]. Provides unique information about dynamics and interactions but the determination of the atomic structure is restricted to small complexes
	Cryo-Electron Microscopy	Based on the imaging of frozen-hydrated molecules by electron microscopy. Allows obtaining molecular resolution but in recent studies atomic resolution has been achieved [73]
Computational	Homology modelling	Computational prediction method that allows to determine the protein 3D structure from its amino acid sequence based on 3D structure templates of proteins with similar sequences[74]