Table 1.

Current biophysical approaches in studying conformational control of NOSs

Technique	Results	Information obtained from the data
Cryo EM	Transmission electron microscopes images	Higher-order NOS domain architecture and quaternary structure
smFRET	FRET signal of individual protein molecules in real time	Conformational states distribution and interconversion rates
Pulsed EPR	Distances between paramagnetic centers & distance distribution	Structure of the docking complex and conformational equilibrium
HDX MS	Monitoring perturbations in amide proton exchange rate changes	Interdomain interaction surfaces (at peptide level) induced by CaM and/or phosphorylation
Laser flash photolysis	Kinetics of the discrete FMN-heme IET process	A direct measure of the interdomain FMN-heme complex formation
Solvent perturbation stopped flow	Electron transfer rates as a function of pressure, viscosity and ionic strength	Functional significance of the rugged energy landscape