Atomic displacement parameters in structural biology

Atomic displacement parameters (ADPs, also known as B-factors), which depend on structural heterogeneity, provide a wide spectrum of information on protein structure and dynamics and find several applications, from protein conformational disorder prediction to protein thermostabilization, and from protein folding kinetics prediction to protein binding sites prediction. A crucial aspect is the standardization of the ADPs when comparisons between two or more protein crystal structures are made, since ADPs are differently affected by several factors, from crystallographic resolution to refinement protocols. A potential limitation to ADP analysis is the modern tendency to let ADPs to inflate up to extremely large values that have little physico-chemical meaning.