Editing Protein structure prediction (section)

===Deltas===
Some parts of the protein have fixed three-dimensional structure, but do not form any regular structures. They should not be confused with [[Intrinsically disordered proteins|disordered or unfolded segments]] of proteins or [[random coil]], an unfolded polypeptide chain lacking any fixed three-dimensional structure. These parts are frequently called "[[Coordination_complex#Optical_isomerism|deltas]]" (''Δ'') because they connect β-sheets and α-helices. Deltas are usually located at protein surface, and therefore mutations of their residues are more easily tolerated. Having more substitutions, insertions, and deletions in a certain region of a sequence alignment maybe an indication of some delta. The positions of [[introns]] in genomic DNA may correlate with the locations of loops in the encoded protein {{Citation needed|date=March 2012}}. Deltas also tend to have charged and polar amino acids and are frequently a component of active sites.