Before revision: Consistently predicting protein structure at atomic resolution from sequence alone remains an unsolved challenge in computational biophysics. Even small puzzles involving protein loops excised out of crystallographic structures can become intractable as loop lengths exceed 10 residues and if surrounding side-chain conformations are erased.
After revision: Consistently predicting protein structure at atomic resolution from sequence alone remains a difficult problem, even for small sub-segments of large proteins. Such loop prediction challenges, which arise frequently in comparative modeling and protein design, can become intractable as loop lengths exceed 10 residues and if surrounding side-chain conformations are erased.