An exponential modeling algorithm for protein structure completion by X-ray crystallography

An exponential modeling algorithm is developed for protein structure comple tion by X-ray crystallography and tested on experimental data from a 59-res idue protein. An initial noisy difference Fourier map of missing residues o f up to half of the protein is transformed by the algorithm into one that a llows easy identification of the continuous tube of electron density associ ated with that polypeptide chain. The method incorporates the paradigm of p hase hypothesis generation and cross validation within an automated scheme.