| 摘要 |
An electron density for a crystallographic structure having protein regions and solvent regions is improved by maximizing the log likelihood of a set of structures factors {Fh} using a local log-likelihood function:where pPROT(x) is the probability that x is in the protein region, p(rho(x)|PROT) is the conditional probability for rho(x) given that x is in the protein region, and pSOLV(x) and p(rho(x)|SOLV) are the corresponding quantities for the solvent region, pH(x) refers to the probability that there is a structural motif at a known location, with a known orientation, in the vicinity of the point x; and p(rho(x)|H) is the probability distribution for electron density at this point given that the structural motif actually is present. One appropriate structural motif is a helical structure within the crystallographic structure.
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