Map interpretation remains a critical step in solving the structure of a macromolecule. Errors introduced at this early stage may persist throughout crystallographic refinement and result in an incorrect structure. The normally quoted crystallographic residual is often a poor description for the quality of the model. Strategies and tools are described that help to alleviate this problem. These simplify the model-building process, quantify the goodness of fit of the model on a per-residue basis and locate possible errors in peptide and side-chain conformations.

The Uppsala Electron Density Server (EDS; http:// eds.bmc.uu.se/) is a web-based facility that provides access to electron-density maps and statistics concerning the ®t of crystal structures and their maps. Maps are available for $87% of the crystallographic Protein Data Bank (PDB) entries for which structure factors have been deposited and for which straightforward map calculations succeed in reproducing the published R value to within ®ve percentage points. Here, an account is provided of the methods that are used to generate the information contained in the server. Some of the problems that are encountered in the map-generation process as well as some spin-offs of the project are also discussed.

In order to accurately detect excitation system parameters, this paper presents a algorithm based on the TLS-ESPRIT. The matrix pencil algorithm is used to extract the frequency and damping of each component of system response. So it's necessary to apply the Laplace transform for s function of excitation system. After getting the Laplace transform of a function f(t), as mean as impulse response for excitation system. Then the magnitude and phase of each component of impulse response are estimated by least squares method, thus achieving the excitation system parameters. In the end, the simulation results show when SNR is between 35dB to 30dB, it still accurately identified the parameters.