ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 14 (1993), S. 1272-1280 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Computer methods for analytic surface calculations of molecular systems suffer from numerical instabilities and are CPU time consuming. In this article, we present proposals toward the solution of both problems. Singularities arise when nearly collinear triples of neighboring atoms or multiple vertices are encountered during the calculation. Topological decisions in analytic surface calculation algorithms (accessibility of vertices and arcs) are based upon the comparison of distances or angles. If two such numbers are nearly equal, then currently used computer programs may not resolve this ambiguity correctly and can subsequently fail. In this article, modifications in the analytic surface calculation algorithm are described that recognize singularities automatically and treat them appropriately without restarting parts of the computation. The computing time required to execute these alterations is minimal. The basic modification consists in defining an accuracy limit within which two values may be assumed as equal. The search algorithm has been reformulated to reduce the computational effort. A new set of formulas makes it possible to avoid mostly the extraction of square roots. Tests for small-and medium-sized intersection circles and for pairs of vertices with small vertex height help recognize fully buried circles and vertex pairs at an early stage. The new program can compute the complete topology of the surface and accessible surface area of the protein crambin in 1.50-4.29 s (on a single R3000 processor of an SGI 4D/480) depending on the compactness of the conformation where the limits correspond to the fully extended or fully folded chain, respectively. The algorithm, implemented in a computer program, will be made available on request. © John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The double cubic lattice method (DCLM) is an accurate and rapid approach for computing numerically molecular surface areas (such as the solvent accessible or van der Waals surface) and the volume and compactness of molecular assemblies and for generating dot surfaces. The algorithm has no special memory requirements and can be easily implemented. The computation speed is extremely high, making interactive calculation of surfaces, volumes, and dot surfaces for systems of 1000 and more atoms possible on single-processor workstations. The algorithm can be easily parallelized. The DCLM is an algorithmic variant of the approach proposed by Shrake and Rupley (J. Mol. Biol., 79, 351-371, 1973). However, the application of two cubic lattices - one for grouping neighboring atomic centers and the other for grouping neighboring surface dots of an atom - results in a drastic reduction of central processing unit (CPU) time consumption by avoiding redundant distance checks. This is most noticeable for compact conformations. For instance, the calculation of the solvent accessible surface area of the crystal conformation of bovine pancreatic trypsin inhibitor (entry 4PTI of the Brookhaven Protein Data Bank, 362-point sphere for all 454 nonhydrogen atoms) takes less than 1 second (on a single R3000 processor of an SGI 4D/480, about 5 MFLOP). The DCLM does not depend on the spherical point distribution applied. The quality of unit sphere tesselations is discussed. We propose new ways of subdivision based on the icosahedron and dodecahedron, which achieve constantly low ratios of longest to shortest arcs over the whole frequency range. The DCLM is the method of choice, especially for large molecular complexes and high point densities. Its speed has been compared to the fastest techniques known to the authors, and it was found to be superior, especially when also taking into account the small memory requirement and the flexibility of the algorithm. The program text may be obtained on request. © 1995 by John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...