Barry D. Olafson

Abstract CHARMM ( C hemistry at HAR vard M acromolecular M echanics) is a highly flexible computer program which uses empirical energy functions to model macromolecular systems. The program can read or model build structures, energy minimize them by first‐ or second‐derivative techniques, perform a normal mode or molecular dynamics simulation, and analyze the structural, equilibrium, and dynamic properties determined in these calculations. The operations that CHARMM can perform are described, and some implementation details are given. A set of parameters for the empirical energy function and a sample run are included.

We report the parameters for a new generic force field, DREIDING, that we find useful for predicting structures and dynamics of organic, biological, and main-group inorganic molecules. The philosophy in DREIDING is to use general force constants and geometry parameters based on simple hybridization considerations rather than individual force constants and geometric parameters that depend on the particular combination of atoms involved in the bond, angle, or torsion terms. Thus all bond distances are derived from atomic radii, and there is only one force constant each for bonds, angles, and inversions and only six different values for torsional barriers. Parameters are defined for all possible combinations of atoms and new atoms can be added to the force field rather simply. This paper reports the parameters for the "nonmetallic" main-group elements (B, C, N, 0, F columns for the C, Si, Ge, and Sn rows) plus H and a few metals (Na, Ca, Zn, Fe). The accuracy of the DREIDING force field is tested by comparing with (i) 76 accurately determined crystal structures of organic compounds involving H, C, N, 0, F, P, S, CI, and Br, (ii) rotational barriers of a number of molecules, and (iii) relative conformational energies and barriers of a number of molecules. We find excellent results for these systems.

How many metals to oxidize methane? Methane is an important fuel, but there are few direct transformations to partially oxidized products. Bacteria use metalloenzymes to catalyze methane oxidation to methanol, a reaction of industrial interest. Understanding the metal sites that enable this reaction may inspire new biomimetic catalysts. Ross et al. used spectroscopic measurements to assign two monocopper sites in the enzyme particulate methane monooxygenase. These results differ in part from previous proposals for the location and nuclearity of the metal sites and will prompt rethinking about how this metalloenzyme catalyzes methane oxidation. Science , this issue p. 566

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTApplication of molecular simulation to derive phase diagrams of binary mixturesCun Feng Fan, Barry D. Olafson, Mario Blanco, and Shaw Ling HsuCite this: Macromolecules 1992, 25, 14, 3667–3676Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July 1992https://pubs.acs.org/doi/10.1021/ma00040a010https://doi.org/10.1021/ma00040a010research-articleACS PublicationsRequest reuse permissionsArticle Views1716Altmetric-Citations216LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts