It's an asymmetric world

2003-03-25

COMP D

Computers in Chemistry General Contributions

8:30a, #134: Estimation of physicochemical properties of compounds by SPARC

S.H. HIlal, L.A. Carreira, S.W. Karichkoff (EPA/UGA)

• Sparc Performs Automatic Reasoning in Chemistry: program to calc. properties and reactivity based solely on molecular structure.
• Capabilities: chemical and physical properties.

• Basically, it calculates a set of core properties, and all others are derived from these

  • Vapor pressure (temp)
  • Activity coefficient (temp, solv)
  • Ionization pKa (temp, pH, solv): microscopic, zwitterionic constant, molecular speciation, isoelectric point

• Approach: Molecule is broken into functional units, each with intrinsic properties, e.g. p-amino phenol --> -NH2 = Reference point, -Ph- = Resonance, HO- = Electrostatic
• Intermolecular interaction model: DeltaG(interaction) = DeltaG(dispersion) + DeltaG(induction) + DeltaG(dipole) + DeltaG(H-bond) + DeltaG(mix)
• Vapor pressure model has been tested by calculating boiling points from -200 C --> 1000 C
  • Non-polars have an error of +/- 3 C
  • Polars have an error of +/- 7.5 C
• Activity coefficient comparisons (calculated vs experimental): R^2 = 0.998, RMS = 0.064, N = 491
  • Solubility: R^2 = 0.987, RMS = 0.40, N = 647
• Similar good correlations for ionization pKa's, etc.
• SPARC accepts as input a SMILE string or a CAS reg number

8:55a, #135: Calculation of tautomeric equilibrium network constants using SPARC

S.N. Ayyampalayam, L.A. Carreira (EPA/UGA)

• SPARC does not do first principle calculations, it is based on mechanistic perturbation models
• Descriptors: density, polarizability, index of refraction, and H-bonding (alpha/beta)
• System can calculate tautomeric equilibirum networks, irrespective from the initial input structure
• SPARC is written in Prolog
• URL: http://ibmlc2.chem.uga.edu/sparc

9:20a, #136: OptiDesign: Extending optimizable K-dissimilarity selection (OptiSim) for use in combinatorial library design

F. Soltanshahi, L. Alkella, R.D. Clark (TRIPOS)

• OptiDesign: Select diverse representatives from a population
• In 2D designs (or higher dimensionality), it uses axis pivoting for selection
• It can do full and sparse matrix designs
• Maximum dissimilarity approach
• Multi-block designs also possible
• Backtrack redesigns
• User-defined filters, contraints, and evaluation parameters, including bias towards reagents, etc.
• Ref: J. Mol. Graph. Model. 2000, 18, 404

9:45a, #137: Predictive toxicology using quantum QSAR descriptors from intermediates

S. Trohalaki, R. Patcher, K.T. Geiss, J.M. Frazier (Air Force Research Labs)

• QSARs derived from

  • neutral descriptors
  • radical descriptors
  • combination of neutral and radical

• Applied to HAs (halogen aliphatics), which exhibit toxicity, in particular liver toxicity
• Best correlations when using both neutral and radical descriptors

10:10a, #138: WITHDRAWN

10:35a, #139: WITHDRAWN

11:00a, #140: Web services as applications' integration tool: QikProp case study

V.R. Polyakov, A. Laoul, W.L. Jorgensen (Global LG Informatics/Aventis)

• QikProp (W. Jorgensen) is a DOS program used to predict biopharmaceutical properties
  • Caculates: solubility, adsorption, distribution, metabolism, and excretion (ADME)
  • Uses 3D descriptors for its internal calculations
  • Input format: SD or MOL (both are MDL formats)

PHYS A

Physical Chemistry Awards Symposium

2:10p, #168: Award Address (ACS Award in Theoretical Chemistry) - Quantum Chemistry in the 21st Century

Fritz Schaefer (UGA)

• Next generation: Explicitly correlated electronic structure methods for molecules
• "Sub-chemical" accuracy methods: approx. 0.1 kcal/mol, compared to current methods: 1.0 kcal/mol
• Cusps appear in current orbital methods

COMP A

ACS Award for Computers in Chemical and Pharmaceutical Research

4:20p, #155: Award Address (ACS Award for Computers in Chemical and Pharmaceutical Research) - Discovery through computation

K.N. Houk