3-D structural modeling of humic acids through experimental characterization, computer assisted structure elucidation and atomistic simulations 1. Chelsea soil humic acid.
- Pacific Northwest National Laboratory
- Ohio State University
- University of Toronto
- - California Institute of Technology, Pasadena, CA
- California Institute of Technology, Pasadena, CA
- Howard University
This paper describes an integrated experimental and computational framework for developing 3-D structural models for humic acids (HAs). This approach combines experimental characterization, computer assisted structure elucidation (CASE), and atomistic simulations to generate all 3-D structural models or a representative sample of these models consistent with the analytical data and bulk thermodynamic/structural properties of HAs. To illustrate this methodology, structural data derived from elemental analysis, diffuse reflectance FT-IR spectroscopy, 1-D/2-D {sup 1}H and {sup 13}C solution NMR spectroscopy, and electrospray ionization quadrupole time-of-flight mass spectrometry (ESI QqTOF MS) are employed as input to the CASE program SIGNATURE to generate all 3-D structural models for Chelsea soil humic acid (HA). These models are subsequently used as starting 3-D structures to carry out constant temperature-constant pressure molecular dynamics simulations to estimate their bulk densities and Hildebrand solubility parameters. Surprisingly, only a few model isomers are found to exhibit molecular compositions and bulk thermodynamic properties consistent with the experimental data. The simulated {sup 13}C NMR spectrum of an equimolar mixture of these model isomers compares favorably with the measured spectrum of Chelsea soil HA.
- Research Organization:
- Sandia National Laboratories
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 993893
- Report Number(s):
- SAND2003-2501J
- Journal Information:
- Proposed for publication in Environmental Science and Technology., Journal Name: Proposed for publication in Environmental Science and Technology. Journal Issue: 9 Vol. 37; ISSN ESTHAG; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
Similar Records
The chemical structure of highly aromatic humic acids in three volcanic ash soils as determined by dipolar dephasing NMR studies
Alicyclic carboxylic acids in soil humic acid as detected with ultrahigh resolution mass spectrometry and multi-dimensional NMR