Collection of new experimental data

The Chodera lab is building the ability to collect new experimental data for forcefield parameterization

NMR data

SKI has a Bruker 600 MHz NMR instrument as part of the analytical NMR core facility that is available for us to use. The instrument has a 40-sample changer, but a 200-sample chamber can be installed for larger volume experiments.

Kyle Beauchamp is currently investigating the collection of quantitative NMR data of several types:

• binary mixtures, where intermolecular NOEs can provide useful information on nonbonded interactions
• short zwitterionic synthetic peptides, where intramolecular NOEs, J-coupling constants, and potentially chemical shifts can provide quantitative data on conformational equilibria
• small molecules in water

MRS: I'm interested to know what sort of NOE intermolecular information can one get on nonbonded interactions in small molecules when there's so much orientational averaging? I'm used to thinking about proteins where the distances don't change as much.

Excess densities

The temperature-dependent densities of neat liquids and binary mixtures can provide an enormous amount of useful data on intermolecular interactions, sufficient to parameterize vdW forcefield terms and likely even atom type-atom type interaction parameters (rather than simple mixing rules).

The Chodera lab will be acquiring a Mettler-Toledo DM40 density meter which can measure densities from 0-3 g/cm3 with an accuracy of 0.0001 g/cm3 over the range of 0-91C. We will also acquire a 30-sample changer that allows us to automate the collection of multiple liquids or mole-fractions of binary mixtures, such that a single 8-hour experiment could allow us to collect binary mixture data over the 2D space of mole-fractions x and temperatures T to produce a 30x30 sampling of density rho(x,T) to 0.0001 g/cm3 accuracy.

MRS: I think this would be fantastic. With the properly chosen small molecules, the required data would be relatively small. We should make sure the approaches are compatible with best practices for density data, reproducing some data we feel are very well taken first.

MRS: To get both T and P data, it would be great to get partial molar enthalpies (excess enthalpies) as well. What are the calorimetric capabilities there?