Computational Study of Chiral Separations by Ion Mobility Spectrometry
EMSL Project ID
31293
Abstract
This proposal is a rapid access request for computational and EMSL staff resources for a computational study that probes the mechanism of a novel separation method for chiral compounds in which gas phase chiral ions are produced from electrospray ionization and separated by their mobilities. The rapid access request will allow graduate student Natalia Zakharova to visit EMSL and learn how to use the ab-initio molecular dynamics capabilities within the NWChem computational chemistry program and gain timing information for a standard access, general proposal for computing time at EMSL. Ab-initio MD simulations will be used to calculate collisional cross-sections of ions that are separated in the gas phase using ion mobility spectrometry (IMS). The basic process of ion mobility separation is simple: as gas phase ions migrate through a low electric field in a buffer gas such as nitrogen, ions are repeatedly accelerated by the field and decelerated by collisions with the buffer gas molecules. These accelerations and decelerations result in a unique constant average ion velocity through the buffer gas in the direction of the electric field which is related to the ions size and its interaction with the buffer gas during collisions. Thus ions are separated based on their size and ion-molecule interaction potentials. Recently, our experimental collaborator at WSU (Herb Hill) and his research group have discovered and demonstrated that chiral compounds can be separated in the gas phase with IMS. For the separation of enantiomers, a small quantity of a chiral compound is added to the buffer gas. From the initial experiments which have been conducted, the mechanism of chiral separation is not clear. Do enantiomer ions separate by small differences in their interaction potentials with the chiral modifier molecules as they drift through the buffer gas or do they form transient diastereomers and separate by differences in size? Ab-initio molecular dynamics simulations are ideally suited to calculate the interaction potentials between enantiomer and chiral modifiers, as well as the collisional cross-sections of transient diasteriomers under conditions that closely match those of experiment. It is believed that these calculations will yield fundamental information regarding the mechanism of chiral separation and can be applied to the design of systems that separate biologically relevant molecules.
Project Details
Project type
Limited Scope
Start Date
2008-08-04
End Date
2008-09-18
Status
Closed
Released Data Link
Team
Principal Investigator