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  • ESI-MS investigation of solvent effects on the chiral recognition capacity of tartar emetic towards neutral side-chain amino acids.

ESI-MS investigation of solvent effects on the chiral recognition capacity of tartar emetic towards neutral side-chain amino acids.

Chirality (2010-12-03)
Aruna B Wijeratne, Samuel H Yang, Jose Gracia, Daniel W Armstrong, Kevin A Schug
ABSTRACT

The effect of solvent systems on previously-reported ESI-MS based proton-assisted enantioselective molecular recognition phenomena of tartar emetic, L-antimony(III)-tartrate, was evaluated. This was achieved by carrying out a series of competitive binding experiments using chiral selectors, bis(sodium) D- and -L-antimony(III)-tartrates with chiral selectands, neutral side-chain amino acid enantiomeric isotopomers of alanine (Ala), valine (Val), leucine (Leu) and phenylalanine (Phe), in three different solvent systems, ACN/H(2)O (75/25 v/v), H(2)O (100%) and H(2)O/MeOH (25/75 v/v). Observations from these experiments suggest that the effect of solvent systems on previously reported proton-assisted chiral recognition capacity of D,L-antimony(III)-tartrates is small, but not negligible. It was observed that an ACN/H(2)O (75/25 v/v) solvent system facilitates and enhances the chiral discrimination capacity of protonated {[D,L-Sb(2)-tar(2)][H]}(-) ionic species. Further, amino acid enantiomers showed a general trend of increasing selectivity order, Val ≤ Ala < Leu ≈ Phe towards the protonated {[D,L-Sb(2)-tar(2)][H]}(-) ionic species which was independent of the solvent system employed. The lack of enantioselective binding for {[D,L-Sb(2)-tar(2)]}(2-) ionic species was consistently recorded in respective mass spectra from all performed experiments, which suggests that ESI-friendly solvent systems have no effect and do not influence this phenomenon.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Potassium antimonyl tartrate trihydrate, purum p.a., 99.0-103% (RT)
Sigma-Aldrich
Potassium antimonyl tartrate trihydrate, puriss., meets analytical specification of USP, 99.0-103.0%, powder
Sigma-Aldrich
Potassium antimonyl tartrate trihydrate, ACS reagent, ≥99%