Separation Of Tryptophan Enantiomers Research Articles

Magnetic carbon nanotubes grafted with smart polymer brushes for highly efficient enantioseparation of tryptophan enantiomers

We herein report a novel chiral carbon nanotube nanomaterial (MCNTs–PNG–CD) grafted with smart copolymer brushes for highly efficient chiral recognition and separation of tryptophan enantiomers (dl-Trp).

Chiral ionic liquids as chiral selectors for separation of tryptophan enantiomers by ligand exchange chromatography

Chiral ionic liquids (CILs) containing imidazolium cations and L-Proline (L-Pro) anions were applied as chiral selector to separate tryptophan (Trp) enantiomers on a C18 column by ligand exchange chromatography. Several factors influencing Trp enantiomers separation, such as alkyl chain length of CILs, concentrations of Cu2+ and CILs, pH of the mobile phase, flow rate, organic solvent and temperature, were studied. Under the optimal conditions, the Trp enantiomers could be successfully separated within 21 min with the resolution of 2.30. At the same time, some thermodynamical parameters were obtained. The experimental results show that the enthalpy values of the Trp enantiomers are negative, indicating that the separation process is exothermic. And the enthalpy values of D-Trp are larger than those of L-Trp, which indicates that L-Trp could form more stable ternary complexes with tryptophan enantiomers.

Preparation of a Monolith with Covalently Bound Bovine Serum Albumin for Capillary Electrochromatography

Capillary electrochromatography (CEC) is important for applications in enantiomer separation. The problems associated with column fabrication bring a challenge in developing monoliths with ease of preparation, robustness of separation, enhanced mass transfer, and lower pressure drop. In this research, the covalent binding of proteins on to a monolithic matrix was investigated to overcome the drawback of loss and/or denaturing of the biomolecules from physical adsorption and encapsulation method. A chitosan/silica hybrid monolith was prepared and a protein, bovine serum albumin, was covalently immobilized on the column. The prepared monolith was evaluated using the enantioseparation of D,L-tryptophan by CEC. It was found that separation of tryptophan enantiomers with a resolution of 2.44 was achieved by using 20 mmol L−1 phosphate buffer at pH 7.5. A higher chitosan concentration was also proven to be of possible use in the synthesis with the aid of acetic acid as the solvent. The much shorter retention time and increased separation ability demonstrate the advantages of capillary column under investigation.

Separation of tryptophan enantiomers with polypyrrole electrode column by potential-induced technique

Polypyrrole (PPy), synthesized by chemical oxidation in the presence of l-tryptophan ( l-Trp) as template molecules, was packed into a porous ceramic column as the conductive stationary phase to fabricate an electrode column which can be regarded as a working electrode of a three-electrode system from an electrochemical point of view. The electric potential of this column can be easily controlled by a potentiostat. l-Trp anions were ejected from the PPy backbone after overoxidation of PPy, and thus cavities complementary to l-Trp were left in the stationary phase. When the solution containing l- or d-Trp was pumped through the column packed with imprinted overoxidized polypyrrole (oPPy), a negative potential was applied on the electrode column for re-binding Trp enantiomers. The novel electrode column offers an excellent chiral selectivity for l-Trp over d-Trp as the result of stereochemistry, and it also displays satisfactory selectivity for tyrosine (Tyr) enantiomers which is analogous to Trp in structure. The advantage of this method proposed over previously reported is that the separation of amino acids enantiomers can be performed in a high efficiency by controlling the potential applied on the electrode column.

Separation of tryptophan enantiomers with molecularly imprinted polypyrrole electrode column

In this study, we have fabricated molecularly imprinted polypyrrole (PPy) packed electrode columns and investigated their effects on separation of tryptophan (Trp) enantiomers by using potential control. The results indicate that the imprinted PPy electrode columns could efficiently enhance the L-Trp uptake and separate Trp enantiomers effectively, implying the great potential for the enantioselective recognition of other amino acids enantiomers.

Chiral separation of tryptophan enantiomers by liquid chromatography with BSA-silica stationary phase

The separation of tryptophan enantiomers was carried out with medium-pressure liquid chromatography using BSA (bovine serum albumin)-bonded silica as a chiral stationary phase. The influence of various experimental factors such as pH and ionic strength of mobile phase, separation temperature, and the presence of organic additives on the resolution was studied. In order to expand this system to preparative scale, the loadability of sample and the stability of stationary phase for repeated use were also examined. The separation of tryptophan enantiomers was successful with this system. The data indicated that a higher separation factor (α) was obtained at a higher pH and lower temperature and ionic strength in mobile phase. Addition of organic additives (acetonitrile and 2-propanol) in mobile phase contributed to reduce the retention time of L-tryptophan. About 30% of the separation factor was reduced after 80 days of repeated use.