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Biomedical subjects

Tingyu Li

Publications and source records attributed to Tingyu Li.

6 recordsLinked to original sources
PubMed2003

The role of analogue ions in the ion-pair reversed-phase chromatography of quaternary ammonium compounds.

The choice of analogue ion of the mobile phase additive is shown to significantly affect the analysis of quaternary ammonium compounds (QACs) in ion-pair reversed-phase high-performance liquid chromatography. A series of bromide-containing and dodecyl-sulfate-containing mobile phase additives are investigated using two QAC probe analytes. In all instances, the quaternary-ammonium-containing mobile phase additives perform better than the corresponding sodium-containing additives for effective QAC elution. These results indicate that the structure of the analogue ion, not just its formal charge, is important in the reversed-phase ion-pair chromatography of these compounds. The relative elution order of the QAC probe analytes is also influenced by the counter ions of the mobile phase additives, with bromide and dodecyl sulfate offering opposite elution orders.

Journal Article↗
PubMed2002

Resolution of tert-butyl-1-(2-methyinaphthyl)phosphine oxide using selectors identified from a chemical combinatorial library.

Resolution of racemic tert-butyl-1-(2-methylnaphthyl)-phosphine oxide 1, a chiral phosphorus compound, was achieved using selectors developed from a small peptide library. Separation factors as high as 3.2 were observed. The library consists of 81 peptide-based potential chiral selectors on polymeric synthesis resins. The linker needed to immobilize the identified chiral selectors onto silica gel proved important in the chiral separation; a longer linker provided a significantly higher separation factor in this study.

Chromatography, High Pressure Liquid↗
PubMed2002

Absolute configuration of tert-butyl-1-(2-methylnaphthyl)phosphine oxide.

The enantiomers of tert-butyl-1-(2-methylnaphthyl)phosphine oxide 1 have been separated using a homemade HPLC column and an analytical gradient system. Vibrational absorption and circular dichroism spectra for both enantiomers have been measured in CD2Cl2 and CH2Cl2 solutions in the 2000-900 cm(-1) region. The fully relaxed potential energy surface of (S)-tert-butyl-1-(2-methylnaphthyl)phosphine oxide, obtained using the B3LYP functional with a 6-31G basis set, indicated two stable conformers with their populations in a approximately 2:1 ratio. The vibrational absorption and VCD spectra are predicted for these two conformers using the B3LYP functional with a 6-31G basis set. The comparison of predicted and experimental spectra indicated that (+)-tert-butyl-1-(2-methylnaphthyl)phosphine oxide is in the (S)-configuration. This assignment is supported by the ab initio prediction of positive optical rotation for the most stable conformer with an (S)-configuration and the nonequivalence sense of the tert-butyl group chemical shift observed in the 1H NMR spectrum of this enantiomer measured in the presence of (+)-(S)-mandelic acid as a chiral solvating agent.

Chromatography, High Pressure Liquid↗
PubMed2002

Solvent effects on the screening of parallel combinatorial libraries for selectors for chiral chromatography.

The correlation between the resin-swelling property and the outcome of the crucial equilibration assay used in our parallel library screening method is investigated. It is found that the incorporation of CHCl3 (an effective swelling solvent for both the polystyrene and TentaGel resins) into the equilibration solvent leads to faster equilibration and thus shorter library screening time. The outcome of the equilibration experiment is also found to depend on the chemical nature of the solid base resins. It appears that polystyrene resin, which has a relatively inert surface, provides higher enantioselectivity than the polar TentaGel resin. The importance of a thoroughly swelled resin for the direct assay of functional groups on the resin is demonstrated.

Circular Dichroism↗
PubMedDate not supplied

Identification of affinity ligands for protein purification from synthetic chemical combinatorial libraries.

A method to screen combinatorial libraries for the development of selective ligands for protein affinity chromatographic purification is described. The method is based on the application of parallel combinatorial libraries, and it has several potential advantages. The screening procedure is simple and straightforward, and it does not require the chemical derivatization of the target proteins or even that the target protein be pure. The experiment can also be designed to select binders that are less likely to cause protein denaturation. Feasibility of this approach is demonstrated with a model study of the chromatographic purification of bovine albumin serum (BSA) and Avidin.

Combinatorial Chemistry Techniques↗