Open Port Interface for Coupling Capillary Electrophoresis and Mass Spectrometry: Performance Evaluation for Capillary Isoelectric Focusing.

Capillary electrophoresis (CE) combined with mass spectrometry (MS) is a powerful analytical technique that utilizes the resolving power of CE and the mass-detection capabilities of MS. In many cases, CE is coupled to MS via a sheath-flow interface (SFI). This interface has a simple design and can be easily constructed; however, it often suffers from issues such as MS signal suppression, interference of MS and CE electrical circuits, and the inability to set an optical point of detection close to the capillary end due to the specific design of the coupling union.

Quantitative Characterization of Partitioning in Selection of DNA Aptamers for Protein Targets by Capillary Electrophoresis.

Partitioning of protein-DNA complexes from protein-unbound DNA is a key step in selection of DNA aptamers. Conceptually, the partitioning step is characterized by two parameters: transmittance for protein-bound DNA (binders) and transmittance for unbound DNA (nonbinders). Here, we present the first study to reveal how these transmittances depend on experimental conditions; such studies are pivotal to the effective planning and control of selection.

How to Develop and Prove High-Efficiency Selection of Ligands from Oligonucleotide Libraries: A Universal Framework for Aptamers and DNA-Encoded Small-Molecule Ligands.

Screening molecular libraries for ligands capable of binding proteins is widely used for hit identification in the early drug discovery process. Oligonucleotide libraries provide a very high diversity of compounds, while the combination of the polymerase chain reaction and DNA sequencing allow the identification of ligands in low copy numbers selected from such libraries. Ligand selection from oligonucleotide libraries requires mixing the library with the target followed by the physical separation of the ligand-target complexes from the unbound library.

Spherical-Shape Assumption for Protein-Aptamer Complexes Facilitates Prediction of Their Electrophoretic Mobility.

DNA aptamers are single-strand DNA (ssDNA) capable of selectively and tightly binding a target molecule. Capillary electrophoresis-based selection of aptamers for protein targets requires the knowledge of electrophoretic mobilities of protein-aptamer complexes, while measuring these mobilities requires having the aptamers. Here, we report on breaking this vicious circle.

Aptamer facilitated purification of functional proteins.

DNA aptamers are attractive capture probes for affinity chromatography since, in contrast to antibodies, they can be chemically synthesized and, in contrast to tag-specific capture probes (such as Nickel-NTA or Glutathione), they can be used for purification of proteins free of genetic modifications (such as His or GST tags). Despite these attractive features of aptamers as capture probes, there are only a few reports on aptamer-based protein purification and none of them includes a test of the purified protein's activity, thus, leaving discouraging doubts about method's ability to purify proteins in their active state. The goal of this work was to prove that aptamers could facilitate isolation of active proteins.