Molecular Swings as Highly Active Ion Transporters.

Ions are transported across membrane mostly via carrier or channel mechanisms. Herein, a unique class of molecular-machine-inspired membrane transporters, termed molecular swings is reported that utilize a previously unexplored swing mechanism for promoting ion transport in a highly efficient manner. In particular, the molecular swing, which carries a 15-crown-5 unit as the ion-binding and transporting unit, exhibits extremely high ion-transport activities with EC50 values of 46 nm (a channel:lipid molar ratio of 1:4800 or 0.021 mol % relative to lipid) and 110 nm for K+ and Na+ ions, respectively. Remarkably, such ion transport activities remain high in a cholesterol-rich environment, with EC50 values of 130 (0.045 mol % relative to lipid/cholesterol) and 326 nm for K+ and Na+ ions, respectively.

An efficient strategy to enhance binding affinity and specificity of a known isozyme inhibitor.

The binding profile of a known inhibitor, benzenesulfonamide, against a family of carbonic anhydrase isozymes was efficiently enhanced via high-throughput screening of customized combinatorial one-bead-one-compound peptide libraries modified with the inhibitor molecule. The screening of the conjugate libraries recognized subtle variations in the microenvironments of the target enzyme and thus facilitated the identification of short peptide sequences that bind selectively to a close proximity of the active site. The identified peptide portions contributed significantly to the overall binding of the conjugate peptides with greatly enhanced affinity as well as improved specificity towards the target isozyme. The interactions between the inhibitors and the isozymes were validated by surface plasmon resonance (SPR), pull-down assay and enzymatic activity measurement. This high-throughput approach proved useful and efficient to enhance the binding profile of known inhibitors and may apply to developing effective inhibitors for a wide range of isozyme families.

Recent Advances in Synthesis and Identification of Cyclic Peptides for Bioapplications.

Cyclic peptides, owing to their good stability, high resistance to exo- and to some extent endo-peptidases, enhanced binding affinity and selectivity towards target biomolecules, are actively investigated as biochemical tools and therapeutic agents. In this review, we discuss various commonly utilized synthetic strategies for cyclic peptides and peptoids (peptidomimetics), their important screening methods to identify the bioactive cyclic peptides and peptoids such as combinatorial beadbased peptide library, phage display, mRNA display etc. and recent advances in their applications as bioactive compounds. Lastly, we also make a summary and provide an outlook of the research area.

Target identification of natural and traditional medicines with quantitative chemical proteomics approaches.

Natural and traditional medicines, being a great source of drugs and drug leads, have regained wide interests due to the limited success of high-throughput screening of compound libraries in the past few decades and the recent technology advancement. Many drugs/bioactive compounds exert their functions through interaction with their protein targets, with more and more drugs showing their ability to target multiple proteins, thus target identification has an important role in drug discovery and biomedical research fields. Identifying drug targets not only furthers the understanding of the mechanism of action (MOA) of a drug but also reveals its potential therapeutic applications and adverse side effects. Chemical proteomics makes use of affinity chromatography approaches coupled with mass spectrometry to systematically identify small molecule-protein interactions. Although traditional affinity-based chemical proteomics approaches have made great progress in the identification of cellular targets and elucidation of MOAs of many bioactive molecules, nonspecific binding remains a major issue which may reduce the accuracy of target identification and may hamper the drug development process. Recently, quantitative proteomics approaches, namely, metabolic labeling, chemical labeling, or label-free approaches, have been implemented in target identification to overcome such limitations. In this review, we will summarize and discuss the recent advances in the application of various quantitative chemical proteomics approaches for the identification of targets of natural and traditional medicines.

Investigating fluorescent dyes in fluorescence-assisted screenings.

Screening of bead-based peptide libraries against fluorescent dye-labeled target proteins was found to be significantly influenced by the dye characteristics. Commercially available red fluorescent dyes with net negative charges adversely showed strong interactions with library beads. The introduction of zwitterionic dyes significantly reduced the unwanted interactions, which sheds light upon using the right fluorescent probe for acquisition of reliable results in various fluorescence-assisted applications.