Identification of Synthetic Phosphatidylserine Translocases from a Combinatorial Library Prepared by Directed Split-and-Pool Synthesis

Orthogonal Combinatorial Raman Codes Enable Rapid High-Throughput-Out Library Screening of Cell-Targeting Ligands

High-throughput assays play an important role in the fields of drug discovery, genetic analysis, and clinical diagnostics. Although super-capacity coding strategies may facilitate labeling and detecting large numbers of targets in a single assay, practically, the constructed large-capacity codes have to be decoded with complicated procedures or are lack of survivability under the required reaction conditions. This challenge results in either inaccurate or insufficient decoding outputs. Here, we identified chemical-resistant Raman compounds to build a combinatorial coding system for the high-throughput screening of cell-targeting ligands from a focused 8-mer cyclic peptide library. The accurate in situ decoding results proved the signal, synthetic, and functional orthogonality for this Raman coding strategy. The orthogonal Raman codes allowed for a rapid identification of 63 positive hits at one time, evidencing a high-throughput-out capability in the screening process. We anticipate this orthogonal Raman coding strategy being generalized to enable efficient high-throughput-out screening of more useful ligands for cell targeting and drug discovery.

High throughput technology: approaches of research in homogeneous and heterogeneous catalysis

High throughput experimentation (HTE) approaches and the choice of the design of experiment (DoE) tools are discussed with regard to their convenience and applicability in homogeneous and heterogeneous catalysis as a concerted workflow. Much attention is given to diverse methodologies and strategies, which are fundamental for the experimental planning. For two target reactions in two case studies presented in this chapter, HTE methods were applied to create and evaluate catalyst libraries. A homogeneous catalyst case study is illustrated first, which deals with parallel synthesis and screening of organometallic catalysts in the polymerisation of ethylene. The second case study (heterogeneous catalysis) focuses on coherent synthesis and testing of dopant effects on the performance of oxidation catalysts in a reaction of transformation of n-butane to maleic anhydride. Supporting examples from the literature described here show that careful planning of libraries and test conditions is vital in high throughput experimentation in order to deliver meaningful results leading to performance improvements or disruptive new findings.

Facilitated phospholipid translocation in vesicles and nucleated cells using synthetic small molecule scramblases

A series of 16 synthetic scramblase candidates were prepared from a tris(aminoethyl)amine (TREN) scaffold and evaluated for ability to facilitate translocation of fluorescent phospholipid probes across vesicle membranes and endogenous phosphatidylserine across the plasma membrane of nucleated cells. More than half of the compounds were found to greatly accelerate phospholipid translocation in vesicles. However, they were generally unable to induce large increases in the amount of phosphatidylserine on the surface of nucleated mammalian cells, which contrasts with previous results using erythrocytes. Fluorescence microscopy showed that the synthetic scramblases are rapidly trafficked out of the cell plasma membrane and into the membranes of internal organelles. Future molecular designs of synthetic scramblases should focus on structures that are more amphiphilic, a structural feature that is expected to increase plasma membrane residence time.

New noninvasive methodology for real-time monitoring of lipid flip

A new methodology for the detection of lipid flip was developed. This methodology relies on the quenching of the fluorescence of the cascade-blue-labeled lipid through complex formation with a membrane-impermeable cyclen-tetranaphthalenethiourea synthetic receptor for this dye. The high affinity of the receptor to cascade-blue label allows the use of micromolar concentrations of this receptor during the experiment. At these low concentrations, the receptor does not interfere with the membrane integrity and, therefore, renders this new methodology less invasive to the model and cell membranes than commonly utilized 7-nitro-1,2,3-benzoxadiazol-4-yl (NBD)-dithionite methodology. Unlike with the NBD-dithionite assay, where the fluorescence quenching of the NBD group is achieved through its chemical modification, this new assay relies on the noncovalent interactions between cascade-blue label and the receptor. Therefore, the quenching can be reverted by either competitive displacement of the lipid-attached label with a water-soluble substrate or by enzymatic degradation of the receptor leading to the label release and fluorescence dequenching. We demonstrate that this new methodology is suitable for the study of lipid flip in both model spherical bilayer membranes and in-vitro experiments.

Bolaamphiphiles promote phospholipid translocation across vesicle membranes

A series of membrane-spanning bolaamphiphiles (molecules with two hydrophilic end groups connected by a hydrophobic linker) were prepared by a modular synthetic method and evaluated for their abilities to affect the dynamics of a surrounding bilayer membrane. The goal was to determine if the bolaamphiphiles promote the translocation of phospholipids across vesicle membranes. The bolaamphiphiles were incorporated at low levels (up to 5 mol %) in vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Inward translocation assays were performed using fluorescent, NBD-labeled phospholipid probes with phosphocholine (PC) or phosphoglycerol (PG) headgroups. The membrane-spanning bolaamphiphiles promote the translocation of both phospholipid probes in the order PG > PC, whereas shorter bolaamphiphiles (structures that must adopt a U-shape and keep both end groups in the same leaflet of the membrane), and regular amphiphiles with one hydrophilic end group, are inactive. These results are an exception to the rule-of-thumb that membrane-spanning bolaamphiphiles are inherently membrane-stabilizing molecules that inhibit all types of membrane transport.