Discovery and Characterization of VU0542270, the First Selective Inhibitor of Vascular Kir6.1/SUR2B KATP Channels.

Vascular smooth muscle KATP channels critically regulate blood flow and blood pressure by modulating vascular tone and therefore represent attractive drug targets for treating several cardiovascular disorders. However, the lack of potent inhibitors that can selectively inhibit Kir6.1/SUR2B (vascular KATP) over Kir6.2/SUR1 (pancreatic KATP) has eluded discovery despite decades of intensive research. We therefore screened 47,872 chemically diverse compounds for novel inhibitors of heterologously expressed Kir6.1/SUR2B channels. The most potent inhibitor identified in the screen was an N-aryl-N'-benzyl urea compound termed VU0542270. VU0542270 inhibits Kir6.1/SUR2B with an IC50 of approximately 100 nM but has no apparent activity toward Kir6.2/SUR1 or several other members of the Kir channel family at doses up to 30 µM (>300-fold selectivity). By expressing different combinations of Kir6.1 or Kir6.2 with SUR1, SUR2A, or SUR2B, the VU0542270 binding site was localized to SUR2. Initial structure-activity relationship exploration around VU0542270 revealed basic texture related to structural elements that are required for Kir6.1/SUR2B inhibition. Analysis of the pharmacokinetic properties of VU0542270 showed that it has a short in vivo half-life due to extensive metabolism. In pressure myography experiments on isolated mouse ductus arteriosus vessels, VU0542270 induced ductus arteriosus constriction in a dose-dependent manner similar to that of the nonspecific KATP channel inhibitor glibenclamide. The discovery of VU0542270 provides conceptual proof that SUR2-specific KATP channel inhibitors can be developed using a molecular target-based approach and offers hope for developing cardiovascular therapeutics targeting Kir6.1/SUR2B. SIGNIFICANCE STATEMENT: Small-molecule inhibitors of vascular smooth muscle KATP channels might represent novel therapeutics for patent ductus arteriosus, migraine headache, and sepsis; however, the lack of selective channel inhibitors has slowed progress in these therapeutic areas. Here, this study describes the discovery and characterization of the first vascular-specific KATP channel inhibitor, VU0542270.

Synthesis and SAR of a novel Kir6.2/SUR1 channel opener scaffold identified by HTS.

Kir6.2/SUR1 is an ATP-regulated potassium channel that acts as an intracellular metabolic sensor, controlling insulin and appetite-stimulatory neuropeptides secretion. In this Letter, we present the SAR around a novel Kir6.2/SUR1 channel opener scaffold derived from an HTS screening campaign. New series of compounds with tractable SAR trends and favorable potencies are reported.

Asymmetric Synthesis of Lysergic Acid via an Intramolecular (3+2) Dipolar Cycloaddition/Ring-Expansion Sequence.

An effective, potentially scalable asymmetric synthesis of lysergic acid, a core component of the ergot alkaloid family, is reported. The synthesis features the strategic combination of an intramolecular azomethine ylide cycloaddition and Cossy-Charette ring expansion to assemble the target's C- and D-rings. Simple functional group manipulation produced a compound that had been converted to lysergic acid in four steps, thus constituting a formal synthesis of the natural product. The strategy may be used to prepare novel ergot analogues that include unnatural antipodes and may be more amenable to analogue generation relative to prior approaches.

Site-Specific Synthesis of Cysteine-Bridged Glycoproteins via Expressed Protein Glycoligation.

Site-specific glycosylation of a functional recombinant protein thioester is reported. The thioester functionalized protein sfGFP-Y151ThioD, prepared by genetic code expansion, underwent native chemical ligation with the cysteine-conjugated glycans H-Cys-NH-GlcNAc and H-Cys-NH-(GlcNAc)2(Man)3 to give the corresponding cysteine-bridged glycoproteins. The intact glycoproteins, which retained their fluorescence, were characterized by top-down mass spectrometry and gel electrophoresis. The bridging cysteine provided a convenient handle for affinity chromatography purification of the glycoproteins via a removable biotin tag. Given the influence that specific glycoforms can have on a protein's function, the ability to attach a homogeneous glycan to an intact protein in a functional group controlled yet sequon-independent manner could find widespread application. These preliminary results set the stage for development of the expressed protein glycoligation (EPG) concept.

Design and Synthesis of Pyrrolidine-based Fragments That Sample Three-dimensional Molecular Space.

Fragment-based drug discovery (FBDD) is a well-established technology for lead compound generation in drug discovery. As this technology has evolved, the design of fragments for screening has also evolved to engender not just an understanding of the role of modulating the physicochemical properties of fragments (Rule of Three, Ro3) but also the importance and implications of incorporating shape and, in particular, 3D characteristics into fragments. Herein, we describe the design and synthesis of pyrrolidine-based fragments with good fragment-like (Ro3) physicochemical properties that effectively sample three-dimensional molecular space.

Rice bran nanofiber composites for stabilization of phytase.

This study explores the potential application of rice bran (agro waste) to nano-encapsulate phytase, which is a thermally unstable biologically active enzyme. Rice bran was converted to nanofibers (20-50 nm in diameter) using electrospinning. After optimizing the pH, viscosity, voltage and the distance between electrodes for electrospinning, phytase enzyme was encapsulated and the fibers were cross-linked using sodium tripolyphosphate. Thermal stability of phytase enzyme was improved by 90 °C when they are encapsulated and cross-linked with sodium tripolyphosphate. The activity of the phytase enzyme was monitored at different temperatures. The activity of the pure enzyme was lost at 80 °C while the enzyme encapsulated into nanofibers demonstrated the activity up to 170 °C. This study opens up many opportunities for nanotechnology value addition to many waste materials and also to improve the properties of a range of biomaterials through a sustainable approach.

Urea-Hydroxyapatite Nanohybrids for Slow Release of Nitrogen.

While slow release of chemicals has been widely applied for drug delivery, little work has been done on using this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by in situ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.