Synthesis of chiral α-amino acids Pd(ii)-catalyzed enantioselective C-H arylation of α-aminoisobutyric acid.

Non-natural chiral α,α-disubstituted α-amino acids (α,α-AAs) constitute an attractive α-aminoisobutyric acid (Aib) replacement for improving bioavailability of linear peptides as therapeutics due to the ability of these amino acids to induce the peptides to form helical structures. Enantioselective β-C(sp)-H arylation of Aib could potentially provide a versatile one-step strategy for accessing diverse α,α-AAs, but the installation and removal of external directing groups was found in our previously reported work to reduce the efficiency of this approach. Herein we report a Pd(ii)-catalyzed enantioselective C-H arylation of -phthalyl-protected Aib enabled by a -2,6-difluorobenzoyl aminoethyl phenyl thioether (MPAThio) ligand, affording α,α-AAs with up to 72% yield and 98% ee.

Quantifying Siglec-sialylated ligand interactions: a versatile F-T CPMG filtered competitive NMR displacement assay.

Sialic-acid-binding immunoglobulin-like lectins (Siglecs) are integral cell surface proteins crucial for the regulation of immune responses and the maintenance of immune tolerance through interactions with sialic acids. Siglecs recognize sialic acid moieties, usually found at the end of -glycan and -glycan chains. However, the different Siglecs prefer diverse presentations of the recognized sialic acid, depending on the type of glycosidic linkage used to link to the contiguous Gal/GalNAc or sialic acid moieties.

Direct observation of peptide hydrogel self-assembly.

The characterization of self-assembling molecules presents significant experimental challenges, especially when associated with phase separation or precipitation. Transparent window infrared (IR) spectroscopy leverages site-specific probes that absorb in the "transparent window" region of the biomolecular IR spectrum. Carbon-deuterium (C-D) bonds are especially compelling transparent window probes since they are non-perturbative, can be readily introduced site selectively into peptides and proteins, and their stretch frequencies are sensitive to changes in the local molecular environment.

Chaperones mainly suppress primary nucleation during formation of functional amyloid required for bacterial biofilm formation.

Unlike misfolding in neurodegenerative diseases, aggregation of functional amyloids involved in bacterial biofilm, CsgA () and FapC (), is carefully regulated. However, it is unclear whether functional aggregation is inhibited by chaperones targeting pathological misfolding and if so by what mechanism. Here we analyze how four entirely different human chaperones or protein modulators (transthyretin, S100A9, Bri2 BRICHOS and DNAJB6) and bacterial CsgC affect CsgA and FapC fibrillation.

Directed Markovnikov hydroarylation and hydroalkenylation of alkenes under nickel catalysis.

We report a full account of our research on nickel-catalyzed Markovnikov-selective hydroarylation and hydroalkenylation of non-conjugated alkenes, which has yielded a toolkit of methods that proceed under mild conditions with alkenyl sulfonamide, ketone, and amide substrates. Regioselectivity is controlled through catalyst coordination to the native Lewis basic functional groups contained within these substrates. To maximize product yield, reaction conditions were fine-tuned for each substrate class, reflecting the different coordination properties of the directing functionality.

Merging C(sp)-H activation with DNA-encoding.

DNA-encoded library (DEL) technology has the potential to dramatically expedite hit identification in drug discovery owing to its ability to perform protein affinity selection with millions or billions of molecules in a few experiments. To expand the molecular diversity of DEL, it is critical to develop different types of DNA-encoded transformations that produce billions of molecules with distinct molecular scaffolds. Sequential functionalization of multiple C-H bonds provides a unique avenue for creating diversity and complexity from simple starting materials.

Regulatory mechanisms of mitochondrial BK channels.

The mitochondrial BK channel (mitoBK) is a splice variant of plasma membrane BK (Maxi-K, BK, Slo1, K1.1). While a high-resolution structure of mitoBK is not available yet, functional and structural studies of the plasma membrane BK have provided important clues on the gating of the channel by voltage and Ca, as well as the interaction with auxiliary subunits.

Controlling cyclization pathways in palladium(ii)-catalyzed intramolecular alkene hydro-functionalization substrate directivity.

We report a series of palladium(ii)-catalyzed, intramolecular alkene hydrofunctionalization reactions with carbon, nitrogen, and oxygen nucleophiles to form five- and six-membered carbo- and heterocycles. In these reactions, the presence of a proximal bidentate directing group controls the cyclization pathway, dictating the ring size that is generated, even in cases that are disfavored based on Baldwin's rules and in cases where there is an inherent preference for an alternative pathway. DFT studies shed light on the origins of pathway selectivity in these processes.

Recent developments in nickel-catalyzed intermolecular dicarbofunctionalization of alkenes.

Nickel-catalyzed three-component alkene difunctionalization has rapidly emerged as a powerful tool for forging two C-C bonds in a single reaction. Building upon the powerful modes of bond construction in traditional two-component cross-coupling, various research groups have demonstrated the versatility of nickel in enabling catalytic 1,2-dicarbofunctionalization using a wide range of carbon-based electrophiles and nucleophiles and in a fully intermolecular fashion. Though this area has emerged only recently, the last few years have witnessed a proliferation of publications on this topic, underscoring the potential of this strategy to develop into a general platform that offers high regio- and stereoselectivity.

GABA receptor allosteric modulators exhibit pathway-dependent and species-selective activity.

Positive modulation of the GABA receptor (GABAR) represents a potentially useful therapeutic approach for the treatment of nicotine addiction. The positive allosteric modulators (PAMs) of GABAR GS39783 and BHF177 enhance GABA-stimulated [S]GTP S-binding, and have shown efficacy in a rodent nicotine self-administration procedure reflecting aspects of nicotine dependence. Interestingly, the structural related analog, NVP998, had no effect on nicotine self-administration in rats despite demonstrating similar pharmacokinetic properties.

Methamphetamine reduces expression of caveolin-1 in the dorsal striatum: Implication for dysregulation of neuronal function.

Role of striatal dopamine D1 receptors (D1Rs) in methamphetamine (Meth) taking and seeking is recognized from contingent Meth self-administration studies. For example, Meth increases levels of D1Rs in the dorsal striatum in animal models of Meth addiction, and blockade of striatal D1Rs decreased responding for Meth and reduced Meth priming-induced drug seeking. However, the mechanism underlying enhanced expression of striatal D1Rs in animals self-administering Meth is unknown and is hypothesized to involve maladaptive intracellular signal transduction mechanism via hyperphosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2).

Site-specifically arraying small molecules or proteins on DNA using an expanded genetic alphabet.

A class of replicable unnatural DNA base pairs formed between d5SICS and either dMMO2, dDMO, or dNaM were developed. To explore the use of these pairs to produce site-specifically labeled DNA, the synthesis of a variety of derivatives bearing propynyl groups, an analysis of their polymerase-mediated replication, and subsequent site-specific modification of the amplified DNA by Click chemistry is reported. With the d5SICS scaffold a propynyl ether linker is accommodated better than its aliphatic analogue, but not as well as the protected propargyl amine linker explored previously.

α-Ketoheterocycle-based Inhibitors of Fatty Acid Amide Hydrolase (FAAH).

A summary of the initial discovery and characterization of the enzyme fatty acid amide hydrolase (FAAH), and the subsequent advancement of an important class of competitive, reversible, potent and selective inhibitors is presented. Initially explored using substrate-inspired inhibitors bearing electrophilic carbonyls, the examination of α-ketoheterocyle-based inhibitors of FAAH with the benefit of a unique activity-based protein-profiling (ABPP)-based proteome-wide selectivity assay, a powerful in vivo biomarker-based in vivo screen, and subsequent retrospective X-ray co-crystal structures with the enzyme, is summarized. These efforts defined the impact of the central activating heterocycle and its key substituents, provided key simplifications in the C2 acyl side chain and clear interpretations for the unique role and subsequent optimization of the central activating heterocycle, and established the basis for the recent further conformational constraints in the C2 acyl side chain, providing potent, long-acting, orally-active FAAH inhibitors.

Photophysics Applied to Cavitands and Capsules.

The use of light as a stimulus to control functional materials or nano-devices is appealing as it provides convenient control of triggering events where and when they are desired without introducing extra components to the system. Many photophysical and photochemical processes are extremely fast, giving rise to nearly instantaneous onset of events. However, these fast processes can be challenging to engineer into chemical systems.

Characterization of the chondrocyte actin cytoskeleton in living three-dimensional culture: response to anabolic and catabolic stimuli.

The actin cytoskeleton is a dynamic network required for intracellular transport, signal transduction, movement, attachment to the extracellular matrix, cellular stiffness and cell shape. Cell shape and the actin cytoskeletal configuration are linked to chondrocyte phenotype with regard to gene expression and matrix synthesis. Historically, the chondrocyte actin cytoskeleton has been studied after formaldehyde fixation--precluding real-time measurements of actin dynamics, or in monolayer cultured cells.

Natural killer T cell recognition of lipid antigens.

Natural killer T cells recognize lipid antigens in the context of CD1 molecules. Recent publications show that this mode of recognition differs substantially from that of classic T-cell receptor peptide-major histocompatibility complex interaction.

Shape complementarity of protein-protein complexes at multiple resolutions.

Biological complexes typically exhibit intermolecular interfaces of high shape complementarity. Many computational docking approaches use this surface complementarity as a guide in the search for predicting the structures of protein-protein complexes. Proteins often undergo conformational changes to create a highly complementary interface when associating.

XCMS2: processing tandem mass spectrometry data for metabolite identification and structural characterization.

Mass spectrometry based metabolomics represents a new area for bioinformatics technology development. While the computational tools currently available such as XCMS statistically assess and rank LC-MS features, they do not provide information about their structural identity. XCMS(2) is an open source software package which has been developed to automatically search tandem mass spectrometry (MS/MS) data against high quality experimental MS/MS data from known metabolites contained in a reference library (METLIN).

PRR7 protein levels are regulated by light and the circadian clock in Arabidopsis.

Interlocking transcriptional loops and regulated protein degradation are the principal mechanisms involved in the generation of self-sustaining circadian rhythms in many organisms. In Arabidopsis the first proposed regulatory transcriptional loop involved the transcription factors CIRCADIAN CLOCK ASSOCIATED (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) and the pseudo-response regulator TIMING OF CHLOROPHYLL A/B BINDING PROTEIN (TOC1/PRR1). Recent findings indicate that the TOC1 homologues PRR7 and PRR9 might also be involved in transcriptional regulatory loops with CCA1 and LHY.

Structural basis for cooperative transcription factor binding to the CBP coactivator.

Regulation of transcription requires interactions between transcriptional activators and transcriptional co-activator CREB binding protein (CBP). The KIX domain of CBP can bind simultaneously to two different proteins, providing an additional mechanism for transcriptional regulation. Here we describe the solution structure of the ternary complex formed by cooperative binding of activation domains from the c-Myb and mixed lineage leukemia (MLL) transcription factors to the KIX domain.

Antibody-catalyzed oxidative degradation of nicotine using riboflavin.

Tobacco abuse remains a major cause of death worldwide despite ample evidence linking nicotine to various disease states. Consequently, immunopharmacotherapeutic approaches for the treatment of nicotine abuse have received increasing attention. Although a number of nicotine-binding antibodies have been disclosed, no antibody catalysts exist which efficiently degrade nicotine into pharmacologically inactive substances.