Activation/Deactivation Free-Energy Profiles for the β₂‑Adrenergic Receptor: Ligand Modes of Action

We use enhanced-sampling simulations with an effective collective variable to study the activation of the β2-adrenergic receptor in the presence of ligands with different efficacy. The free-energy profiles are computed for the ligand-free (apo) receptor and binary (apo-receptor + G-protein α-subunit and receptor + ligand) and ternary complexes. The results are not only compatible with available experiments but also allow unprecedented structural insight into the nature of GPCR conformations along the activation pathway and their role in the activation mechanism. In particular, the simulations reveal an unexpected mode of action of partial agonists such as salmeterol and salbutamol that arises already in the binary complex without the G-protein. Specific differences in the polar interactions with residues in TM5, which are required to stabilize an optimal TM6 conformation that facilitates G-protein binding and receptor activation, play a major role in differentiating them from full agonists

Bromodomain Factor 5 as a Target for Antileishmanial Drug Discovery

Leishmaniases are a collection of neglected tropical diseases caused by kinetoplastid parasites in the genus Leishmania. Current chemotherapies are severely limited, and the need for new antileishmanials is of pressing international importance. Bromodomains are epigenetic reader domains that have shown promising therapeutic potential for cancer therapy and may also present an attractive target to treat parasitic diseases. Here, we investigate Leishmania donovani bromodomain factor 5 (LdBDF5) as a target for antileishmanial drug discovery. LdBDF5 contains a pair of bromodomains (BD5.1 and BD5.2) in an N-terminal tandem repeat. We purified recombinant bromodomains of L. donovani BDF5 and determined the structure of BD5.2 by X-ray crystallography. Using a histone peptide microarray and fluorescence polarization assay, we identified binding interactions of LdBDF5 bromodomains with acetylated peptides derived from histones H2B and H4. In orthogonal biophysical assays including thermal shift assays, fluorescence polarization, and NMR, we showed that BDF5 bromodomains bind to human bromodomain inhibitors SGC-CBP30, bromosporine, and I-BRD9; moreover, SGC-CBP30 exhibited activity against Leishmania promastigotes in cell viability assays. These findings exemplify the potential BDF5 holds as a possible drug target in Leishmania and provide a foundation for the future development of optimized antileishmanial compounds targeting this epigenetic reader protein

New Findings for the Composition and Structure of Ni Nanoparticles Protected with Organomercaptan Molecules

Here we explore the synthesis of alkanethiol-coated Ni NPs following the one-phase reaction method by Brust et al. The reduction of NiCl₂ with NaBH₄ in the presence of dodecanethiol (C₁₂SH) yields a complex product that is difficult to identify as illustrated in the figure of merit. We synthesized Ni­(II) dodecanethiolate (C₁₂S) (without the addition of NaBH₄) for comparison and performed an exhaustive characterization with TEM, HR-TEM, AFM, MFM, XPS, XRD, UV–vis, magnetism, and FT-IR. It is found that the organic coating is not quite a well-organized self-assembled monolayer (SAM) surrounding the Ni cluster as previously reported., XPS and XRD data show slight differences between both syntheses; however, Ni­(II) thiolate appears to be more stable than reduced Ni when exposed to ambient air, indicating the propensity of metallic Ni to oxidize. It has been shown that irradiating with TEM electrons over various metal thiolates leads to nanoparticle formation. We irradiated over Ni­(II) thiolate and observed no evidence of NP formation whereas irradiating a reduced Ni sample exhibited an ∼3.0 nm nanoparticle diameter. Magnetism studies showed a difference between both samples, indicating ferromagnetic character for the reduced Ni sample. According to our results, the product of the synthesis is comprised of ultrasmall metallic clusters embedded in some form of Ni­(II) C₁₂S. In this work, we open a discussion of the chemical nature of the core and the shell in the synthesis of Ni NPs protected with organomercaptan molecules

Slow-Binding Inhibition of <i>Mycobacterium tuberculosis</i> Shikimate Kinase by Manzamine Alkaloids

Tuberculosis represents a significant public health crisis. There is an urgent need for novel molecular scaffolds against this pathogen. We screened a small library of marine-derived compounds against shikimate kinase from <i>Mycobacterium tuberculosis</i> (<i>Mt</i>SK), a promising target for antitubercular drug development. Six manzamines previously shown to be active against <i>M. tuberculosis</i> were characterized as <i>Mt</i>SK inhibitors: manzamine A (<b>1</b>), 8-hydroxymanzamine A (<b>2</b>), manzamine E (<b>3</b>), manzamine F (<b>4</b>), 6-deoxymanzamine X (<b>5</b>), and 6-cyclohexamidomanzamine A (<b>6</b>). All six showed mixed noncompetitive inhibition of <i>Mt</i>SK. The lowest <i>K</i>_I values were obtained for <b>6</b> across all <i>Mt</i>SK–substrate complexes. Time-dependent analyses revealed two-step, slow-binding inhibition. The behavior of <b>1</b> was typical; initial formation of an enzyme–inhibitor complex (EI) obeyed an apparent <i>K</i>_I of ∼30 μM with forward (<i>k</i>₅) and reverse (<i>k</i>₆) rate constants for isomerization to an EI* complex of 0.18 and 0.08 min^–1, respectively. In contrast, <b>6</b> showed a lower <i>K</i>_I for the initial encounter complex (∼1.5 μM), substantially faster isomerization to EI* (<i>k</i>₅ = 0.91 min^–1), and slower back conversion of EI* to EI (<i>k</i>₆ = 0.04 min^–1). Thus, the overall inhibition constants, <i>K</i>_I*, for <b>1</b> and <b>6</b> were 10 and 0.06 μM, respectively. These findings were consistent with docking predictions of a favorable binding mode and a second, less tightly bound pose for <b>6</b> at <i>Mt</i>SK. Our results suggest that manzamines, in particular <b>6</b>, constitute a new scaffold from which drug candidates with novel mechanisms of action could be designed for the treatment of tuberculosis by targeting <i>Mt</i>SK

Breakthrough infections in MPN-COVID vaccinated patients

we have provided quantitative estimates of SARSCoV2 infections in vaccinated patients with MPN revealing a higher rate of severe disease than in the normal population. Compared to unvaccinated, a trend for a lower reinfection rate was found in patients with hybrid vaccination

Second versus first wave of COVID-19 in patients with MPN

Second versus first wave of COVID-19 in patients with MP

Piperazin-1-ylpyridazine Derivatives Are a Novel Class of Human dCTP Pyrophosphatase 1 Inhibitors

The dCTP pyrophosphatase 1 (dCTPase) is a nucleotide pool “housekeeping” enzyme responsible for the catabolism of canonical and noncanonical nucleoside triphosphates (dNTPs) and has been associated with cancer progression and cancer cell stemness. We have identified a series of piperazin-1-ylpyridazines as a new class of potent dCTPase inhibitors. Lead compounds increase dCTPase thermal and protease stability, display outstanding selectivity over related enzymes and synergize with a cytidine analogue against leukemic cells. This new class of dCTPase inhibitors lays the first stone toward the development of drug-like probes for the dCTPase enzyme