Characterization of New DNA Aptamers for Anti-HIV-1 Reverse Transcriptase

HIV-1 RT is a necessary enzyme for retroviral replication, which is the main target for antiviral therapy against AIDS. Effective anti-HIV-1 RT drugs are divided into two groups; nucleoside inhibitors (NRTI) and non-nucleoside inhibitors (NNRTI), which inhibit DNA polymerase. In this study, new DNA aptamers were isolated as anti-HIV-1 RT inhibitors. The selected DNA aptamer (WT62) presented with high affinity and inhibition against wild-type (WT) HIV-1 RT and gave a KD value of 75.10±0.29 nM and an IC₅₀ value of 84.81±8.54 nM. Moreover, WT62 decreased the DNA polymerase function of K103 N/Y181 C double mutant (KY) HIV-1 RT by around 80 %. Furthermore, the ITC results showed that this aptamer has small binding enthalpies with both WT and KY HIV-1 RTs through which the complex might form a hydrophobic interaction or noncovalent bonding. The NMR result also suggested that the WT62 aptamer could bind with both WT and KY mutant HIV-1 RTs at the connection domain.     

LEGO‐Inspired Drug Design: Unveiling a Class of Benzo[d]thiazoles Containing a 3,4‐Dihydroxyphenyl Moiety as Plasma Membrane H+‐ATPase Inhibitors

The fungal plasma membrane H⁺‐ATPase (Pma1p) is a potential target for the discovery of new antifungal agents. Surprisingly, no structure–activity relationship studies for small molecules targeting Pma1p have been reported. Herein, we disclose a LEGO‐inspired fragment assembly strategy for the design, synthesis, and discovery of benzo[d]thiazoles containing a 3,4‐dihydroxyphenyl moiety as potential Pma1p inhibitors. A series of 2‐(benzo[d]thiazol‐2‐ylthio)‐1‐(3,4‐dihydroxyphenyl)ethanones was found to inhibit Pma1p, with the most potent IC₅₀ value of 8 μm in an in vitro plasma membrane H⁺‐ATPase assay. These compounds were also found to strongly inhibit the action of proton pumping when Pma1p was reconstituted into liposomes. 1‐(3,4‐Dihydroxyphenyl)‐2‐((6‐(trifluoromethyl)benzo[d]thiazol‐2‐yl)thio)ethan‐1‐one (compound 38 ) showed inhibitory activities on the growth of Candida albicans and Saccharomyces cerevisiae, which could be correlated and substantiated with the ability to inhibit Pma1p in vitro.     

Facile Rh-C Bond Cleavage of Rhodium(III) Benzyl Porphyrin Complex in DMSO with Strong Bases

Rhodium-carbon bond cleavage represents an essential step for small molecule activation and transformation by rhodium porphyrin complexes. This article reports on a new method for the cleavage of porphyrin rhodium(III)-carbon bonds in DMSO solvent with strong bases. UV-Vis, in situ ¹H NMR spectrum and GC-MS analysis confirmed generation of rhodium(I) species and monodeuterated toluene. Mechanistic studies revealed that strongly reducing CD₃SOCD₂⁻, formed in situ from DMSO-d₆ and strong bases, promoted Rh-C bond cleavage.     

N‐Phenylbenzamides as Potent Inhibitors of the Mitochondrial Permeability Transition Pore

Persistent opening of the mitochondrial permeability transition pore (PTP), an inner membrane channel, leads to mitochondrial dysfunction and renders the PTP a therapeutic target for a host of life‐threatening diseases. Herein, we report our effort toward identifying small‐molecule inhibitors of this target through structure–activity relationship optimization studies, which led to the identification of several potent analogues around the N‐phenylbenzamide compound series identified by high‐throughput screening. In particular, compound 4 (3‐(benzyloxy)‐5‐chloro‐N‐(4‐(piperidin‐1‐ylmethyl)phenyl)benzamide) displayed noteworthy inhibitory activity in the mitochondrial swelling assay (EC₅₀=280 nm ), poor‐to‐very‐good physicochemical as well as in vitro pharmacokinetic properties, and conferred very high calcium retention capacity to mitochondria. From the data, we believe compound 4 in this series represents a promising lead for the development of PTP inhibitors of pharmacological relevance.     

Targeting tumour proliferation with a small-molecule inhibitor of AICAR transformylase homodimerization

Aminoimidazole carboxamide ribonucleotide transformylase/ inosine monophosphate cyclohydrolase (ATIC) is a bifunctional homodimeric enzyme that catalyzes the last two steps of de novo purine biosynthesis. Homodimerization of ATIC, a protein–protein interaction with an interface of over 5000 Ų, is required for its aminoimidazole carboxamide ribonucleotide (AICAR) transformylase activity, with the active sites forming at the interface of the interacting proteins. Here, we report the development of a small‐molecule inhibitor of AICAR transformylase that functions by preventing the homodimerization of ATIC. The compound is derived from a previously reported cyclic hexapeptide inhibitor of AICAR transformylase (with a K_i of 17 μM ), identified by high‐throughput screening. The active motif of the cyclic peptide is identified as an arginine‐tyrosine dipeptide, a capped analogue of which inhibits AICAR transformylase with a K_i value of 84 μM . A library of nonnatural analogues of this dipeptide was designed, synthesized, and assayed. The most potent compound inhibits AICAR transformylase with a K_i value of 685 nM , a 25‐fold improvement in activity from the parent cyclic peptide. The potential for this AICAR transformylase inhibitor in cancer therapy was assessed by studying its effect on the proliferation of a model breast cancer cell line. Using a nonradioactive proliferation assay and live cell imaging, a dose‐dependent reduction in cell numbers and cell division rates was observed in cells treated with our ATIC dimerization inhibitor.     

The Identification of a Novel Natural Activator of p300 Histone Acetyltranferase Provides New Insights into the Modulation Mechanism of this Enzyme

Many severe human pathologies are related to alterations of the fine balance between histone acetylation and deacetylation; because not all such diseases involve hypoacetylation, but also hyperacetylation, compounds able to enhance or repress the activities of histone acetyltransferases (HATs) could be promising therapeutic agents. We evaluated in vitro and in cell the ability of eleven natural polyisoprenylated benzophenone derivatives to modulate the HAT activity of p300/CBP, an enzyme that plays a pivotal role in a variety of cellular processes. Some of the tested compounds bound efficiently to the p300/CBP protein: in particular, guttiferone A, guttiferone E and clusianone inhibit its HAT activity, whereas nemorosone showed a surprising ability to activate the enzyme. The ability of nemorosone to penetrate cell membranes and modulate histone acetylation into the cell together with its high affinity for the p300/CBP enzyme made this compound a suitable lead for the design of optimized anticancer drugs. Besides, the studies performed at a cellular and molecular level on both the inhibitors and the activator provided new insights into the modulation mechanism of p300/CBP by small molecules.     

Molecular weight distribution of polyethylene terephthalate in homogeneous,continuous-flow-stirred tank reactors

Poly(ethylene terephthalate) (PET) formation in homogeneous, continuous-flow-stirred tank reactors (HCSTRs) operating at steady state has been simulated. The feed to the reactor is assumed to consist of the monomer bis-(hydroxyethyl) terephthalate and monofunctional compound (MF₁) cetyl alcohol. The overall polymerization is assumed to consist of the polycondensation, reaction with monofunctional compounds, redistribution, and cyclization reactions. At a given time, the reaction mass consists of polyester molecules (P_n), polyester molecules with an ending of molecules of monofunctional compound (MF_n), and cyclic polymers (C_n). A mass balance for each of these species in the reactor gives rise to a set of algebraic equations to be solved simultaneously. The MWD calculations show that the redistribution reaction plays a major role and cannot be ignored, This result is in contrast lo the observation for semi-batch reactors, for which redistribution becomes important when the cyclization reaction is included. For the same residence times of semi-batch and HCSTRs, the latter gives considerably lower-number average molecular weight, N_av, and polydispersity index, ρ. However, for the same conversions, the ρ for CSTR is higher. The concentration of the monofurctional compound, [MF₁]₀, in the feed and the reactor temperature both influence ρ, but the effect is small within the range studied.     

Condensation reactions of phenolic resins. VI. Dependence of the molecular association of 2,4,6‐trihydroxymethylphenol on the concentration in an aqueous alkaline medium

The concentration dependence of the molecular association of 2,4,6‐trihydroxymethylphenol (THMP) as a model compound for phenol–formaldehyde resin was studied. ¹³C‐NMR spin–lattice relaxation time (T₁) measurements indicated that the molecular interactions were influenced by the concentration of THMP. Plots of T₁ versus the concentration revealed an inflection point around 1.2 mol/L. Molecular orbital calculations of the THMP molecules implied the following features of the molecular interactions: in the concentration range below 1.0 mol/L, THMP existed as a single molecule, and then at a higher concentration, self‐association started. At concentrations higher than 1.5mol/L, almost all the THMP molecules were bimolecularly associated, and the formation of larger clusters was initiated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2849–2854, 2007     

α-Multistriatin: The First Total Synthesis of a Natural Product via Antibody Catalysis

The relevance of antibody catalysis to synthetic organic chemistry is demonstrated here by an efficient total synthesis of (–)-α-multistriatin, the aggregation pheromone of the European elm bark beetle, Scolytus multistriatus, which is the principal vector of the Dutch elm disease, responsible for the severe devastation of the elm population in Europe and North America. The key step in our synthesis of this natural product is an antibody-catalyzed, enantioselective protonolysis of an enol ether to produce a branched ketone. The latter is obtained with an (S) configuration in greater than 99% enantiomeric excess. Catalysis follows Michaelis-Menten kinetics (K_m = 230 μM, k_cat = 0.36 min⁻¹) and useful rate enhancement (k_cat/k_un = 65,000 at pH 6.5). This abzymic step is followed by twelve chemical steps, with all four asymmetric centers originating from the chirality achieved in the antibody-catalyzed reaction. That specific step is a unique example of a chemical transformation which is difficult to achieve either by an available synthetic methodology or via catalysis with a known enzyme. The synthetic pheromone has been checked in field experiments and found as active as the naturally occurring compound in attracting the European elm bark beetles.     

Electrochemical oxidation of aryl cycloheptatrienes

The electrochemical oxidation of various substituted aryl cycloheptatrienes and cyclohepta‐1,3,5‐triene, the parent compound, in acetonitrile is investigated with the aid of cyclic voltammetry (CV), experiments at the rotating ring disk electrode (RRDE) and controlled potential electrolysis. 1‐(p‐methoxyphenyl)‐cycloheptatriene 2c , 1‐ and 3‐(p‐di‐methylaminophenyl)‐cycloheptatriene 2d , 3d are converted by anodic oxidation into the radical cations the main reaction of which is not the deprotonation. According to the proposed mechanism the electrochemical oxidation proceeds along the radical cation dimerization. The dimer cations ( 1 ₂²⁺) decompose under deprotonation into tropylium ions 4 and starting compound. In the case of 1‐(p‐dimethylaminophenyl)‐cycloheptatriene 2d the deprotonation reaction can compete with the dimerization. The oxidation of the cycloheptatriene compounds is kinetically controlled by the homogeneous chemical steps rather than by the initial electron transfer.     

Bisnaphthalimidopropyl Derivatives as Inhibitors of Leishmania SIR2 Related Protein 1

The NAD⁺‐dependent deacetylases, namely sirtuins, are involved in the regulation of a variety of biological processes such as gene silencing, DNA repair, longevity, metabolism, apoptosis, and development. An enzyme from the parasite Leishmania infantum that belongs to this family, LiSIR2RP1, is a NAD⁺‐dependent tubulin deacetylase and an ADP‐ribosyltransferase. This enzyme's involvement in L. infantum virulence and survival underscores its potential as a drug target. Our search for selective inhibitors of LiSIR2RP1 has led, for the first time, to the identification of the antiparasitic and anticancer bisnaphthalimidopropyl (BNIP) alkyl di‐ and triamines (IC₅₀ values in the single‐digit micromolar range for the most potent compounds). Structure–activity studies were conducted with 12 BNIP derivatives that differ in the length of the central alkyl chain, which links the two naphthalimidopropyl moieties. The most active and selective compound is the BNIP diaminononane (BNIPDanon), with IC₅₀ values of 5.7 and 97.4 μM against the parasite and human forms (SIRT1) of the enzyme, respectively. Furthermore, this compound is an NAD⁺‐competitive inhibitor that interacts differently with the parasite and human enzymes, as determined by docking analysis, which might explain its selectivity toward the parasitic enzyme.     

High Versatility of IPP and DMAPP Methyltransferases Enables Synthesis of C6, C7 and C8 Terpenoid Building Blocks

The natural substance class of terpenoids covers an extremely wide range of different structures, although their building block repertoire is limited to the C₅ compounds DMAPP and IPP. This study aims at the characterization of methyltransferases (MTases) that modify these terpene precursors and the demonstration of their suitability for biotechnological purposes. All seven enzymes tested accepted IPP as substrate and altogether five C₆ compounds and six C₇ compounds were formed within the reactions. A high selectivity for the deprotonation site as well as high stereoselectivity could be observed for most of the biocatalysts. Only the enzyme from Micromonospora humi also accepted DMAPP as substrate, converting it into (2R)-2-methyl-IPP in vitro. In vivo studies demonstrated the production of a C₈ compound and a hydride shift step within the MTase-catalyzed reaction. Our study presents IPP/DMAPP MTases with very different catalytic properties, which provide biosynthetic access to many novel terpene-derived structures.     

Structure‐Guided Discovery of Antitubercular Agents That Target the Gyrase ATPase Domain

In this study we explored the pharmaceutically underexploited ATPase domain of DNA gyrase (GyrB) as a potential platform for developing novel agents that target Mycobacterium tuberculosis. In this effort a combination of ligand‐ and structure‐based pharmacophore modeling was used to identify structurally diverse small‐molecule inhibitors of the mycobacterial GyrB domain based on the crystal structure of the enzyme with a pyrrolamide inhibitor (PDB ID: 4BAE ). Pharmacophore modeling and subsequent in vitro screening resulted in an initial hit compound 5 [(E)‐5‐(5‐(2‐(1H‐benzo[d]imidazol‐2‐yl)‐2‐cyanovinyl)furan‐2‐yl)isophthalic acid; IC₅₀=4.6±0.1 μm ], which was subsequently tailored through a combination of molecular modeling and synthetic chemistry to yield the optimized lead compound 24 [(E)‐3‐(5‐(2‐cyano‐2‐(5‐methyl‐1H‐benzo[d]imidazol‐2‐yl)vinyl)thiophen‐2‐yl)benzoic acid; IC₅₀=0.3±0.2 μm ], which was found to display considerable in vitro efficacy against the purified GyrB enzyme and potency against the H₃₇Rv strain of M. tuberculosis. Structural handles were also identified that will provide a suitable foundation for further optimization of these potent analogues.     

Analysis of a reactor with surface renewal for poly(ethylene terephthalate) synthesis

A mathematical model of a polycondensation reactor that can be used in the final stage for poly(ethylene terephthalate) (PET) is established and compared with experimental data obtained from a laboratory scale reactor with film renewal. Detailed side reactions are considered along with the diffusional removal of the small molecules through thin film. Among several kinetic constants, the polycondensation reaction rate constant k₁(= k₈) and diester group degradation reaction rate constant k₇ have an influence over the degree of polymerization. The values of k₁(= k₈) and k₇ for 0.05 wt% Sb₂O₃ were obtained as curve-fit values: (1) k₁(= k₈) = 3.4 × 10⁶ exp(? 18.500/RT′) (L/mol-min); (2) k₇ = 1.3 × 10¹¹ exp(? 37,800/RT′) (min^?1). Effects of the film exposure time, reduced pressure of vacuum, temperature, the initial terephthalic acid (TPA)/ethylene glycol (EG) mole ratio, the initial degree of polymerization, and catalysts were well explained by the model.     

Tetrazolylhydrazides as Selective Fragment‐Like Inhibitors of the JumonjiC‐Domain‐Containing Histone Demethylase KDM4A

The JumonjiC‐domain‐containing histone demethylase 2A (JMJD2A, KDM4A) is a key player in the epigenetic regulation of gene expression. Previous publications have shown that both elevated and lowered enzyme levels are associated with certain types of cancer, and therefore the definite role of KDM4A in oncogenesis remains elusive. To identify a novel molecular starting point with favorable physicochemical properties for the investigation of the physiological role of KDM4A, we screened a number of molecules bearing an iron‐chelating moiety by using two independent assays. In this way, we were able to identify 2‐(1H‐tetrazol‐5‐yl)acetohydrazide as a novel fragment‐like lead structure with low relative molecular mass (M_r=142 Da), low complexity, and an IC₅₀ value of 46.6 μm in a formaldehyde dehydrogenase (FDH)‐coupled assay and 2.4 μm in an antibody‐based assay. Despite its small size, relative selectivity against two other demethylases could be demonstrated for this compound. This is the first example of a tetrazole group as a warhead in JMJD demethylases.     

Reactive red 120 and NI(II) derived poly(2‐hydroxyethyl methacrylate) nanoparticles for urease adsorption

Non‐porous poly(2‐hydroxyethyl methacrylate) [p(HEMA)] nanoparticles were prepared by surfactant free emulsion polymerization. The p(HEMA) nanoparticles was about 200 nm diameter, spherical form, and non‐porous. Reactive Red 120 (RR 120) was covalently attached to the p(HEMA) nanoparticles and Ni(II) ions were incorporated to attach dye molecules. Urease was immobilized onto RR120‐Ni(II) attached p(HEMA) nanoparticles via adsorption. The maximum urease adsorption capacity of RR120‐Ni(II) attached p(HEMA) nanoparticles was 480.01 mg g^?1 nanoparticles at pH 7.0 in phosphate buffer. It was observed that urease could be repeatedly adsorbed and desorbed without significant loss in adsorption amount. K_m values were 21.50 and 34.06 mM for the free and adsorbed enzyme. The V_max values were 4 U for the free enzyme and 3.3 U for the adsorbed enzyme. The optimum pH was 25 mM pH 7 phosphate buffer for free and adsorbed enzyme. The optimum temperature was determined at 35°C and 55°C for the free and adsorbed enzyme, respectively. These findings show considerable promise for this material as an adsorption matrix in biotechnological applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39757.     

Three-dimensional microporous metal–organic framework constructed from Cadmium(II) ion with terephthalate and in-situ generated amino-tetrazole mixed-ligands

A new coordination polymer, [Cd₄(atz)₆(PTA)]_n has been firstly synthesized by employing mixed-ligand of terephthalic acid (PTA) with the in-situ generated ligand of 5-amino-tetrazolate (atz^?). Compound 1 represents a 3D microporous framework constructed from Cd-tetrazolate subunits and the subunits are bridged by PTA and atz ligands. When the subunit was collided into node, compound 1 possesses an unprecedented 3, 9-connected topological network. Furthermore, the investigations of thermal stability and luminescent property of complex 1 indicate that compound 1 may be an excellent candidate for potential blue-light emitting material.