CuAAC synthesis of resorcin[4]arene-based glycoclusters as multivalent ligands of lectins

Synthetic multivalent glycoclusters show promise as anti-adhesives for the treatment of bacterial infections. Here we report the synthesis of a family of tetravalent galactose and lactose functionalised macrocycles based on the resorcin[4]arene core. The development of diastereoselective synthetic routes for the formation of lower-rim propargylated resorcin[4]arenes and their functionalistion via Cu-catalyzed azide-alkyne click chemistry is described. ELLA binding studies confirm that galactose sugar clusters are effective ligands for the PA-IL bacterial lectin of Pseudomonas aeruginosa while poor binding for the lactose-based monovalent probe and no binding could be measured for the multivalent glycoclusters was observed for the human galectin-1.     

The synthesis of novel heteroaryl-fused 7,8,9,10-tetrahydro-6H-azepino[1,2-a]indoles, 4-oxo-2,3-dihydro-1H-[1,4]diazepino[1,7-a]indoles and 1,2,4,5-tetrahydro-[1,4]oxazepino[4,5-a]indoles. Effective inhibitors of HCV NS5B polymerase

Three synthetic approaches have been developed that allow efficient access to novel heteroaryl fused indole ring systems, including: 7,8,9,10-tetrahydro-6H-azepino[1,2-a]indoles, 4-oxo-2,3-dihydro-1H-[1,4]diazepino[1,7-a]indoles and 1,2,4,5-tetrahydro-[1,4]oxazepino[4,5-a]indoles. Each strategy is fully exemplified and the relative merits and limitations of the approaches are discussed. The hepatitis C virus (HCV) non-structural 5B (NS5B) polymerase inhibitory activities of select examples from each molecular class are briefly presented.     

Production of camptothecin by hairy roots and regenerated transformed shoots of Ophiorrhiza rugosa var. decumbens

Camptothecin (CPT), the derivatives of which are used clinically for the treatment of metastatic colon cancer, is isolated from intact plants that can be subjected to environmental fluctuations. In?vitro cultures may be an alternate and continuous source for year-round production of CPT. Since CPT production by undifferentiated cell cultures is low, differentiated tissues such as root cultures may be a viable alternate source for CPT production. Hairy roots were induced in Ophiorriza rugosa, a source of CPT, using Agrobacterium rhizogenes strain LBA9402. The hairy roots, when cultured in light, showed spontaneous regeneration of shoots. Analysis of CPT levels in the hairy roots and in?vitro-grown transformed shoots revealed 0.009% d.w. and 0.012% d.w., respectively.     

Copper(II) complexes of 2-halo-3-methylpyridine: synthesis, structure, and magnetic behaviour of Cu(2-X-3-CH(3)py)2X'2 [X, X' = chlorine or bromine; py = pyridine

An isocoordinate family of compounds has been generated with the general formula (2-X-3-methylpyridine)(2)CuX'(2), where X, X' = Cl or Br. While each forms trans-ligand compounds, they vary in copper coordination geometry, canting of the pyridine rings and magnetic behavior. The copper bromide analogues exhibit weak ferromagnetic interactions whereas the copper chloride analogues exhibit antiferromagnetic interactions. Each compound has been characterized by IR, powder X-ray diffraction, single-crystal X-ray diffraction, and temperature dependent magnetic susceptibility.     

Molecular dynamics simulation and binding energy calculation for estimation of oligonucleotide duplex thermostability in RNA-based therapeutics

For oligonucleotide-based therapeutics, a thorough understanding of the thermodynamic properties of duplex formation is critical to developing stable and potent drugs. For unmodified small interfering RNA (siRNA), DNA antisense oligonucleotide (AON) and locked nucleic acid (LNA), DNA/LNA modified oligonucleotides, nearest neighbor (NN) methods can be effectively used to quickly and accurately predict duplex thermodynamic properties such as melting point. Unfortunately, for chemically modified olignonucleotides, there has been no accurate prediction method available. Here we describe the potential of estimating melting temperature (T(m)) for nonstandard oligonucleotides by using the correlation of the experimental T(m) with the calculated duplex binding energy (BE) for oligonucleotides of a given length. This method has been automated into a standardized molecular dynamics (MD) protocol through Pipeline Pilot (PP) using the CHARMm component in Discovery Studio (DS). Results will be presented showing the correlation of the predicted data with experiment for both standard and chemically modified siRNA and AON.     

Development and validation of a reference measurement procedure for certification of phenytoin, phenobarbital, lamotrigine, and topiramate in human serum using isotope-dilution liquid chromatography/tandem mass spectrometry

Phenytoin (PHT), phenobarbital (PHB), lamotrigine (LTG), and topiramate (TPM) are some of the most widely used antiepileptic drugs (AEDs). Monitoring of their concentrations in serum is important for the treatment of epilepsy. A reference measurement procedure (RMP) for certification of PHT, PHB, LTG, and TPM in serum has been developed and critically evaluated. Isotopically labeled compounds of PHT, PHB, LTG, and TPM are used as internal standards for the four AEDs. The four drugs and their respective labeled internal standards are simultaneously extracted from serum using solid-phase extraction prior to reversed-phase liquid chromatography–tandem mass spectrometry (LC-MS/MS). Chromatographic separation was performed using a C₁₈ column. Electrospray ionization (ESI) in the positive ion mode for PHT and LTG, and in the negative ion mode for PHB and TPM were used. The recovery of AEDs added to serum (accuracy of the extraction method) was evaluated by recovery studies of measuring the four drugs in spiked samples with known drug levels. The recoveries of the added drugs ranged from 98.6% to 102.0%. The absolute recoveries (extraction efficiencies) of the four drugs with this method ranged from 97% to 100%. Excellent repeatability was obtained for the four drugs with between-set coefficients of variation (CVs) within 1%. The type B components estimates are conservatively large and are considerably larger than the type A component. Therefore, we use the usual metrological expansion factor of 2 to provide an approximate 95% coverage interval. The relative expanded uncertainties for the four AEDs ranged from 2.3% to 2.4%. This LC-MS/MS RMP for PHT, PHB, LTG, and TPM in serum demonstrating good accuracy and precision can be used to assess the accuracy of routine methods used in clinical laboratories.     

Gelation behavior of polysaccharide-based interpenetrating polymer network (IPN) hydrogels

We report the preparation and rheological characterization of interpenetrating polymer network (IPN) hydrogels made from alginate and hydrophobically modified ethyl hydroxyl ethyl cellulose (HMEHEC). To our knowledge, there have been no studies of the gelation behavior of IPNs. We found that the rheology of these systems can be easily tuned, with the elastic modulus of the IPN strongly dependent on the relative ratio of HMEHEC to alginate. The sol–gel transition of these systems was found to satisfy the Winter–Chambon criterion for gelation at various crosslinker densities. From the power law relationship of the dynamic moduli (G ^′ ~G ^″ ~ω ⁿ), the exponent n appears to be dependent on both the crosslinker density and relative amount of two polymers. The value of n was found to be ~0.5 for all samples for stoichiometric amounts of crosslinker. The effect of molecular weight of HMEHEC on the gel point and viscoelastic exponent has also been reported. Alginate seems to dominate the kinetics of the process but the effect of high molecular weight HMEHEC on the gel point, especially at lower proportion was also evident.     

Catalytic asymmetric γ-alkylation of carbonyl compounds via stereoconvergent Suzuki cross-couplings

With the aid of a chiral nickel catalyst, enantioselective γ- (and δ-) alkylations of carbonyl compounds can be achieved through the coupling of γ-haloamides with alkylboranes. In addition to primary alkyl nucleophiles, for the first time for an asymmetric cross-coupling of an unactivated alkyl electrophile, an arylmetal, a boronate ester, and a secondary (cyclopropyl) alkylmetal compound are shown to couple with significant enantioselectivity. A mechanistic study indicates that cleavage of the carbon-halogen bond of the electrophile is irreversible under the conditions for asymmetric carbon-carbon bond formation.     

A comparative picosecond transient infrared study of 1-methylcytosine and 5'-dCMP that sheds further light on the excited states of cytosine derivatives

The role of N1-substitution in controlling the deactivation processes in photoexcited cytosine derivatives has been explored using picosecond time-resolved IR spectroscopy. The simplest N1-substituted derivative, 1-methylcytosine, exhibits relaxation dynamics similar to the cytosine nucleobase and distinct from the biologically relevant nucleotide and nucleoside analogues, which have longer-lived excited-state intermediates. It is suggested that this is the case because the sugar group either facilitates access to the long-lived (1)n(O)π* state or retards its crossover to the ground state.     

In-channel amperometric detection for microchip electrophoresis using a wireless isolated potentiostat

The combination of microchip electrophoresis with amperometric detection leads to a number of analytical challenges that are associated with isolating the detector from the high voltages used for the separation. While methods such as end-channel alignment and the use of decouplers have been employed, they have limitations. A less common method has been to utilize an electrically isolated potentiostat. This approach allows placement of the working electrode directly in the separation channel without using a decoupler. This paper explores the use of microchip electrophoresis and electrochemical detection with an electrically isolated potentiostat for the separation and in-channel detection of several biologically important anions. The separation employed negative polarity voltages and tetradecyltrimethylammonium bromide (as a buffer modifier) for the separation of nitrite (NO??), glutathione, ascorbic acid, and tyrosine. A half-wave potential shift of approximately negative 500 mV was observed for NO?? and H?O? standards in the in-channel configuration compared to end-channel. Higher separation efficiencies were observed for both NO?? and H?O? with the in-channel detection configuration. The limits of detection were approximately two-fold lower and the sensitivity was approximately two-fold higher for in-channel detection of nitrite when compared to end-channel. The application of this microfluidic device for the separation and detection of biomarkers related to oxidative stress is described.