A series of 2-adamantanamines with alkyl adducts of various lengths were examined for efficacy against strains of influenza A including those having an S31N mutation in M2 proton channel that confer resistance to amantadine and rimantadine. The addition of as little as one CH2 group to the methyl adduct of the amantadine/rimantadine analogue, 2-methyl-2-aminoadamantane, led to activity in vitro against two M2 S31N viruses A/Calif/07/2009 (H1N1) and A/PR/8/34 (H1N1) but not to a third A/WS/33 (H1N1). Solid state NMR of the transmembrane domain (TMD) with a site mutation corresponding to S31N shows evidence of drug binding. But electrophysiology using the full length S31N M2 protein in HEK cells showed no blockade. A wild type strain, A/Hong Kong/1/68 (H3N2) developed resistance to representative drugs within one passage with mutations in M2 TMD, but A/Calif/07/2009 S31N was slow (>8 passages) to develop resistance in vitro, and the resistant virus had no mutations in M2 TMD. The results indicate that 2-alkyl-2-aminoadamantane derivatives with sufficient adducts can persistently block p2009 influenza A in vitro through an alternative mechanism. The observations of an HA1 mutation, N160D, near the sialic acid binding site in both 6-resistant A/Calif/07/2009(H1N1) and the broadly resistant A/WS/33(H1N1) and of an HA1 mutation, I325S, in the 6-resistant virus at a cell-culture stable site suggest that the drugs tested here may block infection by direct binding near these critical sites for virus entry to the host cell.

Rimantadine hydrochloride (α-methyl-1-adamantane-methalamine hydrochloride) is a chiral compound which exerts antiviral activity against the influenza A virus by inhibiting proton conductance of the M2 ion channel. In complex with M2, rimantadine has always been characterized as a racemic mixture. Here, we report the novel enantioselective synthesis of deuterium-labeled (R)- and (S)-rimantadine and the characterization of their protein-ligand interactions using solid-state NMR. Isotropic chemical shift changes strongly support differential binding of the enantiomers to the proton channel. Position restrained simulations satisfying distance restraints from (13)C-(2)H rotational-echo double-resonance NMR show marked differences in the hydrogen-bonding pattern of the two enantiomers at the binding site. Together these results suggest a complex set of interactions between (R)-rimantadine and the M2 proton channel, leading to a higher stability for this enantiomer of the drug in the channel pore.

NMR spectroscopy of helical membrane proteins has been very challenging on multiple fronts. The expression and purification of these proteins while maintaining functionality has consumed countless graduate student hours. Sample preparations have depended on whether solution or solid-state NMR spectroscopy was to be performed – neither have been easy. In recent years it has become increasingly apparent that membrane mimic environments influence the structural result. Indeed, in these recent years we have rediscovered that Nobel laureate, Christian Anfinsen, did not say that protein structure was exclusively dictated by the amino acid sequence, but rather by the sequence in a given environment (Anfinsen, 1973) [106]. The environment matters, molecular interactions with the membrane environment are significant and many examples of distorted, non-native membrane protein structures have recently been documented in the literature. However, solid-state NMR structures of helical membrane proteins in proteoliposomes and bilayers are proving to be native structures that permit a high resolution characterization of their functional states. Indeed, solid-state NMR is uniquely able to characterize helical membrane protein structures in lipid environments without detergents. Recent progress in expression, purification, reconstitution, sample preparation and in the solid-state NMR spectroscopy of both oriented samples and magic angle spinning samples has demonstrated that helical membrane protein structures can be achieved in a timely fashion. Indeed, this is a spectacular opportunity for the NMR community to have a major impact on biomedical research through the solid-state NMR spectroscopy of these proteins.

While aminoadamantanes are well-established inhibitors of the influenza A M2 proton channel, the mechanisms by which they are rendered ineffective against M2 S31N are unclear. Solid state NMR, isothermal titration calorimetry, electrophysiology, antiviral assays, and molecular dynamics simulations suggest stronger binding interactions for aminoadamantanes to M2 WT compared to negligible or weak binding to M2 S31N . This is due to reshaping of the M2 pore when N31 is present, which, in contrast to wild-type (WT), leads (A) to the loss of the V27 pocket for the adamantyl cage and to a predominant orientation of the ligand's ammonium group toward the N-terminus and (B) to the lack of a helical kink upon ligand binding. The kink, which reduces the tilt of the C-terminal helical domain relative to the bilayer normal, includes the W41 primary gate for proton conductance and may prevent the gate from opening, representing an alternative view for how these drugs prevent proton conductance.

The base-catalysed addition of diphenylphosphine to the substituted diphenylethynes RC᎐ ᎐ ᎐ CRЈ (R = Ph, RЈ = Ph, o-tolyl, m-tolyl or 2-biphenyl; R = m-tolyl, RЈ = o-tolyl or m-tolyl) yielded Ph 2 PC(R)᎐ ᎐ CHRЈ and/or Ph 2 PCH(R)CH(RЈ)PPh 2 . Proton, 13 C, 13 P and two-dimensional rotating frame Overhauser enhancement 1 H NMR spectra have been used to determine the stereochemical pathways of the reactions and the stereochemistry of the products. In general the more hindered alkynes undergo monoaddition ultimately to yield phosphinoalkenes with the Ph 2 P attached to the carbon bearing the least bulky substituent and cis to the olefinic proton, while for the less hindered alkynes the trans isomer is formed initially and this then reacts further to give meso/erythro-diphosphinoalkanes. Bis(o-tolyl)ethyne does not react with Ph 2 PH under the same conditions. Crystal structures were determined for E-and Z-Ph 2 P(Ph)C᎐ ᎐ CHPh and show distortions of interbond angles consistent with the pattern of strain implied by the foregoing reactions. The sulfides of the phosphinoalkenes and the Mo(CO) 4 complexes of the diphosphinoalkanes were also prepared and their 1 H, 13 C and 31 P NMR spectra recorded. In several cases the pattern of 13 CO NMR signals for the complexes was used unambiguously to determine the stereochemistry of the parent diphosphines.

This report investigates the homotetrameric membrane protein structure of the S31N M2 protein from Influenza A virus in the presence of a high molar ratio of lipid. The structured regions of this protein include a single transmembrane helix and an amphipathic helix. Two structures of the S31N M2 conductance domain from Influenza A virus have been deposited in the Protein Data Bank (PDB). These structures present different symmetries about the channel main axis. We present new magic angle spinning and oriented sample solid-state NMR spectroscopic data for S31N M2 in liquid crystalline lipid bilayers using protein tetramer:lipid molar ratios ranging from 1:120 to 1:240. The data is consistent with an essentially 4-fold-symmetric structure very similar to the M2 WT structure that also has a single conformation for the four monomers, except at the His37 and Trp41 functional sites when characterized in samples with a high molar ratio of lipid. While detergent solubilization is well recognized today as a nonideal environment for small membrane proteins, here we discuss the influence of a high lipid to protein ratio for samples of the S31N M2 protein to stabilize an essentially 4-fold-symmetric conformation of the M2 membrane protein. While it is generally accepted that the chemical and physical properties of the native environment of membrane proteins needs to be reproduced judiciously to achieve the native protein structure, here we show that not only the character of the emulated membrane environment is important but also the abundance of the environment is important for achieving the native structure. This is a critical finding as a membrane protein spectroscopist's goal is always to generate a sample with the highest possible protein sensitivity while obtaining spectra of the nativelike structure.

Malignant gliomas are associated with extremely poor clinical outcomes in both humans and dogs, and novel therapies are needed. Glioma-bearing canine patients may serve as promising preclinical models for human therapies, including complementary medicine. The objective of this study was to evaluate the effects of mistletoe extract (Viscum album) alone and in combination with mebendazole in an in vitro model of canine high-grade astrocytoma using the cell line SDT-3G. SDT-3G cells were exposed to a range of concentrations of mistletoe extract alone to obtain an IC50. In separate experiments, cells were exposed to mebendazole at a previously determined IC50 (0.03 µM) alone or in conjunction with varying concentrations of mistletoe extract to determine the additive effects. The IC50 for mistletoe alone was 5.644 ± 0.09 SD μg/mL. The addition of mistletoe at 5 μg/mL to mebendazole at 0.03 µM led to increased cell death compared to what would be expected for each drug separately. The cytotoxicity of mistletoe in vitro and its additive effect with mebendazole support future expanded in vitro and in vivo studies in dogs and supply early evidence that this may be a useful adjunct therapeutic agent for use in glioma-bearing dogs. To the authors’ knowledge, this is the first published report of Viscum album extract in canine glioma.

arrhythmogenic early afterdepolarizations (EADs) characteristic of LQT2 myocytes under b-adrenergic stimulation. Parameters of Ca handling were measured in ventricular myocytes isolated from normal and LQT2 hearts using confocal Ca imaging and whole-cell patch clamp. Ca imaging revealed no LQT2-mediated changes in amplitude of Ca transients and SR Ca content under basal conditions. Experiments in saponin-permeabilized cells using SRentrapped low-affinity Ca indicator revealed enhanced RyR-mediated SR Ca leak and SERCA-mediated Ca uptake in LQT2 myocytes. Correspondingly, western blot analyses using phospho-specific antibodies showed that phosphorylation of both RyR and phospholamban is significantly higher in LQT2 CMs vs. controls at both PKA and CaMKII sites. In the presence of isoproterenol (50 nM) LQT2 CMs exhibited diminished Ca transient amplitudes and SR Ca content compared to controls. Stimulation of LQT2 CMs with isoproterenol resulted in prolongation of plateau of action potentials accompanied by aberrant Ca releases and phase 3 EADs, in contrast to controls. Importantly, preincubation of LQT2 CMs with CaMKII inhibitor KN93 (10 min, 500 nM) prevented ISO-mediated changes in AP duration, disturbances in Ca handling and EADs. Analysis of CaMKII activity revealed no differences between LQT2 and control heart tissues, while Western-blot analysis demonstrated 30% decrease in the abundance of catalytic subunit of protein phosphatase type 1 (PP1). These data suggest that hyperactive RyRs due to adaptive reduction in PP1 activity and thereby RyR hyperphosphorylation is a key contributor to enhanced triggered activity in hereditary LQT2 syndrome.