Phototactic responses of Chlamydomonas reinhardtii in electric fields

Crude mitochondria isolated from Jerusalem artichoke ( Helianthus tuberosus L.) tubers were purified on a 23% (v/v) continuous Percoll gradient. Microbodies and damaged mitochondria banded on top of the gradient, whereas the purified mitochondria handed close to the bottom. The purified mitochondria showed improved membrane integrities, specific enzyme activities and respiratory properties (higher rate, respiratory control, ADP/O ratio) than the crude mitochondria. Purified mitochondria could he stored for 24 h on ice in a phosphate buffer with only small loss of activity.     

Synthesis and in vivo imaging properties of [11C]befloxatone: a novel highly potent positron emission tomography ligand for mono-amine oxidase-A

Befloxatone (1, (5R)-5-(methoxymethyl)-3-[4-[(3R)-4,4,4-trifluoro-3-hydroxybutoxy]phenyl]-2-oxazolidinone) is an oxazolidinone derivative belonging to a new generation of reversible and selective mono-amine oxidase-A (MAO-A) inhibitors. In vitro and ex vivo studies have demonstrated that befloxatone is a potent, reversible and competitive MAO-A inhibitor with potential antidepressant properties. Befloxatone (1) was labelled with carbon-11 (t(12): 20.4 min) using [(11)C]phosgene as reagent. Typically, starting from a 1.2 Ci (44.4 GBq) cyclotron-produced [(11)C]CH(4) batch, 150-300 mCi (5.55-11.10 GBq) of [(11)C]befloxatone ([(11)C]-1) with a radiochemical- and chemical purity of more than 99% were routinely obtained within 20 min of radiosynthesis (including HPLC purification) with specific radioactivities of 500-2000 mCi/micromol (18.5-74.0 GBq/micromol). The results obtained in vivo with carbon-11-labelled befloxatone not only confirm the biochemical and pharmacological profile of befloxatone found in rodent and in human tissues but also point out [(11)C]befloxatone as an excellent tool for the assessment of MAO-A binding sites using positron emission tomography, a high-resolution, sensitive, non-invasive and quantitative imaging technique.     

Influence of liposome composition and membrane binding on protein kinase activity of PI3Kγ

Phosphoinositide 3-kinase γ (PI3Kγ) has been implicated in a variety of cellular signaling processes. It is a multifunctional enzyme with lipid and protein kinase activity that also acts as a scaffold protein. Although it is well known that membrane recruitment is essential for the phosphorylation of phosphoinositides, the cellular localization of PI3Kγ as a protein kinase remains unclear. It has merely been described that PI3Kγ protein kinase activity leading to MAPK activation seems to be restricted to a cytosolic localization. Here, we demonstrate that a hybrid-PI3Kγ having protein kinase, but not lipid kinase activity shows a similar cellular distribution with a high membrane association and comparable liposome binding behavior to wild-type PI3Kγ. Binding of PI3Kγ to liposomes mimicking the natural plasma membrane slightly stimulates autophosphorylation of PI3Kγ. However, liposomes containing an unphysiologically high amount of PI inhibit autophosphorylation of PI3Kγ. Finally, PI3Kγ bound to membrane fragments does not show autophosphorylation which is possibly due to protein–protein-interactions at the plasma membrane. This indicates that not only MAPK activation, but PI3Kγ protein kinase activity in general is localized in the cytosol.     

Nascent structure–activity relationship study of a diastereomeric series of kappa opioid receptor antagonists derived from CJ-15,208

Cyclic tetrapeptide c[Phe-pro-Phe-trp] 2, a diastereomer of CJ-15,208 (1), was identified as a potent dual κ/μ opioid receptor antagonist devoid of δ opioid receptor affinity against cloned human receptors: K_i (2) = 3.8 nM (κ), 30 nM (μ); IC₅₀ ([³⁵S]GTPγS binding) = 140 nM (κ), 21 nM (μ). The d-tryptophan residue rendered 2 ca. eightfold and fourfold more potent at κ and μ, respectively, than the corresponding l-configured tryptophan in the natural product 1. Phe analogs 3–10, designed to probe the effect of substituents on receptor affinity and selectivity, possessed K_i values ranging from 14 to 220 nM against the κ opioid receptor with μ/κ ratios of 0.45–3.0. An alanine scan of 2 yielded c[Ala-pro-Phe-trp] 12, an analog equipotent to 2. Agents 2 and 12 were pure antagonists in vitro devoid of agonist activity. Ac-pro-Phe-trp-Phe-NH₂ 16 and Ac-Phe-trp-Phe-pro-NH₂ 17 two of the eight possible acyclic peptides derived from 1 and 2, were selective, modestly potent μ ligands: K_i (16) = 340 nM (μ); K_i (17) = 360 nM (μ).     

Diet‐dependent female evolution influences male lifespan in a nuptial feeding insect

Theory predicts that lifespan will depend on the dietary intake of an individual, the allocation of resources towards reproduction and the costs imposed by the opposite sex. Although females typically bear the majority of the cost of offspring production, nuptial feeding invertebrates provide an ideal opportunity to examine the extent to which reproductive interactions through gift provisioning impose a cost on males. Here we use experimental evolution in an Australian ground cricket to assess how diet influences male lifespan and how the costs of mating evolve for males. Our findings show that males had significantly shorter lifespans in populations that adapted to a low‐quality diet and that this divergence is driven by evolutionary change in how females interact with males over reproduction. This suggests that the extent of sexual conflict over nuptial feeding may be under‐realized by focusing solely on the consequences of reproductive interactions from the female’s perspective.     

Novel sulfamoyl benzamides as selective CB2 agonists with improved in vitro metabolic stability

A lead optimization campaign in our previously reported sulfamoyl benzamide class of CB₂ agonists was conducted to improve the in vitro metabolic stability profile in this series while retaining high potency and selectivity for the CB₂ receptor. From this study, compound 14, N-(3,4-dimethyl-5-(morpholinosulfonyl)phenyl)-2,2-dimethylbutanamide, was identified as a potent and selective CB₂ agonist exhibiting moderate in vitro metabolic stability and oral bioavailability. Compound 14 demonstrated in vivo efficacy in a rat model of post-surgical pain.