GABAergic synaptic response and its opioidergic modulation in periaqueductal gray neurons of rats with neuropathic pain

Background  

Neuropathic pain is a chronic and intractable symptom associated with nerve injury. The periaqueductal gray (PAG) is important in the endogenous pain control system and is the main site of the opioidergic analgesia. To investigate whether neuropathic pain affects the endogenous pain control system, we examined the effect of neuropathic pain induced by sacral nerve transection on presynaptic GABA release, the kinetics of postsynaptic GABA-activated Cl^- currents, and the modulatory effect of μ-opioid receptor (MOR) activation in mechanically isolated PAG neurons with functioning synaptic boutons.     

Evaluation of enzymatic activity on nanoscale polystyrene-block-polymethylmethacrylate diblock copolymer domains

Understanding structural and functional changes of polymeric surface-bound proteins is extremely important as polymers play an increasingly significant role as arrays and substrates in proteomics applications. We carried out, for the first time, quantitative activity measurements of horseradish peroxidase (HRP) enzymes immobilized selectively on the polystyrene domains of microphase-separated polystyrene-block-polymethylmethacrylate ultrathin films. The specific enzymatic activity of HRP adsorbed on the diblock copolymer surface was evaluated and compared to that of HRP in free solution. We demonstrate that the polymeric surface-bound HRP molecules maintain approximately 85% of their activity in free solution. The unique advantages of diblock copolymer templates, involving nanoscale self-assembly and largely retained protein functionality, make the spontaneously constructed enzyme nanoarrays highly suitable as proteomics substrates. Our novel assembly method of providing functional enzymes on diblock copolymer thin films can be greatly beneficial for high-throughput and high-density protein assays.     

A General Method for Synthesis of GPI Anchors Illustrated by the Total Synthesis of the Low-Molecular-Weight Antigen from Toxoplasma gondii

Building blocks: A new, general synthetic strategy, which allows the construction of branched glycosylphosphatidylinositols (GPIs), enables the synthesis of parasitic glycolipid 1 from Toxoplasma gondii. In addition, the structure is further confirmed by recognition of monoclonal antibodies.     

Investigation of single-molecule kinetics mediated by weak hydrogen bonds within a biological nanopore

The study of factors essential for protein-peptide interactions and protein pore-mediated peptide transport are of particular relevance in biology. Wild-type α-hemolysin was adopted as a "nanoreactor" in which perturbations of the current through a protein containing a lumen-residing, aryl-capped antimicrobial peptide were seen for the first time and studied at the single-molecule level. Energy and steric considerations hint that Met-aryl interactions between aromatic residues placed at a peptide's extremities and any of the methionines lining the α-hemolysin constriction region may be the primary cause of peptide stabilization within the lumen and may be particularly important to the peptide-α-hemolysin interaction.     

Elucidation of novel nanostructures by time-lapse monitoring of polystyrene-block-polyvinylpyridine under chemical treatment

Nanoscale micellar structures of polystyrene-block-polyvinylpyridine (PS-b-PVP) diblock copolymers have proven their effectiveness in lithography and biological detection by serving as a choice material to produce nanoscale guides and delivery systems in a straightforward and rapid manner through self-assembly. Such applications can greatly benefit from having high versatility for the selection of template sizes (pattern repeat spacing) and shapes (pattern geometry), especially when reaching a size regime that conventional top-down fabrication techniques may not readily be able to provide desired feature dimensions. Selective chemical treatments of the diblock copolymers are one of the useful methods yielding a rich set of nanoscale features on PS-b-PVP. Exposure to selective vapor can induce reorganization of the polymeric chains of PS-b-PVP and alter the original micellar nanostructures. In this Article, we identify for the first time a host of new nanostructures formed at different stages of chloroform vapor annealing by performing time-lapse atomic force microscopy measurements. We determine key, time-dependent, topological parameters defining each nanostructure and present the likely scenario of polymeric chain reorganization during the morphological evolution of the diblock polymer nanodomains over time. We also ascertain intermediate morphological states containing the characteristic nanostructures from two consecutive phases as well as transition states appearing for a short time in between two subsequent phases. These research efforts may not only provide insight into the domain evolution steps of the micellar to the cylindrical structures of PS-b-PVP but may also be technologically advantageous for subwavelength mask design in nanolithography and high-density array fabrication in high throughput biodetection.     

Trichogin GA IV: a versatile template for the synthesis of novel peptaibiotics

Trichogin GA IV, isolated from the fungus Trichoderma longibrachiatum, is the prototype of lipopeptaibols, the sub-class of short-length peptaibiotics exhibiting membrane-modifying properties. This peptaibol is predominantly folded in a mixed 3(10)-/α- helical conformation with a clear, albeit modest, amphiphilic character, which is likely to be responsible for its capability to perturb bacterial membranes and to induce cell death. In previous papers, we reported on the interesting biological properties of trichogin GA IV, namely its good activity against Gram positive bacteria, in particular methicillin-resistant S. aureus strains, its stability towards proteolytic degradation, and its low hemolytic activity. Aiming at broadening the antimicrobial activity spectrum by increasing the peptide helical amphiphilicity, in this work we synthesized, by solution and solid-phase methodologies, purified and fully characterized a set of trichogin GA IV analogs in which the four Gly residues at positions 2, 5, 6, 9, lying in the poorly hydrophilic face of the helical structure, are substituted by one (position 2, 5, 6 or 9), two (positions 5 and 6), three (positions 2, 5, and 9), and four (positions 2, 5, 6, and 9) Lys residues. The conformational preferences of the Lys-containing analogs were assessed by FT-IR absorption, CD and 2D-NMR techniques in aqueous, organic, and membrane-mimetic environments. Interestingly, it turns out that the presence of charged residues induces a transition of the helical conformation adopted by the peptaibols (from 3(10)- to α-helix) as a function of pH in a reversible process. The role played in the analogs by the markedly increased amphiphilicity was further tested by fluorescence leakage experiments in model membranes, protease resistance, antibacterial and antifungal activities, cytotoxicity, and hemolysis. Taken together, our biological results provide evidence that some of the least substituted among these analogs are good candidates for the development of new membrane-active antimicrobial agents.     

Turbulent equipartition and homogenization of plasma angular momentum

A physical model of turbulent equipartition (TEP) of plasma angular momentum is developed. We show that using a simple, model insensitive ansatz of conservation of total angular momentum, a TEP pinch of angular momentum can be obtained. We note that this term corresponds to a part of the pinch velocity previously calculated using quasilinear gyrokinetic theory. We observe that the nondiffusive TEP flux is inward, and therefore may explain the peakedness of the rotation profiles observed in certain experiments. Similar expressions for linear toroidal momentum and flow are computed and it is noted that there is an additional effect due the radial profile of moment of inertia density.