How does chronic activity modulation lead to global remodeling of proteins at synapses and synaptic scaling? Here we report a role of guanylate-kinase-associated-protein (GKAP; also known as SAPAP), a scaffolding molecule linking NMDA receptor-PSD-95 to Shank-Homer complexes, in these processes. Over-excitation removes GKAP from synapses via ubiquitin-proteasome system, while inactivity induces synaptic accumulation of GKAP in rat hippocampal neurons. The bi-directional changes of synaptic GKAP levels are controlled by specific CaMKII isoforms coupled to different Ca2+ channels. α-CaMKII activated by NMDA receptor phosphorylates Serine-54 of GKAP to induce poly-ubiquitination of GKAP. In contrast, β-CaMKII activation via L-type voltage-dependent calcium channel promotes GKAP recruitment by phosphorylating Serine-340 and Serine-384 residues, which uncouples GKAP from MyoVa motor complex. Remarkably, overexpressing GKAP turnover mutants not only hampers activity-dependent remodeling of PSD-95 and Shank but also blocks bi-directional synaptic scaling. Therefore, activity-dependent turnover of PSD proteins orchestrated by GKAP is critical for homeostatic plasticity.

Their nanometer-scale dimensions, along with their large shape anisotropy, high mechanical strength, and very high thermal and electrical conductivity, make carbon nanotubes (CNTs) an excellent material choice for nanocomposites, in which even a very small amount of CNTs can induce significant changes in the material's properties.[1±3] Whereas most of the reported studies were focused on the enhancement of mechanical properties and/or electrical conductivity of composites, in this communication we investigate the influence of CNTs on the microstructure and electromechanical properties of the electrostrictive terpolymer poly(vinylidene fluorideÐ trifluoroethyleneÐchlorofluoroethylene), abbreviated P(VDF-TrFE-CFE). It will be shown that the crystallinity, Young's modulus, dielectric constant, electrostrictive strain, and elastic energy density of P(VDF-TrFE-CFE) can be simultaneously improved by inclusion of only 0.5 wt.-% CNTs.PVDF-based ferroelectric polymers are well known for their strong piezoelectricity. They can perform efficient electrical-to-mechanical energy conversion and generate large mechanical actuation in response to external electrical stimulation. Therefore, these polymers are attractive for a broad range of applications, such as sensors, actuators, artificial muscles, ferroelectric memory devices, and integrated microelectromechanical systems. [4,5] Recently, by employing defect modifications, such as by introducing a bulky third monomer CFE, it has been shown that the normal ferroelectric P(VDFTrFE) can be converted into a ferroelectric relaxor P(VDFTrFE-CFE), and the electromechanical response can be significantly enhanced. [6,7] For instance, a hysteresis-free

The role of Lys-63 ubiquitin chains in targeting proteins for proteasomal degradation is still obscure. We systematically compared proteasomal processing of Lys-63 ubiquitin chains with that of the canonical proteolytic signal, Lys-48 ubiquitin chains. Quantitative mass spectrometric analysis of ubiquitin chains in HeLa cells determines that the levels of Lys-63 ubiquitin chains are insensitive to short-time proteasome inhibition. Also, the Lys-48/Lys-63 ratio in the 26 S proteasome-bound fraction is 1.7-fold more than that in the cell lysates, likely because some cellular Lys-63 ubiquitin conjugates are sequestered by Lys-63 chain-specific binding proteins. In vitro, Lys-48 and Lys-63 ubiquitin chains bind the 26 S proteasome comparably, whereas Lys-63 chains are deubiquitinated 6-fold faster than Lys-48 chains. Also, Lys-63 tetraubiquitin-conjugated UbcH10 is rapidly deubiquitinated into the monoubiquitinated form, whereas Lys-48 tetraubiquitin targets UbcH10 for degradation. Furthermore, we found that both the ubiquitin aldehyde-and 1,10-phenanthroline-sensitive deubiquitinating activities of the 26 S proteasome contribute to Lys-48-and Lys-63-linkage deubiquitination, albeit the inhibitory extents are different. Together, our findings suggest that compared with Lys-48 chains, cellular Lys-63 chains have less proteasomal accessibility, and proteasome-bound Lys-63 chains are more rapidly deubiquitinated, which could cause inefficient degradation of Lys-63 conjugates.

Liquid chromatography/mass spectrometry (LC/MS), utilizing a time-of-flight (TOF) mass analyzer, has been evaluated and applied to problems in bioanalysis for pharmacokinetics and drug metabolism. The data obtained by TOF MS differ from those obtained using quadrupole mass spectrometer instruments in that full-scan spectra can be routinely collected with greater sensitivity and speed. Both quantitative and qualitative information, including compound concentration in rat plasma and full-scan atmospheric pressure ionization mass spectra, are concurrently obtained. This approach has been used to characterize the disposition of several drug compounds that have been simultaneously dosed to rats in a cassette format. Quantitation limits in the 5-25 ng/mL range (approximately 20 nM) were obtained from nominal mass chromatograms (0.5 Da resolution). A reference lock mass was used to provide accurate mass measurement to reach third decimal place accuracy in the monoisotopic molecular weight. An improvement in quantitation limits was demonstrated after using accurate mass determinations. Several possible preliminary drug metabolites were confirmed or refuted, based on accurate mass. The trend of metabolite formation and clearance was qualitatively evaluated.

An improved process is presented to functionalize carbon nanotubes by potassium permanganate with the help of phase transfer catalyst (PTC). The PTC helps to extract potassium permanganate from the solid phase to an organic solvent phase and improves the efficiency of nanotube oxidation. The higher reaction efficiency as well as mild reaction conditions leads to a higher yield of functional nanotube preparation. X-ray photoelectron spectroscopy confirms the functional groups attached to the nanotube surface. A preliminary comparison is given of the potassium permanganate oxidation of nanotubes with and without PTC. This method is believed to be a potential economic method for large-scale functional nanotube preparation.

Background: Spinal muscular atrophy (SMA) is a devastating genetic disorder caused by low levels of survival motor neuron (SMN) protein.Results: Ubiquitin-specific protease 9x (Usp9x) interacts with, deubiquitinates, and stabilizes SMN. Conclusion: Usp9x likely deubiquitinates SMN to protect it from Ub-dependent degradation. Significance: Usp9x is a key mediator that regulates the protein levels of SMN and the SMN complex.

No abstract

An automated and integrated system for DNA typing directly from blood samples has been developed. The multiplexed eight-array system is based on capillary microfluidics and capillary array electrophoresis. Three short-tandem-repeat loci, vWA, THO1, and TPOX, are coamplified simultaneously in a fused-silica capillary by a hot-air thermocycler. Blood is directly used as the sample for polymerase chain reaction (PCR) without any pretreatment. Modifications of standard protocols are necessary for direct PCR from blood. A programmable syringe pump plus a set of multiplexed liquid nitrogen freeze/thaw switching valves are employed for liquid handling in the fluid distribution network. The system fully integrates sample loading, PCR, addition of an absolute standard, on-line injection of sample and standards, separation and detection. The genotypes from blood samples can be clearly identified in eight parallel channels when the electropherograms are compared with that of the standard allelic ladder by itself. Regeneration and cleaning of the entire system prior to subsequent runs are also integrated into the instrument. The instrumentation is compatible with future expansion to hundreds of capillaries to achieve even higher throughput.