Imaging of protein layers with an optical microscope for the characterization of peptide microarrays.

Solid-phase assays play a crucial role today in biological studies. These assays are based on the immobilization of probe molecules on a surface, which are able to capture specifically soluble receptors. In particular, peptide microarrays have emerged as powerful tools in a variety of applications. In this context, optical techniques that allow imaging of nanometer-thick biomolecular films, and thereby the characterization of microarrays, are of great interest. For this purpose, we used a recently disclosed wide-field optical imaging technique of surface nanostructures called Sarfus, which is based on the use of a standard optical microscope and antireflection substrates. We demonstrate here that this technique allows the imaging of the protein layers that result from the specific capture of antibodies by arrayed peptide probes with a spatial resolution of 0.45 microm. The relationship between the thickness of the antibody layer and peptide or antibody concentration was examined.     

NADPH binding to beta-subunit regulates inactivation of voltage-gated K(+) channels

Ancillary beta-subunits regulate the voltage-dependence and the kinetics of Kv currents. The Kvbeta proteins bind pyridine nucleotides with high affinity but the role of cofactor binding in regulating Kv currents remains unclear. We found that recombinant rat Kvbeta 1.3 binds NADPH (K(d)=1.8+/-0.02 microM) and NADP(+) (K(d)=5.5+/-0.9 microM). Site-specific modifications at Tyr-307 and Arg-316 decreased NADPH binding; whereas, K(d) NADPH was unaffected by the R241L mutation. COS-7 cells transfected with Kv1.5 cDNA displayed non-inactivating currents. Co-transfection with Kvbeta1.3 accelerated Kv activation and inactivation and induced a hyperpolarizing shift in voltage-dependence of activation. Kvbeta-mediated inactivation of Kv currents was prevented by the Y307F and R316E mutations but not by the R241L substitution. Additionally, the R316E mutation weakened Kvalpha-beta interaction. Inactivation of Kv currents by Kvbeta:R316E was restored when excess NADPH was included in the patch pipette. These observations suggest that NADPH binding is essential for optimal interaction between Kvalpha and beta subunits and for Kvbeta-induced inactivation of Kv currents.     

Metastable mesoscopic clusters in solutions of sickle-cell hemoglobin

Sickle cell hemoglobin (HbS) is a mutant, whose polymerization while in deoxy state in the venous circulation underlies the debilitating sickle cell anemia. It has been suggested that the nucleation of the HbS polymers occurs within clusters of dense liquid, existing in HbS solutions. We use dynamic light scattering with solutions of deoxy-HbS, and, for comparison, of oxy-HbS and oxy-normal adult hemoglobin, HbA. We show that solutions of all three Hb variants contain clusters of dense liquid, several hundred nanometers in size, which are metastable with respect to the Hb solutions. The clusters form within a few seconds after solution preparation and their sizes and numbers remain relatively steady for up to 3 h. The lower bound of the cluster lifetime is 15 ms. The clusters exist in broad temperature and Hb concentration ranges, and occupy 10(-5)-10(-2) of the solution volume. The results on the cluster properties can serve as test data for a potential future microscopic theory of cluster stability and kinetics. More importantly, if the clusters are a part of the nucleation mechanism of HbS polymers, the rate of HbS polymerization can be controlled by varying the cluster properties.     

Synthesis and biological evaluation of novel 5-aryl-4-(5-nitrofuran-2-yl)-pyrimidines as potential anti-bacterial agents

A facile two-step synthetic approach to fluorinated and non-fluorinated 5-aryl-4-(5-nitrofuran-2-yl)-pyrimidines from readily available 5-bromo-4-(furan-2-yl)pyrimidine has been developed. All synthesized compounds were screened in vitro for their antibacterial activities against twelve various bacterial strains. It is demonstrated that some of these compounds exhibited significant antibacterial activities against strains Neisseria gonorrhoeae and Staphylococcus aureus, comparable and even higher with that commercial drug Spectinomycin.     

Tumor suppressor Tsc1 is a new Hsp90 co‐chaperone that facilitates folding of kinase and non‐kinase clients

The tumor suppressors Tsc1 and Tsc2 form the tuberous sclerosis complex (TSC), a regulator of mTOR activity. Tsc1 stabilizes Tsc2; however, the precise mechanism involved remains elusive. The molecular chaperone heat‐shock protein 90 (Hsp90) is an essential component of the cellular homeostatic machinery in eukaryotes. Here, we show that Tsc1 is a new co‐chaperone for Hsp90 that inhibits its ATPase activity. The C‐terminal domain of Tsc1 (998–1,164 aa) forms a homodimer and binds to both protomers of the Hsp90 middle domain. This ensures inhibition of both subunits of the Hsp90 dimer and prevents the activating co‐chaperone Aha1 from binding the middle domain of Hsp90. Conversely, phosphorylation of Aha1‐Y223 increases its affinity for Hsp90 and displaces Tsc1, thereby providing a mechanism for equilibrium between binding of these two co‐chaperones to Hsp90. Our findings establish an active role for Tsc1 as a facilitator of Hsp90‐mediated folding of kinase and non‐kinase clients—including Tsc2—thereby preventing their ubiquitination and proteasomal degradation.     

Spinal cord injury reveals multilineage differentiation of ependymal cells

Spinal cord injury often results in permanent functional impairment. Neural stem cells present in the adult spinal cord can be expanded in vitro and improve recovery when transplanted to the injured spinal cord, demonstrating the presence of cells that can promote regeneration but that normally fail to do so efficiently. Using genetic fate mapping, we show that close to all in vitro neural stem cell potential in the adult spinal cord resides within the population of ependymal cells lining the central canal. These cells are recruited by spinal cord injury and produce not only scar-forming glial cells, but also, to a lesser degree, oligodendrocytes. Modulating the fate of ependymal progeny after spinal cord injury may offer an alternative to cell transplantation for cell replacement therapies in spinal cord injury.     

Novel aryl and heteroaryl substituted N-[3-(4-phenylpiperazin-1-yl)propyl]-1,2,4-oxadiazole-5-carboxamides as selective GSK-3 inhibitors

Synthesis, biological evaluation, and SAR dependencies for a series of novel aryl and heteroaryl substituted N-[3-(4-phenylpiperazin-1-yl)propyl]-1,2,4-oxadiazole-5-carboxamide inhibitors of GSK-3beta kinase are described. The inhibitory activity of the synthesized compounds is highly dependent on the character of substituents in the phenyl ring and the nature of terminal heterocyclic fragment of the core molecular scaffold. The most potent compounds from this series contain 3,4-di-methyl or 2-methoxy substituents within the phenyl ring and 3-pyridine fragment connected to the 1,2,4-oxadiazole heterocycle. These compounds selectively inhibit GSK-3beta kinase with IC(50) value of 0.35 and 0.41 microM, respectively.