Integral Cohomology and Detection of -basic 2-groups

In this paper we compute the cohomology of all -basic 2-groups with integral coefficients twisted by the orientation character . We also calculate appropriate restiction maps and thus prove that the cohomology of any -basic group is detected by subgroups isomorphic to one of five types, and we provide a sample application of this main theorem.

     

Asymptotic optimality of statistical multiplexing in pipelined processing

The throughput of pipelined processing ofheterogeneous multitasked jobs is computed and optimized in this study. There areK job classes. Each job hasM tasks which have to be processed in a given order (same for all tasks) on a pipeline ofM processors. Tasks have random processing times. The jobs of each class form a stationary and ergodic sequence (with respect to their task processing times). Classes are differentiated by distinct statistics and may not be jointly stationary or ergodic. Thus, the jobs are overall statistically heterogeneous. We are interested in the average execution time per job , when the job populations of the various classes become very large (asymptotically). This is shown to depend on the order in which jobs enter the pipeline. Under the natural class-based ordering, where all jobs of the first class enter first, followed by those of the second, third, and so on, the quantity is computed, but is shownnot to attain its minimal value in general. On the contrary, appropriate statistical multiplexing of jobs of different classes on the pipeline is shown to minimize the average execution time per job on every sample path (with probability one). The procedure, calledbalanced statistical multiplexing, is constructed and the minimal is computed in terms of the average execution times of the job tasks.     

Influence of methanol as a buffer additive on the mobilities of organic cations in capillary electrophoresis

The mobilities of a series of aromatic ammonium ions, ranging in charge from +1 to + 3, were investigated by capillary electrophoresis using buffers consisting of 0-75% v/v methanol. This is an extension of our previous studies involving anion mobility in methanol-water media [1]. Absolute mobilities were determined by extrapolation of the effective mobilities to zero ionic strength according to the Pitts' equation. For all of the buffer compositions studied, the ionic strength effect increased with increasing cation charge, and varied as a function of solvent 1/eta epsilon (1/2) as predicted by the electrophoretic term within the Pitts' equation. In the presence of methanol, the ionic strength effects became more dramatic. The absolute mobilities of the cations were altered by the addition of methanol to the electrophoretic media. For example, at 75% MeOH, a migration order reversal was observed between the + 2 and + 3 ammonium ions. These solvent-induced selectivity changes are attributed to dielectric friction. As predicted by the Hubbard-Onsager dielectric friction model, dielectric friction increased with increasing methanol content and with increasing analyte charge. Further, the changes in cation mobility correlated to the changes in solvent relaxation time (tau), epsilon and eta. Although not predicted by the Hubbard-Onsager theory, the + 3 ammonium ion experienced more dielectric friction than the - 3 sulfonate and - 3 carboxylate investigated previously [1]. This apparent failure of the Hubbard-Onsager model results from its continuum nature, whereby ion-solvent interactions are not taken into account.     

Bromoporphyrins as versatile synthons for modular construction of chiral porphyrins: cobalt-catalyzed highly enantioselective and diastereoselective cyclopropanation

5,10-Bis(2',6'-dibromophenyl)porphyrins bearing various substituents at the 10 and 20 positions were demonstrated to be versatile synthons for modular construction of chiral porphyrins via palladium-catalyzed amidation reactions with chiral amides. The quadruple carbon-nitrogen bond formation reactions were accomplished in high yields with different chiral amide building blocks under mild conditions, forming a family of D2-symmetric chiral porphyrins. Cobalt(II) complexes of these chiral porphyrins were prepared in high yields and shown to be active catalysts for highly enantioselective and diastereoselective cyclopropanation under a practical one-pot protocol (alkenes as limiting reagents and no slow addition of diazo reagents).     

Quantitative determination of the polypeptide motilin in rat plasma by externally calibrated liquid chromatography/electrospray ionization mass spectrometry

We present a method for the quantitation of motilin from rat plasma by protein precipitation and liquid chromatography/mass spectrometry (LC/MS). Using external calibration, the method was linear over the concentration range 10-1000 ng/mL with an initial sample volume of 150 microL. The LC system included a C(18) column with a 300 A pore size. A linear gradient was used with a mobile phase consisting of water and acetonitrile, each with 0.2% acetic acid and 0.02% trifluoroacetic acid. Motilin was detected with the mass spectrometer in positive ion mode monitoring the 4+ charge state at m/z 675.5. The approximated limit of detection was less than 1 ng/mL and the lower limit of quantitation (LLOQ) was 10 ng/mL. The method showed a high degree of precision and accuracy both within and between runs at five validation points, including the LLOQ.     

Infrared detection of a phenylboronic acid terminated alkane thiol monolayer on gold surfaces

Polarization modulation infrared reflectance absorption spectroscopy (PM-IRRAS) and infrared reflectance absorption spectroscopy (IRRAS) have been used to characterize the formation of a self-assembled monolayer of N-(3-dihydroxyborylphenyl)-11-mercaptoundecanamide) (abbreviated PBA) on a gold surface and the subsequent binding of various sugars to the PBA adlayer through the phenylboronic acid moiety to form a phenylboronate ester. Vibrationally resonant sum frequency generation (VR-SFG) spectroscopy confirmed the ordering of the substituted phenyl groups of the PBA adlayer on the gold surface. Solution FTIR spectra and density functional theory were used to confirm the identity of the observed vibrational modes on the gold surface of PBA with and without bound sugar. The detection of the binding of glucose on the gold surface was confirmed in part by the presence of a C-O stretching mode of glucose and the observed O-H stretching mode of glucose that is shifted in position relative to the O-H stretching mode of boronic acid. An IR marker mode was also observed at 1734 cm(-1) upon the binding of glucose. Additionally, changes in the peak profile of the B-O stretching band were observed upon binding, confirming formation of a phenylboronate ester on the gold surface. The binding of mannose and lactose were also detected primarily through the IR marker mode at approximately 1736 to 1742 cm(-1) depending on the identity of the bound sugar.     

Immobilization of proteins on carboxylic acid functionalized nanopatterns

The immobilization of proteins on nanopatterned surfaces was investigated using in situ atomic force microscopy (AFM) and ex situ infrared reflectance–absorption spectroscopy (IRAS). The AFM-based lithography technique of nanografting provided control of the size, geometry, and spatial placement of nanopatterns within self-assembled monolayers (SAMs). Square nanopatterns of carboxylate-terminated SAMs were inscribed within methyl-terminated octadecanethiolate SAMs and activated using carbodiimide/succinimide coupling chemistry. Staphylococcal protein A was immobilized on the activated nanopatterns before exposure to rabbit immunoglobulin G. In situ AFM was used to monitor changes in the topography and friction of the nanopatterns in solution upon protein immobilization. Complementary studies with ex situ IRAS confirmed the surface chemistry that occurred during the steps of SAM activation and subsequent protein immobilization on unpatterned samples. Since carbodiimide/succinimide coupling chemistry can be used for surface attachment of different biomolecules, this protocol shows promise for development of other aqueous-based studies for nanopatterned protein immobilization.     

Halogenated Flavonoid Derivatives Display Antiangiogenic Activity

Antiangiogenic agents attenuate tumours’ growth and metastases and are therefore beneficial as an adjuvant or standalone cancer regimen. Drugs with dual antiproliferative and antiangiogenic activities can achieve anticancer efficacy and overcome acquired resistance. In this study, synthetic flavones (5a,b) with reported anticancer activity, and derivatives (4b and 6a), exhibited significant inhibition of endothelial cell tube formation (40–55%, 12 h) at 1 µM, which is comparable to sunitinib (50% inhibition at 1 µM, 48 h). Flavones (4b, 5a,b and 6a) also showed 25–37% reduction in HUVECs migration at 10 µM. In a Western blotting assay, 5a and 5b subdued VEGFR2 phosphorylation by 37% and 57%, respectively, suggesting that VEGFR2 may be their main antiangiogenic target. 5b displayed the best docking fit with VEGFR2 in an in silico study, followed by 5a, emphasizing the importance of the 7-hydroxyl group accompanied by a 4−C=S for activity. Conversely, derivatives with a 4-carbonyl moiety fitted poorly into the target’s binding pocket, suggesting that their antiangiogenic activity depends on a different target. This study provides valuable insight into the Structure Activity Relationships (SAR) and modes of action of halogenated flavones with VEGFR2 and highlights their therapeutic potential as antiangiogenic/anticancer lead compounds.     

Syntheses of Benzo[b]furan-6-carbonitrile and 6-Cyanobenzo[b]furan-2-boronic Acid Pinacol Ester

6-Cyanobenzo[b]furan-2-boronic acid pinacol ester (10) is a potentially useful two-point scaffold for the construction of specific compounds or compound libraries with benzofuran cores. Using a per-iodination/de-iodination strategy coupled with Sonogashira alkynylation and Cu-catalyzed heteroannulation, we have developed a procedure that allows the preparation of benzo[b]furan-6-carbonitrile (9) and 6-cyanobenzo[b]furan-2-boronic acid pinacol ester (10) in gram quantities.

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