Human R-1,3-fucosyltransferase V (FucT V), which catalyzes the transfer of L-fucose moiety from guanosine diphosphate -L-fucose (GDP-Fuc) to an acceptor sugar to form sialyl Lewis x (sLe x ), was shown to proceed through an ordered, sequential mechanism by product inhibition studies. The designed azatrisaccharide propyl 2-acetamido- (2), prepared by covalently linking the N-group of -L-homofuconojirimycin (1) to the 3-OH of LacNAc through an ethylene unit, in the presence of GDP was found to be an effective inhibitor of FucT V. In the presence of 30 µM GDP, the concentration of 2 necessary to cause 50% inhibition was reduced 77-fold to 31 µM. Presumably, the azatrisaccharide and GDP form a complex which mimics the transition state of the enzymatic reaction. Given the low affinity of FucT V for its substrate LacNAc (K m ) 35 mM), the designed azatrisaccharide in the presence of GDP represents the most potent synergistic inhibitor complex reported so far.
Gold nanoparticles have been used for centuries, both for decoration and in medical applications. More recently, many of the major advances in cluster chemistry have involved welldefined clusters containing tens or hundreds of atoms, either with or without a ligand shell. In this paper we report the synthesis of two gold/lead clusters, [Au 8 Pb 33 ] 6− and [Au 12 Pb 44 ] 8− , both of which contain nido [Au@Pb 11 ] 3− icosahedra surrounding a core of Au atoms. Analogues of these large clusters are not found in the corresponding Ag chemistry: instead, the Ag-centered nido icosahedron, [Ag@Pb 11 ] 3− , is the only isolated product. The structural chemistry, along with the mass spectrometry which shows the existence of [Au 2 Pb 11 ] 2− but not [Ag 2 Pb 11 ] 2− , leads us to propose that the former species is the key intermediate in the growth of the larger clusters. Density functional theory indicates that secondary π-type interactions between the [Au@Pb 11 ] 3− ligands and the gold core play a significant part in stabilizing the larger clusters.
We report the synthesis of two new cluster anions [Cu4@E18] 4-(E = Sn, Pb), in which a Cu4 subunit is incorporated into a continuous E18 tetrel cage. Both anions are characterized by X-ray crystallography and mass spectrometry, complemented by quantum chemical calculations which highlight the relationships to known Zintl clusters including the stannaspherenes and plumbaspherenes, [M@Sn12] qand [M@Pb12] q-, the Matryoshka bronze [Sn@Cu12@Sn20] 12and also [Pd2@E'18] 4-(E' = Ge, Sn). Figure 5. Comparison of the structures and frontier Kohn-Sham orbitals of D2h-symmetric [Cu2@Sn18] 6and D3d-symmetric [Cu2@Sn18] 2viewed down the conserved C2 axis. The middle of the HOMO-LUMO gap is taken as the zero of energy for all three clusters.ASSOCIATED CONTENT Supporting Information. The detailed experimental procedures, crystallographic supplementation, electrospray ionization mass spectrometry (ESI-MS) analysis, energy dispersive X-ray (EDX) spectroscopic analysis, and quantum chemical studies.
We reported the high strength of magnetoelectric (ME) coupling of trilayered
composites prepared by electro-deposition. The ME coupling of Ni–lead
zirconate titanate–Ni trilayered structure was measured in the range of
1–120 kHz. The trilayered composites exhibit high ME voltage coefficient because
of good interfacial bonding between piezoelectric and magnetostrictive
layers. The peak value of the ME voltage coefficient can be up to
33 V cm−1 Oe−1
at the electromechanical resonance frequency. This magnetoelectric effect shows promise for
application in transducers for magnetoelectric energy conversion.
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