Double Hilbert transform along real-analytic surfaces in Rd+2

We give a necessary and sufficient condition for the doubleHilbert transform on ^d+2 to be bounded on L^p, 1 < p <. This generalizes a result of Carbery, Wainger and Wright [DukeMath. J. 101 (2000) 499–513] for d = 1.     

Tripodal naphthalene ether ligand: Solid-state anion recognition and fluorescence studies

The simple tripodal amine ligand Tris-[2-(naphthalen-1-yloxy)-ethyl]-amine (L₁) was screened for anion recognition. Four crystal structures confirmed the inorganic as well as organic anion recognition in the solid state. Solid-state structures are results of supramolecular self-assembly and 3D molecular network involves C–HO and C–Hπ bonding in the crystal lattice. In the solid state, it forms a strong C–HCl and C–HO type interactions with the anions. This anion recognition was also confirmed by steady state fluorescence spectroscopy. In complex 4, L₁ is confined between 2D hydrogen bonded sheet formed by pyromellitic acid anion. L₁ shows unusually high selectivity toward nitrate in solution resulting in both a dramatic color change and a concomitant quenching of luminescence.     

Structure of light neutron-rich nuclei through coulomb dissociation

Coulomb breakup of neutron-rich nuclei around mass A ∼ 20 has been studied experimentally using secondary beams (∼ 500–600 MeV/u) of unstable nuclei produced at GSI. The spectroscopic factor deduced for the neutron occupying s _1/2 level in ¹⁵C ground state is consistent with the earlier reported value. The data analysis for Coulomb breakup of ¹⁷C shows that most of the cross section yields the ¹⁶C core in its excited state. For ^17–22O, the low-lying E1 strength amounts up to about 12% of the energy weighted dipole sum rule strength depending on neutron excess. The cluster sum rule limit with ¹⁶O as a core is almost exhausted for ^17,18O, while for more neutron rich isotopes the strength with respect to that limit decreases.     

Application of electrospray mass spectrometry in probing protein-protein and protein-ligand noncovalent interactions

A novel mass spectrometry-based methodology using electrospray ionization (ESI) is described for the detection of protein-protein [interferon (IFN)-γ dimer] and protein-ligand [ras-guanosine diphosphate (GDP)] noncovalent interactions. The method utilizes ESI from aqueous solution at appropriate pH. The presence of the noncovalent complex of the IFN-γ dimer was confirmed by the observed average molecular weight of 33,819 Da. The key to the detection of the IFN-γ dimer is the use of an alkaline solution (pH ≈ 9) for sample preparation and for mass spectrornetry analysis. The effect of the declustering energy in the region of the ion sampling orifice and focusing quadrupole on the preservation of the gas-phase noncovalent complex (IFN-γ dimer) was also studied. The effect of the declustering energy on complex dissociation was further extended to probe the noncovalent protein-ligand association of ras-GDP. It was found that little energy is required to dissociate the IFN-γ dimer, whereas a substantial amount of energy is required to dissociate the gas-phase ras-GDP complex.     

A Toggle Nanoswitch Alternately Controlling Two Catalytic Reactions

Reversible switching between two states of the triangular nanoswitch [Cu( 1 )]⁺ was accomplished by alternate addition of 2‐ferrocenyl‐1,10‐phenanthroline ( 2 ) and copper(I) ions. The two switching states regulate the binding and release of two distinct catalysts, piperidine and [Cu( 2 )]⁺, in a fully interference‐free manner and allow alternating on/off switching of two orthogonal catalytic processes. In switching state I, piperidine is released from the nanoswitch and catalyzes a Knoevenagel addition between 4‐nitrobenzaldehyde and diethyl malonate (ON‐1 and OFF‐2), while in state II the released [Cu( 2 )]⁺ catalyzes a click reaction between 4‐nitrophenylacetylene and benzylazide (OFF‐1 and ON‐2). Upon addition of one equivalent of 2 to the (OFF‐1 and ON‐2)‐state, both catalytically active processes are shut down (OFF‐1 and OFF‐2).     

Spectroscopic studies of 2-(2-bromo-ethyl)-6-nitro-benzo[de]isoquinolene-1,3-dione in water/alkanol mixed solvents and nonionic micelle of Igepal CO series

Spectroscopic studies of newly synthesized bioactive compound 2-(2-bromo-ethyl)-6-nitro-benzo[de]isoquinolene-1,3-dione (BNBIO) have been carried out in polar aprotic solvent, viz. acetonitrile, tetrahydrofuran, 1,4-dioxan, ethylene glycol, dimethyl formamide, and polar protic solvent, viz. methanol, ethanol, propanol, water. Variation in absorbance of BNBIO in water-methanol, water-ethanol and water-propanol mixtures at their different compositions have been observed. Absorption behaviour of the dye has been studied in poly(oxyethylene) nonylphenol surfactants Igepal CO 630, Igepal CO 720 and Igepal CO 890 containing same hydrophobic tail and different numbers of poly(oxyethylene) groups. Experimental results of the BNBIO nonionic micelles have been explained in terms of 1:1 electron donor-acceptor (EDA) complexation and the complexation equilibrium becomes suppressed with increasing number of poly(oxyethylene) residue on the Igepal surfactant. Variation in binding constant of dye-micelle complexation has been rationalized considering a competitive equilibrium process between the BNBIO-water interactions.     

Synthesis and photocatalytic oxidation of different organic dyes by using Mn2O3/TiO2 solid solution and visible light

Mn₂O₃/TiO₂ solid solution was prepared from two different oxides, manganese oxide (from KMnO₄ and ethanol) and TiO₂, these samples were characterized by BET, XRD, EDAX, SEM, FT-IR, ESR, XPS and UV–vis absorption spectroscopy. Photocatalytic activities of Mn₂O₃/TiO₂ powder was investigated by photooxidation of different dyes like Rhodamine B, thymol blue, methyl orange and Bromocresol green under visible light (300-W Xe lamp; λ > 420 nm). The results show that the alloy of TiO₂ with 1 mol% of Mn₂O₃ (MNT1) exhibit photocatalytic activity 3–5 times higher than that of P25 TiO₂ for oxidation of various dyes (RB, TB, MO and BG). The average particle size and crystallite size of MNT1 were found to be 100 nm and 12 nm measured from SEM and XRD, respectively. The EPR spectra of the Mn₂O₃/TiO₂ samples is a sharp five-line Mn(III) component centered on g_eff = 1.99.     

Applications of LC/MS in structure identifications of small molecules and proteins in drug discovery

With advancements in ionization methods and instrumentation, liquid chromatography/mass spectrometry (LC/MS) has become a powerful technology for the characterization of small molecules and proteins. This article will illustrate the role of LC/MS analysis in drug discovery process. Examples will be given on high-throughput analysis, structural analysis of trace level impurities in drug substances, identification of metabolites, and characterization of therapeutic protein products for process improvement. Some unique MS techniques will also be discussed to demonstrate their effectiveness in facilitating structural identifications.     

Amyloid‐Like Fibrillogenesis through Supramolecular Helix‐Mediated Self‐Assembly of Tetrapeptides Containing Non‐Coded α‐Aminoisobutyric Acid (Aib) and 3‐Aminobenzoic Acid (m‐ABA)

Single‐crystal X‐ray diffraction studies of two terminally protected tetrapeptides Boc‐Ile‐Aib‐Val‐m‐ABA‐OMe ( I ) and Boc‐Ile‐Aib‐Phe‐m‐ABA‐OMe ( II ) (Aib=α‐aminoisobutyric acid; m‐ABA=meta‐aminobenzoic acid) reveal that they form continuous H‐bonded helices through the association of double‐bend (type III and I) building blocks. NMR Studies support the existence of the double‐bend (type III and I) structures of the peptides in solution also. Field emission scanning electron‐microscopic (FE‐SEM) and high‐resolution transmission electron‐microscopic (HR‐TEM) images of the peptides exhibit amyloid‐like fibrils in the solid state. The Congo red‐stained fibrils of peptide I and II , observed between crossed polarizers, show green‐gold birefringence, a characteristic of amyloid fibrils.