Surface studies of halloysite nanotubes by XPS and ToF‐SIMS

This report provides detailed experimental results of thermal and surface characterization on untreated and surface‐treated halloysite nanotubes (HNTs) obtained from two geographic areas. Surface characterization techniques, including XPS and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) were used. ToF‐SIMS surface analysis experiments were performed with both atomic and cluster ion beams. Higher ion yields and more high‐mass ions were obtained with the cluster ion beams. Static ToF‐SIMS spectra were analyzed with principal component analysis (PCA). Morphological diversities were observed in the samples although they mainly contained tubular structures. Thermogravimetric data indicated that aqueous hydrogen peroxide solution could remove inorganic salt impurities, such as alkali metal salts. The amount of grafting of benzalkonium chloride of HNT surface was determined by thermogravimetic analysis. PCA of ToF‐SIMS spectra could distinguish the samples mined from different geographical locations as well as among surface‐treated and untreated samples. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimization of separation of heavy metals by capillary electrophoresis with contactless conductivity detection

The separation of four toxic metal ions (Cr(3+) , Pb(2+) , Hg(2+) , Ni(2+) ) was achieved by optimizing the composition of the histidine/tartaric acid background electrolyte. An on-column preconcentration technique, viz. field amplified sample injection, was performed to improve the sensitivity. This method afforded an enhancement factor of up to 91,800 fold with the LODs ranging from 0.005 to 2.32 μg/L, which were well below the maximum contaminant levels set by the United States Environmental Protection Agency. The robustness of this method was demonstrated with its application to the analysis of real samples including tap water, drain water, and reservoir water with recoveries between 90 and 120%.     

Ultrasensitive and selective DNA detection by hydroxylamine assisted gold nanoparticle amplification

A new nanoparticle-based chemiluminescent (CL) method has been developed for the ultrasensitive detection of DNA hybridization which can achieve ultra-sensitivity up to approximately 30 zmol, i.e. 300 aM.     

One-pot three-enzyme synthesis of UDP-GlcNAc derivatives

A Pasteurella multocida N-acetylglucosamine 1-phosphate uridylyltransferase (PmGlmU) was cloned and used efficiently with an N-acetylhexosamine 1-kinase (NahK_ATCC55813) and an inorganic pyrophosphatase (PmPpA) for one-pot three-enzyme synthesis of UDP-GlcNAc derivatives with or without further chemical diversification.     

Novel heterobimetallic ruthenium(III)-cobalt(II) compounds constructed from trans-[Ru(III)(Q)2(CN)2](-) (Q = 8-quinolinolato): synthesis, structures and magnetic properties

Reaction of [Ru(II)(PPh(3))(3)Cl(2)] with HQ and KCN produces a new dicyanoruthenium(III) building block, [Ru(III)(Q)(2)(CN)(2)](-). It reacts with hydrated CoCl(2) in MeOH or DMF to produce a trinuclear compound 2 or a 1-D zigzag chain 3.     

Sensitive Morphological Characterization of Oriented High-Density Lipoprotein Nanoparticles Using 31P NMR Spectroscopy

The biological function of high-density lipoprotein (HDL) nanoparticles, the so-called good cholesterol that is associated with a low risk of heart disease, depends on their composition, morphology, and size. The morphology of HDL particles composed of apolipoproteins, lipids and cholesterol is routinely visualised by transmission electron microscopy (TEM), but higher-resolution tools are needed to observe more subtle structural differences between particles of different composition. Here, reconstituted HDL formulations are oriented on glass substrates and solid-state ³¹P NMR spectroscopy is shown to be highly sensitive to the surface curvature of the lipid headgroups. The spectra report potentially functionally important differences in the morphology of different HDL preparations that are not detected by TEM. This method provides new morphological insights into HDL comprising a naturally occurring apolipoprotein A-I mutant, which may be linked to its atheroprotective properties, and holds promise as a future research tool in the clinical analysis of plasma HDL.     

Fragmentation Chemistry of [Met-Gly]•+, [Gly-Met]•+, and [Met-Met]•+ Radical Cations

Radical cations [Met-Gly]^?+, [Gly-Met]^?+, and [Met-Met]^?+ have been generated through collision-induced dissociation (CID) of [Cu^II(CH₃CN)₂(peptide)]^?2+ complexes. Their fragmentation patterns and dissociation mechanisms have been studied both experimentally and theoretically using density functional theory at the UB3LYP/6-311++G(d,p) level. The captodative structure, in which the radical is located at the α-carbon of the N-terminal residue and the proton is on the amide oxygen, is the lowest energy structure on each potential energy surface. The canonical structure, with the charge and spin both located on the sulfur, and the distonic ion with the proton on the terminal amino group, and the radical on the α-carbon of the C-terminal residue have similar energies. Interconversion between the canonical structures and the captodative isomers is facile and occurs prior to fragmentation. However, isomerization to produce the distonic structure is energetically less favorable and cannot compete with dissociation except in the case of [Gly-Met]^?+. Charge-driven dissociations result in formation of [b _n – H]^?+ and a ₁ ions. Radical-driven dissociation leads to the loss of the side chain of methionine as CH₃-S-CH?=?CH₂ producing α-glycyl radicals from both [Gly-Met]^?+ and [Met-Met]^?+. For [Met-Met]^?+, loss of the side chain occurs at the C-terminal as shown by both labeling experiments and computations. The product, the distonic ion of [Met-Gly]^?+, NH₃ ⁺CH(CH₂CH₂SCH₃)CONHCH^?COOH dissociates by loss of CH₃S^?. The isomeric distonic ion NH₃ ⁺CH₂CONHC^?(CH₂CH₂SCH₃)COOH is accessible directly from the canonical [Gly-Met]^?+ ion. A fragmentation pathway that characterizes this ion (and the distonic ion of [Met-Met]^?+) is homolytic fission of the C_β–C_γ bond to lose CH₃SCH₂ ^?.