Application of laser ablation–inductively coupled plasma-mass spectrometry (LA–ICP–MS) to investigate trace metal spatial distributions in human tooth enamel and dentine growth layers and pulp

Human tooth enamel provides a nearly permanent and chronological record of an individuals nutritional status and anthropogenic trace metal exposure during development; it might thus provide an excellent bio archive. We investigated the micro-spatial distribution of trace metals (Cu, Fe, Mg, Sr, Pb, and Zn) in 196×339 m² raster pattern areas (6.6×10⁴ m²) in a deciduous tooth using laser ablation-inductively coupled plasma-mass spectrometry (LA–ICP–MS). Ablated areas include prenatal and postnatal enamel, the neonatal line, the dentine–enamel junction (DEJ), dentine, and the dentine–pulp junction. Topographic variations in the surface elemental distribution of lead, zinc, strontium, and iron intensities in a deciduous tooth revealed heterogeneous distribution within and among regions. ⁴³Ca normalized elemental intensities showed the following order: Sr>Mg>>Zn>Pb>Fe>Cu. Elevated zinc and lead levels were present in the dental pulp region and at the neonatal line. This study demonstrates the ability of LA–ICP–MS to provide unique elemental distribution information in micro spatial areas of dental hard tissues. Elemental distribution plots could be useful in decoding nutrition and pollution information embedded in their bio apatite structure.Presented in part at the 2002 Winter Conference on Plasma Spectrochemistry, Scottsdale, AZ, January 6–12, 2002. The poster was selected as an outstanding poster presentation.     

Rate constants for reactions of hydroxyl radicals with nitromethane and methyl nitrite vapours at 292 K

The variations of yields of CO₂ from the gas phase H₂O₂ + NO₂ + CO chain reaction system with added nitromethane or methyl nitrite have given rate constants for reactions of OH radicals with these substrates. At 292 K these are (5.5 ± 0.6) × 10⁸ and (8.0 ± 1.1) × 10⁸ dm³ mol^?1 s^?1 respectively.     

Wannier-Stark effect on surface states

A recursive Green-function (RGF) technique is used to study the surface states of an electrified solid. The concatenating nature of the method leads to a continued-fraction form of the RGF, which can be expressed as a ratio of Bessel functions. The surface density of states (SDOS), derived from the RGF, reveals a quasi-Stark-ladder distribution of the energy levels at the surface atom. The dependence of the SDOS on the applied field and surface perturbation parameters is discussed.     

Receptor-bound conformation of an alpha(5)beta(1) integrin antagonist by (15)N-edited 2D transferred nuclear overhauser effects

We report the results of (15)N-edited 2D transferred NOE experiments of the partially (15)N-labeled alpha(5)beta(1) antagonist c[Mpa(15)N-Arg-(15)N-Gly-(15)N-Asp-(15)N-Asp-(15)N-Val-Cys]-NH(2) (Mpa denotes mercaptopropionic acid) in the presence of the native alpha(5)beta(1) receptor. The alpha(5)beta(1) integrin receptor is believed to be involved in tumor metastasis and the rational design of alpha(5)beta(1) integrin antagonist is therefore of considerable interest. Our experiments provide insight into the alpha(5)beta(1) receptor-bound conformation of the antagonist c[MpaRGDDVC]-NH2 and will be important for the design of novel antagonists.