Detection of opium alkaloids in a Cypriot base-ring juglet.

A method has been developed for extracting poppy alkaloids from oily matrices, specifically lipid residues associated with archaeological ceramics. The protocol has been applied to fresh and artificially aged poppyseed oil and to residue from a Late Bronze Age Cypriot juglet in the collections of the British Museum. The juglet is of a type that has been linked with ancient trade in opium due to its poppy-head shape and wide distribution; it is a rare example of an intact vessel with contents sealed inside. Bulk analysis of the residue by GC-EI-MS and pyGC-EI-MS indicated a degraded plant oil and possible presence of papaverine. Analysis of the alkaloid extracts by HPLC-ESI-MS using both triple quadrupole and FTICR mass spectrometers detected the five primary opium alkaloids in fresh poppyseed oil and papaverine in most of the aged samples. Papaverine and thebaine were detected in the juglet residue, providing the first rigorous chemical evidence to support a link between this vessel type and opium, or at least poppies. The association of opium with oil raises new questions about the ancient purpose of the commodities within these vessels, and the low levels (ng g-1) of opiates detected in this unusually well-preserved residue shed doubt on the scope for their detection in more fragmentary ceramic remains (potsherds). Papaverine was found to exhibit challenging carryover behaviour in all the analytical methods used in this study. The phenomenon has not been reported before and should be considered in future analyses of this analyte in all application areas.

Observation of single colloidal platinum nanocrystal growth trajectories.

Understanding of colloidal nanocrystal growth mechanisms is essential for the syntheses of nanocrystals with desired physical properties. The classical model for the growth of monodisperse nanocrystals assumes a discrete nucleation stage followed by growth via monomer attachment, but has overlooked particle-particle interactions. Recent studies have suggested that interactions between particles play an important role. Using in situ transmission electron microscopy, we show that platinum nanocrystals can grow either by monomer attachment from solution or by particle coalescence. Through the combination of these two processes, an initially broad size distribution can spontaneously narrow into a nearly monodisperse distribution. We suggest that colloidal nanocrystals take different pathways of growth based on their size- and morphology-dependent internal energies.

Sulfidation of cadmium at the nanoscale.

We investigate the evolution of structures that result when spherical Cd nanoparticles of a few hundred nanometers in diameter react with dissolved molecular sulfur species in solution to form hollow CdS. Over a wide range of temperatures and concentrations, we find that rapid Cd diffusion through the growing CdS shell localizes the reaction front at the outermost CdS/S interface, leading to hollow particles when all the Cd is consumed. When we examine partially reacted particles, we find that this system differs significantly from others in which the nanoscale Kirkendall effect has been used to create hollow particles. In previously reported systems, partial reaction creates a hollow particle with a spherically symmetric metal core connected to the outer shell by filaments. In contrast, here we obtain a lower symmetry structure, in which the unreacted metal core and the coalesced vacancies separate into two distinct spherical caps, minimizing the metal/void interface. This pattern of void coalescence is likely to occur in situations where the metal/vacancy self-diffusivities in the core are greater than the diffusivity of the cations through the shell.

Spectral diffusion in the tunneling spectra of ligand-stabilized undecagold clusters.

We report diffusion in the tunneling spectra of isolated, ligand-stabilized undecagold (Au11) clusters immobilized by attachment to alpha,omega-alkanedithiolate tethers inserted into alkanethiolate self-assembled monolayers. We use scanning tunneling microscopy and spectroscopy at cryogenic (UHV, 4 K) conditions to measure these clusters' conductance with complete control of their chemical and physical environment; additionally, thermal broadening of their electronic states as well as their mobility is minimized. At low temperature, the Au11 clusters demonstrate Coulomb blockade behavior, with zero-conductance gaps resulting from quantum size effects. Surprisingly, chemically identical and even single particles produced different families of tunneling spectra, comparable to previous results for heterogeneous distributions of particles. We hypothesize that, while these particles are chemically attached to the surface of the SAM for measurement, these assemblies may still be sufficiently dynamic to affect their transport properties significantly.

Molecular engineering and measurements to test hypothesized mechanisms in single molecule conductance switching.

Six customized phenylene-ethynylene-based oligomers have been studied for their electronic properties using scanning tunneling microscopy to test hypothesized mechanisms of stochastic conductance switching. Previously suggested mechanisms include functional group reduction, functional group rotation, backbone ring rotation, neighboring molecule interactions, bond fluctuations, and hybridization changes. Here, we test these hypotheses experimentally by varying the molecular designs of the switches; the ability of the molecules to switch via each hypothetical mechanism is selectively engineered into or out of each molecule. We conclude that hybridization changes at the molecule-surface interface are responsible for the switching we observe.

MASK, a large ankyrin repeat and KH domain-containing protein involved in Drosophila receptor tyrosine kinase signaling.

The receptor tyrosine kinases Sevenless (SEV) and the Epidermal growth factor receptor (EGFR) are required for the proper development of the Drosophila eye. The protein tyrosine phosphatase Corkscrew (CSW) is a common component of many RTK signaling pathways, and is required for signaling downstream of SEV and EGFR. In order to identify additional components of these signaling pathways, mutations that enhanced the phenotype of a dominant negative form of Corkscrew were isolated. This genetic screen identified the novel signaling molecule MASK, a large protein that contains two blocks of ankyrin repeats as well as a KH domain. MASK genetically interacts with known components of these RTK signaling pathways. In the developing eye imaginal disc, loss of MASK function generates phenotypes similar to those generated by loss of other components of the SEV and EGFR pathways. These phenotypes include compromised photoreceptor differentiation, cell survival and proliferation. Although MASK is localized predominantly in the cellular cytoplasm, it is not absolutely required for MAPK activation or nuclear translocation. Based on our results, we propose that MASK is a novel mediator of RTK signaling, and may act either downstream of MAPK or transduce signaling through a parallel branch of the RTK pathway.