Practical methodology for the solubility speciation analysis of ambient dust deposits for heavy metals: application to a 6-month measurement campaign

A robust and accurate method for the quantitative determination of the water-soluble and water-insoluble, Ni, Cd, Pb and Zn contents of deposited ambient dust is presented. The extraction of the soluble metal phase from deposited ambient dust has been validated using commercially available ambient dust certified reference material. Results from a 6 month measurement campaign, from July to December 2004, are presented. Quantitative analysis of the two fractions, of different aqueous solubility (referred to here as ‘solubility speciation analysis’), within deposited ambient dust is reported for the first time. Additionally, the two Bergerhoff dust deposit gauges used in parallel to acquire the dust deposit samples have shown good inter-sampler comparability. The measured total deposition fluxes compare well with those previously reported in urban and semi-rural locations around the UK.     

Changes in Preservice Teachers' Attitudes and Beliefs: The Net Impact of Two Mathematics Education Units and Intervening Experiences

Preservice teachers in a bachelor of education (Primary and ECE) program were surveyed about their beliefs and attitudes toward mathematics and its teaching and learning, at the beginning of their first mathematics curriculum unit and again at the end of their second mathematics education unit, approximately 18 months later. Significant differences were found for several items. However, in comparison to previously noted changes in the beliefs of similar cohorts from the beginning to end of a single unit, the changes were relatively small. Aspects of the course that students considered valuable and which may have contributed to the changes are also reported.     

Scope and limitations of the base-catalyzed phospha-peterson P=C bond-forming reaction

Phosphaalkenes (MesP=CRR': R = R' = Ph (1a); R = R' = 4-FC6H4 (1b); R = Ph, R' = 4-FC6H4 (1c); R = R' = 4-OMeC6H4 (1d); R = Ph, R' = 4-OMeC6H4 (1e); R = Ph, R' = 2-pyridyl (1f)) are prepared from the reaction of MesP(SiMe3)2 and O=CRR' in the presence of a trace of KOH or NaOH. The base-catalyzed phospha-Peterson reaction is quantitated by NMR spectroscopy, and isolated yields of phosphaalkene between 40 and 70% are obtained after vacuum distillation and/or recrystallization. The asymmetrically substituted phosphaalkenes (1c, 1e, 1f) form as 1:1 mixtures of E and Z isomers; however, X-ray crystallography reveals that the E isomers crystallize preferentially. Interestingly, E-1e and E-1f readily isomerize in solution in the dark, although the rate of isomerization is much faster when samples are exposed to light. X-ray crystal structures of 1b, E-1e, and E-1f reveal that the P=C bond lengths (average of 1.70 A) are in the long end of the range typically found in phosphaalkenes (1.61-1.71 A). Attempts to prepare isolable P-adamantyl phosphaalkenes following this route were unsuccessful. Although AdP=CPh2 (2a) is detected by 31P NMR spectroscopy, attempts to isolate this species afforded the 1,2-diphosphetane (AdPCPh2)2 (3a), which was characterized by X-ray crystallography.     

Efficient Innate Immune Killing of Cancer Cells Triggered by Cell‐Surface Anchoring of Multivalent Antibody‐Recruiting Polymers

Binding of monoclonal antibodies (mAbs) onto a cell surface triggers antibody‐mediated effector killing by innate immune cells through complement activation. As an alternative to mAbs, synthetic systems that can recruit endogenous antibodies from the blood stream to a cancer cell surface could be of great relevance. Herein, we explore antibody‐recruiting polymers (ARPs) as a novel class of immunotherapy. ARPs consist of a cell‐binding motif linked to a polymer that contains multiple small molecule antibody‐binding motifs along its backbone. As a proof of concept, we employ a lipid anchor that inserts into the phospholipid cell membrane and make use of a polymeric activated ester scaffold onto which we substitute dinitrophenol as an antibody‐binding motif. We demonstrate that ARPs allow for high avidity antibody binding and drive antibody recruitment to treated cells for several days. Furthermore, we show that ARP‐treated cancer cells are prone to antibody‐mediated killing through phagocytosis by macrophages.     

Carboxy-terminated oligo(ethylene glycol)-alkane phosphate: synthesis and self-assembly on titanium oxide surfaces

The surface immobilization of oligo- and poly(ethylene glycol) on solids is a widely used approach to prevent the nonspecific adsorption of proteins, bacteria, and cells. A novel tri(ethylene glycol) derivative, phosphoric acid-mono(22-carboxy-12,15,18,21-tetraoxadocosyl) ester, was synthesized with the aim to produce self-assembled monolayers (SAMs) on metal/metal oxide surfaces. This compound contains two reactive, terminal moieties: the phosphoric acid group as anchor to the surface, and the carboxylic group as linker for further attachment of molecules such as peptides and proteins to be present at the surface. The adsorption on titanium-dioxide-coated substrates was studied quantitatively and the resulting SAMs were characterized by angle-dependent X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry. XPS data showed that the monomolecular layer is attached with the phosphate group to the substrate, but not fully ordered. The dry adlayer thickness was determined to be 13.4 A, which is less than expected for a densely packed monolayer. Surface concentration calculated from ellipsometry data resulted in a grafting density of 2.03 molecules/nm2.     

Enantioselective synthesis of bridged bicyclic ring systems

The type 2 intramolecular Diels-Alder (IMDA) reaction is a valuable method for synthesis of both carbocyclic and heterocyclic bridged bicyclo[5.3.1]undecane and bicyclo[4.3.1]decane ring systems. These structures are common to a number of biologically important natural products. Asymmetric variants of the type 2 IMDA reaction incorporating oxazolidinone chiral auxiliaries have been evaluated. This study has resulted in systems that deliver bridged bicyclic [5.3.1] and [4.3.1] ring systems in high diastereomeric (97-99% de) and enantiomeric purity.     

An analytical derivation of a popular approximation of the Voigt function for quantification of NMR spectra

The approximation of the Voigt line shape by the linear summation of Lorentzian and Gaussian line shapes of equal width is well documented and has proved to be a useful function for modeling in vivo (1)H NMR spectra. We show that the error in determining peak areas is less than 0.72% over a range of simulated Voigt line shapes. Previous work has concentrated on empirical analysis of the Voigt function, yielding accurate expressions for recovering the intrinsic Lorentzian component of simulated line shapes. In this work, an analytical approach to the approximation is presented which is valid for the range of Voigt line shapes in which either the Lorentzian or Gaussian component is dominant. With an empirical analysis of the approximation, the direct recovery of T(2) values from simulated line shapes is also discussed.     

Using ion imaging to analyze higher-order moments of the angular distributions of photofragments

We investigate the effect of the hexadecapole (K=4) polarization moment on the spatial distributions of angular momenta for atoms produced during the photodissociation of diatomic or triatomic molecules by polarized radiation. We derive general expressions for the angular distributions of the atomic density matrix for K = 2, 4 and expressions for the corresponding anisotropy parameters that contain all information on the photodissociation dynamics. We show that these anisotropy parameters can be experimentally determined by using ion imaging. We consider oxygen atoms in the ¹ D ₂ state aligned with respect to the orbital angular momentum as an example and provide ion images of the signals that correspond to the population of the atomic magnetic sublevels ¦m¦ = 0, 1, 2. We show the contributions from the second-and fourth-rank state multipoles to the angular distributions of the atomic density matrix to be comparable in magnitude and significantly different in form.