Orientation dependence of overlayer attenuation of electrons for the cylindrical mirror analyzer and a retarding field analyzer

The effect of a homogeneous flat overlayer in attenuating spectral lines is analyzed as a function of orientation for apertures corresponding to a 42.3° cylindrical mirror analyzer and 48° retarding field analyzer. Exponential attenuation with path length is assumed. Results are presented graphically for both isotropic and cosine distributions of sources. The numerical results are particularly useful when practical considerations require the use of an unsymmetrical sample orientation. The results are pertinent to measurements of inelastic mean free paths and are also related to the response of these spectrometers to different depth distributions of elements.     

Photochemistry of methylenenitrones and related compounds. A study of oxaziridine and nitrene formation

A series of N-alkylmethylenenitrones has been prepared and can be irradiated cleanly to simple N-alkyloxaziridines. Further irradiations of these systems lead to N-alkylformamides via a singlet state rearrangement process. Triplet state fragmentation to give amines, presumably via alkyl nitrenes, has been observed but with very low efficiency. Only N-aryl systems appear to lead to significant nitrene formation.     

Synthesis of NanoQ, a copper-based contrast agent for high-resolution magnetic resonance imaging characterization of human thrombus

A new site-targeted molecular imaging contrast agent based on a nanocolloidal suspension of lipid-encapsulated, organically soluble divalent copper has been developed. Concentrating a high payload of divalent copper ions per nanoparticle, this agent provides a high per-particle r1 relaxivity, allowing sensitive detection in T1-weighted magnetic resonance imaging when targeted to fibrin clots in vitro. The particle also exhibits a defined clearance and safety profile in vivo.     

Controllable three-component luminescence from a 1,8-naphthalimide/Eu(III) complex: white light emission from a single molecule

A macrocycle-appended naphthalimide derivative and its Eu(III) complex show triple luminescence from isolated naphthalimide (blue), aggregated naphthalimide excimers (green) and Eu centres (red) with the balance being sensitive to the degree of aggregation, allowing white light emission to be obtained from a single molecule.     

Quantifying dithiothreitol displacement of functional ligands from gold nanoparticles

Dithiothreitol (DTT)-based displacement is widely utilized for separating ligands from their gold nanoparticle (AuNP) conjugates, a critical step for differentiating and quantifying surface-bound functional ligands and therefore the effective surface density of these species on nanoparticle-based therapeutics and other functional constructs. The underlying assumption is that DTT is smaller and much more reactive toward gold compared with most ligands of interest, and as a result will reactively displace the ligands from surface sites thereby enabling their quantification. In this study, we use complementary dimensional and spectroscopic methods to characterize the efficiency of DTT displacement. Thiolated methoxypolyethylene glycol (SH-PEG) and bovine serum albumin (BSA) were chosen as representative ligands. Results clearly show that (1) DTT does not completely displace bound SH-PEG or BSA from AuNPs, and (2) the displacement efficiency is dependent on the binding affinity between the ligands and the AuNP surface. Additionally, the displacement efficiency for conjugated SH-PEG is moderately dependent on the molecular mass (yielding efficiencies ranging from 60 to 80?% measured by ATR-FTIR and ≈90?% by ES-DMA), indicating that the displacement efficiency for SH-PEG is predominantly determined by the S–Au bond. BSA is particularly difficult to displace with DTT (i.e., the displacement efficiency is nearly zero) when it is in the so-called normal form. The displacement efficiency for BSA improves to 80?% when it undergoes a conformational change to the expanded form through a process of pH change or treatment with a surfactant. An analysis of the three-component system (SH-PEG?+?BSA?+?AuNP) indicates that the presence of SH-PEG decreases the displacement efficiency for BSA, whereas the displacement efficiency for SH-PEG is less impacted by the presence of BSA.

Solid state 13C NMR can distinguish between bronsted and Lewis acid adducts of amines

The solid ¹³C NMR spectra of solid complexes of phenethylamine with SnCl_4, Me₃SnCl, AlCl_3, and HCl are presented and discussed as a means of distinguishing between Bronsted and Lewis acid adducts of alkyl amines. Solution ¹³C NMR results are discussed in terms of species present in complex equilibria and their detection using the two NMR methods.