Comparison of Curve Fitting Models for Ligand Binding Assays

In the case of ligand binding assays the relationship between instrumental response and analyte concentration is non-linear, usually either hyperbolic or sigmoidal. As it is not possible to calibrate an assay at all the levels to be measured a suitable method of constructing a concentration-response relationship (the standard curve), based on a limited number of carefully spaced standards is required. The method should be robust and operator independent. The two main approaches that have been used involve empirical and mechanistic (theoretical) models. Empirical models utilise any mathematical function(s) that appears to have the characteristics of the experimentally derived assay data. Empirical models require no understanding of the principles of the assay. Mechanistic models make assumptions about the physico-chemical processes involved in the assay procedure. In practice either single function or spline models are used. The curve fitting solution may be explicit (in the case of spline interpolation), or by least-squares curve fitting regression methods, including polynomial and logistic equations, the latter involving many iterations. Examples of good curve fitting selection are presented and contrasted with inappropriate models in a number of common assay formats.     

Structural and magnetic properties of nano-crystalline RuFe alloys prepared by organometallic synthesis

Nanoparticles of Ru_1-xFe_x (0≤x≤1) in a carbon matrix were synthesized over the entire composition range using organometallic precursors. For Fe concentrations with x<0.70, a hexagonal close-packed phase was formed whereas a body-centered cubic phase was observed for x>0.70. The crystallite sizes varied between 5–10 nm. In addition, multi-wall carbon nanotubes formed during the pyrolysis of the precursors. Increasing superparamagnetic order was observed with increasing Fe content.     

Planar integrated wavelength-drop device based on pedestal antiresonant reflecting waveguides and high-Q silica microspheres

Whispering-gallery modes in silica microspheres can be accessed very efficiently with the recently introduced stripline pedestal antiresonant reflecting optical waveguide (SPARROW) structure. This integrated-optics coupling technique creates novel application opportunities for the high-Q spherical cavities. We report the demonstration of a narrow-band wavelength-drop configuration utilizing SPARROW waveguides and a silica microsphere.     

Determination of tricyclic antidepressants using silica gel with a reversed-phase eluent

Summary Five common tricyclic antidepressants are separated on a silica column using an aqueous eluent. The tricyclics are concentrated from serum using an adsorption procedure on a solid phase Sep Pak^TM C₁₈ cartridge. The method appears to be adequate for monitoring therapeutic levels of these drugs.Dedicated to Professor Dr. István Halász for his 60th birthday.     

The preparation and tin-119 Mössbauer spectra of new adducts of the type organotetrachlorostannate(IV) base (11)

New adducts Et₄N(RSnCl₄ · L) (R butyl and phenyl; L pyridine, trimethylamine, tri-n-butylphosphine, triphenylphosphine oxide, triphenylarsine oxide, dimethylsulphoxide, dimethylformamide) have been isolated and their Mössbauer spectra studied. Definite structural assignments are made for the phosphine and phosphine oxide adducts from Mössbauer quadrupole splitting data. Comments are made on the choice of partial splitting values for phenyl and butyl groups.