Lawrence R. Drake

Applications of Frontal Affinity Chromatography to the Study of Interactions between Metal Ions and a Complex Biomaterial.

The use of frontal affinity chromatography for the study of metal-biomaterial interactions is described. Both normal frontal affinity chromatography and a modification of this methodology were used to generate metal binding isotherms to a biomaterial. This modification enabled the acquisition of binding isotherms with extended concentration ranges at the expense of time-dependent binding information. Comparison between normal and modified mode was made by using a well-defined commercial resin. Similar performance of these two modes was obtained. The biomaterial investigated was composed of cell fragments from the plant Datura innoxia which were immobilized within a polysilicate matrix. The application of a regularized least-squares method indicated the existence of two classes of sites on this biosorbent involved in the binding of Ag(+). A total metal-ion binding affinity order at solution pH 3-5 was determined to be Cu(2+) > Cd(2+) ≈ Ag(+) > Ca(2+).

Affinity distributions of lead ion binding to an immobilized biomaterial derived from cultured cells of Datura innoxia

Abstract Datura innoxia biomass has been targeted as a potential sorbent for heavy metal remediation. Of interest in our laboratory are the binding mechanisms responsible for metal uptake. In this study, the binding behavior of Pb(II) to immobilized Datura innoxia biomaterial was investigated under different chemical conditions, such as ionic strength, the presence of calcium, and pH. Regularized regression analysis was employed to derive the corresponding affinity distributions. Two classes of binding sites were determined, having mean affinity of approximately 200 and 105 M−1, depending on solution conditions. Variations in apparent affinity distributions with ionic strength and pH suggest the low-affinity sites involve sulfonates and carboxylates in an ion exchange process. The high-affinity sites are proposed to result from the coordination of carboxylates to Pb2+ ions.

Characterization of Metal Ion Binding Sites on Datura innoxia by Using Lanthanide Ion Probe Spectroscopy

The excitation spectra associated with the 7F0↦5D0 transition of Eu+3 has been used to examine the binding sites on cell wall fragments of Datura innoxia. Both native and esterified cell wall fragments were each examined at pH 5 and pH 2 to determine the contributions to metal ion sorption from both the carboxylate and sulfonate functional groups. The excitation spectra have been de-convoluted into the individual groups responsible for metal ion uptake. At least four unique binding sites can be described as being responsible for metal ion uptake. The higher affinity sites involve carboxylates in the binding of Eu+3 in a tridentate (3:1 ligand-to-metal ratio) configuration.

Characterization of analyte absorption profiles in a power-amplitude modulated inductively coupled argon plasma

Abstract Analyte absorption profiles were generated using a square wave power-amplitude modulated inductively coupled plasma (ICP). Atomic absorption was achieved by the coaxial orientation of the ICP torch along the optical axis of the spectrometer. Incident radiation, from a hollow cathode lamp, was passed through the sample introduction channel of the torch and through the central channel of the plasma. Modulation frequencies investigated were 10, 20, 30, 40, 50, 100 Hz. The magnitudes of the square wave power step were 50, 150, 250, 400, 500, 650, 850, 950 W from a steady state power level of 1500 W. Three absorbance maxima were observed between 2 and 15 ms after the decrease in the applied forward power. These maxima are suggested to be dependent on the analyte, changes in radial gas dynamics and changes in linear gas velocity. The calculated absorbance, from integrating over the 2–15 ms time period, was shown to return values comparable to those taken at the peak maxima but with improved precision and accuracy.

A laser based spectrofluorometer for the efficient probing of metal ion binding sites on solid biomaterials

Abstract A laser based spectrofluorometer with f/# matched optics has been developed for the investigation of metal ion binding sites on nonviable biomaterials. Solid biomaterial samples have been encapsulated in a KBr glass matrix for these investigations. This sample preparation technique has allowed for the investigation of metal ion binding sites by both luminescence and infrared spectroscopy. The utility of the system and the method of sample preparation has been demonstrated with Eu(III) bound to cultured cell fragments from Datura innoxia.