Biopolymer Metal Binding and ETV-ICPMS

1. High Throughput Screening of Combinatorial Libraries Exposure to mixed metal solution U + M Bind metal Cd Cu Library of Oligopeptides Metal-bound bead in acid solution Bead in metal solution Release metal 1mm U Synthesize polypeptide(s) and characterize uranium binding Metal solution to be quantified CGGDCCGDGC Determine what exclusively binds U Sequence peptide High throughput screening Amino Acid Cation Binding Residues CH CH2 CH H CH O SH C CH2 H2N C COOH M+ Cysteine O- C O M+ R Aspartate OH O- M+ Tyrosine Glutamate M+ Anion Binding Residues Other Chelating Residues M+ M+ M+ (CH2)3 CH2 (CH2)4 CH2 CH2 C O CH2 NH CH2 NH3+ NH2 C O Lysine HN C NH2+ N Asparagine Support NH2 Tryptophan NH NH2 Glutamine Histidine Arginine Second Vaporization Stage First Vaporization Stage Auxiliary Electrode Eapplied Column 3-electrode potentiostat Reference Electrode valve An electrical potential is used to change the binding characteristics of the column. Metal Recovery Stream Clean Effluent Stream High Throughput Screening Techniques Resonance energy transfer (RET) can be used to determine various characteristics of metal binding. RET involves the transfer of energy between a fluorescent donor and an acceptor molecule. The efficiency of the energy transfer is dependent on the distance between the molecules, which can be related to their spectroscopic properties. Mn+ Mn+ Free metal can be bound and released by exposing the ligand to successive reduction and oxidation cycles. Mn+ Micro-x-ray-fluorescence (MXRF) Fluorescence Microscopy ETV-ICPMS Mn+ Mn+ UO22+ in solution Absorption bands: 330-350nm, 390-440nm Emission bands: 470-570nm with lmax at 485nm, 510nm, 535nm, and 560nm Polycapillary optic/ x-ray source Electrothermal vaporization inductively-coupled plasma mass spectrometry Si Li detector Mn+ Mn+ Bell and Biggers. J. Molec. Spec., 1965, 18, 247-275 Sample Moulin, C. et al. Anal. Chem., 1995, 67, 348-353 Oxidation Reduction Counter Electrodes LED - stage illumination TackyDot™ slide to array beads Scale up of the electrochemical reactor to practical size requires consideration of materials, geometry, operating conditions, and overall cost. Flow • Single bead screening • Quantitative elemental information • Non-destructive • Bulk/single bead screening • Applicable for wide range of metals • Non-destructive • Bulk screening • Based on fluorescence of bound species • Non-destructive Working Electrodes Biopolymer Metal Binding and ETV-ICPMS The Bonded-Phase Ion-Exchange System ICP-MS is the cutting edge technology for atomic spectrometry. It can offer part per trillion detection limits, over 5 orders of magnitude of linear response, and works for almost all elements in the periodic table. It uses an inductively coupled plasma (~8,000 K) as the ionization source. Our ICP-MS uses a time of flight system for mass analysis. Though many labs rely on solution nebulization for sample introduction, this is not always the best technique. It can be problematic for some matrices (e.g. salty solutions, organic solutions, and solids or slurries). An alternative is electrothermal vaporization (ETV). This uses a carbon tube to vaporize the sample before introduction to the ICP-MS. Vaporization temperatures of up to 3,000o C can be achieved in a controlled manner. It can handle a wide variety of sample types, and generally has higher sample introduction efficiency than nebulizers. For the past several years, one of the primary focuses of our research group has been the development of novel ion-exchange systems for the purpose of metal remediation from aqueous systems. Expanding on hints from Mother Nature, we chose to explore the metal chelation abilities of proteins and, in particular, their constituent amino acids. In order to simplify these ion-exchange systems, short-chain homopolymers consisting of repeating monomers of a specified amino acid residue have been used. These systems exhibit many of the characteristics for an ideal ion-exchanger – strong binding; fast, efficient release and structural stability. These biologically-based systems also have the added benefit of being environmentally friendly, unlike many traditional exchange systems which require harsh extraction agents. Sample To ICP-MS Exploring a Combinatorial Approach Developing Fluorescence-based Sensors Creating Chemical-free Remediation Systems ETV-ICP-MS for Isobars and Isotopes High Throughput Sample Introduction One problem with ICP-MS is elements of the same nominal mass (isobaric interference). ETV can be used to separate some problematic elements based on their differing volatilities. Rb and Sr can be separated to remove the isobar at mass 87. Multi-ETV system for rapid sample introduction, with all of the benefits of a graphite furnace. Coupled with the ICP-TOF, the periodic table can be analyzed every 40 seconds. This is 5 times faster than current techniques! The time of flight design is able to offer excellent isotope ratio precision as a result of simultaneous ion extraction from the plasma. However, difficulties have been encountered with ratio accuracy. Factors that cause this and possible fixes are actively being researched. Questions? Email Thomas. tk109400@mail.utexas.edu Questions? Email Ram. ramk@mail.utexas.edu Questions? Email Carina. cgunder@mail.utexas.edu Questions? Email Brianna. briannawhite@mail.utexas.edu Questions? Email Adam. adamrowland@mail.utexas.edu Visit us! On the web: http://www.cm.utexas.edu/directory/james_holcombe/ In the Lab: Welch 3.240 and 3.238