James A HolcombeProfessor Emeritus
Department of Chemistryholcombe@mail.utexas.edu
The University of Texas at Austin
Department of Chemistry, College of Natural Sciences
105 East 24th Street
Austin, TX 78712
Ph.D., University of Michigan (1974)
B.A., Colorado College (1970)
Atomic Spectroscopy; Ultratrace Metal Analysis; And Biopolymer Metal Binding
Prof. Holcombe's group is involved in a variety of research areas focusing on trace metal analysis. The central theme is in the development of improved techniques (including new sources); speciation and preconcentration; and developing a better understanding of the processes preceding signal measurement.
Biomolecules and biopolymers for metal binding and detection
We are using short chain biomolecules for trace metal preconcentration using flow injection systems with small columns containing these molecules chemically immobilized on various surfaces, including nanoparticles of magnetic Fe2O3. It is the intent to take advantage of Mother Nature's concept of "metal binding proteins". We are using biopolymers to accomplish similar goals using theses more readily prepared materials. The advantages sought are selectivity and strong binding with the ability to denature (i.e., "unwrap") the molecule to easily release the metal -- on demand! We also are actively pursuing remote sensing using FRET response as a result of these peptide conformational changes when they complex with metal ions. We’re expecting spectroscopic responses from ppb levels of metals from a remote sensing “package” that can be put in your pocket.
ICP-MS (inductively coupled-mass spectrometry)
ICP-MS is probably the most powerful elemental analytical tool in the field today. With sub-ppb and sub-ppt sensitivities and multielement capabilities, it has gained wide acceptance in spite of its $170-250K price tag. However, many applications have only a limited sample amount (microanalysis). An electrothermal vaporizer (ETV... sometimes referred to as a graphite furnace) used as a sample introduction provides a solution. Understanding and improving ETV introductions is a research objective. We have also initiated a project to elucidate a cell’s metallome (metal containing peptide composition) using ETV and laser ablation. More than a third of all proteins are thought to have a metal associated with it. Loss of metal or displacement with another metal is often associated with an organism disease state. Step one in elucidating some of these health issues is to determine metal-protein associations.
Rowland, A., Housh, T.B., and Holcombe, J.A. "Use of Electrothermal Vaporization for Volatility-Based Separation of Rb-Sr Isobars for Determination of Isotopic Ratios by ICP-MS" J. Anal. Atom. Spectrom 23(2) (2008): 167-172.
White, B.R., Liljestrand, H.M., and Holcombe, J.A. "A 'Turn On' FRET Peptide Sensor Based on the Mercury Binding Protein MerP" Analyst 133(1) (2008): 65-70.
Finley-Jones, H.J., Molloy, J.L., and Holcombe, J.A. "Choosing Internal Standards Based on a Multivariate Analysis Approach with ICP(TOF)MS" J. Anal. Atom. Spectrom 23(9) (2008): 1214-1222.
Stair, J.L., White, B.R., Rowland, A., and Holcombe, J.A. "Quantitative determination of single-bead metal content from a peptide combinatorial library" Journal of Combinatorial Chemistry 8(6) (2006): 929-934.