Our research interests are primarily in bioanalytical chemistry, with a focus on NMR spectroscopy and its applications to the characterization of peptides, proteins, carbohydrates and the chemistry of heavy metal toxicology.

Peptides and Proteins. We are studying the solution chemistry of peptides and proteins by state-of-the-art liquid phase 1H and 13C NMR spectroscopy, including their microscopic acid/base and thiol/disulfide chemistry and their secondary structure in solution. Our studies on thiol/disulfide chemistry include measurements by both NMR and HPLC to characterize the kinetics and equilibria of thiol/disulfide exchange reactions involving the thiol and disulfide groups of amino acids and peptides, including peptide hormones, peptide toxins and model peptides for the active site of thiol/disulfide oxidoreductases. We also are studying the kinetics and equilibria of cis/trans isomerization of peptide bonds by NMR.

Carbohydrates. A major research program in our laboratory involves the characterization of heparin, a glycosaminoglycan, and its interaction with peptides derived from the heparin-binding regions of cell adhesion proteins, including fibronectin, laminin, thrombospondin and vitronectin, and with designer peptides. The objectives of the binding studies are to characterize the heparin-peptide interactions at the molecular level, including identification of the binding sites on both heparin and the peptides and determination of the secondary structures of both the heparin and the peptides in the heparin-peptide complexes. The interactions are characterized at the molecular level by NMR and binding constants are determined by isothermal titration calorimetry (ITC)

Chemistry of Heavy Metal Toxicology. We are studying the complexation of heavy metal ions, including mercury, cadmium lead and zinc, by peptides, including a family of peptides, the phytochelatins, that are produced by plants to sequester heavy metals. The goals of this research are to identify peptide motifs that have a high affinity and high selectivity for specific heavy metal ions and to develop new molecules for use in the treatment of heavy metal poisoning.

In all of our research, we make extensive use of one- and two-dimensional NMR spectroscopy. We have two high field NMR spectrometers in our laboratory, in addition to the high field instruments in the departmental Analytical Chemistry Instrumentation Facility (ACIF). In addition to using NMR in the studies described above, we are developing new NMR methods which make use of the pulsed field gradient capabilities and the magic angle spinning capabilities of a state-of-the-art 500 MHz Varian UnityINOVA NMR spectrometer in our laboratory. Most of the peptides being studied are synthesized using a computer-controlled solid phase peptide synthesizer, purified by HPLC and characterized by capillary electrophoresis, mass spectroscopy and NMR. We have all of the instrumentation needed for the peptide synthesis and characterization in our laboratory.

Selected Publications

Spain, S.M.; Rabenstein, D.L. “Characterization of the Selenotrisulfide Formed by Reaction of Selenite with End-Capped Phytochelatin-2”, Anal.Bioanal. Chem., 2004, 378, 1414-1427.

Shi, T.; Spain, S.M.; Rabenstein, D.L. “Unexpectedly Fast Cis/Trans Isomerization of Xaa-Pro Peptide Bonds in Disulfide-Constrained Cyclic Peptides”, J. Amer. Chem. Soc. 2004, 126, 790-796.

Spain, S.M.; Rabenstein, D.L. “Characterization of the Acid/Base and Redox Chemistry of Phytochelatin Analogue Peptides”, Analytical Chemistry, 2003, 75, 3712-3719.

Rabenstein, D. L. "Heparin and Heparan Sulfate: Structure and Function," Natural Product Reports 2002, 19, 312-331.

Chuang, W-L.; McAllister, H.; Rabenstein, D. L. "Hexasaccharides from the Histamine-Modified Depolymerization of Porcine Intestinal Mucosal Heparin," Carbohydrate Research 2002, 337, 935-945.

Shi, T.; Rabenstein, D. L. "Convenient Synthesis of Human Calcitonin and Its Methionine Sulfoxide Derivative," Bioorganic & Medicinal Chemistry Letters 2002, 12, 2237-2240.

Chuang, W-L.; Christ, M. D.; Rabenstein, D. L. "Determination of the Chemical Structures of Heparin- and Heparan-Sulfate-Derived Oligosaccharides Using Band-Selective Homonuclear-Decoupled Two-Dimensional 1H NMR Experiments," Analytical Chemistry 2001, 73, 2310-2316.

Shi, T.; Rabenstein, D. L. "Formation of Multiple Intramolecular Disulfide Bonds in Peptides Using the Reagent trans-[Pt(ethylenediamine)2Cl2]2+" Tetrahedron Letters 2001, 42, 7203-7206.

Chuang, W-L.; McAllister, H.; Rabenstein, D. L. "Chromatographic Methods for Product Profile Analysis and Isolation of Oligosaccharides Produced by Heparinase-Catalyzed Depolymerization of Heparin," J. Chromatography A 2001, 932, 65-74.

Rabenstein, D. L. "NMR Spectroscopy: Past and Present," Analytical Chemistry 2001, 73, 214A-223A.

Rabenstein, D. L.; Shi, T.; Spain, S. “Intramolecular Catalysis of the Cis-Trans Isomerization of Proline Peptide Bonds in Cyclic Disulfide-Containing Peptides,” J. Amer. Chem. Soc. 2000, 122, 2401-2402.

Shi,T.; Rabenstein, D . L. “Discovery of a Highly Selective and Efficient Reagent for Formation of Intramolecular Disulfide Bonds in Peptides,” J. Amer. Chem. Soc. 2000, 122, 6809-6815.

Hari, S. P.; McAllister, H.; Chuang, W-L.; Christ, M. D.; Rabenstein, D. L. “Interaction of Heparin with a Synthetic Pentadecapeptide from the C-Terminal Heparin-Binding Domain of Fibronectin,” Biochemistry 2000, 39, 3763-3773.

Chuang, W-L.; Christ, M. D.; Peng, J.; Rabenstein, D. L. “An NMR and Molecular Modeling Study of the Site-Specific Binding of Histamine by Heparin, Chemically Modified Heparin, and Heparin-Derived Oligosaccharides”, Biochemistry, 2000, 39, 3542-3555.

Kaerner, A.; Rabenstein, D. L. “Stability and Structure-Forming Properties of the Two Disulfide Bonds of a-Conotoxin GI”, Biochemistry, 1999, 38, 5459-5470.

Kaerner, A.; Rabenstein, D. L. “An ?-Band-Selective, ?-Homonuclear Decoupled ROESY Experiment: Application to the Assignment of 1H NMR Spectra of Difficult-to-Assign Peptide Sequences”, Magn. Res. Chem. 1998, 36, 601-607.