Membrane proteins act as enzymes, regulate transport processes, and play a central role in intercellular communication. In order to understand the diverse functions of membrane proteins and to engineer these functions for biomedical or biotechnological purposes, it is necessary to determine their high-resolution structure and to describe their dynamics. Structure determination of membrane proteins is one of the most important and challenging aspects of science at the present time. Solid-state NMR spectroscopy is an ideal technique for immobile and non-crystalline proteins that are difficult to study by X-ray crystallography or by solution NMR.
The development of solid-state NMR methods and their applications to determine the structure and describe the dynamics of membrane proteins are the main goals of the research program. Biology of the research program involves the preparation of peptides and proteins associated with membranes through synthetic or molecular biological methods. All aspects of sample preparation are optimized including the incorporation of specific and selective isotopic labels, isolation, purification, and final preparation of NMR samples. Antimicrobial peptides, toxins, cytochrome b5, myelin basic protein, and amyloid peptides are some of the systems currently under investigation by this group. Solid-state NMR experiments on membrane proteins incorporated in oriented and unoriented phospholipid bilayers and solution NMR experiments on membrane proteins in detergent micelles or lipid bicelles are performed to determine the structure of membrane proteins.
Solid-state NMR spectroscopy is one of the premier methods for studying the structure and dynamics of molecules in solids. Ramamoorthy's research program orchestrates the theoretical design, experimental demonstration, and application of new and cutting edge solid-state NMR spectroscopic methods to study the structure and properties of molecules in single crystalline, liquid crystalline, polycrystalline, and amorphous phases. The design of solid-state NMR methods is composed of a variety of sophisticated techniques including specifically constructed multiple radio-frequency pulses, magic-angle spinning, multiple resonance schemes, sensitivity enhancement procedures, selective observation or hybridization of them. This basic research on spin physics encompasses theoretical and experimental aspects of spin engineering, computer simulations, and instrumentation.
Brender JR, Hartman K, Nanga RPR, Popovych N, de la Salud Bea R, Vivekanandan S, Marsh ENG, Ramamoorthy A. Role of Zinc in Human Amyloid Polypeptide Aggregation. J. Am. Chem. Soc. 132 (2010) 8973-8983.
Xu J, Soong R, Im SC, Waskell L, Ramamoorthy A. INEPT-Based Separated-Local-Field NMR Spectroscopy: A Unique Approach To Elucidate Side-Chain Dynamics of Membrane-Associated Proteins, J. Am. Chem. Soc. 132 (2010) 9944-9947.
Smith PES, Brender JR, Durr UHN, Xu J, Mullen DG, Banaszack Holl MM, Ramamoorthy A. Solid-State NMR Reveals the Hydrophobic-Core Location of Poly(amidoamine) Dendrimers in Biomembranes. J. Am. Chem. Soc. 132 (2010) 8087-8097.
Yamamoto K, Xu J, Kawulka KE, Vederas JC, Ramamoorthy A. Use of a copper-chelated lipid speeds up NMR measurements from membrane proteins. J. Am. Chem. Soc. 132 (2010) 6929-6931.
Soong R, Smith PE, Xu J, Yamamoto K, Im SC, Waskell L, Ramamoorthy A. Proton-evolved local-field solid-state NMR studies of cytochrome b5 embedded in bicelles, revealing both structural and dynamical information. J. Am. Chem. Soc. 132 (2010) 5779-5788.
S. Thennarasu, A. Tan, R. Penumatchu, C. E. Shelburne, D. L. Heyl, and A. Ramamoorthy, Antimicrobial and Membrane Disrupting Activities of a Peptide Derived from the Human Cathelicidin Antimicrobial Peptide LL37, Biophys. J. 98, 248-257 (2010).
A. Bhunia, P. N. Domadia, K. J. Hallock, A. Ramamoorthy, and S. Bhattacharjya, NMR Structure of Pardaxin, a Pore-Forming Antimicrobial Peptide, in Lipopolysaccharide Micelles: Mechanism of Outer membrane Permeabilization, J. Biol. Chem., 285, 3883-3895 (2010).
R. P. R. Nanga, J. R. Brender, S. Vivekanandan, N. Popovych, and A. Ramamoorthy, NMR Structure in a Membrane Environment Reveals Putative Amyloidogenic Regions of the SEVI Precursor Peptide PAP248-286, J. Am. Chem. Soc., 131, 17972-17979 (2009).
P. Z. Zhu, J. D. Xu, N. Sahar, M. D. Morris, D. H. Kohn, and A. Ramamoorthy, Time-Resolved Dehydration-induced Structural Changes in an Intact Bovine Cortical Bone Revealed by Solid-State NMR Spectroscopy, J. Am. Chem. Soc., 131, 17064-5 (2009).
S. S. Hindo, A. M. Mancino, J. J. Braymer, Y. H. Liu, S. Vivekanandan, A. Ramamoorthy, and M. H. Lim, Small Molecule Modulators of Copper-Induced Abeta Aggregation, J. Am. Chem. Soc., 131, 16663-5 (2009).
R. P. R. Nanga, J. R. Brender, J. D. Xu, K. Hartman, S. Vivekanandan, and A. Ramamoorthy, Three-Dimensional Structure and Orientation of Rat Islet Amyloid Polypeptide Protein in a Membrane Environment by Solution NMR Spectroscopy, J. Am. Chem. Soc., 131, 8252-8261 (2009).
R. Soong, J. R. Brender, P. M. Macdonald, and A. Ramamoorthy, Association of Highly Compact Type II Diabetes Related Islet Amyloid Polypeptide Intermediate Species at Physiological Temperature Revealed by Diffusion NMR Spectroscopy, J. Am. Chem. Soc., 131, 7079-7085 (2009).
P. E. S. Smith, J. R. Brender, and A. Ramamoorthy, Induction of Negative Curvature as a Mechanism of Cell Toxicity by Amyloidogenic Peptides: The Case of Islet Amyloid Polypeptide, J. Am. Chem. Soc., 131, 4470-4478 (2009).
J. Barry, M. Fritz, J. R. Brender, P. E. S. Smith, D. K. Lee, and A. Ramamoorthy, Determining the Effects of Lipophilic Drugs on Membrane Structure by Solid-State NMR Spectroscopy: The Case of the Antioxidant Curcumin, J. Am. Chem. Soc., 131, 4490-4498 (2009).
J. R. Brender, K. Hartman, L. M. Gottler, M. E. Cavitt, D. W. Youngstrom, and A. Ramamoorthy, Helical Conformation of the SEVI Precursor Peptide PAP(248-286), a Dramatic Enhancer of HIV Infectivity, Promotes Lipid Aggregation and Fusion, Biophys. J., 97, 2474-2483 (2009).
T. Fukami, T. Ishii, T. Io, N. Suzuki, T. Suzuki, K. Yamamoto, J. D. Xu, A. Ramamoorthy, and K. Tomono, Nanoparticle Processing in the Solid State Dramatically Increases the Cell Membrane Permeation of a Cholesterol-Lowering Drug, Probucol, Mol. Pharm., 6, 1029-1035 (2009).