Our laboratory is interested in the dynamic structure and function of proteins, nucleic acids, glyco-conjugates, and membranes. Motions and interactions that occur on time scales from picoseconds to minutes are investigated. Fluorescence spectroscopy provides a relatively non-invasive probe and has the power to examine functional macromolecular assemblies both in solution and in the intact cell. The current interest is in the dynamics of electrostatic interactions in proteins. We are approaching this problem with the aid of time-resolved fluorescence emission studies. Nanosecond time-resolved spectral shifts of both the intrinsic and/or extrinsic emission may be related to the time dependence of changes in the electric field around the fluorophore. Proteins being studied include the galactose repressor, interlukin II, staphylococcal. Nuclease and several proteins involved in the bacterial phosphoenol pyruvate glucose transfer system. The work with the PTS system is done in collaboration with Professor S. Roseman. - Wu, P., K.B. Lee, Y.C. Lee, and L. Brand. 1996. Solution conformations of a biantennary glycopeptide and a series of exoglycosidase products from sequential trimming of sugar residues. J. Biol. Chem. 271:1470-1474.
- Toptygin, D.D., B.Z. Packard, and L. Brand. 1997. Resolution of absorption spectra of rhodamine 6G aggregates in aqueous solution using the law of mass action. Chem. Phys. Lett. 277:430-435.
- Packard, B.Z., A. Komoriya, D.D. Toptygin, and L. Brand. 1997. Structural characteristics of fluorophores that form intramolecular H-type dimers in a protease substrate. J. Phys. Chem. 101:5070-5074.
- Wang, K., M.E. Rodgers, D. Toptygin, V.A. Munsen, and L. Brand. 1997. Fluorescence study of the multiple binding equilibria of the galactose repressor. Biochemistry 37:41-50.
- Packard, B.Z., D.D. Toptygin, A. Komoriya, and L. Brand. 1997. Characterization of fluorescence quenching in bifluorophoric protease substrates. Biophys. Chem. 67:167-176.
- Hirshfield, K.M., D. Toptygin, G. Grandhige, B.Z. Packard, and L. Brand. 1998. A nanosecond fluorescence study of the simultaneous influx of Ca2+ and Cd2+ into liposomes. Biophys. Chem. 71:63-72.
- Packard, B.Z., A. Komoriya, V. Nanda, and L. Brand. 1998. Intramolecular excitonic dimers in protease substrates: Modification of the backbone moiety to probe the H dimer structure. J. Phys. Chem. B 102:1820-1827.
- Packard, B.Z., D.D. Toptygin, A. Komoriya, and L. Brand. 1998. Intramolecular resonance dipole-dipole interactions in a profluorescent protease substrate. J. Phys. Chem. B 102:752-758.
- Brown, M.P., D. Toptygin, K.B. Lee, T. Animashaun, R.C. Hughes, Y.C. Lee, and L. Brand. 1998. The tryptophan fluorescence of tetracarbidium conophorum agglutinin II and a solution based assay for the binding of a biantennary glycopeptide. J. Protein Chem. 17:149-159.
- Fomenkov, A., A. Valiakhmetov, L. Brand, and S. Roseman. 1998. In vivo and in vitro complementation of the N-domain of enzyme I of the Escherichia coli phosphotransferase system by the cloned C-terminal domain. Proc. Natl. Acad. Sci. USA 95:8491-8495.
- Nanda, V., and L. Brand. 2000. Aromatic Interactions in Homeodomains Contribute to the Low Quantum Yield of a Conserved, Buried Tryptophan. Proteins: Struct. Funct. Genet. 40:1121-125.
- Toptygin, D., and L Brand. 2000. Spectrally and Time-Resolved Fluorescence Emission of Indole During Solvent Relaxation: A Quantitative Model. Chem. Phys. Lett. 322:496-502.
- Reshetnyak, Y.K., O.A. Andreev, J. Borejdo, D.D. Toptygin, L. Brand, and E.A. Burstein 2000. The Identification of Tryptophan Residues Responsible for ATP-induced Increase in Intrinsic Fluorescence of Myosin Subfragment 1. J Biomol Struct. Dyn. 18:113-125.
- Nanda, V., Liang, Shu-Mei, and L Brand. 2000 Hydrophobic Clustering in Acid-Denatured IL-2 and Fluorescence of a Trp NH...pi H-bond. Biochem. Biophys. Res. Commun. 279:770-778.
- Toptygin, D. R.S. Savichenko, N.D. Meadow, and L. Brand, 2001. Homogeneous Spectrally and Time-Resolved Fluorescence Emission from Single-Tryptophan of IIA Glc Protein. J. Phys. Chem. B 105:2043-2055.
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