Ludwig Brand Professor Department of Biology CMDB Graduate Program Faculty A.B. Harvard University Ph.D. Indiana University Postdoctoral Brandeis University Weizmann Institute

[Research Interests] [Representative Publications] [Lab Members]

RESEARCH INTERESTS

Conformation and Activity of Biological Macromolecules with Emphasis on Applications of Fluorescence Techniques

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. Our main 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 intrinsic and/or extrinsic emission may be related to the time dependence of changes in the electric field around the fluorophore. We have investigated a number of proteins with only a single tryptophan and are able to interpret the nanosecond time-resolved measurements in terms of a relaxation of the protein matrix. The relaxation dynamics are faster for small for a small protein with a tightly packed core and slower for some larger proteins. We are interested in studying the relaxation dynamics of numerous proteins. Fluorescence spectroscopy is one of the few techniques capable of directly measuring nanosecond relaxation processes of protein segments. The dynamics of collective motions and conformational changes in proteins are almost certainly related to protein structure and function. Understanding this relation in different proteins is a main interest in the laboratory. Proteins being studied include, GB1, the B1 immunoglobulin-binding domain of Streptococcal protein G, IIAGlc of the PTS system (in collaboration with the Roseman laboratory, HIV protease (in collaboration with the Freire laboratory), Drosophila notch receptor (in collaboration with the Barrick laboratory, and Staphylococcal nuclease (in collaboration with the Garcia-Moreno E. laboratory. We are also in collaboration with the Bessman laboratory to investigate the dynamics of Orf191, a Nudix hydrolase, in relation to its ability to hydrolyze GDP-mannose.

REPRESENTATIVE PUBLICATIONS

Toptygin, Dmitri; Gronenborn, A.M.; and Brand, L. 2006. “Nanosecond Relaxation Dynamics of Protein GB1 Identified by the Time-Dependent Red shift in the fluorescence of Tryptophan and 5-fluorotryptophan”. Journal of Physical Chemistry B. 110:26292-26302.

Xu,J., Toptygin, D., Graver, K.J.Albertini, R.A., Savchenko, R.S., Meadow, N.D, Roseman, S., Callis, P.R., Brand, L., and Knutson, J.R. 2006. Ultrafast fluorescence Dynamics of Tryptophan in the Proteins Monellin and IIAGlc. , J. Am. Chem. Soc. 128:1214-1221 2006.

Zheng, Y., F. Mamdani, D. Toptygin, L. Brand, J.T. Stivers, and P.A. Cole. 2005. Fluorescence analysis of a dynamic loop in the PCAF/GCN5 histone acetyltransferase. Biochemistry 44:10501-10509.

Toptygin, D., R.S. Savichenko, N.D. Meadow, and L. Brand. 2001. Homogeneous spectrally and time-resolved fluorescence emission from single-tryptophan of IIAGlc protein. J. Phys. Chem. B. 105:2043-2055.

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.

Lab Members

Research Associates:
Dimitrij Toptygin