Associate Professor of Chemistry
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Research Interests: Biophysical Chemistry.
My research interests focus on ligand-receptor interactions on cell surfaces that lead to signal transduction. I am particularly interested in systems where a requirement for cell activation is the clustering of the cell surface receptor by a ligand capable of bridging two or more receptor molecules. The best studied examples of receptor aggregation occur in immunology. My group employs a model system for studying allergic responses. On the surface of mast cells and basophils are receptors which bind immunoglobulin E with high affinity. Crosslinking of IgE initiates a biochemical cascade that results in the release of histamine and other mediators of allergic reactions. The clinical manifestations of this response include asthma, hay fever and hives.
1) R. Posner, K. Subramanian, T. Feder, J. Thomas, D. Holowka, B. Baird
and B. Goldstein. Simultaneous crosslinking by two non triggering bivalent
ligands causes synergistic signaling of IgE-FceRI complexes. Journal of
Immunology 155: 3601-3609 (1995).
2) J. Martin, R. Posner, R. Habbersett and L. Sklar, A rapid mix flow
cytometer with subsecond kinetic resolution. Cytometry 21: 223-229 (1995).
3) R. Posner, C. Wofsy and B. Goldstein, The Kinetics of Bivalent Ligand-Bivalent
Receptor Aggregation: Ring Formation and the Breakdown of the Equivalent
Site Approximation. Mathematical Biosciences 126: 171-190 (1995).
4) J. Nolan, S. Magargee, R. Posner and R. Hammerstedt. Flow cytometric
analysis of transmembrane phospholipid movement in bull sperm. (Biochemistry
34: 3907-3915 (1995).
5) R. Posner and M. Dembo. Binding of Bivalent Ligand to Cell Surface
IgE: Can one detect ring formation? Molecular Immunology 31: 1439-1445
(1994).
6) A. Remmers, R. G. Posner and R. Neubig. Fluorescent Guanine Nucleotide
Analogs and G Protein Activation. J. Biol. Chem., Vol. 269 No. 19: 13771-13778
(1994).
7) R. G. Posner, S. Fay, M. Domolewski and L. Sklar, Continuous Spectrofluorometric
analysis of formyl peptide receptor ternary complex interactions, Mol.
Pharm., 45: 65-73 (1994).
8) S. Fay, R. Habbersett, M. Domalewski, R. G. Posner, T. Houghton,
E. Pierson, J Whitacker, N.Muthukumaraswamy, R. Haugland, R. Freer and
L Sklar. Multiparameter flow cytometric analysis of a pH sensitive formyl
peptide: application to receptor structure and processing events. Cytometry,
15: 148-153 (1994).
9) R. G. Posner, B. Lee, D. Conrad, D. Holowka, B. Baird, and B.Goldstein, Aggregation of IgE receptor complexes on rat basophilic leukemia cells does not change the intrinsic affinity but can alter the kinetics of the ligand-IgE interaction, Biochemistry, 31: 5350-5356 (1992).
10) S. Fay, R.G. Posner, and L. Sklar, Real-Time Analysis of the assembly
of ligand, receptor and G-Protein by quantitative fluorescence flow cytometry,
Biochemistry, 30: 5066-5075 (1991).
11) J. Erickson, R. G. Posner, B. Goldstein, D. Holowka, and B. Baird,
Bivalent ligand dissociation kinetics from receptor bound IgE: Evidence
for a time dependent increase in ligand rebinding at the cell surface Biochemistry,
30: 2357-2363 (1991).
12) R. G. Posner, J. Erickson, D. Holowka, B. Baird, and B. Goldstein
, Dissociation Kinetics of bivalent hapten-Immunoglobulin E aggregates
in solution, Biochemistry, 30: 2348-2356 (1991).
13) J. Erickson, R. G. Posner, B. Goldstein, D. Holowka, and B. Baird,
Analysis of ligand binding and crosslinking of receptors in solution and
on cell surfaces: Immunoglobulin E as a model receptor, in: Fluorescence
in Biochemistry and Cell Biology, (1991) G. Dewey, ed. Plenum
14) B. Goldstein, R. G. Posner, D.C. Torney, J. Erickson, D. Holowka,
and B. Baird, Competition between solution and cell surface receptors for
ligand: The dissociation of hapten bound presence of surface antibody in
the presence of solution antibody, Biophysical Journal, 56: 955-966 (1989).
15) R.G. Posner and J. Dix, Temperature dependence of anion transport
inhibitor binding to human red cell membranes, Biophys. Chem., 23: 139-145
(1985).