Professor
B.S. 1962, CUNY (City University of New York)
Ph.D. 1970, Rutgers University
Postdoc 1971-2, University of California-Irvine
Postdoc 1970-1, University of Massachusetts Amherst

Bioanalytical, Biophysical Chemistry

Department of Chemistry
149F GSMN
University of Massachusetts
710 North Pleasant Street
Amherst, MA 01003

office: 149F GSMN
lab: GSMN 144, 242
tel: 413-577-4167; fax: 413-545-4490

dubin@chem.umass.edu

Dubin Research Group

Research in my group arises from my interest in polyelectrolytes, long-chain molecules in
which every repeat unit carries a charge. Their unique properties reflect a combination of those of polymer solutions and salts. We focus on their interaction with oppositely charged nanoparticles such as dendrimers, surfactant micelles and proteins, with the objective of fundamental understanding of solution behavior. To do this we measure properties that can be quantitatively understood through basic physical relationships. Our work combines the disciplines of analytical, biological and physical chemistry.

Our experimental tools vary from very simple ones (turbidimetry), to more complex methods (light scattering, capillary electrophoresis, rheology, and various microscopies). To ensure reproducible results, we focus on equilibrium systems. One of our interests is the unique dense, viscous liquid phase “coacervates” that form spontaneously from polyelectrolytes with oppositely charged micelles or proteins. Polyelectrolyte-enzyme coacervates function as microreactors because the protein retains its native state and diffuses freely in the dense fluid coacervatge droplets. The surprising combination of high viscosity and fast diffusion arises from mesophase separation at the 300 nm length scale in these fluids. Polyelectrolyte-micelle coacervates also display unusual properties, phase separating by either heating or stress, a phenomenon known as “shear-banding.”

Biologically significant protein binding occurs with a group of polyelectrolytes known as glycosaminoglycans (GAGs). These mammalian polysaccharides are the most highly charged macromolecules in animals. Although they play a role in the action of many signaling proteins responsible for tissue regeneration, angiogenesis and cell differentiation, structure-property relations for GAGs are unknown. Unlike proteins and nucleic acids, they are never homogeneous and therefore never “pure,” so their characterization presents a huge challenge to classical biochemistry. We approach this problem with the model GAG-protein system of heparin-antithrombin, applying electrophoretic methods coupled with mass spectrometry and protein modeling.

Representative Publications

2008

1. Y. Li, P.L. Dubin and W. Jaeger, “Mesophase Separation in Polyelectrolyte-Mixed Micelles Coacervates,” Langmuir, in press (2008).
2. A. Menjoge, A.B. Kayitmazer, S.A. Vasenkov and P.L. Dubin, “1H PFG NMR Studies of BSA/PDADMAC Coacervates,” J. Phys. Chem., under revision (2008).

2007

1. Y.G. Mishael, P.D. Dubin, R. deVries and A.B. Kayitmazer,“Effect of Pore Size on Polyelectrolyte Adsorption on/in Controlled Pore Glass”,  Langmuir. 23 2510-2516 (2007).
2. E. Seyrek, J. Henriksen and P.L Dubin, “Nonspecific Electrostatic Binding Characteristics of the Heparin-Antihrombin Interaction”,  Biopolymers 86, 249-259 (2007).
3. A. Kumar, M. Herndon, W. Jaeger and P.L. Dubin,“Temperature-dependent Phase Behavior of Polyelectrolyte-mixed Micelle Systems”,  J. Phys. Chem. B.,  ASAP.
4. A.B. Kayitmazer, H. Bohidar, A. Bose, A. Hashidzume, P.Russo, W. Jaeger and P.L. Dubin, “Mesophase Separation and Probe Dynamics in Protein-polyelectrolyte Coacervates”, Soft Matter, published on the web, June 26, 2007 http://www.rsc.org/Publishing/Journals/SM/article.asp?doi=b701334e
5. R. Abzalimov, P.L.Dubin and I. Kaltashov,“Glycosaminoglycans as naturally occurring combinatorial libraries: developing a   mass spectrometry-based strategy for characterization of anti-thrombin interaction with low molecular weight heparin and heparin oligomers”, Anal. Chem. , (2007) accepted.
6. Effect of Polyelectrolyte Structure on Protein-Polyelectrolyte Coacervates: Coacervates of Bovine Serum Albumin with Poly(dimethyldiallylammonium chloride) vs. Chitosan A.B. Kayitmazer, S.Strand, C. Tribet, W. Jaeger, P.L. Dubin, Biomacromolecules, under revision, (2007).

1. P. Mahji, R. R. Ganta, R. P. Vanam, E. Seyrek and K. Giger,“Electrostatically-induced protein aggregation: b-Lactoglobulin at low ionic strength”, Langmuir 22, 9150-9159 (2006).
2. X. Guo, G.F. Kirton and P.L. Dubin, “Carboxylated Ficolls: Synthesis, Characterization and Electrophoretic Behavior of Model Charged Nanospheres”, J. Phys. Chem., B, 110, 20815-20822 (2006).
3. C.L. Cooper, A. Goulding, A.B. Kayitmazer, S. Stoll, S. Turksen, S. Ulrich, S.-I. Yusa, A. Kumar and P.L. Dubin,"Effects of Polyelectrolyte Chain Stiffness, Charge Mobility and Charge Sequences on Binding to Proteins and Micelles", Biomacromolecules, 7(4), 1025-1035 (2006).

Click here for a complete list of publications.