Robert M. Bieganski, Ph.D.
Web Site Administrator
Web site designed, updated and maintained by Robert Bieganski
Selected Publications:
Interactions Among alpha-Synuclein, Dopamine, and Biomembranes: Some Clues
for Understanding Neurodegeneration in Parkinson's Disease. Rochet J.C., Outeiro T.F., Conway K.A., Ding T.T.,
Volles M.J., Lashuel H.A., Bieganski R.M., Lindquist S.L., and Lansbury P.T. J Mol
Neurosci. 2004; 23(1-2):23-34. Link to
PubMed
Abstract.
Kinetic Stabilization of the alpha-Synuclein Protofibril by a Dopamine-alpha-Synuclein Adduct. Conway KA, Rochet JC, Bieganski RM, Lansbury Jr PT. Science 2001 Nov 9;294(5545):1346-9.
Link to:
Science Full TextAbstract:
The substantia nigra in Parkinson's disease (PD) is depleted of dopaminergic neurons and contains fibrillar Lewy bodies comprising primarily alpha-synuclein. We screened a library to identify drug-like molecules to probe the relation between neurodegeneration and alpha-synuclein fibrilization. All but one of 15 fibril inhibitors were catecholamines related to dopamine. The inhibitory activity of dopamine depended on its oxidative ligation to alpha-synuclein and was selective for the protofibril-to-fibril conversion, causing accumulation of the alpha-synuclein protofibril. Adduct formation provides an explanation for the dopaminergic selectivity of alpha-synuclein-associated neurotoxicity in PD and has implications for current and future PD therapeutic and diagnostic strategies.
Intracellular trehalose improves the survival of cryopreserved mammalian cells. Eroglu A, Russo MJ, Bieganski R, Fowler A, Cheley S, Bayley H, Toner M. Nat Biotechnol 2000 Feb;18(2):163-7.
Link to:
PubMedAbstract:
We report that the introduction of low concentrations of intracellular trehalose can greatly improve the survival of mammalian cells during cryopreservation. Using a genetically engineered mutant of Staphylococcus aureus alpha-hemolysin to create pores in the cellular membrane, we were able to load trehalose into cells. Low concentrations (0.2 M) of trehalose permitted long-term post-thaw survival of more than 80% of 3T3 fibroblasts and 70% of human keratinocytes. These results indicate that simplified and widely applicable freezing protocols may be possible using sugars as intracellular cryoprotective additives.
Stabilization of active recombinant retroviruses in an amorphous dry state with trehalose. Bieganski RM, Fowler A, Morgan JR, Toner M. Biotechnol Prog 1998 Jul-Aug;14(4):615-20.
Link to:
PubMedAbstract:
The disaccharide trehalose is found to be effective for stabilization of active recombinant retroviruses in an amorphous dry state achieved through ambient-temperature vacuum dehydration of retroviral supernatants. Studies revealed that trehalose is a significantly better desiccation protectant than sucrose, glucose, and dextran: dextran has essentially no protective effect on retroviral survival after drying and rehydration. X-ray diffractometry of the retroviral supernatant dried with trehalose demonstrated its amorphous nature. The ability to dehydrate retroviral stocks at ambient temperatures into a stable glassy state will have a profound effect for researchers and commercial biotechnology companies which supply retroviral vectors for human gene therapy and basic research.
Primary structure of peptides and ion channels. Role of amino acid side chains in voltage gating of melittin channels. Tosteson MT, Alvarez O, Hubbell W, Bieganski RM, Attenbach C, Caporales LH, Levy JJ, Nutt RF, Rosenblatt M, and Tosteson DC. Biophys J. 1990 Dec;58(6):1367-75.
Link to:
PubMedAbstract:
Melittin produces a voltage-dependent increase in the conductance of planar lipid bilayers. The conductance increases when the side of the membrane to which melittin has been added (cis-side) is made positive. This paper reports observations on the effect of modifying two positively charged amino acid residues within the NH2-terminal region of the molecule: lysine at position 7 (K7), and the NH2-terminal glycine (G1). We have synthesized melittin analogues in which K7 is replaced by asparagine (K7-N), G1 is blocked by a formyl group (G1-f), and in which both modifications of the parent compound were introduced (G1-f, K7-N). The time required to reach peak conductance during a constant voltage pulse was shorter in membranes exposed to the analogues than in membranes modified by melittin. The apparent number of monomers producing a conducting unit for [K7-N]-melittin and [G1-f]-melittin, eight, was found to be greater than the one for [G1-f], K7-N]-melittin and for melittin itself, four. The apparent gating charge per monomer was less for the analogues, 0.5-0.3 than for melittin, one. Essentially similar results were obtained with melittin analogues in which the charge on K7 or G1 or both was blocked by an uncharged N-linked spin label. These results show that the positive charges in the NH2-terminal region of melittin play a major but not exclusive role in the voltage gating of melittin channels in bilayers.