5 Davey Lab
Penn State UniversityContacts:
Paul S. Weiss: stm@psu.edu
Anne Counterman: aec@stm1.chem.psu.edu
Julia Heetderks: jjh272@psu.edu
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The first of two Nikon inverted optical microscopes in the lab, this instrument is dedicated to study morphology and properties of lipid bilayer vesicles. It is used for fluorescence and phase contrast (DIC) methods of imaging. We are especially interested in the self-organization of lipids into single-component domains in multi-component vesicles. Generally our lipid components include one with a melting point below room temperature, and one with melting point above room temperature, so there will be both fluid and gel domains present in the same vesicle. The different domains are labeled with co-localized fluorescent dyes. A wavelength splitter is used to separate the signals and record images from both dyes simultaneously. These are later recombined into a single, dual-color image, showing the lipid domain pattern as seen in images below.
This microscope also has dual micropipette capabilities. Liquid pressure inside the micropipettes is controlled by a homebuilt manometer system, and measured with a reluctance transducer. The micropipettes are used for vesicle manipulation, tether pulling, membrane stretching, and aspiration force experiments. All these methods change the local degree of curvature of the membrane, and can manipulate the membrane into modeling local conditions in biological systems, on a larger (optically visible) scale.
References:
D'Onofrio TG,
Binns CW, Muth EH, Keating CD, Weiss PS. 2002. Controlling and measuring local
composition and properties in lipid bilayer membranes. Journal of Biological
Physics 28(4):605-617.
D'Onofrio TG, Hatzor A, Counterman AE, Heetderks JJ, Sandel MJ, Weiss PS. 2003.
Controlling and Measuring the Interdependence of Local Properties in
Biomembranes.
Langmuir,
in press.
Images: Lipid domains on vesicle surface; partially aspirated vesicle; vesicle main body at center of lipid tether (also with "beading")
(green shows fluidic lipid components, red shows gel-phase lipid components,
yellow shows mixture)