A simple, chemical materials model may lead to a better understanding of the structure and organization of the cell according to a Penn State researcher.
"Cells are interesting because they show organization even at the level of the cytoplasm, and while it is thought to be important for cell functions, it is not always clear how this organization is achieved," said Christine Keating, associate professor of chemistry. "We are taking a materials chemistry approach in developing simple experimental models for cytoplasm organization," she told attendees at the 2009 Annual Meeting of the American Association for the Advancement of Science.
Cytoplasm is the material that fills the cell and is crowded with very large molecules. It surrounds the organelles -- tiny organs like mitochondria and the nucleus. Unlike organelles, the cytoplasm is a fundamental feature of all cells. Many important biochemical processes take place here, and so cytoplasm is interesting as a major player in cell function.
Creating a cell with organelles would be a monumental task, but creating one that exhibits molecular crowding and heterogeneity -- unevenness of composition -- is possible using large polymeric molecules and a lipid membrane.
Keating uses lipids to create vesicles, tiny cell-sized bubbles of lipid membrane in an aqueous solution of two large polymers. In one case she used poly(ethyleneglycol) (PEG) -- a common polymer -- and dextran -- a polymerized sugar to create the cell.
"Neither of these compounds is important in a cell, but they illustrate the possibility of partitioning large molecules within a cell without internal membranes," said Keating. Cytoplasm is usually filled with macromolecules of proteins, nucleic acids and carbohydrates.
A mixture of a small amount of PEG, a small amount of dextran, water and dried lipid allowed the lipid to rehydrate and form the vesicles. The PEG and dextran filled the vesicles to the same concentratio
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