A simple, chemical-materials model could lead to a better understanding of cell structure and assembly, according to a Penn State researcher. "Cells exhibit organization at the cytoplasmic level, which is interesting and important to cellular function, but how this organization is achieved is not known," said Christine Keating, associate professor of chemistry. "We are using a materials chemistry approach to develop simple experimental models for cytoplasmic organization," he told attendees at the 2009 meeting of the American Association for the Advancement of Science. Cytoplasm is the material that fills the cell and is filled with very large molecules. It surrounds organelles – tiny organelles such as mitochondria and nuclei. Unlike organelles, cytoplasm is a major feature of all cells. Many important biochemical processes take place here, and therefore the cytoplasm plays a key role in the functioning of cells. Creating a cell with organelles can be a daunting task, but it is possible to use large polymer molecules and lipid membranes that exhibit molecular packing and heterogeneity—compositional heterogeneity.
Keating uses lipids to create vesicles, tiny intracellular executive database bubbles of lipid membrane, in an aqueous solution of two large polymers. In one case, poly(ethylene glycol) (PEG)—a general polymer—and dextran—a polymerized sugar—were used to form the cell. "Neither of these compounds are essential in the cell, but they do show the possibility of sequestering large molecules without the presence of membranes inside the cell," Keating said. The 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 allows the lipid to liquefy and form vesicles. PEG and dextran filled the vesicles to the same concentration as the surrounding fluid. A lipid membrane encapsulated a mixture of PEG and dextran in water, but the material separated to form two distinct regions, one with a higher percentage of PEG and one with a higher percentage of dextran.
"Materials are completely inseparable with one type of macromolecule in one compartment and another," Keating said. "But the two aqueous phases differ enough that additional molecules, such as proteins or nucleic acids, concentrate there preferentially." In many materials, the researchers were able to induce aqueous phase separation of 15 different compounds. Similarly, the cytoplasm of a cell can have many differences. Biologists know that enzymes and other proteins can bind or bind together in certain parts of the cell at certain times. This colocalization will speed up chemical reactions in metabolic pathways because the chemicals needed for the next step will be located nearby.
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Тема: Artificial Cells Are A Simple Model For A Complex Structure (Прочитано 23 раз)