Research Biophysics

Mechanical properties of proteins

Proteins are complex organic macromolecules that are the fundamental components of all living cells. Twenty different amino acids are common to proteins, linked in chains of hundreds to thousands of units. Proteins have three important levels of structure: primary (the amino acid sequence), determined by the genes; secondary (the geometric shape, often a helix), determined by the angles of the covalent bonds between and within amino acids; and tertiary (the looped and folded overall shape), determined largely by attraction between oppositely charged groups (and repulsion between like charged groups) on amino-acid side chains and especially by hydrogen bonding. The tertiary structure, which can be globular or sheetlike with ridges, crevices, or pockets, often holds the key to a protein's biological activity.

The mechanical properties of proteins are believed to play a central role in their normal behavior. Single molecule manipulation is used to investigate how proteins respond to applied forces.

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The results of force-extension experiments are one of the best ways to assess the mechanical properties of structures. Even though the simplest idealistic case considers a linear force-extension relationship, real structures show more complex dependence, as happens for the twin helices bellow.

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Many diseases, like severe muscle disorders, viral infections, cardiopathies, etc., are linked to changes in the mechanical properties of these elements. In order to quantify these properties, we use a combination of molecular dynamics simulations and statistical models. The molecular models allow us to obtain the necessary data that subsequently will be compared with mesoscale models.

References

1. Alcaraz, Alamo, Barrera, Mateu, Neira, Biophysical Journal (2007) 93, 1264
2. Bharadwaj, Shah, Tariq, Damartoski, Prasad, Cancer Letters (2005) 229, 253
3. Root, Yadavalli, Forbes, Wang, Biophysical Journal (2006) 90, 2852
4. Sarin, Gaffin, Meininger, Muthuchamy, Journal ofPhysiology (2005) 564.2, 603

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