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Karsten W Jacobsen

Publications and source records attributed to Karsten W Jacobsen.

4 recordsLinked to original sources
PubMed2004

Elastic effects behind cooperative bonding in beta-sheets.

We present extensive density functional theory calculations of the bonding between strands in beta-sheets. We identify a significant cooperative effect whereby the interaction increases in strength with the number of strands. We show that the effect is related to a coupling between interstrand bonding and intrastrand elastic properties. It is found that a direct consequence of this coupling is that the pitch of beta-sheets should contract with increasing number of strands, and we show that the effect can be observed directly in experimental data from the Protein Data Bank.

Models, Molecular↗
PubMed2003

Beta-sheet preferences from first principles.

The natural amino acids have different preferences of occurring in specific types of secondary protein structure. Simulations are performed on periodic model beta-sheets of 14 different amino acids, at the level of density functional theory, employing the generalized gradient approximation. We find that the statistically observed beta-sheet propensities correlate very well with the calculated binding energies. Analysis of the calculations shows that the beta-sheet propensities are determined by the local flexibility of the individual polypeptide strands.

Amino Acids↗
PubMed2003

A maximum in the strength of nanocrystalline copper.

We used molecular dynamics simulations with system sizes up to 100 million atoms to simulate plastic deformation of nanocrystalline copper. By varying the grain size between 5 and 50 nanometers, we show that the flow stress and thus the strength exhibit a maximum at a grain size of 10 to 15 nanometers. This maximum is because of a shift in the microscopic deformation mechanism from dislocation-mediated plasticity in the coarse-grained material to grain boundary sliding in the nanocrystalline region. The simulations allow us to observe the mechanisms behind the grain-size dependence of the strength of polycrystalline metals.

Journal Article↗