From ribbon to scroll: Gaining shape control by electrostatics

phys.org | 10/1/2013 | Staff
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Northwestern Engineering materials science researchers have uncovered new insights into how electrostatic interactions can be regulated to attain and control scroll-like cochleate structures, which could inform how to capture and release macromolecules in a size-selective manner as part of future drug-delivery strategies.

Charged molecules, such as DNA and proteins, are present throughout biological systems. Membranes, a bilayer of these charged lipid molecules, are used to compartmentalize matter in a variety of structural forms, from spherical vesicles to helical nanoribbons to cochleates.

Biology - Molecules - Form - Shapes - Variations

"In biology, molecules take the form of many coexisting shapes. Some are decided based on the variations placed upon them, such as concentrations of pH or salt," said Monica Olvera de la Cruz, Lawyer Taylor Professor of Materials Science and Engineering at the McCormick School of Engineering.

"Using a simple charged biomolecule, we have shown how the interplay between electrostatic, elastic, and interfacial energies can lead to structural polymorphism, or coexistence of multiple shapes. While cochleate structures have been observed in other systems, the entire pathway for their formation had not been explained," she added.

Team - Findings - Paper - Shape - Control

The team's findings were published in a paper, titled "Electrostatic Shape Control of a Charged Molecular Membrane from Ribbon to Scroll," on October 14 in Proceedings of the National Academy of Sciences. Olvera de la Cruz was the study's co-corresponding author along with Michael Bedzyk, professor of materials science and engineering.

Using a combination of microscopy techniques and small- and wide-angle X-ray scattering, the team studied changes to the membrane shape of a charged amphiphilic molecule called C16-K1, composed of a hydrophilic single amino acid headgroup and a 16-carbon-long hydrophobic tail. A salt-based solution screened the charge of the headgroup of the membrane, allowing researchers to control the range of electrostatic interactions.

Molecules - Way - Molecule

"We repeated the C16-K1 molecules in a crystalline 2-D way, and each molecule carried particular left or right...
(Excerpt) Read more at: phys.org
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