Features Partner Sites Information LinkXpress
Sign In
Advertise with Us
RANDOX LABORATORIES

Events

06 Jun 2016 - 09 Jun 2016
22 Jun 2016 - 24 Jun 2016
04 Jul 2016 - 06 Jul 2016

pH-Dependence Described for Key Membrane Bilayer Properties

By BiotechDaily International staff writers
Posted on 16 Oct 2013
Print article
Image: pH-dependent changes in intermolecular packing and symmetry of bilayer tails (Photo courtesy of Northwestern University).
Image: pH-dependent changes in intermolecular packing and symmetry of bilayer tails (Photo courtesy of Northwestern University).
Scientists have discovered specific pH-dependent changes in structural symmetry and density of bilayer membranes, enabling a new venue for controlled alteration of properties important for advancement of cell biology and biotechnology.

The study, an interdisciplinary collaboration between multiple Northwestern University laboratories led by principal investigators of Northwestern’s McCormick School of Engineering and Applied Science (Evanston, IL, USA), showed how crystalline order within bilayer membranes, formed from coassembled cationic- and anionic-head amphiphile molecules, can be controlled by varying pH and molecular hydrophobic-tail length. “In nature, living things function at a delicate balance: acidity, temperature, all its surroundings must be within specific limits, or they die,” said Prof. Monica Olvera de la Cruz of Northwestern’s McCormick School of Engineering; “When living things can adapt, however, they are more functional. We wanted to find the specific set of conditions under which bilayers, which control so much of the cell, can morph in nature.”

In bilayer membranes, the two layers of amphiphile molecules form a crystalline shell around its contents. The density and arrangement of the molecules determine the membrane’s porosity, strength, and other properties. Taking advantage of the ionizable charge in the head groups, the team coassembled dilysine (+2) and carboxylate (-1) amphiphile molecules of varying hydrophobic-tail lengths into bilayer membranes at various (physiologically relevant) pH levels, which changed the effective charge of the heads. Then, using X-ray scattering technology at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) at Argonne National Laboratory’s Advanced Photon Source, the researchers analyzed the resulting crystallization formed by the bilayer molecules. Freezing has generally been used to produce electron microscope images of membrane structures, however this process is labor-intensive and changes the structural fidelity, making it less relevant for understanding membrane assembly and behavior under physiological conditions.

From the results, the researchers found that most molecules did not notably respond to the change in acidity, but for those that possessed a critical tail length (which correlates to the level of hydrophylia) the charge of the heads changed to the extent that their two-dimensional crystallization morphed from a periodic rectangular-patterned lattice in more basic pH solutions to a hexagonal lattice in more acidic pH solutions. Shells with a higher symmetry (e.g., hexagonal) are stronger and less brittle than those with lesser symmetry. The change in pH also altered bilayer thickness and compactness. Changing the crystallinity, density, and spacing of molecules within membranes could help researchers control diffusion rates and the encapsulation and release efficiency of molecules in vesicles, which would further shed light on cell function and could enable advances in drug delivery and other bio-inspired technology.

The study was published ahead of print online September 24, 2013, in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

Related Links:
McCormick School of Engineering and Applied Science at Northwestern University



Print article

Channels

Genomics/Proteomics

view channel
Image: A dark field photomicrograph showing the spirochete bacterium Borrelia burgdorferi, the pathogen responsible for causing Lyme disease (Photo courtesy of the CDC).

Statins May Help Block Transmission of Lyme Disease

A recent study found that treatment with cholesterol-lowering statins reduced the number of Borrelia burgdorferi bacteria in rodents, which helped to block transmission of Lyme disease. Lyme disease... Read more

Drug Discovery

view channel

Experimental Small-Molecule Anticancer Drug Blocks RAS-binding Domains

The experimental small-molecule anticancer drug rigosertib was shown to block tumor growth by acting as an RAS-mimetic and interacting with the RAS binding domains of RAF kinases, resulting in their inability to bind to RAS, which inhibited the RAS-RAF-MEK pathway. Oncogenic activation of RAS genes due to point mutations... Read more

Lab Technologies

view channel

Huge Modifiable Biomedical Database to Be Available on the Wikidata Site

Genome researchers are exploiting the power of the open Internet community Wikipedia database to create a comprehensive resource for geneticists, molecular biologists, and other interested life scientists. While efficiency in generating scientific data improves almost daily, applying meaningful relationships between... Read more

Business

view channel

European Biotech Agreement to Promote Antigen-Drug Conjugation Technology

Two European biotech companies have joined forces to exploit and commercialize an innovative, site-specific ADC (antigen-drug conjugate) conjugation technology. ProBioGen (Berlin, Germany), a company specializing in the development and manufacture of complex glycoproteins and Eucodis Bioscience (Vienna, Austria), a... Read more
Copyright © 2000-2016 Globetech Media. All rights reserved.