Featured Research

from universities, journals, and other organizations

Acidity can change cell membrane properties

Date:
October 1, 2013
Source:
Northwestern University
Summary:
Understanding cell bilayers is important for advances in biology and biotechnology. Now an interdisciplinary team of researchers has determined how to control their properties in a new way.

Changes in the packing of the tails into a hexagonal, rectangular-C, or rectangular-P lattice are observed at various pH levels.
Credit: Northwestern University

Of all the amazing technologies humans have developed, none has matched the complexity of the fundamental building block of nature: the living cell. And none of the cell's activities would be possible without thin lipid membranes, or bilayers,that separate its parts and regulate their functions.

Changes in the packing of the tails into a hexagonal, rectangular-C, or rectangular-P lattice are observed at various pH levels.

Understanding and controlling bilayers' properties is vital for advances in biology and biotechnology. Now an interdisciplinary team of Northwestern University researchers has determined how to control bilayers' crystallization by altering the acidity of their surroundings.

The research, published September 24 in the Proceedings of the National Academy of Sciences, sheds light on cell function and could enable advances in drug delivery and bio-inspired technology.

"In nature, living things function at a delicate balance: acidity, temperature, all its surroundings must be within specific limits, or they die," said co-author Monica Olvera de la Cruz, Lawyer Taylor Professor of Materials Science and Engineering, Chemistry, and (by courtesy) Chemical and Biological Engineering at 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."The research, published September 24 in the Proceedings of the National Academy of Sciences, sheds light on cell function and could enable advances in drug delivery and bio-inspired technology.Understanding and controlling bilayers' properties is vital for advances in biology and biotechnology. Now an interdisciplinary team of Northwestern University researchers has determined how to control bilayers' crystallization by altering the acidity of their surroundings.

By taking advantage of the charge in the molecules' head groups, the Northwestern researchers developed a new way to modify the membrane's physical properties. They began by co-assembling dilysine (+2) and carboxylate (-1) amphiphile molecules of varying tail lengths into bilayer membranes at different pH levels, which changed the effective charge of the heads. Bilayers are made of two layers of amphiphile molecules -- molecules with both water-loving and water-hating properties -- that form a crystalline shell around its contents. Shaped like a lollipop, amphiphile molecules possess a charged, water-loving (hydrophilic) head and a water-repelling (hydrophobic) tail; the molecules forming each layer line up tail-to-tail with the heads forming the exterior of the membrane. The density and arrangement of the molecules determine the membrane's porosity, strength, and other properties.

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 bilayers' molecules.

(To produce electron microscope images of membrane structures, researchers previously have frozen them, but this process is labor-intensive and changes the structural fidelity, which makes it less relevant for understanding membrane assembly and behavior under physiological conditions as carried out inside the human body.)

The Northwestern researchers found that most molecules did not respond to a change in acidity. But those that possessed a critical tail length -- a measure that correlates to the molecules' level of hydrophylia -- the charge of the molecules' heads changed to the extent that their two-dimensional crystallization morphed from a periodic rectangular-patterned lattice (found in more basic solutions) to a hexagonal lattice (found in more acidic solutions). Shells with a higher symmetry, such as hexagonal, are stronger and less brittle than those with lesser symmetry. The change in pH also altered the bilayers' thickness and the compactness of the molecules.

Changing the density and spacing of molecules within membranes could help researchers control the encapsulation and release efficiency of molecules inside a vesicle.


Story Source:

The above story is based on materials provided by Northwestern University. Note: Materials may be edited for content and length.


Journal Reference:

  1. C.-Y. Leung, L. C. Palmer, S. Kewalramani, B. Qiao, S. I. Stupp, M. Olvera de la Cruz, M. J. Bedzyk. Crystalline polymorphism induced by charge regulation in ionic membranes. Proceedings of the National Academy of Sciences, 2013; DOI: 10.1073/pnas.1316150110

Cite This Page:

Northwestern University. "Acidity can change cell membrane properties." ScienceDaily. ScienceDaily, 1 October 2013. <www.sciencedaily.com/releases/2013/10/131001124012.htm>.
Northwestern University. (2013, October 1). Acidity can change cell membrane properties. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2013/10/131001124012.htm
Northwestern University. "Acidity can change cell membrane properties." ScienceDaily. www.sciencedaily.com/releases/2013/10/131001124012.htm (accessed July 31, 2014).

Share This




More Plants & Animals News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Xtreme Eating: Your Daily Caloric Intake All On One Plate

Xtreme Eating: Your Daily Caloric Intake All On One Plate

Newsy (July 30, 2014) The Center for Science in the Public Interest released its 2014 list of single meals with whopping calorie counts. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



      Save/Print:
      Share:

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile: iPhone Android Web
      Follow: Facebook Twitter Google+
      Subscribe: RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins