German-French research team improves method for
size-discrimination of individual molecules
(June 10, 2015) A
German-French team led by Prof. Dr. Jan C. Behrends and Dr. Gerhard Baaken from
the University of Freiburg and Dr. Abdelghani Oukhaled from the Universities of
Evry and Cergy-Pontoise has developed a method capable of precisely measuring
the size of individual molecules. To do so, the researchers used the protein
aerolysin from the bacterium Aeromonas hydrophila instead of the protein
previously used for this purpose, alpha-hemolysin from the bacterium
Staphylococcus aureus. The method remains unchanged: The protein forms a pore
in an artificial cell membrane. The researchers insert the molecule whose size
they wish to measure into this pore by guiding an ionic current through it. The
molecule partially blocks this current – similar to the way an object illuminated
by a spotlight throws a shadow. The rest of the ionic current, which makes it
through the pore, can then be used to measure the molecule. “The new pore is
much more suitable for determining the entire size range of molecules,” says
Behrends. The researchers published their findings in the journal ACS Nano