A US molecular biologist has developed a molecular sieve using a DNA crystal with nanoscale channels.

A US molecular biologist has developed a molecular sieve using a DNA crystal with nanoscale channels. 

Paul Paukstelis from the University of Texas at Austin created his DNA crystal by mixing two different types of single strand DNA - a 24-base assembly strand and an 11-base spacer strand - in the presence of magnesium ions. The spacer strand could bind to a complementary section of the assembly strand, leaving smaller sections at the ends of the assembly strands that would then bind to each other. 

The DNA strands self-assembled into a repeating hollow star shape, producing 3D crystals with 9nm-diameter channels running through them. Paukstelis then found that proteins with molecular weights below 45kDa, such as ovalbumin and myoglobin, could fit into these channels, with smaller proteins being absorbed to a greater extent than larger ones. 

In this way, Paukstelis showed that these DNA crystals can act as zeolite-like molecular sieves, which could be used as catalysts and for chromatographic separations. In addition, if absorbed molecules could be placed at precise locations in the DNA crystals, they could be used as molecular scaffolds and also as crystal hosts for conducting atomic-scale structural analyses.

Other researchers developing DNA structures are excited about this latest work. ’Demonstrating that proteins can diffuse into DNA crystals without causing disruption of the hydrogen-bonded lattice is an impressive result,’ said Thomas LaBean, associate professor of chemistry and computer science at Duke University, US. 

Nadrian Seeman, professor of chemistry at New York University, agrees. ’It is the first example of which I am aware where a 3D DNA array has been used as a method of selecting for the molecular weight of a component in solution,’ said Seeman.

Jon Evans