Synthetic protein nanosheets reveal a surprising “twist”

Peptoids are synthetic molecules similar to peptides but with side groups that protrude from nitrogen rather than carbon atoms along the chain’s molecular “backbone”.

“This seemingly small change in chemical connectivity has dramatic effects,” says chemist Glenn Butterfoss from New York University Abu Dhabi. “For example, it turns out that it is much easier to incorporate a wider variety of side chains in peptoids relative to peptides and proteins.”

Scientists believe that recently discovered peptoid nanosheets have exciting potential to be engineered for use as nanofilters, catalysts and in molecular recognition (for example, to identify the presence of particular proteins in biological samples). However, not much was understood about the internal structure of peptoid nanosheets until now.

Scientists from Lawrence Berkeley National Laboratory in the US and New York University Abu Dhabi used computer simulations, together with previously reported experimental data, to determine the atomic structure of peptoid nanosheets. 

In common motifs seen in proteins, each unit has the same “torsional state”, twisting the chain into a helix. Surprisingly, the researchers found that peptoids exhibited an alternating “binary” pattern — successive units had opposing torsions, with the ultimate result of a linear strand. This has never been observed in naturally occurring proteins. 

“Now that we know the precise spatial relationships in the sheets, engineering them to contain things like catalytic and selective molecular binding sites becomes a much more clearly defined challenge,” says Butterfoss.  

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