Helical springs as a color indicator for determining chirality and enantiomeric excess

Chirality captured with a colourful twist

26 November 2021

A colour-changing compound that can precisely indicate the ‘enantiomeric excess’ (ee) of chiral molecules could provide a convenient method to measure pharmaceutical purity.

Many molecular systems in nature are chiral, existing in only one of two mirror-image forms. For pharmaceuticals to interact with the body as intended, they must have the correct chirality — a mismatch would be like trying to slide a right hand into a left glove. Drug makers measure the ee of their products to confirm they have produced a molecule of the correct chirality.

Now, researchers at Kanazawa University in Japan have helped to develop a novel colour-changing ee indicator.

The team developed a polymer shaped like a helical spring, which changes shape — and colour — when it interacts with chiral amine drugs. Differences of less than 2% ee between samples produced colour changes discernible to the naked eye. When the colour change was analysed by digital imaging, the technique rivalled the accuracy of industry-standard, high-performance liquid chromatography for ee determination.

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References

1. Science Advances 7, eabg5381 (2021). doi: 10.1126/sciadv.abg5381