Molecules can be manipulated to 'alter' light-absorbing properties

Molecules can be altered in order to change their light-absorbing properties, a new study has determined.

Chemical and Engineering News has reported that chemists from Michigan State University came across the discovery and believe the work could lead to new biobased sensors, along with light-harvesting proteins for solar energy and new protein tags for biological research.

The light receptor proteins in colour vision all use the 11 cis retinal molecule to absorb light throughout the visible spectrum, and nature somehow regulates its wavelength, allowing it to cover a very long range to detect a number of colours.

With this in mind, Babak Borhan, James H. Geiger and colleagues investigated how nature does this and tested ways of pushing the absorption profile as far as possible.

A cellular retinol-binding protein (CRBP) was used in their laboratory work in order to mimic the electronic properties of rhodopsin-retinal complexes, with the technology being engineered so that it binds all transretinal, which is easier to study than 11-cis-retinal.

The experts were surprised when they saw their work pushed the absorption profile to wavelengths beyond those thought possible.

The most red-shifted protein had a maximum profile of 644 nm, even though it was previously believed no retinal could stretch further than around 620nm.

"I think we have the opportunity to go even farther than 644 nm. I’m not sure how much more we can go, but I don’t think we’re at the upper limit yet. We have the ability to dial in whatever color we want, depending on the protein sequence. They are also developing variants that bind fluorescent molecules. “Fluorescence is really the name of the game for protein fusion tags," Mr Borhan explained to the news provider.

Mr Geiger also commented on the work, noting: "We believe that our work provides a ‘toolbox’ of principles and strategies that can be used for controlling the spectroscopic properties of not just retinal, but potentially a variety of chromophores."

Posted by Neil Clark