Photoreceptor molecule genetically modified to “see” red

Nature : Rhodopsin is a light-sensing pigment in the photoreceptor cells of human retinas. It consists of proteins called opsins surrounding a chromophore molecule called retinal. Rhodopsin’s peak absorbance ranges in wavelength from 420 nm (blue) to 560 nm (green). When retinal absorbs a photon, the molecule changes shape and triggers the transmission of an electrical signal to the brain. Babak Borhan from Michigan State University and his research team genetically engineered a variation of rhodopsin that was able to absorb wavelengths up to 644 nm (red). Borhan’s work sheds light on how pigment molecules absorb the ranges of light that they do. By altering the amino acids in the pigment, the researchers caused the electrical charge of the molecule to be more evenly distributed instead of localizing at a particular spot. That change alone was responsible for the redshift in absorption. Because of the simplicity of the change, it appears that the ability to engineer other pigments is not far away.