Friday, 19 December 2014

New research uses bioluminescent jellyfish as optical engineers

Researchers at St Andrews have produced the world’s first solid-state protein lasers, capable of record performance and some capable of self-assembly, by harnessing the optical engineering skills of bioluminescent jellyfish.

The findings, reported in the international journal Nature Communications ("Bio-optimized energy transfer in densely packed fluorescent protein enables near-maximal luminescence and solid-state lasers", doi: 10.1038/ncomms6722), have the potential to transform biomedical diagnosis of conditions such as cancer and advance the design of new materials. The work was inspired by the discovery that nature may have optimized - with sub-nanometre precision - the size of the molecules driving the bioluminescence of jellyfish to allow them to shine as brightly as possible. Professor Malte Gather from the School of Physics and Astronomy, together with Dr Seok Hyun Yun at Harvard Medical School and Massachusetts General Hospital, calculated that the green fluorescent protein molecule, which allows certain jellyfish to emit bright green light, has just the right size to strike an optimal balance between not losing energy to unproductive quenching and being able to squeeze as many molecules as possible into the light-emitting cells of the animal.

Fluorescent proteins derived from bioluminescent jellyfish
allow fabrication of efficient solid-state microlasers.
Under the right conditions, the protein molecules self-assemble
into a ring-shaped laser structure. Shown above are two such
lasers in action, made from a green and a red fluorescent protein, respectively.

Bioinspired by nature’s design, the researchers were able to make tiny solid-state lasers from these fluorescent proteins. The green fluorescent protein, generally known as GFP, is found the pacific jellyfish Aequorea Victoria where it is involved as energy acceptor in the natural bioluminescence of the animal. Several years ago molecular biologists isolated the section of DNA that tells the cellular machinery of the jellyfish how to produce GFP. Using genetic engineering this DNA can be used to confer the bright green fluorescence to other species - to bacteria, fruit flies, even to mice - a method that is widely used today to visualize cells or structures within cells under the microscope. Such measurements require only relatively modest protein concentrations. In the light-emitting organ of the jellyfish, however, the protein concentration is believed to be more than thousand times higher.

The scientists developed a number of different laser configurations. A particularly efficient design began to emit laser light when the power provided to it was less than what can be achieved in lasers based on state-of-the-art synthetic dyes. Another design makes use of the concept of self-assembly and allows the structure of the laser to form by itself. Professor Gather believes that beyond using GFP and other fluorescent proteins, the study of their structure and their optical properties can bio-inspire improvements of artificial emitters. [Press release]