The adaptive iridocytes in the skin of the California market squid are able tune color through most of the spectrum.
A finely tuned molecular process in the camouflage of certain squid may lead to the next generation of bio-inspired synthetic materials
Squids, octopuses and cuttlefish are undisputed masters of deception and camouflage. Their extraordinary ability to change color, texture and shape is unrivaled, even by modern technology.
Researchers in the lab of UC Santa Barbara professor Daniel Morse have long been interested in the optical properties of color-changing animals, and they are particularly intrigued by the opalescent inshore squid. Also known as the California market squid, these animals have evolved the ability to finely and continuously tune their color and sheen to a degree unrivaled in other creatures. This enables them to communicate, as well as hide in plain sight in the bright and often featureless upper ocean.
In previous work, the researchers uncovered that specialized proteins, called reflectins, control reflective pigment cells — iridocytes — which in turn contribute to changing the overall visibility and appearance of the creature. But still a mystery was how the reflectins actually worked.
“We wanted now to understand how this remarkable molecular machine works,” said Morse, a Distinguished Emeritus Professor in the Department of Molecular, Cellular and Developmental Biology, and principal author of a paper that appears in the Journal of Biological Chemistry. Understanding this mechanism, he said, would provide insight into the tunable control of emergent properties, which could open the door to the next generation of bio-inspired synthetic materials.
Light-reflecting skin
Like most cephalopods, opalescent inshore squid, practice their sorcery by way of what may be the most sophisticated skin found anywhere in nature. Tiny muscles manipulate the skin texture while pigments and iridescent cells affect its appearance. One group of cells controls their color by expanding and contracting cells in their skin that contain sacks of pigment.
Behind these pigment cells are a layer of iridescent cells — those iridocytes — that reflect light and contribute to the animals’ color across the entire visible spectrum. The squids also have leucophores, which control the reflectance of white light. Together, these layers of pigment-containing and light-reflecting cells give the squids the ability to control the brightness, color and hue of their skin over a remarkably broad palette.
Unlike the color from pigments, the highly dynamic hues of the opalescent inshore squid result from changing the iridocyte’s structure itself. Light bounces between nanometer-sized features about the same size as wavelengths in the visible part of the spectrum, producing colors. As these structures change their dimensions, the colors change. Reflectin proteins are behind these features’ ability to shapeshift, and the researchers’ task was to figure out how they do the job.
Thanks to a combination of genetic engineering and biophysical analyses, the scientists found the answer, and it turned out to be a mechanism far more elegant and powerful than previously imagined.
“The results were very surprising,” said first author Robert Levenson, a postdoctoral researcher in Morse’s lab. The group had expected to find one or two spots on the protein that controlled its activity, he said. “Instead, our evidence showed that the features of the reflectins that control its signal detection and the resulting assembly are spread across the entire protein chain.”
An Osmotic Motor
Reflectin, which is contained in closely packed layers of membrane in iridocytes, looks a bit like a series of beads on a string, the researchers found. Normally, the links between the beads are strongly positively charged, so they repel each other, straightening out the proteins like uncooked spaghetti.
Morse and his team discovered that nerve signals to the reflective cells trigger the addition of phosphate groups to the links. These negatively charged phosphate groups neutralize the links’ repulsion, allowing the proteins to fold up. The team was especially excited to discover that this folding exposed new, sticky surfaces on the bead-like portions of the reflectin, allowing them to clump together. Up to four phosphates can bind to each reflectin protein, providing the squid with a precisely tunable process: The more phosphates added, the more the proteins fold up, progressively exposing more of the emergent hydrophobic surfaces, and the larger the clumps grow.
As these clumps grow, the many, single, small proteins in solution become fewer, larger groups of multiple proteins. This changes the fluid pressure inside the membrane stacks, driving water out — a type of “osmotic motor” that responds to the slightest changes in charge generated by the neurons, to which patches of thousands of leucophores and iridocytes are connected. The resulting dehydration reduces the thickness and spacing of the membrane stacks, which shifts the wavelength of reflected light progressively from red to yellow, then to green and finally blue. The more concentrated solution also has a higher refractive index, which increases the cells’ brightness.
“We had no idea that the mechanism we would discover would turn out to be so remarkably complex yet contained and so elegantly integrated in one multifunctional molecule — the block-copolymeric reflectin — with opposing domains so delicately poised that they act like a metastable machine, continually sensing and responding to neuronal signaling by precisely adjusting the osmotic pressure of an intracellular nanostructure to precisely fine-tune the color and brightness of its reflected light,” Morse said.
What’s more, the researchers found, the whole process is reversible and cyclable, enabling the squid to continually fine-tune whatever optical properties its situation calls for.
New Design Principles
The researchers had successfully manipulated reflectin in previous experiments, but this study marks the first demonstration of the underlying mechanism. Now it could provide new ideas to scientists and engineers designing materials with tunable properties. “Our findings reveal a fundamental link between the properties of biomolecular materials produced in living systems and the highly engineered synthetic polymers that are now being developed at the frontiers of industry and technology,” Morse said.
“Because reflectin works to control osmotic pressure, I can envision applications for novel means of energy storage and conversion, pharmaceutical and industrial applications involving viscosity and other liquid properties, and medical applications,” he added.
Remarkably, some of the processes at work in these reflectin proteins are shared by the proteins that assemble pathologically in Alzheimer’s disease and other degenerative conditions, Morse observed. He plans to investigate why this mechanism is reversible, cyclable, harmless and useful in the case of reflectin, but irreversible and pathological for other proteins. Perhaps the fine-structured differences in their sequences can explain the disparity, and even point to new paths for disease prevention and treatment.
Learn more: A Marvelous Molecular Machine
The Latest on: Bio-inspired synthetic materials
- High-Tech Toilet Coating Does the Dirty Work For Youon November 19, 2019 at 7:07 am
“Our team has developed a robust bio-inspired liquid-, sludge-, and bacteria-repellent coating that can essentially ... “When we put that coating on a toilet in the lab and dump synthetic fecal matter ...
- New Toilet Coating Saves Wateron November 18, 2019 at 11:30 am
In the Wong Laboratory for Nature Inspired Engineering, housed within the Department of Mechanical Engineering and the Materials Research Institute, researchers have developed a method that ...
- Innovative, Slippery Toilet Coating Saves Water With Cleaner Flushing [Video]on November 18, 2019 at 10:36 am
“Our team has developed a robust bio-inspired, liquid, sludge- and bacteria-repellent coating that can essentially ... In the Wong Laboratory for Nature Inspired Engineering, housed within the ...
- Squid camouflage may lead to next gen of bio-inspired synthetic materialson November 17, 2019 at 9:34 am
Understanding this mechanism, he said, would provide insight into the tunable control of emergent properties, which could open the door to the next generation of bio-inspired synthetic materials.
- A Marvelous Molecular Machineon November 15, 2019 at 11:51 am
Understanding this mechanism, he said, would provide insight into the tunable control of emergent properties, which could open the door to the next generation of bio-inspired synthetic materials.
- Scientists create fake rhino horn from horsehair in a bid to save the specieson November 8, 2019 at 6:03 am
Scientists have developed a fake rhino horn using horsehair, in a bid to create "credible fakes" to flood the market and reduce demand for the material.
- Bio-inspired materialson August 16, 2019 at 10:43 am
Korley utilizes inspiration from nature to design a variety of materials. She is the principal investigator of PIRE: Bio-Inspired Materials and Systems, a five-year, $5.5 million grant from the ...
- Bio-Inspired Material Targets Oceans’ Uranium Stores for Sustainable Nuclear Energyon May 17, 2019 at 1:34 pm
Scientists have demonstrated a new bio-inspired material for an eco-friendly and cost ... The prototype stands out among other synthetic materials for increasing the storage space for uranium, ...
- Bio-inspired Material Can Follow the Sunon January 15, 2019 at 3:54 am
Researchers have developed new, bio-inspired materials that can move in response to different ... However, to date, researchers have managed to develop synthetic LCEs that can deform in only one or ...
- Bio-Inspired Material Keeps Cool at High Temperatureson December 5, 2018 at 4:00 am
A team led by Mark Alston, assistant professor of environmental design from the Faculty of Engineering at Nottingham University, designed the bio-inspired material ... develop a thermally functional ...
via Bing News
The Latest on: Synthetic materials
- Synthetic Biologics Reports on NYSE American Noncompliance Notice and Compliance Planon November 27, 2019 at 1:42 pm
Synthetic Biologics' inability to maintain its material licensing agreements, or a failure by Synthetic Biologics or its strategic partners to successfully commercialize products and other factors ...
- Researchers create new coating to prevent clotting, infection in synthetic vascular graftson November 27, 2019 at 10:34 am
Researchers at McMaster University have created a new coating to prevent clotting and infection in synthetic vascular grafts, while also accelerating the body's own process for integrating the grafted ...
- 'Smart' surfaces help synthetic blood-vessel grafts knit better and more safelyon November 27, 2019 at 5:24 am
The smart materials are made to coat the inner walls of new sections of replacement vessels typically deployed after injury or disease. Synthetic materials currently used in vascular grafts can be ...
- Global HVAC Filters Markets to 2024: Synthetic Polymer Segment Projected to Grow at the Highest CAGRon November 26, 2019 at 4:17 pm
DUBLIN, Nov. 26, 2019 /PRNewswire/ -- The "HVAC Filters Market by Material (Fiberglass, Synthetic Polymer, Carbon), Technology (Electrostatic Precipitator, HEPA, Activated Carbon), End-Use Industry ...
- Highly flammable materials should have no place in our homeson November 26, 2019 at 3:09 pm
I hope your report on highly flammable plastic material in contemporary furnishings caused the same alarm in others as it did in me (“Experts call for more sprinklers in residences,” Metro, Nov. 14).
- Efficient bottom-up synthesis of new perovskite material for the production of ammoniaon November 22, 2019 at 5:21 am
Perovskites are a class of synthetic materials that have a crystalline structure similar to that of the naturally occurring mineral calcium titanate. They have been the subject of many studies ...
- Biodegradable Packaging Material Market Analysis, Overview, Revenue, Growth, Opportunities And Forecast Up To 2025on November 22, 2019 at 4:22 am
These materials might contain acombination of pigments and synthetic materials to increase the functionalcharacteristics of the final stage of packaging. Get PDF template of this report: ...
- Gore-Tex Is Betting Big On Synthetic Biologyon November 19, 2019 at 9:41 am
It was just this April that Checkerspot raised a $13 million Series A to develop this platform to produce synthetic biology-enabled performance materials. Gore has decades of experience in making high ...
- Synthetic biologists developing a new class of high-performance materialson November 18, 2019 at 12:28 pm
Synthetic biologists have developed a process that could lead to a new class of synthetic polymers that may create new high-performance materials and therapeutics for Soldiers. Nature Communications ...
- Kick-starting Moore's Law? New 'synthetic' method for making microchips could helpon November 18, 2019 at 9:48 am
"We are contributing a fundamental advance in rational control of the shape and dimension of nanoscale materials," Kempa said. This method can "sculpt nanoscale crystals in ways that were not readily ...
via Bing News