Squids, Octopuses and Cuttlefish are Undisputed Masters of DECESS 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 sign 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 remakeable 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 turntable control of emergent properies, 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 contribut to the animals' color across the whole visible spectrum. The Squids also have leukophores, 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 remark
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 changes their dimensions, The Colors changes. 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 Analysis, 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 surprise," 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 features of the reflectins that control its signal detection and the resulting assembly are spread across the whole 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 thong, the researchers found. Normally, the links between the beads are strongly positively loaded, so they repel each other, straightering out the proteins like acooked 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 oven phosphates can bind to each reflectin protein, providing the squid with a precisely turntable process: the more phosphates added, the more the proteins fold up, progressively exhibition more of the emergent hydrophobic surfaces, and the larger the clumps grow.
As these Clumpst 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 Finly Blue. The more concentrated solution also has a high refractive index, which increese the cells' brightness.
"We had no idea that the mechanism we would discover would turn out to be so remaked complex yet contained and so elegantly integrated in one multifunctional molecule-The block-crolymeric reflectin-with opposing domains so de Delicately poisd that they actable machine, continually sensing and Reponding 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 Continory Fine-Tune Whatever Optical Properties its situation calls for.
New Design Principles
The Researchers Had Successfully Manipulative Reflectin in Previous Experiment, But this Study Marks the First Demonstration of the underlying mechanism. NOW it could Provide New Ideas to Scientists and Engineers Designing Materials With Turnable Properties. "Our Findings Reveal A Fundamental Link Between The Properties of Biomolecular Materials Produced in Living Systems and the Highly Enginered Synthetic Polymers that are now being developed at the frontiers of industry and technology," Morse Said.
"Becaus reflectin works to control osmotic press, I can invision applications for novel means of energy storage and conversion, pharmaceutical and industrial applications involving viscosity and other liquid properies, and medical applications," he added.
NOTAKABLY, Some of the Processes at Work in these reflectin proteins are shared by the proteins that assembled pathologically in Alzheimer's Disease and other Degenerative Conditions, Morse Observed. He plans to investigate why this mechanism is reversible, cycling, harmless and useful in the case of reflectin, irreversible but pathological for other proteins. Perhaps the Fine-Structure Differentés in Their Sequences Can Explain The Disapity, and Even Point to New Paths for Disease Prevention and Treatment.
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