Naik Rajesh R.

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Naik
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Rajesh R.
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  • Preprint
    Biological versus electronic adaptive coloration : how can one inform the other?
    ( 2011-11) Kreit, Eric ; Mathger, Lydia M. ; Hanlon, Roger T. ; Dennis, Patrick B. ; Naik, Rajesh R. ; Forsythe, Eric ; Heikenfeld, Jason
    Adaptive reflective surfaces have been a challenge for both electronic paper (e-Paper) and biological organisms. Multiple colours, contrast, polarization, reflectance, diffusivity and texture must all be controlled simultaneously without optical losses in order to fully replicate the appearance of natural surfaces and vividly communicate information. This review merges the frontiers of knowledge for both biological adaptive coloration, with a focus on cephalopods, and synthetic reflective e-Paper within a consistent framework of scientific metrics. Currently, the highest performance approach for both nature and technology utilizes colourant transposition. Three outcomes are envisioned from this review: reflective display engineers may gain new insights from millions of years of natural selection and evolution; biologists will benefit from understanding the types of mechanisms, characterization, and metrics used in synthetic reflective e-Paper; all scientists will gain a clearer picture of the long-term prospects for capabilities such as adaptive concealment and signalling.
  • Preprint
    Changes in reflectin protein phosphorylation are associated with dynamic iridescence in squid
    ( 2009-07-18) Izumi, Michi ; Sweeney, Alison M. ; DeMartini, Daniel ; Weaver, James C. ; Powers, Meghan L. ; Tao, Andrea ; Silvas, Tania V. ; Kramer, Ryan M. ; Crookes-Goodson, Wendy J. ; Mathger, Lydia M. ; Naik, Rajesh R. ; Hanlon, Roger T. ; Morse, Daniel E.
    Many cephalopods exhibit remarkable dermal iridescence, a component of their complex, dynamic camouflage and communication. In the species Euprymna scolopes, the light-organ iridescence is static and is due to reflectin protein-based platelets assembled into lamellar thin-film reflectors called iridosomes, contained within iridescent cells called iridocytes. Squid in the family Loliginidae appear to be unique in that the dermis possesses a dynamic iridescent component, with reflective, colored structures that are assembled and disassembled under the control of the muscarinic cholinergic system and the associated neurotransmitter acetylcholine (Mathger et al. 2004). Here we present the sequences and characterization of three new members of the reflectin family associated with the dynamically changeable iridescence in Loligo and not found in static Euprymna iridophores. In addition, we show that application of genistein, a protein tyrosine kinase inhibitor, suppresses acetylcholine- and calcium-induced iridescence in Loligo. We further demonstrate that two of these novel reflectins are extensively phosphorylated in concert with the activation of iridescence by exogenous acetylcholine. This phosphorylation and the correlated iridescence can be blocked with genistein. Our results suggest that tyrosine phosphorylation of reflectin proteins is involved in the regulation of dynamic iridescence in Loligo.