Experimental and Modeling Study of the Optical Properties and Phase Behavior of Heat and Cold Tolerant Eye Lens Crystallins

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Non-technical summaryThe objective of this project is to understand and mimic the properties of structural proteins that are adapted to resist extreme environments. A combination of experimental and theoretical techniques will be used to explore the molecular mechanisms by which eye lens proteins from different organisms maintain transparency. The scientific goal is to understand how nature produces transparent, durable biomaterials, as exemplified by the proteins making up the eye lens. The lenses of animals that live in very hot, cold, or UV light-saturated environments can provide a guide to making robust, biodegradable materials that withstand harsh conditions. The knowledge gained from this project will guide the design of flexible materials with potential applications to new biomimetic lens designs, in both the medical and analytical chemistry contexts, flexible microlenses, and self-healing materials that resist UV-light damage. In the future, it could enable the development of bioinorganic hydrogel scaffolds, controllable membraneless bioreactors, and ocean-safe, biodegradable sunscreen. The educational plan includes training of students at the Ph.D. and undergraduate levels. These students will be trained not only in the specific skills needed to complete the research, but also in critical thinking, scientific communication, and problem solving across disciplinary boundaries. Another important component is outreach to middle school and high school students in grades 6-12. The goal of the outreach program is to increase interest in science as a career among middle school students. The students, many of whom are from disadvantaged economic backgrounds, visit UCI to participate in a campus tour where they learn about undergraduate life, perform hands-on activities in the investigators’ laboratories, and interact with undergraduate researchers.  Technical summaryThe objective of this project is to understand the solubility and stability of proteins that are adapted to resist extreme environments. Experimental and modeling studies of highly stable structural proteins that play the same functional role in very different environments will provide insight into sequence determinants of stability and solubility. Structural and refractive proteins are chosen specifically to avoid interference from sequence features that are conserved to maintain chemical activity in thermostable enzymes. The scientific goal of this project is to understand how nature produces transparent, durable biomaterials, as exemplified by the proteins making up the eye lens. Although the molecular details of these proteins vary among different organisms, they are functionally similar in their high stability and resistance to temperature extremes. The specific proteins chosen for this effort are eye lens crystallins that are adapted to extreme environments. The J2 crystallin from the box jellyfish Tripedalia cystophora and the βγ-crystallin from the tunicate Ciona intestinalis are extremely stable with respect to heat denaturation. These proteins are not homologous but share a common function; we seek to understand the sequence and structural determinants of thermal stability. On the other hand, the γS- and γM-crystallins from the Antarctic toothfish (Dissostichus mawsoni) resist cold cataract at -2 C or lower, far below the temperature at which mammalian lenses undergo cold cataract. These proteins exist in a complex mixture, with 13 paralogs in the fish lens. One goal is to understand and control the liquid-liquid phase separation involved in cold cataract. The iota-crystallin from the diurnal gecko Lygodactylus picturatus binds a modified form of the visual pigment retinol to protect its retinae from UV light damage in bright sunlight. NMR and optical spectroscopy, light scattering, and directed mutagenesis experiments will be coupled with molecular dynamics and Monte Carlo simulations to elucidate the important structural factors and intermolecular interactions that confer high stability and resistance to extreme conditions on these proteins, guiding the future design of biomimetic materials. Understanding the structural factors diverse lens proteins have in common will help guide the design of future temperature- and UV-resistant biomimetic materials. Furthermore, the ability to predict and control the formation and dissociation of liquid-liquid phase separation in protein mixtures will be useful for modulating protein aggregation and biochemical activity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.