IAB Life Science Hour Seminar Series
|Professor. University of Illinois at Urbana-Champagne.|
|Title:||The Role of Antifreeze Proteins in Freezing Avoidance of Polar Fishes|
|Date:||Tuesday, 6 September 2016|
|Location:||Murie Life Science Bldg, Murie Auditorium.|
|Host:||Kristin O'Brien and Lara Horstmann|
The polar marine waters are the coldest and iciest on the planet. However the rich invertebrate and fish faunas attests to the fact that they have evolved adaptations to survive in ice-laden freezing seawater. Marine invertebrates do not freeze because they are isosmotic to seawater. Teleost fishes are hypo-osmotic to seawater and thus are in danger of freezing. In both the Arctic and Antarctic oceans many fishes live in close proximity of ice but do not freeze, because they have evolved antifreeze proteins (AFPs). In Antarctic notothenioid fishes they are glycoproteins (AFGPs), composed of repeats of the glycotripeptide ala-ala-thr- with each thr linked to the disaccharide, galactosyl-N-acetylgalactoseamine. AFGPs are made up of many size isoforms that circulate in the blood at 30 to 40 mg/ml, and are found also in most other body fluids including the intestinal fluid. The Arctic fish fauna is much more diverse than the Antarctic fishes. Several sculpins, eel pouts and flat fishes have evolved peptide antifreezes that function the same way the AFGPs do. The polar cods have evolved an identical AFGP to the Antarctic notothenioids but from a different origin.
The accepted mechanism of antifreeze action in freeze avoidance is adsorption to ice and inhibition of ice growth. This mechanism implies that ice is present in the fish and it does enter the blood. The AFPs adsorb to ice crystals and divide the surface into many small domains. As water molecules join these domains, they grow into highly curved fronts, which have large surface free energy unfavorable for further addition of water molecules from the liquid phase. In other words, ice growth soon becomes arrested. For growth to continue, the bulk solution temperature must be lowered, equivalent to lowering the freezing point. This antifreeze mechanism results in a separation of the equilibrium melting point and the temperature of unimpeded ice crystal growth, or non-equilibrium freezing point, which is the hall mark of all antifreeze proteins. Ice growth in the presence of AFPs below the non-equilibrium freezing point is along the c-axis, the thermodynamically non-preferred direction, resulting in the formation of thin ice spicules. The recognition and binding to ice is thought to involve a match between potential hydrogen bonding hydroxyl groups of the AFPs and the oxygens in the ice lattice and is specific for each type of AFP. The adsorption-inhibition mechanism of preventing ice growth has an unintended consequence – it also inhibits melting at the expected equilibrium melting point. Antifreeze bound and growth-arrested ice crystals in northern fishes can be eliminated by summer melting. In high Antarctic latitude however, seasonal warming is insufficient in duration and magnitude to overcome the melting inhibition to eliminate internalized ice. Thus notothenioid fishes are destined to carry potentially injurious ice crystal throughout life.
About the Speaker:
A native of Montana, Art DeVries received a BA in zoology with honors from the University of Montana in 1960. After spending a year at McMurdo Sound, Antarctica, performing research on Antarctic fishes he enrolled in graduate school at Stanford University and studied freezing avoidance in Antarctic fishes. He received his Ph.D. in biology at Stanford University in 1968. In the course of his Ph.D. research he discovered that freezing avoidance in Antarctic fishes resulted from the presence of blood antifreeze glycoproteins. Following a three-year National Institutes of Health post-doctoral fellowship at the University of California, Davis, he received National Science Foundation funding to continue his studies on freezing avoidance at Scripps Institution of Oceanography. During his tenure at Scripps he made six trips to McMurdo Station, Antarctica, where the role of the antifreeze glycoproteins in fish was elucidated.
In 1976 he accepted a position in the Department of Physiology at the University of Illinois, Urbana. In 1998 he became head of the Department of Animal Biology until 2000. In 2011 he retired as professor emeritus and he remains active in research and advising students.
Since 1961 he has spent over 50 seasons conducting research on the cold adaptation of Antarctic fishes with emphasis on the role of the antifreeze proteins in their freezing avoidance. He has made several trips to the Arctic region to examine freezing avoidance in the polar cods and sculpins and participated in the Danish Galathea 3 Expedition to the Antarctic Peninsula and a six-week season with Italian scientists at the Mario Zucchelli at Terra Nova Bay.
His research related to the antifreeze proteins and biology of polar fishes generated 185 publications and the story of the antifreeze proteins and freezing avoidance appears in several comparative physiology textbooks.
Among his honors and awards are: Elected Fellow of the American Association for the Advancement of Science (1984); Evans Visiting Scholar, University of Otago, New Zealand (1985); awarded the Premio Internazionale 'Felice Ippolito' (international prize for biological excellence) by the Italian Accademia Nazionale dei Lincei and National Antarctic Programme (2005); Lifetime Achievement Award for discovery and research on antifreeze proteins in polar fishes at the 1st International Ice-Binding Protein Conference, Queens University, Ontario, Canada (2011); awarded Honorary Doctoral Degree In Natural Sciences H.C. Roskilde University, Copenhagen, Denmark (2014); and the American Physiological Society’s “August Krogh Distinguished Lectureship,” March 2015.
Browse Life Science Hour Seminars
Beginning in 1966 and continuing today, IAB hosts a weekly seminar for faculty, students, staff and the public during the academic year. The series attracts life scientists from Alaska and around the world.
If you wish to meet with a particular speaker, please contact one of the seminar coordinators or the IAB director's office at 907-474-7649.The 2016-2017 faculty coordinators for this seminar series are Greg Breed and Devin Drown. Beginning in 2013, many of the seminars were recorded and can be viewed online. Speakers are listed in chronological order within academic years.
- 8/26/16 (Virginia K. Walker)
- 9/6/16 (Art DeVries)
- 9/7/16 (Chi-Hing Christina Cheng)
- 9/16/16 (Kathryn Clancy)