Effects of the Ionic Liquid Ethyl Ammonium Nitrate on the Structure and Function of the Potential Therapeutic Agent Gelsolin
Vogel, Harrison S.
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Gelsolin is a protein that upon Ca activation, acts to nucleate and cap the cytoskeletal protein actin in the human body and has been shown to break apart filamentous actin released into the bloodstream from assorted medical conditions (1,2,4, 5, 15). The relative instability of this protein poses a problem for transportation and storage. Sugars and certain ionic liquids such as ethyl ammonium nitrate (EAN) have been shown to slow aggregation and thermally stabilize some proteins (25). In this paper, the thermal stability of human recombinant gelsolin (hGS) and the effects of EAN on its secondary structure and aggregation were studied. Secondary structure loss associated with the change in fluorescence spectra of hGS when activated by Ca is different than when exposed to 1M or greater EAN, which behaves more like the denaturant Urea. The expanded structure of hGS in the presence of EAN is greater (Rg = 50 ± 10 A and Dmax s 200 A) than upon Ca2+ activation (Rg =49.3 ±0.2 A and Dmax s 150 A) while the addition of EAN to Ca2+ activated hGS did not affect the structural dimensions when observed by SAXS, EAN however prevented aggregation (decrease in Iq/c). EAN would be useful to prevent aggregation during storage and transportation if hGS can refold post EAN exposure in solution. However, as a stabilizing agent for therapeutic gelsolin, EAN would need to be mixed with liquids thermally stabilize sugars or other ionic liquids in order to be effective.