Tavagnacco Letizia, Chiessi Ester, Zanatta Marco, Orecchini Andrea, Zaccarelli Emanuela
CNR-ISC and Department of Physics , Sapienza University of Rome , Piazzale A. Moro 2 , 00185 Rome , Italy.
Department of Chemical Sciences and Technologies , University of Rome Tor Vergata , Via della Ricerca Scientica I , 00133 Rome , Italy.
J Phys Chem Lett. 2019 Feb 21;10(4):870-876. doi: 10.1021/acs.jpclett.9b00190. Epub 2019 Feb 12.
The long debated protein dynamical transition was recently found also in nonbiological macromolecules, such as poly- N-isopropylacrylamide (PNIPAM) microgels. Here, by using atomistic molecular dynamics simulations, we report a description of the molecular origin of the dynamical transition in these systems. We show that PNIPAM and water dynamics below the dynamical transition temperature T are dominated by methyl group rotations and hydrogen bonding, respectively. By comparing with bulk water, we unambiguously identify PNIPAM-water hydrogen bonding as mainly responsible for the occurrence of the transition. The observed phenomenology thus crucially depends on the water-macromolecule coupling, being relevant to a wide class of hydrated systems, independently from the biological function.
长期以来备受争议的蛋白质动力学转变最近在非生物大分子中也被发现，例如聚N-异丙基丙烯酰胺（PNIPAM）微凝胶。在此，通过使用原子分子动力学模拟，我们报告了这些系统中动力学转变的分子起源描述。我们表明，在动力学转变温度T以下，PNIPAM和水的动力学分别由甲基旋转和氢键主导。通过与体相水比较，我们明确确定PNIPAM-水氢键是转变发生的主要原因。因此，观察到的现象学关键取决于水-大分子耦合，这与广泛的水合系统相关，与生物功能无关。
