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pH-Dependent Adsorption of Peptides on Montmorillonite for Resisting UV Irradiation

by Rongcan Lin 1,†, Yueqiao Wang 1,†, Xin Li 1, Yan Liu 1,* and Yufen Zhao 1,2,3
1
Department of Chemical Biology, Key Laboratory for Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
2
Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, China
3
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing 100084, China
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Life 2020, 10(4), 45; https://doi.org/10.3390/life10040045
Received: 19 February 2020 / Revised: 14 April 2020 / Accepted: 17 April 2020 / Published: 20 April 2020
(This article belongs to the Special Issue Clays and the Origin of Life)
Ultraviolet (UV) irradiation is considered an energy source for the prebiotic chemical synthesis of life’s building blocks. However, it also results in photodegradation of biology-related organic compounds on early Earth. Thus, it is important to find a process to protect these compounds from decomposition by UV irradiation. Herein, pH effects on both the adsorption of peptides on montmorillonite (MMT) and the abilities of peptides to resist UV irradiation due to this adsorption were systematically studied. We found that montmorillonite (MMT) can adsorb peptides effectively under acidic conditions, while MMT-adsorbed peptides can be released under basic conditions. Peptide adsorption is positively correlated with the length of the peptide chains. MMT’s adsorption of peptides and MMT-adsorbed peptide desorption are both rapid-equilibrium, and it takes less than 30 min to reach the equilibrium in both cases. Furthermore, compared to free peptides, MMT-adsorbed peptides under acidic conditions are well protected from UV degradation even after prolonged irradiation. These results indicate amino acid/peptides are able to concentrate from aqueous solution by MMT adsorption under low-pH conditions (concentration step). The MMT-adsorbed peptides survive under UV irradiation among other unprotected species (storage step). Then, the MMT-adsorbed peptides can be released to the aqueous solution if the environment becomes more basic (releasing step), and these free peptides are ready for polymerization to polypeptides. Hence, a plausible prebiotic concentration–storage–release cycle of amino acids/peptides for further polypeptide synthesis is established. View Full-Text
Keywords: pH-dependent; adsorption; peptides; UV radiation protection; montmorillonite pH-dependent; adsorption; peptides; UV radiation protection; montmorillonite
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Lin, R.; Wang, Y.; Li, X.; Liu, Y.; Zhao, Y. pH-Dependent Adsorption of Peptides on Montmorillonite for Resisting UV Irradiation. Life 2020, 10, 45.

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