Prebiotic Alternatives to Proteins: Structure and Function of Hyperbranched Polyesters
- 417 Downloads
Proteins are responsible multiple biological functions, such as ligand binding, catalysis, and ion channeling. This functionality is enabled by proteins’ three-dimensional structures that require long polypeptides. Since plausibly prebiotic synthesis of functional polypeptides has proven challenging in the laboratory, we propose that these functions may have been initially performed by alternative macromolecular constructs, namely hyperbranched polymers (HBPs), during early stages of chemical evolution. HBPs can be straightforwardly synthesized in one-pot processes, possess globular structures determined by their architecture as opposed to folding in proteins, and have documented ligand binding and catalytic properties. Our initial study focuses on glycerol-citric acid HBPs synthesized via moderate heating in the dry state. The polymerization products consisted of a mixture of isomeric structures of varying molar mass as evidenced by NMR, mass spectrometry and size-exclusion chromatography. Addition of divalent cations during polymerization resulted in increased incorporation of citric acid into the HBPs and the possible formation of cation-oligomer complexes. The chelating properties of citric acid govern the makeup of the resulting polymer, turning the polymerization system into a rudimentary smart material.
KeywordsHyperbranched polymer Polyester Smart material Protein Size exclusion chromatography
We thank Dr. Leslie Gelbaum for his help in the design of NMR experiments and Prof. Nicholas Hud for helpful discussions. This work is supported by Simons Foundation Collaboration on the Origin of Life Fellowship SCOL 292864 (I.M.) and Investigator Award SCOL 302497 (M.P.C., J.P.D.), as well as the NASA Astrobiology Institute award to the Carnegie Institution for Science (I.M., G.D.C.) and The Goddard Center for Astrobiology (M.P.C., J.P.D.).
- Berg JM, Tymoczko JL, Stryer L (2012) Biochemistry, 7th edn. W.H. Freeman, New YorkGoogle Scholar
- Fahnestock S, Rich A (1971) Ribosome-catalyzed polyester formation. Science 173(3994):340–343. doi: 10.1126/science.173.3994.340
- Fréchet JMJ, Hawker CJ (1995) Hyperbranched polyphenylene and hyperbranched polyesters: new soluble, three-dimensional, reactive polymers. React Funct Polym 26:127–136. doi: 10.1016/1381-5148(95)00010-D, Proceedings of the 6th International Conference on Polymer Supported Reactions in Organic ChemistryCrossRefGoogle Scholar
- Lahav N, White D, Chang S (1978) Peptide formation in the prebiotic era: thermal condensation of glycine in fluctuating clay environments. Science 201(4350):67–69. doi: 10.1126/science.663639
- Mamajanov I, MacDonald PJ, Ying J, Duncanson DM, Dowdy GR, Walker CA, Engelhart AE, Fernández FM, Grover MA, Hud NV, Schork FJ (2014) Ester formation and hydrolysis during wet–dry cycles: generation of far-from-equilibrium polymers in a model prebiotic reaction. Macromolecules 47:1334–1343. doi: 10.1021/ma402256d CrossRefGoogle Scholar
- Martin RB (1998) Free energies and equilibria of peptide bond hydrolysis and formation. Biopolymers 45:351–353. doi: 10.1002/(SICI)1097-0282(19980415)45:5<351::AID-BIP3>3.0.CO;2-K CrossRefGoogle Scholar
- Miller SL, Urey HC (1959) Organic Compound Synthes on the Primitive Eart Several questions about the origin of life have been answered, but much remains to be studied. Science 130(3370):245–251. doi: 10.1126/science.130.3370.245
- Prabaharan M, Grailer JJ, Pilla S, Steeber DA, Gong S (2009) Folate-conjugated amphiphilic hyperbranched block copolymers based on Boltorn® H40, poly(l-lactide) and poly(ethylene glycol) for tumor-targeted drug delivery. Biomaterials 30:3009–3019. doi: 10.1016/j.biomaterials.2009.02.011 PubMedCrossRefGoogle Scholar
- Tasaka F, Ohya Y, Ouchi T (2001) One-pot synthesis of novel branched polylactide through the copolymerization of lactide with mevalonolactone. Macromol Rapid Commun 22:820–824. doi: 10.1002/1521-3927(20010701)22:11<820::AID-MARC820>3.0.CO;2-7 CrossRefGoogle Scholar
- Weimann BJ, Lohrmann R, Orgel LE, Schneider-Bernloehr H, Sulston JE (1968) Template-directed synthesis with adenosine-5′-phosphorimidazolide. Science 161(3839):387. doi: 10.1126/science.161.3839.387