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Polymers 2012, 4(1), 710-740; doi:10.3390/polym4010710

Papain Catalyzed (co)Oligomerization of α-Amino Acids

Department of Polymer Chemistry & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, The Netherlands
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Received: 3 January 2012 / Revised: 6 February 2012 / Accepted: 8 February 2012 / Published: 29 February 2012
(This article belongs to the Special Issue Enzymes in Monomer and Polymer Synthesis)

Abstract

Four hydrophobic amino acids (Leu, Tyr, Phe, Trp) were oligomerized by the protease papain in homo-oligomerization, binary co-oligomerization and ternary co-oligomerization. After 24 h, solid polydisperse reaction products of the homo-oligomerization were obtained in yields ranging from 30–80% by weight. A DPavg was calculated based on MALDI-ToF MS results using the ion counts for the chains in the product. Based on the DPavg and the yield of the homo-oligomerization it was determined that the amino acids can be ranked according to reactivity in the order: Tyr > Leu > Phe > Trp. Thermal degradation of the homo-oligomers shows two degradation steps: at 178–239 °C and at 300–330 °C. All the products left a significant amount of char ranging from 18–57% by weight at 800 °C. Binary co-oligomers were obtained as a polydisperse precipitate with a compositional distribution of the chains. Both the compositional and chain length distribution are calculated from MALDI-ToF mass spectra. By comparing the amount of each amino acid present in the chains it was determined that the amino acids are incorporated with a preference: Leu > Tyr > Phe > Trp. Ternary co-oligomers were also obtained as a precipitate and analyzed by MALDI-ToF MS. The compositional distribution and the chain length distribution were calculated from the MALDI-ToF data. The quantity of every amino acid in the chains was determined. Also determined was the influence on the DPavg when the oligomers were compared with corresponding binary co-oligomers. From the combined results it was concluded that in the co-oligomerization of three amino acids the reactivity preference is Leu > Tyr > Phe > Trp. Thermal degradation of all the co-oligomers showed a weight loss of 2 wt% before the main oligomer degradation step at 300–325 °C.
Keywords: enzymatic oligomerization; papain; poly amino acids; co-oligomerization; MALDI-ToF MS; thermogravimetry enzymatic oligomerization; papain; poly amino acids; co-oligomerization; MALDI-ToF MS; thermogravimetry
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Schwab, L.W.; Kloosterman, W.M.J.; Konieczny, J.; Loos, K. Papain Catalyzed (co)Oligomerization of α-Amino Acids. Polymers 2012, 4, 710-740.

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