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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; in revised form: 6 February 2012 / Accepted: 8 February 2012 / Published: 29 February 2012
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
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Schwab, L.W.; Kloosterman, W.M.J.; Konieczny, J.; Loos, K. Papain Catalyzed (co)Oligomerization of α-Amino Acids. Polymers 2012, 4, 710-740.
Schwab LW, Kloosterman WMJ, Konieczny J, Loos K. Papain Catalyzed (co)Oligomerization of α-Amino Acids. Polymers. 2012; 4(1):710-740.
Schwab, Leendert W.; Kloosterman, Wouter M. J.; Konieczny, Jakob; Loos, Katja. 2012. "Papain Catalyzed (co)Oligomerization of α-Amino Acids." Polymers 4, no. 1: 710-740.