Papain Catalyzed (co)Oligomerization of α-Amino Acids

Polymers

Leendert W. Schwab¹  Wouter M. J. Kloosterman¹  Jakob Konieczny¹ 

[1] Department of Polymer Chemistry & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen 9747 AG, The Netherlands;

关键词: enzymatic oligomerization;    papain;    poly amino acids;    co-oligomerization;    MALDI-ToF MS;    thermogravimetry;   

DOI  :  10.3390/polym4010710

来源: mdpi

【 摘 要 】

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 DP_avg was calculated based on MALDI-ToF MS results using the ion counts for the chains in the product. Based on the DP_avg 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 DP_avg 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.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland.