Abstract
The helix–coil transformations of block copolymers composed of poly(γ-benzyl-L-glutamate) (PBLG) and polystyrene (PS), in which PS was attached to either the N terminus (PBLGn-N-PSm) or the C terminus (PSn-C-PBLGm) of PBLG, were investigated in trifluoroacetic acid (TFA)–chloroform mixtures with TFA concentrations in the range of 0.7–10 vol%. The helical content (fH) estimated from 1H nuclear magnetic resonance measurements indicated that the PBLG segment in PBLG55-N-PS160 underwent a gradual helix–coil transformation from fH=1 to fH=0.75 over the range of 3.6–5.7 vol% TFA and then a drastic transformation to fH=0 at 9.5 vol% TFA, in a manner similar to that of the PBLG55 homopolymer. In PS120-C-PBLG55, the helical deformation of the PBLG segment was observed by adding a very small amount of TFA (0.7–3.6 vol%), followed by gradual and drastic transformations at higher TFA concentrations. The results indicate that the conformational stability of the C terminus in a PBLG chain differs from that of the N terminus. Transformations of PBLG/PS block copolymers with various molecular weights and compositions were also studied.
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References
Klok, H.- A. Peptide/protein-synthetic polymer conjugates: quo vadis. Macromolecules 42, 7990–8000 (2009).
Lecommandoux, S., Klok, H.- A. & Schlaad, H. in Block Copolymers in Nanoscience (ed. Lazzari, M., Liu, G., & Lecommandoux, S.) Ch. 6, 117–150 (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2006).
Gallot, B. Comb-like and block liquid crystalline polymers for biological applications. Prog. Polym. Sci. 21, 1035–1088 (1996).
Ding, W., Lin, S., Lin, J. & Zhang, L. Effect of chain conformational change on micelle structures: experimental studies and molecular dynamics. J. Phys. Chem. B 112, 776–783 (2008).
Rodríguez-Hernández, J. & Lecommandoux, S. Reversible inside-out micellization of pH-responsive and water-soluble vesicles based on polypeptide diblock copolymers. J. Am. Chem. Soc. 127, 2026–2027 (2005).
Klok, H.- A., Langenwalter, J. F. & Lecommandoux, S. Self-assembly of peptide-based diblock oligomers. Macromolecules 33, 7819–7826 (2000).
Lecommandoux, S., Achard, M.- F., Langenwalter, J. F. & Klok, H.- A. Self-assembly of rod-coil diblock oligomers based on α-helical peptides. Macromolecules 34, 9100–9111 (2001).
Doig, A. J. Recent advances in helix-coil theory. Biophys. Chem. 101–102, 281–293 (2002).
Cammas, S., Harada, A., Nagasaki, Y. & Kataoka, K. Poly(ethylene oxide-co-β-benzyl L-aspartate) block copolymers: influence of the poly(ethylene oxide) block on the conformationof the poly(β-benzyl L-aspartate) segment in organic solvents. Macromolecules 29, 3227–3231 (1996).
Harada, A., Cammas, S. & Kataoka, K. Stabilized α-helix structure of poly(L-lysine)-block-poly(ethylene glycol) in aqueous medium through supramolecular assembly. Macromolecules 29, 6183–6188 (1996).
Pechar, M., Kopeèková, P., Joss, L. & Kopeèek, J. Associative diblock copolymers of poly(ethylene glycol) and coiled-coil peptides. Macromol. Biosci. 2, 199–206 (2002).
Vandermeulen, G. W. M., Tziatzios, C. & Klok, H.- A. Reversible self-organization of poly(ethylene glycol)-based hybrid block copolymers mediated by a de novo four-stranded α-helical coiled coil motif. Macromolecules 36, 4107–4114 (2003).
Hamley, I. W., Ansari, I. A., Castelletto, V., Nuhn, H., Rösler, A. & Klok, H.- A. Solution self-assembly of hybrid block copolymers containing poly(ethylene glycol) and amphiphilic β-strand peptide sequences. Biomacromolecules 6, 1310–1315 (2005).
Kugo, K., Ohji, A., Uno, T. & Nishino, J. Synthesis and conformations of A-B-A tri-block copolymers with hydrophobic poly(γ-benzyl L-glutamate) and hydrophilic poly(ethylene oxide). Polym. J. 19, 375–381 (1987).
Itoh, T., Iwai, T., Ihara, E. & Inoue, K. Conformational transformation of poly(γ-phenetyl-L-aspartate) in block copolymer with polystyrene in 1,1,2,2-tetrachloroethane. Polym. J. 39, 853–860 (2007).
Steigman, J., Verdini, A. S., Montagner, C. & Strasorier, L. Protonation of peptides. II. Protonation of an amide and of a diamide in dichloroacetic acid, and the behavior of poly(γ-benzyl-L-glutamate) in dichloroacetic acid and in some mixed solvents. J. Am. Chem. Soc. 91, 1829–1836 (1969).
Markley, J. L., Meadows, D. H. & Jardetzky, O. Nuclear magnetic resonance studies of helix-coil transitions in polyamino acids. J. Mol. Biol. 27, 25–40 (1967).
Bradbury, E. M., Crane-Robinson, C., Goldman, H. & Rattle, H. W. E. Proton magnetic resonance and the helix–coil transition. Nature 217, 812–816 (1968).
Bradbury, J. H. & Fenn, M. D. Helix to coil transition in poly-L-amino acids. II. N.M.R. study of model compounds and poly-γ-benzyl-L-glutamate. Aust. J. Chem. 22, 357–371 (1969).
Bradbury, E. M., Crane-Robinson, C. & Rattle, H. W. E. High resolution N.M.R. studies of poly-γ-benzyl-L-glutamate: effect of polydispersity and molecular weight. Polymer 11, 277–286 (1970).
Nagayama, K. & Wada, A. 220 MHz PMR of monodisperse (PBLG) at the helix—coil transition region. Chem. Phys. Lett. 16, 50–51 (1972).
Crespo, J. S., Lecommandoux, S., Borsali, R., Klok, H.- A. & Soldi, V. Small-angle neutron scattering from diblock copolymer poly(styrene-d8)-b-poly(γ-benzyl L-glutamate) solutions: rod-coil to coil-coil transition. Macromolecules 36, 1253–1256 (2003).
Tian, H. Y., Deng, C., Chen, X. S. & Jing, X. B. Biodegradable cationic PEG–PEI–PBLG hyperbranched block copolymer: synthesis and micelle characterization. Biomaterials 26, 4209–4217 (2005).
Daly, W. H. & Poche, D. The preparation of N-carboxyanhydrides of α-amino acids using bis(trichloromethyl)carbonate. Tetrahedron Lett. 29, 5859–5862 (1988).
Matyjaszewski, K. & Xia, J. Atom transfer radical polymerization. Chem. Rev. 101, 2921–2990 (2001).
Ullman, R. On the controversy over “fast” and “slow” helix-coil transition rates in polypeptides. Biopolymers (Peptide Science) 9, 471–483 (1970).
Aurora, R. & Rose, G. D. Helix capping. Protein Sci. 7, 21–38 (1998).
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We thank the Venture Business Laboratory of Ehime University for conducting the NMR measurements.
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Itoh, T., Hatanaka, T., Ihara, E. et al. Helix–coil transformation of poly(γ-benzyl-L-glutamate) with polystyrene attached to the N or C terminus in trifluoroacetic acid–chloroform mixtures. Polym J 44, 189–194 (2012). https://doi.org/10.1038/pj.2011.113
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DOI: https://doi.org/10.1038/pj.2011.113
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