Probing the Folding of Peptide–Polymer Conjugates Using the π-Dimerization of Viologen End-Groups

Abstract

The synthesis of a foldable viologen-functionalized peptide–polymer conjugate is presented. The ABA-type triblock conjugate with a PEG polymer was capped with a FHFHF pentapeptide sequence and further modified with a viologen building block at both chain ends. The pH-responsive peptide domains fold into an intermediate structure inducing close proximity of the viologen units, which upon a reduction step form π-dimers of the radical cation. Overall the intramolecular folding and intermolecular self-assembly process leads to the formation of supramolecular nanorods. Mixing of viologen-peptide–polymer conjugates with unfunctionalized conjugates leads to crosslinking of the nanorods and hydrogels with a tunable content of viologen end groups. π-Dimerization in the gels induces a deep purple color, which is used as an optical probe to monitor the diffusion of molecular oxygen through the hydrogel matrix.

Key words

supramolecular materials - stimuli-responsive polymers - electrochromism - peptide conjugation - hydrogel

Supporting Information

Supporting information for this article is available online at https://doi.org/10.1055/s-0040-1710343.

• References

• 1 Michaelis L. Biochem. Z. 1932; 250: 564
• 2 Michaelis L, Hill ES. J. Gen. Physiol. 1933; 16: 859
• 3 Striepe L, Baumgartner T. Chem. Eur. J. 2017; 23: 16924
• 4 Ding J, Zheng C, Wang L, Lu C, Zhang B, Chen Y, Li M, Zhai G, Zhuang X. J. Mater. Chem. A 2019; 7: 23337
• 5 Senn DR, Carr PW, Klatt LN. Anal. Biochem. 1976; 75: 464
• 6 Kameyama A, Nambu Y, Endo T, Shinkai S. J. Chem. Soc. D 1992; 1058
• 7 Thorneley RN. F. Biochim. Biophys. Acta, Bioenerg. 1974; 333: 487
• 8 Bird CL, Kuhn AT. Chem. Soc. Rev. 1981; 10: 49
• 9 Kirch M, Lehn J-M, Sauvage J-P. Helv. Chim. Acta 1979; 62: 1345
• 10 Borgarello E, Kiwi J, Pelizzetti E, Visca M, Grätzel M. Nature 1981; 289: 158
• 11 Ebbesen TW, Levey G, Patterson LK. Nature 1982; 298: 545
• 12 Janoschka T, Martin N, Martin U, Friebe C, Morgenstern S, Hiller H, Hager MD, Schubert US. Nature 2015; 527: 78
• 13 Janoschka T, Martin N, Hager MD, Schubert US. Angew. Chem. Int. Ed. 2016; 55: 14427
• 14 Hu B, DeBruler C, Rhodes Z, Liu TL. J. Am. Chem. Soc. 2017; 139: 1207
• 15 Wheeler DR, Nichols J, Hansen D, Andrus M, Choi S, Watt GD. J. Electrochem. Soc. 2009; 156: B1201
• 16 Zhu H, Song N, Lv H, Hill CL, Lian T. J. Am. Chem. Soc. 2012; 134: 11701
• 17 Prier CK, Rankic DA, MacMillan DW. C. Chem. Rev. 2013; 113: 5322
• 18 Hwang E, Seo S, Bak S, Lee H, Min M, Lee H. Adv. Mater. 2014; 26: 5129
• 19 Beneduci A, Cospito S, La Deda M, Veltri L, Chidichimo G. Nat. Commun. 2014; 5: 3105
• 20 Boettcher SW, Spurgeon JM, Putnam MC. , et al. Science 2010; 327: 185
• 21 Balzani V, Credi A, Raymo FM, Stoddart JF. Angew. Chem. Int. Ed. 2000; 39: 3348
• 22 Kim H-J, Heo J, Jeon WS, Lee E, Kim J, Sakamoto S, Yamaguchi K, Kim K. Angew. Chem. Int. Ed. 2001; 40: 1526
• 23 Ong W, Gómez-Kaifer M, Kaifer AE. Org. Lett. 2002; 4: 1791
• 24 Badjic JD, Balzani V, Credi A, Silvi S, Stoddart JF. Science 2004; 303: 1845
• 25 Moon K, Grindstaff J, Sobransingh D, Kaifer AE. Angew. Chem. Int. Ed. 2004; 43: 5496
• 26 Correia HD, Chowdhury S, Ramos AP, Guy L, Demets GJ. F, Bucher C. Polym. Int. 2019; 68: 572
• 27 Zhou C, Tian J, Wang J-L, Zhang D-W, Zhao X, Liu Y, Li Z-T. Polym. Chem. 2014; 5: 341
• 28 Kahlfuss C, Métay E, Duclos M-C, Lemaire M, Milet A, Saint-Aman E, Bucher C. Chem. Eur. J. 2015; 21: 2090
• 29 Zhan T-G, Zhou T-Y, Lin F, Zhang L, Zhou C, Qi Q-Y, Li Z-T, Zhao X. Org. Chem. Front. 2016; 3: 1635
• 30 Greene AF, Danielson MK, Delawder AO, Liles KP, Li X, Natraj A, Wellen A, Barnes JC. Chem. Mater. 2017; 29: 9498
• 31 Liles KP, Greene AF, Danielson MK, Colley ND, Wellen A, Fisher JM, Barnes JC. Macromol. Rapid Commun. 2018; 39: 1700781
• 32 Kahlfuss C, Gibaud T, Denis-Quanquin S, Chowdhury S, Royal G, Chevallier F, Saint-Aman E, Bucher C. Chem. Eur. J. 2018; 24: 13009
• 33 van Hest JC. M, Tirrell DA. Chem. Commun. 2001; 1897
• 34 Klok HA, Lecommandoux S. Adv. Mater. 2001; 13: 1217
• 35 Vandermeulen GW. M, Klok H-A. Macromol. Biosci. 2004; 4: 383
• 36 Börner HG, Schlaad H. Soft Mater. 2007; 3: 394
• 37 Börner HG. Prog. Polym. Sci. 2009; 34: 811
• 38 Otter R, Klinker K, Spitzer D, Schinnerer M, Barz M, Besenius P. Chem. Commun. 2018; 54: 401
• 39 Otter R, Henke NA, Berac C, Bauer T, Barz M, Seiffert S, Besenius P. Macromol. Rapid Commun. 2018; 39: 1800459 Characterization of C2 ¹H NMR (400 MHz, DMSO- d₆ , 298 K): δ/ppm: 14.14 (s(br), 8H, NH₂ ^{+ His}), 9.04–8.92 (m, 4H, CH ^His), 8.48 (d, 2H, α-NH), 8.35 (d, J = 8.2 Hz, 2H, α-NH), 8.21 (d, J = 7.5 Hz, 2H, α-NH), 8.18–8.08 (m, 4H, α-NH/NH ^Ahx), 8.03 (d, J = 7.4 Hz, 2H, α-NH), 7.99 (t, J = 5.6 Hz, 2H, NH ^Gly), 7.90 (t, J = 5.5 Hz, 2H, PEG-NH), 7.48–7.08 (m, 34H, CH ^His /CH ^Phe), 4.66–4.34 (m, 10H, α-CH), 3.65 (d, J = 6.0 Hz, 4H, CH₂ ^Gly), 3.50 (s (br), 264H, PEG–CH2), 3.39 (t, J = 5.8 Hz, 4H, PEGCH ₂CH₂NH), 3.20 (q, J = 5.8 Hz, 4H, PEGCH₂CH₂ NH), 3.11–2.70 (m, 24H, CH₂ ^His /CH₂ ^Phe /CH₂ ^Ahx), 2.10 (t, J = 7.5 Hz, 4H, CH₂ ^Ahx), 1.74 (s, 6H, NHCOCH₃ ) 1.50–1.40 (m, 4H, CH₂ ^Ahx), 1.36–1.26 (m, 4H, CH₂ ^Ahx), 1.19–1.10 (m, 4H, CH₂ ^Ahx). MALDI-MS (DIT + KTFA, DCM/MeOH = 1/1) (m/z): Calculated for [C₂₃₄H₃₉₁N₂₄O₈₃]⁺ : 4868.8, found: 4867.6; calculated for [C₂₃₄H_39oN₂₄O₈₃Na]⁺ : 4890.8, found: 4890.0
• 40 Reczek JJ, Rebolini E, Urbach AR. J. Org. Chem. 2010; 75: 2111
• 41 Ogawa M, Balan B, Ajayakumar G, Masaoka S, Kraatz HB, Muramatsu M, Ito S, Nagasawa Y, Miyasaka H, Sakai K. Dalton Trans. 2010; 39: 4421
• 42 Synthesis of C1: 5 (295 mg, 49 µmol, 1 eq.) was dissolved in 2 mL DMF in a flask equipped with a stir bar. 2 (161.7 mg, 386 µmol, 8 eq.), PyBOP (100.9 mg, 193 mmol, 4 eq.), HOBt (26.1 mg, 193 µmol, 4 eq.), and DIPEA (53 µL, 290 µmol, 6 eq.) were added to the solution. The mixture was stirred for 6 hours at room temperature. Then PyBOP (50.4 mg, 96 mmol, 2 eq.) and HOBt (13 mg, 96 mmol, 2 eq.) were added to the yellow solution, which was stirred for 18 hours. Afterwards a mixture of TFA (2 mL), water (0.1 mL), and triisopropylsilane (0.1 mL) was added. The solution was stirred for 45 min at room temperature. After the deprotection, all volatiles were removed through reduced pressure and the solid was co-distilled with toluene. The residue was separated via size exclusion chromatography (Sephadex® LH 20, MeOH). Yield: 280 mg (47 µmol, 96%) slightly yellow sticky solid. ¹ H-NMR (400 MHz, DMSO- d₆ , 298 K): δ/ppm: 9.43–9.38 (m, 8H, H2/H6 ^Viologen /H2′/H6′ ^Viologen), 8.81–8.77 (m, 8H, H3/H5 ^Viologen/H3′/H5′ ^Viologen), 8.50–7.97 (m, 20H, CH ^His /α-NH), 7.91 (t, J = 5.7 Hz, 2H, α-NH ^PEG), 7.45–7.11 (m, 34H, CH ^His /CH ^Phe), 4.90 (t, J = 6.4 Hz, 4H, N ⁺ CH₂ CH₂), 4.73 (q, J = 7.3 Hz, 4H, N ⁺ CH₂ CH₃), 4.66–4.41 (m, 10H, α-CH), 3.66 (d, J = 5.9 Hz, 4H, CH₂ ^Gly), 3.51 (s(br), 264H, PEG-CH ₂), 3.40 (t, J = 5.8 Hz, 4H, PEGCH ₂CH₂NH), 3.21 (q, J = 5.8 Hz, 4H, PEGCH₂CH₂ NH), 3.11–2.74 (m, 28H, CH₂ ^Ahx /CH₂ ^Phe /CH₂ ^His), 2.10 (t, J = 7.5 Hz, 4H, CH₂ ^Ahx), 2.00-1.92 (m, 4H, CH₂ ^Ahx), 1.60 (t, J = 7.3 Hz, 6H, N ⁺ CH₂CH₃ ), 1.47–1.42 (m, 4H, CH₂ ^Ahx), 1.32–1.23 (m, 12H, CH₂ ^Ahx), 1.18–1.11 (m, 4H, CH₂ ^Ahx), 1.02–0.94 (m, 4H, CH₂ ^Ahx).
• 43 Otter R, Berac CM, Seiffert S, Besenius P. Eur. Polym. J. 2019; 110: 90
• 44 Iehl J, Frasconi M, de Rouville HP. J, Renaud N, Dyar SM, Strutt NL, Carmieli R, Wasielewski MR, Ratner MA, Nierengarten JF, Stoddart JF. Chem. Sci. 2013; 4: 1462
• 45 Wadhwa K, Nuryyeva S, Fahrenbach AC, Elhabiri M, Platas-Iglesias C, Trabolsi A. J. Mater. Chem. C 2013; 1: 2302
• 46 Iordache A, Kannappan R, Métay E, Duclos M-C, Pellet-Rostaing S, Lemaire M, Milet A, Saint-Aman E, Bucher C. Org. Biomol. Chem. 2013; 11: 4383
• 47 Ahlers P, Frisch H, Holm R, Spitzer D, Barz M, Besenius P. Macromol. Biosci. 2017; 17: 1700111
• 48 Farrington JA, Ebert M, Land EJ, Fletcher K. Biochim. Biophys. Acta, Bioenerg. 1973; 314: 372
• 49 Nanni EJ, Angelis CT, Dickson J, Sawyer DT. J. Am. Chem. Soc. 1981; 103: 4268
• 50 Sweetser PB. Anal. Chem. 1967; 39: 979
• 51 Gong Y-N, Lu T-B. Chem. Commun. 2013; 49: 7711
• 52 Tong J, Guo X, Jia L, Tian X. Mater. Lett. 2015; 158: 255
• 53 Shirman E, Ustinov A, Ben-Shitrit N, Weissman H, Iron MA, Cohen R, Rybtchinski B. J. Phys. Chem. B 2008; 112: 8855
• 54 Baram J, Shirman E, Ben-Shitrit N, Ustinov A, Weissman H, Pinkas I, Wolf SG, Rybtchinski B. J. Am. Chem. Soc. 2008; 130: 14966
• 55 Schmidt D, Bialas D, Würthner F. Angew. Chem. Int. Ed. 2015; 54: 3611
• 56 Leira-Iglesias J, Sorrenti A, Sato A, Dunne PA, Hermans TM. Chem. Commun. 2016; 52: 9009
• 57 Leira-Iglesias J, Tassoni A, Adachi T, Stich M, Hermans TM. Nat. Nanotechnol. 2018; 13: 1021