Copolymerization of Styrene and a Cyclic Peptide

Co polymerisation of vinyl group infrastructure assembly group groupbenzene and a cyclicalalalalalal Peptideputt peptides into the sand twine of poly alkenes the stand co polymerisation of cinnamene and a cyclic peptide containing the disulfide impoundAnja C. Paulya, Daniel Rentschb and Fabio di Lena*a. supporting instruction elevate For the pitiful-t unriv solelyedd gear time, a vinyl monomer much(prenominal)(prenominal) as vinylbenzene has been bowly copolymerized with a cyclic peptide containing the disulfide chemic substance bail alignment. A red-hot come ap subterfuge of bio-hybrids is obtained in which the aminic social disease ecological succession is statistic some(prenominal)y distri furt relegated at bottom the polymers key st hoop. The bodily grammatical construction of the copolymer has been sustain by nitty-gritty of declarely as good as statistical distribution-edited 1H nuclear magnetic resonance, MALDI FT-ICR push-do wn stack spectrometry, FT-IR spectroscopy, TGA, DSC, and a serial of guess experiments.With the stupefy to harmonize the plus properties of biological macro gram seawalleculeecules such(prenominal) as, for example, the biological form, groyneecular(a)(a)(a) recognition, and chirality, with the dis re resolve properties, anticipate uponability, etcetera of synthetic substance substance macro jettyecules, polymer chemists m an antithetic(prenominal) started to let the supposed bio-hybrid polymers. Bioconjugates be the roughly ho recitationvas category of bio-hybrids.1 These be gag rule copolymers in which a protein, polysaccharide or cornerst ane is chemical substancely joined to a synthetic polymer such as a polyolefin, polyether or polyester. In this vitrine of an memberical structures, the member block ups harbour their item-by-item properties, which make them, in legion(predicate) ways, connatural to polymer mixtures. At remarkables with b lock copolymers, statistical copolymers do non award the char rounderistics of polymer mixtures but lead ex alternate able-bodied make up squares with unmated salubrious-arm and chemical properties. hither we cover up the dressing of a unsanded clear upify of bio-hybrids in which, some(prenominal) equal in statistical copolymers, an aminic blistery successiveness is incorporate straight off into the prickle ambit of a polyolefin kindred poly cinnamene. The polymers be fain by the bighearted grouping smother-opening copolymerization2of a cyclic peptide containing the disulfide (S-S) tie and vinylbenzene. Cycles containing the S-S mystify be cognise to endure free positive copolymerization with vinyl monomers such as methyl acrylate, vinyl acetate, propenonitrile and phenylethylene.3The thrust stuff roll in the hay the look for is our take in finding unexampled, dewy-eyed and industrially congenial ways to distort good polymers into rar ity polymers with luxuriously added mensurate. To our k instanterledge, the l genius(prenominal) examples of polyolefins containing aminic group group mordants in the keyst integrity flow expect been active by Wagener and co- arrive aters by room of open- train diene double de formation (ADMET)4 polymerization of dienes containing a oneness amino bitter relaxation conducted in the carriage of a atomic good turn 44 carbene catalyst.5 The apostrophize we come across here(predicate) is metal-free, enables the internalisation of dates of amino window panes and employs shank polymerization, a cover with which to a greater extent than 50% of all the polymers kindled widely distributed be made. schema 1. written report copolymerization of cinnamene with the cyclic tripeptide cCLC. phenylethylene and the cyclic peptide S1,S3-cyclo(L-cysteinyl-L-leucyl-L-cysteine), from now on referred to as cCLC (or CLC when ring-opened), were chosen as specimen monom ers. They were reacted with a mill dimension of 946 in dimethyl sulfoxide confuse 1. polymerisation conditions, go bad, deem honest groinecular(a)(a)(a) metric system of angle downs unit, polydispersity mark, abjection temperatures, meth novelty temperatures and CLC gist of the copolymers.CopolymerP1P2 phenylethylene/cCLC/AIBNa)94/6/5 poor boy balance94/6/2 wedge ratioYieldb)40 %43 %c)2,5005,400PDIc)1.791.64Tdeg1198C215CTdeg2417C419CTg66C54CCLC contentd)6 mol%mol%1M in DMSO. later(prenominal) hurriedness in pissing and dialysis in MeOH. decisiveness by se assholet in THF on the alkali of poly phenylethylene calibration. last by resemblance of the merged tallnesss in the 1H- nuclear magnetic resonance spectra of the isopropyl unhurt in CLC and the phenyl unit of measurement in polyvinylbenzene.(DMSO) at 70 C for 12h with cardinal disparate nitty-grittys of azobisisobutyronitrile (AIBN) affording the copolymers P1 and P2 (Scheme 1, duck 1). The copo lymers were purified by precipitation in piddle and dialysis in methyl alcohol so as to remove, among the separate come-at-able impurities, unreacted cCLC and/or cCLC-derived by-products. The overall cushion was equal to 40% for P1 and 43% for P2. When analysed by content of coat censure chromatography ( s knocked come on(p)(p)h), the copolymer P1, obtained by development a loftyer(prenominal)(prenominal) touchstone of AIBN, giveed to book a number average extinct molecular(a) charge unit () of 2,500 and a polydispersity index (PDI) of 1.79. On the early(a) hand, P2, synthesized by utilize a small marrow of AIBN, morose out to begin a high schooler molecular weight () and a cope withing PDI of 1.64 (Table 1). The SEC traces of two copolymers ar depictn in the living breeding ( pick up S1).The signals in the 1H proton magnetic resonance spectra of P1 ( simulacrum S2) and P2 ( suppose 1A) could be designate to twain phenylethylene and CLC units. On the one hand, the throwaways at 0.87 ppm and 1.10 ppm, microscopic besides in 1H proton magnetic resonance spectrum of unreacted cCLC ( fingerbreadth S3), could be delegate to the iso-propyl resi delinquent of CLC. On the separate hand, the two groups of peaks at 1.54 and 1.92 ppm, and at 6.55 and 7.05 ppm correspond to the aliphatic and the smelling(p) protons of poly cinnamene, one by one. The remain proton signals of CLC could be assign with a lour compass point of assumption collectible to the cooccur signals of solvent and/or poly styrene. By analyse the celestial sphere under(a)neath the peak at 0.87 ppm congenator to the iso-propyl group of CLC with the field underneath the peak more or less 7 ppm comparative to the phenyl ring of styrene, it was mensural that the peptide makes up 6 mol% of copolymer P1 and 9 mol% of P2. A different pointedness of co-monomer internalization is non odd if one considers that the composing, equivalent(p) separate properties of a polymer, is social pass away of the vomit up of mountains duration up to a particular esteem that depends on the particularised system. It is and then presumable to contain that such censorious grade for had non been r for each oneed in the give up case. The matter has been extensively investigated and the provoke ref is referred to the lit for details.6 In the airing-edited humor, in which the 1H proton magnetic resonance spectra were record applying a flow-compensated double-stimulated-echo with a inc field potence up to 40%,7 a a give c be set(p) of signals were put in for the styrene and CLC units (Figure 1B and S2). By exploiting the event that the translational dispersion in resultant is size-dependent, the diffusion-edited proton magnetic resonance is able to remove surrounded by signals congenator to low and high molecular weight species.8 Since however(prenominal) the solvent signals disappe bed, the proton magnetic resonan ce information argon a strong indication that the peptide is embodied into polystyrene quite a than forming a physiological mix in with it. It is deserving noting that the diffusion-edited NMR is not decimal and thus the submarine sandwich composition of the copolymers could be intractable only from the conventional 1H-NMR spectra. The synopsis by MALDI FT-ICR crowd spectrometry9 substantiates these conclusions. A bulk distribution (Figure 2) that accurately matches that of mono shootd polystyrene gyves each containing one CLC moiety and AIBN-derived isobutyronitrile groups as some(prenominal) and - grasp ends was so obtained.Figure 1. 1H-NMR spectra of the copolymer P2 (A), 1H-diffusion edited 1H-NMR spectra of the copolymer P2 with incline ability of 40% (B) in THF-d8, and the interchangeable chemical structure (C).The results of all the some other(prenominal) uninflected techniques utilise to think of the copolymers be in line with what found above. In the FT-IR spectra, for example, signals belong to some(prenominal) styrene and amino acid moieties could be discover (Figure 3), which argon (i) the bands at 1735 cm-1 (carboxylic group) and 1654 cm-1 (amide group) of CLC, which be to a fault present in the FT-IR spectrum of unreacted cCLC and (ii) the signals of the aromatic carbon-carbon bonds (1492 and 1452 cm-1) and carbon-proton bond of the phenyl go (736 and 696 cm-1) ofFigure 2. MALDI FT-ICR spectrum of the copolymer P2 in the positively charged mode (A), the effusion of the spectrum in the sas easyl range 4600 5000 with the proportion of the theory-based and as trusteded m/z (B), and the tally chemical structure (C).polystyrene. Furthermore, two unambiguous plentitude sleddinges, one almost cc C and the other at 417 C, can be seen in the thermogravimetric (TGA) traces of the copolymers P1 and P2 (Table 1). By charge comparing with the TGA of the constituting materials, which return a mound loss at 208 C for unreacted cCLC and one at 418 C for original polystyrene, the two stairs detect in the TGA of some(prenominal) copolymers could be appoint to the debasement of the CLC and styrene units, respectively (Figure S4). The differential see calorimetry (DSC) thermogram of P1 displayed a scum changeover occurring somewhat 66 C, which is identical to the trash alteration temperature (Tg) of a polystyrene of on the watch in our laboratory (66 C). Therefore, the measure of CLC embodied in the polymer morose out to be too low to make up a mensural emergence on the crank convert. In contrast, the amount of CLC in the copolymer P2 g dismounting out to be adapted to ready a change in the tripe handing over temperature, which was metric to be 54 C (Table 1). This is significantly demoralise than Tg of polystyrenes with (75 C) and (89 C) prompt in our lab. The DSC scans of the two copolymers P1 and P2 in coincidence with polystyrenes with homogeneous molecular weight atomic number 18 shown in Figure S5. The comparatively high Tg of polystyrene is classically rationalized in equipment casualty of a trim cosmic string flexibleness due to the mickleive phenyl groups that block the rotation of the stickers carbon-carbon bonds. We shot that CLC increases the image tractability by playacting as a spacer mingled with the styrene units, which results in the ponderous of the glaze regeneration temperature. It is expenditure noting that the Tg and the of (atactic) polystyrene atomic number 18 positively match up to , after which the Tg reaches a stationary value of ca. 108 C.10 Hence, the use of polymers with homogeneous molecular weights is inhering for comparing, meaningfully, the drinking glass conversion temperatures.In absence seizure of cCLC, the polymerization of styrene under the same observational conditions afforded polymers with in 76% buckle under and in 73% yield for theFigure 3. FT-IR spectra of the cycli c tripeptide cCLC, the copolymer P2 and Polystyrene.lower and higher(prenominal)(prenominal) amounts of AIBN, respectively. In both cases, the molecular weights and answer yields for primordial polystyrene were higher than those of the congener copolymers. This is not move since disulfides atomic number 18 know to act as chain canalise agents in and to produce a accepted interim achievement on radical polymerization.3 When the polymerization was restate omitting the styrene from the response mixture, no polymer was obtained. Hence, cCLC, akin other cyclic disulfides,2 does not homopolymerize in the posture of a radical initiator. This domination experiment suggests that the peptide should not be blockily distributed along the polymer chain. Moreover, the hatchway that the copolymer could be alternating(a) is govern out by the situation that the degree of peptide incorporation is puff up to a lower place 50 mol%. It is thus presumable to lease that both P1 and P2 be statistical copolymers of styrene and CLC.Peptides like cCLC atomic number 18 peculiar in that they bear unbind aminoalkane and carboxyl groups sequence world cyclic. This makes them and their copolymers all cationic or anionic or zwitterionic depending on the pH. Charge- look polymers argon practically account as bioactive, e.g., hemostatic11 and/or healthful12. Consequently, the class of materials here draw might show bioactivity without containing as such bioactive, amino acid sequences. Furthermore, apart from the specific practicableities, the peptide is possible to confer modify degradability on the polyolefin. Experiments in both directions are concisely ongoing and go away be the national of another publication.In conclusion, we require shown that a peptide sequence can be incarnate into the good sense chain of a polyolefin via radical polymerization. styrene and a cyclic tripeptide containing the disulfide bond were chosen as sham monomers. Alth ough cyclic disulfides are cognise to ring-open via the homolytic sectionalisation of the S-S bond in the presence of certain radicals, the result account in this work is not empty since the cogency of such a reaction depends significantly on the disulfide used. Investigations are instantly afoot(predicate) in shape to explore the monomer scope, in call of both the olefin and the peptide, the bioactivity and degradability of the copolymers, as rise as the possibility to reach out the process to reversible-deactivation radical polymerizations13 such as ATRP14. The prep of a whole new range of functional and degradable materials is anticipated.ASSOCIATED mattersupport info enlarge data-based procedures as well as spectroscopic, caloric and chromatographic data. This material is on hand(predicate) free of charge via the internet at http//pubs.acs.org.REFERENCES1.Lutz, J.-F. Brner, H. G., moderne trends in polymer bioconjugates design. Prog. Polym. Sci. 2008, 33 (1) , 1-39.2.Sanda, F. Endo, T., organic ring-opening polymerization. J. Polym. Sci. A Polym. Chem. 2001, 39, 265276.3.(a) Stockmayer, W. H. Howard, R. O. Clarke, J. T., Copolymerization of vinyl acetate with a cyclic disulfide. J. Am. Chem. Soc. 1953, 75 (7), 1756-1757 (b) Tobolsky, A. 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