Polypeptide

Polypeptide block copolymers prepared by transition metal-mediated NCA polymerization are well defined, with the sequence and composition of cake segments controlled past order and quantity of monomer added to initiating species, respectively.

From: Polymer Science: A Comprehensive Reference , 2012

Corrosion inhibitors

Johannes Fink , in Petroleum Engineer's Guide to Oil Field Chemicals and Fluids (Third Edition), 2021

Polypeptides

Polypeptides take been under consideration as corrosion inhibitors considering of environmental concerns [ 55]. Poly(aspartate) is the most efficient corrosion inhibitor known among the polypeptides [56]. The molecular weight (1-22   kDa) does not affect the efficiency, instead both loftier calcium ion and high pH raise the effectiveness. The performance is especially good in batch treatment tests.

In another study, poly(aspartic acid) was examined as a corrosion inhibitor for steel equally a function of pH and temperature [57]. At low to neutral pH values, poly(aspartic acid) increases the corrosion charge per unit of steel. At pH values above x, poly(aspartic acid) is a reasonably robust corrosion inhibitor.

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Corrosion Inhibitors

Johannes Karl Fink , in Petroleum Engineer'due south Guide to Oil Field Chemicals and Fluids, 2012

Polypeptides

Polypeptides accept been under consideration as corrosion inhibitors considering of their ecology acceptability ( Obeyesekere et al., 2001). Polyaspartate is the most efficient corrosion inhibitor known among the polypeptides (McMahon and Harrop, 1995). Its molecular weight (1–22 kDalton) does non bear upon its efficiency, but both high calcium ion concentration and high pH heighten the effectiveness. The performance was particularly skilful in batch treatment tests.

In another study, polyaspartic acid was examined as a corrosion inhibitor for steel over a range of pHs and temperatures (Silverman et al., 1995). At low to neutral pH values, it increases the corrosion rate of steel, simply at pH values above 10, polyaspartic acid is a reasonably robust corrosion inhibitor.

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Scientific Fundamentals of Biotechnology

R.B. Hitchman , ... Fifty.A. Rex , in Comprehensive Biotechnology (Second Edition), 2011

A polypeptide consisting of amino acids. Each polypeptide consists of a concatenation of amino acids linked together by covalent (peptide) bonds. They are naturally occurring complex organic substances (egg albumen and meat) composed essentially of carbon, hydrogen, oxygen, and nitrogen, plus sulfur or phosphorus, which are so associated as to form submicroscopic bondage, spirals, or plates and to which are attached other atoms and groups of atoms in a variety of ways. In their biologically active states, proteins function every bit catalysts in metabolism and, to some extent, every bit structural elements of cells and tissues.

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Ring-Opening Polymerization and Special Polymerization Processes

T.J. Deming , in Polymer Science: A Comprehensive Reference, 2012

4.16.4.2 Mesogen-Functionalized Polypeptides

The polypeptide materials field has grown tremendously in recent years. However, a drawback of polypeptides has been the difficulty in using melt processing with these materials, since the arable H-bonds and consequent poor chain flexibility prevent melting earlier decomposition. Although solution-based methods allow processing of these materials for most applications, 84 cook processing, or even adequacy for thermal annealing, would profoundly aggrandize the utility of polypeptides.

Pioneering studies on thermotropic polypeptides were washed by Watanabe's group, where poly(glutamates) were derivatized either with long alkyl chains 85 or past end-on attachment of biphenyl mesogens (eqn [21]). 86 Polypeptides with short alkyl side chains were not thermotropic, even so side chains greater than 10 carbons long gave melting transitions from –26 to 54   °C. These samples formed cholesteric liquid crystalline phases above the melting transition, only formed layered structures at low temperatures driven by crystallization of the side chains. Furthermore, poly(γ-octadecyl-l-glutamate) was establish to form a columnar hexagonal stage at temperatures above 200   °C, where the rodlike helices make up the ii-dimensional (2d) lattice. 85 When biphenyl mesogens were attached terminate-on to poly(glutamate) side bondage by half-dozen carbon alkyl spacers, layered structures were observed in the crystalline and liquid crystalline states, followed past transition into a cholesteric construction at higher temperatures. 86 Like results were establish when mesogens were fastened end-on to poly(lysine) bondage. 87 In these examples, the liquid crystalline mesophases were dominated either by the side-concatenation grouping (layered structure) or past the rodlike nature of the polypeptide courage (hexagonal phase), just in no example was coexistence of both types of ordering observed.

[21]

Deming developed mesogen-functionalized polypeptides in which liquid crystalline ordering exists meantime with backbone ordering. To obtain this coexistence betwixt mesogen and main-chain ordering, 'side-on' mesogen 88 modification of the polypeptides was used to allow facile parallel orientation of mesogens and the peptide backbones. Since it is known that varying the length of flexible spacers connecting polymer backbones and mesogens affects the mesophase behavior of side-chain liquid crystalline polymers, 89 NCA monomers with spacers of iii, v, and 10 methylene units between the lysine side chains and the mesogens were prepared. The mesogen used for this study was a well-known 3-ring aromatic ester molecule, xc which was derivatized from a central carboxylic acrid grouping by ester coupling to attach linkers of 3, five, and 10 methylene units to enable attachment to l-lysine ( Scheme ix ). Mesogen-derivatized polypeptides were prepared by polymerization of the corresponding NCAs using (PMeiii)4Co initiator in THF solvent in high yield. 91 The polypeptides were soluble in THF and were found to adopt α-helical conformations in solution by CD and Fourier transform infrared (FTIR) spectroscopy. These polymers displayed an unusual thermotropic mesophase where both side-chain mesogens and polymer backbones are ordered and coexist in a nematic hexagonal structure.

Scheme 9. Preparation of side-on mesogen functionalized polylysines.

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Pace Polymerization

Erno Chiellini , Robert W. Lenz , in Comprehensive Polymer Science and Supplements, 1989

38.3.3 Polypeptides

Polypeptides analogous to cellulose derivatives (when suitably substituted on the functional groups of the amino acid residues) are able to requite rise to anisotropic melts with cholesteric structures. The first reported examples are represented by copolymers of γ- due north-alkyl-L-glutamates, every bit represented past ( seven ). 81 Depending upon the chemical composition, the prepared copolymers form mesophases susceptible of selectively reflecting the visible lite. The wavelength of reflected light increases, at any given copolymers limerick, with increasing temperature, coordinating to the behavior of cellulose derivative mesophases and lyotropic solutions of poly(γ-benzyl-50-glutamate). Such a behavior can be interpreted assuming that the ether-ester branches in cellulose derivatives and the alkyl substituents in copoly(γ-n-alkyl-50-glutamate)southward play the function of solvents in essentially concentrated solutions. 82

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Polymer Characterization

K. Saalwächter , H.West. Spiess , in Polymer Science: A Comprehensive Reference, 2012

2.07.3.4.four Self-assembly and dynamics of polypeptides

Polypeptides (macromolecules composed of amino acids) play a vital role of molecules designed for use in drug delivery or gene therapy and thus have been the subject of intensive studies. 72,73 These copolymers are produced commercially on an industrial calibration by using conventional α-amino-acid N-carboxyanhydrides (NCAs) ring-opening polymerization techniques. In addition, it is known that the superb operation of biological polypeptide-based materials such as hair or spiders' silk is due to a hierarchical superstructure with several length scales where structure control is exerted at every level of hierarchy. Their two nigh common local conformations, known as secondary structures, are the α-helix, stabilized by intramolecular hydrogen bonds, and the β-sheet, stabilized by intermolecular bonds. These secondary structures tin can be probed straight by solid-country NMR 74 and their packing tin can exist obtained by Ten-rays. In improver, the α-helical structure posts a permanent dipole moment along its courage, and tin be, therefore, classified equally type-A polymer in Stockmayer's classification. This dipole moment tin can be measured precisely using dielectric spectroscopy and can be used as a probe of the persistence length of the secondary structure, which is difficult to obtain by other methods. 75

For example, 'copolypeptides', with their inherent nanometer length calibration of phase separation, provide the means of manipulating both the type and persistence of peptide secondary structures. Specifically, partial annihilation of α-helical structural defects due to chain stretching induced chain folding of β-sheets in block copolypeptides with incommensurate dimensions as well equally destabilization of β-sheets in peptidic blocks having both secondary motifs were identified. 76 These effects should be taken into account when such peptides are considered for drug delivery. Polypeptide 'star polymers' with a large hydrocarbon core were found to have several unanticipated properties. 77 Start, with the assist of a polyphenylene core scaffold, it was shown that there is a singled-out modify in the peptide secondary structure from coil/β-canvass conformations to α-helices accompanied by an abrupt increase in the hydrodynamic radii. This alter in secondary construction and the consequences on the particles' diffusion, measured past confocal fluorescence correlation spectroscopy, can be crucial in the efficient pattern of multiple antigen peptides. Second, the majority studies revealed a strong upshot of the polyphenylene cadre on the peptide secondary motifs that could non be envisaged from their linear analogs. Conspicuously, the local conformation of the peptides is a primal parameter for understanding these systems and the concerted utilize of the different techniques provides considerable more data than using either one alone, Effigy 32 .

Figure 32. Assembly of a lamellar-forming polypeptide-curlicue diblock copolymer depicting the master techniques employed in their characterization. Small-angle 10-ray scattering (SAXS) is employed for the domain spacing, d thirteenC NMR and wide-bending 10-ray handful (WAXS) are employed to identify the type of the peptide secondary structure (α-helical in the schematic). WAXS is further employed to go the lateral self-assembly of α-helices within the polypeptide domain (a hexagonal lattice is indicated in the schematic). Dielectric spectroscopy (DS) and site-specific NMR techniques are employed for the dynamics. Furthermore, the almost intense DS procedure tin can provide the persistence length, ξ, of α-helical segments.

 Reproduced with permission from Floudas, G.; Spiess, H. W. Macromol. Rapid Commun. 2009, xxx, 278–298. 75 Copyright 2009, by John Wiley & Sons, Inc.

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Bionanotechnology

Jeremy J. Ramsden Jeremy J. Ramsden , in Nanotechnology (Second Edition), 2016

xi.1 The Structural Nature of Biomolecules

Polypeptides (PP) (proteins) are linear polymers of amino acids (H 2 N–CHR–COOH, where R (bonded to the central C) is a variable side concatenation ("balance") – there are 20 different natural ones. To polymerize them, water is eliminated betwixt –COOH and H 2 Northward– to class the peptide bail, hence there is a common courage (linked via the "peptide" bonds) with variable side bondage – short aliphatic groups, minor aromatic groups, carboxylate, amine, hydroxyl, etc. Template-directed synthesis with a very high yield is used in nature, with the templates being closely related to genes via the genetic lawmaking (triplets of nucleotide bases encode each amino acid). Afterward synthesis (polymerization), they fold, oft spontaneously, to a meaty structure according to a least-activeness principle (see Section 8.2.11). Typical natural proteins take 50–500 amino acids. Depending on their sequence, they adopt a definite remembered conformation (proteins acting every bit devices, rather than having a passive structural rôle, have two or more stable conformations) and can conduct out varied functions, ranging from essentially structural or scavenging to enzymes and motors. Some proteins (chosen glycoproteins) are branched with oligosaccharides (OS) fastened to certain residues.

Nucleic acids (NA) are polymerized from nucleotides constituted from a saccharide, a phosphate group, and a "base" derived from a purine or pyrimidine (aromatic heterocycle). The sugar and phosphate are polymerized by eliminating water to form a linear courage, with the bases playing the rôle of the residues in PP. At that place are 4 natural bases, abbreviated A, C, G, T (in DNA) and A, C, One thousand, U (in RNA). The bases pair preferentially: A with T (or U), via 2 hydrogen bonds, and C with G via three hydrogen bonds (complementary base-pairing, CBP). Linear polymers are linked via the sugar. Template-directed synthesis with a very high yield is used in nature to create the polymers. The templates are the genes (DNA), and operate according to the principle of CBP. During polymerization RNA spontaneously folds to a definite compact structure according to a to the lowest degree-action principle (run across Section 8.ii.11), in which base-pairing via hydrogen bonding is equivalent to the potential energy, and loop and hairpin formation is equivalent to the kinetic energy. DNA forms the famous double helix in which genetic information is stably stored in living cells and many viruses.

Polysaccharides (PS) and OS are linear or branched polymers of various sugar (cyclic oligoalcohol) monomers, linked via h2o elimination ("condensation") at whatever of the several hydroxyl groups. The problem of predicting their construction is non however solved. Polymerization is not templated (i.e. not under direct genetic control) and there is variability (to a degree that is only poorly characterized) in sequence and length of the PS establish fulfilling the same role in comparable organisms.

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Nanostructured Polymer Materials and Sparse Films

J.Y. Shu , T. Xu , in Polymer Science: A Comprehensive Reference, 2012

7.08.4.1 Polypeptides

Linear polypeptides have simple sequences typically composed of a unmarried amino acrid species and can be synthesized past the band-opening polymerization of Due north-carboxyanhydrides (NCA) of protected α-amino acids initiated by primary amino end-functionalized synthetic polymer macroinitiators, every bit shown in Effigy 7 (a). This method is the most direct and efficient fashion of obtaining loftier-molecular-weight homopolymer or BCP polypeptides. The evolution of transition metal-mediated NCA polymerizations eliminates significant competing termination and transfer steps and allows control over polypeptide chain length and composition. This polymerization mechanism is a living polymerization that gives a monomodal distribution with a low polydispersity index and allows for the formation of sequences far greater in length than SPPS, resulting in molecular weights greater than 100   000   thousand   mol−1. 3 Diblock copolypeptides synthesized by this method tin be designed to cocky-assemble into stimuli-responsive vesicles 61 or hydrogels for biomedical applications. 62 Though polypeptide-based conjugates can assemble into various structures, they are inherently express by their uncomplicated sequences, such that they volition never be able to arroyo the complexity and versatility produced by nature.

Figure 7. (a) Linear polypeptides synthesized past the ring-opening polymerization of N-carboxyanhydrides of protected α-amino acids initiated by principal amino terminate-functionalized synthetic polymer macroinitiators.

 Reproduced with permission. Copyright © 2006, Elsevier. (b) Short circuitous peptide sequences, typically less than fifty residues in length, prepared by solid-stage peptide synthesis. (c) Native chemical ligation used to fix larger peptides from ii shorter ones, requiring a C-final thioester balance on one peptide and an N-terminal cysteine on the other.

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Macromolecular Architectures and Soft Nano-Objects

H.G. Börner , J.F. Lutz , in Polymer Science: A Comprehensive Reference, 2012

half dozen.fifteen.1.ane Peptide Bioconjugation: From Amino Acids to Proteins

Polypeptides and proteins can be considered as the near versatile polymer platform that nature is applying. However, the broad spectrum of structural and functional diversity is realized by the combination of only 20 natural L-α-amino acids (AAs). These building blocks are assembled in linear polypeptide chains, linked by amide connectivities (peptide bond). Together with posttranslational modifications and processing, the AA sequence determines the well-defined third structure of proteins, leading to the institution of precisely adapted properties and functions.

The diverse class of polypeptides allows for the realization of, on the one mitt, high-performance structure materials, such as dragline spider silk, microtubules, or collagen fibers. On the other hand, (multi)functional molecules or molecular assemblies can be found, for example, necessary for biocatalysis (enzymes) or for the office of the allowed organisation (allowed globulins). Moreover, proteins participate in the storage and the directed transport of materials in biological systems and are essential components for the communication in complex biosystems in form of, for example, cell-surface markers, receptors, regulators, or hormones.

The functional and structural diversity of peptides and proteins appear highly highly-seasoned for materials science, if a rational transfer of such (bio)functions toward synthetic polymers can be accomplished. Therefore, the conjugation of constructed polymers to peptide-based segments is considered as a straightforward tool to integrate a wide spectrum of novel properties and (bio)-functions into established synthetic, polymeric materials. 12,14 A modest part of this, what might appear to exist possible, has been already demonstrated. Indeed, the command of structure germination processes in polymeric materials, the incorporation of metal-free catalytic activity, the establishment of biocompatibility, and, perchance most important, the generation of bioactivity could be accomplished past the well-defined conjugation of polymers to peptide-based segments.

Bioconjugates, combining synthetic polymers and polypeptides tin can be classified based on the type of biosegment. Thus the field of bioconjugates is subdivided into three different categories, following the construction principle of polypeptides from (i) the AA building blocks, (2) the oligo and polymeric peptides toward (3) the high-molecular-weight proteins. With increasing length of the monomer sequence (degree of polymerization), the chemical variety of the biosegments increases dramatically, enlarging the functional infinite. This makes the realization of more complex functions and highly purpose-divers properties possible.

The lowest level in complexity and functionality results from the incorporation of single AA in synthetic polymers. Oftentimes, one AA moiety is attached per repeat unit of the synthetic polymer, resulting in conjugates with a synthetic polymer backbone and pendent AA side chains. In these conjugates, the complex function of proteins and polypeptides is strongly reduced to the simple chemical functionalities of the AAs. However, the compatible chirality of the AAs and the hydrophobic–hydrophilic remainder of the AA moieties are inherently present in the macromolecule. Particularly, in aqueous solutions interesting effects tin can exist observed, which are clearly across those of classical synthetic polymers. For example, Schlaad and co-workers demonstrated that the nearly quantitative zipper of cysteine to each repeat unit of measurement of poly(i,2-butadiene) results in a polymer, soluble in mixtures of h2o and alcohol ( Figure 2 ). 16,17 In the absenteeism of classical amphiphilicity of established block copolymers, aggregates can exist observed probably due to hydrogen bonding and entropic effects. This example points out that fifty-fifty at the lowest level of peptide–polymer conjugates, elementary driving forces, which are responsible for the folding of high-molecular-weight protein chains, inherently exist in unmarried AA moieties. However, functional and structural diversity and hierarchical complexity are rather limited, since these are encoded in the monomer sequence of peptide segments.

Figure two. Synthesis of bio-hybrid amphiphiles by radical add-on of cysteine-based dipeptides onto poly(ane,ii-butadiene)-block-poly(ethylene oxide)s and fluorescence microscopy images of self-assembled aggregates in aqueous solution.

 Reprinted with permission from Geng, Y.; Discher, D. E.; Justynska, J.; Schlaad, H. Angew. Chem., Int. Ed. 2006, 45, 7578 and Lutz, J.-F.; Schlaad, H. Polymer 2008, 49, 817. Copyright 2008, Elsevier. 16,17

Polymer–peptide conjugates that exhibit linear oligo- or polypeptides with upwards to ∼ forty AA in length possess, in contrast to the polymers modified with single AAs, the crucial AA sequence as a primal characteristic to plant diversity. It is noteworthy that already very brusque oligopeptides frequently express highly specified (bio)-functions. For example, 1 of the active cell recognition motifs of fibronectin, which is a 500-kDa adhesion glycoprotein, consists of the peptide Arg-Gly-Asp (RGD). This short RGD domain allows for the realization of bioactivity in polymer–peptide conjugates, considering certain cell-surface proteins (integrins) demark specifically to this sequence, mediating cell adhesion. 18 Moreover, it was demonstrated that ii repeats of alternate valine and threonine ((Val-Thr)2Axx) show specific self-recognition, if preorganized with an appropriate template. nineteen The conjugation of such a peptide-based organizer segment to poly(ethylene oxide) (PEO) enables the command of the microstructure formation in solution. Well-defined nanotapes were obtained, driven by the specific assembly of the peptide segments as it was encoded in the AA sequence. More complex macrotapes exhibiting a defined hierarchical inner construction and length of up to millimeters could be accessed by the directed self-assembly of a conjugate that comprises a (Val-Thr)5 domain and PEO. 20 Several other peptide-based aggregation motifs have been exploited by the conjugation of oligopeptides to polymers to induce and control microstructure formation processes in synthetic polymers. 21 Among these examples, peptides were utilized that evidence self-arrangement via specific interactions. It was shown that polymers tin exist organized, for instance, into tape-similar structures past using the β-sheet motif or into bundles by packing α-helices into coiled-gyre motifs. Furthermore, responsive networks could be realized, on the ane mitt, by the integration of peptide sequences based on collagen, leading to the germination of stiff triple helix connectivities. On the other hand, temperature-responsive cross-linking was achieved using sequences derived from elastin, which exhibit a tunable lower critical aggregation temperature.

The examples presented in a higher place demonstrate that the increase in the number of AAs in a peptide sequence dramatically increases the possibilities. However, compared to complex proteins with more than 100 AAs and ofttimes several subunits, these short oligopeptide segments can be easily accessed through chemical synthesis, if required conveniently in scales of upward to multiple grams. Even more important might exist that the sequence–property human relationship of the oligopeptides is still insufficiently simple. Frequently, this allows an accurate prediction past figurer simulation methods, making the rational design of functional segments possible.

However, advanced properties such as selective catalytic activity, highly specific recognition, or directional functions (such every bit send and the combination of multiple functions, including regulatory and signaling mechanisms) can and then far only be achieved by the integration of native, high-molecular-weight proteins. Frequently, these consist of several subunits and a complex, hierarchical structure is found that is optimized by evolutionary processes. Despite all the progress in protein structure analysis and computational modeling, the relationship between the AA sequence and the protein structure that results from distinct folding processes is withal hard to predict. Due to this, the de novo synthesis of proteins remains challenging, making the conjugates of synthetic polymers to proteins from biological sources an unrivaled strategy to conjugate with highly complex functions.

In the recent years, substantial progress was made in the fields of protein engineering and biomaterials design. 22–24 This was demonstrated by Smeenk et al., 25 reporting the protein controlled self-assembly of polymer–poly peptide conjugates. The bioconjugates comprised PEO chains that were fastened to both termini of a genetically engineered poly peptide. The utilization of a segmented protein with a repetitive (β-γ) 10 folding domain ((sheet-plow)-multimer) leads to the self-assembly into well-defined fiber-like structures with a protein cadre and PEO beat out. The latter prevented lateral interactions and iii-dimensional (3D) network formation, causing homogeneous dispersion of the nanostructures in solution. The primary structure of the folding domain allowed the precise aligning of both dimensions and functionality of the protein core. 26 This case demonstrates clearly the possibilities of modern synthetic approaches, which combine standard polymer chemistry and genetic engineering.

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Pushing the Bacterial Envelope

Samir Gautam , David A. Spiegel , in Micro- and Nanoengineering of the Cell Surface, 2014

Polypeptides at the cell surface have been similarly re-engineered via 2-step metabolic labeling techniques. In analogy to the functionalized monosaccharides used to label glycans, chemically tagged noncanonical amino acids (ncAAs) are incorporated into proteins and presented on the cell surface for subsequent ligation. To this cease, ncAAs such every bit azidohomoalanine, azidonorvaline, and azidonorleucine have been shown to serve equally methionine surrogates, replacing the endogenous amino acid during translation [358–362]. Alkyne-functionalized compounds, in turn, are fastened to these protein-spring, surface-exposed azides. Through this arroyo, methionines are globally replaced with ncAAs—a particularly valuable feature in sure settings (east.k., proteomic analysis). However, for site-specific modification, an alternative technique—pioneered past Schultz et al.—must be used. Offset, a genetically engineered tRNA–tRNA synthetase pair, designed to incorporate a ketone-containing ncAA (m-acetyl-50-phenylalanine) into a recombinant surface poly peptide in response to the amber nonsense finish codon, is introduced into a bacterial strain. So, the strain is incubated with m-acetyl-fifty-phenylalanine, so that the ncAA is selectively incorporated into the recombinant poly peptide. Finally, the surface-exposed ketone functionality is used as an attachment point for a small molecule containing a hydrazine or hydroxylamine group [363].

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