Towards the Simplification of Protein Synthesis: Iterative Solid-Supported Ligations with Concomitant Purifications

New method for peptide purification based on selective removal of truncation peptide impurities after SPPS with orthogonal capping

Peptide purification by high-performance liquid chromatography (HPLC) is associated with high solvent consumption, relatively large effort and lack of efficient parallelization. As an alternative, many catch-and-release (c&r) purification methods have been developed over the last decades to enable the efficient parallel purification of peptides originating from solid-phase peptide synthesis (SPPS). However, with one exception, none of the c&r systems has been widely established in industry and academia until today. Herein, we present an entirely new chromatography-free purification concept for peptides synthesized on a solid support, termed reactive capping purification (RCP). The RCP method relies on the capping of truncation peptides arising from incomplete coupling of amino acids during SPPS with a reactive tag. The reactive tag contains a masked functionality that, upon liberation during cleavage from the resin, enables straightforward purification of the peptide by incubation with a resin-bound reactive moiety. In this work, two different reactive tags based on masked thiols were developed. Capping with these reactive tags during SPPS led to effective modification of truncated sequences and subsequent removal of the latter by chemoselective reaction with a maleimide-functionalized solid support. By introducing a suitable protecting group strategy, the thiol-based RCP method described here could also be successfully applied to a thiol-containing peptide. Finally, the purification of a 15-meric peptide by the RCP method was demonstrated. The developed method has low solvent consumption, has the potential for efficient parallelization, uses readily available reagents, and is experimentally simple to perform.

Towards the use of an amino acid cleavable linker for solid-phase chemical synthesis of peptides and proteins

The synthesis of proteins by solid-phase chemical ligation (SPCL) suffers from the paucity of linkers that can be cleaved under mild conditions. Here, we deployed a spontaneous nickel-assisted cleavage (SNAC) tag, known to undergo spontaneous cleavage in the presence of nickel(II), as a linker for C-to-N SPCL.

Multivalent Pyrrolidine Iminosugars: Synthesis and Biological Relevance

Recently, the strategy of multivalency has been widely employed to design glycosidase inhibitors, as glycomimetic clusters often induce marked enzyme inhibition relative to monovalent analogs. Polyhydroxylated pyrrolidines, one of the most studied classes of iminosugars, are an attractive moiety due to their potent and specific inhibition of glycosidases and glycosyltransferases, which are associated with many crucial biological processes. The development of multivalent pyrrolidine derivatives as glycosidase inhibitors has resulted in several promising compounds that stand out. Herein, we comprehensively summarized the different synthetic approaches to the preparation of multivalent pyrrolidine clusters, from total synthesis of divalent iminosugars to complex architectures bearing twelve pyrrolidine motifs. Enzyme inhibitory properties and multivalent effects of these synthesized iminosugars were further discussed, especially for some less studied therapeutically relevant enzymes. We envision that this comprehensive review will help extend the applications of multivalent pyrrolidine iminosugars in future studies.

On Demand Attachment and Detachment of rac-2-Br-DMNPA Tailoring to Facilitate Chemical Protein Synthesis

Herein, we developed a bifunctional reagent rac-2-Br-DMNPA 2 for the late-stage protection of peptide cysteine. Through the identification of its t-Bu ester 1 as a more competent form under ligation conditions, facile N-terminal and side-chain caging for the model peptide and protein were accomplished. Building upon this, a one-pot ligation and photolysis strategy was applied in the synthesis of the mini-protein chlorotoxin. More importantly, we extended the utility of 2 as a bifunctional linker for traceless solid-phase chemical ligation.

Enzyme-Cleavable Linkers for Protein Chemical Synthesis through Solid-Phase Ligations

The total synthesis of long proteins requires the assembly of multiple fragments through successive ligations. The need for intermediate purification steps is a strong limitation, particularly in terms of overall yield. One solution to this problem would be solid-supported chemical ligation (SPCL), for which a first peptide segment must be immobilized on a SPCL-compatible solid support through a linker that can be cleaved under very mild conditions to release the assembled protein. The cleavage of SPCL linkers has previously required chemical conditions sometimes incompatible with sensitive protein targets. Herein, we describe an alternative enzymatic approach to trigger cleavage under extremely mild and selective conditions. Optimization of the linker structure and use of a small enzyme able to diffuse into the solid support were key to the success of the strategy. We demonstrated its utility by the assembly of three peptide segments on the basis of native chemical ligation to afford a 15 kDa polypeptide.

1,5-Disubstituted 1,2,3-Triazoles as Amide Bond Isosteres Yield Novel Tumor-Targeting Minigastrin Analogs

1,5-Disubstituted 1,2,3-triazoles (1,5-Tz) are considered bioisosteres of cis-amide bonds. However, their use for enhancing the pharmacological properties of peptides or proteins is not yet well established. Aiming to illustrate their utility, we chose the peptide conjugate [Nle15]MG11 (DOTA-dGlu-Ala-Tyr-Gly-Trp-Nle-Asp-Phe-NH2) as a model compound since it is known that the cholecystokinin-2 receptor (CCK2R) is able to accommodate turn conformations. Analogs of [Nle15]MG11 incorporating 1,5-Tz in the backbone were synthesized and radiolabeled with lutetium-177, and their pharmacological properties (cell internalization, receptor binding affinity and specificity, plasma stability, and biodistribution) were evaluated and compared with [Nle15]MG11 as well as their previously reported analogs bearing 1,4-disubstituted 1,2,3-triazoles. Our investigations led to the discovery of novel triazole-modified analogs of [Nle15]MG11 with nanomolar CCK2R-binding affinity and 2-fold increased tumor uptake. This study illustrates that substitution of amides by 1,5-disubstituted 1,2,3-triazoles is an effective strategy to enhance the pharmacological properties of biologically active peptides.

Traceless parallel peptide purification by a first-in-class reductively cleavable linker system featuring a safety-release

Hundreds of peptides can be synthesized by automated parallel synthesizers in a single run. In contrast, the most widely used peptide purification method – high-pressure liquid chromatography (HPLC) – only allows one-by-one processing of each sample. The chromatographic purification of many peptides, therefore, remains a time-consuming and costly effort. Catch-and-release methods can be processed in parallel and potentially provide a remedy. However, no such system has yet provided a true alternative to HPLC. Herein we present the development of a side-reaction free, reductively cleavable linker. The linker is added to the target peptide as the last building block during peptide synthesis. After acidic cleavage from synthetic resin, the linker-tagged full-length peptide is caught onto an aldehyde-modified solid support by rapid oxime ligation, allowing removal of all impurities lacking the linker by washing. Reducing the aryl azide to an aniline sensitizes the linker for cleavage. However, scission does not occur at non-acidic pH enabling wash out of reducing agent. Final acidic treatment safely liberates the peptide by an acid-catalysed 1,6-elimination. We showcase this first-in-class reductively cleavable linker system in the parallel purification of a personalized neoantigen cocktail, containing 20 peptides for cancer immunotherapy within six hours.

A first-in-class reductively cleavable linker system that enables parallel and traceless purification of peptides through a safety-release is introduced with three linker types and showcased by rapid production of 20 personalized neoantigen peptides.

A straightforward methodology to overcome solubility challenges for N-terminal cysteinyl peptide segments used in native chemical ligation

One of the main limitations encountered during the chemical synthesis of proteins through native chemical ligation (NCL) is the limited solubility of some of the peptide segments. The most commonly used solution to overcome this problem is to derivatize the segment with a temporary solubilizing tag. Conveniently, the tag can be introduced on the thioester segment in such a way that it is removed concomitantly with the NCL reaction. We herein describe a generalization of this approach to N-terminal cysteinyl segment counterparts, using a straightforward synthetic approach that can be easily automated from commercially available building blocks, and applied it to a well-known problematic target, SUMO-2.

An optimized protocol for the synthesis of N-2-hydroxybenzyl-cysteine peptide crypto-thioesters

We herein report a robust upgraded synthetic protocol for the synthesis of N-Hnb-Cys crypto-thioester peptides, useful building blocks for segment-based chemical protein synthesis through native chemical ligation. We recently observed the formation of an isomeric co-product when using a different solid support than the originally-reported one, thus hampering the general applicability of the methodology. We undertook a systematic study to characterize this compound and identify the parameters favouring its formation. We show here that epimerization from l- to d-cysteine occurred during the key solid-supported reductive amination step. We also observed the formation of imidazolidinones by-products arising from incomplete reduction of the imine. Structural characterization combined with the deciphering of underlying reaction mechanisms allowed us to optimize conditions that abolished the formation of all these side-products.

Design, synthesis, characterization of peripherally tetra-pyridine-triazole-substituted phthalocyanines and their inhibitory effects on cholinesterases (AChE/BChE) and carbonic anhydrases (hCA I, II and IX)

In this study, phthalocyanine precursors (5and9) and 1,2,3-triazole-substituted metal-free and metallo phthalocyanines (9a–c) were designed and synthesized for the first time and evaluatedin vitrofor key molecular targets.

Photo-cleavable purification/protection handle assisted synthesis of giant modified proteins with tandem repeats

Proteins with tandem repeats have essential physical or biological roles in cells and have been widely investigated as biomaterials or vaccines. Chemically derived proteins with tandem repeats would be beneficial for research, owing to their accurate structures, possibly with precise modifications, produced by chemical synthesis. Traditional protein synthesis often leads to severe handling loss due to multiple ligations and HPLC purifications. To improve the protein synthesis efficiency, we developed a purification/protection handle consisting of a His6 tag and a photo-labile linker. This handle has great potential to facilitate purification with immobilized metal affinity chromatography techniques and also provides orthogonal protection for N-terminal Cys. The synthesis of the model proteins Muc1 and antifreeze glycoprotein mimics shows that the handle decreases the requirement for HPLC and enables both convergent and sequential assembly of peptide segments.

Triazole substituted metal-free, metallo-phthalocyanines and their water soluble derivatives as potential cholinesterases inhibitors: Design, synthesis and in vitro inhibition study

In this study, 1,2,3-triazole substituted metal-free and metallo phthalocyanines (4, 5, 6) and their water soluble derivatives (4a, 5a, 6a) were designed, synthesized for the first time and tested in vitro on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. Most phthalocyanines exhibited good inhibitory activities on these enzymes. Among the six phthalocyanines and starting compounds, 4a showed the most interesting profile as a submicromolar selective inhibitor of AChE (IC₅₀ = 0.040 µM) and 5a showed the most effective inhibitor of BChE (IC₅₀ = 0.1198 µM).

How are 1,2,3-triazoles accommodated in helical secondary structures?

1,4-Disubstituted-1,2,3-triazole (Tz) is widely used in peptides as a trans-amide bond mimic, despite having hazardous effects on the native peptide activity. The impact of amide bond substitution by Tz on peptide secondary structures is scarcely documented. We performed a Tz scan, by systematically replacing peptide bonds following the Aib residues with Tz on two model peptaibols: alamethicin F50/5 and bergofungin D, which adopt stable α- and 310 helices, respectively. We observed that the Tz insertion, whatever its position in the peptide sequences, abolished their antimicrobial activity. The structural consequences of this insertion were further investigated using CD, NMR and X-ray diffraction. Importantly, five crystal structures that were incorporated with Tz were solved, showing various degrees of alteration of the helical structures, from minor structural perturbation of the helix to partial disorder. Together, these results showed that Tz insertions impair helical secondary structures.

Synthesis of aryl-thioglycopeptides through chemoselective Pd-mediated conjugation

We describe herein a Pd-catalyzed methodology for the thioglycoconjugation of iodoaryl peptides and aminoacids. This operationally simple process occurs under semi-aqueous conditions and displays wide substrate scope. The strategy has been successfully applied to both the thioglycosylation of unprotected peptides and the generation of thioglyco-aminoacid building blocks, including those suitable for solid phase peptide synthesis. To demonstrate the broad potential of this technique for late stage functionalization, we successfully incorporated challenging unprotected β-S-GlcNAc- and α-S-GalNAc-derivatives into very long unprotected peptides. This study opens the way to new applications in chemical biology, considering the well-recognized advantages of S-glycosides over O-glycosides in terms of resistance towards both enzymatic and chemical degradation.

Design, Synthesis, and Immunological Evaluation of a Multicomponent Construct Based on a Glycotripeptoid Core Comprising B and T Cell Epitopes and a Toll-like Receptor 7 Agonist That Elicits Potent Immune Responses

We present here for the first time the synthesis and immunological evaluation of a fully synthetic three-component anticancer vaccine candidate that consists of a β-glycotripeptoid core mimicking a cluster of Tn at the surface of tumor cells (B epitope), conjugated to the OVA 323-339 peptide (T-cell epitope) and a Toll-like receptor 7 (TLR7) agonist for potent adjuvanticity. The immunological evaluation of this construct and of precursor components demonstrated the synergistic activity of the components within the conjugate to stimulate innate and adaptive immune cells (DCs, T-helper, and B-cells). Surprisingly, immunization of mice with the tricomponent GalNAc-based construct elicited a low level of anti-Tn IgG but elicited a very high level of antibodies that recognize the TLR7 agonist. This finding could represent a potential vaccine therapeutic approach for the treatment of some autoimmune diseases such as lupus.

Harnessing pyrrolidine iminosugars into dimeric structures for the rapid discovery of divalent glycosidase inhibitors

The synthesis of three libraries (1a-l, 1a'-l' and 2a-l) of dimeric iminosugars through CuAAC reaction between three different alkynyl pyrrolidines and a set of diazides was carried out. The resulting crude dimers were screened in situ against two α-fucosidases (libraries 1a-l and 1a'-l') and one β-galactosidase (2a-l). This method is pioneer in the search of divalent glycosidase inhibitors. It has allowed the rapid identification of dimer 1i as the best inhibitor of α-fucosidases from bovine kidney (K_i = 0.15 nM) and Homo sapiens (K_i = 60 nM), and dimer 2e as the best inhibitor of β-galactosidase from bovine liver (K_i = 5.8 μM). In order to evaluate a possible divalent effect in the inhibition, the synthesis and biological analysis of the reference monomers were also performed. Divalent effect was only detected in the inhibition of bovine liver β-galactosidase by dimer 2e.

Leveraging a "Catch-Release" Logic Gate Process for the Synthesis and Nonchromatographic Purification of Thioether- or Amine-Bridged Macrocyclic Peptides

Macrocyclic peptides containing N-alkylated amino acids have emerged as a promising therapeutic modality, capable of modulating protein-protein interactions and an intracellular delivery of hydrophilic payloads. While multichannel automated solid-phase peptide synthesis (SPPS) is a practical approach for peptide synthesis, the requirement for slow and inefficient chromatographic purification of the product peptides is a significant limitation to exploring these novel compounds. Herein, we invent a "catch-release" strategy for the nonchromatographic purification of macrocyclic peptides. A traceless catch process is enabled by the invention of a dual-functionalized N-terminal acetate analogue, which serves as a handle for capture onto a purification resin and as a leaving group for macrocyclization. Displacement by a C-terminal nucleophilic side chain thus releases the desired macrocycle from the purification resin. By design, this catch/release process is a logic test for the presence of the key components required for cyclization, thus removing impurities which lack the required functionality, such as common classes of peptide impurities, including hydrolysis fragments and truncated sequences. The method was shown to be highly effective with three libraries of macrocyclic peptides, containing macrocycles of 5-20 amino acids, with either thioether- or amine-based macrocyclic linkages; in this latter class, the reported method represents an enabling technology. In all cases, the catch-release protocol afforded significant enrichment of the target peptides purity, in many cases completely obviating the need for chromatography. Importantly, we have adapted this process for automation on a standard multichannel peptide synthesizer, achieving an efficient and completely integrated synthesis and purification platform for the preparation of these important molecules.

A simple and traceless solid phase method simplifies the assembly of large peptides and the access to challenging proteins

We show that the combination of solid phase and solution ligation techniques facilitates the production of a challenging and biologically active protein made of 180 amino acids.

Chemical protein synthesis gives access to well-defined native or modified proteins that are useful for studying protein structure and function. The majority of proteins synthesized up to now have been produced using native chemical ligation (NCL) in solution. Although there are significant advantages to assembling large peptides or proteins by solid phase ligation, reports of such approaches are rare. We report a novel solid phase method for protein synthesis which relies on the chemistry of the acetoacetyl group and ketoxime ligation for the attachment of the peptide to the solid support, and on a tandem transoximation/rearrangement process for the detachment of the target protein. Importantly, we show that the combination of solid phase and solution ligation techniques facilitates the production of a challenging and biologically active protein made of 180 amino acids. We show also that the solid phase method enables the purification of complex peptide segments through a chemoselective solid phase capture/release approach.

Total chemical synthesis of proteins without HPLC purification

This work presents the first method for the rapid chemical total on-resin synthesis of proteins that proceeds without a single HPLC-purification step.

The total chemical synthesis of proteins is a tedious and time-consuming endeavour. The typical steps involve solid phase synthesis of peptide thioesters and cysteinyl peptides, native chemical ligation (NCL) in solution, desulfurization or removal of ligation auxiliaries in the case of extended NCL as well as many intermediary and final HPLC purification steps. With an aim to facilitate and improve the throughput of protein synthesis we developed the first method for the rapid chemical total on-resin synthesis of proteins that proceeds without a single HPLC-purification step. The method relies on the combination of three orthogonal protein tags that allow sequential immobilization (via the N-terminal and C-terminal ends), extended native chemical ligation and release reactions. The peptide fragments to be ligated are prepared by conventional solid phase synthesis and used as crude materials in the subsequent steps. An N-terminal His₆ unit permits selective immobilization of the full length peptide thioester onto Ni-NTA agarose beads. The C-terminal peptide fragment carries a C-terminal peptide hydrazide and an N-terminal 2-mercapto-2-phenyl-ethyl ligation auxiliary, which serves as a reactivity tag for the full length peptide. As a result, only full length peptides, not truncation products, react in the subsequent on-bead extended NCL. After auxiliary removal the ligation product is liberated into solution upon treatment with mild acid, and is concomitantly captured by an aldehyde-modified resin. This step allows the removal of the most frequently observed by-product in NCL chemistry, i.e. the hydrolysed peptide thioester (which does not contain a C-terminal peptide hydrazide). Finally, the target protein is released with diluted hydrazine or acid. We applied the method in the synthesis of 46 to 126 amino acid long MUC1 proteins comprising 2–6 copies of a 20mer tandem repeat sequence. Only three days were required for the parallel synthesis of 9 MUC1 proteins which were obtained in 8–33% overall yield with 90–98% purity despite the omission of HPLC purification.

Toward the Optimization of Bombesin-Based Radiotracers for Tumor Targeting

The peptide bombesin (BBN) is a peptide with high affinity for the gastrin-releasing peptide receptor (GRPr), a receptor that is overexpressed by, for example, breast and prostate cancers. Thus, GRPr agonists can be used as cancer-targeting vectors to shuttle diagnostic and therapeutic agents into tumor cells. With the aim of optimizing the tumor targeting properties of a radiolabeled [Nle(14)]BBN(7-14) moiety, novel BBN(7-14)- and BBN(6-14)-based radioconjugates were synthesized, labeled with Lu-177, and fully evaluated in vitro and in vivo. The effect of residue and backbone modification on several parameters such as the internalization of the radiolabeled peptides into PC3 and AR42J tumor cells, their affinity toward the human GRPr, metabolic stability in blood plasma, and biodistribution in mice bearing GRPr-expressing PC3 xenografts was studied. As a result of our investigations, a novel radiolabeled GRPr agonist with a high tumor uptake and a high tumor-to-kidney ratio was identified.

CuAAC: An Efficient Click Chemistry Reaction on Solid Phase

Click chemistry is an approach that uses efficient and reliable reactions, such as Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC), to bind two molecular building blocks. CuAAC has broad applications in medicinal chemistry and other fields of chemistry. This review describes the general features and applications of CuAAC in solid-phase synthesis (CuAAC-SP), highlighting the suitability of this kind of reaction for peptides, nucleotides, small molecules, supramolecular structures, and polymers, among others. This versatile reaction is expected to become pivotal for meeting future challenges in solid-phase chemistry.

NIR fluorescent DCPO glucose analogues and their application in cancer cell imaging

N3-DCPO and its glucose analogues were synthesized, and the linker's length impact on cellular uptake was studied.

Combining triazole ligation and enzymatic glycosylation on solid phase simplifies the synthesis of very long glycoprotein analogues

The solid-phase chemical assembly of a protein through iterative chemoselective ligation of unprotected peptide segments can be followed with chemical and/or enzymatic transformations of the resulting immobilized protein, the latter steps thus benefitting from the advantages provided by the solid support. We demonstrate here the usefulness of this strategy for the chemo-enzymatic synthesis of glycoprotein analogues. A linker was specifically designed for application to the synthesis of O-glycoproteins: this new linker is readily cleaved under mild aqueous conditions compatible with very sensitive glycosidic bonds, but is remarkably stable under a wide range of chemical and biochemical conditions. It was utilized for solid-supported N-to-C peptidomimetic triazole ligation followed by enzymatic glycosylation, ultimately leading to a very large MUC1-derived glycoprotein containing 160 amino acid residues, 24 α-GalNAc moieties linked to Ser and Thr, and 3 triazoles as peptide bond mimetics.

Solid phase chemical ligation employing a rink amide linker for the synthesis of histone H2B protein

Presented here is a solid phase chemical ligation strategy employing native chemical ligation and the commercially available Rink-amide linker as a key element in our approach. The method was applied for the synthesis of histone H2B, which sets the ground for the rapid preparation of posttranslationally modified analogues of this protein.

Rational design of triazololipopeptides analogs of kisspeptin inducing a long-lasting increase of gonadotropins

New potent and selective KISS1R agonists were designed using a combination of rational chemical modifications of the endogenous neuropeptide kisspeptin 10 (KP10). Improved resistance to degradation and presumably reduced renal clearance were obtained by introducing a 1,4-disubstituted 1,2,3-triazole as a proteolysis-resistant amide mimic and a serum albumin-binding motif, respectively. These triazololipopeptides are highly potent full agonists of KISS1R and are >100 selective over the closely related NPFF1R. When injected in ewes with a quiescent reproductive system, the best compound of our series induced a much prolonged increase of luteinizing hormone release compared to KP10 and increased follicle-stimulating hormone plasma concentration. Hence, this KISS1R agonist is a new valuable pharmacological tool to explore the potential of KP system in reproduction control. Furthermore, it represents the first step to develop drugs treating reproductive system disorders due to a reduced activity of the hypothalamo-pituitary-gonadal axis such as delayed puberty, hypothalamic amenorrhea, and hypogonadotropic hypogonadism.

Hyperbranched poly(triazole) with thermal and metal ion dual stimuli-responsiveness

Hyperbranched poly(triazole) bearing oligo(ethylene glycol) terminal groups is dual stimuli-responsive to thermal conditions and metal ions and is capable for the selective absorption of Ag⁺ ion on tuning temperature.

Biologically targeted probes for Zn2+: a diversity oriented modular "click-SNAr-click" approach†Electronic supplementary information (ESI) available: Full experimental details including characterisation of all novel compounds can be found in the ESI. See DOI: 10.1039/c4sc01249f

We describe a one-pot strategy for the high yielding, operationally simple synthesis of fluorescent probes for Zn2+ that bear biological targeting groups and exemplify the utility of our method through the preparation of a small library of sensors. Investigation of the fluorescence behaviour of our library revealed that although all behaved as expected in MeCN, under biologically relevant conditions in HEPES buffer, a plasma membrane targeting sensor displayed a dramatic switch on response to excess Zn2+ as a result of aggregation phenomena. Excitingly, in cellulo studies in mouse pancreatic islets demonstrated that this readily available sensor was indeed localised to the exterior of the plasma membrane and clearly responded to the Zn2+ co-released when the pancreatic beta cells were stimulated to release insulin. Conversely, sensors that target intracellular compartments were unaffected. These results demonstrate that this sensor has the potential to allow the real time study of insulin release from living cells and exemplifies the utility of our simple synthetic approach.

Patchwork protein chemistry: a practitioner's treatise on the advances in synthetic peptide stitchery

With the study of peptides and proteins at the heart of many scientific endeavors, the omics era heralded a multitude of opportunities for chemists and biologists alike. Across the interface with life sciences, peptide chemistry plays an indispensable role, and progress made over the past decades now allows proteins to be treated as molecular patchworks stitched together through synthetic tailoring. The continuous elaboration of sophisticated strategies notwithstanding, Merrifield's solid-phase methodology remains a cornerstone of chemical protein design. Although the non-practitioner might misjudge peptide synthesis as trivial, routine, or dull given its long history, we comment here on its many advances, obstacles, and prospects from a practitioner's point of view. While sharing our perspectives through thematic highlights across the literature, this treatise provides an interpretive overview as a guide to novices, and a recap for specialists.

Solid phase protein chemical synthesis

The chemical synthesis of peptides or small proteins is often an important step in many research projects and has stimulated the development of numerous chemical methodologies. The aim of this review is to give a substantial overview of the solid phase methods developed for the production or purification of polypeptides. The solid phase peptide synthesis (SPPS) technique has facilitated considerably the access to short peptides (<50 amino acids). However, its limitations for producing large homogeneous peptides have stimulated the development of solid phase covalent or non-covalent capture purification methods. The power of the native chemical ligation (NCL) reaction for protein synthesis in aqueous solution has also been adapted to the solid phase by the combination of novel linker technologies, cysteine protection strategies and thioester or N,S-acyl shift thioester surrogate chemistries. This review details pioneering studies and the most recent publications related to the solid phase chemical synthesis of large peptides and proteins.

Solid phase oxime ligations for the iterative synthesis of polypeptide conjugates

All on-resin! An efficient C-to-N iterative strategy for solid phase chemical ligations (SPCL).

Probing the dendritic architecture through AIE: challenges and successes

Since the aggregation-induced emission (AIE) phenomenon is very sensitive to steric hindrance, we set out to use it as a tool to probe the periphery of dendrimers.

Solid-phase peptide synthesis and solid-phase fragment coupling mediated by isonitriles

The synthesis of polypeptides on solid phase via mediation by isonitriles is described. The acyl donor is a thioacid, which presumably reacts with the isonitrile to generate a thio-formimidate carboxylate mixed anhydride intermediate. Applications of this chemistry to reiterative solid-phase peptide synthesis as well as solid-phase fragment coupling are described.