Site-Specific Polymer Attachment to a CCL-5 (RANTES) Analogue by Oxime Exchange

The CuAAC: Principles, Homogeneous and Heterogeneous Catalysts, and Novel Developments and Applications

The copper-catalyzed azide/alkyne cycloaddition reaction (CuAAC) has emerged as the most useful "click" chemistry. Polymer science has profited enormously from CuAAC by its simplicity, ease, scope, applicability and efficiency. Basic principles of the CuAAC are reviewed with a focus on homogeneous and heterogeneous catalysts, ligands, anchimeric assistance, and basic chemical principles. Recent developments of ligand design and acceleration are discussed.

A solid-phase affinity labeling method for target-selective isolation and modification of proteins

Solid-phase affinity labeling of a target protein, peanut agglutinin (PNA), with the specifically designed chemical tool 1 selectively and effectively furnished the labeled PNA. Furthermore, this method was applicable to native human carbonic anhydrase II in red blood cell lysate using the chemical tool 2 without the need for tedious manipulations.

Polymeric anti-HIV therapeutics

The scope of this review is to highlight the application of polymer therapeutics in an effort to curb the transmission and infection of the human immunodeficiency virus (HIV). Following a description of the HIV life cycle, the use of approved antiretroviral drugs that inhibit critical steps in the HIV infection process is highlighted. After that, a comprehensive overview of the structure and inhibitory properties of polymeric anti-HIV therapeutic agents is presented. This overview will include inhibitors based on polysaccharides, synthetic polymers, dendritic polymers, polymer conjugates as well as polymeric DC-SIGN antagonists. The review will conclude with a section that discusses the applications of polymers and polymer conjugates as systemic and topical anti-HIV therapeutics.

PEG-peptide conjugates

The remarkable diversity of the self-assembly behavior of PEG-peptides is reviewed, including self-assemblies formed by PEG-peptides with β-sheet and α-helical (coiled-coil) peptide sequences. The modes of self-assembly in solution and in the solid state are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized.

N-Terminal α-amino group modification of peptides by an oxime formation-exchange reaction sequence

A site-specific and efficient method for N-terminal modification of peptides using oxone for selective oxidation of N-terminal α-amino groups of peptides to oximes followed by transoximation with O-substituted hydroxylamines has been developed.

“Click” reactions: a versatile toolbox for the synthesis of peptide-conjugates

Peptides that comprise the functional subunits of proteins have been conjugated to versatile materials (biomolecules, polymers, surfaces and nanoparticles) in an effort to modulate cell responses, specific binding affinity and/or self-assembly behavior.

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).

Peptide and protein-based inhibitors of HIV-1 co-receptors

Human immunodeficiency virus (HIV) afflicts an estimated 30 million people globally, making it a continuing pandemic. Despite major research efforts, the rate of new infections has remained relatively static over time. This article reviews an emerging strategy for the treatment of HIV, the inhibition of the co-receptors necessary for HIV entry, CCR5 and CXCR4. The aim of this article is to highlight potential therapeutics derived from peptides and proteins that show particular promise in HIV treatment. Molecules that act on CCR5, CXCR4 or on both receptors will be discussed herein.

Emerging synthetic approaches for protein-polymer conjugations

Protein-polymer conjugates are important in diverse fields including drug delivery, biotechnology, and nanotechnology. This feature article highlights recent advances in the synthesis and application of protein-polymer conjugates by controlled radical polymerization techniques. Special emphasis on new applications of the materials, particularly in biomedicine, is provided.

Sortase-catalyzed transformations that improve the properties of cytokines

Recombinant protein therapeutics often suffer from short circulating half-life and poor stability, necessitating multiple injections and resulting in limited shelf-life. Conjugation to polyethylene glycol chains (PEG) extends the circulatory half-life of many proteins, but the methods for attachment often lack specificity, resulting in loss of biological activity. Using four-helix bundle cytokines as an example, we present a general platform that uses sortase-mediated transpeptidation to facilitate site-specific attachment of PEG to extend cytokine half-life with full retention of biological activity. Covalently joining the N and C termini of proteins to obtain circular polypeptides, again executed using sortase, increases thermal stability. We combined both PEGylation and circularization by exploiting two distinct sortase enzymes and the use of a molecular suture that allows both site-specific PEGylation and covalent closure. The method developed is general, uses a set of easily accessible reagents, and should be applicable to a wide variety of proteins, provided that their termini are not involved in receptor binding or function.

Biohybrid block copolymers: towards functional micelles and vesicles

This critical review covers the elaboration of micelles and vesicles made from block copolymers containing peptide or oligonucleotide blocks with a focus on recent developments toward responsive and functional assemblies (166 references).

Fluorous tagged N-hydroxy phthalimide for the parallel synthesis of O-aryloxyamines

The parallel synthesis of O-aryloxyamines remains an unfulfilled need in the field of medicinal chemistry and fragment-based approaches. To fill this gap a solution-phase two-step process based on (1) a copper-catalyzed cross-coupling of aryl boronic acids with a fluorous tagged N-hydroxyphthalimide, and (2) a supported aminolysis was designed and optimized using Taguchi's method. A library of O-aryloxyamines was synthesized in high yields with high purity and diversity.

Synthesis of Aminooxy End-functionalized pNIPAAm by RAFT Polymerization for Protein and Polysaccharide Conjugation

A Boc-protected aminooxy end-functionalized poly(N-isopropylacrylamide) (pNIPAAm) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The monomer was polymerized in the presence of a Boc-protected aminooxy trithiocarbonate chain transfer agent (CTA) utilizing 2,2'-azobis(2-isobutyronitrile) (AIBN) as the initiator in DMF at 70 °C. The final polymer had a number-average molecular weight (M(n)) of 4,200 Da as determined by (1)H NMR spectroscopy and a narrow polydispersity index (1.14) by gel permeation chromatography (GPC). The Boc group was removed, and the polymer was then incubated with N(ε)-levulinyl lysine-modified bovine serum albumin (BSA). Gel electrophoresis confirmed that the conjugation was successful. The aminooxy end-functionalized pNIPAAm was also immobilized on a gold surface after reduction of the trithiocarbonate end-group. The pNIPAAm surface was then incubated with an aldehyde-modified heparin to yield the polysaccharide-functionalized surface. All surface modifications were monitored by FT-IR spectroscopy.

Peptide/protein-polymer conjugates: synthetic strategies and design concepts

This feature article provides a compilation of tools available for preparing well-defined peptide/protein-polymer conjugates, which are defined as hybrid constructs combining (i) a defined number of peptide/protein segments with uniform chain lengths and defined monomer sequences (primary structure) with (ii) a defined number of synthetic polymer chains. The first section describes methods for post-translational, or direct, introduction of chemoselective handles onto natural or synthetic peptides/proteins. Addressed topics include the residue- and/or site-specific modification of peptides/proteins at Arg, Asp, Cys, Gln, Glu, Gly, His, Lys, Met, Phe, Ser, Thr, Trp, Tyr and Val residues and methods for producing peptides/proteins containing non-canonical amino acids by peptide synthesis and protein engineering. In the second section, methods for introducing chemoselective groups onto the side-chain or chain-end of synthetic polymers produced by radical, anionic, cationic, metathesis and ring-opening polymerization are described. The final section discusses convergent and divergent strategies for covalently assembling polymers and peptides/proteins. An overview of the use of chemoselective reactions such as Heck, Sonogashira and Suzuki coupling, Diels-Alder cycloaddition, Click chemistry, Staudinger ligation, Michael's addition, reductive alkylation and oxime/hydrazone chemistry for the convergent synthesis of peptide/protein-polymer conjugates is given. Divergent approaches for preparing peptide/protein-polymer conjugates which are discussed include peptide synthesis from synthetic polymer supports, polymerization from peptide/protein macroinitiators or chain transfer agents and the polymerization of peptide side-chain monomers.

Synthesis of protein–polymer conjugates

Protein-polymer conjugates are widely employed for applications in medicine, biotechnology and nanotechnology. Covalent attachment of synthetic polymers to proteins improves protein stability, solubility, and biocompatibility. Furthermore, synthetic polymers impart new properties such as self assembly and phase behavior. Polymer attachment at amino acid side-chains and at ligand binding sites is typically exploited. This Emerging Area focuses on synthetic methods to prepare protein-reactive polymers and also employing the protein itself as an initiator for polymerization.

Site-specific polymer modification of therapeutic proteins

Recent advances in chemoselective ligation technology have made possible the modification of proteins with polymers in a site-specific and controlled manner. These approaches rely on the incorporation of chemoselective anchors into the protein backbone by either chemical or recombinant means, and subsequent modification with a polymer carrying a complementary linker. As a result, the assembly process and the covalent structure of the resulting protein-polymer conjugate are completely controlled, enabling the rational optimization of drug properties, in particular efficacy and pharmacokinetic properties. Application of chemoselective ligation technologies to cytokines and chemokines has led to the generation of new lead proteins for use as erythropoietic agents and HIV fusion inhibitors.