Anion-induced thermoresponsiveness in cationic polycysteine and DNA binding

This study describes the synthesis of an l-cysteine-based water-soluble cationic polypeptide, an investigation of its thermoresponsive behaviour in the presence of added anions and its polyplexation with DNA.

Phosphonopeptides containing free phosphonic groups: recent advances

Phosphonopeptides are mimetics of peptides in which phosphonic acid or related (phosphinic, phosphonous etc.) group replaces either carboxylic acid group present at C-terminus, is located in the peptidyl side chain, or phosphonamidate or phosphinic acid mimics peptide bond. Acting as inhibitors of key enzymes related to variable pathological states they display interesting and useful physiologic activities with potential applications in medicine and agriculture. Since the synthesis and biological properties of peptides containing C-terminal diaryl phosphonates and those with phosphonic fragment replacing peptide bond were comprehensively reviewed, this review concentrate on peptides holding free, unsubstituted phosphonic acid moiety. There are two groups of such mimetics: (i) peptides in which aminophosphonic acid is located at C-terminus of the peptide chain with most of them (including antibiotics isolated from bacteria and fungi) exhibiting antimicrobial activity; (ii) non-hydrolysable analogues of phosphonoamino acids, which are useful tools to study physiologic effects of phosphorylations.

Thiol–ene coupling reaction achievement and monitoring by “in situ” UV irradiation NMR spectroscopy

In this study, the possibilities of a new “in situ” LED UV illumination NMR spectroscopic technique for performing an initiator-free thiol–ene “click” coupling reaction of an allyl-functionalized poly(allyl glycidyl ether) (PAGE) prepolymer with a number of mono- and di-oligo polyethylene glycol (PEG) thiols is demonstrated. The state-of-the-art setup constructed with LEDs as UV light sources that illuminate through optical fibers directly into an NMR testing tube at a fixed wavelength of 365 nm is appropriate for various polymeric materials and biologically active substances. The selected experimental protocol uses a series of periods of irradiation and dark periods, thus providing opportunities to conduct an effective thiol–ene “click” reaction and simultaneously study the kinetics of the photochemical reaction with the exposure time, as well as macromolecular association directly in a solution applying the whole types of NMR methods: from conventional ¹H or ¹³C NMR to diffusion NMR spectroscopy (DOSY). In addition, the molecular mass characteristics of the prepared copolymers were studied by gel-permeation chromatography (GPC). The observed differences in the reaction rates as well as in the size of species formed (the corresponding hydrodynamic radiuses R_h of aggregates) as a result of the coupling process of parent PAGE prepolymers and model PEG thiols were thoroughly discussed and the reaction pathway proposed.

An “In situ” LED UV illumination NMR setup for achievement of initiator-free coupling reactions of allyl-functionalized poly(allyl glycidyl ether) with polyethylene glycols thiols.

Zwitterionic polypeptides bearing carboxybetaine and sulfobetaine: synthesis, self-assembly, and their interactions with proteins

Zwitterionic polypeptides bearing carboxybetaine and sulfobetaine were synthesized and their self-assembly and protein interactions were evaluated.

Synthetic polypeptides: from polymer design to supramolecular assembly and biomedical application

This review highlights the recent advances in the chemical design, supramolecular assembly, and biomedical application of synthetic polypeptides fromN-carboxyanhydrides.

Controlled Synthesis of End-Functionalized Mannose-6-phosphate Glycopolypeptides for Lysosome Targeting

The ubiquitous expression of the mannose-6-phosphate receptor on the majority of human cells makes it a valid target in the quest to deliver therapeutics selectively to the lysosome. In this work end-functionalized polyvalent mannose-6-phosphate glycopolypeptides (M6P-GPs) with high molecular weights (up to 22 kDa) have been synthesized via NCA polymerization. These synthetic M6P-GPs were found to display minimal toxicity to cells in vitro and show exceptional selectivity for trafficking into lysosomes in various cell lines. Comparison of the cellular uptake behavior of M6P-GP and the corresponding mannose-GP polymer reveals that incorporation of the phosphate moiety at the 6-position of mannose completely alters its trafficking behavior and becomes exclusively lysosome specific. We also demonstrate that trafficking of M6P-GPs in mammalian cells is likely associated with the CI-MPR receptor pathway.

Controlled Synthesis and Enzyme-Induced Hydrogelation of Poly(l-phosphotyrosine)s via Ring-Opening Polymerization of α-Amino Acid N-Carboxyanhydride

Tyrosine phosphorylation is an important post-translational modification (PTM) that governs numerous cellular processes. Constructing synthetic phosphotyrosine polypeptides helps expand the horizon of our understanding regarding the fundamental aspects and biological consequences of this PTM. Here, we report the synthesis of a novel monomer, O-diethylphospho l-tyrosine N-carboxyanhydride (pOEt TyrNCA), whose ring-opening polymerization (ROP) mediated by hexamethyldisilazane (HMDS) leads to poly(l-phosphotyrosine) (P(pTyr)) derivatives with controllable molecular weights and narrow molecular-weight distributions. Moreover, P(pTyr)₁₅-b-PEG-b-P(pTyr)₁₅ triblock copolymer (TBP15) undergo sol-gel transition in the presence of alkaline phosphatase. The stiffness of the gel is reinforced by the addition of horseradish peroxidase and hydrogen peroxide. These phosphotyrosine-mimicking polymers are realized for the first time by NCA polymerization and are promising materials for a variety of biological applications.

Controlled synthesis of phosphorylcholine derivatives of poly(serine) and poly(homoserine)

We report methods for the synthesis of polypeptides that are fully functionalized with desirable phosphorylcholine, PC, groups. Because of the inherent challenges in the direct incorporation of the PC group into α-amino acid N-carboxyanhydride (NCA) monomers, we developed a synthetic approach that combined functional NCA polymerization with efficient postpolymerization modification. While poly(L-phosphorylcholine serine) was found to be unstable upon synthesis, we successfully prepared poly(L-phosphorylcholine homoserine) with controlled chain lengths and found these to be water-soluble with disordered chain conformations.

Analogues of Poly(l-phosphoserine) via Living Polymerization of Phosphonate-Containing N-Carboxyanhydride Monomers

We have synthesized new phosphonate-containing α-amino acid N-carboxyanhydride (NCA) monomers and used these to prepare well-defined phosphonate-containing polypeptides and block copolypeptides. These NCAs were found to undergo living polymerization to high molecular weights with narrow chain length distributions. The methods described here demonstrate that phosphono polypeptides are also readily incorporated into block copolymers with controlled architecture and composition. One polymer, poly(l-phosphonohomoalanine) (poly(Pha)), is an isosteric analogue of poly(l-phosphoserine) and was found to display a pH-responsive conformational change. The pH-responsive α-helical conformation of poly(Pha) is unprecedented and may prove to be useful in the preparation of stimuli-responsive block copolypeptides containing poly(Pha) segments.

Thiol–ene “click” reactions and recent applications in polymer and materials synthesis: a first update

This contribution serves as an update to a previous review (Polym. Chem.2010,1, 17–36) and highlights recent applications of thiol–ene ‘click’ chemistry as an efficient tool for both polymer/materials synthesis as well as modification.