13C NMR spectroscopic
integration employing short relaxation
delays was evaluated as a quantitative tool to obtain ratios of diastereomers,
regioisomers, constitutional isomers, mixtures of unrelated compounds,
peptoids, and sugars. The results were compared to established quantitative
methods such as 1H NMR spectroscopic integration, gas chromatography,
and high-performance liquid chromatography and were found to be within
<3.4% of 1H NMR spectroscopic values (most examples
give results within <2%). Acquisition of the spectra took 2–30
min on as little as 10 mg of sample, proving the general utility of
the technique. The simple protocol was extended to include end group
analysis of low molecular weight polymers, which afforded results
in accordance with 1H NMR spectroscopy and matrix-assisted
laser desorption-ionization time-of-flight spectrometry.
Poly(ethylene glycol) (PEG) side-chain functionalized lactide analogues have been synthesized in four steps from commercially available L-lactide. The key step in the synthesis is the 1,3-dipolar cycloaddition between PEG-azides and a highly strained spirolactide-heptene monomer, which proceeds in high conversions. The PEG-grafted lactides analogues were polymerized via ring-opening polymerization using triazacyclodecene as organocatalyst to give well-defined tri- and hepta-(ethylene glycol)-poly(lactide)s (PLA) with molecular weights above 10 kDa and polydispersity indices between 1.6 and 2.1. PEG-poly(lactide) (PLA) with PEG chain Mn 2000 was also prepared but GPC analysis showed a bimodal profile indicating the presence of starting macromonomer. Cell adhesion assays were performed using MC3T3 E-1 osteoblast-like cells demonstrating that PEG-containing PLA reduces cell adhesion significantly when compared to unfunctionalized PLA.
A tri(ethylene glycol)-containing lactide analogue was synthesized via thiol-ene chemistry between a bi-functional triethylene glycol and allyl lactide. Subsequent tin-octoate-catalyzed ring-opening polymerization yielded well-defined poly(lactide)-graft-poly(ethylene glycol) copolymers with molecular weights of 6000 g/mol and polydispersity indices of 1.6. The tri(ethylene glycol) chains along the copolymers contain azide termini that are capable of ‘click’-type postpolymerization functionalization. The utility of this strategy was demonstrated via successful Staudinger ligation to install the Gly-Arg-Gly-Asp-Ser (GRGDS) peptide.
The synthesis of C3‐symmetrical tristriazolotriazines with conjugated arms and lateral alkoxy side chains was performed by a threefold condensation of cyanuric chloride with tetrazoles. Conjugated π segments include phenyl, tolane, and its phenylethynyl‐elongated homologue. Disclike and a dendritic molecule have been obtained, and two compounds with a 3,4,5‐tris(octyloxy) substitution form broad thermotropic mesophases. The linear optical properties, solvatochromism of the fluorescence, acidochromism, and the two‐photon absorption efficiency of selected compounds are reported.
Polymer-protein conjugates are biohybrid macromolecules derived from covalently connecting synthetic polymers with polypeptides. The resulting materials combine the properties of both worlds: chemists can engineer polymers to stabilize proteins, to add functionality, or to enhance activity; whereas biochemists can exploit the specificity and complexity that Nature has bestowed upon its macromolecules. This has led to a wealth of applications, particularly within the realm of biomedicine. Polymer-protein conjugation has expanded to include scaffolds for drug delivery, tissue engineering, and microbial inhibitors. This feature article reflects upon recent developments in the field and discusses the applications of these hybrids from a biomaterials standpoint.
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