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Instruments / Technical Area	Publication Details	Published	Actions
B21-High Throughput SAXS	Influence of polymer molar mass and mixture stoichiometry on polyelectrolyte complexes of poly(l-arginine) and Poly(l-glutamic acid) Valeria Castelletto , Lucas De Mello , Foteini Arfara , Hermis Iatrou , Jani Seitsonen , Ian W. Hamley Polymer 3 DOI: 10.1016/j.polymer.2022.125497 Diamond Proposal Number(s): [29895] Show Abstract ▼ Abstract: Poly(l-arginine) (PARG) and poly(l-glutamic acid) (PLGA) homopolypeptides were custom synthesized by precision N-carboxyanhydride ring-opening polymerization methods with two molar masses, matched for pairs of cationic and anionic polypeptides (degrees of polymerization n = 100 and n = 500). The conformations of the homopolypeptides were probed using circular dichroism (CD) and FTIR spectroscopy which showed the presence of mainly polyproline II (PPII) conformation. Small-angle X-ray scattering (SAXS) showed concentration-dependent polyelectrolyte peaks and form factor with high q scaling due to the excluded volume behaviour of the wormlike chains. We then examined polyelectrolyte complexation in mixtures of pairs of PARG and PLGA polypeptides with matched molar masses. Precipitation was generally observed and the structures of precipitates, supernatant and resuspended precipitates were investigated using CD, SAXS and cryo-TEM. These revealed that, contrary to prior suggestions in the literature, the precipitates contain mostly polypeptides in a PPII-like conformation, and there is only a minimal β-sheet content (which is enhanced upon drying the sample during preparation for certain measurements). The precipitates have a fractal-like structure as revealed by cryo-TEM and SAXS. Our findings on the structure of polypeptide complex precipitates contribute to the understanding of phase separation of polyelectrolyte complexes and coacervation and may shed light on the formation of inter-cellular bodies of proteins and peptides such as Lewy and other inclusion bodies.	Nov 2022
B21-High Throughput SAXS	Self-assembly of telechelic tyrosine end-capped PEO star polymers in aqueous solution Charlotte J. C. Edwards-Gayle , Francesca Greco , Ian W. Hamley , Robert P. Rambo , Mehedi Reza , Janne Ruokolainen , Dimitrios Skoulas , Hermis Iatrou Biomacromolecules DOI: 10.1021/acs.biomac.7b01420 Diamond Proposal Number(s): [14684, 15778] Show Abstract ▼ Abstract: We investigate the self-assembly of two telechelic star polymer-peptide conjugates based on poly(ethylene oxide) (PEO) four-arm star polymers capped with oligotyrosine. The conjugates were prepared via N-carboxy anhydride (NCA)-mediated ring-opening polymerization from PEO star polymer macroinitiators. Self-assembly occurs above a critical aggregation concentration determined via fluorescence probe assays. Peptide conformation was examined using circular dichroism spectroscopy. The structure of self-assembled aggregates was probed using small-angle X-ray Scattering (SAXS) and cryogenic transmission electron microscopy (Cryo-TEM). In contrast to previous studies on linear telechelic PEO-oligotyrosine conjugates which show self-assembly into -sheet fibrils, the star architecture suppresses fibril formation and instead micelles are generally observed, a small population of fibrils only being observed upon pH adjustment. Hydrogelation is also suppressed by the polymer star architecture. However, hydrogels can be produce by addition of sodium alginate with calcium chloride. These peptide-functionalized star polymer solutions are cytocompatible at sufficiently low concentration. These polymers present tyrosine at high density and may be useful in the development of future enzyme or pH-responsive biomaterials.	Dec 2017

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