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22 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3 [Next/Last]

Instruments / Technical Area	Publication Details	Published
B21-High Throughput SAXS	Self-sorting in diastereomeric mixtures of functionalized dipeptides Qingwen Guan , Kate Mcaulay , Tian Xu , Sarah E. Rogers , Charlotte Edwards-Gayle , Ralf Schweins , Honggang Cui , Annela M. Seddon , Dave J. Adams Biomacromolecules DOI: 10.1021/acs.biomac.3c00246 Diamond Proposal Number(s): [29985] Open Access Show Abstract ▼ Abstract: Self-sorting in functionalized dipeptide systems can be driven by the chirality of a single amino acid, both at a high pH in the micellar state and at a low pH in the gel state. The structures formed are affected to some degree by the relative concentrations of each component showing the complexity of such an approach. The structures underpinning the gel network are predefined by the micellar structures at a high pH. Here, we describe the systems prepared from two dipeptide-based gelators that differ only by the chirality of one of the amino acids. We provide firm evidence for self-sorting in the micellar and gel phases using small-angle neutron scattering and cryo-transmission electron microscopy (cryo-TEM), showing that complete self-sorting occurs across a range of relative concentrations.	May 2023
B21-High Throughput SAXS I22-Small angle scattering & Diffraction	Self-assembly of tunable intrinsically disordered peptide amphiphiles Tamara Ehm , Hila Shinar , Guy Jacoby , Sagi Meir , Gil Koren , Merav Segal Asher , Joanna Korpanty , Matthew P. Thompson , Nathan C. Gianneschi , Michael M. Kozlov , Salome Azoulay-Ginsburg , Roey J. Amir , Joachim O. Rädler , Roy Beck Biomacromolecules DOI: 10.1021/acs.biomac.2c00866 Diamond Proposal Number(s): [21971, 24693, 29428, 28723, 28010] Open Access Show Abstract ▼ Abstract: Intrinsically disordered peptide amphiphiles (IDPAs) present a novel class of synthetic conjugates that consist of short hydrophilic polypeptides anchored to hydrocarbon chains. These hybrid polymer-lipid block constructs spontaneously self-assemble into dispersed nanoscopic aggregates or ordered mesophases in aqueous solution due to hydrophobic interactions. Yet, the possible sequence variations and their influence on the self-assembly structures are vast and have hardly been explored. Here, we measure the nanoscopic self-assembled structures of four IDPA systems that differ by their amino acid sequence. We show that permutations in the charge pattern along the sequence remarkably alter the headgroup conformation and consequently alter the pH-triggered phase transitions between spherical, cylindrical micelles and hexagonal condensed phases. We demonstrate that even a single amino acid mutation is sufficient to tune structural transitions in the condensed IDPA mesophases, while peptide conformations remain unfolded and disordered. Furthermore, alteration of the peptide sequence can render IDPAs to become susceptible to enzymatic cleavage and induce enzymatically activated phase transitions. These results hold great potential for embedding multiple functionalities into lipid nanoparticle delivery systems by incorporating IDPAs with the desired properties.	Dec 2022
I03-Macromolecular Crystallography I04-1-Macromolecular Crystallography (fixed wavelength)	How coiled-coil assemblies accommodate multiple aromatic residues Guto G. Rhys , William M. Dawson , Joseph L. Beesley , Freddie J. O. Martin , R. Leo Brady , Andrew Thomson , Derek N. Woolfson Biomacromolecules 2 DOI: 10.1021/acs.biomac.1c00131 Diamond Proposal Number(s): [12342] Show Abstract ▼ Abstract: Rational protein design requires understanding the contribution of each amino acid to a targeted protein fold. For a subset of protein structures, namely, α-helical coiled coils (CCs), knowledge is sufficiently advanced to allow the rational de novo design of many structures, including entirely new protein folds. Current CC design rules center on using aliphatic hydrophobic residues predominantly to drive the folding and assembly of amphipathic α helices. The consequences of using aromatic residues—which would be useful for introducing structural probes, and binding and catalytic functionalities—into these interfaces are not understood. There are specific examples of designed CCs containing such aromatic residues, e.g., phenylalanine-rich sequences, and the use of polar aromatic residues to make buried hydrogen-bond networks. However, it is not known generally if sequences rich in tyrosine can form CCs, or what CC assemblies these would lead to. Here, we explore tyrosine-rich sequences in a general CC-forming background and resolve new CC structures. In one of these, an antiparallel tetramer, the tyrosine residues are solvent accessible and pack at the interface between the core and the surface. In another more complex structure, the residues are buried and form an extended hydrogen-bond network.	Apr 2021
B21-High Throughput SAXS	Impact of arginine–phosphate interactions on the reentrant condensation of disordered proteins Samuel Lenton , Stefan Hervø-Hansen , Anton M. Popov , Mark D. Tully , Mikael Lund , Marie Skepö Biomacromolecules DOI: 10.1021/acs.biomac.0c01765 Diamond Proposal Number(s): [24294] Open Access Show Abstract ▼ Abstract: Re-entrant condensation results in the formation of a condensed protein regime between two critical ion concentrations. The process is driven by neutralization and inversion of the protein charge by oppositely charged ions. Re-entrant condensation of cationic proteins by the polyvalent anions, pyrophosphate and tripolyphosphate, has previously been observed, but not for citrate, which has similar charge and size compared to the polyphosphates. Therefore, besides electrostatic interactions, other specific interactions between the polyphosphate ions and proteins must contribute. Here, we show that additional attractive interactions between arginine and tripolyphosphate determine the re-entrant condensation and decondensation boundaries of the cationic, intrinsically disordered saliva protein, histatin 5. Furthermore, we show by small-angle X-ray scattering (SAXS) that polyvalent anions cause compaction of histatin 5, as would be expected based solely on electrostatic interactions. Hence, we conclude that arginine–phosphate-specific interactions not only regulate solution properties but also influence the conformational ensemble of histatin 5, which is shown to vary with the number of arginine residues. Together, the results presented here provide further insight into an organizational mechanism that can be used to tune protein interactions in solution of both naturally occurring and synthetic proteins.	Mar 2021
B21-High Throughput SAXS	The architectural change of the shell forming block from linear to V-shaped accelerates micellar disassembly but slows the complete enzymatic degradation of the amphiphiles Merav Segal , Lihi Ozery , Gadi Slor , Shreyas Shankar Wagle , Tamara Ehm , Roy Beck , Roey J. Amir Biomacromolecules DOI: 10.1021/acs.biomac.0c00882 Diamond Proposal Number(s): [24693] Show Abstract ▼ Abstract: Tuning the enzymatic degradation and disassembly rates of polymeric amphiphiles and their assemblies is crucial for designing enzyme-responsive nanocarriers for controlled drug delivery applications. The common methods to control the enzymatic degradation of amphiphilic polymers are to tune the molecular weights and ratios of the hydrophilic and hydrophobic blocks. In addition, to these approaches, the architecture of the hydrophilic block can also serve as a tool to tune enzymatic degradation and disassembly. To gain deeper understanding of the effect of the molecular architecture of the hydrophilic block we prepared two types of well-defined PEG-dendron amphiphiles bearing linear or V-shaped PEG chains as the hydrophilic blocks. The high molecular precision of these amphiphiles, which emerges from the utilization of dendrons as the hydrophobic blocks allowed us to study the self-assembly and enzymatic degradation and disassembly of the two types of amphiphiles with high resolution. Interestingly, the micelles of the V-shaped amphiphiles were significantly smaller and disassembled faster than those of the amphiphiles based on linear PEG. However, the complete enzymatic cleavage of the hydrophobic end-groups was significantly slower for the V-shaped amphiphiles. Our results show that the V-shape architecture can stabilize the unimer state and hence plays a double role in the enzymatic degradation and the induced disassembly and how it can be utilized to control the release of encapsulated or bound molecular cargo.	Aug 2020
I22-Small angle scattering & Diffraction	Aromatic stacking facilitated self-assembly of ultra-short ionic complementary peptide sequence: β-sheet nanofibres with remarkable gelation and interfacial properties Jacek K. Wychowaniec , Ronak Patel , James Leach , Rachel Mathomes , Vikesh Chhabria , Yogita Patil-Sen , Araida Hidalgo-Bastida , Robert T. Forbes , Joseph M. Hayes , Mohamed A. Elsawy Biomacromolecules DOI: 10.1021/acs.biomac.0c00366 Diamond Proposal Number(s): [17102] Open Access Show Abstract ▼ Abstract: Understanding peptide self-assembly mechanisms and stability of the formed assemblies is crucial for development of functional nanomaterials. Herein, we have adopted rational design approach to demonstrate how minimal structural modification to a non-assembling ultra-short ionic self-complementary tetrapeptide FEFK (Phe4) remarkably enhanced stability of self-assembly into β-sheet nanofibres and induced hydrogelation. This was achieved by replacing flexible phenylalanine residue (F) by the rigid phenylglycine (Phg) resulting in constrained analogue PhgEPhgK (Phg4), which positioned aromatic rings in an orientation favourable for aromatic stacking. Phg4 self-assembly into stable β-sheet ladders was facilitated by π-staking of aromatic sidechains alongside hydrogen bonding between backbone amides along the nanofibre axis. The contribution of these non-covalent interactions in stabilising self-assembly was predicted by in silico modelling using molecular dynamics simulations and semi-empirical quantum mechanics calculations. In aqueous medium, Phg4 β-sheet nanofibres entangled at a critical gelation concentration > 20 mg/mL forming a network of nanofibrous hydrogel. Phg4 also demonstrated unique surface activity in presence of immiscible oils and was superior to commercial emulsifiers in stabilising oil-in-water emulsions. This was attributed to interfacial adsorption of amphiphilic nanofibrilles forming nanofibrillised microspheres. To our knowledge, Phg4 is the shortest ionic self-complementary peptide rationally designed to self-assemble into stable β-sheet nanofibres capable of gelation and emulsification. Our results suggest that Ultra-short Ionic-complementary Constrained Peptides or UICPs have significant potential for the development of cost-effective, sustainable and multifunctional soft bionanomaterials.	May 2020
I22-Small angle scattering & Diffraction	Role of sheet-edge interactions in β-sheet self-assembling peptide hydrogels Jacek K. Wychowaniec , Andrew Smith , Cosimo Ligorio , Oleksandr O. Mykhaylyk , Aline F. Miller , Alberto Saiani Biomacromolecules DOI: 10.1021/acs.biomac.0c00229 Diamond Proposal Number(s): [12950, 15246] Open Access Show Abstract ▼ Abstract: Hydrogels’ hydrated fibrillar nature makes them the material of choice for the design and engineering of 3D-scaffolds for cell culture, tissue engineering and drug delivery applications. One particular class of hydrogels that has been the focus of significant research is self-assembling peptide hydrogels. In the present work we were interested in exploring how fibre-fibre edge interactions affect the self-assembly and gelation properties of amphipathic peptides. For this purpose we investigated two β-sheet forming peptides, FEFKFEFK (F8) and KFEFKFEFKK (KF8K), the latter one having the fibre edges covered by lysine residues. Our results showed that the addition of the two lysine residues did not affect the ability of the peptides to form β-sheet rich fibres provided that the overall charge carried by the two peptides was kept constant. It did though significantly reduce edge driven hydrophobic fibre-fibre associative interactions resulting in a reduced tendency for KF8K fibres to associate / aggregate laterally and form large fibre bundles and consequently network crosslinks. This effect resulted in the formation of hydrogels with lower moduli but faster dynamics. As a result KF8K fibres could be aligned only under high shear and at high concentration while F8 hydrogel fibres were found to align readily at low shear and low concentration. In addition F8 hydrogels were found to fragment at high concentration due to the high aggregation state stabilising the fibre bundles resulting in fibre breakage rather than disentanglement and alignment.	Apr 2020
I22-Small angle scattering & Diffraction	Hydrophobization of cellulose nanocrystals for aqueous colloidal suspensions and gels Rinat Nigmatullin , Marcus A. Johns , Juan C. Muñoz-García , Valeria Gabrielli , Julien Schmitt , Jesús Angulo , Yaroslav Z. Khimyak , Janet Lesley Scott , Karen J. Edler , Stephen J. Eichhorn Biomacromolecules DOI: 10.1021/acs.biomac.9b01721 Diamond Proposal Number(s): [17580] Show Abstract ▼ Abstract: Surface hydrophobization of cellulose nanomaterials has been used in the development of nanofiller reinforced polymer composites and formulations based on Pickering emulsions. Despite well known effect of hydrophobic domains on self assembly or association of water soluble polymer amphiphiles, very few studies have addressed the behavior of hydrophobized cellulose nanomaterials in aqueous media. In this study, we investigate the properties of hydrophobized cellulose nanocrystals (CNCs) and their self assembly and amphiphilic properties in suspensions and gels. CNCs of different hydrophobicity were synthesized from sulfated CNCs by coupling primary alkylamines of different alkyl chain lengths (6, 8 and 12 carbon atoms). The synthetic route permitted the retention of surface charge, ensuring good colloidal stability of hydrohobized CNCs in aqueous suspensions. We compare surface properties (surface charge, Zeta potential), hydrophobicity (water contact angle, microenvironment probing using pyrene fluorescence emission) and surface activity (tensiometry) of different hydrophobized CNCs and hydrophilic CNCs. Association of hydrophobized CNCs driven by hydrophobic effects is confirmed by X ray scattering (SAXS) and autofluorescent spectroscopy experiments. As a result of CNC association, CNCs suspensions/gels can be produced with a wide range of rheological properties depending on the hydrophobic/hydrophilic balance. In particular, sol gel transitions for hydrophobized CNCs occur at lower concentrations then hydrophilic CNCs and more robust gels are formed by hydrophobized CNCs. Our work illustrates that amphiphilic CNCs can complement associative polymers as modifiers of rheological properties of water based systems.	Jan 2020
I07-Surface & interface diffraction	Structural order in cellulose thin films prepared from a trimethylsilyl precursor Andrew O. F. Jones , Roland Resel , Benedikt Schrode , Eduardo Machado-Charry , Christian Rothel , Birgit Kunert , Ingo Salzmann , Eero Kontturi , David Reishofer , Stefan Spirk Biomacromolecules DOI: 10.1021/acs.biomac.9b01377 Diamond Proposal Number(s): [13569] Show Abstract ▼ Abstract: The biopolymer cellulose is investigated in terms of the crystallographic order within thin films. The films were prepared by spin coating of a trimethylsilyl cellulose precursor followed by an exposure to HCl vapors; two different source materials were used. Careful pre-characterization of the films was performed by infrared spectroscopy and atomic force microscopy. Subsequently, the films were investigated by grazing incidence X-ray diffraction using synchrotron radiation. The results showed broad diffraction peaks, indicating a rather short correlation length of the molecular packing in the range of a few nm. The analysis of the diffraction pattern was based on the known structures of crystalline cellulose, since the observed peak pattern was comparable to cellulose phase II and phase III. The dominant fraction of the film is formed by two different types of layers which are oriented parallel to the substrate surface. The stacking of the layers results in a one-dimensional crystallographic order with a defined interlayer distance of either 7.3 Å or 4.2 Å. As a consequence, two different preferred orientations of the polymer chains are observed. In both cases, polymer chain axes are aligned parallel to the substrate surface, and the orientation of the cellulose molecules are concluded to be either edge-on or flat-on. A minor fraction of the cellulose molecules form nanocrystals that are randomly distributed within the films. In this case, the molecular packing density was found to be smaller in comparison to the known crystalline phases of cellulose.	Nov 2019
B21-High Throughput SAXS	Conformation and aggregation of selectively pegylated and lipidated gastric peptide hormone human PYY 3-36 Valeria Castelletto , Ian W. Hamley , Jani Seitsonen , Janne Ruokolainen , Gemma Harris , Kathrin Bellmann-Sickert , Annette G. Beck-Sickinger Biomacromolecules DOI: 10.1021/acs.biomac.8b01209 Diamond Proposal Number(s): [14684, 17118] Show Abstract ▼ Abstract: The gastric peptide hormone human PYY3-36 is a target for the development of therapeutics, especially for treatment of obesity. The conformation and aggregation behaviour of PEGylated and lipidated derivatives of this peptide is examined using a combination of fluorescence dye assays, circular dichroism (CD) spectroscopy, analytical ultracentrifugation (AUC) measurements, small-angle x-ray scattering (SAXS) and cryogenic-transmission electron microscopy (cryo-TEM). The behaviour of two PYY3-36 derivatives lipidated (with octyl chains) in different positions is compared to that of two derivatives with PEG attached at different residues and to that of the native peptide. We find that, unexpectedly, PYY3-36 forms amyloid fibril structures above a critical aggregation concentration. Formation of these structures is suppressed by PEGylation or lipidation. PEGylation significantly reduces the (reversible) loss of α-helix content observed on heating PYY3-36. The PEG conjugates form mainly monomeric structures in solution, coiled coil formation and other aggregation presumably being sterically hindered by swollen PEG chains. However, some small aggregates are detected by AUC. In complete contrast, both of the two lipidated peptides show the formation of spherical micelle-like structures which are small oligomeric aggregates. Our findings show that PEGylation and lipidation are complementary strategies to tune the conformation and aggregation of the important gastric peptide hormone human PYY3-36.	Sep 2018

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