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129 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4, 5, 6, 7, 8 [Next/Last]

Instruments / Technical Area	Publication Details	Published
B23-Circular Dichroism	Modelling the adsorption of proteins to nanoparticles at the solid-liquid interface Mikhail Soloviev , Giuliano Siligardi , Danilo Roccatano , Enrico Ferrari Journal Of Colloid And Interface Science 162 DOI: 10.1016/j.jcis.2021.07.072 Diamond Proposal Number(s): [27024] Show Abstract ▼ Abstract: Hypothesis: We developed a geometrical model to determine the theoretical maximum number of proteins that can pack as a monolayer surrounding a spherical nanoparticle. We applied our new model to study the adsorption of receptor binding domain (RBD) of the SARS-CoV-2 spike protein to silica nanoparticles. Due to its abundance and extensive use in manufacturing, silica represents a reservoir where the virus can accumulate. It is therefore important to study the adsorption and the persistence of viral components on inanimate surfaces. Experiments: We used previously published datasets of nanoparticle-adsorbed proteins to validate the new model. We then used integrated experimental methods and Molecular Dynamics (MD) simulations to characterise binding of the RBD to silica nanoparticles and the effect of such binding on RBD structure. Findings: The new model showed excellent fit with existing datasets and, combined to new RBD-silica nanoparticles binding data, revealed a surface occupancy of 32% with respect to the maximum RBD packing theoretically achievable. Up to 25% of RBD’s secondary structures undergo conformational changes as a consequence of adsorption onto silica nanoparticles. Our findings will help developing a better understanding of the principles governing interaction of proteins with surfaces and can contribute to control the spread of SARS-CoV-2 through contaminated objects.	Jul 2021
B23-Circular Dichroism	Interaction of a short peptide with G-quadruplex-forming sequences: An SRCD and CD study Claudia Honisch , Eugenio Ragazzi , Rohanah Hussain , John Brazier , Giuliano Siligardi , Paolo Ruzza Pharmaceutics 13 DOI: 10.3390/pharmaceutics13081104 Diamond Proposal Number(s): [21245] Open Access Show Abstract ▼ Abstract: G-quadruplex (G4) forming DNA sequences were recently found to play a crucial role in the regulation of genomic processes such as replication, transcription and translation, also related to serious diseases. Therefore, systems capable of controlling DNA and RNA G-quadruplex structures would be useful for the modulation of various cellular events. In particular, peptides represent good candidates for targeting G-quadruplex structures, since they are easily tailored to enhance their functionality. In this work, we analyzed, by circular dichroism and synchrotron radiation circular dichroism spectroscopies, the interaction of a 25-residue peptide deriving from RHAU helicases (Rhau25) with three G-quadruplex-forming oligonucleotide sequences, in both sodium- and potassium-containing buffers, the most relevant monovalent cations in physiological conditions. The peptide displayed greater affinity for the G4 sequences adopting a parallel structure. However, it showed the ability to also interact with antiparallel or hybrid G-quadruplex structures, inducing a conformation conversion to the parallel structure. The stability of the oligonucleotide structure alone or in presence of the Rhau25 peptide was studied by temperature melting and UV denaturation experiments, and the data showed that the interaction with the peptide stabilized the conformation of oligonucleotide sequences when subjected to stress conditions.	Jul 2021
B23-Circular Dichroism	Free radicals and ROS induce protein denaturation by UV photostability assay Paolo Ruzza , Claudia Honisch , Rohanah Hussain , Giuliano Siligardi International Journal Of Molecular Sciences 22 DOI: 10.3390/ijms22126512 Diamond Proposal Number(s): [13661, 14857, 15931, 16643, 17413] Open Access Show Abstract ▼ Abstract: Oxidative stress, photo-oxidation, and photosensitizers are activated by UV irradiation and are affecting the photo-stability of proteins. Understanding the mechanisms that govern protein photo-stability is essential for its control enabling enhancement or reduction. Currently, two major mechanisms for protein denaturation induced by UV irradiation are available: one generated by the local heating of water molecules bound to the proteins and the other by the formation of reactive free radicals. To discriminate which is the likely or dominant mechanism we have studied the effects of thermal and UV denaturation of aqueous protein solutions with and without DHR-123 as fluorogenic probe using circular dichroism (CD), synchrotron radiation circular dichroism (SRCD), and fluorescence spectroscopies. The results indicated that the mechanism of protein denaturation induced by VUV and far-UV irradiation were mediated by the formation of reactive free radicals (FR) and reactive oxygen species (ROS). The development at Diamond B23 beamline for SRCD of a novel protein UV photo-stability assay based on consecutive repeated CD measurements in the far-UV (180–250 nm) region has been successfully used to assess and characterize the photo-stability of protein formulations and ligand binding interactions, in particular for ligand molecules devoid of significant UV absorption.	Jun 2021
B23-Circular Dichroism	CD imaging at high spatial resolution at Diamond B23 beamline: Evolution and applications Rohanah Hussain , Tamas Javorfi , Giuliano Siligardi Frontiers In Chemistry 9 DOI: 10.3389/fchem.2021.616928 Diamond Proposal Number(s): [26447] Open Access Show Abstract ▼ Abstract: Circular Dichroism imaging in the 190–650 nm spectral region pionered at Diamond Light Source B23 beamline, has been made possible by the highly collimated microbeam generated at the beamline and has been used to study the homogeneity of the supramolecular structures of thin films of chiral materials deposited on fused quartz substrates. This facility has been expanded with the installation of a Mueller Matrix Polarimeter, MMP, coupled to the beamlight, of which a preliminary data will be discussed. In the solid state, the measurement of CD related to the supramolecular structure is hampered by the presence of circular birefringence, linear dichroism, and linear birefringence that can only be evaluated using the MMP technique. The ability to characterize the chiroptical property of thin chiral films prepared under a variety of conditions and protocols such as drop cast, spin coating, spray at different temperatures and concentrations will enable the determination of the critical parameters for reproducible, uniform and homogeneous specimen preparation, which is the sine qua non for any commercial application. This is of particular importance for optoelectronic materials, but it can also be extended to a broad variety of materials with applications from biosensors to biological tissues.	Apr 2021
B23-Circular Dichroism	Graphene FET sensors for Alzheimer’s disease protein biomarker clusterin detection Theodore Bungon , Carrie Haslam , Samar Damiati , Benjamin O’driscoll , Toby Whitley , Paul Davey , Giuliano Siligardi , Jerome Charmet , Shakil A. Awan Frontiers In Molecular Biosciences 8 DOI: 10.3389/fmolb.2021.651232 Diamond Proposal Number(s): [24459] Open Access Show Abstract ▼ Abstract: We report on the fabrication and characterisation of graphene field-effect transistor (GFET) biosensors for the detection of Clusterin, a prominent protein biomarker of Alzheimer’s disease (AD). The GFET sensors were fabricated on Si/SiO2 substrate using photolithographic patterning and metal lift-off techniques with evaporated chromium and sputtered gold contacts. Raman Spectroscopy was performed on the devices to determine the quality of the graphene. The GFETs were annealed to improve their performance before the channels were functionalized by immobilising the graphene surface with linker molecules and anti-Clusterin antibodies. Concentration of linker molecules was also independently verified by absorption spectroscopy using the highly collimated micro-beam light of Diamond B23 beamline. The detection was achieved through the binding reaction between the antibody and varying concentrations of Clusterin antigen from 1 to 100 pg/mL, as well as specificity tests using human chorionic gonadotropin (hCG), a glycoprotein risk biomarker of certain cancers. The GFETs were characterized using direct current (DC) 4-probe electrical resistance (4-PER) measurements, which demonstrated a limit of detection of the biosensors to be ∼ 300 fg/mL (4 fM). Comparison with back-gated Dirac voltage shifts with varying concentration of Clusterin show 4-PER measurements to be more accurate, at present, and point to a requirement for further optimisation of the fabrication processes for our next generation of GFET sensors. Thus, we have successfully fabricated a promising set of GFET biosensors for the detection of Clusterin protein biomarker. The developed GFET biosensors are entirely generic and also have the potential to be applied to a variety of other disease detection applications such as Parkinson’s, cancer, and cardiovascular.	Mar 2021
B23-Circular Dichroism	Characterization of insulin mucoadhesive buccal films: Spectroscopic analysis and in vivo evaluation Maram Diab , Al-Sayed Sallam , Imad Hamdan , Randa Mansour , Rohanah Hussain , Giuliano Siligardi , Nidal Qinna , Enam Khalil Symmetry 13 DOI: 10.3390/sym13010088 Diamond Proposal Number(s): [19787] Open Access Show Abstract ▼ Abstract: Insulin mucoadhesive buccal films (MBF) are a noninvasive insulin delivery system that offers an advantageous alternative route of administration to subcutaneous injection. One major concern in the formulation of insulin MBF is the preservation of an insulin secondary structure in the presence of the other film components. Buccal films were formulated using chitosan, glycerin, and L-arginine. The MBF-forming solutions (MBF-FS) and the films (MBF) were examined for their chemical and structural stability and for their in vivo activity. Enzyme-Linked Immunosorbent Assay (ELISA) of the insulin-loaded MBF showed that each individualized unit dose was at least loaded with 80% of the insulin theoretical dose. Results of Synchrotron Radiation Circular Dichroism (SRCD) measurements revealed that MBF-FS retained the α-helices and β–sheets conformations of insulin. Fourier transform infrared (FTIR)-microspectroscopy (FTIR-MS) examination of insulin MBF revealed the protective action of L-arginine on insulin structure by interacting with chitosan and minimizing the formation of an unordered structure and β-strand. A blood glucose-lowering effect of insulin MBF was observed in comparison with subcutaneous (S.C) injection using a rat model. As a result; chitosan-based MBFs were formulated and characterized using SRCD and FTIR-MS techniques. Furthermore, the results of in vivo testing suggested the MBFs as a promising delivery system for insulin.	Jan 2021
B23-Circular Dichroism	Natural optical activity as the origin of the large chiroptical properties in π-conjugated polymer thin films Jessica Wade , James N. Hilfiker , Jochen R. Brandt , Letizia Liirò-Peluso , Li Wan , Xingyuan Shi , Francesco Salerno , Seán T. J. Ryan , Stefan Schöche , Oriol Arteaga , Tamas Javorfi , Giuliano Siligardi , Cheng Wang , David B. Amabilino , Peter H. Beton , Alasdair J. Campbell , Matthew J. Fuchter Nature Communications 11 DOI: 10.1038/s41467-020-19951-y Diamond Proposal Number(s): [20376, 21822] Open Access Show Abstract ▼ Abstract: Polymer thin films that emit and absorb circularly polarised light have been demonstrated with the promise of achieving important technological advances; from efficient, high-performance displays, to 3D imaging and all-organic spintronic devices. However, the origin of the large chiroptical effects in such films has, until now, remained elusive. We investigate the emergence of such phenomena in achiral polymers blended with a chiral small-molecule additive (1-aza[6]helicene) and intrinsically chiral-sidechain polymers using a combination of spectroscopic methods and structural probes. We show that – under conditions relevant for device fabrication – the large chiroptical effects are caused by magneto-electric coupling (natural optical activity), not structural chirality as previously assumed, and may occur because of local order in a cylinder blue phase-type organisation. This disruptive mechanistic insight into chiral polymer thin films will offer new approaches towards chiroptical materials development after almost three decades of research in this area.	Dec 2020
B23-Circular Dichroism	Mapping the chiroptical properties of local domains in thin films of chiral silicon phthalocyanines by CD imaging Dora-Maria Rasadean , Tiberiu-Marius Gianga , Tamas Javorfi , Rohanah Hussain , Giuliano Siligardi , G. Dan Pantos Molecules 25 DOI: 10.3390/molecules25246048 Diamond Proposal Number(s): [23955, 20441, 26447] Open Access Show Abstract ▼ Abstract: The first example of uniformly chiral thin films of silicon phthalocyanines (SiPcs) are reported. The local domains of the films are mapped using circular dichroism (CD) imaging (CDi) technique available at the Diamond B23 beamline. The CDi allowed us to increase the spatial resolution up to 525× when compared with benchtop spectrometers. The results indicate formation on-surface of chiral and stable supramolecular assemblies with homogenous distribution. Chemical functionalization and solvent choice for deposition allow controllable chiroptical properties to be obtained. The method and technique reported in this work could be applied to prepare and characterize a wide variety of chiral thin films.	Dec 2020
B23-Circular Dichroism	Allosteric inhibition of human exonuclease1 (hExo1) through a novel extended β-sheet conformation Aminu Argungu Umar , Susan Liddell , Rohanah Hussain , Giuliano Siligardi , Gemma Harris , Stephen Carr , Karishma Asiani , Darren M. Gowers , Mark Odell , David J. Scott Biochimica Et Biophysica Acta (bba) - General Subjects 1864 DOI: 10.1016/j.bbagen.2020.129730 Diamond Proposal Number(s): [15313, 14658, 14430] Show Abstract ▼ Abstract: Background: Human Exonuclease1 (hExo1) participates in the resection of DNA double-strand breaks by generating long 3′-single-stranded DNA overhangs, critical for homology-based DNA repair and activation of the ATR-dependent checkpoint. The C-terminal region is essential for modulating the activity of hExo1, containing numerous sites of post-translational modification and binding sites for partner proteins. Methods: Analytical Ultracentrifugation (AUC), Dynamic Light Scattering (DLS), Circular Dichroism (CD) spectroscopy and enzymatic assays. Results: AUC and DLS indicates the C-terminal region has a highly extended structure while CD suggest a tendency to adopt a novel left-handed β-sheet structure, together implying the C-terminus may exhibit a transient fluctuating structure that could play a role in binding partner proteins known to regulate the activity of hExo1. Interaction with 14–3-3 protein has a cooperative inhibitory effect upon DNA resection activity, which indicates an allosteric transition occurs upon binding partner proteins. Conclusions: This study has uncovered that hExo1 consist of a folded N-terminal nuclease domain and a highly extended C-terminal region which is known to interact with partner proteins that regulates the activity of hExo1. A positively cooperative mechanism of binding allows for stringent control of hExo1 activity. Such a transition would coordinate the control of hExo1 by hExo1 regulators and hence allow careful coordination of the process of DNA end resection.	Dec 2020
B23-Circular Dichroism	Diamond B23 CD imaging of thin films of chiral materials or achiral polymers coated with chiral molecules Rohanah Hussain , Tamas Javorfi , Charlotte S. Hughes , Harini Sriram , Rajamani Lashminarayanan , Giuliano Siligardi Symmetry 12 DOI: 10.3390/sym12111847 Diamond Proposal Number(s): [8893, 14842, 13518] Open Access Show Abstract ▼ Abstract: The novel vertical sample chamber, developed at the B23 beamline for synchrotron radiation circular dichroism (SRCD), has enabled the Diamond User community to conduct different types of experiments from high throughput CD of protein and DNA folding using 96-well multiplates to CD imaging at high spatial resolution. Here, we present the application of CD imaging to large areas of achiral polymer PVA films doped with D-dopa to assess the chiral homogeneity of the film preparation with potential antimicrobial property. Synopsis: CDi application of Diamond B23 SRCD beamline.	Nov 2020

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