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124 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	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
B23-Circular Dichroism	Ligand-receptor interactions of galectin-9 and VISTA suppress human T lymphocyte cytotoxic activity Inna M. Yasinska , N. Helge Meyer , Stephanie Schlichtner , Rohanah Hussain , Giuliano Siligardi , Maxwell Casely-hayford , Walter Fiedler , Jasmin Wellbrock , Cloe Desmet , Luigi Calzolai , Luca Varani , Steffen M. Berger , Ulrike Raap , Bernhard F. Gibbs , Elizaveta Fasler-kan , Vadim V. Sumbayev Frontiers In Immunology 11 DOI: 10.3389/fimmu.2020.580557 Diamond Proposal Number(s): [24509, 20755, 21202] Open Access Show Abstract ▼ Abstract: Acute myeloid leukemia (AML), a blood/bone marrow cancer, is a severe and often fatal malignancy. AML cells are capable of impairing the anti-cancer activities of cytotoxic lymphoid cells. This includes the inactivation of natural killer (NK) cells and killing of T lymphocytes. Here we report for the first time that V-domain Ig-containing suppressor of T cell activation (VISTA), a protein expressed by T cells, recognizes galectin-9 secreted by AML cells as a ligand. Importantly, we found that soluble VISTA released by AML cells enhances the effect of galectin-9, most likely by forming multiprotein complexes on the surface of T cells and possibly creating a molecular barrier. These events cause changes in the plasma membrane potential of T cells leading to activation of granzyme B inside cytotoxic T cells, resulting in apoptosis.	Nov 2020
B23-Circular Dichroism	Chirality enhancement in macro-chiral liquid crystal nanoparticles Huanan Yu , Chris Welch , Wentao Qu , Christopher J. Schubert , Feng Liu , Giuliano Siligardi , Georg H. Mehl Materials Horizons 87 DOI: 10.1039/D0MH01274B Open Access Show Abstract ▼ Abstract: The amplification of molecular chirality by metal nanoparticles (NPs) is an important and rapidly evolving field in nanomaterial research with wide applications in smart materials, catalysis, and solvent–solute interactions. Here we present the results of the synthesis of gold nanoparticles (AuNPs) functionalized both with chiral ligands based on the binaphthol motif and with nematogenic groups (ChirAuLC). The materials were characterized chemically and the ratios between chiral groups and LC groups was determined. Synchrotron radiation circular dichroism (SRCD) and synchrotron based X-ray diffraction (XRD) studies show that the AuNPs favoured by the LC state arrange themselves into ordered columns and a helical superstructure appears in the mesophase of collective NPs. A specific focus has been the investigation of the chiral induction of ChirAuLC composites in two different nematic LC hosts. For a number of selected mixtures, the helical twisting power (HTP) of these NPs in systems was calculated from systematic optical observations based on optical polarizing microscopy (OPM). The experimental data show that the HTP of the investigated ChirAuLC composite is significantly larger than that of free “small molecule” chiral groups when dispersed in the same LC host and the chiral transfer efficiency of ChirAuLC is higher than NPs functionalized only with chiral groups (ChirAuNP). This is new and can be explained by a combination of a surface chirality and the domino effect of bound mesogens interacting with the bulk.	Sep 2020
B23-Circular Dichroism	Circular dichroism spectroscopy identifies the β-adrenoceptor agonist salbutamol as a direct inhibitor of tau filament formation in vitro David J. Townsend , Barbora Mala , Eleri Hughes , Rohanah Hussain , Giuliano Siligardi , Nigel J. Fullwood , David A. Middleton Acs Chemical Neuroscience DOI: 10.1021/acschemneuro.0c00154 Diamond Proposal Number(s): [17645, 24138] Show Abstract ▼ Abstract: Potential drug treatments for Alzheimer’s disease (AD) may be found by identifying compounds that block the assembly of the microtubule-associated protein tau into neurofibrillar tangles associated with neuron destabilisation and cell death. Here, a small library of structurally diverse compounds was screened in vitro for the ability to inhibit tau aggregation, using high-throughput synchrotron radiation circular dichroism (HT-SRCD) as a novel tool to monitor the structural changes in the protein as it assembles into filaments. The catecholamine epinephrine was found to be the most effective tau aggregation inhibitor of all 88 compounds screened. Subsequently, we tested chemically-similar phenolamine drugs from the β-adrenergic receptor (βAR) agonist class, using conventional circular dichroism spectroscopy, thioflavin T fluorescence and transmission electron microscopy. Two compounds, salbutamol and dobutamine, used widely in the treatment of respiratory and cardiovascular disease, impede the aggregation of tau in vitro. Dobutamine reduces both the rate and yield of tau filament formation over 24 hours, although it has little effect on the structural transition of tau into β-sheet structures over 24 hours. Salbutamol also reduces the yield and rate of filament formation, and additionally inhibits tau’s structural change into β-sheet rich aggregates. Salbutamol has a good safety profile and a half-life that facilitates permeation through the blood brain barrier and could represent an expediated approach to developing AD therapeutics. These results provide the motivation for in vivo evaluation of pre-existing β-adrenergic receptor agonists as a potential therapy for AD through the reduction of tau deposition in AD.	Jun 2020
B23-Circular Dichroism	Magnetically aligned membrane mimetics enabling comparable chiroptical and magnetic resonance spectroscopy studies Luke S. Evans , Rohanah Hussain , Giuliano Siligardi , Philip T. F. Williamson Biochimica Et Biophysica Acta (bba) - Biomembranes DOI: 10.1016/j.bbamem.2020.183343 Diamond Proposal Number(s): [16501, 14084] Show Abstract ▼ Abstract: Lipidic bicelles have been widely used for the analysis of integral membrane proteins where their spontaneous alignment in an magnetic field has been exploited for oriented sample solid-state NMR studies. Many of their physical properties however make them well suited to the analysis of membrane proteins by circular dichroism (CD) and synchrotron radiation circular dichroism (SRCD). In this paper we have identified bicelle compositions that permit comparable studies of integral membrane proteins by solid-state NMR, CD, and SRCD; complementary methods that can provide insights into protein structure and the interactions with drugs and other small molecules. Furthermore we have been able to identify bicelle compositions that allow the magnetic alignment of the bicelles at fields routinely available in magnetic CD instruments. This potentially provides a route to the preparation of samples for oriented CD that mitigates many of the issues associated with the preparation of mechanically aligned samples, although we demonstrate that the dynamics present within the system can complicate the analysis of such spectra.	May 2020
	Length-dependent electron spin polarization in oligopeptides and DNA Suryakant Mishra , Amit Kumar Mondal , Shubhadeep Pal , Tapan Kumar Das , Eilam Z. B. Smolinsky , Giuliano Siligardi , Ron Naaman The Journal Of Physical Chemistry C DOI: 10.1021/acs.jpcc.0c02291 Show Abstract ▼ Abstract: The effect of spin polarization in conduction and electric field-induced polarization was measured for double-stranded DNA oligonucleotides and oligopeptides of different lengths. The measurements were conducted using magnetic contact AFM, spin-dependent electrochemistry, spin-dependent polarization, and magnetoresistance studies. It was established that the spin-dependent conduction through chiral molecules depends on the voltage applied with a power of d, when d is larger than unity, and that there is a different voltage threshold for conducting each of the spin polarizations. In addition, there is no spin flipping during the conduction through the chiral system. The spin polarization depends linearly on the length, within the range of lengths studied, and it seems to scale like the optical activity. These results suggest the importance of the electric polarizability in the chiral-induced spin selectivity process.	Apr 2020

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