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141 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
B21-High Throughput SAXS B23-Circular Dichroism	Conformational analysis and interaction of the Staphylococcus aureus transmembrane peptidase AgrB with its AgrD propeptide substrate Philip Bardelang , Ewan J. Murray , Isobel Blower , Sara Zandomeneghi , Alice Goode , Rohanah Hussain , Divya Kumari , Giuliano Siligardi , Katsuaki Inoue , Jeni Luckett , James Doutch , Jonas Emsley , Weng C. Chan , Philip Hill , Paul Williams , Boyan B. Bonev Frontiers In Chemistry 11 DOI: 10.3389/fchem.2023.1113885 Diamond Proposal Number(s): [5098, 12923, 13185, 13634, 15146] Open Access Show Abstract ▼ Abstract: Virulence gene expression in the human pathogen, S. aureus is regulated by the agr (accessory gene regulator) quorum sensing (QS) system which is conserved in diverse Gram-positive bacteria. The agr QS signal molecule is an autoinducing peptide (AIP) generated via the initial processing of the AgrD pro-peptide by the transmembrane peptidase AgrB. Since structural information for AgrB and AgrBD interactions are lacking, we used homology modelling and molecular dynamics (MD) annealing to characterise the conformations of AgrB and AgrD in model membranes and in solution. These revealed a six helical transmembrane domain (6TMD) topology for AgrB. In solution, AgrD behaves as a disordered peptide, which binds N-terminally to membranes in the absence and in the presence of AgrB. In silico, membrane complexes of AgrD and dimeric AgrB show non-equivalent AgrB monomers responsible for initial binding and for processing, respectively. By exploiting split luciferase assays in Staphylococcus aureus, we provide experimental evidence that AgrB interacts directly with itself and with AgrD. We confirmed the in vitro formation of an AgrBD complex and AIP production after Western blotting using either membranes from Escherichia coli expressing AgrB or with purified AgrB and T7-tagged AgrD. AgrB and AgrD formed stable complexes in detergent micelles revealed using synchrotron radiation CD (SRCD) and Landau analysis consistent with the enhanced thermal stability of AgrB in the presence of AgrD. Conformational alteration of AgrB following provision of AgrD was observed by small angle X-ray scattering from proteodetergent micelles. An atomistic description of AgrB and AgrD has been obtained together with confirmation of the AgrB 6TMD membrane topology and existence of AgrBD molecular complexes in vitro and in vivo.	May 2023
B23-Circular Dichroism	Mueller matrix polarimetry on cyanine dye J-aggregates Samuel R. Clowes , Dora M. Răsădean , Tiberiu-M. Gianga , Tamas Javorfi , Rohanah Hussain , Giuliano Siligardi , G. Dan Pantos Molecules 28 DOI: 10.3390/molecules28041523 Diamond Proposal Number(s): [29075, 31797] Open Access Show Abstract ▼ Abstract: Cyanine dyes are known to form H- and J-aggregates in aqueous solutions. Here we show that the cyanine dye, S0271, assembles in water into vortex induced chiral J-aggregates. The chirality of the J-aggregates depends on the directionality of the vortex. This study utilised both conventional benchtop CD spectropolarimeters and Mueller matrix polarimetry. It was found that J-aggregates have real chirality alongside linear dichroism and linear and circular birefringence. We identify the factors that are key to the formation of metastable chiral J-aggregates and propose a mechanism for their assembly.	Feb 2023
B23-Circular Dichroism	Self‐assembly of chiral diketopyrrolopyrrole chromophores giving supramolecular chains in monolayers and twisted microtapes Joshua Humphreys , C. Elizabeth Killalea , Flavia Pop , E. Stephen Davies , Giuliano Siligardi , David B. Amabilino Chirality 9 DOI: 10.1002/chir.23539 Open Access Show Abstract ▼ Abstract: Chiral diketopyrrolopyrroles appended with enantiomeric ethyl lactate functions through an ether linkage to the aryl backbone of the chromophore were synthesized via the Mitsunobu reaction. The molecules have good solubility and excellent optical properties, high molar absorption coefficients, and fluorescence quantum yields. Helical aggregates with circular dichroism arising from the supramolecular arrangement are seen in both solution and thin films, and the aggregates also display circularly polarized luminescence (glum ≈ ±0.1). The molecules assemble to give monolayers on graphite and precipitate from solution forming supramolecular twisted tapes hundreds of microns long.	Feb 2023
B23-Circular Dichroism	Modulating the poly-l-lysine structure through the control of the protonation–deprotonation state of l-lysine Luigi Stagi , Martina Sini , Davide Carboni , Roberto Anedda , Giuliano Siligardi , Tiberiu-Marius Gianga , Rohanah Hussain , Plinio Innocenzi Scientific Reports 12 DOI: 10.1038/s41598-022-24109-5 Diamond Proposal Number(s): [31392] Open Access Show Abstract ▼ Abstract: Designing the architecture of L-lysine-based polymeric structures is a highly challenging task that requires careful control of the amino acid reactive groups. Conventional processes to obtain branched polylysine need several steps and the addition of specific catalysts. In the present work, to gain a better understanding and control of the formation of L-lysine-based polymers, we have investigated the correlation between the protonation state of L-lysine and the corresponding hydrothermally grown structures. The samples have been characterized by combining optical spectroscopies, such as UV–Vis, fluorescence, and synchrotron radiation circular dichroism with structural analysis by Nuclear Magnetic Resonance, Fourier Transform Infrared spectroscopy, and dynamic light scattering. We have observed that aqueous precursor solutions with alkaline pHs promote the formation of branched structures. In contrast, high pHs favour the reactivity of the ε-amino groups leading to linear structures, as shown by circular dichroism analyses. On the other hand, acidic conditions trigger the branching of the amino acid. Interestingly, the polymeric forms of L-lysine emit in the blue because the increasing number of intermolecular hydrogen bonds promote the intermolecular charge transfer responsible for the emission. Understanding the correlation between the L-lysine charged states and the polymeric structures that could form controlling the protonation–deprotonation states of the amino acid opens the route to a refined design of polypeptide systems based on L-lysine.	Nov 2022
B23-Circular Dichroism	A conformational switch controlling the toxicity of the prion protein Karl Frontzek , Marco Bardelli , Assunta Senatore , Anna Henzi , Regina R. Reimann , Seden Bedir , Marika Marino , Rohanah Hussain , Simon Jurt , Georg Meisl , Mattia Pedotti , Federico Mazzola , Giuliano Siligardi , Oliver Zerbe , Marco Losa , Tuomas Knowles , Asvin Lakkaraju , Caihong Zhu , Petra Schwarz , Simone Hornemann , Matthew G. Holt , Luca Simonelli , Luca Varani , Adriano Aguzzi Nature Structural & Molecular Biology 379 DOI: 10.1038/s41594-022-00814-7 Diamond Proposal Number(s): [19680] Open Access Show Abstract ▼ Abstract: Prion infections cause conformational changes of the cellular prion protein (PrPC) and lead to progressive neurological impairment. Here we show that toxic, prion-mimetic ligands induce an intramolecular R208-H140 hydrogen bond (‘H-latch’), altering the flexibility of the α2–α3 and β2–α2 loops of PrPC. Expression of a PrP2Cys mutant mimicking the H-latch was constitutively toxic, whereas a PrPR207A mutant unable to form the H-latch conferred resistance to prion infection. High-affinity ligands that prevented H-latch induction repressed prion-related neurodegeneration in organotypic cerebellar cultures. We then selected phage-displayed ligands binding wild-type PrPC, but not PrP2Cys. These binders depopulated H-latched conformers and conferred protection against prion toxicity. Finally, brain-specific expression of an antibody rationally designed to prevent H-latch formation prolonged the life of prion-infected mice despite unhampered prion propagation, confirming that the H-latch is an important reporter of prion neurotoxicity.	Aug 2022
B23-Circular Dichroism	Imaging deposition-dependent supramolecular chiral organisation C. Elizabeth Killalea , Mario Samperi , Giuliano Siligardi , David B. Amabilino Chemical Communications 9 DOI: 10.1039/D1CC06790G Diamond Proposal Number(s): [22017, 26044] Open Access Show Abstract ▼ Abstract: Thin films of a chiral diketopyrrolopyrrole derivative were imaged with spatially-defined Mueller Matrix Polarimetry, focussing on the Circular Dichroism signal, giving unique insight into the impact that deposition techniques and thermal annealing can have on chiral supramolecular structures in the solid state, where homogeneity was observed for spun-coated films while drop-coating afforded chiroptical diversity in the material, a feature invisible to absorption spectroscopy or optical microscopy.	Mar 2022
B23-Circular Dichroism I02-Macromolecular Crystallography	Crystal structure and metal binding properties of the periplasmic iron component EfeM from Pseudomonas syringae EfeUOB/M iron-transport system Mohan B. Rajasekaran , Rohanah Hussain , Giuliano Siligardi , Simon C. Andrews , Kimberly A. Watson Biometals 66 DOI: 10.1007/s10534-022-00389-2 Open Access Show Abstract ▼ Abstract: EfeUOB/M has been characterised in Pseudomonas syringae pathovar. syringae as a novel type of ferrous-iron transporter, consisting of an inner-membrane protein (EfeUPsy) and three periplasmic proteins (EfeOPsy, EfeMPsy and EfeBPsy). The role of an iron permease and peroxidase function has been identified for the EfeU and EfeB proteins, respectively, but the role of EfeO/M remains unclear. EfeMPsy is an ‘M75-only’ EfeO-like protein with a C-terminal peptidase-M75 domain (EfeOII/EfeM family). Herein, we report the 1.6 Å resolution crystal structure of EfeMPsy, the first structural report for an EfeM component of P. syringae pv. syringae. The structure possesses the bi-lobate architecture found in other bacterial periplasmic substrate/solute binding proteins. Metal binding studies, using SRCD and ICP-OES, reveal a preference of EfeMPsy for copper, iron and zinc. This work provides detailed knowledge of the structural scaffold, the metal site geometry, and the divalent metal binding potential of EfeM. This work provides crucial underpinning for a more detailed understanding of the role of EfeM/EfeO proteins and the peptidase-M75 domains in EfeUOB/M iron uptake systems in bacteria.	Mar 2022
B23-Circular Dichroism	Spatially resolved chiroptical study of thin films of benzo[1,2‐ b :4,5‐ b’]dithiophene‐based oligothiophenes by synchrotron radiation electronic circular dichroism imaging (SR‐ECDi) technique Gianluigi Albano , Marcin Gorecki , Tamas Javorfi , Rohanah Hussain , Giuliano Siligardi , Gennaro Pescitelli , Lorenzo Di Bari Aggregate 10 DOI: 10.1002/agt2.193 Diamond Proposal Number(s): [17621] Open Access Show Abstract ▼ Abstract: The study of the chiroptical properties of thin-film samples of two chiral benzo[1,2-b:4,5-b’]dithiophene-based oligothiophenes with optoelectronic properties was carried out at Diamond B23 beamline using the synchrotron radiation electronic circular dichroism imaging (SR-ECDi) facility. The experimental results support the hypothesis that the non-reciprocal circularly polarized absorption observed in these materials is due to the combined linear dichroism and linear birefringence contributions. The mapping at 50-µm spatial resolution revealed that several species coexist in the mesoscopic chiral domains likely due to different aggregated phases, which were identified in the films by SR-ECDi but could not be detected with benchtop ECD instruments	Mar 2022
B23-Circular Dichroism	Effect of trehalose and ceftriaxone on the stability of aggregating-prone tau peptide containing PHF6* sequence: an SRCD study Claudia Honisch , Federica Torni , Rohanah Hussain , Paolo Ruzza , Giuliano Siligardi International Journal Of Molecular Sciences 23 DOI: 10.3390/ijms23062932 Diamond Proposal Number(s): [23764, 25489] Open Access Show Abstract ▼ Abstract: The tau protein, a soluble protein associated with microtubules, which is involved in the assembly and stabilization of cytoskeletal elements, was found to form neurofibrillary tangles in different neurodegenerative diseases. Insoluble tau aggregates were observed to be organized in paired helical filaments (PHFs) and straight filaments (SFs). Recently, two small sequences (306–311 and 275–280) in the microtubule-binding region (MTBR), named PHF6 and PHF6, respectively, were found to be essential for tau aggregation. Since a possible therapeutic approach consists of impairing amyloid formation either by stabilizing the native proteins or reducing the level of amyloid precursors, here we use synchrotron radiation circular dichroism (SRCD) at Diamond B23 beamline to evaluate the inhibitory effects of two small molecules, trehalose and ceftriaxone, against the aggregation of a small peptide containing the PHF6 sequence. Our results indicate that both these molecules, ceftriaxone and trehalose, increased the stability of the peptide toward aggregation, in particular that induced by heparin. With trehalose being present in many fruits, vegetables, algae and processed foods, these results support the need to investigate whether a diet richer in trehalose might exert a protective effect toward pathologies linked to protein misfolding.	Mar 2022
B23-Circular Dichroism	Self‐assembly of gold nanoparticles into an adjustable plasmonic 3D lattice using Janus‐type forked mesogenic ligands Yang-Yang Zhao , Yu Cao , Giuliano Siligardi , Georg H. Mehl , Feng Liu , Goran Ungar Chemistry – An Asian Journal DOI: 10.1002/asia.202200057 Diamond Proposal Number(s): [24437, 28686] Show Abstract ▼ Abstract: We report the formation of a 3D body-centred self-assembled superlattice of gold nanoparticles whose interparticle gap, and hence its plasmonic properties, are adjustable exclusively in the xy -plane. Thus, even though the particles are spherical, their anisotropic packing generates tailorable plasmonic dichroism. The gold nanoparticles are coated with forked ligands containing two mesogens: either two cholesterols (“twin”), one cholesterol and one azobenzene (“Janus”), or a mixture of the two. Beside the body-centered arrangement of gold nanoparticles, the structure also contains unusual two-dimensionally modulated smectic-like layers of mesogens in an egg-box geometry. Moreover, the presence of azobenzene mesogens allows the superlattice to be melted through UV-induced photo-isomerization; the process is reversible displaying low fatigue on repeated cycling.	Feb 2022

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