B23-Circular Dichroism
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Xi
Lei
,
Sibo
Peng
,
Nijas
Aliu
,
Rohanah
Hussain
,
Giuliano
Siligardi
,
Tiberiu-Marius
Gianga
,
Xin
Jin
,
Sabrina
Ruggiero
,
Shilpa
Chokshi
,
Luca
Urbani
,
Bernhard F.
Gibbs
,
Elena
Klenova
,
Gurprit S.
Lall
,
Gabriela
Dekany
,
Dietmar
Cholewa
,
Steffen M.
Berger
,
Maryam
Abooali
,
Inna M.
Yasinska
,
Song
Xu
,
Elizaveta
Fasler-Kan
,
Vadim V.
Sumbayev
Diamond Proposal Number(s):
[36941, 38189]
Abstract: Human cancer cells and malignant tumours operate immune evasion machinery, which consists of a set of cross-linked biochemical pathways that suppress the activities of immune cells, such as cytotoxic T cells and natural killer cells. Recent evidence demonstrated that the immune evasion machinery operated by human cancer cells is self-sustaining. However, the mechanisms underlying self-regulation of cancer immune evasion networks remain to be understood. Here we report for the very first time that the cell surface receptor CD44 acts as an enhancer of immune evasion activity in human cancer cells rather than an immune checkpoint per se. Furthermore, upon interaction with galectin-9, CD44 was found to alter cell membrane potential and induce the secretion of TGF-β. Secreted TGF-β displays autocrine and paracrine activities following TGF-β receptor (TGFBR) engagement, which was shown to then activate the Smad3 transcriptional pathway. CD44 complexed to galectin-9 allosterically enhances activity of the TGFBR complex and this was shown to substantially amplify the expression of immune checkpoint proteins crucially associated with suppressing the anti-cancer activities of cytotoxic lymphoid cells. We also demonstrated that this is a fundamental pathway used by human embryos to prevent immune rejection and by innate immune cells to facilitate anti-bacterial innate immune response. Cancer cells and malignant tumours hijack and successfully adapt this fundamental pathway to escape immune surveillance and suppress anti-cancer immune reactions. As such, this autocrine loop allows for the self-regulation of immune evasion networks operated by cancer cells and can be considered as a promising target for highly efficient immunotherapy of cancer.
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Nov 2026
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B23-Circular Dichroism
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Diamond Proposal Number(s):
[41438]
Open Access
Abstract: Understanding the interplay between different forms of chirality in organic materials is critical for tuning and optimizing their (chir)optical properties. There is a growing interest in chiral chromophores such as bay-substituted perylene diimides (PDIs) due to their intrinsic helicity (M/P) which, at a higher level of organization, can also generate supramolecular chirality (Ms/Ps). The relationship between helical and supramolecular chirality governs interchromophore coupling, rotatory strengths, and subsequently circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. Herein, we report the first PDI dimers that match helical and supramolecular chirality, e.g., PP–Ps. In agreement with theory, this chiral synergy contributes to enhanced CD and broadband CPL with high CPL brightness, properties of significant value for optical filtering in next-generation chiral sensors and displays.
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Sep 2026
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B23-Circular Dichroism
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Claudio
Fontanesi
,
Andrea
Severini
,
Marianna
Burello
,
Alberta
Carella
,
Marco
Bonechi
,
Fabrizio
Roncaglia
,
Massimo
Innocenti
,
Francesco
Rossella
,
Suryakant
Mishra
,
Andrew Crandall
Jones
,
Rohanah
Hussain
,
Giuliano
Siligardi
Diamond Proposal Number(s):
[45826]
Open Access
Abstract: Enantiorecognition is a fundamental process in bioscience, ruling most life-related processes. This work focuses on the physics underlying chiral recognition, suggesting that the electron-spin/molecular-handedness interaction plays an important role here. Results obtained exploiting three complementary experimental techniques are compared, where metal surfaces are functionalized using a chiral porphyrin (cPorf): (1) cyclic voltammetry is used to probe the handedness of the electrode surface exploiting a chiral redox couple; (2) spin-dependent electrochemistry measurements were performed using a ferromagnetic electrode as spin injector; (3) magnetoconductive atomic force microscopy measurements proved that the charge transport through cPorf bundles adsorbed on a nickel surface is spin-polarized (spin polarization percentage, SP%, ranging between 20% and 50%). Mueller matrix polarimetry (MMP) spectra confirmed that the electronic circular dichroism of cPorf in solid-state thin films is not merely apparent but is true. The overall experimental results suggest that spin plays a fundamental role in the enantiorecognition process, as a possible manifestation of the Naaman−Waldeck chiral-induced spin selectivity effect.
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Sep 2026
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B23-Circular Dichroism
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Carolina
Díaz-Norambuena
,
Juan Manuel
Moreno-Naranjo
,
David
Reger
,
Giuliano
Siligardi
,
César
Ray
,
Jessica
Colligan
,
Florencio
Moreno
,
Beatriz L.
Maroto
,
Gilles
Muller
,
Jorge
Bañuelos
,
Matthew J.
Fuchter
,
Santiago De La
Moya
Open Access
Abstract: Chiral organic thin films are emerging as key materials in advanced optoelectronic and chiroptical technologies, where the straightforward, solution-processed fabrication of chiroptically active neat films from small π-conjugated helical molecules is highly desirable for sustainable and scalable device integration. However, in such densely packed systems, the intrinsic chiroptical response is often compromised by macroscopic anisotropies (e.g., linear dichroism and birefringence) and aggregation-induced effects, which obscure genuine molecular signatures and induce or alter chiral exciton coupling. Here, we demonstrate that a readily accessible and conformationally flexible helically chiral boron-dipyrromethene dimer (helicoBODIPY) platform enables the reproducible fabrication of robust solution-processed neat thin films exhibiting a unique behavior: chiroptical isotropy while retaining the characteristic molecular chiroptical response arising from intramolecular chiral exciton coupling. Through systematic structural tuning, these systems exhibit enhanced electronic circular dichroism (ECD) and circularly polarized luminescence in solution. Remarkably, the sharp ECD couplets and absorption dissymmetry values measured in the corresponding films closely reproduce those observed in solution, indicating minimal contribution from anisotropic contributions and negligible perturbation of excitonic interactions in the condensed phase. These unique findings point to helically flexible helicoBODIPYs as an excellent molecular platform that bridges molecular design and thin-film performance, offering a potential tool for disentangling aggregation effects in chiral thin films and advancing the rational design of chiral organic materials with predictable chiroptical properties.
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Aug 2026
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B23-Circular Dichroism
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Abstract: CD spectroscopy is the essential tool to quickly ascertain in the far UV region the global conformational changes, the secondary structure content and protein folding and in the near UV region the local tertiary structure changes probed by the local environment of the aromatic side chains, prosthetic groups (hemes, flavones, carotenoids), the dihedral angle of disulphide bonds and the ligand chromophore moieties, the latter occurring as a result of protein–ligand binding interaction. Qualitative and quantitative investigations into ligand binding interactions in both the far-UV and near-UV regions using CD spectroscopy provide unique and direct information whether induced conformational changes upon ligand binding occur and of what nature that are unattainable with other techniques such as fluorescence, ITC, SPR, and AUC. This chapter provides an overview of how to perform circular dichroism (CD) experiments, detailing methods, hints, and tips for successful CD measurements. Descriptions of different experimental designs are discussed using CD to investigate ligand-binding interactions. This includes standard qualitative CD measurements conducted in both single-measurement mode and high-throughput 96-well plate mode, CD titrations, and UV protein denaturation assays with and without ligand. The highly collimated microbeam available at B23 beamline for synchrotron radiation circular dichroism (SRCD) at diamond light source (DLS) offers many advantages to benchtop instruments. The synchrotron light source is ten times brighter than a standard xenon arc light source of benchtop instruments. The small diameter of the synchrotron beam can be up to 160 times smaller than that of benchtop light beams has enabled the use of small aperture cuvette cells and flat capillary tubes reducing substantially the amount of volume sample to be investigated. Methods, hints and tips, and golden rules to measure good quality, artifact-free SRCD and CD data will be described in this chapter in particular for the study protein–ligand interactions and protein photostability.
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Jul 2026
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B21-High Throughput SAXS
B23-Circular Dichroism
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Diamond Proposal Number(s):
[39005, 42397, 40578, 42398]
Open Access
Abstract: Aspergillus fumigatus infections are a major yet often neglected global health challenge magnified by a growing at-risk population, limited treatment options, and the emergence of drug-resistant strains. Regulation of the DNA damage response (DDR) by ADP-ribosylation signalling has recently emerged as an important feature of fungal pathogenesis, but the underlying mechanisms remain largely elusive. Here we present a comprehensive phylogenetic and functional characterisation of Af-PARP1, the A. fumigatus PARP homologue. Our data reveal Af-PARP1 as a DNA-dependent poly(ADP-ribosyl)transferase with unique domain architecture, DNA damage selectivity, and activation dynamics distinct from its mammalian and plant homologues. We show that the fungal specific BRCT domain plays a crucial role in both damage recognition and ADP-ribosylation signal establishment. Collectively, our findings reveal a divergence in DDR-associated ADP-ribosylation specific to fungi, highlighting the potential of this signalling pathway as target for antifungal therapy.
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Jul 2026
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B23-Circular Dichroism
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Diamond Proposal Number(s):
[33191, 39995]
Open Access
Abstract: The orientation of π-conjugated polymers impacts organic solar cells (OSCs). Owing to their intrinsic anisotropy, when fully extended, their alignment is expected to boost device performances. While various strategies have been used to control orientation, in this work we present a simple, yet effective, approach to enforce polymer alignment at the interface with an electron transport layer in a bulk heterojunction OSC. As little as 3 weight % of an additive in the photoactive layer gives interface adsorption and polymer oredering. In doing so, light absorption and charge generation across the photoactive area are optimized, especially for thinner films. We demonstrate that the PM6:Y6 photoactive layer exhibits superior photovoltaic performance when blended with enantiomerically pure 1,1’-bi-2-naphthol (BINOL) at film thicknesses as low as 40 nm under otherwise identical conditions. BINOL promotes short range molecular order without compromising the phase segregation of PM6:Y6 when blade-coated. Overall, BINOL enhances charge transport and reduces recombination losses by interfacial adsorption of this and other hydroxyl-containing additives that induce polymer alignment. What results are higher power conversion efficiencies (PCE) with minimum materials use, which support a potentially scalable and cost-efficient OSC fabrication. Our strategy not only offers a straightforward route to enhance device performance but also provides new insights into the role of small molecules in influencing the structural order of organic semiconducting films at interfaces.
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Jul 2026
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B23-Circular Dichroism
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Diamond Proposal Number(s):
[36727]
Open Access
Abstract: We report a new chiral indaceno[1,2-b:5,6-b′]dithiophene bis-thiophenylpropynone (IDT-TPO) dye exhibiting very noticeable chiroptical properties in thin films. While freshly prepared samples are ECD-silent, aging triggers a giant dichroic response, with ellipticity values reaching approximately 18,000 mdeg, among the highest reported to date for thin films of chiral organic dyes as neat materials. This amplification is accompanied by an unusual flattening of the main UV-Vis absorption band, and the combination of these effects produces very large gabs values (exceeding 0.1). A thorough investigation, combining microscopy and spatially resolved chiroptical techniques with time-dependent density functional theory (TD-DFT) calculations, reveals that the intense chiroptical activity arises primarily from the consistent formation of right-handed three-dimensional (3D) helical architectures. Notably, the degree of circular polarization exhibits a non-monotonic dependence on film thickness: the maximum ECD intensity was found for a thinner film, rather than for the thickest one. This behavior is particularly promising for optoelectronic applications requiring efficient chiroptical responses in relatively thin active layers.
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Jul 2026
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B23-Circular Dichroism
I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
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Diamond Proposal Number(s):
[10442, 11638, 13119]
Open Access
Abstract: Achiral bivalent ligands capable of simultaneous occupation of both hormone binding sites of transthyretin generate a substantial and complex induced near ultraviolet circular dichroism spectrum during protein binding, revealing the dynamics of this process. Reduced temperature and pH slow the interaction and reveal two phases consistent with formation of an encounter complex and progression of the interaction through the core of the transthyretin tetramer. The x-ray structure of the protein-ligand complex confirms the endpoint of the binding trajectory and shows evidence of plasticity in the structure, with substantial disturbances of some mainchain and sidechains within and adjacent to the binding channel. This study highlights the effective complementarity of CD and x-ray investigations.
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May 2026
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B23-Circular Dichroism
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Diamond Proposal Number(s):
[40646]
Open Access
Abstract: Microvolume UV–Vis and synchrotron radiation circular dichroism (SRCD) offer clear sustainability benefits by reducing sample and reagent consumption, yet their adoption is often limited by concerns over optical pathlength variability and low-volume dispensing inaccuracies. Here, we benchmark a μDrop™ Duo microplate workflow implemented on both a Multiskan SkyHigh spectrophotometer and the B23 HTCD/SRCD platform against conventional cuvette-based measurements, using a combination of per-well pathlength calibration, baseline subtraction, and rigorous pipetting validation. Across 32 wells, relative pathlengths showed measurable well-to-well variation, confirming that a single global correction factor is inadequate. Once corrected, microvolume spectra demonstrated quantitative agreement with cuvette references, supported by regression analysis, narrow Bland–Altman limits of agreement, and low baseline-region noise. Gravimetric evaluation of a multichannel pipette revealed substantial volume-dependent error at 20 µL, underscoring the importance of matching pipette class to microvolume operation and verifying performance under actual environmental conditions. Together, these results show that microvolume UV–Vis and SRCD workflows can achieve cuvette-level analytical reliability when appropriate calibration and QC procedures are applied. The study provides a three-tier set of best-practice recommendations—essential, recommended, and aspirational—designed to help laboratories implement greener workflows without compromising metrological integrity. This work demonstrates that sustainability and analytical performance can be mutually reinforcing when validation is embedded at each stage of microvolume analysis.
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Apr 2026
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