I04-Macromolecular Crystallography
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Diamond Proposal Number(s):
[23269]
Open Access
Abstract: Human somatic angiotensin I-converting enzyme is a key zinc metallopeptidase in cardiovascular regulation that hydrolyzes angiotensin peptides (Ang I, Ang II), as well as other vasoactive peptides, including kinins (e.g., bradykinin), substance P, the acetylated tetrapeptide Ac-Ser-Asp-Lys-Pro, and the amyloid ß-peptide. Because of its enzymatic promiscuity, ACE and its substrates and products affect many physiological processes, including blood pressure control, hemopoiesis, reproduction, renal development/function, fibrosis, and immune response. ACE inhibitors are among the most important therapeutic agents available today for the treatment of hypertension, heart failure, coronary artery disease, renal insufficiency, and general atherosclerosis. However, they need much improvement because of the side effects seen in patients with long-term treatment due to nonselective inhibition of the N- and C-domains of ACE (referred to as nACE and cACE, respectively). Here, we report that ACE activity can be inhibited by ciprofloxacin, a potent fluoroquinolone antibiotic (IC50 202.7/Ki 33.8 μM for cACE). In addition, the high-resolution crystal structure of cACE in complex with ciprofloxacin reveals that it binds at an exosite away from the active site pocket, overlapping the position of a potential allosteric site with a different binding mode. The detailed structural information reported here will provide a useful scaffold for the design of future potent allosteric inhibitors.
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Jun 2025
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[29890]
Open Access
Abstract: The extraction of lithium from natural deposits is energy intensive due to its coexistence with physiochemically similar alkali (Na+ and K+) and alkaline earth (Mg2+ and Ca2+) metal ions. Methods for the direct and specific extraction of lithium from salt mixtures are thus essential to ensure an adequate supply of this metal for the batteries needed to decarbonize the world economy. Here, we present the preparation of alkali-metal-templated coordination cages and their application to lithium extraction. Within the cage framework, protons alter the relative binding affinities of Li+ and similar metal ions: protons associate exclusively with Li+ in close proximity at the cage vertices, repelling other cations as a result of increased electrostatic repulsion, enhanced steric hindrance, and reduced availability of coordinating nitrogen atoms. We developed this proton-driven lithium recognition within coordination cages into a separation cycle capable of extracting Li+ from a mixture of salts that includes Na+, K+, Mg2+, and Ca2+.
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Apr 2025
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[21497]
Open Access
Abstract: Here, we report two (AgI3I)4L4 metal-organic cages that each contain a previously unobserved trisilver(I) iodide cluster at their vertices. Clusters containing fewer than 10 AgI ions are challenging to synthesize in an atomically precise manner. Previous work has demonstrated the potential of the approach of generating such clusters during the formation of higher-order metal-organic cage superstructures, but too few examples were known for design principles to be deciphered. Through analysis of the set of such cages reported herein and previously, we elaborate a set of design principles for their synthesis.
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Mar 2025
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B18-Core EXAFS
I11-High Resolution Powder Diffraction
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Xu
Chen
,
Dhruv
Menon
,
Xiaoliang
Wang
,
Meng
He
,
Mohammad Reza
Alizadeh Kiapi
,
Mehrdad
Asgari
,
Yuexi
Lyu
,
Xianhui
Tang
,
Luke L.
Keenan
,
William
Shepard
,
Lik H.
Wee
,
Sihai
Yang
,
Omar K.
Farha
,
David
Fairen-Jimenez
Diamond Proposal Number(s):
[32566, 34552]
Open Access
Abstract: Selective CO2 capture from industry is crucial for reducing emissions from fossil fuel combustion. Flexible metal-organic frameworks (MOFs) have shown promise for CO2 adsorption via differential binding and size-exclusion mechanisms. However, achieving precise pore-size control to selectively capture CO2, particularly in the presence of N2 and water, remains a challenge. Here, we demonstrate a strategy for frustrating framework flexibility in a MOF to create an optimal, confined pore environment that enhances selective CO2 recognition while maintaining high working capacity. We designed a flexible MOF, Cambridge University (CU)-4, by using a bulky cubane-derived ligand and In3+ ions that undergo dynamic breathing with a 2 Å contraction upon solvent exchange and removal. In situ synchrotron X-ray diffraction and molecular simulations reveal that the stable narrow-pore configuration creates a hydrogen-rich cavity that selectively binds CO2 via multiple hydrogen bonds. This physisorption-based CO2 recognition remains effective even at 80% humidity, making CU-4 promising for post-combustion carbon capture.
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Jan 2025
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[31850]
Open Access
Abstract: Glycan sulfation is a widespread postglycosylation modification crucial for modulating biological functions including cellular adhesion, signaling, and bacterial colonization. 6-Sulfo-β-GlcNAcases are a class of enzyme that alters sulfation patterns. Such changes in sulfation patterns are linked to diseases such as bowel inflammation, colitis, and cancer. Despite their significance, 6-sulfo-β-GlcNAcases, which cleave β-linked 6-sulfo-N-acetylglucosamine (6S-GlcNAc), have been but rarely identified. This scarcity results mainly from the short, diverse, and distinctive sulfate-binding motifs required for recognition of the 6-sulfate group in 6S-GlcNAc in addition to the conserved GH20 family features. In this study, we discovered 6-sulfo-β-GlcNAcases and assigned two novel sulfate-binding motifs by the use of comparative genomics, structural predictions, and activity-based screening. Our findings expand the known microbiota capable of degrading sulfated glycans and add significant enzymes to the tool kit for analysis and synthesis of sulfated oligosaccharides.
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Nov 2024
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[29890]
Open Access
Abstract: Inspired by natural systems, metal-organic cages with well-defined shapes and cavities can be tuned for different guest-binding functions. Here, we report the construction of two types of cage frameworks: an MII12L8 (M = ZnII and CoII) pseudo-cuboctahedral architecture 1 and a rarer MII9L8 (M = ZnII and CoII) pseudo-Johnson-solid-type (J51) framework 2. Both structures form from the same boron-containing triamine subcomponent, and each one incorporates hexacoordinate metal vertices chelated by only two bidentate pyridyl(imine) arms. Such vertices provide the cages with the flexibility required to form lower-symmetry architectures, and they also facilitate reversible disassembly in response to fluoride. These cages were also shown to respond to other chemical stimuli enabling transformation between cage structures. Cage 1 bound different guest molecules, including the anticancer drug paclitaxel, C-methylcalix[4]resorcinarene, and tetraphenylborates. The release of paclitaxel by 1 was stimulated by fluoride or chloride, highlighting the potential for applications in natural product separation and drug delivery.
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Sep 2024
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I03-Macromolecular Crystallography
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Diamond Proposal Number(s):
[20147]
Open Access
Abstract: Many cell-surface receptors are promising targets for chemical synthesis because of their critical roles in disease development. This synthetic approach enables investigations by racemic protein crystallography and ligand discovery by mirror-image methodologies. However, due to their complex nature, the chemical synthesis of a receptor can be a significant challenge. Here, we describe the chemical synthesis and folding of a central, cysteine-rich domain of the cell-surface receptor tumor necrosis factor 1 which is integral to binding of the cytokine TNF-α, namely, TNFR-1 CRD2. Racemic protein crystallography at 1.4 Å confirmed that the native binding conformation was preserved, and TNFR-1 CRD2 maintained its capacity to bind to TNF-α (KD ≈ 7 nM). Encouraged by this discovery, we carried out mirror-image phage display using the enantiomeric receptor mimic and identified a d-peptide ligand for TNFR-1 CRD2 (KD = 1 μM). This work demonstrated that cysteine-rich domains, including the central domains, can be chemically synthesized and used as mimics for investigations.
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Dec 2023
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I04-Macromolecular Crystallography
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George H.
Hutchins
,
Sebastian
Kiehstaller
,
Pascal
Poc
,
Abigail H.
Lewis
,
Jisun
Oh
,
Raya
Sadighi
,
Nicholas M.
Pearce
,
Mohamed
Ibrahim
,
Ivana
Drienovská
,
Anouk M.
Rijs
,
Saskia
Neubacher
,
Sven
Hennig
,
Tom N.
Grossmann
Diamond Proposal Number(s):
[25413]
Open Access
Abstract: Proteins are essential biomolecules and central to biotechnological applications. In many cases, assembly into higher-order structures is a prerequisite for protein function. Under conditions relevant for applications, protein integrity is often challenged, resulting in disassembly, aggregation, and loss of function. The stabilization of quaternary structure has proven challenging, particularly for trimeric and higher-order complexes, given the complexity of involved inter- and intramolecular interaction networks. Here, we describe the chemical bicyclization of homotrimeric protein complexes, thereby increasing protein resistance toward thermal and chemical stress. This approach involves the structure-based selection of cross-linking sites, their variation to cysteine, and a subsequent reaction with a triselectrophilic agent to form a protein assembly with bicyclic topology. Besides overall increased stability, we observe resistance toward aggregation and greatly prolonged shelf life. This bicyclization strategy gives rise to unprecedented protein chain topologies and can enable new biotechnological and biomedical applications.
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Nov 2023
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[29072]
Open Access
Abstract: Synthetic cells, like their biological counterparts, require internal compartments with distinct chemical and physical properties where different functionalities can be localized. Inspired by membrane-less compartmentalization in biological cells, here, we demonstrate how microphase separation can be used to engineer heterogeneous cell-like architectures with programmable morphology and compartment-targeted activity. The synthetic cells self-assemble from amphiphilic DNA nanostructures, producing core-shell condensates due to size-induced de-mixing. Lipid deposition and phase-selective etching are then used to generate a porous pseudo-membrane, a cytoplasm analog, and membrane-less organelles. The synthetic cells can sustain RNA synthesis via in vitro transcription, leading to cytoplasm and pseudo-membrane expansion caused by an accumulation of the transcript. Our approach exemplifies how architectural and functional complexity can emerge from a limited number of distinct building blocks, if molecular-scale programmability, emergent biophysical phenomena, and biochemical activity are coupled to mimic those observed in live cells.
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Nov 2023
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[15768, 21497]
Open Access
Abstract: The development of artificial molecular systems capable of allosteric regulation has the potential to unlock new functions related to the purification, sensing, and transformation of bound guests. Here, we employ the binding of fluoride to boron centers within the walls of metal-organic cages to modulate cage conformations and allosterically tune their host-guest binding. Tetrahedral ZnII4L4 and octahedral ZnII6L4 cages that contain the same boron-centered moiety responded differently to fluoride binding, inhibiting or enhancing the binding of a second guest, respectively. Upon binding the allosteric effector F−, the apertures of the octahedral cage expanded, facilitating guest binding. The apertures of the tetrahedral cage also expanded following F− addition, but this expansion led to a decrease in internal cavity volume, thus leading to an expulsion of guest molecules. Synergetic allosteric regulation between the tetrahedral and octahedral cages was also possible, whereby a guest transferred between the two cages upon binding of fluoride to both.
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Apr 2023
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