The post New guiding principles for community engagement and involvement in global health research was curated by information for practice.

The post New York Child Care Subsidy Staff Describe How Policy Implementation Influences Latino Families’ Receipt of Subsidies was curated by information for practice.

‘People doing door-to-door outreach to voters are encountering men who prevent their wives from even conversing at the door.’

The post Why are so many women hiding their voting plans from their husbands? was curated by information for practice.

Volume 29, Issue 7, October 2024. Read the full article ›

The post Embracing hybridity: the affordances of arts-based research for the professional doctorate in education was curated by information for practice.

Abe Kugielsky shot footage of Hasidic people trying to cross the street in Williamsburg during the 2024 New York City Marathon.

The use of biologic and targeted therapies for children with juvenile idiopathic arthritis (JIA) surpassed more typical therapies in recent years, according to Rutgers Health researchers.

Today, the Bronx Zoo announced that Idina Menzel, Tony Award-winner, actress, philanthropist and multi-platinum-selling singer/songwriter, will perform in the 98th Macy's Thanksgiving Day Parade(r) on the zoo's new "Wondrous World of Wildlife" float.

The use of biologic and targeted therapies for children with juvenile idiopathic arthritis (JIA) surpassed more typical therapies in recent years, according to Rutgers Health researchers.

The crystal structure of a neo­pentyl­oxypillar[5]arene with two pyridine mol­ecules encapsulated in the macrocyclic cavity is reported.

The crystal structure of a pyrrolidine analogue obtained from the stereoselective reduction of the enolic form of 4-hy­droxy-2-furyl-pyrrole­carboxyl­ate is described.

Hydraulic fracking exposes shale plays to acidic hydraulic fracking fluid (HFF), releasing toxic uranium (U) along with the desired oil and gas. With no existing methods to ensure U remains sequestered in the shale, this study sought to add organic ligands to HFF to explore potential U retention in shale plays. To test this possibility, incubations were set up in which uranyl acetate and one organic bipyridine ligand (either 2,2'-, 2,3'-, 2,4'-, or 4,4'-bipyridine) were added to pristine HFF as the crystallization medium. After several months and complete evaporation of all volatiles, bulk yellow crystalline material was obtained from the incubations, three of which yielded crystals suitable for single-crystal analysis, resulting in two novel structures and a high-quality structure of a previously described compound. The UO2VI acetate complexes bis(acetato-κ2O,O')(2,2'-bipyridine-κ2N,N')dioxidouranium(VI), [U(C2H3O2)2O2(C10H8N2)2] or [2,2'-bipyridine]UVIO2(CH3CO2)2, (I), and bis(acetato-κ2O,O')(2,4'-bipyridine-κN1')dioxidouranium(VI), [U(C2H3O2)2O2(C10H8N2)2] or [2,4'-bipyridine]2UVIO2(CH3CO2)2, (III), contain eight-coordinate UVI in a pseudo-hexagonal bipyramidal coordination geometry and are molecular, packing via weak C—H...O/N interactions, whereas catena-poly[bis(2,3'-bipyridinium) [di-μ-acetato-μ3-hydroxido-μ-hydroxido-di-μ3-oxido-hexaoxidotriuranium(VI)]–2,3'-bipyridine–water (1/1/1)], (C10H9N2)2[U3(C2H3O2)2O8(OH)2]·C10H8N2·H2O or {[2,3'-bipyridinium]2[2,3'-bipyridine][(UVIO2)3(O)2(OH)2(CH3CO2)2·H2O]}n, (II), forms an ionic one-dimensional polymer with seven-coordinate pentagonal bipyramidal UVI centers and hydrogen-bonding interactions within each chain. The formation of these crystals could indicate the potential for bipyridine to bind with U in shale during fracking, which will be explored in a future study via ICP-MS (inductively coupled plasma mass spectrometry) analyses of U concentration in HFF/bipyridine/shale incubations. The variation seen here between the molecular structures may indicate variance in the ability of bipyridine isomers to form complexes with U, which could impact their ability to retain U within shale in the context of fracking.

Imaging scaffolds composed of designed protein cages fused to designed ankyrin repeat proteins (DARPins) have enabled the structure determination of small proteins by cryogenic electron microscopy (cryo-EM). One particularly well characterized scaffold type is a symmetric tetrahedral assembly composed of 24 subunits, 12 A and 12 B, which has three cargo-binding DARPins positioned on each vertex. Here, the X-ray crystal structure of a representative tetrahedral scaffold in the apo state is reported at 3.8 Å resolution. The X-ray crystal structure complements recent cryo-EM findings on a closely related scaffold, while also suggesting potential utility for crystallographic investigations. As observed in this crystal structure, one of the three DARPins, which serve as modular adaptors for binding diverse `cargo' proteins, present on each of the vertices is oriented towards a large solvent channel. The crystal lattice is unusually porous, suggesting that it may be possible to soak crystals of the scaffold with small (≤30 kDa) protein cargo ligands and subsequently determine cage–cargo structures via X-ray crystallography. The results suggest the possibility that cryo-EM scaffolds may be repurposed for structure determination by X-ray crystallography, thus extending the utility of electron-microscopy scaffold designs for alternative structural biology applications.

Structures of tetra­pyridine­silver(I) hexa­fluoro­phosphate and tetra­pyridine silver(I) hexa­fluoro­anti­monate are reported from data collected at 300 K and 100 K.

In the title compound, the tellurium(VI) and vanadium(V) atoms are statistically disordered over two of the ten metal-atom sites in the unprotonated [TeV9O28]5– heteropolyanion.

Crystallization of the title compound from CH2Cl2/n-pentane (1:5 v/v) at room temperature gave two polymorphs, which crystallize in monoclinic (P21/c; α form) and ortho­rhom­bic (Pna21; β form) space groups. The ReI complex mol­ecules in either polymorph adopt a six-coordinate octa­hedral geometry with three facially-oriented carbonyl ligands, one bromido ligand, and two nitro­gen atoms from one chelating ligand ppt-OMe. In the crystal, both polymorph α and β form di-periodic sheet-like architectures supported by multiple hydrogen bonds.

N-terminally hexahistidine-tagged O. volvulus macrophage migration inhibitory factor-1 has a unique jellyfish-like structure with the prototypical macrophage migration inhibitory factor trimer as the `head' and a C-terminal extension as the `tail'.

Crystallization of the title compound, fac-[ReBr(ppt-OMe)(CO)3] (ppt-OMe = C15H12N2OS), from CH2Cl2/n-pentane (1:5 v/v) at room temperature gave two polymorphs, which crystallize in monoclinic (P21/c; α form) and orthorhombic (Pna21; β form) space groups. The ReI complex molecules in either polymorph adopt a six-coordinate octahedral geometry with three facially-oriented carbonyl ligands, one bromido ligand, and two nitrogen atoms from one chelating ligand ppt-OMe. In the crystal, both polymorph α and β form di-periodic sheet-like architectures supported by multiple hydrogen bonds. In polymorph α, two types of hydrogen bonds (C—H...O) are found while, in polymorph β, four types of hydrogen bonds (C—H...O and C—H...Br) exist.

A novel insertion device is introduced, designated as the Mango wiggler, designed for synchrotron radiation (SR) imaging that provides a large field of view. This innovative device is constructed from two orthogonal planar wigglers with a small difference in their period lengths, eliciting the phase difference of the magnetic fields to incrementally transitions from 0 to π/2. Such a configuration enlarges the vertical divergence of the light source, as with the horizontal divergence. The appellation `Mango wiggler' derives from the distinctive mango-shaped contour of its radiation field. A comprehensive suite of theoretical analyses and simulations has been executed to elucidate the radiation properties of the Mango wiggler, employing SPECTRA and Mathematica as calculation tools. In conjunction with the ongoing construction of the High Energy Photon Source in Beijing a practical Mango wiggler device has been fabricated for utilization in SR imaging applications. Theoretical analyses were applied to this particular Mango wiggler to yield several theoretical conclusions, and several simulations were performed according to the measured magnetic field results.

In the title complex, [Ni(C19H13N5)2](CF3SO3)2·(CH3CH2)2O, the central NiII atom is sixfold coordinated by three nitro­gen atoms of each 2,6-bis­(2-benzimidazol­yl)pyridine ligand in a distorted octa­hedral geometry with two tri­fluoro­methane­sulfonate ions and a mol­ecule of diethyl ether completing the outer coordination sphere of the complex. Hydrogen bonding contributes to the organization of the asymmetric units in columns along the a axis generating a porous supra­molecular structure. The structure was refined as a two-component twin with a refined BASF value of 0.4104 (13).

In the title complex salt, [Pd(C10H8N2)(C12H12N2O2)](CF3SO3)2, the palladium(II) atom is fourfold coordinated by two chelating ligands, 2,2'-bi­pyridine and 4,4'-dimeth­oxy-2,2'-bi­pyridine, in a distorted square-planar environment. In the crystal, weak π–π stacking inter­actions between the 2,2'-bi­pyridine rings [centroid-to-centroid distances = 3.8984 (19) Å] and between the 4,4'-dimeth­oxy-2,2'-bi­pyridine rings [centroid-to-centroid distances = 3.747 (18) Å] contribute to the alignment of the complex cations in columns parallel to the b-axis direction.

In the title complex, [Ru(C10H8N2)2(C6H6N2O)(H2O)](CF3SO3)2, the central RuII atom is sixfold coordinated by two bidentate 2,2'-bi­pyridine, an isonic­otinamide ligand, and a water mol­ecule in a distorted octa­hedral environment with tri­fluoro­methane­sulfonate ions completing the outer coordination sphere of the complex. Hydrogen bonding involving the water mol­ecule and weak π–π stacking inter­actions between the pyridyl rings in adjacent mol­ecules contribute to the alignment of the complexes in columns parallel to the c axis.

The structure of the title complex, [Zn2(C2H3O2)4(C11H9N3O)2], is triclinic containing half of the mol­ecule in the asymmetric unit. Each zinc atom is coordinated to a pyridyl and oxime nitro­gen from one di-2-pyridyl ketone oxime (dpko) ligand and a third nitro­gen from the other dpko pyridyl ring. Additionally, each zinc is coordinated to two acetato anions, one of which is bidentate and the other monodentate. The uncoordinated oxygen of the monodentate acetato group is involved in a hydrogen bond with the oxime hydrogen. The packing in the crystal is assisted by weak C—H⋯O inter­actions between acetato groups and neighboring pyridyl rings.

The structure of the title compound, [RuCl2(C7H10N2)2(C2H6OS)2], has monoclinic (P21/n) symmetry. The Ru—N distances of the coordination compound are influenced by the trans chloride or di­methyl­sulfoxide-κS ligands. The mol­ecular structure exhibits disorder for two of the terminal methyl groups of a dimethyl sulfoxide ligand.

The title compound, [Ru(C19H13N5)2](PF6)2·3C4H10O, was obtained from the reaction of Ru(bimpy)Cl3 [bimpy is 2,6-bis­(1H-benzimidazol-2-yl)pyridine] and bimpy in refluxing ethanol followed by recrystallization from diethyl ether/aceto­nitrile. At 125 K the complex has ortho­rhom­bic (Pca21) symmetry. It is remarkable that the structure is almost centrosymmetric. However, refinement in space group Pbcn leads to disorder and definitely worse results. It is of inter­est with respect to potential catalytic reduction of CO2. The structure displays N—H⋯O, N—H⋯F hydrogen bonding and significant π–π stacking and C—H⋯π stacking inter­actions.

In the title salt solvate (systematic name: 8-amino-5-ethyl-6-phenyl­phenanthridin-5-ium benzoate methanol monosolvate), C21H20N3+·C6H5CO2−·CH3OH, two ethidium cations, C21H20N3+, dimerize about a twofold axis through π–π inter­actions [inter-centroid separation = 3.6137 (4) Å]. The benzoate anions are connected through hydrogen bonding with the –NH2 groups of the ethidium cations and the –OH group of the MeOH mol­ecule. The MeOH mol­ecule also accepts a hydrogen bond from the –NH2 group of the ethidium cation. The result is a one-dimensional hydrogen-bonded chain along the b-axis direction.

In the title compound, {(C6H8N)[Zn2(HPO3)2(H2PO3)]}n, the constituent ZnO4, HPO3 and H2PO3 polyhedra of the inorganic component are linked into (010) sheets by Zn—O—P bonds (mean angle = 134.4°) and the layers are reinforced by O—H⋯O hydrogen bonds. The protonated templates are anchored to the inorganic sheets via bifurcated N—H⋯(O,O) hydrogen bonds.

The mol­ecule of the title NCNHCS pincer N-heterocyclic carbene palladium(II) complex, [PdBr(C21H25N3S)]Br, exhibits a slightly distorted square-planar coordination at the palladium(II) atom, with the five-membered chelate ring nearly planar. The six-membered chelate ring adopts an envelope conformation. Upon chelation, the sulfur atom becomes a stereogenic centre with an RS configuration induced by the chiral carbon of the precursor imidazolium salt. There are intra­molecular C—H⋯Br—Pd hydrogen bonds in the structure. The two inter­stitial Br atoms, as the counter-anion of the structure, are both located on crystallographic twofold axes and are connected to the complex cations via C—H⋯·Br hydrogen bonds.

The title compound, C17H17BN3I, is a type of di­aza­borinane featuring substitution at the 1, 2, and 3 positions of the nitro­gen–boron six-membered heterocycle. The organic mol­ecule has a planar structure, the dihedral angle between the pyridyl ring and the fused ring system being 3.46 (4)°. In the crystal, mol­ecules are stacked in a head-to-tail manner. The iodide ion makes close contacts with three organic mol­ecules and supports the alternating stack.

The cation of the title hydrated salt, C17H17BN3+·I−·H2O, is a di­aza­borinane featuring substitution at the 1, 2, and 3 positions in the nitro­gen–boron six-membered heterocycle. The cation is approximately planar with a dihedral angle between the pyridyl ring and the di­aza­borinane ring system of 5.40 (5)°. In the crystal, the cations stack along [100] in an alternating head-to-tail manner, while the iodide ion and water mol­ecule form one-dimensional hydrogen-bonded chains beside the cation stack. The cation stacks and I−–water chains are crosslinked by N—H⋯I and N—H⋯O hydrogen bonds.

In the structure of the title complex, [Zn(C4H2FN2O2)(C10H24N4)]ClO4, the zinc(II) ion forms coordination bonds with the four nitro­gen atoms of cyclam (1,4,8,11-tetra­aza­cyclo­tetra­decane or [14]aneN4) as well as with the nitro­gen atom of a deprotonated 5-fluoro­uracil ion (FU−). Cyclam adopts a trans-I type conformation within this structure. The coordination structure of the zinc(II) ion is a square pyramid with a distorted base plane formed by the four nitro­gen atoms of the cyclam. FU− engages in inter­molecular hydrogen bonding with neighboring FU− mol­ecules and with the cyclam mol­ecule.

In the title compound, [Mn(C68H44N12O4)(C5H8N2)]·2C6H5Cl, the central MnII ion is coordinated by four pyrrole N atoms of the porphyrin core in the basal sites and one N atom of the 2,5-di­methyl­imidazole ligand in the apical site. Two chloro­benzene solvent mol­ecules are also present in the asymmetric unit. Due to the apical imidazole ligand, the Mn atom is displaced out of the 24-atom porphyrin mean plane by 0.66 Å. The average Mn—Np (p = porphyrin) bond length is 2.143 (8) Å, and the axial Mn—NIm (Im = 2,5-di­methyl­imidazole) bond length is 2.171 (8) Å. The structure displays inter­molecular and intra­molecular N—H⋯O, N—H⋯N, C—H⋯O and C—H⋯N hydrogen bonding. The crystal studied was refined as a two-component inversion twin.

The title compound, [Ir(C8H12)(C8H15N3)(C18H15P)]BF4, a new triazole-based N-heterocyclic carbene iridium(I) cationic complex with a tetra­fluorido­borate counter-anion, crystallizes with two cations and two anions in the asymmetric unit of space group Pc. The Ir centers of the cations have distorted square-planar conformations, formed by a bidentate (η2 + η2) cyclo­octa-1,5-diene (COD) ligand, an N-heterocyclic carbene and a tri­phenyl­phosphane ligand with the NHC carbon atom and P atom being cis. In the extended structure, non-classical C–H⋯F hydrogen bonds, one of which is notably short (H⋯F = 2.21 Å), link the cations and anions. The carbon atoms of one of the COD ligands are disordered over adjacent sites in a 0.62:0.38 ratio.

The title compound, C15H12BN3, is a type of di­aza­borinane featuring substitution at 1, 2, and 3 positions in the nitro­gen–boron six-membered heterocycle. It is comprised of two almost planar units, the pyridyl ring and the Bdan (dan = 1,8-di­aminona­phtho) group, which subtend a dihedral angle of 24.57 (5)°. In the crystal, the mol­ecules are linked into R44(28) hydrogen-bonding networks around the fourfold inversion axis, giving cyclic tetra­mers. The mol­ecules form columnar stacks along the c axis.

The title compound, [Ni2(C8H6N3)2(C2H3O2)2(C5H8N2)2] or [Ni(μ-OOCCH3)(2-PyPz)(Me2PzH)]2 (1) [2-PyPz = 3-(pyridin-2-yl) pyrazole; Me2PzH = 3,5-dimethyl pyrazole] was synthesized from Ni(OOCCH3)2·4H2O, 2-PyPzH, Me2PzH and tri­ethyl­amine as a base. Compound 1 {[Ni2(C30H34N10Ni2O4)]} at 100 K has monoclinic (P21/n) symmetry and the mol­ecules have crystallographic inversion symmetry. Mol­ecules of 1 comprise an almost planar dinuclear NiII core with an N4O2 coordination environment. The equatorial plane consists of N3,O coordination derived from one of the bidentate acetate O atoms and three of the N atoms of the chelating 2-PyPz ligand while the axial positions are occupied by neutral Me2PzH and the second O atom of the acetate unit. The Ni atoms are bridged by the nitro­gen atom of a deprotonated 2-PyPz ligand. Compound 1 exhibits various inter- and intra­molecular C—H⋯O and N—H⋯O hydrogen bonds.

The title compound (systematic name: pyridinium 4-methyl­benzene­sulfonate), C5H6N+·C7H7O3S−, is the pyridinium salt of para-toluene­sulfonic acid. In the crystal, classical N—H⋯O hydrogen bonds as well as C—H⋯O contacts connect the cationic and anionic entities into sheets lying parallel to the ab plane.

The title compound, [Ir(C15H10N)2(C19H12N4)]PF6·CH3OH, crystallizes in the C2/c space group with one monocationic iridium complex, one hexa­fluorido­phosphate anion, and one methanol solvent mol­ecule of crystallization in the asymmetric unit, all in general positions. The anion and solvent are linked to the iridium complex cation via hydrogen bonding. All bond lengths and angles fall into expected ranges compared to similar compounds.

A new triazole-based N-heterocyclic carbene IrI cationic complex with a tetra­fluorido­borate counter-anion and hemi-solvating di­chloro­methane, [Ir(C8H12)(C8H15N3)(C18H15P)]BF4·0.5CH2Cl2, has been synthesized and structurally characterized. There are two independent ion pairs in the asymmetric unit and one di­chloro­methane solvent mol­ecule per two ion pairs. The cationic complex exhibits a distorted square-planar conformation around the IrI atom, formed by a bidentate cyclo­octa-1,5,diene (COD) ligand, a tri­phenyl­phosphane ligand, and an N-heterocyclic carbene (NHC). There are several close non-standard H⋯F hydrogen-bonding inter­actions that orient the tetra­fluorido­borate anions with respect to the IrI complex mol­ecules. The complex shows promising catalytic activity in transfer hydrogenation reactions. The structure was refined as a non-merohedral twin, and one of the COD mol­ecules is statistically disordered.

The crystal structure of 1,4-bis­(neopent­yloxy)pillar[5]arene, C95H140N2O10 (TbuP), featuring two encapsulated pyridine mol­ecules, reveals significant host–guest inter­actions. Inter­estingly, the pyridine guests are positioned near the neopent­yloxy substituents instead of the electron-rich aromatic core of the pillar[5]arene. This spatial arrangement suggests a preference for the pyridine mol­ecules to engage with the aliphatic regions of the host. Detailed analysis of the structural characteristics of this host–guest system (TbuP·2Py), as well as its packing pattern within the crystal network, is presented and discussed.

A confiscated package of street drugs was characterized by the usual mass spectral (MS) and FT–IR analyses. The confiscated powder material was highly crystalline and was found to consist of two very different species, accidentally of sizes convenient for X-ray diffraction. Thus, one each was selected and redundant com­plete sets of data were collected at 100 K using Cu Kα radiation. The selected crystals contained: (a) 1,2-diphenyl-2-(pyrrolidin-1-yl)ethanone hy­dro­chloride hemihydrate or 1-(2-oxo-1,2-di­phenyl­eth­yl)pyrrolidin-1-ium chloride hemihydrate, C18H20NO+·Cl−·0.5H2O, (I), a synthetic cathinone called `α-D2PV', and (b) the sugar myo-inositol, C6H12O6, (II), probably the only instance in which the drug and its diluent have been fully characterized from a single confiscated sample. Moreover, the structural details of both are rather attractive showing: (i) inter­esting hydrogen bonding observed in pairwise inter­actions by the drug mol­ecules, mediated by the chloride counter-anions and the waters of crystallization, and (ii) π–π inter­actions in the case of the phenyl rings of the drug which are of two different types, namely, π–π stacking and edge-to-π. Finally, the inositol crystallizes with Z' = 2 and the resulting diastereoisomers were examined by overlay techniques.

The synthesis and structural characterization of three families of coordination com­plexes synthesized from 4'-phenyl-2,2':6',2''-terpyridine (8, Ph-TPY), 4'-(4-chloro­phen­yl)-2,2':6',2''-terpyridine (9, ClPh-TPY) and 4'-(4-meth­oxy­phen­yl)-2,2':6',2''-terpyridine (10, MeOPh-TPY) ligands with the divalent metals Co2+, Fe2+, Mn2+ and Ni2+ are reported. The com­pounds were synthesized from a 1:2 mixture of the metal and ligand, resulting in a series of com­plexes with the general formula [M(R-TPY)2](ClO4)2 (where M = Co2+, Fe2+, Mn2+ and Ni2+, and R-TPY = Ph-TPY, ClPh-TPY and MeOPh-TPY). The general formula and structural and supra­molecular features were determinated by single-crystal X-ray diffraction for bis­(4'-phenyl-2,2':6',2''-terpyridine)­nickel(II) bis­(per­chlo­rate), [Ni(C21H15N3)2](ClO4)2 or [Ni(Ph-TPY)2](ClO4)2, bis­[4'-(4-meth­oxy­phen­yl)-2,2':6',2''-terpyridine]­manganese(II) bis­(per­chlo­rate), [Mn(C22H17N3O)2](ClO4)2 or [Mn(MeOPh-TPY)2](ClO4)2, and bis­(4'-phenyl-2,2':6',2''-ter­py­ridine)­manganese(II) bis­(per­chlo­rate), [Mn(C21H15N3)2](ClO4)2 or [Mn(Ph-TPY)2](ClO4)2. In all three cases, the com­plexes present distorted octa­hedral coordination polyhedra and the crystal packing is determined mainly by weak C—H⋯π inter­actions. All the com­pounds (except for the Ni derivatives, for which FT–IR, UV–Vis and thermal analysis are reported) were fully characterized by spectroscopic (FT–IR, UV–Vis and NMR spectroscopy) and thermal (TGA–DSC, thermogravimetric analysis–differential scanning calorimetry) methods.

Using a 1:1 cocrystal of (E)-N-(3,4-di­fluoro­phen­yl)-1-(pyridin-4-yl)methanimine with acetic acid, C12H8F2N2·C2H4O2, we investigate the influence of F atoms introduced to the aromatic ring on promoting π–π inter­actions. The cocrystal crystallizes in the triclinic space group P1. Through crystallographic analysis and com­putational studies, we reveal the mol­ecular arrangement within this co­crystal, demonstrating the presence of hydrogen bonding between the acetic acid mol­ecule and the pyridyl group, along with π–π inter­actions between the aromatic rings. Our findings highlight the importance of F atoms in promoting π–π inter­actions without necessitating full halogenation of the aromatic ring.

The highly cytotoxic macrocyclic trichothecene Isororidin A (C29H40O9) was isolated from the fungus Myrothesium verrucaria endophytic on the wild medicinal plant `Datura' (Datura stramonium L.) and was characterized by one- (1D) and two-dimensional (2D) NMR spectroscopy. The three-dimensional structure of Isororidin A has been confirmed by X-ray crystallography at 0.81 Å resolution from crystals grown in the ortho­rhom­bic space group P212121, with one mol­ecule per asymmetric unit. Isororidin A is the epimer of previously described (by X-ray crystallography) Roridin A at position C-13' of the macrocyclic ring.

Catalase is an antioxidant enzyme that breaks down hydrogen peroxide (H2O2) into molecular oxygen and water. In all monofunctional catalases the pathway that H2O2 takes to the catalytic centre is via the `main channel'. However, the structure of this channel differs in large-subunit and small-subunit catalases. In large-subunit catalases the channel is 15 Å longer and consists of two distinct parts, including a hydrophobic lower region near the heme and a hydrophilic upper region where multiple H2O2 routes are possible. Conserved glutamic acid and threonine residues are located near the intersection of these two regions. Mutations of these two residues in the Scytalidium thermophilum catalase had no significant effect on catalase activity. However, the secondary phenol oxidase activity was markedly altered, with kcat and kcat/Km values that were significantly increased in the five variants E484A, E484I, T188D, T188I and T188F. These variants also showed a lower affinity for inhibitors of oxidase activity than the wild-type enzyme and a higher affinity for phenolic substrates. Oxidation of heme b to heme d did not occur in most of the studied variants. Structural changes in solvent-chain integrity and channel architecture were also observed. In summary, modification of the main-channel gate glutamic acid and threonine residues has a greater influence on the secondary activity of the catalase enzyme, and the oxidation of heme b to heme d is predominantly inhibited by their conversion to aliphatic and aromatic residues.

The Swiss Light Source facilitates fragment-based drug-discovery campaigns for academic and industrial users through the Fast Fragment and Compound Screening (FFCS) software suite. This framework is further enriched by the option to utilize the Smart Digital User (SDU) software for automated data collection across the PXI, PXII and PXIII beamlines. In this work, the newly developed HEIDI webpage (https://heidi.psi.ch) is introduced: a platform crafted using state-of-the-art software architecture and web technologies for sample management of rotational data experiments. The HEIDI webpage features a data-review tab for enhanced result visualization and provides programmatic access through a representational state transfer application programming interface (REST API). The migration of the local FFCS MongoDB instance to the cloud is highlighted and detailed. This transition ensures secure, encrypted and consistently accessible data through a robust and reliable REST API tailored for the FFCS software suite. Collectively, these advancements not only significantly elevate the user experience, but also pave the way for future expansions and improvements in the capabilities of the system.

Radiation damage remains one of the major impediments to accurate structure solution in macromolecular crystallography. The artefacts of radiation damage can manifest as structural changes that result in incorrect biological interpretations being drawn from a model, they can reduce the resolution to which data can be collected and they can even prevent structure solution entirely. In this article, we discuss how to identify and mitigate against the effects of radiation damage at each stage in the macromolecular crystal structure-solution pipeline.

Type VII secretion (T7S) systems, also referred to as ESAT-6 secretion (ESX) systems, are molecular machines that have gained great attention due to their implications in cell homeostasis and in host–pathogen interactions in mycobacteria. The latter include important human pathogens such as Mycobacterium tuberculosis (Mtb), the etiological cause of human tuberculosis, which constitutes a pandemic accounting for more than one million deaths every year. The ESX-5 system is exclusively found in slow-growing pathogenic mycobacteria, where it mediates the secretion of a large family of virulence factors: the PE and PPE proteins. The secretion driving force is provided by EccC5, a multidomain ATPase that operates using four globular cytosolic domains: an N-terminal domain of unknown function (EccC5DUF) and three FtsK/SpoIIIE ATPase domains. Recent structural and functional studies of ESX-3 and ESX-5 systems have revealed EccCDUF to be an ATPase-like fold domain with potential ATPase activity, the functionality of which is essential for secretion. Here, the crystal structure of the MtbEccC5DUF domain is reported at 2.05 Å resolution, which reveals a nucleotide-free structure with degenerated cis-acting and trans-acting elements involved in ATP binding and hydrolysis. This crystallographic study, together with a biophysical assessment of the interaction of MtbEccC5DUF with ATP/Mg2+, supports the absence of ATPase activity proposed for this domain. It is shown that this degeneration is also present in DUF domains from other ESX and ESX-like systems, which are likely to exhibit poor or null ATPase activity. Moreover, based on an in silico model of the N-terminal region of MtbEccC5DUF, it is hypothesized that MtbEccC5DUF is a degenerated ATPase domain that may have retained the ability to hexamerize. These observations draw attention to DUF domains as structural elements with potential implications in the opening and closure of the membrane pore during the secretion process via their involvement in inter-protomer interactions.

Histidine can be protonated on either or both of the two N atoms of the imidazole moiety. Each of the three possible forms occurs as a result of the stereochemical environment of the histidine side chain. In an atomic model, comparing the possible protonation states in situ, looking at possible hydrogen bonding and metal coordination, it is possible to predict which is most likely to be correct. A more direct method is described that uses quantum-mechanical methods to calculate, also in situ, the minimum geometry and energy for comparison, and therefore to more accurately identify the most likely proton­ation state.

In the search for new active pharmaceutical ingredients, the precise control of the chemistry of cocrystals becomes essential. One crucial step within this chemistry is proton migration between cocrystal coformers to form a salt, usually anticipated by the empirical ΔpKa rule. Due to the effective role it plays in modifying intermolecular distances and interactions, pressure adds a new dimension to the ΔpKa rule. Still, this variable has been scarcely applied to induce proton-transfer reactions within these systems. In our study, high-pressure X-ray diffraction and Raman spectroscopy experiments, supported by DFT calculations, reveal modifications to the protonation states of the 4,4'-bi­pyridine (BIPY) and malonic acid (MA) cocrystal (BIPYMA) that allow the conversion of the cocrystal phase into ionic salt polymorphs. On compression, neutral BIPYMA and monoprotonated (BIPYH+MA−) species coexist up to 3.1 GPa, where a phase transition to a structure of P21/c symmetry occurs, induced by a double proton-transfer reaction forming BIPYH22+MA2−. The low-pressure C2/c phase is recovered at 2.4 GPa on decompression, leading to a 0.7 GPa hysteresis pressure range. This is one of a few studies on proton transfer in multicomponent crystals that shows how susceptible the interconversion between differently charged species is to even slight pressure changes, and how the proton transfer can be a triggering factor leading to changes in the crystal symmetry. These new data, coupled with information from previous reports on proton-transfer reactions between coformers, extend the applicability of the ΔpKa rule incorporating the pressure required to induce salt formation.

Serial crystallography requires large numbers of microcrystals and robust strategies to rapidly apply substrates to initiate reactions in time-resolved studies. Here, we report the use of droplet miniaturization for the controlled production of uniform crystals, providing an avenue for controlled substrate addition and synchronous reaction initiation. The approach was evaluated using two enzymatic systems, yielding 3 µm crystals of lysozyme and 2 µm crystals of Pdx1, an Arabidopsis enzyme involved in vitamin B6 biosynthesis. A seeding strategy was used to overcome the improbability of Pdx1 nucleation occurring with diminishing droplet volumes. Convection within droplets was exploited for rapid crystal mixing with ligands. Mixing times of <2 ms were achieved. Droplet microfluidics for crystal size engineering and rapid micromixing can be utilized to advance time-resolved serial crystallography.

The functionality and efficiency of proteins within a biological membrane are highly dependent on both the membrane lipid composition and the physiochemical properties of the solution. Lipid mesophases are directly influenced by changes in temperature, pH, water content or due to individual properties of single lipids such as photoswitchability. In this work, we were able to induce light- and temperature-driven mesophase transitions in a model membrane system containing a mixture of 1,2-dipalmitoyl-phosphatidylcholine phospho­lipids and azo­benzene amphiphiles. We observed reversible and reproducible transitions between the lamellar and Pn3m cubic phase after illuminating the sample for 5 min with light of 365 and 455 nm wavelengths, respectively, to switch between the cis and trans states of the azo­benzene N=N double bond. These light-controlled mesophase transitions were found for mixed complexes with up to 20% content of the photosensitive molecule and at temperatures below the gel-to-liquid crystalline phase transition temperature of 33°C. Our results demonstrate the potential to design bespoke model systems to study the response of membrane lipids and proteins upon changes in mesophase without altering the environment and thus provide a possible basis for drug delivery systems.