Coordination Sites Research Articles

A mixed methods evaluation of the Canopy Cancer Collective’s implementation of network-wide screening initiative in 2023.

709 Background: The Canopy Cancer Collective, a Learning Health Network (LHN) comprised of 14 pancreatic cancer centers across the U.S., set ambitious goals in 2023 to improve screening rates across four key areas: clinical trial screening (from a baseline of 30% to 100%), assessment of enzyme replacement (37% to 100%), goals of care discussions (57% to 100%), and palliative care screening (30% to 100%). This study aimed to identify the barriers and facilitators influencing the implementation of these screening aims, with the goal of developing informed, actionable recommendations for future implementation efforts. Methods: Throughout 2023, data were gathered from monthly assessments completed by site coordinators and quality improvement coaches at each of the 14 centers. These assessments captured insights into planning, implementation, and challenges related to the screening aims. Additionally, a comprehensive site assessment conducted in October 2023 was analyzed. We employed content analysis to identify the key factors influencing the implementation process, with percentage improvements in screening aims documented. Results: A total of 128 assessments were reviewed. The most common barriers identified were insufficient personnel and time for screening implementation (n=7), delayed responses and lack of engagement from supporting teams (n=6), unanticipated delays and logistical barriers to the procedures (n=6), recruitment challenges (n=3), and changes in the staff or management (n=5). Facilitators that supported implementation included: identification and testing of patient-centered strategies for implementation of screening (n=11), team expansion (n=8), consistent data collection and sharing through the LHN database (n=7), launching of other initiatives tailored to institutional needs (n=5), and collaboration between teams within or across institutions (n=4). Among the barriers to form ideal interprofessional composition, resource shortages (n=7), provider shortages (n=6), and coordination difficulties (n=5) were included. By January 2024, the network’s screening rates had improved significantly: 92% for clinical trial, 87% for enzyme need and palliative care each, and 97% for goals of care. Conclusions: While common challenges such as staffing limitations and logistical barriers posed obstacles, facilitators like patient-centered strategies, team growth, and improved collaboration were key to the successful implementation of the screening aims. These findings offer actionable insights for enhancing future implementation efforts, with a focus on addressing resource limitations and fostering team engagement. Moving forward, we plan to assess the outcomes of these screening initiatives to examine their impact on patient care and evaluate the perceptions of site on utilization of implementation strategies to promote its adoption.

Unraveling the Mechanism and Influence of Auxiliary Ligands on the Isomerization of Neutral [P,O]-Chelated Nickel Complexes for Olefin Polymerization.

The copolymerization of ethylene with polar monomers presents a significant challenge. While palladium catalysts have shown promise, nickel catalysts are more economical but suffer from poor activity. Previous studies suggest that the isomerization step involved in the nickel-catalyzed polymerization may influence the catalyst activities. Herein, we explore the isomerization mechanisms of two phosphine-phenoxide-ligated catalysts using density functional theory (DFT) studies. We found that out of dissociative, tetrahedral, and associative mechanisms, the associative mechanism is the likeliest, with a pendant methoxy oxygen atom from the ligand to fulfill the fifth coordination site on nickel before Berry pseudorotation. The effect of varying auxiliary ligands on the activation barrier heights was also investigated and found that electron-releasing alkyl groups on substituted pyridine ligands have diminished electronic influence on pseudorotational barriers, but if present at the ortho-positions, will elevate the barriers due to larger steric influences. The electron-withdrawing groups on the ligand result in weaker ligand binding and lower pseudorotational barriers. These insights into the mechanisms of cis-trans isomerization and auxiliary ligand effects may offer valuable guidance for optimizing catalyst performance in copolymerization processes by lowering the barrier of isomerization by fine-tuning the steric and electronic influences of auxiliary ligands and enhancing overall copolymerization efficiency.

Inquiry-based learning in Bangladesh: insights into middle and high school students’ experiences and 21st century skill development

Educators worldwide are using a variety of approaches to develop students’ 21st century skills, better known as the 4Cs: communication, collaboration, critical thinking, and creativity. As part of a larger QUAN-QUAL mixed method study, this paper describes urban Bangladeshi students, teachers, and site coordinators’ thoughts about the influence of a six-month inquiry-based learning (IBL) science project on middle and high students’ 4C skill development. We analyzed survey data from 109 students and 20 teachers, interview data from site coordinators, and Zoom transcripts to identify areas of growth. Students reported that the project fostered the development of communication and collaboration skills. We also noted gains in critical thinking and creativity skills. Nonparametric statistics confirmed that grade levels have a statistically significant effect on the 4C skills development. However, curriculum type (British vs. National) did not have a considerable influence, showing that teachers can use IBL projects to develop 4C skills regardless of curriculum variations. This study highlights the benefits of providing teachers with professional development that targets design and implementation of IBL to foster 4C skills development across content areas and educational settings.

Study and conservation of the genetic potential of the wild plant Agriophyllum squarrosum L. in the deserts and semi-deserts of Western Kazakhstan

The aim of this study is to assess the distribution of Agriophyllum squarrosum (L.) in the Western Kazakhstan and Aktobe regions of the Republic of Kazakhstan. This plant, a wild species with significant potential for fodder production, has received limited attention in these areas. The objectives of this research include determining the species' distribution, evaluating its economically valuable potential, conducting phenological observations, and performing biochemical analyses. The study also involved documenting the coordinates of germination sites, introduction experiments, and examining the plant's biological features under cultivation. Methodologically, we focused on monitoring specific locations in the Zhanakala area and Naryn sands (Western Kazakhstan,) and the Shalkar area (Aktobe, Western Kazakhstan), where fodder productivity was measured. In the Zhanakala area and Naryn Sands, Agriophyllum squarrosum produced 6–8 c/ha of green mass and 2–2.5 c/ha of hay, while in the Shalkar area, productivity was lower at 4–5 c/ha of green mass and 1.0–1.5 c/ha of hay. These findings suggest that Agriophyllum squarrosum has potential as a fodder crop in semi-arid regions, with further studies needed to optimize its cultivation.

Asymmetric Atomic Coordination of Platinum Skin Layer on Intermetallic Platinum-Cobalt Particles.

Pt-based intermetallic alloy particles with a Pt skin layer have higher catalytic activity than solid-solution alloy particles and have attracted considerable attention for practical applications in polymer electrolyte fuel cells. However, the reason for the superior performance of intermetallic alloys is not yet fully understood. Because the catalytic reaction proceeds on the topmost surface of the particle, it is necessary to clarify the relationship between the periodic structure of the intermetallic alloy and the Pt atomic coordination on the surface. This study investigated the Pt-Pt interatomic distance of a Pt skin layer formed on intermetallic Pt3Co particles at atomic resolution through precise measurements using scanning transmission electron microscopy and theoretical calculations. The Pt atomic coordination on the surface shows good agreement between experimental observations and theoretical models, although the experimental image is a projection and thus provides indirect results. The theoretical calculation model revealed that structural relaxation at the Pt and Pt3Co interfaces led to two distinct Pt bonding states at the surface, including asymmetric atomic coordination. The asymmetric coordination of the Pt site deepens the d-band center, diversifies the oxygen adsorption energies, and enhances catalytic activity. Further exploration and control of the unique surface Pt coordination environments formed on the periodic structures of intermetallic alloys should reveal promising routes for the development of catalytic particles.

Stabilizing Contorted Doubly-Reduced Tetraphenylene with Heavy Alkali Metal Complexation: Crystallographic and Theoretical Evidence.

The two-fold reduction of tetrabenzo[a,c,e,g]cyclooctatetraene (TBCOT, or tetraphenylene, 1) with K, Rb, and Cs metals reveals a distinctive core transformation pathway: a newly formed C-C bond converts the central eight-membered ring into a twisted core with two fused five-membered rings. This C-C bond of 1.589(3)-1.606(6) Å falls into a single σ-bond range and generates two perpendicular π-surfaces with dihedral angles of 110.3(9)°-117.4(1)° in the 1TR 2- dianions. As a result, the highly contorted 1TR 2- ligand exhibits a "butterfly" shape and could provide different coordination sites for metal-ion binding. The K-induced reduction of 1 in THF affords a polymeric product with low solubility, namely [{K+(THF)}2(1TR 2-)] (K2-1TR 2-). The use of a secondary ligand facilitates the isolation of discrete complexes with heavy alkali metals, [Rb+(18-crown-6)]2[1TR 2-] (Rb2-1TR 2-) and [Cs+(18-crown-6)]2[1TR 2-] (Cs2-1TR 2-). Both internal and external coordination are observed in K2-1TR 2-, while the bulky 18-crown-6 ligand only allows external metal binding in Rb2-1TR 2- and Cs2-1TR 2-. The reversibility of the two-fold reduction and bond rearrangement is demonstrated by NMR spectroscopy. Computational analysis shows that the heavier alkali metals enable effective charge transfer from the 1TR 2-TBCOT dianion, however, the aromaticity of the polycyclic ligand remains largely unaffected.

Understanding non-reducible N2 in the mechanism of Mo-nitrogenase.

In my proposed mechanism of Mo-nitrogenase there are two roles for separate N2 molecules. One N2 diffuses into the reaction zone between Fe2 and Fe6 where a strategic gallery of H atoms can capture N2 to form the Fe-bound HNNH intermediate which is then progressively hydrogenated through intermediates containing HNNH2, NH and NH2 entities and then two NH3 in sequence. The second N2 can be parked in an N2-pocket about 3.2 Å from Fe2 or bind end-on at the exo coordination site of Fe2. This second N2 is outside the reaction zone, not exposed to H atom donors, and so is 'non-reducible'. Here density functional calculations using a 485+ atom model describe the thermodynamics for non-reducible N2 moving between the N2-pocket and the exo-Fe2 position, for the resting state and 19 intermediates in the mechanism. The entropy component is estimated and included. The result is that for all intermediates with ligation by H or NHx at the endo-Fe2 position the free energy for association of non-reducible N2 at exo-Fe2 is negative. There remains some uncertainty about the status of exo-Fe2-N2 during the step in which H2 exchanges with the incoming reducible N2, where at least two unbound molecules are present. At Fe2 it is evident that attainment of octahedral coordination stereochemistry dominates the binding thermodynamics for non-reducible N2. Possibilities for experimental support of these computational conclusions are discussed.

On the substrate turnover rate of NBCe1 and AE1 SLC4 transporters: structure-function considerations.

A transport protein's turnover rate (TOR) is the maximum rate of substrate translocation under saturating conditions. This parameter represents the number of transporting events per transporter molecule (assuming a single transport site) per second (s). From this standpoint, a transporter's TOR is similar to an enzyme's catalytic constant. Knowledge of a transporter's TOR allows comparison of the transport capacity of various transporters at the molecular level as well as the total transport per cell and whole organ levels. Despite this, there is currently a very limited number of transporters, for which TOR has been determined experimentally. In the SLC4 transporter family of CO3 2-/HCO3 - transporters, erythrocyte AE1 (eAE1; SLC4A1) is the only member, for which TOR has been determined (∼50,000 s-1). Whether other SLC4 family members have similar TOR values is currently unknown. Here we report TOR measurements of the electrogenic Na+-CO3 2- cotransporter NBCe1-A (SLC4A4) and the kidney specific AE1 splice variant, kAE1, that play important roles in renal bicarbonate absorption and are mutated in proximal and distal renal tubular acidosis respectively. We have also remeasured the eAE1 TOR value for comparison. NBCe1-A had a TOR value of ∼30,400 s-1 whereas kAE1 and eAE1 had significantly higher values (62,000 s-1 and 60,500 s-1 respectively). We modeled the inward-facing (IF) conformation of NBCe1-A to determine conformational changes during its transport cycle. Comparison of this IF model with our previously determined cryoelectron microscopy (cryoEM) outward-facing (OF) conformation structure, demonstrates that NBCe1-A has an elevator-type transport mechanism with a small vertical ∼5 Å shift of the ion coordination site as we have previously shown for AE1. We speculate that this very small vertical movement plays an important role in contributing to the very high TOR numbers of SLC4 transporters.

Ion Networks in Water-based Li-ion Battery Electrolytes.

ConspectusWater-in-salt electrolytes (WiSEs) are promising electrolytes for next-generation lithium-ion batteries (LIBs), offering critical advantages like nonflammability and improved safety. These electrolytes have extremely high salt concentrations and exhibit unique solvation structures and transport mechanisms dominated by the formation of ion networks and aggregates. These ion networks are central to the performance of WiSEs, govern the transport properties and stability of the electrolyte, deviating from conventional dilute aqueous or organic electrolytes.The availability of free water molecules is significantly reduced in WiSEs, leading to a shift in the solvation environment. Lithium ions (Li+) typically travel with their solvation shells in dilute solutions and form stronger interactions with anions, resulting in the formation of complex ion aggregates. Despite the high viscosity of WiSEs, they exhibit surprisingly high ionic conductivity attributed to the decoupling of viscosity and ionic mobility. Instead of moving through free water, Li+ ions are transported along the pathways formed by the ion networks, minimizing direct solvent interaction and enhancing mobility.Advanced spectroscopic techniques, such as infrared IR pump-probe (IR-PP) and two-dimensional IR (2D-IR) spectroscopy, and molecular dynamics (MD) simulations have illuminated the critical role of these ion networks in facilitating transport. These studies have shown that even at extreme salt concentrations, some water molecules retain properties similar to bulk water, essential for fast ion movement. In WiSEs, bulk-like water molecules form transient hydrogen-bond networks that serve as conduits for Li+ ions, while anion-bound water molecules play a less active role in transport due to their slower dynamics.As the salt concentration increases, the structure of WiSEs becomes more dominated by 3D ion networks. MD simulations reveal that these networks, stabilized by chaotropic anions such as bis(trifluoromethanesulfonyl)imide (TFSI-), disrupt the hydrogen-bonding network of water and provide a stable, interconnected structure that supports the movement of Li+ ions. The formation of these extensive ion networks is critical for maintaining ionic mobility and the electrochemical stability of the electrolyte.The shift from traditional vehicular transport mechanisms to structural diffusion is a hallmark of WiSEs. Li+ ions no longer move with their solvation shells but hop between coordination sites within the ion network. This structural diffusion mechanism enables high ionic mobility despite the reduced presence of water and the increased viscosity of the solution. In conclusion, the formation of ion networks and aggregates in WiSEs not only stabilizes the electrolyte but also drives an unconventional ion transport mechanism. By understanding and controlling these aggregates, WiSEs offer a pathway toward safer, high-performance electrolytes for LIBs and other aqueous energy storage technologies.

Ligand-Induced Intramolecular Cuprophilic and Argentophilic Interactions in Bimetallic Cu(I) and Ag(I) Phosphine Complexes and the Assessment of Their Antityrosinase and Antibacterial Effects.

Binuclear silver(I) and copper(I) complexes, 1 and 5, with bridging diphenylphosphine ligands were prepared. In 1, the silver(I) center is located inside a trigonal plane composed of three phosphorus donors from three separate and bridging dppm ligands. The fourth coordination site is filled with neighboring silver(I) ions. The short Ag···Ag distance, as a result of small bite angles from bridging dppm ligands, was determined to be 2.9463(4) Å. In 5, the Cu···Cu distance is 2.915(6) Å, significantly shorter than that observed in comparable structures. Intramolecular hydrogen bonding interactions in these complexes, such as C-H···F, C-H···O, and O-H···F interactions and π···π interactions, played a significant role in the crystal packing and stability of these molecules in the solid state. Derivatization of 1 and 5 using selected sulfur donor dialkyldithiophosphates gave six novel heteroleptic binuclear complexes. Single crystal X-ray diffraction studies of five of these complexes revealed interesting structural features, including strong metallophilic interactions in 1 and 5 and multiple intramolecular and intermolecular hydrogen bonding interactions. The antibacterial activities of complexes 1, 2, 3, 7, and 8 were also screened against gram-positive (Staphylococcus aureus PTCC 1112) and gram-negative (Escherichia coli PTCC 1330) bacteria. Antityrosinase and hemolytic effects of the selected compounds were also determined. Time-dependent density functional theory (TD-DFT), interaction region indicator (IRI), and fuzzy atom bond order (FBO) analyses of the selected complexes provided insights into the electronic and structural characteristics of the metal complexes.

Fine-Tuning the Anisotropies of Air-Stable Single-Molecule Magnets Based on Macrocycle Ligands.

Air-stable single-molecule magnets (SMMs) can be obtained by confining DyIII ion in a D6h coordination environment; however, most of the current efforts were focused on modifying the rigidity of the macrocycle ligand. Herein, we attempt to assemble air-stable SMMs based on macrocycles with a replaceable coordination site. By using an in situ 1 + 1 Schiff-base reaction of dialdehyde with diamine, three air-stable SMMs have been obtained in which one of the equatorial coordination sites can be varied from -NH- (for Dy-NH), -O- (for Dy-O), and -NMe- (for Dy-NMe). Complex Dy-NH shows a less distorted D6h symmetry and an anisotropy energy barrier of 1270 K. For complex Dy-O, the coordination site of -O- gives a relatively longer coordination bond but a comparable energy barrier in contrast with that of Dy-NH. In the case of complex Dy-NMe, although the -NMe-group gives a very long coordination bond, the large steric effect on the -NMe- group enforces a larger distortion of the D6h coordination geometry, resulting in the fast quantum tunneling of the magnetization that shortcuts the thermal relaxation process; therefore, Dy-NMe shows a lower energy barrier. This study provides a new strategy for modifying the coordinate site on the equatorial plane of D6h symmetry to fine-tune the structure and magnetic anisotropy of SMMs.

Tipping the balance between twist and chair ligand conformers in multinuclear ethylzinc cyclophosphazenates.

Hexaanionic cyclophosphazenate ligands [(RN)6P3N3]6- provide versatile platforms for the assembly of multinuclear metal arrays due to their multiple coordination sites and highly flexible ligand core structure. This work investigates the impact of incrementally increasing the steric demand of the ligand periphery on the coordination behavior of ethylzinc arrays. It shows that the increased congestion around the ligand sites is alleviated by progressive condensation with the elimination of diethylzinc. The condensation is accompanied by a switch in ligand conformation: the phosphazene ring of the methyl derivative adopts the chair conformer in the dimeric complex (EtZn)12[(RN)6P3N3]2, while the more sterically demanding isobutyl derivative exhibits twist conformers in both the monomeric complex (EtZn)6[(iBuN)6P3N3] and the condensed dimer (EtZn)8Zn2[(iBuN)6P3N3]2. Ethyl and propyl derivatives mark a tipping point: the dimeric complex (EtZn)12[(RN)6P3N3]2 exhibits the chair conformation and is observed in solution and within the stabilising environment of a co-crystal. However, when crystallising in pure form, it transforms with the loss of one equivalent of Et2Zn into the collapsed dimer (EtZn)10Zn[(RN)6P3N3]2 which features the twist conformer.

Multistimuli Responsive and Self-Healing Zn (II)-Inosine Supramolecular Metal-Organic Gel: Phase Selective Gelation and Application as Light-Responsive Schottky Barrier Diode

Utilization of naturally available biomolecules such as nucleosides with several coordination sites as organic counterparts for the synthesis of multifunctional self-assembled metal-organic gels is important, considering the time and efforts...

Multihalogenated Zn phthalocyanine as a precursor for porous Zn-N4-C carbons toward electrocatalytic oxygen reduction.

Multihalogenated Zn phthalocyanine, a commonly used color filter pigment, when pyrolyzed under NH3 atmosphere, produces porous carbon powders containing Zn-N4 coordination sites that exhibit high electrocatalytic O2 reduction reaction (ORR) performance with long-term stability and chemical resistance.

Sensitive detection of formaldehyde via a luminescent distorted Eu4L4 tetrahedral cage.

A distorted low-symmetry Eu4L4 tetrahedral cage was fabricated through the self-assembly of europium ions and C3-symmetric bowl-shaped ligands containing a phosphangulene core. X-ray crystallography confirmed its unique architecture, featuring significant structural distortion and solvent-accessible coordination sites. This cage showcases exceptional luminescence-based sensitivity for formaldehyde detection compared to other analogs, achieving an impressive detection limit of 19.4 ppb.

Mode of Metal Ligation Governs Inhibition of Carboxypeptidase A.

Carboxypeptidase is a Zn-dependent protease that specifically recognises and hydrolyses peptides with a hydrophobic side chain at the C-terminal residue. According to hydrolysis mechanisms proposed in the literature, catalysis requires a water molecule to be close to the Zn ion so as to be activated as a nucleophile. Among small molecules that resemble the slowly hydrolysed Gly-Tyr peptide, which have been previously designed as inhibitors and characterised structurally, a variant with the terminal amino acid in a D-configuration has been the most effective. Our molecular dynamics simulations of carboxypeptidase complexed with different variants of those inhibitor ligands as well as variants of the Gly-Tyr peptide show that the strength of the inhibitory effect is not related to the binding strength of the ligand. Our data rather support an earlier notion that the inhibition is, at least partially, due to blocking a coordination site at the Zn ion by the ligand coordinating the metal ion in a bidentate fashion.

Metal-Independent Correlations for Site-Specific Binding Energies of Relevant Catalytic Intermediates.

Establishing energy correlations among different metals can accelerate the discovery of efficient and cost-effective catalysts for complex reactions. Using a recently introduced coordination-based model, we can predict site-specific metal binding energies (ΔE M) that can be used as a descriptor for chemical reactions. In this study, we have examined a range of metals including Ag, Au, Co, Cu, Ir, Ni, Os, Pd, Pt, Rh, and Ru and found linear correlations between predicted ΔE M and adsorption energies of CH and O (ΔE CH and ΔE O) at various coordination environments for all the considered metals. Interestingly, all the metals correlate with one another under specific surface site coordination, indicating that different metals are interrelated in a particular coordination environment. Furthermore, we have tested and verified for PtPd- and PtIr-based alloys that they follow a similar behavior. Moreover, we have expanded the metal space by taking some early transition metals along with a few s-block metals and shown a cyclic behavior of the adsorbate binding energy (ΔE A) versus ΔE M. Therefore, ΔE CH and ΔE O can be efficiently interpolated between metals, alloys, and intermetallics based on information related to one metal only. This simplifies the process of screening new metal catalyst formulations and their reaction energies.

Precise manipulation of iron spin states in single-atom catalytic membranes for singlet oxygen selective production.

Heterogeneous single-atom catalysts are attracting substantial attention for selectively generating singlet oxygen (1O2). However, precise manipulation of atom coordination structures remains challenging. Here, the fine coordination structure of iron single-atom carbon-nitride catalysts (Fe-CNs) was manipulated by precisely tuning the heating rate with 1 °C min-1 difference. Multiple techniques in combination with density functional theory (DFT) calculations reveal that FeN6 coordination sites with high Fe spin states promote the adsorption, electron transfer, and dissociation of peroxymonosulfate (PMS), resulting in nearly 100% selection of 1O2 generation. A lamellar single atom catalytic membrane is constructed, exhibiting high permeance, high degradation, high-salinity resistance and sustained operation stability. This work provides ideas for regulating spin states of the metal site to fabricate catalysts with selective 1O2 generation for membrane separation and environment catalysis applications.

Unveiling Active Al3+ Sites for Ethanol Dehydration on γ-Al2O3 with Solid-State Nuclear Magnetic Resonance Spectroscopy.

γ-Al2O3 is a crucial catalyst widely used in industrial alcohol dehydration processes. However, the specific nature of its active sites has remained unclear. In this study, we utilize two-dimensional heteronuclear correlation solid-state nuclear magnetic resonance and density functional theory calculations to uncover the active Al sites on the surface of γ-Al2O3 that facilitate ethanol dehydration. We show the formation of stable pentacoordinated AlV-ethanol complexes upon the adsorption of ethanol on the tetracoordinated AlIV sites. This interaction significantly enhances synergy with adjacent AlV-OH sites, resulting in a marked reduction of the activation energy barrier for ethene production. Furthermore, we reveal an interchange between AlIV and AlV-OH species, allowing hexacoordinated AlVI-OH sites to participate in the dehydration pathway through the migration of ethanol between these coordination sites.

Synthesis and luminescence of 3-(pyridine-2-yl)-1,2,4-triazine-based Ir(III) complexes

A series of novel iridium(III) complexes containing 5-N-(aryl)-amino- or 5-cycloamino-3-(pyridine-2-yl)-1,2,4-triazine ligands was obtained. These complexes exhibited red luminescence in solution as well as in the solid state. Based on the DFT studies it was suggested that N(2) atom of the 1,2,4-triazine core is preferable to N(4) one as the coordination site in the complexes of Ir(III).