Channel Molecules Research Articles

Spontaneous Transition between Multiple Conductance States and Rectifying Behaviors in an Artificial Single‐Molecule Funnel

It has long been an aspirational goal to create artificial channel structures that replicate the feat achieved by ion channel proteins. Biological ion channels occasionally demonstrate multiple conductance states (known as subconductance), remaining a challenging property to achieve in artificial channel molecules. We report a funnel‐shaped single‐molecule channel constructed by an electron‐deficient macrocycle and two electron‐deficient aromatic imide arms. Planar lipid bilayer measurements reveal distinct current recordings, including a closed state, two conducting states, and spontaneous transitions between the three states, resembling the events seen in biological ion channels. The transitions result from conformational changes induced by chloride transport in the channel molecule. Both opening states show a non‐linear and rectifying I‐V relationship, indicating voltage‐dependent transport due to the asymmetrical channel structure. This work could enhance our understanding of ion permeation and channel opening mechanism.

Diabetes Insipidus can Increase Patient Security: A Review

Diabetes insipidus (DI) is a condition marked by polydipsia (drinking more than three liters of fluid per day) and a high hypotonic urine production (greater than 50 milliliters per kilogram of body weight per 24 hours). The hypothalamus or pituitary gland's insufficient production of arginine vasopressin (AVP) and its consequent inadequate secretion cause central DI. In addition to central DI, different primary forms (of renal origin) or secondary forms of polyuria may be the cause of additional underlying etiologies of DI. These variations are all part of the Polyuria Polydipsia Syndrome. This is crucial since different treatment plans have different effects, and using the incorrect one can be harmful. Since its discovery in 1942, diabetes insipidus has been linked to pregnancy complications in at least 4 out of every 100,000 patients.The regulatory mechanisms behind CDI and NDI are then discussed, with an emphasis on the water channel molecule aquaporin 2 (AQP2) and the vasopressin receptor 2 (V2R) regulatory axis. (DI) is a complicated pregnancy condition that can affect about 1 in 30,000 pregnancies. It is a heterogeneous illness that most commonly manifests as polyuria and polydipsia. The pathophysiology of DI during pregnancy determines the course of treatment; DI without AVP can be managed with desmopressin (DDAVP); DI with AVP resistance necessitates investigation of the underlying reasons. Previously known as diabetes insipidus (DI), arginase vasopressin disorder is a disease condition that causes electrolyte imbalances by either reducing the secretion of antidiuretic hormone (ADH, also known as vasopressin or AVP) or by reducing the body's response to ADH. Both arginine vasopressin deficiency (AVP-D; formerly known as central DI) and arginine vasopressin resistance (AVP-R; formerly known as nephrogenic DI) are forms of arginine vasopressin disease, with both congenital and acquired origins. Lithium increased the amount of lipid peroxidation (LPO) and reactive oxygen species (ROS) in the kidney.

Lymphocytic colitis can be transcriptionally divided into channelopathic and inflammatory lymphocytic colitis.

The pathobiology of the non-destructive inflammatory bowel disease (IBD) lymphocytic colitis (LC) is poorly understood. We aimed to define an LC-specific mucosal transcriptome to gain insight into LC pathology, identify unique genomic signatures, and uncover potentially druggable disease pathways. We performed bulk RNA-sequencing of LC and collagenous colitis (CC) colonic mucosa from patients with active disease, and healthy controls (n=4-10 per cohort). Differential gene expression was analyzed by gene-set enrichment and deconvolution analyses to identify pathologically relevant pathways and cells, respectively, altered in LC. Key findings were validated using reverse transcription quantitative PCR and/or immunohistochemistry. Finally, we compared our data with a previous cohort of ulcerative colitis and Crohn's disease patients (n=4 per group) to distinguish non-destructive from classic IBD. LC can be subdivided into channelopathic LC, which is governed by organic acid and ion transport dysregulation, and inflammatory LC, which is driven by microbial immune responses. Inflammatory LC displays an innate and adaptive immunity that is limited compared to CC and classic IBD. Conversely, we noted a distinct induction of regulatory non-coding RNA species in inflammatory LC samples. Moreover, compared with CC, water channel and cell adhesion molecule gene expression decreased in channelopathic LC, whereas it was accentuated in inflammatory LC and associated with reduced intestinal epithelial cell proliferation. We conclude that LC can be subdivided into channelopathic LC and inflammatory LC that could be pathomechanistically distinct subtypes despite their shared clinical presentation. Inflammatory LC exhibits a dampened immune response compared to CC and classic IBDs. Our results point to regulatory micro-RNAs as a potential disease-specific feature that may be amenable to therapeutic intervention.

Influence of molecular orientation on the photodissociation process of LiH molecules

AbstractRegulation of photodissociation dynamics of oriented LiH molecules in different dissociation channels is proposed based on time dependent quantum wave packet theory. The enhancement of molecular orientation on the photodissociation of LiH is obvious with our theoretical scheme. The results show that the molecular orientation in the ground state has a great effect on the angular distributions of wave packets. By using the proper laser pulses and controlling the polarization direction of the laser pulses, the enhancement of the photodissociation could be realized. After the molecular orientation, an optimal dissociation channel is observed with an improved dissociation probability. Compared with the results without molecular orientation, the maximal dissociation probability is increased by 8.1% in the indirect dissociation channel and 30.7% in the direct dissociation channel. The enhancement effect is more obvious in the direct dissociation channel, which provides a possible method to manipulate the dissociation of LiH molecules experimentally. Additionally, the photodissociation process of LiH also relies on the electric intensity and delay time of two pump pulses.

P112 Lymphocytic colitis can be transcriptionally divided into channelopathic and inflammatory lymphocytic colitis

Abstract Background The pathobiology of the non-destructive inflammatory bowel disease (IBD) lymphocytic colitis (LC) is poorly understood. We aimed to define an LC-specific mucosal transcriptome to gain insight into LC pathology, identify unique genomic signatures, and uncover potentially druggable disease pathways. Methods We performed bulk RNA-sequencing of LC and collagenous colitis (CC) colonic mucosa from patients with active disease, and healthy controls (n=4-10 per cohort). Differential gene expression was analyzed by gene-set enrichment and deconvolution analyses to identify pathologically relevant pathways and cells, respectively, altered in LC. Key findings were validated using reverse transcription quantitative PCR and/or immunohistochemistry. Finally, we compared our data to a previous cohort of ulcerative colitis and Crohn’s disease patients (n=4 per group) to distinguish non-destructive from classic IBD. Results LC can be subdivided into channelopathic LC, which is governed by organic acid and ion transport dysregulation; and inflammatory LC, which is driven by microbial immune responses. Inflammatory LC displays an innate and adaptive immunity that is limited compared to CC and classic IBD (Fig. 1). Conversely, we noted a distinct induction of regulatory non-coding RNA species in inflammatory LC samples. Moreover, compared to CC, water channel and cell adhesion molecule gene expression decreased in channelopathic LC, whereas it was accentuated in inflammatory LC and associated with reduced intestinal epithelial cell proliferation. Conclusion We conclude that LC can be subdivided into channelopathic LC and inflammatory LC that could be pathomechanistically distinct subtypes despite their shared clinical presentation. Inflammatory LC exhibits a dampened immune response compared to CC and classic IBDs. Our results point to regulatory micro-RNAs as a potential disease-specific feature that may be amenable to therapeutic intervention.

Mechanistic insights into microwave-accelerated permeation through graphene-based membranes

Two-dimensional (2D) membranes, composed of stacked 2D nanomaterials, are increasingly utilized in separation fields due to their structured interlayer channels and ease of modification. The application of microwave technology to 2D membrane separation enhances permeability, but the unclear strengthening mechanism limits the further applications of this technique. This study aims to elucidate the fundamental principle behind microwave-accelerated permeability by investigating the performance of two distinct 2D membranes in response to microwaves: a microwave-transparent graphene oxide (GO) membrane and a microwave-absorbing GO-based membrane doped with molybdenum disulfide (MoS2-GO). Experimental results demonstrate that compared to conventional heating, microwave irradiation amplifies water and ethanol permeation flux through the GO membrane by 122% and 154%, respectively, without observed changes in membrane structure via SEM, XRD, and Raman analyses. In addition, the microwave accelerated permeation also occurs (by 110%) when Rhodamine B - aqueous solution was used as feed liquid, while the rejection rate was remained at above 99%, indicating the promising applications of microwave technology in sewage treatment. Further experiments show that the microwave-induced augmentation of water/ethanol permeation through the GO membrane was primarily governed by the dielectric loss values of the feed liquid. In contrast, this dependence vanished in the MoS2-GO membrane, indicating that accelerated permeation was mainly determined by the interaction between microwaves and diffusing molecules in the 2D channels, disrupted by microwave absorbing MoS2 in the latter case. These findings offer comprehensive insights into the enhancement of membrane permeation induced by microwave irradiation.

A unimolecular artificial cation channel based on cascaded hydrated acid groups.

A cation channel possessing cascaded hydrated acid groups has been successfully constructed using pillar[5]arene integrated with dual cyclodextrins. As a proof-of-concept, the secondary side of cyclodextrin substituted by 24 -CO2H groups presents high coordination sites, which helps hydrated cations to quickly dehydrate and accelerates efficient cation transport (Rb+ > Cs+ > K+ > Na+ > Li+). Notably, benefitted by the protonation and deprotonation of -CO2H groups, ion permeation activity of the channel molecules under acidic condition (pH = 6.0) is 2.8 times higher than that under alkaline conditions (pH = 8.0), exhibiting pH-modulated property and promising potential in building intelligent artificial ion channels with customized features.

Stroma-associated FSTL3 is a factor of calcium channel-derived tumor fibrosis

Hepatocellular carcinoma (HCC) is the most widespread histological form of primary liver cancer, and it faces great diagnostic and therapeutic difficulties owing to its tumor diversity. Herein, we aim to establish a unique prognostic molecular subtype (MST) and based on this to find potential therapeutic targets to develop new immunotherapeutic strategies. Using calcium channel molecules expression-based consensus clustering, we screened 371 HCC patients from The Cancer Genome Atlas to screen for possible MSTs. We distinguished core differential gene modules between varying MSTs, and Tumor Immune Dysfunction and Exclusion scores were employed for the reliable assessment of HCC patient immunotherapeutic response rate. Immunohistochemistry and Immunofluorescence staining were used for validation of predicted immunotherapy outcomes and underlying biological mechanisms, respectively. We identified two MSTs with different clinical characteristics and prognoses. Based on the significant differences between the two MSTs, we further identified Follistatin-like 3 (FSTL3) as a potential indicator of immunotherapy resistance and validated this result in our own cohort. Finally, we found that FSTL3 is predominantly expressed in HCC stromal components and that it is a factor in enhancing fibroblast-M2 macrophage signaling crosstalk, the function of which is relevant to the pathogenesis of HCC. The presence of two MSTs associated with the calcium channel phenotype in HCC patients may provide promising directions for overcoming immunotherapy resistance in HCC, and the promotion of FSTL3 expressed in stromal components for HCC hyperfibrosis may be responsible for the poor response rate to immunotherapy in Cluster 2 (C2) patients.

Assembly of Cell-Free Synthesized Ion Channel Molecules in Artificial Lipid Bilayer Observed by Atomic Force Microscopy.

Artificial lipid bilayer systems, such as vesicles, black membranes, and supported lipid bilayers (SLBs), are valuable platforms for studying ion channels at the molecular level. The reconstitution of the ion channels in an active form is a crucial process in studies using artificial lipid bilayer systems. In this study, we investigated the assembly of the human ether-a-go-go-related gene (hERG) channel prepared in a cell-free synthesis system. AFM topographies revealed the presence of protrusions with a uniform size in the entire SLB that was prepared with the proteoliposomes (PLs) incorporating the cell-free-synthesized hERG channel. We attributed the protrusions to hERG channel monomers, taking into consideration the AFM tip size, and identified assembled structures of the monomer that exhibited dimeric, trimeric, and tetrameric-like arrangements. We observed molecular images of the functional hERG channel reconstituted in a lipid bilayer membrane using AFM and quantitatively evaluated the association state of the cell-free synthesized hERG channel.

Mitochondrial Artificial K+ Channel Construction Using MPTPP@5F8 Nanoparticles for Overcoming Cancer Drug Resistance via Disrupting Cellular Ion Homeostasis.

Mitochondrial potassium ion channels have become a promising target for cancer therapy. However, in malignant tumors, their low expression or inhibitory regulation typically leads to undesired cancer therapy, or even induces drug resistance. Herein, this work develops an in situ mitochondria-targeted artificial K+ channel construction strategy, with the purpose to trigger cancer cell apoptosis by impairing mitochondrial ion homeostasis. Considering the fact that cancer cells have a lower membrane potential than that of normal cells, this strategy can selectively deliver artificial K+ channel molecule 5F8 to the mitochondria of cancer cells, by using a mitochondria-targeting triphenylphosphine (TPP) modified block polymer (MPTPP) as a carrier. More importantly, 5F8 can further specifically form a K+ -selective ion channel through the directional assembly of crown ethers on the mitochondrial membrane, thereby inducing mitochondrial K+ influx and disrupting ions homeostasis. Thanks to this design, mitochondrial dysfunction, including decreased mitochondrial membrane potential, reduced adenosine triphosphate (ATP) synthesis, downregulated antiapoptotic BCL-2 and MCL-1 protein levels, and increased reactive oxygen species (ROS) levels, can further effectively induce the programmed apoptosis of multidrug-resistant cancer cells, no matter in case of pump or nonpump dependent drug resistance. In short, this mitochondria-targeted artificial K+ -selective ion channel construction strategy may be beneficial for potential drug resistance cancer therapy.

The physical basis of osmosis.

Osmosis is an important force in all living organisms, yet the molecular basis of osmosis is widely misunderstood as arising from diffusion of water across a membrane separating solutions of differing osmolarities, and hence different water concentrations. In 1923, Peter Debye proposed a physical model for a semipermeable membrane emphasizing the repulsive forces between solute molecules and membrane that prevent the solute from entering the membrane. His work was hardly noticed at the time and slipped out of view. We show that Debye's analysis of van 't Hoff's law for osmotic equilibrium also provides a consistent and plausible mechanism for osmotic flow. A difference in osmolyte concentrations in solutions separated by a semipermeable membrane leads to different pressures at the two water-membrane interfaces because the total repulsive force between solute molecules and the membrane is different at the two interfaces. Water is therefore driven through the membrane for exactly the same reason that pure water flows in response to an imposed hydrostatic pressure difference. In this paper, we present the Debye model in both equilibrium and flow conditions. We point out its applicability regardless of the nature of the membrane with examples ranging from the predominantly convective flow of water through synthetic membranes and capillary walls to the purely diffusive flow of independent water molecules through a lipid bilayer and the flow of a single-file column of water molecules in narrow protein channels.

Analgesic Effect of the Lysine-Containing Short Peptide Is Due to Modulation of the NaV1.8 Channel Activation Gating System.

The present work continues our recent series of articles that aim to elucidate the ligand-receptor binding mechanism of short cationic peptides to the NaV1.8 channel in the nociceptive neuron. The applied methodological approach has involved several methods: the patch-clamp experimental evaluation of the effective charge of the NaV1.8 channel activation gating system, the organotypic tissue culture method, the formalin test, and theoretical conformational analysis. The lysine-containing short peptide Ac-KEKK-NH2 has been shown to effectively modulate the NaV1.8 channel activation gating system. As demonstrated by the organotypic tissue culture method, the studied short peptide does not trigger the downstream signaling cascades controlling neurite outgrowth and should not be expected to evoke adverse side effects. Conformational analysis of the Ac-KEKK-NH2 molecule has revealed that the distances between the positively charged amino groups of the lysine side chains are equal to 11-12 Å. According to the previously suggested mechanism of ligand-receptor binding of short peptides to the NaV1.8 channel molecule, Ac-KEKK-NH2 should exhibit an analgesic effect, which has been confirmed by the formalin test. The data obtained unequivocally indicate that the studied lysine-containing short peptide is a promising candidate for the role of a novel analgesic medicinal substance.

Voltage-Mediated Water Dynamics Enables On-Demand Transport of Sugar Molecules in Two-Dimensional Channels.

The constructing of artificial channels with gating functions is an important undertaking for gaining insight into biological process and achieving efficient bionic functions. Typically, controllable transport within such channels relies on either electrostatic or specific interactions between the transporting species and the channel. However, for molecules with weak interactions with the channel, achieving precise gating of the transport remains a significant challenge. In this regard, this study proposes a voltage gating membrane of two-dimensional channels that selectively transport of neutral molecules glucose with a dimension of 0.60 nm. The permeation of glucose is switched on/off by electrochemically manipulating the water dynamics in the nanochannel. Voltage driven-intercalation of ion into the two-dimensional channel causes water to stratify and move closer to the channel walls, thereby resulting in the channel center being emptier for glucose diffusion. Due to the sub-nanometer size dimension of the channel, selective permeation of glucose over sucrose is also achieved in this approach.

Construction of Dual-Channel Water Transport in Mesoporous Silica Low Humidity Sensors to Achieve High Sensitivity.

In this paper, strong hydrophilic poly(ionic liquid)s (PILs) are selectively grafted on different positions (mesoporous channels and outer surface) of mesoporous silica via thiol-ene click chemical reaction. The purposes of selective grafting are on the one hand, to explore the differences of adsorption and transportation of water molecules in mesoporous channels and on the outer surface, and on the other hand, to combine the two approaches (intra-pore grafting and external surface grafting) to reasonably design SiO2 @PILs low humidity sensing film with synergetic function to achieve high sensitivity. The results of low relativehumidity （RH）sensing test show that the sensing performance of humidity sensor based on mesoporous silica grafted with PILs in the channels is better than that of humidity sensor based on mesoporous silica grafted with PILs on the outer surface. Compared with water molecules transport single channel, the construction of dual-channel water transport significantly improves the sensitivity of the low humidity sensor, and the response of the sensor is up to 4112% in the range of 7-33% RH. Moreover, the existence of micropores and the formation of dual-channel water transport affect the adsorption/desorption behaviors of the sensor under different humidity ranges, especially below 11% RH.

An Artificial Single Molecular Channel Showing High Chloride Transport Selectivity and pH-Responsive Conductance.

Inspired by the unique structure and function of the natural chloride channel (ClC) selectivity filter, we present herein the design of a ClC-type single channel molecule. This channel displays high ion transport activity with half-maximal effective concentration, EC50 , of 0.10 μM, or 0.075 mol % (channel molecule to lipid ratio), as determined by fluorescent analysis using lucigenin-encapsulated vesicles. Planar bilayer lipid membrane conductance measurements indicated an excellent Cl- /K+ selectivity with a permeability ratio P /P up to 12.31, which is comparable with the chloride selectivity of natural ClC proteins. Moreover, high anion/anion selectivity (P /P =66.21) and pH-dependent conductance and ion selectivity of the channel molecule were revealed. The ClC-like transport behavior is contributed by the cooperation of hydrogen bonding and anion-π interactions in the central macrocyclic skeleton, and by the existence of pH-responsive terminal phenylalanine residues.

An Artificial Single Molecular Channel Showing High Chloride Transport Selectivity and pH‐Responsive Conductance

AbstractInspired by the unique structure and function of the natural chloride channel (ClC) selectivity filter, we present herein the design of a ClC‐type single channel molecule. This channel displays high ion transport activity with half‐maximal effective concentration, EC50, of 0.10 μM, or 0.075 mol % (channel molecule to lipid ratio), as determined by fluorescent analysis using lucigenin‐encapsulated vesicles. Planar bilayer lipid membrane conductance measurements indicated an excellent Cl−/K+ selectivity with a permeability ratio P /P up to 12.31, which is comparable with the chloride selectivity of natural ClC proteins. Moreover, high anion/anion selectivity (P /P =66.21) and pH‐dependent conductance and ion selectivity of the channel molecule were revealed. The ClC‐like transport behavior is contributed by the cooperation of hydrogen bonding and anion–π interactions in the central macrocyclic skeleton, and by the existence of pH‐responsive terminal phenylalanine residues.

Inactivation of epithelial sodium ion channel molecules serves as effective diagnostic biomarkers in clear cell renal cell carcinoma.

Non-voltage-gated sodium channel, also known as the epithelial sodium channel (ENaC), formed by heteromeric complexes consisting of SCNN1A, SCNN1B, and SCNN1G, is responsible for maintaining sodium ion and body fluid homeostasis in epithelial cells. However, no systematic study of SCNN1 family members has been conducted in renal clear cell carcinoma (ccRCC) to date. To investigate the abnormal expression of SCNN1 family in ccRCC and its potential correlation with clinical parameters. The transcription and protein expression levels of SCNN1 family members in ccRCC were analyzed based on the TCGA database, and were confirmed by quantitative RT-PCR and immunohistochemical staining assays, respectively. The areaunder curve (AUC) was used to evaluate the diagnostic value of SCNN1 family members for ccRCC patients. The mRNA and protein expression of SCNN1 family members was significantly downregulated in ccRCC compared with normal kidney tissues, which might be due to DNA hypermethylation in the promoter region. It is worth noting that the AUC of SCNN1A, SCNN1B, and SCNN1G were 0.965, 0.979, and 0.988 based on the TCGA database (p < 0.0001), respectively. The diagnostic value was even higher when combing these three members together (AUC = 0.997, p < 0.0001). Intriguingly, the mRNA level of SCNN1A was significantly lower in females compared with males, while SCNN1B and SCNN1G were increased with the progression of ccRCC and remarkably associated with a worse outcome for patients. The aberrantly decrease of SCNN1 family members might serve as valuable biomarkers for the diagnosis of ccRCC.

PO-01-206 MOLECULAR MODELING OF CLINICAL KCNJ2 MUTATIONS REVEALS STRUCTURE-FUNCTION IMPACT ON PIP2 BINDING SITE

Binding phosphatidylinositol 4,5-bisphosphate (PIP2) is essential for Kir2.1(encoded by KCNJ2), function. Disease associated KCNJ2 mutations, such as those associated with Andersen-Tawil Syndrome (ATS), may exert molecular dysfunction by interrupting PIP2 binding, however a full-length molecular model of Kir2.1 has not been developed to explore this hypothesis. Elucidate the molecular structure of Kir2.1 and determine the functional impact of clinical KCNJ2 mutations on PIP2 binding using experimental and improved molecular dynamic (MD) method. Whole-cell patch clamp experiments of WT-Kir2.1 and selected mutations were performed on stably transfected HEK293 cells using a standard protocol. A full-length Kir2.1 tetramer model (open and closed conformational states) based on Kir2.2 cryo-EM structure using MOE was created. Mutations (R67Q, G300D, R218L) were individually introduced to the channel, and a mutagenesis analysis was performed. Initially, MD simulation for 100ns was performed for wild-type (WT) and mutated structures (GROMACS software). We expanded the model to include +/- bound PIP2. Due to > 77% degree of homology of Kir2.2 (6m84) with Kir2.1, we developed a MD protocol with Kir2.2 as test system. The 2.5% free PIP2 molecules were released into the membrane and MD simulation was performed for 700ns using Amber software. Homomeric WT demonstrated normal Kir2.1 function while mutations G300D, R67Q, and R218L showed complete loss of function. Mutational analysis revealed that residue changes result in disruption of hydrogen bonding and affects the structural conformation at the residue sight and caused fluctuation of residues in other regions, i.e., selectivity filter and pore domain. The improved MD protocol validated Kir2.2 PIP2 binding sites. Moreover, we found mutation disruption of hydrogen bonds and hydrophobic interaction analysis between the channel and PIP2 molecules revealed significant structural changes. We developed the first full length MD model of Kir2.1 and found that ATS KCNJ2 mutations disrupt normal conformation and hydrogen bonding. Further, we validated PIP2 binding sites which illustrate the robustness of our method, and this technique can be applied to delineate Kir2.1 molecular PIP2 binding sites. Combined with experimental validation, our modeling will increase our understanding of structure-function relationships of KCNJ2 clinical mutations.

Vapor-Like Water in the NU-1000 Zr-MOF: A Molecular Level Understanding of Balanced Hydrophobicity in Humid Conditions

While the structural features and tunability of metal–organic frameworks (MOFs) make them promising materials for chemical warfare agent (CWA) hydrolysis, their stability and performance in conditions of varying humidity is an unsolved challenge. Understanding what design rules enable lasting hydrolytic functionality in evolving field conditions is consequently essential to developing practical MOFs for such applications. In this work, molecular dynamics simulations are carried out to examine the behavior of water at various loadings in the Zr-based MOF NU-1000. With its strong node-linker bonds, expansive pores, and balanced hydrophobicity, pristine NU-1000 possesses the characteristic attributes for structural stability and hydrolytic efficiency in the presence of environmental water. Adsorption and residence time results reveal that while NU-1000 is hydrophilic enough to allow water to adsorb, internal hydrophobicity discourages the distribution of H2O molecules to active sites at the metal nodes. Water–water interactions take precedence in NU-1000, forming a water cluster that grows with loading and distracts individual molecules from diffusing throughout the framework. On the other hand, self-diffusion coefficients and radial distribution function patterns suggest a lack of hydrogen bonding, with the clustered molecules having faster diffusion and less ordering than that of liquid-phase water. The limited interactions between water and the metal nodes indicate a lower likelihood of competition for sites impeding target species hydrolysis in NU-1000. Additionally, the partially vapor structural state of the aggregated water molecules in the expansive NU-1000 channels indicates a lower likelihood of pore filling by water that interferes with target species adsorption and diffusion. Such results evidence a strong potential of the NU-1000 Zr-MOF for superior performance in hydrolysis applications like toxic chemical decomposition.

Assembly Rules and Dehydration Mechanism of an Unconventional Hydrate: On the Complexity of the Hydrates of Creatine Phosphate Sodium

Unconventional hydrates with differently bound water molecules and related mazy intermolecular interaction networks need systematic investigation. The assembly rules, interaction analysis, and dehydration behavior can be dramatically more complicated when compared with those of common hydrates. In this work, creatine phosphate sodium (CPS) was selected as a model compound representing unconventional hydrates. The packing mode and the role of water molecules related to the dehydration mechanism were explored by the combination of experimental (diffraction, thermal, microscopy) and quantum chemistry computational (interplay visualization, binding energy calculation) methods. It was observed that in the structure of CPS heptahydrate and heminonahydrate, channel, isolated-site, and ion-associated water molecules exist simultaneously, constructing the framework via the coordination bond and hydrogen bond. The binding energy of some ion-coordinated water molecules is lower than that of hydrogen-bonded ones while that of some isolated-site water molecules is lower when compared with that of channel ones, which is counterintuitive. Moreover, the diverse types and locations of water molecules, complicated H2O···H2O interactions, and the trade-off between CPS···H2O and H2O···H2O lead to multistage, variable, and binding-energy-independent dehydration behavior. This work sheds light on the novel structure and variable dehydration mechanism of complicated hydrate systems and inspires the particularity and further investigation of unconventional hydrates.