Site-Specific Conjugation of Native Antibody: Transglutaminase-Mediated Modification of a Conserved Glutamine While Maintaining the Primary Sequence and Core Fc Glycan via Trimming with an Endoglycosidase.

A versatile chemo-enzymatic tool to site-specifically modify native (nonengineered) antibodies is using transglutaminase (TGase, E.C. 2.3.2.13). With various amines as cosubstrates, this enzyme converts the unsubstituted side chain amide of glutamine (Gln or Q) in peptides and proteins into substituted amides (i.e., conjugates). A pleasant surprise is that only a single conserved glutamine (Gln295) in the Fc region of IgG is modified by microbial TGase (mTGase, EC 2.3.2.13), thereby providing a highly specific and generally applicable conjugation method. However, prior to the transamidation (access to the glutamine residue by mTGase), the steric hindrance from the nearby conserved N-glycan (Asn297 in IgG1) must be reduced. In previous approaches, amidase (PNGase F, EC 3.5.1.52) was used to completely remove the N-glycan. However, PNGase F also converts a net neutral asparagine (Asn297) to a negatively charged aspartic acid (Asp297). This charge alteration may markedly change the structure, function, and immunogenicity of an IgG antibody. In contrast, in our new method presented herein, the N-glycan is trimmed by an endoglycosidase (EndoS2, EC 3.2.1.96), hence retaining both the core N-acetylglucosamine (GlcNAc) moiety and the neutral asparaginyl amide. The trimmed glycan also reduces or abolishes Fc receptor-mediated functions, which results in better imaging agents by decreasing nonspecific binding to other cells (e.g., immune cells). Moreover, the remaining core glycan allows further derivatization such as glycan remodeling and dual conjugation. Practical and robust, our method generates conjugates in near quantitative yields, and both enzymes are commercially available.

Chemoenzymatic labeling of DNA methylation patterns for single-molecule epigenetic mapping.

DNA methylation, specifically, methylation of cytosine (C) nucleotides at the 5-carbon position (5-mC), is the most studied and significant epigenetic modification. Here we developed a chemoenzymatic procedure to fluorescently label non-methylated cytosines in CpG context, allowing epigenetic profiling of single DNA molecules spanning hundreds of thousands of base pairs. We used a CpG methyltransferase with a synthetic S-adenosyl-l-methionine cofactor analog to transfer an azide to cytosines instead of the natural methyl group. A fluorophore was then clicked onto the DNA, reporting on the amount and position of non-methylated CpGs. We found that labeling efficiency was increased up to 2-fold by the addition of a nucleosidase, presumably by degrading the inactive by-product of the cofactor after labeling, preventing its inhibitory effect. We used the method to determine the decline in global DNA methylation in a chronic lymphocytic leukemia patient and then performed whole-genome methylation mapping of the model plant Arabidopsis thaliana. Our genome maps show high concordance with published bisulfite sequencing methylation maps. Although mapping resolution is limited by optical detection to 500-1000 bp, the labeled DNA molecules produced by this approach are hundreds of thousands of base pairs long, allowing access to long repetitive and structurally variable genomic regions.

Association of computed tomography-based body composition with survival in metastatic renal cancer patient received immunotherapy: a multicenter, retrospective study.

OBJECTIVES: To investigate the association of computed tomography-assessed body composition with survival outcomes of metastatic renal cell carcinoma (mRCC) received immunotherapy. METHODS: In this multicenter, retrospective study, we reviewed 251 mRCC patients who received anti-PD1 from five centers. We analyzed the relationship between BMI, skeletal muscle area (SM), subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and subcutaneous adipose percentage (SAT%) with progression-free survival (PFS) and overall survival (OS). The spatial localization T cells was investigated by multiplex immunofluorescence. RESULTS: Among 224 evaluable patients, 23 (10.3%) patients were underweight, 118 (52.7%) had normal weight, 65 (29%) were overweight, and 18 patients (8%) were obese. The median age was 55 years and most patients were male (71%). No significant improvement in PFS (HR, 0.61; 95% CI, 0.27-1.42) or OS (HR, 1.09; 95% CI, 0.38-3.13) was observed for the obese patients. Besides, SM, VAT, and SAT were not associated with survival outcomes (all p > 0.05). Interestingly, SAT% independently predicted PFS (as continuous variable, HR: 0.02; 95% CI, 0.01-0.11) and OS (HR:0.05; 95% CI, 0.01-0.39), which remained significant in multivariate modeling (as continuous variable, adjusted HR for PFS, 0.01; 95% CI, 0.00-0.04; adjusted HR for OS, 0.08; 95% CI, 0.01-0.72). These associations were consistent in subgroup analysis of different gender, BMI, PD-L1 positive, and sarcopenia group. Tumor of high SAT% patients had a higher intratumoral PD1+ CD8+ T cell density and ratio. CONCLUSION: High SAT% predicts better outcomes in mRCC patients treated with anti-PD1 and T cell location may account for the better response. KEY POINTS: • CT-based subcutaneous adipose percentage independently predicted progression-free survival and overall survival. • Patients with a higher subcutaneous adipose percentage had a higher intratumoral PD1+ CD8+ T cell density and ratio.

Study on the Effect of Different Viscosity Reducers on Viscosity Reduction and Emulsification with Daqing Crude Oil.

The urgent problem to be solved in heavy oil exploitation is to reduce viscosity and improve fluidity. Emulsification and viscosity reduction technology has been paid more and more attention and its developments applied. This paper studied the viscosity reduction performance of three types of viscosity reducers and obtained good results. The viscosity reduction rate, interfacial tension, and emulsification performance of three types of viscosity reducers including anionic sulfonate, non-ionic (polyether and amine oxide), and amphoteric betaine were compared with Daqing crude oil. The results showed that the viscosity reduction rate of petroleum sulfonate and betaine was 75-85%. The viscosity reduction rate increased as viscosity reducer concentration increased. An increase in the oil-water ratio and polymer decreased viscosity reduction. When the concentration of erucamide oxide was 0.2%, the ultra-low interfacial tension was 4.41 × 10-3 mN/m. When the oil-water ratio was 1:1, the maximum water separation rates of five viscosity reducers were different. With an increase in the oil-water ratio, the emulsion changed from o/w emulsion to w/o emulsion, and the stability was better. Erucamide oxide and erucic betaine had good viscosity reduction and emulsification effects on Daqing crude oil. This work can enrich knowledge of the viscosity reduction of heavy oil systems with low relative viscosity and enrich the application of viscosity reducer varieties.

Accelerating the Design of High-Energy-Density Hydrocarbon Fuels by Learning from the Data.

In the ZINC20 database, with the aid of maximum substructure searches, common substructures were obtained from molecules with high-strain-energy and combustion heat values, and further provided domain knowledge on how to design high-energy-density hydrocarbon (HEDH) fuels. Notably, quadricyclane and syntin could be topologically assembled through these substructures, and the corresponding assembled schemes guided the design of 20 fuel molecules (ZD-1 to ZD-20). The fuel properties of the molecules were evaluated by using group-contribution methods and density functional theory (DFT) calculations, where ZD-6 stood out due to the high volumetric net heat of combustion, high specific impulse, low melting point, and acceptable flash point. Based on the neural network model for evaluating the synthetic complexity (SCScore), the estimated value of ZD-6 was close to that of syntin, indicating that the synthetic complexity of ZD-6 was comparable to that of syntin. This work not only provides ZD-6 as a potential HEDH fuel, but also illustrates the superiority of learning design strategies from the data in increasing the understanding of structure and performance relationships and accelerating the development of novel HEDH fuels.

How to Regulate the Migration Ability of Emulsions in Micro-Scale Pores: Droplet Size or Membrane Strength?

Micro visualization has become an important means of solving colloid and interface scientific problems in enhanced oil recovery. It can establish a relationship between a series of performance evaluations of an oil-water interface under macroscopic dimensions and the actual application effect in confined space, and more truly and reliably reflect the starting and migration behavior of crude oil or emulsion in rock pores. In this article, zwitterionic surfactant alkyl sulfobetaine (ASB) and anionic extended surfactant alkyl polyoxypropylene sulfate (A145) were employed as flooding surfactants. The macroscopic properties of the surfactant solutions, such as the oil-water interfacial tension (IFT), the interfacial dilational rheology and the viscosity of crude oil emulsions, have been measured. At the same time, we link these parameters with the oil displacement effect in several visual glass models and confirm the main factors affecting the migration ability of emulsions in micro-scale pores. The experimental results show that ASB reduces the IFT through mixed adsorption with crude oil fractions. The flat arrangement of the large hydrophilic group of ASB molecules enhances the interactions between the surfactant molecules on the oil-water interface. Compared with sulfate, betaine has higher interfacial membrane strength and emulsion viscosity. A145 has a strong ability to reduce the IFT against crude oil because of the larger size effect of the PO chains at the oil side of the interface. However, the membrane strength of A145 is moderate and the emulsion does not show a viscosity-increasing effect. During the displacement process, the deformation ability of the front emulsions or oil banks is the main controlling factor of the displacement efficiency, which is determined by the membrane strength and emulsion viscosity. The strong interfacial membrane strength and the high emulsion viscosity are not conducive to the migration of droplets in pore throats and may result in low displacement efficiency.

The Synergistic Effects between Sulfobetaine and Hydrophobically Modified Polyacrylamide on Properties Related to Enhanced Oil Recovery.

In order to explore the mechanism responsible for the interactions in the surfactant-polymer composite flooding and broaden the application range of the binary system in heterogeneous oil reservoirs, in this paper, the influences of different surfactants on the viscosity of two polymers with similar molecular weights, partially hydrolyzed polyacrylamide (HPAM) and hydrophobically modified polyacrylamide (HMPAM), were studied at different reservoir environments. In addition, the relationship between the surfactant-polymer synergistic effects and oil displacement efficiency was also investigated. The experimental results show that for HPAM, surfactants mainly act as an electrolyte to reduce its viscosity. For HMPAM, SDBS and TX-100 will form aggregates with the hydrophobic blocks of polymer molecules, reducing the bulk viscosity. However, zwitterionic surfactant aralkyl substituted alkyl sulfobetaine BSB molecules can build "bridges" between different polymer molecules through hydrogen bonding and electrostatic interaction. After forming aggregates with HMPAM molecules, the viscosity will increase. The presence of two polymers all weakened the surfactant oil-water interfacial membrane strength to a certain extent, but had little effect on the interfacial tension. The synergistic effect of the "bridge" between HMPAM and BSB under macroscopic conditions also occurs in the microscopic pores of the core, which has a beneficial effect on improving oil recovery.

Dynamic Interfacial Tensions of Surfactant and Polymer Solutions Related to High-Temperature and High-Salinity Reservoir.

Betaine is a new surfactant with good application prospects in high-temperature and high-salinity reservoirs. The interfacial properties of two kinds of betaine mixtures with a good synergistic effect were evaluated in this paper. On this basis, the effects of temperature-resistant, salt-resistant polymers with different contents of 2-acrylamide-2-methylpropanesulfonic acid (AMPS) on dynamic interfacial tensions (IFTs) against n-alkanes and crude oil were studied. The experimental results show that the IFTs between betaine ASB and n-alkanes can be reduced to ultra-low values by compounding with anionic surfactant petroleum sulfonate (PS) and extended anionic surfactant alkoxyethylene carboxylate (AEC), respectively. ASB@AEC is very oil-soluble with nmin value ≥14, and ASB@PS is relatively water-soluble with nmin value of 10. The water solubility of both ASB@PS and ASB@AEC is enhanced by the addition of water-soluble polymers. The HLB of the ASB@AEC solution becomes better against crude oil after the addition of polymers, and the IFT decreases to an ultra-low value as a result. On the contrary, the antagonistic effect in reducing the IFT can be observed for ASB@PS in the same case. In a word, polymers affect the IFTs of surfactant solutions by regulating the HLB.

Joint Client Selection and CPU Frequency Control in Wireless Federated Learning Networks with Power Constraints.

Federated learning (FL) represents a distributed machine learning approach that eliminates the necessity of transmitting privacy-sensitive local training samples. However, within wireless FL networks, resource heterogeneity introduces straggler clients, thereby decelerating the learning process. Additionally, the learning process is further slowed due to the non-independent and identically distributed (non-IID) nature of local training samples. Coupled with resource constraints during the learning process, there arises an imperative need for optimizing client selection and resource allocation strategies to mitigate these challenges. While numerous studies have made strides in this regard, few have considered the joint optimization of client selection and computational power (i.e., CPU frequency) for both clients and the edge server during each global iteration. In this paper, we initially define a cost function encompassing learning latency and non-IID characteristics. Subsequently, we pose a joint client selection and CPU frequency control problem that minimizes the time-averaged cost function subject to long-term power constraints. By utilizing Lyapunov optimization theory, the long-term optimization problem is transformed into a sequence of short-term problems. Finally, an algorithm is proposed to determine the optimal client selection decision and corresponding optimal CPU frequency for both the selected clients and the server. Theoretical analysis provides performance guarantees and our simulation results substantiate that our proposed algorithm outperforms comparative algorithms in terms of test accuracy while maintaining low power consumption.

Chiral Supramolecular Microporous Thio-Oxomolybdenum(V) Tartrates for the Selective Adsorptions of Gases.

Two pairs of enantiomerically pure hexanuclear and tetranuclear microporous molybdenum(V) d/l-tartrates, (H2trz)3[Mo6O6(µ2-O)3(µ2-S)3(d/l-Htart)3(Htrz)6]·8H2O (abbreviated as d-1 and l-1; H4tart = tartaric acid, Htrz = 1,2,4-triazole) and (H22-mim)8[Mo4O4(µ2-S)4(d/l-tart)2]2·4H2O (d-2/l-2; H2-mim = 2-methylimidazole), have been isolated in reduced media and well characterized. These enantiomers are observed to finish self-assemblies with single chiral configurations. Structural analyses indicate that tartrates adopt different coordination modes with α-carboxy and/or α-alkoxy groups in 1 and 2, which are further completed with nitrogen-containing ligands. There are two types of micropores that exist in 1 and 2, separately, which are all formed by the isolated molecules themselves. The significant roles of hydrogen bonding among lattice molecules, tartrates, and multi-azoles are suggested, where 1 and 2 exhibited interesting supramolecular networks only through intramolecular self-sorts. Adsorption tests show that 1 has good affinities toward CO2 and O2, while 2 is the most potential O2 adsorbent compared with other common gases CO2, H2, CH4, and N2 under different pressures. In addition, IR, UV-vis, CD (circular dichroism), and solid-state 13C NMR spectroscopies have demonstrated the special chemical properties of these novel molybdenum d/l-tartrates.

Atomically Dispersed Janus Nickel Sites on Red Phosphorus for Photocatalytic Overall Water Splitting.

Single-atom nickel catalysts hold great promise for photocatalytic water splitting due to their plentiful active sites and cost-effectiveness. Herein, we adopt a reactive-group guided strategy to prepare atomically dispersed nickel catalysts on red phosphorus. The hydrothermal treatment of red phosphorus leads to the formation of P-H and P-OH groups, which behave as the reactive functionalities to generate the dual structure of single-atom P-Ni and P-O-Ni catalytic sites. The produced single-atom sites provide two different functions: P-Ni for water reduction and P-O-Ni for water oxidation. Benefitting from this specific Janus structure, Ni-red phosphorus shows an elevated hydrogen evolution rate compared to Ni nanoparticle-modified red phosphorus under visible-light irradiation. The hydrogen evolution rate was additionally enhanced with increased reaction temperature, reaching 91.51 µmol h-1 at 70 °C, corresponding to an apparent quantum efficiency of 8.9 % at 420 nm excitation wavelength.

Intrinsic Molybdenum-Based POMOFs with Impressive Gas Adsorptions and Photochromism.

Novel molybdenum(VI/V) POM-based self-constructed frameworks [MoVI 12 O24 (µ2 -O)12 (trz)6 (H2 O)6 ] ⋅ 6Hma ⋅ 18H2 O (1, Htrz=1H-1,2,3-triazole, ma=methylamine), [MoVI 7 O14 (µ2 -O)8 (trz)5 (H2 O)] ⋅ 7Hma ⋅ 5H2 O (2), Na3 [MoV 6 O6 (µ2 -O)9 (Htrz)3 (trz)3 ] ⋅ 7.5H2 O (3) and [MoV 8 O8 (µ2 -O)12 (Htrz)8 ] ⋅ 30H2 O (4) have been covalently decorated with tri-coordinated deprotonated/protonated 1,2,3-triazoles. Channels with an inner diameter of 7.5 Šwere found in 1, whereas a tunnel composed of stacking molecules with an inner diameter of 4.1 Šalong the b-axis exists in 2; it is occupied by free disordered methylamines, showing selective adsorption of O2 and CO2 at 25 °C. Obvious downfield shifts were observed by 13 C NMR spectroscopies for methylamines inside the confined channels in 1 and 2. There are diversified pores in 3 and 4, which are formed by the molecules themselves and intermolecular accumulations. Adsorption tests indicate that 3 and 4 are fine adsorption materials for CH4 and CO2 under low pressure that rely on the environments built by the POMs. Correspondingly, 1 and 2 display reversible photoresponsive thermochromism that is subtlety influenced by the channels. The polyoxometalate organic frameworks (POMOFs) with multiple functional adsorptions are easy to assemble. Their photo-/thermoresponse properties offer a new pathway for the self-constructions of one-off hybrid materials that possess the good properties of both POMs and MOFs.

Adsorption and wettability of extended anionic surfactants with different PO numbers on a polymethylmethacrylate surface.

To investigate the effect of the number of propylene oxide (PO) units on the wettability of surfactants, the wettability of isomeric dodecyl(polyoxyisopropyl)7 sulfate (S-C12PO7S) and isomeric dodecyl(polyoxyisopropyl)13 sulfate (S-C12PO13S) on the surface of polymethylmethacrylate (PMMA) was investigated. The adsorption behavior on the PMMA surface was analyzed by measuring the surface tension and the contact angle. It is found that the PO group may form hydrogen bonds with the PMMA surface, thus facilitating the hydrophobic tails pointing to the aqueous phase. Moreover, the steric effect of the PO group benefits the formation of semi-micelles above the critical micelle concentration (CMC). Surfactant molecules adsorb on the PMMA surface by polar adsorption below the CMC with hydrophobic tails towards the water. Therefore, the PMMA surface is modified to be more hydrophobic. However, the sodium dodecyl sulfate (SDS) surfactant with no PO unit does not have hydrophobic modification ability on the PMMA surface. Below the CMC, the adsorption amounts of the S-C12PO7S and S-C12PO13S surfactants at the solid-liquid interface were approximately 1/3 of those at the air-liquid interface. Interestingly, the adsorption behavior changes when the concentration of the surfactants is around the CMC. The hydrophilic heads of the surfactant molecules will point to water, and the surfactant molecules will form semi-micellar aggregates on the PMMA surface. Therefore, the PMMA surface is modified to be hydrophilic above the CMC. What's more, both the hydrophilic modification ability and hydrophobic modification ability of the S-C12PO13S surfactant are stronger than those of the S-C12PO7S surfactant. This means that the number of PO units will affect the wettability ability of the surfactants. Therefore, the S-C12PO13S surfactant possesses smaller contact angles than the S-C12PO7S surfactant at high concentrations.

Long Noncoding RNA TTC39A-AS1 Promotes Breast Cancer Tumorigenicity by Sponging MicroRNA-483-3p and Thereby Upregulating MTA2.

INTRODUCTION: In recent years, the regulatory activities of long noncoding RNAs have received increasing attention as an important research focus. This study aimed to characterize the expression and detailed roles of TTC39A antisense RNA 1 (TTC39A-AS1) in breast cancer (BC), in addition to concentrating on its downstream mechanisms. METHODS: Quantitative RT-PCR was performed to determine the expression levels of TTC39A-AS1, microRNA-483-3p (miR-483-3p), and metastasis-associated gene 2 (MTA2). Further, the detailed functions of TTC39A-AS1 in BC cells were confirmed using the Cell Counting Kit 8 assay, flow cytometric analysis, and Transwell cell migration and invasion assays. The targeting relationship between TTC39A-AS1, miR-483-3p, and MTA2 in BC was predicted via bioinformatics analysis and further confirmed by performing the luciferase reporter assay and RNA immunoprecipitation. RESULTS: TTC39A-AS1 was present in high levels in BC; this result was confirmed in our sample cohort and The Cancer Genome Atlas database. Patients with BC with a high level of TTC39A-AS1 had a shorter overall survival than those with a low level of TTC39A-AS1. Functionally, the absence of TTC39A-AS1 accelerated cell apo-ptosis but retained cell proliferation, migration, and invasion. Mechanistically, TTC39A-AS1 functioned as a competing endogenous RNA in BC by sponging miR-483-3p and thereby indirectly increasing MTA2 expression. Finally, rescue experiments revealed that the tumor-inhibiting actions of TTC39A-AS1 knockdown on the malignant characteristics of BC cells could be reversed by inhibiting miR-483-3p or upregulating MTA2. CONCLUSION: The newly identified TTC39A-AS1/miR-483-3p/MTA2 pathway was revealed to be a critical regulator in the tumorigenicity of BC, possibly offering a novel therapeutic direction for the anticancer treatment of BC.

Clinical and Pathological Features of Prostatic Stromal Tumor of Uncertain Malignant Potential: A Retrospective Study of 23 Chinese Cases.

INTRODUCTION: Prostatic stromal tumor of uncertain malignant potential (STUMP) is a rare disease that may coexist with prostate stromal sarcoma (PSS). We aimed to analyze the histological and clinical features of STUMP. METHODS: Twenty-three patients diagnosed with STUMP from 2008 to 2019 were included. Clinicopathological and follow-up information was collected. In the subgroup analysis, we divided the patients into a pure STUMP group (N = 18) and a mixed STUMP (STUMP coexisting with PSS) group (N = 5). Student's t test was used to compare the 2 groups. RESULTS: Patients had a mean age of 55.5 ± 19.4 years and an average follow-up time of 42.3 months. The mean prostate volume was 109.2 ± 73.5 cm3, and the mean prostate-specific antigen was 8.03 ± 10.5 ng/mL. In the subgroup analysis, 16.7% (2/12) of pure STUMP patients had disease progression, while 100% (3/3) of mixed STUMP patients suffered from recurrence. Compared with the pure STUMP group, the mixed STUMP group was younger (37.2 vs. 60.6 years, p = 0.013) and had lower expression of estrogen receptor and progesterone receptor (p = 0.004 and p < 0.001, respectively). CONCLUSION: STUMP is a rare disease with a relatively good prognosis. However, there is still a possibility of disease progression or coexistence with stromal sarcoma. Timely diagnosis and regular monitoring may be helpful in improving treatment outcomes.

Adsorption behaviors of branched cationic gemini surfactants and wettability in quartz-solution-air systems.

The adsorption and wetting on quartz surfaces by aqueous solutions of xylyl-substituted biquaternary ammonium salt gemini surfactants with different spacer groups (C3 and C6), have been investigated. The interfacial properties of surfactant solutions such as contact angle, adhesional tension (γLV cos θ), quartz-water interfacial tension (γSL) as well as adhesion work (WA) have been estimated. The obtained results show that C3 and C6 have similar adsorption behavior on quartz surfaces. Before critical micelle concentration (cmc) is reached, the contact angles of gemini surfactants slowly increase with the increasing concentration, and the adsorption amount at the water-air interface is almost the same as those at a quartz-water interface. After reaching cmc, the gemini surfactant Cn molecules form a more compact adsorption film through bending the flexible spacer chain, instead of forming a bi-layer. As a result, a further increase in quartz-liquid interfacial tension (γSL) and a consequent increase in contact angle have been observed after cmc. Gemini C6 shows a stronger ability towards hydrophobic modification at a quartz surface than C3, demonstrating the contribution of the longer methylene spacer to the hydrophobic modification of the quartz surface.

Isolated Mixed-Valence Iron Vanadium Malate and Its Metal Hydrates (M = Fe2+, Cu2+, Zn2+) with Reversible and Irreversible Adsorptions for Oxygen.

Isolated octanuclear iron-vanadium malate (NH4)3(CH3NH3)3[FeIII2VIV2VV4O11(mal)6]·7.5H2O (1; H3mal = malic acid) and its family of metal hydrates M'3n[MII(H2O)2]1.5n[FeIII2VIV2VV4O11(mal)6]n·xnH2O (2 or 2-Fe, M' = NH4+, M = Fe, x = 7.5; 3 or 3-Cu, M' = K+, M = Cu, x = 10; 4 or 4-Zn, M' = K+, M = Zn, x = 6.5) have been obtained by self-assembly in water. The cluster anion [Fe2V6O11(mal)6]6- (1a) shows an interesting iron bicapped-triangular-prismatic structure, which is bridged by M2+ hydrates (M = Fe, Cu, Zn) to construct isostructural metal organic frameworks (MOFs) 2-4. The mixed-valence vanadium systems in 1-4 were determined by theoretical bond valence calculations (BVS) and charge balance. The magnetic susceptibilities are further elucidated as high spin for Fe3+ in 1a and bridging Fe2+ in 2-Fe, respectively. A strong ferromagnetic interaction was also observed for 2-Fe at 3 K. 2-Fe, 3-Cu, and 4-Zn have similar hydrophilic channels with diameters of 6.8, 6.5, and 6.6 Å, respectively, which show obvious affinity for O2 in comparison with no adsorption of N2, H2, CO2, and CH4 at room temperature under different pressures. Moreover, 2-Fe and 4-Zn exhibit irreversible O2 absorptions, which may be attributed to charge transfer between O2 and open metal sites (OMSs) formed during vacuum heating pretreatment. UV-vis and EPR spectra show a change in electronic structure of 2-Fe after O2 adsorption. The reversible adsorption observed in 3-Cu suggests a weak interaction between O2 and Cu2+ due to the Jahn-Teller effect. The properties of gas adsorption provide an insight into the performances of small molecules in the channels constructed by synthetic octanuclear model compounds, which are related to the interactions between the gas substrate and the heterometal cluster in biology.

Gas Adsorption of Mixed-Valence Trinuclear Oxothiomolybdenum Glycolates.

Trinuclear oxothiomolybdenum(IV) glycolates (H2glyc, glycolic acid) with 2-methylimidazole (2-mim), 4-methylimidazole (4-mim), and sulfite, Na2[MoIV3(µ3-S)(µ2-O)3(glyc)3(2-mim)3]·1.5H2O (1), (4-Hmim)6[MoIV3(µ3-S)(µ2-O)3(glyc)3(4-mim)3]2[MoVIO2(glyc)2] (2), and Na3(4-Hmim)[MoIV3(µ3-S)(µ2-O)3(SO3)(glyc)3(4-mim)]·8H2O (3), have been isolated in reduced media, where 4-methylimidazole trinuclear oxothiomolybdenum(IV) glycolates in 2 coprecipitate with dioxomolybdenum(VI) glycolate, exhibiting unusual mixed valences of 4+ and 6+. Large downfield shifts of glycolates have been observed in solid-state and solution 13C (1H) NMR spectra with coordination to Mo, indicating obvious dissociation of soluble 1 and 3 in solution. Investigations of the coordination modes and conversions among the three complexes give insight into the reactivities of trinuclear oxothiomolybdenum(IV) complexes. Channels with 3.1 × 7.0 Å2 diameters exist in 2, showing reversible O2 absorption of 65.03 mg at 29.9 bar compared with little or no adsorption of N2, H2, CO2, and CH4 at room temperature, respectively. Moreover, trinuclear 2- or 4-methylimidazole oxothiomolybdenum(IV) glycolates 1 and 3 show only a few adsorptions for O2 under the same conditions.

Improved description of hematite surfaces by the SCAN functional.

Controversies on the surface termination of α-Fe2O3 (0001) focus on its surface stoichiometry dependence on the oxygen chemical potential. Density functional theory (DFT) calculations applying the commonly accepted Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional to a strongly correlated system predict the best matching surface termination, but would produce a delocalization error, resulting in an inappropriate bandgap, and thus are not applicable for comprehensive hematite system studies. Besides, the widely applied PBE+U scheme cannot provide evidence for existence of some of the successfully synthesized stoichiometric α-Fe2O3 (0001) surfaces. Hence, a better scheme is needed for hematite DFT studies. This work investigates whether the strongly constrained and appropriately normed (SCAN) approximation reported by Perdew et al. could provide an improved result for the as-mentioned problem, and whether SCAN can be applied to hematite systems. By comparing the results calculated with the PBE, SCAN, PBE+U, and SCAN+U schemes, we find that SCAN and SCAN+U improves the description of the electronic structure of different stoichiometric α-Fe2O3 (0001) surfaces with respect to the PBE results, and that they give a consistent prediction of the surface terminations. Besides, the bulk lattice constants and the bulk density of states are also improved with the SCAN functional. This study provides a general characterization of the α-Fe2O3 (0001) surfaces and rationalizes how the SCAN approximation improves the results of hematite surface calculations.

Quantum dynamics origin of high photocatalytic activity of mixed-phase anatase/rutile TiO2.

Mixed anatase/rutile TiO2 exhibits high photocatalytic activity; however, the mechanism underlying the high performance of the mixed phases is not fully understood. We have performed time-domain ab initio calculations to study the exited state dynamics in mixed phase TiO2 and to investigate the impact of an oxygen vacancy on the dynamics. The anatase(100)/rutile(001) heterostructures with and without an oxygen vacancy used in this work exhibit type II band alignment with the conduction band of rutile residing above that of anatase. The oxygen vacancy introduces a hole trap state inside the bandgap. Owing to a strong coupling between the donor and acceptor states, the electron and hole transfers across the anatase/rutile interface occur on an ultrafast 100 fs timescale in both systems. The decoupling of electron and hole favors a long-lived charge separated state. The electron-hole recombination across the pristine anatase/rutile interface takes 6.6 ns and is significantly slower than that in the pure anatase and rutile phases, showing good agreement with experiments. The electron transfer dynamics is independent of the oxygen vacancy, which has some influence on the hole transfer and a strong effect on carrier recombination. By creating a hole trap state, the vacancy accelerates carrier losses by over an order of magnitude. The fast charge separation and the long lifetime of the charge separated state rationalize the enhanced photocatalytic performance of mixed phase TiO2 compared to the pure phases.