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26 well selected oxidized P-clusters (P2+) from the crystallographic data deposited in the Protein Data Bank have been analysed statistically by the bond-valence sum method with weighting schemes for MoFe proteins at different resolutions. Interestingly, the oxidation states of P2+ clusters correspond to Fe2 3+Fe6 2+ with high electron delocalization, showing the same oxidation states as the resting states of P-clusters (PN) in nitrogenases. The previously uncertain reduction of P2+ to PN clusters by two electrons was assigned as a double protonation of P2+, in which decoordination of the serine residue and the peptide chain of cysteine take place, in MoFe proteins. This is further supported by the obviously shorter α-alkoxy C—O bond (average of 1.398 Å) in P2+ clusters and longer α-hydroxy C—O bond (average of 1.422 Å) in PN clusters, while no change is observed in the electronic structures of Fe8S7 Fe atoms in P-clusters. Spatially, the calculations show that Fe3 and Fe6, the most oxidized and most reduced Fe atoms, have the shortest distances of 9.329 Å from the homocitrate in the FeMo cofactor and 14.947 Å from the [Fe4S4] cluster, respectively, and may well function as important electron-transport sites.

Regular tetra-, hexa- and octanuclear microporous polyoxovanadates(iii) 1–4 are constructed successively. An interesting isolated intrinsic POMOF 4 with the functionalization of microchannels exhibits a notable affinity toward CO2 adsorption.

Iron valences of 129 P-clusters from FeMo/V proteins were analyzed using a bond valence method, supposing the existence of Fe3+ in a generally considered all-ferrous PN cluster in solution with excess reducing agent.

By comparisons of N2 and isoelectronic substrate CO bound FeMo-cofactors (FeMo-cos) in nitrogenases, we have used a classical bond valence method to calculate the oxidation states of the iron and molybdenum atoms in FeMo-cos.

Two pairs of enantiomerically pure hexanuclear and tetranuclear microporous molybdenum(V) d/l-tartrates, (H

Hydrogenation of methyl p-hydroxyphenylacetate has been used for the synthesis of p-hydroxyphenyl ethanol. The reaction was catalyzed by CuiZrj-x%(mass fraction) carbon nanotubes(CNTs) catalysts. Incorporation of a minor amount of CNTs into CuiZrj oxide can visibly increase the catalytic activity for the synthesis of p-hydroxyphenyl ethanol. The yield of p-hydroxyphenyl ethanol reaches 94.2% over a co-precipitated catalyst of Cu3Zr1 oxide with 11.0%CNTs. Its catalytic activity shows no obvious decrease after three cycles. This is much better than the CNT-free co-precipitated catalyst with a good yield of 81.1%, Cu3Zr1-0%CNTs.

Syntheses of POMOFs are related to pH values in solutions. Gas adsorptions indicate that 1 is a potential CO2 adsorbent. 13C NMR and UV-vis spectra can supply further evidences of the isolated Mo8 and Mo2 species.

Three lanthanum aminopolycarboxylates [La(Hida)2(H2O)2]n·nCl·4nH2O (1), K2n[La(nta)2]n·nH2O (2) and (H2en)n[La(edta)(H2O)]2n·10nH2O (3) (H2ida = iminodiacetic acid; H3nta = nitrilotriacetic acid; H4edta = ethylenediaminetetraacetic acid; en = ethylenediamine, NH2CH2CH2NH2) were isolated by gel self-assembly and were fully characterized. Structural analyses reveal that 1–3 have infinite 2D and 3D structures with different coordination modes. Topological analyses of 1–3 were also performed. Solid state 13C NMR spectra show that the coordinated β-CO2 groups give obvious downfield shifts compared with free β-CO2 groups. Interestingly, 3 possesses 5.8 A diameter tunnels inside the crystals, which can selectively adsorb very small amounts of O2 at 5.49 mg g−1 and 29.9 bar, while no adsorption of H2, N2, CH4 and CO2 is observed. Compared with lanthanum 1,3-propylenediaminetetraacetate {La(H2O)4[La(1,3-pdta)(H2O)]3}n·11.25nH2O (4) with 10.0 A diameter tunnels, the latter can adsorb CO2, O2 and N2 at 55.33, 18.01 and 4.41 mg g−1 and 29.9 bar, respectively. This shows that smaller diameter tunnels have better selectivity towards the adsorption of specific gases. When the diameter of the tunnels increases, the adsorption amounts of numerous gases increase significantly with a decrease in selectivity.

The anion zinc-based metal–organic framework [HDMA]2n[Zn2n(DMA)2n(1,4-BDC)3n]·2nDMF·6nH2O (1, DMF = N,N-dimethylformamide, 1,4-H2BDC = 1,4-benzenedicarboxylic acid, DMA = dimethylamine) with open channels has been used as a luminescent sensor for Cd2+ detection, and was obtained by solvothermal synthesis and fully characterized. It shows excellent fluorescence stability in aqueous solution, which was further enhanced with a remarkable fluorescence shift upon introduction of Cd2+, while negligible effects occurred for Fe2+, Zn2+, Fe3+, Cu2+, Co2+, Ni2+, Mn2+ and Pb2+, respectively. The detection limit is 9.9 μM with a linear range between 50 and 600 μM for Cd2+. Furthermore, it can be used to detect Cd2+ in tap water and rice samples directly. Solid state 13C NMR spectra give direct evidence for the ion exchange between protonated dimethylamine and Cd2+ hydrates, which results in the increase of fluorescence and blue shift of the wavelength. The coordination of Cd2+ with the carboxyl groups of 1 in the interface of nano-channels can be also observed using IR spectra, where a structural model has been suggested in the confined channels. This may provide a new construction method for anion fluorescent MOF materials, where a confined sample has obvious influence on the detection of Cd2+. The maximum adsorption capacities are 10.36, 54.53, 103.06 and 8.78 mg g−1 for CH4, CO2, O2 and N2 at 30 bar respectively.

Dimeric mixed-ligand oxidovanadium complexes [V2O2(1,3-pdta)(bpy)2]·9H2O (1) and [V2O2(1,3-pdta)(phen)2]·6H2O (2) feature a symmetric binuclear structure bridged by 1,3-pdta, which is different fro...

Recurrent renal cell carcinoma(reRCC) is associated with poor prognosis and the underlying mechanism is not yet clear. A comprehensive understanding of tumor microenvironment (TME) of reRCC may aid in designing effective anticancer therapies, including immunotherapies. Single-cell transcriptomics holds great promise for investigating the TME, however, this technique has not been used in reRCC. Here, we aimed to explore the difference in the TME and gene expression pattern between primary RCC (pRCC) and reRCC at single-cell level.We performed single-cell RNA sequencing analyses of 32,073 cells from 2 pRCC, 2 reRCC, and 3 adjacent normal kidney samples. 41 pairs of pRCC and reRCC samples were collected as a validation cohort to assess differences observed in single-cell sequencing. The prognostic significance of related cells and markers were studied in 47 RCC patients underwent immunotherapy. The function of related cells and markers were validated via in vitro and in vivo experiments.reRCC had reduced CD8We delineated the heterogeneity of reRCC and highlighted an innovative mechanism that CAFs acted as a suppressor of CD8

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 ...

The bond-valence method has been used for valence calculations of FeMo/V cofactors in FeMo/V proteins using 51 crystallographic data sets of FeMo/V proteins from the Protein Data Bank. The calculations show molybdenum(III) to be present in MoFe7S9C(Cys)(HHis)[R-(H)homocit] (where H4homocit is homocitric acid, HCys is cysteine and HHis is histidine) in FeMo cofactors, while vanadium(III) with a more reduced iron complement is obtained for FeV cofactors. Using an error analysis of the calculated valences, it was found that in FeMo cofactors Fe1, Fe6 and Fe7 can be unambiguously assigned as iron(III), while Fe2, Fe3, Fe4 and Fe5 show different degrees of mixed valences for the individual Fe atoms. For the FeV cofactors in PDB entry 5n6y, Fe4, Fe5 and Fe6 correspond to iron(II), iron(II) and iron(III), respectively, while Fe1, Fe2, Fe3 and Fe7 exhibit strongly mixed valences. Special situations such as CO-bound and selenium-substituted FeMo cofactors and O(N)H-bridged FeV cofactors are also discussed and suggest rearrangement of the electron configuration on the substitution of the bridging S atoms.

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-Hmi...

To expound the mechanisms responsible for the effect of electrolyte on the interfacial tensions (IFTs) of mixed solutions containing zwitterionic surfactant alkyl sulfobetaine (ASB) and anionic sur...

Glutamine gets transformed to 2-hydroxy-5-oxoproline with NH4VO3 in a neutral solution as a product of 2,2'-bipyridine oxidovanadium(v) 2-hydroxy-5-oxoproline [VV2O3(hop)2(bpy)2]·7H2O [1, H2hop = 2-hydroxy-5-oxoproline] with yields of 65.6%. Similarly, histidine and arginine are converted into the corresponding α-hydroxycarboxylates as 2,2'-bipyridine oxidovanadium(iv) 3-(1H-imidazolyl-5-yl)-2-hydroxyacrylate [VIV2O2(imha)2(bpy)2]·bpy [2, H2imha = 3-(1H-imidazolyl-5-yl)-2-hydroxyacrylic acid] and guanidinium oxidovanadium(v) 1-(aminoiminomethyl)-2-hydroxyproline (CN3H6)[VVO2(Haimhp)2]·2H2O [3, H2aimhp = 1-(aminoiminomethyl)-2-hydroxyproline] with V2O5 in low yields respectively, where an aggregate of oxidovanadium(v) arginine (H2arg)n(VVO3)n·½nH2O (4, Harg = arginine) has been isolated preferentially in an initial experiment for 3. α-Hydroxycarboxylates chelate bidentately with vanadium viaα-alkoxy and α-carboxy groups in 1-3, as observed from structural analyses. Their racemizations have been observed after the conversions. There is no coordination in 4 based on solid-state 13C NMR spectra, and only strong hydrogen bonds exist in the anion chains (VVO3)- and protonated arginines. 1 and 4 were fully characterized by elemental analysis, UV-vis, IR and solid-state 13C NMR spectroscopies, TG and X-ray structural analyses, and theoretical bond valence calculations (BVS). The conversions of glutamine, histidine and arginine occur spontaneously in a solution under ambient conditions.

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.

Selective liquid and gas adsorptions are important for environmental control and industrial processes. Here, unique porous lanthanide–organic frameworks of [Ln2(1,3-pdta)2(H2O)2]n2n– {Ln = La (1), ...

Glycolato peroxotitanates [Ti2(O2)2(glyc)2(H2O)4]·2H2O (1) and (NH4)6[Ti4(O2)4O2(glyc)4(Hglyc)2]·7H2O (2) (H2glyc = glycolic acid) have been isolated from the reactions of titanium tetra-n-butyl oxide with glycolic acid and hydrogen peroxide. Transformations of glycolato peroxotitanates depend on pH values of the solutions, that is pH = 1.0 for 1 and pH = 5.0 for 2 respectively. Decomposition of 1 results in the formation of the pure anatase-type TiO2 at 500 °C, while 2 results in the formation of the pure rutile-type TiO2 at 700 °C. The titanium atoms in 1 and 2 exist in pentagonal bipyramidal coordination environment. 1 is a dinuclear neutral complex containing two Ti(O2) (H2O)2 cores, which are linked by two deprotonated glycolate ligands. 2 comprises a tetranuclear titanium anion structure, which consists of two Ti2(O2)2 cores inter-linked through two bridged oxygen atoms. The XRD patterns and Raman spectra of TiO2 annealed from 1 and 2 at different temperature were explored.

Protonation of FeMo-cofactor is important for the process of substrate hydrogenation. Its structure has been clarified as Δ-Mo*Fe(7)S(9)C(R-homocit*)(cys)(Hhis) for the efforts of nearly 30 years, while it remains controversial whether FeMo-cofactor is protonated or deprotonated with chelated ≡C–O(H) homocitrate. We have used protonated molybdenum(V) lactates 1 and its enantiomer as model compounds for R-homocitrate in FeMo-cofactor of nitrogenase. Vibrational circular dichroism (VCD) spectrum of 1 at 1051 cm(−1) is attributed to ≡C–O(H) vibration, and molybdenum(VI) R-lactate at 1086 cm(−1) is assigned as ≡C–O(α-alkoxy) vibration. These vibrations set up labels for the protonation state of coordinated α-hydroxycarboxylates. The characteristic VCD band of NMF-extracted FeMo-cofactor is assigned to ν(C–O(H)), which is based on the comparison of molybdenum(VI) R-homocitrate. Density Functional Theory calculations are in consistent with these assignments. To the best of our knowledge, this is the first time that protonated R-homocitrate in FeMo-cofactor is confirmed by VCD spectra.

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.

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 A were found in 1, whereas a tunnel composed of stacking molecules with an inner diameter of 4.1 A along 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.

Coordination polymers (CPs) of mixed-ligand lanthanide complexes [Ln2(1,3-pdta)(TPA)(H2O)2]n·nH2O [Ln = La, 1; Ce, 2; Pr, 3; Nd, 4] (1,3-H4pdta = 1,3-propanediaminetetraacetic acid; H2TPA = terephthalic acid) were hydrothermally synthesized with flexible 1,3-pdta and rigid TPA ligands. Moreover, lanthanide propanediaminetetraacetates [Ln(1,3-Hpdta)(H2O)]2n·nH2TPA·xH2O [Ln = Sm, 5; Gd, 6] with multi-layered structures were also obtained. In 1–4, both 1,3-pdta and TPA coordinate with lanthanide ions through carboxyl oxygen and nitrogen atoms. In 5 and 6, only 1,3-Hpdta coordinates with the central lanthanide ion, where one nitrogen atom in 1,3-Hpdta is protonated, and TPAs are crystallized as H2TPA with the central multi-layered structures of [Ln(1,3-Hpdta)(H2O)]2n through very strong hydrogen bonds [2.504(4) Å]. Solid-state 13C NMR analysis of 1 revealed the coordination of carboxyl groups. However, the methylene groups of 1,3-pdta showed an obvious upfield shift, which can be attributed to the effects of the phenyl ring in TPA ligand. The successful synthesis of these mixed-ligand lanthanides provides a rational design of such lanthanide CPs with flexible and rigid ligands.

A series of dimeric oxomolybdenum(V) 2,2′-bipyridine or 1,10-phenanthroline α-hydroxycarboxylates trans-[(MoO)2O(glyc)2(bpy)2]·3H2O (1), trans-[(MoO)2O(lact)2(bpy)2]·3H2O (2), trans-[(MoO)2O(Hmal)2(bpy)2] (3), trans-[(MoO)2O(lact)2(phen)2]·4H2O (4) and trans-[(MoO)2O(Hmal)2(phen)2]·4H2O (5) have been synthesized in acidic media for comparisons, where glycolate, lactate and malate in 1–5 chelate to molybdenum(V) with bidentate α-alkoxy and α-carboxy groups respectively. Unlike the molybdenum(IV) lactate in low valence [1] , no protonation was observed for α-alkoxy groups even under acidic condition. The two molybdenum atoms in 1 and 3 are paramagnetic independently as examples by EPR spectroscopies. Solid state 13C NMR spectra of 1 and 3 show large downfield shifts for the coordinated glycolate and malate (δα-alkoxy 75.4, 82.8 ppm, Δδ 13.4 ppm). Moreover, a monomeric mixed ligand oxomolybdenum(VI) complex MoO2(glyc)(bpy) (6) was isolated.

Vanadyl proline [VO(Hpro)(SO4)(H2O)3] (1, Hpro = proline), lysine trans-[VO(H2lys)2(H2O)3]Cl4·H2O (2, Hlys = lysine) and histidine [VO(H2his)(2,2′-bipy)(H2O)2]Cl3·H2O (3, Hhis = histidine) have been obtained in acidic conditions. Proline, lysine and histidine in 1–3 feature monodentate coordination with vanadium(IV) through carboxy groups respectively. The complexes are well characterized by elemental analysis, UV–Vis, IR, EPR, TG, X-ray structural analyses and bond valence calculations (BVS). The interactions between vanadium and amino acids are compared between 1–3 and other similar transition metal amino acids. Solution NMR spectra show the coordination of amino acids in solution. Moreover, 1 and 2 show good catalytic activities for the degradations of methyl orange (MO) with H2O2.

Mixed ligand oxidovanadium(IV) complexes VO(ox)(im)3·H2O (1), VO(ox)(4-mim)3 (2), K2[VO(ox)2(2-mim)]·2H2O (3) and [V2O2(edta)(phen)2]·11H2O (4) (H2ox = oxalic acid, H4edta = ethylenediaminetetraacetic acid, im = imidazole, 2-mim = 2-methylimidazole, 4-mim = 4-methylimidazole, and phen = 1,10-phenanthroline) have been obtained at room temperature and under hydrothermal condition respectively. 1–3 feature bidentate oxalate with two carboxy oxygen atoms, and the dimeric complex 4 contains hexadentate edta as bridging ligand. 1–4 have been fully characterized by elemental, thermogravimetric and single crystal X-ray structural analyses, as well as IR, UV–vis and EPR spectroscopies. Moreover, 1, 2 and 4 were tested for the catalytic degradations of methyl orange (MO) with H2O2.

The adsorption of xylyl-substituted biquaternary ammonium salt Gemini surfactants with different spacer (C3 and C6) at polytetrafluoroethylene (PTFE) and polymethylmethacrylate (PMMA) surfaces has been investigated and the different adsorption parameters such as surface tension, contact angle, adhesional tension, solid-water interfacial tension and work of adhesion have been estimated. The results show that C3 and C6 have similar adsorption behaviors at PTFE and PMMA surfaces. C3 and C6 adsorb gradually at a PFTE-water interface via hydrophobic interactions and the adsorption amounts at the water-air interface are almost three times higher than those at the PTFE-water interface due to the steric hindrance effect. However, the contact angle keeps constant throughout the experimental concentration range because the decrease in surface tension just counterbalances the decrease in PFTE-water interfacial tension. On the other hand, C3 and C6 adsorb at the PMMA surface via polar interactions between xylyl and functional groups of PMMA before CMC. Similar to PTFE, the increase in PMMA-water interfacial tension compensates the decrease in surface tension and the contact angle also shows a stationary value before the CMC. A bi-layer structure of C3 and C6 will be formed at the PMMA-water interface via hydrophobic interaction and PMMA-water interfacial tension decreases consequently after the CMC, which results in the decrease in contact angle.

Oxo and thiomolybdenum(IV/VI) imidazole hydrocitrates K2{MoIV3O4(im)3[MoVIO3(Hcit)]2}·3im·4H2O (1), (Him)2{MoIV3SO3(im)3[MoVIO3(Hcit)]2}·im·6H2O (2), molybdenum(V) bipyridine homocitrate trans-[(MoVO)2O(H2homocit)2(bpy)2]·4H2O (3) and molybdenum(VI) citrate (Et4N)[MoVIO2Cl(H2cit)]·H2O (4) (H4cit = citric acid, H4homocit = homocitric acid, im = imidazole and bpy = 2,2′-bipyridine) with different oxidation states were prepared. 1 and 2 are the coupling products of [MoVIO3(Hcit)]3− anions and incomplete cubane units [MoIV3O4]4+ ([MoIV3SO3]4+) with monodentate imidazoles, respectively, where tridentate citrates coordinate with α-hydroxy, α-carboxy and β-carboxy groups, forming pentanuclear skeleton structures. The molybdenum atoms in 1 and 2 show unusual +4 and +6 valences based on charge balances, theoretical bond valence calculations and Mo XPS spectrum. The coordinated citrates in 1 and 2 are protonated with α-hydroxy groups, while 3 and 4 with higher oxidation states of +5 and +6 are deprotonated with α-alkoxy group even under strong acidic condition, respectively. This shows the relationship between the oxidation state and protonation of the α-alkoxy group in citrate or homocitrate, which is related to the protonation state of homocitrate in FeMo-cofactor of nitrogenase. The homocitrate in 3 chelates to molybdenum(V) with bidentate α-alkoxy and monodentate α-carboxy groups. Molybdenum(VI) citrate 4 is only protonated with coordinated and uncoordinated β-carboxy groups. The solution behaviours of 1 and 2 are discussed based on 1H and 13C NMR spectroscopies and cyclic voltammograms, showing no decomposition of the species.

Extended surfactants have shown great potential in enhanced oil recovery (EOR). In this paper, the effects of extended surfactant concentration, polypropylene oxide (PO) number, and various counter ions (Na+, Ca2+, and Mg2+) on the oil-water interfacial tension (IFT) of extended surfactant solutions were investigated in detail. The selected extended surfactants were sodium dodecyl polyoxypropylene sulfate (L-C12POmS, m=5, 10, 15). Based on our experimental results, under NaCl conditions, with an increase in the PO number, the space occupied by the surfactant molecules on the side of the oil phase increases, which matches the size of the anionic head, and the surfactant film becomes tight. An ultralow IFT value appears for L-C12PO15S at 0.5% NaCl against decane. The addition of bivalent cations can significantly reduce the IFT. As the Ca2+ concentration increases, IFTs of APS solutions against alkanes can achieve ultralow values at lower PO numbers and against alkanes with a wide ACN range. For the MgCl2 system, the smaller hydration radius of Mg2+ improves the tightness of the anionic head, resulting in a crowded arrangement of the PO chains on the oil phase side. Therefore, the ability of Mg2+ to reduce the IFT against alkanes is weaker than that of Ca2+. Moreover, the surface-active substances in the crude oil adsorb competitively on the interface, resulting in an increase in IFT. By adding Ca2+or Mg2+, a tight adsorption film of surfactant molecules will be formed, and the IFT value reaches ultralow against crude oil. The studies in this paper have important implications for the application of extended surfactant solutions to enhance oil recovery under high salt reservoir conditions.

Protonation of FeMo-cofactor (FeMo-co) is important for the process of substrate hydrogenation. Its structure has been clarified as Δ-Mo*Fe7S9C(R-homocit*)(cys)(Hhis) after the efforts of nearly 30 years, but it remains controversial whether FeMo-co is protonated or deprotonated with chelated ≡C − O(H) homocitrate. We have used protonated molybdenum(V) lactate 1 and its enantiomer as model compounds for R-homocitrate in FeMo-co of nitrogenase. Vibrational circular dichroism (VCD) spectrum of 1 at 1051 cm−1 is attributed to ≡C − OH vibration, and molybdenum(VI) R-lactate at 1086 cm−1 is assigned as ≡C − Oα-alkoxy vibration. These vibrations set up labels for the protonation state of coordinated α-hydroxycarboxylates. The characteristic VCD band of NMF-extracted FeMo-co is assigned to ν(C − OH), which is based on the comparison of molybdenum(VI) R-homocitrate. Density functional theory calculations are consistent with these assignments. To the best of our knowledge, this is the first time that protonated R-homocitrate in FeMo-co is confirmed by VCD spectra.

The dynamic interfacial tensions (IFTs) of four extended surfactants (S-C12PO13S, L-C12PO4S, L-C16PO4S and L-C12PO11S) with different alkyl chain length and polypropylene oxide (PO) group against hydrocarbons were investigated. The mechanism responsible for the IFT reduction for extended surfactant has been detected. According to experimental results, we found that only when the size of hydrophobic part is enlarged to match the size of anionic head, the ultralow IFT will appear at optimized hydrophilic-lipophilic balance. For extended surfactants, with an increase of PO number, the curled PO chains occupy larger spaces at interface and match the size of anionic head. As a result, the ultralow IFT appears against alkanes when PO number is 13. The increase of alkyl chain length shows little effect on the size of hydrophobic part and ability of reducing IFT. Moreover, with an increase of n-alkane carbon number (ACN), the size of hydrophobic part increases as a function of ACN. Therefore, the increase of size of hydrophobic part compensates the decrease of adsorbed amount when ACN is higher than nmin value (the n-alkanes carbon number when the IFTs reach the minimum), which results in the “L” shape of IFT curve with a function of ACN.

Glutamine gets transformed to 2-hydroxy-5-oxoproline with NH

A series of monomeric α-hydroxycarboxylato oxovanadium(IV) complexes [VO(H2cit)(tpy)]·H2O (1) (H4cit = citric acid, tpy = 2,2′:6′,2-terpyridine), [VO(glyc)(tpy)]·5.5H2O (2) (H2glyc = glycolic acid) and [VO(α-hbut)(tpy)]·3H2O (3) (α-H2hbut = α-hydroxybutyratic acid) have been obtained from the reactions of vanadyl sulfate with α-hydroxycarboxylates and terpyridine in acidic solutions. These complexes feature bidentate citrate, glycolate or α-hydroxybutyrate respectively. The ligand chelates to vanadium atom through α-hydroxy (in 1) or α-alkoxy (in 2 and 3) and α-carboxy groups, while β-carboxy groups of citrate in 1 are free to participate strong hydrogen bonds with neighboring citrate. With comparable chelation, 1 shares a similar V–Oα-hydroxy distance [2.168(1) A] with that observed in FeV-cofactor [2.17 A] [1]. Moreover, nitrosyl vanadium complexes [V(NO)(glyc)(tpy)]·3H2O (4) and [V(NO)(α-hbut)(tpy)]·4H2O (5) were obtained via reductions of synthetic solutions of 2 and 3 with hydroxylamine respectively. The terminal oxygen atoms were substituted by linear nitrosyl groups in 4 and 5. They were fully characterized by UV–vis, IR, EPR spectra, X-ray structural analyses and theoretical bond valence calculations.

The water flooding of the medium-high permeability conglomerate reservoir in Badaowan Formation in wellblock 530 of block 8, Karamay oilfield has entered the “two-high (high water cut and high recovery percent of reserves)” stage, and the development effect is gradually becoming poor. Based on the experience of optimization and field test of binary combination flooding system in lower Karamay conglomerate reservoir of block Qizhong, we carried out evaluation on the interfacial tension and emulsifying ability of betaine/KPS mixed surfactant system and the adsorption resistance capacity of polymer-betaine/KPS mixed binary system, and used the artificial core to carry out laboratory oil displacement experiment. Based on the geological conditions of the reservoir, we selected 4 injectors and 9 producers to build a fine geological model, and used the numerical simulation method to carry out optimization and obtained the reasonable injection parameters of the formula system. The study results show that the interfacial tension and emulsifying properties of betaine/KPS mixed surfactant system are excellent: when the KPS/betaine ratio is in the range of 7:3–3:7, the interfacial tension can be ultra-low, the water separation ratio of the mixed system largely reduces, and the emulsion stability of the system is significantly improved; the adsorption resistance property of polymer-betaine/KPS mixed binary system is excellent: the ultra-low static adsorption times exceeds 3–4, and after having adsorbed for 8 times, the interfacial tension is still lower than 5 × 10−2 mN/m. The core displacement test in lab shows that the oil displacement efficiency of betaine/KPS mixed system is 26%, about 2% higher than that of single KPS system. The polymer concentration is 1,850 mg/L and the surfactant mass concentration is 0.2 wt% in the binary mixed system obtained from numerical simulation optimization.