Cu(II) Coordination Polymers Containing Mixed Ligands with Different Flexibilities: Structural Diversity and Iodine Adsorption.

Reactions of N,N'-bis(3-methylpyridyl)oxalamide (L1), N,N'-bis(3-methylpyridyl)adipoamide (L2) and N,N'-bis(3-methylpyridyl)sebacoamide (L3) with tricarboxylic acids and Cu(II) salts afforded {[Cu(L1)(1,3,5-HBTC)]·H2O}n (1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid), 1, {[Cu1.5(L2)1.5(1,3,5-BTC)(H2O)2]·6.5H2O}n, 2, [Cu(L2)0.5(1,3,5-HBTB)]n (1,3,5-H3BTB = 1,3,5-tri(4-carboxyphenyl)benzene), 3, [Cu4(L3)(OH)2(1,3,5-BTC)2]n, 4, {[Cu3(L3)2(1,3,5-BTB)2]·2.5MeOH·2H2O}n, 5, and {[Cu3(L3)2(1,3,5-BTB)2 ]·DMF·2H2O}n, 6, which have been structurally characterized by using single crystal X-ray crystallography. Complexes 1-4 form a 2D layer with the {44.62}-sql topology, a 2D layer with the (4.62)2(42.62.82)-bex topology, a three-fold interpenetrated 3D net with the (412·63)-pcu topology and a 3D framework with the (410·632·83)(42·6)2(43·63) topology, respectively, whereas 5 and 6 are 3D frameworks with the (63)2(64·82)(68·85·102) topology. Complex 5 shows a better iodine adsorption factor of 290.0 mg g-1 at 60 °C for 360 min than the other ones, revealing that the flexibility of the spacer ligand governs the structural diversity and the adsorption capacity.

MOF-Derived Cu-BTC Nanowire-Embedded 2D Leaf-like Structured ZIF Composite-Based Aptamer Sensors for Real-Time In Vivo Insulin Monitoring.

Insulin, which is a hormone produced by the ß-cells of the pancreas, regulates the glucose levels in the blood and can transport glucose into cells to produce glycogen or triglycerides. Insulin deficiency can lead to hyperglycemia and diabetes. Therefore, insulin detection is critical in clinical diagnosis. In this study, disposable Au electrodes were modified with copper(II) benzene-1,3,5-tricarboxylate (Cu-BTC)/leaf-like zeolitic imidazolate framework (ZIF-L) for insulin detection. The aptamers are easily immobilized on the Cu-BTC/ZIF-L composite by physical adsorption and facilitated the specific interaction between aptamers and insulin. The Cu-BTC/ZIF-L composite-based aptasensor presented a wide linear insulin detection range (0.1 pM to 5 µM) and a low limit of detection of 0.027 pM. In addition, the aptasensor displayed high specificity, good reproducibility and stability, and favorable practicability in human serum samples. For the in vivo tests, Cu-BTC/ZIF-L composite-modified electrodes were implanted in non-diabetic and diabetic mice, and insulin was quantified using electrochemical and enzyme-linked immunosorbent assay methods.

Metal-organic framework on porous TiO2 thin film-coated alumina beads for fractional distillation of plant essential oils.

Fractionation of essential oils is technically challenging due to enormous scaffold diversities and structural complexities as well as difficulties in the implementation of the fractionation in the gas phase. Packing beads with multi-dimensional hierarchical nanostructures have been developed herein to pack fractional columns for atmospheric distillations. Activated alumina beads were coated with a porous TiO2 thin film. Growth of Cu-BTC (benzene-1,3,5-tricarboxylate) crystals in resultant porous surfaces leads to the generation of new nanopores and increased metal centers for differential coordination with diverse components of essential oils. The TiO2 thin film is not only an integral part of the composites but also induces the oriented growth of Cu-BTC metal organic framework (MOF) crystals through coordinative interactions. These Al2O3@TiO2@Cu-BTC MOF beads show very strong absorptive capability for major components of essential oils, except for a single cyclic ether eucalyptol with steric hindrances. The eucalyptol was fractionated by using the column packed with those modified alumina beads from raw materials of Artemisia argyi, and Rosmarinus officinalis with high purities up to 96% and 93%, respectively.

Tricarboxylate Citrate Transporter of an Oleaginous Fungus Mucor circinelloides WJ11: From Function to Structure and Role in Lipid Production.

The citrate transporter protein (CTP) plays an important role in citrate efflux from the mitochondrial matrix to cytosol that has great importance in oleaginous fungi. The cytoplasmic citrate produced after citrate efflux serves as the primary carbon source for the triacylglycerol and cholesterol biosynthetic pathways. Because of the CTP's importance, our laboratory has extensively studied its structure/function relationships in Mucor circinelloides to comprehend its molecular mechanism. In the present study, the tricarboxylate citrate transporter (Tct) of M. circinelloides WJ11 has been cloned, overexpressed, purified, kinetically, and structurally characterized. The Tct protein of WJ11 was expressed in Escherichia coli, isolated, and functionally reconstituted in a liposomal system for kinetic studies. Our results showed that Tct has a high affinity for citrate with Km 0.018 mM. Furthermore, the tct overexpression and knockout plasmids were created and transformed into M. circinelloides WJ11. The mitochondria of the tct-overexpressing transformant of M. circinelloides WJ11 showed a 49% increase in citrate efflux, whereas the mitochondria of the tct-knockout transformant showed a 39% decrease in citrate efflux compared to the mitochondria of wild-type WJ11. To elucidate the structure-function relationship of this biologically important transporter a 3D model of the mitochondrial Tct protein was constructed using homology modeling. The overall structure of the protein is V-shaped and its 3D structure is dimeric. The transport stability of the structure was also assessed by molecular dynamics simulation studies. The activity domain was identified to form hydrogen bond and stacking interaction with citrate and malate upon docking. Tricarboxylate citrate transporter has shown high binding energy of -4.87 kcal/mol to citric acid, while -3.80 kcal/mol to malic acid. This is the first report of unraveling the structural characteristics of WJ11 mitochondrial Tct protein and understanding the approach of the transporting toward its substrate. In conclusion, the present findings support our efforts to combine functional and structural data to better understand the Tct of M. circinelloides at the molecular level and its role in lipid accumulation.

Molybdenum Disulfide Supported on Metal-Organic Frameworks as an Ultrasensitive Layer for the Electrochemical Detection of the Ovarian Cancer Biomarker CA125.

Metal-organic frameworks (MOFs) are composed of metal ions/clusters and organic ligands, showing accessible functional sites, ultra-high porosity, and large specific surface area. Tricopper benzene-1,3,5-tricarboxylate (CuBTC), as a three-dimensional MOF architecture with an open and robust micro-/nanoconfiguration, possesses excellent catalytic performance and superior electric conductivity as compared to bulk MOF. In this study, CuBTC was used as a substrate on which molybdenum disulfide (MoS2) was in situ constructed by a hydrothermal reaction to enhance the electron- and ion-transfer capability. Then, gold nanoparticles (AuNPs) were electroreduced on a CuBTC@MoS2-modified electrode by linear sweep voltammetry for strengthening the connection between CA125 antibodies (CA125 Ab) and the substrate material. Due to the synergistic effect of CuBTC@MoS2 and AuNPs, our biosensor showed excellent electrochemical performance. Subsequently, CuBTC@MoS2-AuNPs/CA125 Ab-functionalized electrodes were used for the detection of the ovarian cancer biomarker CA125 from 0.5 mU/mL to 500 U/mL by differential pulse voltammetry. The results showed that the peak current decreased with the increase of concentration, and there was a logistic regression relationship between peak current variation and concentration. As interfering substances, carcinoembryonic antigen, human epididymis protein 4, and bovine serum albumin were applied for specific analysis. Our biosensor showed an obviously large response signal for CA125 detection than those observed for other interfering substances. Finally, serum samples collected from five patients were tested on our sensors with good consistency toward clinical standards, showing high practicability. This work demonstrated a tactic for simultaneously integrating the nanostructure, electroconductivity, and biocompatibility to construct advanced biosensors for cancer biomarkers.

Prediction of Autoimmune Diseases by Targeted Metabolomic Assay of Urinary Organic Acids.

Autoimmune diseases (ADs) are chronic disorders characterized by the loss of self-tolerance, and although being heterogeneous, they share common pathogenic mechanisms. Self-antigens and inflammation markers are established diagnostic tools; however, the metabolic imbalances that underlie ADs are poorly described. The study aimed to employ metabolomics for the detection of disease-related changes in autoimmune diseases that could have predictive value. Quantitative analysis of 28 urine organic acids was performed using Gas Chromatography-Mass Spectrometry in a group of 392 participants. Autoimmune thyroiditis, inflammatory bowel disease, psoriasis and rheumatoid arthritis were the most prevalent autoimmune diseases of the study. Statistically significant differences were observed in the tricarboxylate cycle metabolites, succinate, methylcitrate and malate, the pyroglutamate and 2-hydroxybutyrate from the glutathione cycle and the metabolites methylmalonate, 4-hydroxyphenylpyruvate, 2-hydroxyglutarate and 2-hydroxyisobutyrate between the AD group and the control. Artificial neural networks and Binary logistic regression resulted in the highest predictive accuracy scores (66.7% and 74.9%, respectively), while Methylmalonate, 2-Hydroxyglutarate and 2-hydroxybutyrate were proposed as potential biomarkers for autoimmune diseases. Urine organic acid levels related to the mechanisms of energy production and detoxification were associated with the presence of autoimmune diseases and could be an adjunct tool for early diagnosis and prediction.

A universal stress protein in Mycobacterium smegmatis sequesters the cAMP-regulated lysine acyltransferase and is essential for biofilm formation.

Universal stress proteins (USPs) are present in many bacteria, and their expression is enhanced under various environmental stresses. We have previously identified a USP in Mycobacterium smegmatis that is a product of the msmeg_4207 gene and is a substrate for a cAMP-regulated protein lysine acyltransferase (KATms; MSMEG_5458). Here, we explored the role of this USP (USP4207) in M. smegmatis and found that its gene is present in an operon that also contains genes predicted to encode a putative tripartite tricarboxylate transporter (TTT). Transcription of the TTT-usp4207 operon was induced in the presence of citrate and tartrate, perhaps by the activity of a divergent histidine kinase-response regulator gene pair. A usp4207-deleted strain had rough colony morphology and reduced biofilm formation compared with the WT strain; however, both normal colony morphology and biofilm formation were restored in a Δusp4207Δkatms strain. We identified several proteins whose acetylation was lost in the Δkatms strain, and whose transcript levels increased in M. smegmatis biofilms along with that of USP4207, suggesting that USP4207 insulates KATms from its other substrates in the cell. We propose that USP4207 sequesters KATms from diverse substrates whose activities are down-regulated by acylation but are required for biofilm formation, thus providing a defined role for this USP in mycobacterial physiology and stress responses.

Construction of (3,8)-connected three-dimensional cobalt(II) and copper(II) coordination polymers with 1,3-bis[(1,2,4-triazol-4-yl)methyl]benzene and benzene-1,3,5-tricarboxylate ligands.

Coordination polymers (CPs) have been widely studied because of their diverse and adjustable topologies and wide-ranging applications in luminescence, chemical sensors, magnetism, photocatalysis, gas adsorption and separation. In the present work, two coordination polymers, namely poly[(µ5-benzene-1,3,5-tricarboxylato-κ6O1:O1':O3:O3:O5,O5'){µ3-1,3-bis[(1,2,4-triazol-4-yl)methyl]benzene-κ3N:N':N''}di-µ3-hydroxido-dicobalt(II)], [Co2(C9H3O6)(OH)(C12H12N6)]n or [Co2(btc)(OH)(mtrb)]n, (1), and poly[[diaquabis(µ3-benzene-1,3,5-tricarboxylato-κ3O1:O3:O5)bis{µ3-1,3-bis[(1,2,4-triazol-4-yl)methyl]benzene-κ3N:N':N''}tetra-µ3-hydroxido-tetracopper(II)] monohydrate], {[Cu4(C9H3O6)2(OH)2(C12H12N6)2(H2O)2]·H2O}n or {[Cu4(btc)2(OH)2(mtrb)2(H2O)2]·H2O}n, (2), were synthesized by the hydrothermal method using 1,3-bis[(1,2,4-triazol-4-yl)methyl]benzene (mtrb) and benzene-1,3,5-tricarboxylate (btc3-). CP (1) exhibits a (3,8)-coordinated three-dimensional (3D) network of the 3,8T38 topological type, with a point symbol of {4,5,6}2{42·56·616·72·82}, based on the tetranuclear hydroxide cobalt(II) cluster [Co4(µ3-OH)2]. CP (2) shows a (3,8)-coordinated tfz-d topology, with a point symbol of {43}2{46·618·84}, based on the tetranuclear hydroxide copper(II) cluster [Cu4(µ3-OH)2]. The different (3,8)-coordinated 3D networks based on tetranuclear hydroxide-metal clusters of (1) and (2) are controlled by the different central metal ions [CoII for (1) and CuII for (2)]. The thermal stabilities and solid-state optical diffuse-reflection spectra were measured. The energy band gaps (Eg) obtained for (1) and (2) were 2.72 and 2.29 eV, respectively. CPs (1) and (2) exhibit good photocatalytic degradation of the organic dyes methylene blue (MB) and rhodamine B (RhB) under visible-light irradiation.

A tripartite tricarboxylate transporter (MIM_c39170-MIM_c39210) of Advenella mimigardefordensis DPN7T is involved in citrate uptake.

To date, tripartite tricarboxylate transport (TTT) systems are not well characterized in most organisms. To investigate which carbon sources are transported by the TTT system of A. mimigardefordensis DPN7T, single deletion mutants were generated lacking either completely both sets of genes encoding for these transport systems tctABCDE1 and tctABDE2 in the organism or the two genes encoding for the regulatory components of the third chosen TTT system, tctDE3. Deletion of tctABCDE1 (MIM_c39170-MIM_c39210) in Advenella mimigardefordensis strain DPN7T led to inhibition of growth of the cells with citrate indicating that TctABCDE1 is the transport system for the uptake of citrate. Because of the negative phenotype, it was concluded that this deletion cannot be substituted by other transporters encoded in the genome of strain DPN7T. A triple deletion mutant of A. mimigardefordensis lacking both complete TTT transport systems and the regulatory components of the third chosen system (ΔTctABCDE1 ΔTctABDE2 ΔTctDE3) showed a leaky growth with α-ketoglutarate in comparison with the wild type. The other investigated TTT (TctABDE3, MIM_c17190-MIM_c17220) is most probably involved in the transport of α-ketoglutarate. Additionally, thermoshift assays with TctC1 (MIM_c39190) showed a significant shift in the melting temperature of the protein in the presence of citrate whereas no shift occurred with α-ketoglutarate. A dissociation constant Kd for citrate of 41.7 µM was determined. Furthermore, alternative α-ketoglutarate transport was investigated via in silico analysis.

Tunable Light Emission and Multiresponsive Luminescent Sensitivities in Aqueous Solutions of Two Series of Lanthanide Metal-Organic Frameworks Based on Structurally Related Ligands.

Two series of lanthanide metal-organic frameworks (Ln-MOFs) from two structurally related flexible carboxylate-based ligands were solvothermally synthesized. H3L2 with additional -CH2- group provides more flexibility and different coordination modes and conformations compared with H3L1. As a result, 2-Ln MOFs are modulated from two-dimensional kgd of 1-Ln to three-dimensional rtl topological frameworks and further achieve enhanced chemical stability. The Eu- and Tb-MOFs exhibit strong fluorescent emission at the solid state because of the antenna effect of the ligands. Interestingly, the emissions can be tuned by simply doping Eu3+ and Tb3+ of different concentrations within the Eu xTb1- x MOFs. Notably, 2-Ln MOFs realize nearly white light emission by means of a trichromatic approach (red of Eu(III), green of Tb(III), and blue of the H3L2 ligand). Furthermore, 2-Ln MOFs also exhibit water stability and demonstrate high selective and sensitive sensing activities toward Fe(III) and Cr(VI) in aqueous solutions. The results further highlight the importance of the ligand flexibility on tuning MOF structures with improved structural stability and ion-sensing properties.

Graphene oxide wrapped copper-benzene-1,3,5-tricarboxylate metal organic framework as efficient absorbent for gaseous toluene under ambient conditions.

The ultrasonic-assisted hydrothermal and ethanol activation method was proposed to synthesize copper-benzene-1,3,5-tricarboxylate (Cu-BTC) metal organic framework and Cu-BTC/graphene oxide (GO) composites (Cu-BTC@GO). The dynamic adsorption behavior of toluene on two adsorbents was studied and compared with that of GO and reduced graphene oxide (RGO). The Cu-BTC@GO exhibited high adsorption capacity (183 mg/g) for toluene, which is nearly three times as much as that of Cu-BTC (62.7 mg/g) with the GO mass fraction of 20%. Furthermore, the adsorption of toluene on Cu-BTC@GO composites was positively correlated with the initial concentration of toluene and the adsorbent dosage, and negatively correlated with the temperature. The adsorption data of toluene on Cu-BTC@GO composites were well in accordance with pseudo-first kinetics model. Langmuir model had a better fit than Freundlich model. The adsorption thermodynamic results showed that the adsorption process was mainly physical adsorption and the adsorption process was spontaneous at low temperature. After five adsorption-desorption cycles, the adsorption efficiency can still reach 82.1%.This study will help to draw a promising roadmap to describe the adsorption performance of Cu-BTC@GO composites for toluene.

Rational modification of tricarboxylic acid cycle for improving L-lysine production in Corynebacterium glutamicum.

BACKGROUND: Oxaloacetate (OAA) and L-glutamate are essential precursors for the biosynthesis of L-lysine. Reasonable control of all potentially rate-limiting steps, including the precursors supply rate, is of vital importance to maximize the efficiency of L-lysine fermentation process. RESULTS: In this paper, we have rationally engineered the tricarboxylic acid (TCA) cycle that increased the carbon yield (from 36.18 to 59.65%), final titer (from 14.47 ± 0.41 to 23.86 ± 2.16 g L-1) and productivity (from 0.30 to 0.50 g L-1 h-1) of L-lysine by Corynebacterium glutamicum in shake-flask fermentation because of improving the OAA and L-glutamate availability. To do this, the phosphoenolpyruvate-pyruvate-oxaloacetate (PEP-pyruvate-OAA) node's genes ppc and pyc were inserted in the genes pck and odx loci, the P1 promoter of the TCA cycle's gene gltA was deleted, and the nature promoter of glutamate dehydrogenase-coding gene gdh was replaced by Ptac-M promoter that resulted in the final engineered strain C. glutamicum JL-69Ptac-M gdh. Furthermore, the suitable addition of biotin accelerates the L-lysine production in strain JL-69Ptac-M gdh because it elastically adjusts the carbon flux for cell growth and precursor supply. The final strain JL-69Ptac-M gdh could produce 181.5 ± 11.74 g L-1 of L-lysine with a productivity of 3.78 g L-1 h-1 and maximal specific production rate (qLys, max.) of 0.73 ± 0.16 g g-1 h-1 in fed-batch culture during adding 2.4 mg L-1 biotin with four times. CONCLUSIONS: Our results reveal that sufficient biomass, OAA and L-glutamate are equally important in the development of L-lysine high-yielding strain, and it is the first time to verify that fed-batch biotin plays a positive role in improving L-lysine production.

A plant-like mitochondrial carrier family protein facilitates mitochondrial transport of di- and tricarboxylates in Trypanosoma brucei.

The procyclic form of the human parasite Trypanosoma brucei harbors one single, large mitochondrion containing all tricarboxylic acid (TCA) cycle enzymes and respiratory chain complexes present also in higher eukaryotes. Metabolite exchange among subcellular compartments such as the cytoplasm, the mitochondrion, and the peroxisomes is crucial for redox homeostasis and for metabolic pathways whose enzymes are dispersed among different organelles. In higher eukaryotes, mitochondrial carrier family (MCF) proteins transport TCA-cycle intermediates across the inner mitochondrial membrane. Previously, we identified several MCF members that are essential for T. brucei survival. Among these, only one MCF protein, TbMCP12, potentially could transport dicarboxylates and tricarboxylates. Here, we conducted phylogenetic and sequence analyses and functionally characterised TbMCP12 in vivo. Our results suggested that similarly to its homologues in plants, TbMCP12 transports both dicarboxylates and tricarboxylates across the mitochondrial inner membrane. Deleting this carrier in T. brucei was not lethal, while its overexpression was deleterious. Our results suggest that the intracellular abundance of TbMCP12 is an important regulatory element for the NADPH balance and mitochondrial ATP-production.

Pathogenic mutations of the human mitochondrial citrate carrier SLC25A1 lead to impaired citrate export required for lipid, dolichol, ubiquinone and sterol synthesis.

Missense mutations of the human mitochondrial citrate carrier, encoded by the SLC25A1 gene, lead to an autosomal recessive neurometabolic disorder characterised by neonatal-onset encephalopathy with severe muscular weakness, intractable seizures, respiratory distress, and lack of psychomotor development, often resulting in early death. Here, we have measured the effect of all twelve known pathogenic mutations on the transport activity. The results show that nine mutations abolish transport of citrate completely, whereas the other three reduce the transport rate by >70%, indicating that impaired citrate transport is the most likely primary cause of the disease. Some mutations may be detrimental to the structure of the carrier, whereas others may impair key functional elements, such as the substrate binding site and the salt bridge network on the matrix side of the carrier. To understand the consequences of impaired citrate transport on metabolism, the substrate specificity was also determined, showing that the human citrate carrier predominantly transports citrate, isocitrate, cis-aconitate, phosphoenolpyruvate and malate. Although D-2- and L-2 hydroxyglutaric aciduria is a metabolic hallmark of the disease, it is unlikely that the citrate carrier plays a significant role in the removal of hydroxyglutarate from the cytosol for oxidation to oxoglutarate in the mitochondrial matrix. In contrast, computer simulations of central metabolism predict that the export of citrate from the mitochondrion cannot be fully compensated by other pathways, restricting the cytosolic production of acetyl-CoA that is required for the synthesis of lipids, sterols, dolichols and ubiquinone, which in turn explains the severe disease phenotypes.

Structural basis for high-affinity adipate binding to AdpC (RPA4515), an orphan periplasmic-binding protein from the tripartite tricarboxylate transporter (TTT) family in Rhodopseudomonas palustris.

The tripartite tricarboxylate transporter (TTT) family is a poorly characterised group of prokaryotic secondary solute transport systems, which employ a periplasmic substrate-binding protein (SBP) for initial ligand recognition. The substrates of only a small number of TTT systems are known and very few SBP structures have been solved, so the mechanisms of SBP-ligand interactions in this family are not well understood. The SBP RPA4515 (AdpC) from Rhodopseudomonas palustris was found by differential scanning fluorescence and isothermal titration calorimetry to bind aliphatic dicarboxylates of a chain length of six to nine carbons, with KD values in the µm range. The highest affinity was found for the C6-dicarboxylate adipate (1,6-hexanedioate). Crystal structures of AdpC, either adipate or 2-oxoadipate bound, revealed a lack of positively charged amino acids in the binding pocket and showed that water molecules are involved in bridging hydrogen bonds to the substrate, a conserved feature in the TTT SBP family that is distinct from other types of SBP. In AdpC, both of the ligand carboxylate groups and a linear chain conformation are needed for coordination in the binding pocket. RT-PCR showed that adpC expression is upregulated by low environmental adipate concentrations, suggesting adipate is a physiologically relevant substrate but as adpC is not genetically linked to any TTT membrane transport genes, the role of AdpC may be in signalling rather than transport. Our data expand the known ligands for TTT systems and identify a novel high-affinity binding protein for adipate, an important industrial chemical intermediate and food additive. DATABASES: Protein structure co-ordinates are available in the PDB under the accession numbers 5OEI and 5OKU.

A Porous Zirconium-Based Metal-Organic Framework with the Potential for the Separation of Butene Isomers.

By using a novel C3 -symmetrical tricarboxylate (4,4',4''-benzene-1,3,5-triyl-1,1',1''-trinaphthoic acid), a novel zirconium-based metal-organic framework ZJNU-30 was solvothermally synthesized and structurally characterized. Single-crystal X-ray structural analyses show that ZJNU-30 consists of Zr6 -based nodes connected by the organic linkers to form a (3,8)-connected network featuring the coexistence of two different polyhedral cages: octahedral and cuboctahedral cages with the dimensions of about 14 and 22 Å, respectively. Remarkably, ZJNU-30 is very stable when exposed to air for one month. More importantly, with a moderately high surface area, hierarchical pore structures, and an aromatic-rich pore surface in the framework, ZJNU-30, after activation, exhibits a promising potential for the selective adsorptive separation of industrially important butene isomers consisting of cis-2-butene, trans-2-butene, 1-butene, and iso-butene at ambient temperature. This separation was established exclusively by gas adsorption isotherms and simulated breakthrough experiments. To the best of our knowledge, this is the first study investigating porous metal-organic frameworks for butene-isomer separation.

Mitochondrial tricarboxylate and dicarboxylate-tricarboxylate carriers: from animals to plants.

The citrate carrier (CiC), characteristic of animals, and the dicarboxylate-tricarboxylate carrier (DTC), characteristic of plants and protozoa, belong to the mitochondrial carrier protein family whose members are responsible for the exchange of metabolites, cofactors, and nucleotides between the cytoplasm and the mitochondrial matrix. Most of the functional data on these transporters are obtained from the studies performed with the protein purified from rat, eel yeast, and maize mitochondria or recombinant proteins from different sources incorporated into phospholipid vesicles (liposomes). The functional data indicate that CiC is responsible for the efflux of acetyl-CoA from the mitochondria to the cytosol in the form of citrate, the primer for fatty acid, cholesterol synthesis, and histone acetylation. Like the CiC, the citrate exported by DTC from the mitochondria to the cytosol in exchange for oxaloacetate can be cleaved by citrate lyase to acetyl-CoA and oxaloacetate and used for fatty acid elongation and isoprenoid synthesis. In addition to its role in fatty acid synthesis, CiC is involved in other processes such as gluconeogenesis, insulin secretion, inflammation, and cancer progression, whereas DTC is involved in the production of glycerate, nitrogen assimilation, ripening of fruits, ATP synthesis, and sustaining of respiratory flux in fruit cells. This review provides an assessment of the current understanding of CiC and DTC structural and biochemical characteristics, underlying the structure-function relationship of these carriers. Furthermore, a phylogenetic relationship between CiC and DTC is proposed.

A novel three-dimensional Zn(II) coordination polymer with 1,3,5-tris(imidazol-1-ylmethyl)benzene and cyclohexane-1,3,5-tricarboxylate ligands.

In the Zn(II) compound poly[[bis(µ3-cyclohexane-1,3,5-tricarboxylato)bis[µ3-1,3,5-tris(imidazol-1-ylmethyl)benzene]trizinc(II)] hexahydrate], {[Zn3(C18H18N6)2(C9H9O6)2]·6H2O}n, based on mixed 1,3,5-tris(imidazol-1-ylmethyl)benzene and cyclohexane-1,3,5-tricarboxylate ligands, there are two types of crystallographically independent Zn(II) centres, one in a general position and one on a crystallographic twofold axis. They have similar fourfold distorted tetrahedral coordination geometries, ligated by two monodentate carboxylate groups from two cyclohexane-1,3,5-tricarboxylate ligands and by two N atoms from two 1,3,5-tris(imidazol-1-ylmethyl)benzene ligands. The cyclohexane-1,3,5-tricarboxylate anions link the Zn(II) cations to generate a two-dimensional layered metal-organic structure running parallel to the (201) plane. Adjacent layers are further connected by tripodal 1,3,5-tris(imidazol-1-ylmethyl)benzene ligands, resulting in a three-dimensional network. The solvent water molecules are linked to the cyclohexane-1,3,5-tricarboxylate ligands via water-carboxylate O-H···O hydrogen bonds.