Comparison of the hydrodynamics and mass transfer characteristics in internal-loop airlift bioreactors utilizing either a novel membrane-tube sparger or perforated plate sparger

Two gas spargers, a novel membrane-tube sparger and a perforated plate sparger, were compared in terms of hydrodynamics and mass transfer (or oxygen transfer) performance in an internal-loop airlift bioreactor. The overall gas holdup ε _T, downcomer liquid velocity V _d, and volumetric mass transfer coefficient K _L a were examined depending on superficial gas velocity U _G increased in Newtonian and non-Newtonian fluids for the both spargers. Compared with the perforated plate sparger, the bioreactor with the membrane-tube sparger increased the values of ε _T by 4.9–48.8 % in air–water system when the U _G was from 0.004 to 0.04 m/s, and by 65.1–512.6 % in air–CMC solution system. The V _d value for the membrane-tube sparger was improved by 40.0–86.3 %. The value of K _L a was increased by 52.8–84.4 % in air–water system, and by 63.3–836.3 % in air–CMC solution system. Empirical correlations of ε _T, V _d, and K _L a were proposed, and well corresponding with the experimental data with the deviation of 10 %.     

Ecological notes on the species of Phacus Dujardin (Euglenophyta) from the central region of Portugal

Twenty-one species, belonging to the genus Phacus, were identified during the study of samples from the central region of Portugal collected in lentic systems. The abundance of each taxon was determined. Water samples were taken for determination, by means of standard methods, of physicochemical parameters (water temperature, pH, organic matter (K₂Cr₂O₇), conductivity, alkalinity, nitrogen as N(NH₄⁺), N(NO₂^–) and N(NO₃^–), orthophosphate P(PO₄^3–) and metals in a total of 35 parameters). Some species were found more frequently, namely Phacus agilis Skuja, Ph. aenigmaticus Drez., Ph. caudatus Hübn., Ph. gigas Da Cunha, Ph. triqueter (Ehr.) Duj., Ph. longicauda (Ehr.) Duj. and Ph. tortus (Lemm.) Skv. Eighteen taxa were found in the sampling sites characterized by the following variation intervals of the environmental parameters: water temperature: 11.4–21.6 °C; pH: 6.2–7.5; dichromate oxidability: 10–59 mg l^–1; conductivity: 145–779 μS cm^–1; nitrogen as NO₃^–: n.d.–2.852 mg l^–1; orthophosphate: n.d.–0.892 mg l^–1; chloride: 14.2–109.3 mg l^–1; sodium: 10.3–47.5 mg l^–1 and total iron: 135–6446 μg l^–1. In this work, information concerning the environmental conditions that preceded the occurrence of these species as well as results of the cytological and morphologic studies (with bright field microscopy as a resource) is presented and discussed.     

Density functional studies of the stepwise substitution of pyrrole, furan, and thiophene with BCO

The structures, stabilities, and aromaticities of a series of (BCO) _n (CH)_4–n NH (n?=?0–4), (BCO) _n (CH)_4–n O (n?=?0–4), and (BCO) _n (CH)_4–n S (n?=?0–4) clusters were investigated at the B3LYP density functional level of theory. The most stable positional isomers of the individual clusters were obtained. All of the calculated CO binding energies were exothermic, suggesting that these BCO-substituted species are stable. Calculated differences in strain energy between the BCO-substituted structures and their corresponding hydrocarbon clusters were all exothermic, indicating that the BCO-substituted structures are less strained. The negative nucleus-independent chemical shift (NICS) values obtained show that these BCO-substituted clusters are aromatic compounds, in good agreement with the aromaticities of the corresponding hydrocarbon species. To aid further experimental investigations, CO-stretching frequencies were also computed.     

Some nitrated derivatives of N-acylchitosan

O-Nitratedchitosan (d.s. 1.5–1.8 for NO₂ was N-acylated with carboxylic anhydride to afford products (d.s. 1.4–1.8 for NO₂ in 78–100% yield, and N-acylchitosan (d.s. 1.0 for N-acyl was nitrated with fuming nitric acid-acetic anhydride to afford products (d.s. 1.7–2.0 for NO₂ in 90–100% yield. N-Benzoylchitosan was nitrated with fuming nitric acid-acetic anhydride to afford a product of d.s. 3.0 for NO₂. All the products were soluble in methanesulphonic acid. The nitrated products containing N-fatty acyl groups (> C₂) were soluble in N, N-dimethylformamide and dimethyl sulphoxide, but the nitrated products containing N-fatty acyl groups (> C₆) were insoluble or swelled. O-Nitrated chitosan (d.s. 1.5–1.8 for NO₂) had ignition points 150–1562C, but the nitrated products containing N-acyl groups had no ignition point, and decomposed at over 2402C.     

Nonlinear Dependences of Optical Properties of Spherical Core–Shell Silver–Gold and Gold–Silver Nanoparticles on Their Parameters

Modeling of nonlinear optical properties of spherical core–shell gold–silver and silver–gold nanoparticles (NPs) placed in water was carried out on the base of extended Mie theory. Efficiency cross sections of absorption σ _abs, scattering σ _sca, and extinction σ _ext of radiation with wavelengths λ?=?400 and 532 nm for core–shell NPs with constant core radii r ₀₀?=?5, 10, 20, and 40 nm and in the range of relative radii r ₁/r ₀₀?=?1–8 were calculated (r ₁ is the radius of shell). Dependences of optical properties of gold–silver and silver–gold NPs on increasing of core radius r ₀ in the range 0???r ₁ under condition r ₁?=?const and increasing of r ₀ under r ₁???r ₀?=?const were investigated. Results show the nonlinear behavior of optical properties of core–shell gold–silver and silver–gold NPs on radiation wavelengths (optical indexes of metals), different core and shell radii, and their correlation, on relative NP radii r ₁/r ₀₀. An increase and decrease of absorption, scattering, and extinction efficiency cross sections of core–shell NPs with changing of wavelengths, core and shell radii, and relative NP radii r ₁/r ₀₀ are established. These dependences can be used for experimental investigation of the interesting first stages of shell formation on core and optical determination of core–shell NP parameters.     

Force–velocity,force–power relationships of bilateral and unilateral leg multi-joint movements in young and elderly women

The present study investigated force–velocity and force–power relationships of bilateral and unilateral knee-hip extension movement in young and elderly women. Twelve healthy young (age, 19–31 yr) and 12 healthy elderly (age, 60–82 yr) women performed bilateral and unilateral knee-hip extension movements on the dynamometer against loads controlled by the servo system. Under the isotonic force condition, force–velocity relationships were measured. The maximum isometric force (F_max), unloaded velocity (V_max) and power output (P_max) of the movements were calculated from extrapolating force–velocity and force–power relationships. F_max and P_max of bilateral and unilateral knee-hip extension movements were 20–30% lower in elderly than in young women. On the other hand, there were no significant differences in V_max between young and elderly women and between bilateral and unilateral movements. Bilateral deficit was larger as the generation of force was larger in both young and elderly women. Also, bilateral deficit of F_max and P_max were not different between young and elderly women. The results were that lower maximum power output of bilateral and unilateral leg multi-joint movements in elderly women did not depend on the intrinsic shortening velocity of muscle action, but largely on reduction in force generating capacity. This suggests the importance of preventing a loss of force generating capacity of muscles during leg multi-joint movements in elderly women.     

Structural transitions in mixed ternary noble gas clusters

The properties of noble gas systems can be greatly extended by heterogeneous mixtures of elements. The geometrical structures and energies of mixed Ar–Kr–Xe clusters were investigated using ternary Lennard-Jones (TLJ) potential. For the Ar₁₉Kr _n Xe₁₉, Ar₁₉Kr₁₉Xe _n , and Ar _n Kr₁₉Xe₁₉ (n?=?0–17) clusters investigated, the results show that only two minimum energy configurations exist, i.e., polytetrahedron and six-fold pancake. The inner core of all these clusters is composed mainly of Ar atoms, and Kr and Xe atoms are distributed on the surface with well mixed pattern for polytetrahedral and segregate pattern for six-fold pancake configurations. The relative stability property of Ar–Kr–Xe clusters with a certain composition is discussed. Moreover, the role of heterogeneity on the strain was investigated, and reduced strain energies in Ar–Kr–Xe clusters were studied to find possible ways of reducing strain. The results showed that the strain energies were affected mainly by Ar–Ar, Ar–Kr, and Xe–Xe bonds.

Land cover change effects on soil chemical and biological properties after planting Mongolian pine (Pinus sylvestris var. mongolica) in sandy lands in Keerqin, northeastern China

We compared soil moisture content, pH, total organic carbon (C _org), total nitrogen (TN), total phosphorus (TP) and inorganic N (NH₄ ⁺–N, NO₃ ^?–N) concentrations, soil potential C and N mineralization rates, soil microbial biomass C (C _mic), soil metabolic quotient (qCO₂), soil microbial quotient (C _mic/C _org) and soil enzyme (urease and invertase) activities in semiarid sandy soils under three types of land cover: grassland, Mongolian pine (Pinus sylvestris var. mongolica) plantation, and elm (Ulmus punila)–grass savanna in southeastern Keerqin, in northeast China. Soil C _org, TN and TP concentrations (0–10, 10–20, 20–40 and 40–60 cm) were lower while soil C/N and C/P ratios were higher in the plantation than in grassland and savanna. The effects of land cover change on NH₄ ⁺–N and NO₃ ^?–N concentrations, soil potential nitrification and C mineralization rates in the surface soil (0–10 cm) were dependent on sampling season; but soil potential N mineralization rates were not affected by land cover type and sampling season. The effects of land cover change on C _mic and qCO₂ of surface soil were not significant; but C _mic/C _org were significantly affected by land cover change and sampling season. We also found that land cover change, sampling season and land cover type?×?sampling season interaction significantly influenced soil enzyme (urease and invertase) activities. Usually soil enzyme activities were lower in the pine plantations than in grassland and savanna. Our results suggest that land cover change markedly influenced soil chemical and biological properties in sandy soils in the semiarid region, and these effects vary with sampling season.     

Nanoscale mono- and multi-layer cylinder structures formed by recombinant S-layer proteins of mosquitocidal Bacillus sphaericus C3-41

The mature surface layer (S-layer) protein SlpC of mosquitocidal Bacillus sphaericus C3-41 comprises amino acids 31–1,176 and could recrystallize in vitro. The N-terminal SLH domain is responsible for binding function. Deletion of this part, S-layer proteins could not bind to the cell wall sacculi. To investigate the self-assembly ability of SlpC from B. sphaericus, nine truncations were constructed and their self-assembly properties were compared with the recombinant mature S-layer protein rSlpC_31–1,176. The results showed that rSbsC_31–1,176 and truncations rSlpC_211–1,176, rSlpC_278–1,176, rSlpC_31–1,100, and rSlpC_31–1,050 could assemble into multilayer cylinder structures, while N-terminal truncations rSlpC_338–1,176, rSlpC_438–1,176, and rSlpC_498–1,176 mainly showed monolayer cylinders in recombinant Escherichia coli BL21 (DE3) cells. Growth phase analysis of the self-assembly process revealed that rSlpC_498–1,176 mainly formed monolayer cylinders in the early stage (0.5 and 1 h induction of expression), but few double-layer or multilayer cylinders were also found with the cells growing, while rSlpC_31–1,176 could formed multilayer cylinders in all the growth stage in the E. coli cells. It is concluded that the deletion of the C-terminal 126 aa or the N-terminal 497 aa did not interfere with the self-assembly process, the fragment (amino acids 278 to 337) is essential for the multilayer cylinder formation in E. coli BL21 (DE3) cells in the early stage and the fragment (amino acids 338 to 497) is related to monolayer cylinder formation. The information is important for further studies on the assembly mechanism of S-layer proteins and forms a basis for further studies concerning surface display and nanobiotechnology.     

Preparation of Biologically Active Recombinant Human Progastrin1–80

The bacterial expression of human progastrin_6–80 has been reported previously [Baldwin, G.S. et al. (2001) J. Biol. Chem. 276: 7791-7796]. The aims of the present study were to prepare full-length recombinant human progastrin_1–80 and to compare its biological activity with that of progastrin_6–80 in vitro, to determine whether or not the N-terminal five amino acids contributed to activity. A fusion protein of glutathione-S-transferase and human progastrin_1–80 was expressed in Escherichia coli, collected on glutathione-agarose beads, and cleaved with enterokinase. Progastrin_1–80 was purified by reversed-phase and anion exchange HPLC and characterized by radioimmunoassay, amino acid sequencing, and mass spectrometry. No differences were detected in the extent of stimulation by progastrin_1–80 and progastrin_6–80 in proliferation and migration assays with the mouse gastric cell line IMGE-5. We conclude that residues 1–5 of progastrin_1–80 are not essential for biological activity.     

Wax esters of the new zealand silver fern,Cyathea dealbata

The New Zealand silver fern epicuticular wax contained wax esters (C₃₈–C₆₀) of which the C₄₀–C₅₂ homologues were shown by capillary column GC/MS to comprise C₂₂–C₃₄ even and odd n-alkanols randomly combined with C₁₆–C₂₄ even n-acids.     

Hydrogen-Producing Microflora and Fe–Fe Hydrogenase Diversities in Seaweed Bed Associated with Marine Hot Springs of Kalianda, Indonesia

Microbial fermentation is a promising technology for hydrogen (H₂) production. H₂ producers in marine geothermal environments are thermophilic and halotolerant. However, no one has surveyed an environment specifically for thermophilic bacteria that produce H₂ through Fe–Fe hydrogenases (H₂ase). Using heterotrophic medium, several microflora from a seaweed bed associated with marine hot springs were enriched and analyzed for H₂ production. A H₂-producing microflora was obtained from Sargassum sp., 16S rRNA genes and Fe–Fe H₂ase diversities of this enrichment were also analyzed. Based on 16S rRNA genes analysis, 10 phylotypes were found in the H₂-producing microflora showing 90.0–99.5 % identities to known species, and belonged to Clostridia, Gammaproteobacteria, and Bacillales. Clostridia were the most abundant group, and three Clostridia phylotypes were most related to known H₂ producers such as Anaerovorax odorimutans (94.0 % identity), Clostridium papyrosolvens (98.4 % identity), and Clostridium tepidiprofundi (93.1 % identity). For Fe–Fe H₂ases, seven phylotypes were obtained, showing 63–97 % identities to known Fe–Fe H₂ases, and fell into four distinct clusters. Phylotypes HW55-3 and HM55-1 belonged to thermophilic and salt-tolerant H₂-producing Clostridia, Halothermothrix orenii-like Fe–Fe H₂ases (80 % identity), and cellulolytic H₂-producing Clostridia, C. papyrosolvens-like Fe–Fe H₂ases (97 % identity), respectively. The results of both 16S rRNA genes and Fe–Fe H₂ases surveys suggested that the thermophilic and halotolerant H₂-producing microflora in seaweed bed of hot spring area represented previously unknown H₂ producers, and have potential application for H₂ production.     

Enhanced anti-tumor effects of HPV16E749–57-based vaccine by combined immunization with poly(I:C) and oxygen-regulated protein 150

Background: It is well known that both heat shock protein (HSP) and Toll-like receptor (TLR)3 agonist polyinosinic:polycytidylic acid (poly(I:C)) are capable of promoting the antigen-specific immune responses. In the current study, we assessed whether the anti-tumor effects of the HPV16E7_49–57-based vaccine can be elevated by combined applications of poly(I:C) and oxygen-regulated protein 150 (ORP150) in a mouse cervical cancer model. Methods: Recombinant mouse ORP150 and HPV E7_49–57 peptide were combined to passively form the ORP150–E7_49–57 complex under heat shock conditions. The effects of ORP150–E7_49–57 complex plus poly(I:C) adjuvant on lymphocyte proliferation and functional cytotoxic T cells were investigated by methyl thiazolyl tetrazolium (MTT), ELISPOT, and non-radioactive cytotoxicity assays. Finally, the complex's therapeutic anti-tumor effects with and without adjuvant therapy were observed in a tumor challenge experiment. Results: This combination vaccine approach significantly enhanced the proliferation of splenocytes and induced strong E7_49–57-speci?c CTL responses. More importantly, the ORP150–E7_49–57 complex plus poly(I:C) vaccine format demonstrated more potent anti-tumor effects than ORP150–E7_49–57 complex alone or E7_49–57 plus poly(I:C) in TC-1 tumor-bearing mice. Conclusion: Both poly(I:C) and ORP150 chaperone can synergistically enhance the anti-tumor effects of the HPV16E7_49–57-based vaccine in vitro and in vivo. This strategy provides a platform for the design of a tumor therapeutic vaccine capable of inducing an effective anti-tumor immune response.     

Transformation of triplet induced Cotton effects of the methylene blue complexes of some sulphate derivatives of chitosan

Sulphate derivatives (DS 0.8–2.0 for sulphate) of chitosan and N-acylchitosan formed their complexes with Methylene Blue (MB), and the metachromasy and two types of triplet induced Cotton effects (500–700 nm) were produced: the derivatives (DS <0.6 for N-acyl) exhibited three negative-positive-negative extrema at 504–538 (λ₁), 544–565 (λ₂), and 594–615 nm (λ₃), and those (DS >0.7 for N-acyl) exhibited the reverse triplet extrema. When the MB complexes were treated t 70°C for 5 min, both the induced Cotton effects transformed into a novel triplet one with marked changes in the ellipticity and with the sign inversion. The extrema at λ₂ and λ₃ were just reverse to those of the doublet induced Cotton effect of MB-heparin complexes, which was little affected by temperature.     

Phosphorothioate analogs of sn-2 radyl lysophosphatidic acid (LPA): Metabolically stabilized LPA receptor agonists

We describe an efficient synthesis of metabolically stabilized sn-2 radyl phosphorothioate analogs of lysophosphatidic acid (LPA), and the determination of the agonist activity of each analog for the six LPA receptors (LPA_1–6) using a recently developed TGFα shedding assay. In general, the sn-2 radyl OMPT analogs showed similar agonist activities to the previous 1-oleoyl-2-O-methyl-glycerophosphothioate (sn-1 OMPT) analogs for LPA_1–6 receptors. In most cases, the sn-2 radyl-OMPT analogs were more potent agonists than LPA itself. Most importantly, sn-2 alkyl OMPT analogs were very potent LPA₅ and LPA₆ agonists. The availability of sn-2 radyl OPMT analogs further refines the structure–activity relationships for ligand–receptor interactions for this class of GPCRs.     

Modulation of the electron-proton coupling at cytochrome a by the ligation of the oxidized catalytic center in bovine cytochrome c oxidase

Cytochrome a was suggested as the key redox center in the proton pumping process of bovine cytochrome c oxidase (CcO). Recent studies showed that both the structure of heme a and its immediate vicinity are sensitive to the ligation and the redox state of the distant catalytic center composed of iron of cytochrome a₃ (Fe_a3) and copper (Cu_B). Here, the influence of the ligation at the oxidized Fe_a3³⁺–Cu_B²⁺ center on the electron–proton coupling at heme a was examined in the wide pH range (6.5-11). The strength of the coupling was evaluated by the determination of pH dependence of the midpoint potential of heme a (E_m(a)) for the cyanide (the low-spin Fe_a3³⁺) and the formate-ligated CcO (the high-spin Fe_a3³⁺). The measurements were performed under experimental conditions when other three redox centers of CcO are oxidized. Two slightly differing linear pH dependencies of E_m(a) were found for the CN– and the formate–ligated CcO with slopes of −13 mV/pH unit and −23 mV/pH unit, respectively. These linear dependencies indicate only a weak and unspecific electron–proton coupling at cytochrome a in both forms of CcO. The lack of the strong electron–proton coupling at the physiological pH values is also substantiated by the UV–Vis absorption and electron–paramagnetic resonance spectroscopy investigations of the cyanide–ligated oxidized CcO. It is shown that the ligand exchange at Fe_a³⁺ between His–Fe_a³⁺–His and His–Fe_a³⁺–OH⁻ occurs only at pH above 9.5 with the estimated pK >11.0.     

The E2P-like state induced by magnesium fluoride complexes in the Na,K-ATPase. Kinetics of formation and interaction with Rb+

The first X-ray crystal structures of the Na,K-ATPase were obtained in the presence of magnesium and fluoride as E2(K₂)Mg–MgF₄, an E2∙Pi-like state capable to occlude K⁺ (or Rb⁺). This work presents a functional characterization of the crystallized form of the enzyme and proposes a model to explain the interaction between magnesium, fluoride and Rb⁺ with the Na,K-ATPase. We studied the effect of magnesium and magnesium fluoride complexes on the E1–E2 conformational transition and the kinetics of Rb⁺ exchange between the medium and the E2(Rb₂)Mg–MgF₄ state. Our results show that both in the absence and in the presence of Rb⁺, simultaneous addition of magnesium and fluoride stabilizes the Na,K-ATPase in an E2 conformation, presumably the E2Mg–MgF₄ complex, that is unable to shift to E1 upon addition of Na⁺. The time course of conformational change suggests the action of fluoride and magnesium at different steps of the E2Mg–MgF₄ formation. Increasing concentrations of fluoride revert along a sigmoid curve the drop in the level of occluded Rb⁺ caused by Mg^2 +. Na⁺-induced release of Rb⁺ from E2(Rb₂)Mg–MgF₄ occurs at the same rate as from E2(Rb₂) but is insensitive to ADP. The rate of Rb⁺ occlusion into the E2Mg–MgF₄ state is 5–8 times lower than that described for the E2Mg–vanadate complex. Since the E2Mg–MgF₄ and E2Mg–vanadate complexes represent different intermediates in the E2-P → E2 dephosphorylation sequence, the variation in occlusion rate could provide a tool to discriminate between these intermediates.     

Antibacterial effect and proteomic analysis of graphene-based silver nanoparticles on a pathogenic bacterium Pseudomonas aeruginosa

Graphene-based silver nanoparticles (Ag NPs–GE) material has been developed and demonstrated antibacterial effect against Escherichia coli and Pseudomonas aeruginosa. In this study, the antibacterial activity and mechanism on P. aeruginosa were investigated. The experiments results showed the minimum bactericidal concentration of Ag NPs–GE to P. aeruginosa is 20 μg/ml. When P. aeruginosa were exposed to 20 μg/ml Ag NPs–GE for 1 h, the cell wall was breakdown. In order to study the mechanism of antibacterial effect of Ag NPs–GE, two-dimensional electrophoresis was carried out to compare the protein expressional profiles of P. aeruginosa exposed to 5 μg/ml Ag NPs–GE or 5 μg/ml AgNO₃ with the untreated bacteria. Identification of differentially expressed protein was performed by MALDI–TOF/TOF MS. The change of proteomic profile induced by Ag NPs–GE was distinct from that induced by AgNO₃. Seven identified proteins were found induced and nine proteins were suppressed by Ag NPs–GE. Five identified proteins were found induced and twenty proteins were suppressed by AgNO₃. In addition, either Ag NPs–GE or AgNO₃ suppressed the expression of eight proteins, amidotransferase, 30S ribosomal protein S6, bifunctional proline dehydrogenase/pyrroline-5-carboxylate dehydrogenase, arginyl-tRNA synthetase, nitroreductase, acetolactate synthase 3, methionyl-tRNA synthetase and periplasmic tail-specific protease. Furthermore, gene ontology analysis and KEGG pathway analysis were used to characterize the functions of those proteins.     

Hydrolysis of the amide bond in histidine- and methionine-containing dipeptides promoted by pyrazine and pyridazine palladium(II)-aqua dimers: Comparative study with platinum(II) analogues

Two dinuclear palladium(II) complexes, [{Pd(en)Cl}₂(μ-pz)](NO₃)₂ and [{Pd(en)Cl}₂(μ-pydz)](NO₃)₂, have been synthesized and characterized by elemental microanalysis and spectroscopic (¹H and ¹³C NMR, IR and UV–vis) techniques (en is ethylenediamine; pz is pyrazine and pydz is pyridazine). The square planar geometry of palladium(II) metal centers in these complexes has been predicted by DFT calculations. The chlorido complexes were converted into the corresponding aqua complexes, [{Pd(en)(H₂O)}₂(μ-pz)]⁴⁺ and [{Pd(en)(H₂O)}₂(μ-pydz)]⁴⁺, and their reactions with N-acetylated l-histidylglycine (Ac–l–His–Gly) and l-methionylglycine (Ac–l–Met–Gly) were studied by ¹H NMR spectroscopy. The palladium(II)-aqua complexes and dipeptides were reacted in 1:1 M ratio, and all reactions performed in the pH range 2.0 < pH < 2.5 in D₂O solvent and at 37 °C. In the reactions of these complexes with Ac–l–His–Gly and Ac–l–Met–Gly dipeptides, the hydrolysis of the amide bonds involving the carboxylic group of both histidine and methionine amino acids occurs. The catalytic activities of the palladium(II)-aqua complexes were compared with those previously reported in the literature for the analogues platinum(II)-aqua complexes, [{Pt(en)(H₂O)}₂(μ-pz)]⁴⁺ and [{Pt(en)(H₂O)}₂(μ-pydz)]⁴⁺.