Megaprosthesis use in Paprosky III/IV femoral defects in non-oncological patients: analysis of survival, clinical, and functional outcomes after an average follow-up of five years.

PURPOSE: To determine the survival and patient-reported outcomes in non-oncological patients treated with proximal femoral resection (PFR) using MEG for femoral reconstruction. MATERIALS AND METHODS: This retrospective study included 16 patients. Demographic variables and complications developed were analyzed. Clinical-functional outcomes were measured using the modified Harris score (mHSS), numeric Pain Rating Scale (NPRS) and Musculoskeletal Tumor Society (MSTS) score. MEG survival was estimated using a Kaplan-Meier survival analysis. RESULTS: Average follow-up was 5 years (range, 1-9). The 75% of patients were overweight and women with an average age of 74.2 ± 5.9-years (BMI of 28.5 ± 4.2 kg/m2). The main cause of MEG was periprosthetic infection (43.7%). The 50% of patients had post-surgical complications regarding with MEG, being the most frequent seromas and MEG dislocation. Implant survival was 93.4% and 80.9% at 3 and 7 years of follow-up, respectively. The functional results at the end of the follow-up with respect to the pre-surgical state improved from 9.5 ± 2.6 to 3 ± 0.9 mean NPRS and 26.5 ± 6.8 to 69.5 ± 13.5 mean mHHS, p < 0.001, respectively. The mean MSTS score was 68.1% that these results were considered excellent. CONCLUSIONS: The MEG for reconstruct III-IV femoral defects is a good therapeutic option that offers an acceptable clinical-functional result. Short-term and medium-term survival was greater than 80%. The most frequent complications are seromas and MEG dislocation. The use of constrained liner and abductor system reconstruction is essential to prevent the dislocation.

Unicompartmental knee arthroplasties: does the type of tibial component selected influence implant survival?

INTRODUCTION: Few information has been published on the survival of unicompartmental knee arthroplasty (UKA) and fixed-bearing tibial components. The aim of this study is to analyze if UKA survival varies according to UKA model used and to analyze the possible risk factors for UKA revision. MATERIALS AND METHODS: A retrospective study analyzing 301 UKAs (ACCURIS, all-polyethylene tibial component, 152; Triathlon PKR, metal-backed tibial component, 149) was performed. Demographic parameters as well as implant survival and cause of prosthetic revision were analyzed. The Kaplan-Meier survival analysis, the log-rank test and the Cox multiple regression were used for the analysis. RESULTS: Average follow-up was 8.1 ± 3.08-years. Average age was 68.1 ± 8.6-years; 70.4% of subjects were women. The ACCURIS UKA group had a UKA revision rate higher compared to the Triathlon PKR group (16/152, 10.6% vs 5/149, 3.4%, respectively; p < 0.001). The main cause of prosthetic revision was aseptic loosening (5/21, 23.8%). All aseptic loosening cases and tibial component collapse were reported with the ACCURIS UKA group. Overall UKA survival was 98.01% (95% CI 95.62-99.1) at 1-year, 94.27% (95% CI 90.95-96.4) at 5-years and 92.38% (95% CI 88.48-94.99) at 10-years' follow-up. There were no differences in the Kaplan-Meier survival curves regarding operated side or affected tibiofemoral compartment (log-rank test = 0.614 and 0.763, respectively). However, Kaplan-Meier survival curve according to UKA model used was different (log-rank test = 0.033). The metal-backed component appeared to be a protector factor for UKA revision when adjusted for age, sex, operated side, and affected tibiofemoral compartment (Hazard Ratio 0.32, p = 0.031). CONCLUSION: Fixed-bearing UKAs showed excellent mid- and long-term survival rates. Aseptic loosening is the main cause of implant failure. PKR group (metal-backed component) seem to be a protector factor to UKA revision when it was compared with ACCURIS UKA group (all-polyethylene tibial component).

Electroassisted Incorporation of Ferrocene within Sol-Gel Silica Films to Enhance Electron Transfer.

The sol-gel method is a straightforward technique that allows electrode modification with silica thin films. Furthermore, the silica pores could be functionalized to enhance the electrical conductivity and reactivity of the silica films. In this context, silica thin films were functionalized with ferrocene species. This functionalization was performed by electroassisted accumulation, generating a micro-structured composite electrode (Fc@SiO2 electrode). These modified electrodes were characterized by electrochemical and spectroelectrochemical methods, pointing out that ferrocene species were confined with high stability within the microporous silica thin film, demonstrating the good adsorption capacity of the silica. While the spectroelectrochemical characterization indicates that only a fraction of the confined species within the silica films were electroactive, the electrochemical results demonstrate that the Fc@SiO2 film enhances the electrochemical response of cytochrome c in a solution, which gives rise to further applications of these films for redox-controlled release and electrochemical detection of other redox-active proteins.

Fluorescent Nanocomposite Hydrogels Based on Conjugated Polymer Nanoparticles as Platforms for Alkaline Phosphatase Detection.

This work describes the development and characterization of fluorescent nanocomposite hydrogels, with high swelling and absorption capacity, and prepared using a green protocol. These fluorescent materials are obtained by incorporating, for the first time, polyfluorenes-based nanoparticles with different emission bands-poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(1,4-benzo-{2,1,3}-thiadiazole)] (F8BT)-into a three-dimensional polymeric network based on polyacrylamide. To this end, two strategies were explored: incorporation of the nanoparticles during the polymerization process (in situ) and embedment after the hydrogel formation (ex situ). The results show that the combination of PFO nanoparticles introduced by the ex situ method provided materials with good storage stability, homogeneity and reproducibility properties, allowing their preservation in the form of xerogel. The fluorescent nanocomposite hydrogels have been tested as a transportable and user-friendly sensing platform. In particular, the ability of these materials to specifically detect the enzyme alkaline phosphatase (ALP) has been evaluated as a proof-of-concept. The sensor was able to quantify the presence of the enzyme in an aqueous sample with a response time of 10 min and LOD of 21 nM. Given these results, we consider that this device shows great potential for quantifying physiological ALP levels as well as enzyme activity in environmental samples.

Disposable Electrochemical Biosensor Based on the Inhibition of Alkaline Phosphatase Encapsulated in Acrylamide Hydrogels.

The present work describes the development of an easy-to-use portable electrochemical biosensor based on alkaline phosphatase (ALP) as a recognition element, which has been immobilized in acrylamide-based hydrogels prepared through a green protocol over disposable screen-printed electrodes. To carry out the electrochemical transduction, an electroinactive substrate (hydroquinone diphosphate) was used in the presence of the enzyme and then it was hydrolyzed to an electroactive species (hydroquinone). The activity of the protein within the matrix was determined voltammetrically. Due to the adhesive properties of the hydrogel, this was easily deposited on the surface of the electrodes, greatly increasing the sensitivity of the biosensor. The device was optimized to allow the determination of phosphate ion, a competitive inhibitor of ALP, in aqueous media. Our study provides a proof-of-concept demonstrating the potential use of the developed biosensor for in situ, real-time measurement of water pollutants that act as ALP inhibitors.

Chirality influence on the cytotoxic properties of anionic chiral bis(N-heterocyclic carbene)silver complexes.

Complexes Na3[Ag(NHCR)2], 2a-e and 2b'-c', where NHCR is a N-heterocyclic carbene of the 2,2'-(1H-2λ3,3λ4-imidazole-1,3-diyl)dicarboxylate type, were prepared by treatment of compounds HLR, 1a-e and 1b'-c' (2-(1-(carboxyalkyl)-1H-imidazol-3-ium-3-yl)carboxylate), with silver oxide in the presence of aqueous sodium hydroxide. They were characterized by analytical, spectroscopic (infrared, IR, 1H and 13C nuclear magnetic resonance, NMR, and circular dichroism) and X-ray methods (2a). In the solid state, the anionic part of complex 2a, [Ag(NHCH)2]3-, shows a linear disposition of Ccarbene-Ag-Ccarbene atoms and an eclipsed conformation of the two NHC ligands. The proposed bis(NHC) nature of the silver complexes was maintained in solution according to NMR and density functional theory (DFT) calculations. The cytotoxic activity of compounds 2 was evaluated against four cancer cell lines and one non-cancerous cell line and several structure-activity correlations were found for these complexes. For instance, the activity decreased when the bulkiness of the R alkyl group in Na3[Ag(NHCR)2] increased. More interesting is the detected chirality-anticancer relationship, where complexes Na3[Ag{(S,S)-NHCR}2] (R = Me, 2b; iPr, 2c) showed better anticancer activity than those of their enantiomeric derivatives Na3[Ag{(R,R)-NHCR}2] (R = Me, 2b'; iPr, 2c').

Antimicrobial Properties of Amino-Acid-Derived N-Heterocyclic Carbene Silver Complexes.

Complexes {Ag[NHCMes,R]}n (R = H, 2a; Me, 2b and 2b'; iPr, 2c; iBu, 2d), were prepared by treatment of imidazolium precursor compounds [ImMes,R] (2-(3-mesityl-1H-imidazol-3-ium-1-yl)acetate, 1a, (S)-2-alkyl(3-mesityl-1H-imidazol-3-ium-1-yl)acetate, 1b-d, and (R)-2-methyl(3-mesityl-1H-imidazol-3-ium-1-yl)acetate, 1b', with Ag2O under appropriate conditions. They were characterised by analytical, spectroscopic (IR, 1H, and 13C NMR and polarimetry), and X-ray methods (2a). In the solid state, 2a is a one-dimensional coordination polymer, in which the silver(I) cation is bonded to the carbene ligand and to the carboxylate group of a symmetry-related Ag[NHCMes,H] moiety. The coordination environment of the silver centre is well described by the DFT study of the dimeric model {Ag[NHCMes,H]}2. The antimicrobial properties of these complexes were evaluated versus Gram-negative bacteria E. coli and P. aeruginosa. From the observed MIC and MBC values (minimal inhibitory concentration and minimal bactericidal concentration, respectively), complex 2b' showed the best antimicrobial properties (eutomer), which were significantly better than those of its enantiomeric derivative 2b (distomer). Additionally, analysis of MIC and MBC values of 2a-d reveal a clear structure-antimicrobial effect relationship. Antimicrobial activity decreases when the steric properties of the R alkyl group in {Ag[NHCMes,R]}n increase.

Homochiral imidazolium-based dicarboxylate silver(I) compounds: synthesis, characterisation and antimicrobial properties.

Complexes [Ag(LR)], 2 (LR = 2,2'-(imidazolium-1,3-diyl)di(2-alkylacetate)), were prepared by treatment of compounds HLR, 1, with Ag2O. They were characterised by analytical, spectroscopic (IR, 1H and 13C NMR and polarimetry) and X-ray methods (2c, 2c' and 2e). In the solid state, these compounds are novel one-dimensional or two-dimensional coordination polymers in which silver(I) cations are connected via the chiral [LR]- anion with unprecedented coordination modes. The antimicrobial properties of these complexes were evaluated. 2a and 2b' showed the best antimicrobial properties (minimal inhibitory concentrations and minimal bactericidal concentration) for Pseudomonas aeruginosa and Escherichia coli pathogens. Eutomers 2b' and 2c' showed slightly better antimicrobial properties than their respective enantiomers 2b and 2c.

Reactive Insertion of PEDOT-PSS in SWCNT@Silica Composites and its Electrochemical Performance.

Hybrid silica-modified materials were synthesized on glassy carbon (GC) electrodes by electroassisted deposition of sol-gel precursors. Single-wall carbon nanotubes (SWCNTs) were dispersed in a silica matrix (SWCNT@SiO2) to enhance the electrochemical performance of an inorganic matrix. The electrochemical behavior of the composite electrodes was tested against the ferrocene redox probe. The SWCNT@SiO2 presents an improvement in the electrochemical performance towards ferrocene. The heterogeneous rate constant of the SWCNT@SiO2 can be enhanced by the insertion of poly(3,4-Ethylendioxythiophene)-poly(sodium 4-styrenesulfonate) PEDOT-PSS within the silica matrix, and this composite was synthesized successfully by reactive electrochemical polymerization of the precursor EDOT in aqueous solution. The SWCNT@SiO2-PEDOT-PSS composite electrodes showed a heterogeneous rate constant more than three times higher than the electrode without conducting polymer. Similarly, the electroactive area was also enhanced to more than twice the area of SWCNT@SiO2-modified electrodes. The morphology of the sample films was analyzed by scanning electron microscopy (SEM).

Synthesis and structural characterization of homochiral coordination polymers with imidazole-based monocarboxylate ligands.

Chiral Na[(S)-LR] (R = Me, 1a; iPr, 1b; CH2iPr, 1c, and (S)-secBu, 1d) and Na[(R)-LR] (R = Me, 1a') compounds were synthesised following standard procedures. New compounds 1d and 1a' were analytically and spectroscopically characterised. 1a and 1c were structurally identified by single-crystal X-ray diffraction methods as homochiral 2D coordination polymers, {Na(H2O)[(S)-LMe]}n and {Na[(S)-LCH2iPr]}n, respectively. Both (S)-2alkyl,2-(1H-imidazol-1-yl)acetate anions displayed unprecedented coordination modes in these coordination polymers: µ3κ2OκO' for 1a and µ4κ2Oκ2O' for 1c. Enantiomeric species 1a', {Na(H2O)[(R)-LMe]}n, showed the same X-ray powder diffractogram (XRPD) as 1a, in agreement with a similar crystal structure. DFT calculations on the [LR]- anions confirmed their coordination capabilities as ditopic linkers. In fact, the reaction of Na[LR] with several metal salts yielded the following coordination polymers: {Ag[(S)-LMe]}n, 2a, {Ag[(R)-LMe]}n, 2a', {Cu[(S)-LR]2}n (R = Me, 3a; iPr, 3b), {Cu[(R)-LMe]}n, 3a', {Zn[(S)-LR]2}n (R = Me, 4a; iPr, 4b; (S)-secBu, 4d) and {Zn[(R)-LMe]2}n, 4a'. For the known compounds 3a and 4a, this procedure is a new synthetic route that avoided high temperature reaction conditions. New complexes 2, 3a', b, and 4a', b, d were characterised by elemental analysis, infrared and XRPD methods and complex 2a by single-crystal X-ray diffraction. This complex is also a two-dimensional coordination polymer in which the [(S)-LMe]- anion acts as a µ4κN,κ2O,κ2O' bridging ligand. Compounds 1-4a' are the first examples of homochiral coordination polymers with imidazole-monocarboxylate ligands based on non-natural amino acids. Preliminary studies on the metal-catalysed preparation of chiral α-aminophosphonates were carried out but, unfortunately, no enantioselectivity was observed.

Affinity of Electrochemically Deposited Sol⁻Gel Silica Films towards Catecholamine Neurotransmitters.

Dopamine, norepinephrine, and epinephrine neurotransmitters can be detected by electrochemical oxidation in conventional electrodes. However, their similar chemical structure and electrochemical behavior makes a difficult selective analysis. In the present work, glassy carbon electrodes have been modified with silica layers, which were prepared by electroassisted deposition of sol⁻gel precursors. These layers were morphologically and compositionally characterized using different techniques, such as field emission scanning electron microscopy (FESEM), TEM, FTIR, or thermogravimetric analysis⁻mass spectrometry (TG-MS). The affinity of silica for neurotransmitters was evaluated, exclusively, by means of electrochemical methods. It was demonstrated that silica adsorbs dopamine, norepinephrine, and epinephrine, showing different interaction with silica pores. The adsorption process is dominated by a hydrogen bond between silanol groups located at the silica surface and the amine groups of neurotransmitters. Because of the different interaction with neurotransmitters, electrodes modified with silica films could be used in electrochemical sensors for the selective detection of such molecules.

Molybdenum-Catalyzed Enantioselective Sulfoxidation Controlled by a Nonclassical Hydrogen Bond between Coordinated Chiral Imidazolium-Based Dicarboxylate and Peroxido Ligands.

Chiral alkyl aryl sulfoxides were obtained by molybdenum-catalyzed oxidation of alkyl aryl sulfides with hydrogen peroxide as oxidant in mild conditions with high yields and moderate enantioselectivities. The asymmetry is generated by the use of imidazolium-based dicarboxylic compounds, HLR. The in-situ-generated catalyst, a mixture of aqueous [Mo(O)(O2)2(H2O)n] with HLR as chirality inductors, in the presence of [PPh4]Br, was identified as the anionic binuclear complex [PPh4]{[Mo(O)(O2)2(H2O)]2(µ-LR)}, according to spectroscopic data and Density Functional Theory (DFT) calculations. A nonclassical hydrogen bond between one C⁻H bond of the alkyl R group of coordinated (LR)− and one oxygen atom of the peroxido ligand was identified as the interaction responsible for the asymmetry in the process. Additionally, the step that governs the enantioselectivity was theoretically analyzed by locating the transition states of the oxido-transfer to PhMeS of model complexes [Mo(O)(O2)2(H2O)(κ¹-O-LR)]− (R = H, iPr). The ∆∆G≠ is ca. 0 kcal∙mol−1 for R = H, racemic sulfoxide, meanwhile for chiral species the ∆∆G≠ of ca. 2 kcal∙mol−1 favors the formation of (R)-sulfoxide.

An Electrochemical Study on the Copolymer Formed from Piperazine and Aniline Monomers.

A study on the electrochemical oxidation of piperazine and its electrochemical copolymerization with aniline in acidic medium is presented. It was found that the homopolymerization of piperazine cannot be achieved under electrochemical conditions. A combination of electrochemistry, in situ Fourier transform infrared (FTIR), and ex situ X-ray photoelectron spectroscopy (XPS) spectroscopies was used to characterize both the chemical structure and the redox behavior of an electrochemically synthesized piperazine⁻aniline copolymer. The electrochemical sensing properties of the deposited material were also tested against ascorbic acid and dopamine as redox probes.

Oxidoperoxidomolybdenum(vi) complexes with acylpyrazolonate ligands: synthesis, structure and catalytic properties.

Oxidoperoxido-molybdenum(vi) complexes containing acylpyrazolonate ligands were obtained by reaction of [Mo(O)(O)2(H2O)n] with the corresponding acylpyrazolone compounds HQR. Complexes Ph4P[Mo(O)(O2)2(QR)] (R = neopentyl, 1; perfluoroethyl, 2; hexyl, 3; phenyl, 4; naphthyl, 5; methyl, 6; cyclohexyl, 7; ethylcyclopentyl, 8) were obtained if the reaction was carried out with one equivalent of HQR in the presence of Ph4PCl. Alternatively, neutral complexes [Mo(O)(O2)(QR)2] (R = neopentyl, 9; hexyl, 10; cyclohexyl, 11) were formed when two equivalents of HQR were used in the reaction. These complexes were isolated in good yields as yellow or yellow-orange crystalline solids and were spectroscopically (IR, 1H, 13C{1H} and 31P{1H} NMR), theoretically (DFT) and structurally characterised (X-ray for 1, 2, 9 and 10). Compounds 1 and 9 were selected to investigate their catalytic behaviour in epoxidation of selected alkenes and oxidation of selected sulphides, while 10 and 11 were tested as catalyst precursors in the deoxygenation of selected epoxide substrates to alkenes, using PPh3 as the oxygen-acceptor. Complexes Ph4P[Mo(O)(O2)2(QR)] were shown to be poor catalyst precursors in oxidation reactions, while the activity of [Mo(O)(O2)(QR)2] species is good in all the studied reactions and comparable to related oxidoperoxido-molybdenum(vi) complexes. Complex [Mo(O)2(QC6)2], 12, was obtained by treatment of 10 with one equivalent of PPh3, demonstrating that the first step in the epoxide deoxygenation mechanism was the oxygen atom transfer toward the phosphane.

Synthesis and structural characterization of homochiral 2D coordination polymers of zinc and copper with conformationally flexible ditopic imidazolium-based dicarboxylate ligands.

Different novel coordination polymers containing zinc, 1-4, and copper, 5-8, metals, connected via chiral imidazolium-based dicarboxylate ligands, [LR]-, were isolated by reaction between zinc acetate or copper acetate and enantiomerically pure HLR compounds. They were characterised and structurally identified by X-ray diffraction methods (single crystal and powder). These compounds are two-dimensional homochiral coordination polymers, [M(LR)2]n, in which the metal ions are coordinated by the two carboxylate groups of [LR]- anions in a general bridging monodentate µ2-κ1-O1,κ1-O3 fashion that afforded tetrahedral metal coordination environments for zinc, 1-4, and square planar for copper, 5-8, complexes. In all the compounds the 3D supramolecular architecture is constructed by non-covalent interactions between the hydrophobic parts (R groups) of the homochiral 2D coordination polymers and, in some cases, by weak C-HO non-classical hydrogen bonds that provided, in general, a dense crystal packing. DFT calculations on the [LR]- anions confirmed their conformational flexibility as ditopic linkers and this fact makes possible the formation of different coordination polymers for four-coordinated metal centers. Preliminary studies on the Zn-catalyzed synthesis of chiral α-aminophosphonates were carried out and, unfortunately, no enantioselectivity was observed in these reactions.

The HERC2 ubiquitin ligase is essential for embryonic development and regulates motor coordination.

A mutation in the HERC2 gene has been linked to a severe neurodevelopmental disorder with similarities to the Angelman syndrome. This gene codifies a protein with ubiquitin ligase activity that regulates the activity of tumor protein p53 and is involved in important cellular processes such as DNA repair, cell cycle, cancer, and iron metabolism. Despite the critical role of HERC2 in these physiological and pathological processes, little is known about its relevance in vivo. Here, we described a mouse with targeted inactivation of the Herc2 gene. Homozygous mice were not viable. Distinct from other ubiquitin ligases that interact with p53, such as MDM2 or MDM4, p53 depletion did not rescue the lethality of homozygous mice. The HERC2 protein levels were reduced by approximately one-half in heterozygous mice. Consequently, HERC2 activities, including ubiquitin ligase and stimulation of p53 activity, were lower in heterozygous mice. A decrease in HERC2 activities was also observed in human skin fibroblasts from individuals with an Angelman-like syndrome that express an unstable mutant protein of HERC2. Behavioural analysis of heterozygous mice identified an impaired motor synchronization with normal neuromuscular function. This effect was not observed in p53 knockout mice, indicating that a mechanism independent of p53 activity is involved. Morphological analysis showed the presence of HERC2 in Purkinje cells and a specific loss of these neurons in the cerebella of heterozygous mice. In these animals, an increase of autophagosomes and lysosomes was observed. Our findings establish a crucial role of HERC2 in embryonic development and motor coordination.

Synthesis, characterization and structure of nickel and copper compounds containing ligands derived from keto-enehydrazines and their catalytic application for aerobic oxidation of alcohols.

Ligand precursors HL(R,Ph) (R = Me, Ph) were synthesised by condensation of acetylacetone and the corresponding N,N-substituted hydrazines and were characterised spectroscopically and structurally. Both in the solid state and in solution they behave as (Z)-keto-enehydrazines and this was confirmed by DFT calculations which showed that this form was the most stable of their possible tautomers. The reaction of HL(R,Ph) compounds with copper acetate and nickel acetate in EtOH afforded the corresponding complexes [M(L(R,Ph))2] (M = Cu, Ni; R = Me, Ph). The methyl-substituted derivatives were structurally characterised by X-ray methods. A four-coordinate environment around the metal centre, where the two L(Me,Ph) ligands act as bidentate N,O-chelators and lie in a pseudo-trans conformation, was found for both compounds. The dihedral angle between the two six-membered metallacycles M(L(Me,Ph)) was 0° for nickel, a typical square planar coordination, meanwhile it was 23° for copper, a square planar slightly distorted to pseudotetrahedral coordination. Copper complexes [Cu(L(R,Ph))2] were tested as catalysts, in combination with TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl radical), for the aerobic oxidation of 4-nitrobenzyl alcohol as the model reaction. An almost complete conversion to the corresponding aldehyde was observed after 1 h at 60 °C and 1 bar of dioxygen, in toluene as the solvent. Importantly, air at atmospheric pressure was also observed to be appropriate for the oxidation, although longer reaction times were required. After the optimization of the reaction conditions, the study was extended to other alcohol substrates and good catalytic activity was found for benzylic-type alcohols, while low yield was found for 1-octanol.

Experimental and theoretical insights into the oxodiperoxomolybdenum-catalysed sulphide oxidation using hydrogen peroxide in ionic liquids.

The oxidation of organic sulphides with aqueous hydrogen peroxide in ionic liquids (ILs) catalysed by oxodiperoxomolybdenum complexes was investigated. The selective formation of several sulfones was achieved using the 1 : 3 ratio of sulphide : H2O2 in [C4mim][PF6] (C4mim = 1-butyl-3-methylimidazolium) in a reaction catalysed by the [Mo(O)(O2)2(H2O)n] complex. Conversely, sulfoxides were produced with good selectivities using a 1 : 1 ratio in the same solvent in a 1 h reaction with [Mo(O)(O2)2(Mepz)2] (Mepz = methylpyrazol). The use of [C4mim][PF6] as the solvent was advantageous for two reasons: (i) the improved performance of the H2O2-IL combination; (ii) recycling of the catalyst/IL mixture without a significant diminution of conversion or selectivity. A DFT analysis using the [Mo(O)(O2)2(L)] catalysts (L = Mepz, a; 3,5-dimethylpyrazole, dmpz, b; and H2O, c) indicated that a Sharpless-type outer-sphere mechanism is more probable than a Thiel-type one. The highest barrier of the catalytic profile was the oxo-transfer step, in which the nucleophilic attack of sulphide onto the peroxide ligand occurred with formation of dioxoperoxo species. In order to yield the sulfoxide and the starting catalyst, the oxidation of the resulting dioxoperoxo species with H2O2 was found to be the most favourable pathway. Subsequently, the sulfoxide to sulfone oxidation was performed through a similar mechanism involving the [Mo(O)(O2)2(L)] catalyst. The comparable energies found for the successive two oxo-transfer steps were in agreement with the experimental formation of sulfone in both the reaction with an excess of the oxidant and the stoichiometric reaction in the absence of the oxidant. In the latter case, diphenylsulfone was isolated as the major product in the 1 : 1 combination of diphenylsulphide and [Mo(O)(O2)2(Mepz)2] in the ionic liquid [C4mim][PF6]. Also, the compounds [HMepz]4[Mo8O26(Mepz)2]·2H2O, 1, [Hdmpz]4[Mo8O26(dmpz)2]·2dmpz, , and [Hpz]4[Mo8O22(O2)4(pz)2]·3H2O, 3, were obtained by treating in water, stoichiometrically, dimethylsulfoxide and the corresponding [Mo(O)(O2)2(L)2] complex (L = Mepz; 3,5-dimethylpyrazole, dmpz; pyrazol, pz). The crystal structures of octanuclear compounds 1-3 were indirect proof of the formation of the theoretically proposed intermediates.

Modulation of the silica sol-gel composition for the promotion of direct electron transfer to encapsulated cytochrome c.

The direct electron transfer between indium-tin oxide electrodes (ITO) and cytochrome c encapsulated in different sol-gel silica networks was studied. Cyt c@silica modified electrodes were synthesized by a two-step encapsulation method mixing a phosphate buffer solution with dissolved cytochrome c and a silica sol prepared by the alcohol-free sol-gel route. These modified electrodes were characterized by cyclic voltammetry, UV-vis spectroscopy, and in situ UV-vis spectroelectrochemistry. The electrochemical response of encapsulated protein is influenced by the terminal groups of the silica pores. Cyt c does not present electrochemical response in conventional silica (hydroxyl terminated) or phenyl terminated silica. Direct electron transfer to encapsulated cytochrome c and ITO electrodes only takes place when the protein is encapsulated in methyl modified silica networks.