Pedro Vidinha

Lipase catalysed mono and di-acylation of secondary alcohols with succinic anhydride in organic media and ionic liquids

The acylation of the model substrate (R,S)-2-octanol with succinic anhydride catalysed by immobilised Candida antarcticalipase B was studied in two water-miscible organic solvents, two water-immiscible ones, nine 1-alkyl-3-methylimidazolium ionic liquids (RTILs) and two quaternary ammonium RTILs. From previous reports, the reaction was expected to yield an acidic half ester (hemiester). However, it was found that the diester was also produced, in many cases at an even higher yield. The major reaction products were the (R)-hemiester and the (R,R)-diester. In some of the solvents, the amount of hemiester formed increased and then remained constant, whereas in others the amount of hemiester first peaked and then decayed. This behaviour could be explained by the coupling of two reaction pathways: the hydrolysis of the hemiester, and the esterification of the hemiester. The solubility limit of succinic acid, produced in the former pathway, was found to be a discriminating parameter, the precipitation of the acid acting as a driving force for the consumption of the hemiester formed. The impact of the choice of solvent on the outcome of the acylation with succinic anhydride was confirmed by conducting the reaction on a preparative scale: in acetonitrile, the reaction produced 32% (w/w) of (R)-hemiester and 68% (w/w) of (R,R)-diester, whereas in tetrahydrofuran 85% (w/w) of (R)-hemiester and 15% (w/w) of (R,R)-diester were obtained.

Understanding the Ion Jelly Conductivity Mechanism

The properties of the light flexible device, ion jelly, which combines gelatin with an ionic liquid (IL) were recently reported being promising to develop safe and highly conductive electrolytes. This article aims for the understanding of the ion jelly conductive mechanism using dielectric relaxation spectroscopy (DRS) in the frequency range 10(-1)-10(6) Hz; the study was complemented with differential scanning calorimetry (DSC) and pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy. The room temperature ionic liquid 1-butyl-3-methylimmidazolium dicyanamide (BMIMDCA) used as received (1.9% w/w water content) and with 6.6% (w/w) of water content and two ion jellies with two different ratios BMIMDCA/gelatin/water % (w/w), IJ1 (41.1/46.7/12.2) and IJ3 (67.8/25.6/6.6), have been characterized. A glass transition was detected by DSC for all materials allowing for classifying them as glass formers. For the ionic liquid, it was observed that the glass transition temperature decreases with the increase of water content. While in subsequent calorimetric runs crystallization was observed for BMIMDCA with negligible water content, no crystallization was detected for any of the ion jelly materials upon themal cycling. To the dielectric spectra of all tested materials, both dipolar relaxation and conductivity contribute; at the lowest frequencies, electrode and interfacial polarization highly dominate. Conductivity, which manifests much more intensity relative to dipolar reorientations, strongly evidences subdiffusive ion dynamics at high frequencies. From dielectric measures, transport properties as mobility and diffusion coefficients were extracted. Data treatment was carried out in order to deconvolute the average diffusion coefficients estimated from dielectric data in its individual contributions of cations (D(+)) and anions (D(-)). The D(+) values thus obtained for IJ3, the ion jelly with the highest IL/gelatin ratio, cover a large temperature range up to room temperature and revealed excellent agreement with direct measurements from PFG NMR, obeying to the same VFT equation. For BMIMDCA(6.6%water), which has the same water amount as IJ3, the diffusion coefficients were only estimated from DRS measurements over a limited temperature range; however, a single VFT equation describes both DRS and PFG NMR data. Moreover, it was found that the diffusion coefficients and mobility are similar for the ionic liquid and IJ3, which points to a role of both water and gelatin weakening the contact ion pair, facilitating the translational motion of ions and promoting its dissociation; nevertheless, it is conceivable the existence of a critical composition of gelatin that leads to those properties. The VFT temperature dependence observed for the conductivity was found to be determined by a similar dependence of the mobility. Both conductivity and segmental motion revealed to be correlated as inferred by the relatively low values of the decoupling indexes. The obtained results show that ion jelly could be in fact a very promising material to design novel electrolytes for different electrochemical devices, having a performance close to the IL but presenting an additional stability regarding electrical measurements and resistance against crystallization relative to the bulk ionic liquid.

Ion Jelly Conductive Properties Using Dicyanamide-Based Ionic Liquids

The thermal behavior and transport properties of several ion jellys (IJs), a composite that results from the combination of gelatin with an ionic liquid (IL), were investigated by dielectric relaxation spectroscopy (DRS), differential scanning calorimetry (DSC), and pulsed field gradient nuclear magnetic resonance spectroscopy (PFG NMR). Four different ILs containing the dicyanamide anion were used: 1-butyl-3-methylimidazolium dicyanamide (BMIMDCA), 1-ethyl-3-methylimidazolium dicyanamide (EMIMDCA), 1-butyl-1-methylpyrrolidinium dicyanamide (BMPyrDCA), and 1-butylpyridinium dicyanamide (BPyDCA); the bulk ILs were also investigated for comparison. A glass transition was detected by DSC for all materials, ILs and IJs, allowing them to be classified as glass formers. Additionally, an increase in the glass transition temperature upon dehydration was observed with a greater extent for IJs, attributed to a greater hindrance imposed by the gelatin matrix after water removal, rendering the IL less mobile. While crystallization is observed for some ILs with negligible water content, it was never detected for any IJ upon thermal cycling, which persist always as fully amorphous materials. From DRS measurements, conductivity and diffusion coefficients for both cations (D+) and anions (D-) were extracted. D+ values obtained by DRS reveal excellent agreement with those obtained from PFG NMR direct measurements, obeying the same VFTH equation over a large temperature range (ΔT ≈ 150 K) within which D+ varies around 10 decades. At temperatures close to room temperature, the IJs exhibit D values comparable to the most hydrated (9%) ILs. The IJ derived from EMIMDCA possesses the highest conductivity and diffusion coefficient, respectively, ∼10(-2) S·cm(-1) and ∼10(-10) m(2)·s(-1). For BMPyrDCA the relaxational behavior was analyzed through the complex permittivity and modulus formalism allowing the assignment of the detected secondary relaxation to a Johari-Goldstein process. Besides the relevant information on the more fundamental nature providing physicochemical details on ILs behavior, new doorways are opened for practical applications by using IJ as a strategy to produce novel and stable electrolytes for different electrochemical devices.

Probing the microenvironment of sol-gel entrapped cutinase: the role of added zeolite NaY.

Cutinase, an esterase from Fusarium solani pisi, was immobilized in sol-gel matrices of composition 1:5 tetramethoxysilane (TMOS):n-alkyltrimethoxysilane (n-alkylTMS). Fluorescence spectroscopy using the single tryptophan (Trp-69) residue of cutinase as a probe revealed that the polarity of the matrices decreased as their hydrophobicity increased up to the TMOS/n-butylTMS pair, which correlates with an increase in cutinase activity. Fluorescence emission was suppressed (a higher than two orders of magnitude reduction) in the TMOS/n-octylTMS matrix, suggesting a greater proximity of the tryptophan to a nearby disulfide bridge. When sol-gel matrices were prepared with added zeolite NaY, the fluorescence emission intensity maximum (lambda(max)) of the tryptophan did not change. And although the presence of the zeolite led to the recovery of fluorescence emission from the TMOS/n-octylTMS matrix, the corresponding lambda(max) fell in line with the values obtained for the matrices with lower n-alkyl chain lengths, indicating that the tryptophan does not sense the zeolite. On the other hand, the presence of the zeolite led to increases in cutinase activity in all the matrices. This suggests that the zeolite is in a position to affect the active site of the enzyme, located at the opposite pole of the enzyme molecule. Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed that the zeolite particles were segregated to the pores of the matrices. Optical microscopy following the staining of the protein with a fluorescent dye showed that the enzyme was distributed throughout the material, and tended to accumulate around zeolite particles. By promoting the accumulation of the enzyme at the pores of the material, the zeolite should improve the accessibility of the enzyme to the substrates and lead to a higher enzymatic activity. Data obtained for sol-gel matrices with epoxy or SH groups provided further evidence that cutinase responded to changes in the chemical nature of the precursors.

Development of antimicrobial Ion Jelly fibers

We report a method to obtain electrospun fibers based on ionic liquids and gelatin, exhibiting antimicrobial properties.

Assessing diffusion in enzyme loaded sol–gel matrices

Pulsed field gradient spin echo high resolution magic angle spinning nuclear magnetic resonance spectroscopy is a powerful technique to characterize confined biosystems. We used this approach to assess the diffusion of solvent and reaction species within sol–gel matrices differing in enzyme loading.

Ionic Liquids Gelation with Polymeric Materials: The Ion Jelly Approach

Nuno M.T. Lourenco1, Ana V.M. Nunes2, Catarina M.M. Duarte3,4 and Pedro Vidinha2 1IBB/CEBQ Departamento de Bioengenharia, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Avenida Rovisco Pais, Lisboa, 2Requimte/CQFB, Departamento de Quimica, Faculdade de Ciencias e Tecnologia Universidade Nova de Lisboa, Campus de Caparica, Caparica, 3Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Avenida da Republica, Oeiras, 4Instituto de Biologia Experimental e Tecnologica, Apartado 12, Oeiras, Portugal

Evaluation of Ion Jelly biopolymer on glucose biosensing

The kinetics of Glucose oxidase (GOD) and Horseradish peroxidase (HRP) on a transparent Ion Jelly biopolymer has been investigated using a colorimetric assay of H2O2 with phenol-4-sulfonic acid and 4-aminoantipyrine, as color-generating precursors. The activity of GOD and HRP on the Ion Jelly biopolymer solid disk formed in the bottom of the well ELISA plate showed to be respectively 16 times and 13 times lower than in free sodium phosphate buffer. The storage stability at 4°C of the both immobilized enzymes showed that GOD can retain up to 70% of the initial activity after two weeks, where HRP retained 91% of its initial activity. The drop cast deposition of the transparent Ion Jelly biopolymer containing the two enzymes (GOD, HRP) and the color-generating precursors on filter paper allowed to demonstrate their applicability on colorimetric glucose detection.