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.

Sol-gel encapsulation: an efficient and versatile immobilization technique for cutinase in non-aqueous media.

Cutinase from Fusarium solani pisi was encapsulated in sol-gel matrices prepared with a combination of alkyl-alkoxysilane precursors of different chain-lengths. The specific activity of cutinase in a model transesterification reaction at fixed water activity in n-hexane was highest for the precursor combination tetramethoxysilane/n-butyltrimetoxysilane (TMOS/BTMS) in a 1:5 ratio, lower and higher chain lengths of the mono-alkylated precursor or decreasing proportions of the latter relative to TMOS leading to lower enzyme activity. Results obtained using combinations of three precursors confirmed the beneficial effect of the presence of BTMS in the preparations. Scanning electron microscopy of the 1:5 TMOS/n-alkylTMS gels showed a direct correlation between the macropore dimensions and the alkyl chain length of the alkylated precursor and revealed that TMOS/n-octylTMS gels suffered extensive pore collapse during the drying process. The specific activity of TMOS/BTMS sol-gel entrapped cutinase was similar to that exhibited by the enzyme immobilized by adsorption on zeolite NaY. However, the incorporation of different additives (zeolites, silica, Biogel, grinded sol-gel, etc.) having in common the capability to react with residual silanol groups of the sol-gel matrix brought about remarkable enhancements of cutinase activity, despite the fact that the global porosity of the gels did not change. The behavior of the gels in supercritical CO 2 (sc-CO 2) paralleled that exhibited in n-hexane, although cutinase activity was ca. one order of magnitude lower (i.e. sol-gel encapsulation did not prevent the deleterious effect of CO 2. The impact that functionalization of some of the additives had on cutinase activity indicates that the enzyme/matrix interactions must play an important role. Some of the best additives from the standpoint of enzyme activity were also the best from the standpoint of its operational stability (ca. 80% retention of enzyme activity at the tenth reutilization cycle). None of the additives that proved effective for cutinase could improve the catalytic activity of sol-gel encapsulated Pseudomonas cepacia lipase.

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.

[Clinical and epidemiological profile of ulcerative colitis in a hospital in Lima]. / Perfil clínico y epidemiológico de la colitis ulcerativa en un hospital de Lima.

UNLABELLED: The Non-specific Ulcerative Colitis (NUC) is an inflammatory disease of the rectum and the colon that can extend from the distal part of the rectum to the colon. Only in rare occasions is the terminal ileum compromised. OBJECTIVE: To know the clinic and epidemiological profile of the NUC, in the Edgardo Rebagliati Martins Hospital-EsSALUD (Lima-Peru). METHOD: Prospective and descriptive study of 43 patients diagnosed with NUC, from June, 2001 to May, 2003. RESULTS: The patients were 27 women (62.8%) and 16 men (37.2%); 31 from previous analysis (72.1%) and 12 new patients (27.9%); the largest compromised age group was between 30 to 39 years old (23.3%). The main symptoms were diarrhea (86%), rectal bleeding (58.1%), and abdominal pain (37.2%). Follow-up showed: remission (65.1%), recurrence (28%), persistency (2.3%) and fulminant course (2.3%). One patient died (2.3%). The colon compromise was: rectosigmoid (32.6%), left (30.3%), pancolitis (20.9%), to transverse (9.3%) and distal (6.9%). CONCLUSIONS: The incidence was of 2.1 cases per year, the average age was 45 years old (at the time of diagnosis), with a prevalence of women (62.8%). The main symptoms were diarrhea, rectal bleeding and abdominal pain. The main factor of recurrence was the interruption of the medication and anaemia was a frequent problem observed in the follow-up.