Metal-Chelate Immobilization of Lipase onto Polyethylenimine Coated MCM-41 for Apple Flavor Synthesis

An enzyme immobilized on a mesoporous silica nanoparticle can serve as a multiple catalyst for the synthesis of industrially useful chemicals. In this work, MCM-41 nanoparticles were coated with polyethylenimine (MCM-41@PEI) and further modified by chelation of divalent metal ions (M = Co²⁺, Cu²⁺, or Pd²⁺) to produce metal-chelated silica nanoparticles (MCM-41@PEI-M). Thermomyces lanuginosa lipase (TLL) was immobilized onto MCM-41, MCM-41@PEI, and MCM-41@PEI-M by physical adsorption. Maximum immobilization yield and efficiency of 75 ± 3.5 and 65 ± 2.7% were obtained for MCM@PEI-Co, respectively. The highest biocatalytic activity at extremely acidic and basic pH (pH = 3 and 10) values were achieved for MCM-PEI-Co and MCM-PEI-Cu, respectively. Optimum enzymatic activity was observed for MCM-41@PEI-Co at 75 °C, while immobilized lipase on the Co-chelated support retained 70% of its initial activity after 14 days of storage at room temperature. Due to its efficient catalytic performance, MCM-41@PEI-Co was selected for the synthesis of ethyl valerate in the presence of valeric acid and ethanol. The enzymatic esterification yield for immobilized lipase onto MCM-41@PEI-Co was 60 and 53%, respectively, after 24 h of incubation in n-hexane and dimethyl sulfoxide media.

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Graphical Abstract Divalent metal chelated polyethylenimine coated MCM-41 (MCM-41@PEI-M) was used for immobilization of Thermomyces lanuginosa lipase catalyzing green apple flavor preparation

     

A one-pot multi-component reaction for the facile synthesis of some novel 2-aryl thiazolidinones bearing benzimidazole moiety using La(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>·6H<Subscript>2</Subscript>O as an efficient catalyst

A series of new derivatives of 3-benzimidazolyl-2-aryl thiazolidinones, 4a–j are synthesized via a rapid, one-pot, three-component reaction by using La(NO₃)₃·6H₂O as an efficient catalyst from the reaction of 2-aminobenzimidazole, aromatic aldehydes and thioglycolic acid in ethanol at room temperature. These new compounds were characterized by IR, ¹H, ¹³C NMR and mass spectroscopies. An inexpensive and available catalyst, short reaction time, easy workup, good to excellent yields and nontoxic solvent are the advantages of this reaction.     

The effect of electrospinning parameters on the compliance behavior of electrospun polyurethane tube for artificial common bile duct

The present research introduced a method to produce an artificial common bile duct using electrospinning technique. Also, the effect of electrospinning variables on the mechanical properties of produced prostheses is investigated. Using electrospinning of polyurethane nanofibres, cylindrical prostheses were produced on a rotating mandrel considering the different controllable factors such as the mandrel rotational speed, the applied voltage, and the flow rate of polymer solution. Taguchi method was used to investigate the effect of mentioned factors on the compliance of circular prostheses. MTT assay was performed to study the cytotoxicity of prostheses. The results of the signal-to-noise analysis showed that the mandrel rotational speed factor has the strongest effect on the compliance values. The flow rate was the second factor and it was followed by electrospinning voltage. In addition, the optimum conditions to reach the highest compliance value were determined. The results of MTT assay indicated no cytotoxic effects of prostheses on the cells. The compliance of optimum prosthesis was found close to the compliance value of a native common bile duct.     

Synthesis of cobalt-based magnetic nanocrystals from cobalt(II) heterocyclic amine complexes

Research on Chemical Intermediates - Cobalt nanocrystals with different morphologies and magnetic properties were prepared from three cobalt(II) heterocyclic amine precursors in alcoholic solution...     

On quantitative structure of small Ree groups

The main aim of this article is to study quantitative structure of small Ree Groups ²G₂(q). Here, we prove that small Ree groups are uniquely determined by their orders and the set of the number of elements of the same order.     

A facile ZrO<Subscript>2</Subscript> nanoparticles catalyzed synthesis of 2-amino-5-arylpyrimido[4,5-<Emphasis Type="Italic">b</Emphasis>]quinolinediones

In this investigation, an efficient and ecofriendly multicomponent reaction is described for the green synthesis of 2-amino-5-arylpyrimido[4,5-b]quinolinedione derivatives using ZrO₂ (NPs). In this protocol, the reaction of 2,6-diaminopyrimidin-4(1H)-one, arylaldehyde and 1,3-cyclohexanedione or 5,5-dimethyl-1,3-cyclohexanedione in the presence of ZrO₂ (NPs) in ethylene glycol at 120 °C produced the desired products in excellent yields (90–98 %) and short reaction times (8–60 min.). Use of recyclable catalyst, green solvent, easy workup and excellent yields are the notable features of this method.     

Synthesis of 14H-dibenzo xanthene derivatives using choline chloride/tin(II) chloride deep eutectic solvent and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/ƛ-carrageenan/Zn(II)

In this study, various xanthene derivatives have prepared efficiently through a simple method using choline chloride/tin(II) chloride (ChCl·2SnCl₂) deep eutectic solvent (DES), alone, or in the presence of Fe₃O₄/?-carrageenan/Zn(II) magnetic bionanocatalyst. In the employed procedure, 2-naphthol derivatives have mixed with aromatic or aliphatic aldehydes and the reactions have been completed in the presence of DES at 90 °C in 1.5 h. In addition, using DES/Fe₃O₄/?-carrageenan/Zn(II), the reaction time was reduced to 30 min. The employed DES has been recycled four times without important loss of its activity.     

A simple non-enzymatic strategy for adenosine triphosphate electrochemical aptasensor using silver nanoparticle-decorated graphene oxide

In this work, a sensitive electrochemical aptasensor for the detection of adenosine triphosphate (ATP) has been introduced. A simple and non-enzymatic signal amplification strategy is utilized using silver nanoparticle-decorated graphene oxide (AgNPs–GO) as a redox probe. The modified electrode surface was characterized by scanning electron microscopy, FTIR and UV–Vis spectroscopy, and electrochemical impedance spectroscopy. GO provides an excellent substrate for the presence of the large number of AgNPs, so the monitored oxidation signal of AgNPs has been amplified. ATP-specific DNA aptamer is split into two fragments (F₁ & F₂) in order to design a sandwich-type assay. For the construction of the sensor, the surface of a graphite screen-printed electrode is modified with electrodeposited gold nanoparticles followed by self-assembling a monolayer of 3-mercaptopropionic acid on the electrode surface. The first amino-labeled fragment, F₁, is immobilized on the modified electrode via carbodiimide chemistry. The synthesized AgNPs–GO interacts with F₁ via \(\pi{-}\pi\) stacking. In the presence of ATP, the second fragment of the aptamer, F₂, forms an associated complex with the immobilized F₁ and causes AgNPs–GO to leave the surface. Consequently, a remarkable decrease in the oxidation signal of the AgNPs is observed. The percentage of this decrease has been monitored as an analytical signal, which is proportional to ATP concentration, and delivers a linear response over the range of 10.0 (±0.6) to 850 (±5) nM with a detection limit of 5.0 (±0.2) nM.