The immobilization of enzymes using protein coated micro-crystals (PCMCs) was reported for the first time in 2001 by Kreiner and coworkers. The strategy is very simple. First, an enzyme solution must ...be prepared in a concentrated solution of one compound (salt, sugar, amino acid) very soluble in water and poorly soluble in a water-soluble solvent. Then, the enzyme solution is added dropwise to the water soluble solvent under rapid stirring. The components accompanying the enzyme are called the crystal growing agents, the solvent being the dehydrating agent. This strategy permits the rapid dehydration of the enzyme solution drops, resulting in a crystallization of the crystal formation agent, and the enzyme is deposited on this crystal surface. The reaction medium where these biocatalysts can be used is marked by the solubility of the PCMC components, and usually these biocatalysts may be employed in water soluble organic solvents with a maximum of 20% water. The evolution of these PCMC was to chemically crosslink them and further improve their stabilities. Moreover, the PCMC strategy has been used to coimmobilize enzymes or enzymes and cofactors. The immobilization may permit the use of buffers as crystal growth agents, enabling control of the reaction pH in the enzyme environments. Usually, the PCMC biocatalysts are very stable and more active than other biocatalysts of the same enzyme. However, this simple (at least at laboratory scale) immobilization strategy is underutilized even when the publications using it systematically presented a better performance of them in organic solvents than that of many other immobilized biocatalysts. In fact, many possibilities and studies using this technique are lacking. This review tried to outline the possibilities of this useful immobilization strategy.
Introduction: Alzheimer's disease (AD), the most common type of dementia among older adults, is a chronic neurodegenerative pathology that causes a progressive loss of cognitive functioning with a ...decline of rational skills. It is well known that AD is multifactorial, so there are many different pharmacological targets that can be pursued.
Areas covered: The authors highlight the strategic value of privileged scaffolds in a multi-target lead compound generation against AD, exploring the concept of multi-target design, with a special emphasis on hybrid compounds. Hence, the most promising building blocks for designing and synthesizing hybrid anti-AD drugs are shown, while also presenting the more advanced hybrid compounds.
Expert opinion: The available therapeutic arsenal for AD, designed under the traditional paradigm of 'one-drug/one target/one-disease', is based on the inhibition of brain acetylcholinesterase (AChE) to increase acetylcholine (ACh) levels. However, this classical approach has not been sufficiently effective when used to treat any multifactor-depending pathology (cancer, diabetes or AD). The multi-target drug concept has been quickly adopted by medicinal chemists. The basic research developments reported in recent years are a solid foundation that will pave the way for the construction of future AD therapeutics.
The intrinsic degradative α-elimination of Li carbenoids somehow complicates their use in synthesis as C1-synthons. Nevertheless, we herein report how boosting such an α-elimination is a ...straightforward strategy for accomplishing controlled ring-opening of epoxides to furnish the corresponding β-halohydrins. Crucial for the development of the method is the use of the eco-friendly solvent 2-MeTHF, which forces the degradation of the incipient monohalolithium, due to the very limited stabilizing effect of this solvent on the chemical integrity of the carbenoid. With this approach, high yields of the targeted compounds are consistently obtained under very high regiocontrol and, despite the basic nature of the reagents, no racemization of enantiopure materials is observed.
Brain-derived neurotrophic factor (BDNF) regulates dendritic branching and dendritic spine morphology, as well as synaptic plasticity and long-term potentiation. Consequently, BDNF deficiency has ...been associated with some neurological disorders such as Alzheimer's, Parkinson's or Huntington's diseases. In contrast, elevated BDNF levels correlate with recovery after traumatic central nervous system (CNS) injuries. The utility of BDNF as a therapeutic agent is limited by its short half-life in a pathological microenvironment and its low efficacy caused by unwanted consumption of non-neuronal cells or inappropriate dosing. Here, we tested the activity of chitosan microsphere-encapsulated BDNF to prevent clearance and prolong the efficacy of this neurotrophin. Neuritic growth activity of BDNF release from chitosan microspheres was observed in the PC12 rat pheochromocytoma cell line, which is dependent on neurotrophins to differentiate via the neurotrophin receptor (NTR). We obtained a rapid and sustained increase in neuritic out-growth of cells treated with BDNF-loaded chitosan microspheres over control cells (
< 0.001). The average of neuritic out-growth velocity was three times higher in the BDNF-loaded chitosan microspheres than in the free BDNF. We conclude that the slow release of BDNF from chitosan microspheres enhances signaling through NTR and promotes axonal growth in neurons, which could constitute an important therapeutic agent in neurodegenerative diseases and CNS lesions.
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•Lipase A from Candida antarctica potential is here reviewed.•The production of the enzyme has been discussed.•Enzyme improvement via different genetic tolls is ...presented.•Immobilization of the enzyme using different strategies is discussed.
This review intends to present some of the latest studies on the lipase A from Candida antarctica (CALA). This lipase is among the most stable ones and has some capability to attack the sn-2 position of triglycerides. This makes it a very interesting lipase, especially considering that it is commercially available. The cloning and production of the enzyme together with some structural facts and applications will be discussed in this review. Special focus will be put on the immobilization of the enzyme. The use of the commercially available crosslinked enzyme aggregates of this enzyme will be explained, together with the use of the enzyme in some new trends in enzyme immobilization, such as bio-imprinting of the open form of CALA by detergents and the fixation of the open structure, the design of heterofunctional supports able to take full advantage of the immobilization via interfacial activation but preventing enzyme release, or the design of strategies for the preparation of multiple layers of lipase enzymes (using just CALA or combining CALA with other lipases).
Lipase from Thermomyces lanuginosus (TLL) has been immobilized on a methacrylate macroporous resin coated with octadecyl groups (Purolite Lifetech®® ECR8806F). This immobilization protocol gave a ...biocatalyst with significantly higher stability than that obtained using octyl agarose. To further improve the biocatalyst features, we tried to covalently immobilize the enzyme using this support. For this purpose, the support was activated with divinyl sulfone. The results showed that at least 1/3 of the immobilized enzyme molecules were not covalently immobilized. To solve the problem, we produced an aminated support and then activated it with divinyl sulfone. This permitted the full covalent immobilization of the previously immobilized TLL. The use of different blocking agents as the reaction endpoint (using ethylenediamine, Asp, Gly, and Cys) greatly altered the biocatalyst functional features (activity, specificity, or stability). For example, the blocking with ethylenediamine increased the ratio of the activity versus R- and S-methyl mandelate by a three-fold factor. The blocking with Cys produced the most stable biocatalyst, maintaining close to 90% of the activity under conditions where the just adsorbed enzyme maintained less than 55%. That way, this strategy to modify the support has permitted obtaining an enzyme interfacially activated versus the octadecyl layer and, later, covalently immobilized by reaction with the vinyl sulfone groups.
2‐Methyl‐tetrahydrofuran (2‐MeTHF) can be derived from renewable resources (e.g., furfural or levulinic acid) and is a promising alternative solvent in the search for environmentally benign synthesis ...strategies. Its physical and chemical properties, such as its low miscibility with water, boiling point, remarkable stability compared to other cyclic‐based solvents such as THF, and others make it appealing for applications in syntheses involving organometallics, organocatalysis, and biotransformations or for processing lignocellulosic materials. Interestingly, a significant number of industries have also started to assess 2‐MeTHF in several synthetic procedures, often with excellent results and prospects. Likewise, preliminary toxicology assessments suggest that the use of 2‐MeTHF might even be extended to more processes in pharmaceutical chemistry. This Minireview describes the properties of 2‐MeTHF, the state‐of‐the‐art of its use in synthesis, and covers several outstanding examples of its application from both industry and academia.
The choice of a new generation: 2‐Methyltetrahydrofuran (2‐MeTHF) is a biomass‐derived chemical that finds widespread use as alternative (co)solvent for organic reactions, both in industry and academia. 2‐MeTHF has applications in organometallics, organocatalysis, biotransformations, and biomass processing. This Minireview describes current applications of 2‐MeTHF, and gives a prognosis for future uses.
In this paper, we describe the effectiveness of the combination between an organic solvent system mixture with orthoformates with different chain sizes from one to four carbon atoms. These ...orthoesters have been used as a “water trapper/alcohol releaser molecule” to reach a notable improvement in enantioselectivity and enantiomeric excess of our target compound, (S)-2-(4-isobutylphenyl)propanoic acid (ibuprofen eutomer), during the enzymatic kinetic resolution of rac-ibuprofen using immobilized lipase B of Candida antarctica as a biocatalyst. At the same time, one of the great problems of biocatalysis in organic media has been solved by eliminating excess water in the medium that allows the reversibility of the reaction. Following the optimization of the reaction conditions, an increase in enantiomeric excess and enantioselectivity was reached by using these acyl donors in the presence of a cosolvent.
l‐Theanine (l‐Th) was synthesized by simply mixing the reactants (l‐glutamine and ethylamine in water) at 25 °C and Bacillus subtilis γ‐glutamyl transferase (BsGGT) covalently immobilized on ...glyoxyl‐agarose according to a methodology previously reported by our research group; neither buffers, nor other additives were needed. Ratio of l‐glutamine (donor) to ethylamine (acceptor), pH, enzymatic units (IU), and reaction time were optimized (molar ratio of donor/acceptor=1 : 8, pH 11.6, 1 IU mL−1, 6 h), furnishing l‐Th in 93 % isolated yield (485 mg, 32.3 g L−1) and high purity (99 %), after a simple filtration of the immobilized biocatalyst, distillation of the volatiles (unreacted ethylamine) and direct lyophilization. Immobilized BsGGT was re‐used (four reaction cycles) with 100 % activity retention. This enzymatic synthesis represents a straightforward, fast, high‐yielding, and easily scalable approach to l‐Th preparation, besides having a favorable green chemistry metrics.
Making green t(h)ea greener: The sustainable synthesis of l‐theanine is achieved by simply mixing l‐glutamine and ethylamine in water with the immobilized γ‐glutamyl transferase from Bacillus subtilis, and stirring for 6 h. The product is obtained with a yield of 93 % and purity of 99 %. The biocatalyst can be recovered and reused for the next run.
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