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Histochemical Study of Estrogen Receptors in the Rat Uterus With a Hydrophilic Fluorescent Estradiol Conjugate
Published in Louis P. Pertschuk, Sin Hang Lee, Localization of Putative Steroid Receptors, 2019
There is a difference not only in concentration, but in physical characteristics between the receptors in the cell and the receptors in cytosol. Unlike those soluble in supernatant of a tissue homogenate, the receptor sites demonstrated histochemically are bound to cellular structures. The situation is reminiscent of an immobilized enzyme system. In comparative studies, it has been shown that because immobilized enzymes are less accessible to substrate and are subject to partitioning effects leading to a modified microenvironment in the domain of the immobilized enzyme particle, great differences are expected to exist between these fixed enzymes and the soluble enzymes, as reflected in the values of their kinetic parameters.37 Therefore, the kinetic parameters used to characterize the binding behavior of ER sites in tissue sections may well differ from those based on soluble receptor proteins.
Biocatalytic Nanoreactors for Medical Purposes
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Oscar González-Davis, Chauhan Kanchan, Rafael Vazquez-Duhalt
Klein et al. (2012) investigated the use of macro- and nanoparticles of chitosan for β-Gal immobilization. Their research evaluated the effect of the support size on the properties of the immobilized enzyme. They observed that different particle sizes and porosities modified the enzyme load, as well as the activity and thermal stability of the immobilized biocatalyst. Nonetheless, immobilized β-Gal exhibited excellent operational stability at 37°C. Although their focus was on the food industry, modifications could be made to accommodate this system for a therapeutic approach.
Short-Lived Positron Emitting Radionuclides
Published in Frank Helus, Lelio G. Colombetti, Radionuclides Production, 2019
As discussed before, an advantage of enzymatic methods is that very often the natural stereoisomers of the prepared compounds are obtained. A recent improvement in the preparation is the application of immobilized enzymes. Gelbard described the preparation of l-13N-glutamate by this technique. The procedure to immobilize the enzyme used, is included.260 Baumgartner developed a remote, semiautomated procedure not only for l-13N-glutamate but also for l-glutamine, labeled either in the α or ω positron.261 The semiautomated procedure for l-13N-alanine is reported earlier by the same group.262 Nitrogen-13 labeled l-glutamic acid is used as intermediate in the preparation of two aromatic amino acids. l-13N-tyrosine and l-13N-phenylalanine are prepared by transamination of the appropriate α-keto acid with glutamate oxalacetate transaminase isolated from a pig heart.263 The enzymatic synthesis of 13N-asparagine is described in an abstract by Majumdar.134 A new nonenzymatic preparation is reported by Elmaleh.264 The β-carboxylic group of the protected l-aspartic acid is activated with N-hydroxysuccinimide. This intermediate compound is refluxed with 13N-ammonia, hydrolyzed and after chromatography l-13N-asparagine is obtained in good yields.
Bioconjugation as a smart immobilization approach for α-amylase enzyme using stimuli-responsive Eudragit-L100 polymer: a robust biocatalyst for applications in pharmaceutical industry
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Heidi Mohamed Abdel-Mageed, Rasha Ali Radwan, Nermeen Zakaria AbuelEzz, Hebatallah Ahmed Nasser, Aliaa Ali El Shamy, Rana M. Abdelnaby, Nesrine Abdelrehim EL Gohary
Enzymes are biodegradable biocatalysts that catalyze selective reactions under mild operating conditions. They are cost efficient with the ability to reduce environmental impact unlike conventional chemical processes and they do not produce undesirable waste [4]. However, the industrial applications of enzymes are immensely hindered by high production cost and the inherently sensitive nature of enzymes that compromise their storage shelf life and stability under operational conditions. In addition, enzymes are typically wasted after completion of the catalytic process. Though, regarding their catalytic nature, they still retain their enzymatic activity at the end of the reaction [4,5]. Immobilization is an age-old method of biocatalyst stabilization. Immobilization is a physical or a chemical process in which enzymes are fixed to or confined to a support, creating a heterogeneous immobilized enzyme system that mimics the enzyme natural mode in living cells. Immobilization allows the recovery of enzymes for re-use as biocatalyst which is highly advantageous for industrial applications [4,5]. The choice of the appropriate immobilization support and the efficient immobilization method is fundamental for effective industrial applications of immobilized enzymes [5,6]. In instances where the enzyme has to act on macromolecular substrates (heterogeneous media) it is highly important that the support does not represent a constraint to enzymatic reaction [7].
Mycotoxin patulin in food matrices: occurrence and its biological degradation strategies
Published in Drug Metabolism Reviews, 2019
Marina Sajid, Sajid Mehmood, Yahong Yuan, Tianli Yue
Enzymes have developed the possible potential to decrease mycotoxin levels and its toxic effects in food matrices which emphasize their use in the future for the detoxification of mycotoxins (He and Zhou 2010). Immobilized enzymes show numerous benefits over the free one, including enhanced stability, ease of separation from the reaction mixture, significant savings in enzyme consumption, and usually improved activity (Li et al. 2017). Porcine pancreatic lipase (PPL) has been studied for the detoxification of mycotoxin patulin in aqueous solution. PPL has the ability to reduce the patulin >90% at pH 7.0, 40°C for 48 h. It showed that PPL could be effective for the degradation of patulin in fruits and vegetable juices (Liu et al. 2018). Moreover, biodegradation of patulin from apple juice using an immobilized enzyme PPL was studied by Tang et al. (2018). The results showed >70% patulin detoxification rate without any change in the number of amino acids, aroma components, and polyphenols in apple juice.
Recent approaches to ameliorate selectivity and sensitivity of enzyme based cholesterol biosensors: a review
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Anjum Gahlaut, Vinita Hooda, Vikas Dhull, Vikas Hooda
Immobilized enzymes are the enzymes physically confined or localized in a certain defined region of space without altering their catalytic activities, so that they can be used repeatedly and continuously. Immobilized enzymes are used in organic synthesis to fully exploit the technical and economical benefits of biocatalysts based on isolated enzymes. It will increase the enzyme specificity (kcat/Km) and reduce product inhibition [21]. Operational stability of enzyme also increases on immobilization. The concept of stabilization has been an important driving force for immobilizing enzymes [22]. Immobilization of enzyme on the surface of electrode provides reusability as well as cut the cost of enzyme preparation. Mode of enzyme immobilization is most critical step which decides the level of sensitivity and stability of biosensor [23]. Enzyme can be immobilized on different supports in different ways.