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Macrocyclic Receptors Synthesis, History, Binding Mechanism: An Update on Current Status
Published in Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney, Macrocyclic Receptors for Environmental and Biosensing Applications, 2022
Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney
Cryptands were first introduced to the macrocyclic scientific community in the year 1969 by (Blanco-Gómez et al. 2020). These are cyclic (bicyclic and polycyclic) multidentate ligands used extensively for trapping metal ions (Bharadwaj 2017). Alternatively, cryptands are three-dimensional cyclic structures of crown ether derivatives. These three-dimensional structures bind guest species in a crypt (a stone chamber that holds a coffin) and hence the name is known as ‘cryptand’.
Carbon-Based Materials
Published in Ghenadii Korotcenkov, Handbook of Humidity Measurement, 2020
The functionalization of fullerenes also gives positive effects. For example, the sensitivity of fullerene sensors toward polar vapors (e.g., ethanol and water) was enhanced by >50-fold through the deposition of a metal–fullerene-hybrid film containing both C60 and aluminum due to a higher surface area and possibly metal-fullerene bonding (Grynko et al. 2009). UV exposure further enhanced the sensitivity of both pristine and C60-Al hybrid films through the introduction of reactive sites on the C60 surface (Grynko et al. 2009). The sensitivity of C60-based QCM and SAW sensors toward polar and non-polar vapors such as volatile organic alcohols, water vapors, aldehydes, and acids was enhanced by derivatizing the C60 with supramolecular host compounds such as crown ethers and cryptands (Shih et al. 2001; Lin and Shih 2003). The proposed mechanism of this sensitivity enhancement involved a combination of enhanced chelation by the cryptand/crown ether as well as enhanced reactivity of the C60 at the cryptand/crown ether binding site (Shih et al. 2001; Lin and Shih 2003). Another approach to generating supramolecular host compounds for vapor sensing with fullerenes involved liquid crystals (Dickert et al. 1997) where rigid linear (thermotropic liquid crystals) and globular (fullerenes) compounds formed a 1:1 stoichiometry sensing film, disturbing the close packing of both species and, thus, forming cavities and diffusion channels.
Sensor Systems for Label-Free Detection of Biomolecular Interactions: Quartz Crystal Microbalance (QCM) and Surface Plasmon Resonance (SPR)
Published in Yallup Kevin, Basiricò Laura, Iniewski Kris, Sensors for Diagnostics and Monitoring, 2018
Şükran Şeker, M. Taner Vurat, Arin Doğan, A. Eser Elçin, Y. Murat Elçin
QCM enzyme biosensors are typically used for the evaluation of the catalytic properties of enzymes by measuring the mass deposition of the product molecule, which is formed through the enzymatic conversion of the substrate molecules. For that, the quartz crystal is coated with a layer that has the ability to detect the product of the enzymatic reaction. For example, the ammonium ion, which is an end product of the catalytic hydrolysis of urea by urease, is detected by a fullerene–cryptand-coated quartz crystal [37]. Quartz crystal coated with a nanofibrous layer of poly(lactic-co-glycolic acid) (PLGA) containing saturated fullerene C60 is used for the detection of the gluconic acid, the oxidation product of β-D-glucose by glucose oxidase [24]. In some studies using similar methods to measure enzyme activity, the substrate is immobilized on the quartz crystal to investigate the kinetic behavior of enzymatic hydrolysis. The frequency and dissipation shifts caused by substrate hydrolysis at various temperatures and enzyme concentrations are determined during an enzymatic reaction [38, 39]. QCM is also used in enzyme immobilization studies to determine the influence of surface chemistry on enzyme adsorption. The immobilization of Candida antarctica B lipase on a gold electrode modified with either methyl- (hydrophobic) or hydroxyl-terminated (hydrophilic) SAM surfaces is monitored using QCM [40].
The influence of the bridgehead in Saalfrank-type cryptands: prediction of ion selectivity by quantum chemical calculations XII†
Published in Journal of Coordination Chemistry, 2020
Jelena Balović, Dušan Ćoćić, Ralph Puchta, Andreas Scheurer, Rudi van Eldik
These cryptands showed the unmatched selectivity for complexation of complementary sized alkali and alkaline earth metal cation guests [8c] with unprecedented thermodynamic and kinetic stabilities [13]. The high thermodynamic stability of metal-cryptate complexes arises predominately from the high degree of preorganization and low degree of solvation of cryptands, such that it is enthalpic by origin [14]. The ligand’s stringent selectivity preferences is often attributed to size complementarity considerations [15], but also other factors such as ligand flexibility and coordination preferences of guests are recognized to have an important influence [16].