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Some Underlying Physical Principles
Published in Clive R. Bagshaw, Biomolecular Kinetics, 2017
This equation applies when the change in length, Δx, is independent of force (i.e., the states have the same stiffness). For more complex cases, see Howard [75]. A change in the equilibrium distribution of the A and B conformers requires that at least one of the rate constants change. From transition-state theory:
Molecular Aspects of the Activity and Inhibition of the FAD-Containing Monoamine Oxidases
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2019
Insight into the mechanism has come from transition state theory using multiscale simulations to calculate the free energy barriers for the catalytic step in the oxidation of amines by MAO (reviewed in Vianello et al. (2016)). The lower the free energy barriers between substrate, transition state intermediate, and product, the faster the reaction. The highest resolution structure of MAO B was optimized, fitted to the electrostatic potential, and the solvent reaction field included, then EVB calculations applied to the oxidation of a substrate such as dopamine by lumiflavin in the gas phase compared to the reaction in the enzyme. The work revealed that dopamine is stripped of its proton (pKa 8.3) for the catalytic reaction that requires the neutral amine before oxidation via a two-step hydride transfer in which H− (one proton and two electrons) is transferred to the N5 of the flavin and the other H+ is removed from the substrate nitrogen and transferred via a water relay to N1 of the flavin to yield the neutral product required for dissociation. The calculated energy for the reaction was 16.1 kcal/mol in good agreement with the experimentally determined 16.5 kcal/mol. The method not only provides insight into the mechanism but also provides information relevant to design of the propargylamine inactivators of MAO. As described above, these mechanism-based inhibitors are first oxidized as substrates generating a positively charged product that could be retained close to the reduced flavin by electrostatic attraction and by favourable cation-π interactions in the active site “aromatic cage”, where it can react with the reduced flavin to form a covalent adduct (Albreht et al., 2018).
Adsorption and sensing of an anticancer drug on the boron nitride nanocones; a computational inspection
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Chao Wang, Lizhen Shen, Liang Wu
The work function of 5FU drug adsorbed on pristine BNNCs decreases to 4.58 eV to 3.71 eV. Reduce the work function value of BNNCs after 5FU drug adsorption which express that the electrons are restricted not more tightly to the BNNCs. Owing to the Richardson Dushman equation (Eq.7), there is a relationship between the Φ value and the current densities of the electron, hence the Fermi level changes as a function of Φ variation, which is related to the changes in the field emission (Richardson 1924): 2), and T is the absolute temperature (K). Correspondingly, the electron current density released from the BNNCs surface has a significantly change and the neocons can be regarded as a 5FU adsorption Φ-type sensor. Since fast desorption is a requirement for a suitable sensor, too strong chemical interactions are not ideal for sensors. Technically speaking, intense adsorption often leads to long recovery periods which are not ideal for sensor applications. According to the current transition state theory, longer recovery time is needed in strong adsorption as follows (Hadipour et al. 2015): 0 is the applied frequency. Using ultraviolet light (ν ∼1012s−1) in vacuum to extract the 5FU drug attached to BNNCs, the recovery time at ambient temperature will be nearly 4.25 ms. It is noteworthy that in higher temperatures this period can be reduced. BNNCs has a relatively fast recovery period and is ideal for sensing 5FU species.
Biointerface: a nano-modulated way for biological transportation
Published in Journal of Drug Targeting, 2020
Pravin Shende, Varun S. Wakade
The molecular theory postulated by Arrhenius demonstrates that the molecules with less energy react and the energy required is referred to as the energy of activation [25]. Drug release from nanocarriers plays a vital role in the determination of biological effect with kinetic profile [26]. In vitro and in vivo kinetic profiles study the impact of the drug on the gastrointestinal tract. Drug release studies are performed using various equations like Nernst–Brunner, Korsmeyer–Peppas [25], Hixon–Crowell and Hopfenberg. The fundamental factors show alterations in Noyes–Whitney, Nernst–Brunner and Levich equation. Furthermore, factors like diffusivity and solubility of drug and polymer within the gastrointestinal (GI) contents cause drug or polymer to swell when it comes in contact with sodium thiopental fluids, which is explained by GI fluid mechanics [26]. The theory of Arrhenius with nanotechnology demonstrates a change from delayed pattern to targeted drug release in addition to kinetics models [25]. Bronsted theory forms the basis of transition state theory and consists of two charged particles with the reversible formation of transition state where charge number is equal to the number of electronic species that indicates the rate-determining step [27]. Interfacial equilibrium causes a total change in charge of a doublet state that affects the rate of reaction proportional to the concentration of transition state. The overall rate constant is based on the strength of medium for co-efficient of activity from the Debye–Huckel rule. Arrhenius theory implements various laws and sub-theories such as the Gouy–Chapman theory stating the distribution of ions from ‘d’ plane (diffuse layer onset) [8]. This theory is stated as a double layer to improve the diffusion of a molecule inside the cell by forming alternate positive and negative charge layers. The diffusion process decreases the potential difference of cell membranes but increases in the biointerface of adhering nanoparticles to the cell surface. This adherence prevents electrostatic repulsion between the nanocarrier and cell surface for diffusion phenomenon which is explained by Smoluchowski’s theory [28]. Hogg–Healy–Fuerstenau’s theory explains the approaches based on the Coulombs interaction between two nanoparticles [29]. Two nanocarriers encapsulating the drug show the same surface potential and energy which is expressed in molar units. Furthermore, the surface complex model shows surfaces of metal oxides undergoing hydration, protonation and deprotonation for amphoteric compounds from the ‘d’ plane and distribution of ions depends on the Hogg–Healy–Fuerstenau theory [30]. The surface potential relation of electrical bilayer states the basis of constant capacitance concept (not depending on electromotive force and charges at the plates). In addition to the surface complex, the model measures the number of colloid particle charges at given conditions of temperature, pH and lipophilicity of cell-membrane to show capacitance [30], surface reactions and total density. The Bronsted theory demonstrates the stability of electrolyte in a nano-dispersion form in extracellular matrix but it decreases the stability of the cell.