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The British School: Caiman, Cannon, and Manton and their effect on carcinology in the English speaking world
Published in Frank Truesdale, History of Carcinology, 2020
Cannon believed that need leads to appearance of form or structure, and use leads to degrees of development. Like Caiman, he ascribed to a holistic view of nature, that organisms lived in total equilibrium with their environment. However, Cannon saw evolution as a kind of biological Le Chatelier’s Principle, i.e., biological systems adjusted to external changes in the environment so as to remain in equilibrium with them.
Buffers
Published in Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod, The Primary FRCA Structured Oral Examination Study Guide 1, 2017
Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod
The general equation for a buffer system is: Le Chatelier’s principle states that if H+ ions are added to the solution, the equilibrium shifts to the left, and the H+ ions are ‘neutralised’ by the conjugate base, minimising an increase in free [H+] and maintaining a constant pH. If a base is added, H+ and OH− react to form water, but more HA dissociates to maintain the [H+] constant, therefore the equation shifts to the right.By applying the Law of Mass Action, , the Henderson–Hasselbach equation can be derived and the (pKa) for a buffer system can be calculated: (where Ka is the dissociation constant of a buffer and pKa is the pH at which 50% of the buffer’s acid is dissociated).
Proteosynthesis vs. Proteolysis: How to Bias This Antagonism in Favor of Proteosynthesis
Published in Willi Kullmann, Enzymatic Peptide Synthesis, 1987
can also be used to influence the outcome of the peptide bond-forming step. According to Le Chatelier’s principle, a reaction will proceed in the direction in which heat is absorbed by the equilibrium reaction system. As a consequence, the endothermic — (ΔH°′syn > 0) — process of peptide bond formation15 will be enhanced with rising temperature. For example, the synthesis of protected dipeptides was observed to proceed exergonically — (ΔG°′syn < 0) — at temperatures above 60°C.16
Plasma-initiated graft polymerization of carbon nanoparticles as nano-based drug delivery systems
Published in Biofouling, 2022
Tianchi Liu, Christopher Stradford, Ashwin Ambi, Daniel Centeno, Jasmine Roca, Thomas Cattabiani, Thomas J. Drwiega, Clive Li, Christian Traba
During bacterial colonization of a surface and subsequent biofilm formation, metabolically active bacteria produce acidic substances, in addition to many other biological components including DNA, proteins, enzymes, and sugars [Reference??]. These substances are methodically released in order to help modify the biofilms’ surroundings in an attempt to facilitate an environment suitable for the infection. During this process, the micro-environment pH of the biofilm drops (Ilie et al. 2012). Consequently, this drop in pH may affect the interaction between the polymer brushes of the CNPs and the loaded MFRPEE. To test this, NBDDSs were exposed to PBS solutions at a range of pH and the release of MFRPEE from NBDDSs into the solution monitored. As expected, NBDDSs were stable in PBS solutions with physiologic pH. Under these conditions, minimal amounts (2%) of MFRPEE were released. However, when NBDDSs were placed into PBS solutions of pH of 6.0, 11% of MFRPEE were released into the supernatant after exposure for 60min. As the pH of the PBS solutions decreased, release of MFRPEE became more evident (Figure 9B). Within 60min in PBS solutions at pH 5, > 85% of the loaded MFRPEE was released into solution (Figure 9B). This pH-sensitive release mechanism can be explained by Le Chatelier’s principle. In order to neutralize the acidity of the solution, the QA monomer separates from the MFRPEE. As the MFRPEE becomes released, this then activates the marked anti-biofilm activity observed by NBDDSs.
Nicotine forms: why and how do they matter in nicotine delivery from electronic cigarettes?
Published in Expert Opinion on Drug Delivery, 2020
Vinit V Gholap, Leon Kosmider, Laleh Golshahi, Matthew S Halquist
Under the Dilution approach, El-Hellani et al. established a Liquid-Liquid Extraction method for calculating the free base nicotine yield in e-liquids [68]. A study carried out by Gholap et al. [65] and Duell et al. [66] have shown that Liquid-Liquid Extraction method suffers a drawback of inaccurate quantification of free base nicotine yield in e-liquids. The extraction method is not specific for nicotine and can be affected by flavoring chemicals in the e-liquids. Additionally, e-liquids diluted in water can be a mixture of weak acids or bases and according to Le Chatelier’s principle, after a single extraction of free base nicotine (Nic) in organic solvent, there can be a change in equilibrium between Nic and NicH+ before the second extraction. Thus, results obtained in Liquid-Liquid Extraction method can be overestimated [65].