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The Inducible System: Antigens
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
the concentrations of reactants (A + B) and products (C + D) change until a constant concentration of each is attained. At this point, the rate of product formation (the forward reaction) equals the rate of reactant formation (the reverse reaction). The result is called chemical equilibrium. There is no net change in the concentrations of the reactants at equilibrium unless product is removed. This equilibrium is, therefore, dynamic. If some product is removed, the forward reaction replaces it, reestablishing the equilibrium. The equilibrium point is a constant for any reaction.
Simple Receptor-Ligand Interactions
Published in John C. Matthews, Fundamentals of Receptor, Enzyme, and Transport Kinetics, 2017
Returning to the baseball analogy, if we have 1,000 pairs of throwers and catchers on a field and we start out with only the throwers having the balls, over a short time the number of glove-ball complexes will increase from zero to some number. As the catchers catch the balls they throw them back, and so forth. If we stop all action at any instant and count the number of balls in gloves we will find that, after an initial short period, this number will become nearly unchanging. This is the equivalent of chemical equilibrium.
Proteosynthesis vs. Proteolysis: How to Bias This Antagonism in Favor of Proteosynthesis
Published in Willi Kullmann, Enzymatic Peptide Synthesis, 1987
Besides the “manipulation” of ionic equilibria, there exist additional means to favor peptide synthesis at the expense of peptide hydrolysis. These aim at inducing a favorable shift of the chemical equilibria in protease-catalyzed reactions. All these expedients can be reduced formally to a single basic idea, that of energy coupling; a concept which is ubiquitous in living organisms. Thus, when synthesis of a peptide bond, for which
Central Corneal Edema with Scleral-Lens Wear
Published in Current Eye Research, 2018
Young Hyun Kim, Bo Tan, Meng C. Lin, Clayton J. Radke
Because of high water permeability and thin PoLTF and lens thicknesses, the influence of carbon dioxide on corneal edema is minimal for soft-contact-lens wear. However, with SL wear and larger PoLTF and lens thicknesses, the effect of carbon dioxide on corneal edema needs to be revisited. Upon comparing carbon-dioxide transmissibilities of 0 and 500 hBarrer/cm in Figure 5, we note a decline of 1% in corneal swelling. The reason for this decrease is that with higher lens carbon-dioxide transmissibility, more carbon dioxide exits the cornea. This exit shifts the chemical equilibrium in Eq. (5) toward carbon-dioxide production and reduces the concentration of bicarbonate ion in the cornea. Lower bicarbonate-ion concentration at the endothelial layer decreases the swelling pressure in Eq. (3) and, hence, reduces swelling. In this study, the contributions of lactate and bicarbonate ions to the endothelial pump and, subsequently, to edema are consistent with the in-vivo findings of Nguyen and Bonnano.44
Effect of matrix composition, sphere size and hormone concentration on diffusion coefficient of insulin for controlled gastrointestinal delivery for diabetes treatment
Published in Journal of Microencapsulation, 2018
Fernando Villaverde Cendon, Regina Maria Matos Jorge, Regina Weinschutz, Alvaro Luiz Mathias
WPI was also used as a protective matrix for the insulin. A solution containing 110 g L−1 WPI (BiPRO, Davisco, Eden Prairie, MN) was prepared using distilled water, under low agitation at ambient temperature for 60 min. The solution was kept at rest for 120 min in order to establish physical–chemical equilibrium. In order to irreversibly alter protein structures (>56 °C), the liquid underwent low agitation at 80 °C in a magnetic agitator for 40 min, resulting in a viscous, clouded brown solution composed of denatured protein (Lefevre and Subirade, 2000).
Measuring aggregates, self-association, and weak interactions in concentrated therapeutic antibody solutions
Published in mAbs, 2020
Sumit K. Chaturvedi, Arun Parupudi, Kristian Juul-Madsen, Ai Nguyen, Thomas Vorup-Jensen, Sonia Dragulin-Otto, Huaying Zhao, Reza Esfandiary, Peter Schuck
An important question is whether the detected faster-sedimenting states are stable aggregates, or species in slow or rapid self-association equilibrium. This can be addressed in a concentration series allowing samples to attain chemical equilibrium at different dilutions of stock solutions prior to the SV experiment. When studying samples across a large concentration range that spans ideal and strongly nonideal sedimentation behavior, it is useful to recognize that for IgG samples at low concentrations (below 0.5 mg/mL) nonideality is typically virtually absent and diffusion behavior can be measured well, whereas for high concentrations (above 10 mg/mL) diffusion information is obscured by dominant boundary self-sharpening originating from nonideality. Therefore, we applied a 3-step strategy. Initially, we carried out a conventional ideal c(s) analysis of the most diluted sample still with significant signal (e.g., at 0.3 mg/mL) to determine the average frictional ratio f/f0. Next, this was inserted and kept fixed as prior knowledge in the cNI(s0) analysis of the most concentrated sample (where diffusion is masked most by self-sharpening). This provides a good estimate of the nonideality of sedimentation kS, since the highest concentrations are maximally exhibiting nonideality. SV experiments do not carry as much information on kD as they do on kS, since nonideality of diffusion becomes a second-order effect when diffusion is largely masked. Therefore, in this step, we found the best strategy to achieve convergence to the best-fit model is to initially constrain kD (e.g., to a small value of log10(kD) = −3 or −2.5) while optimizing kS, followed by a release of the constraint on kD and optimizing both kS and kD. In rare cases we found it advantageous to release the constraint in f/f0, to allow for the effect that rapid chemical conversion of species on the time-scale of sedimentation can enhance boundary broadening in excess of solely diffusion-based estimates. Finally, since the scale of sedimentation coefficients (s0-values) returned in cNI(s0) depends chiefly on kS, it is important that this parameter is well defined. For this reason, in the analysis of the intermediate concentrations we fixed kS (and kD) to the value obtained in the analysis of the highest sample concentration, which reflects best the nonideality of the solution. For low concentrations, this parameter would not be well defined. If the highest sample concentration was below ~10 mg/mL, we found that kS may best be fixed to average expectation values for mAbs. This strategy allows for nonideality corrections to samples under close-to-ideal conditions.