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International Journal of Molecular... Aug 2019Carbonic anhydrases (CAs) catalyze a reaction fundamental for life: the bidirectional conversion of carbon dioxide (CO) and water (HO) into bicarbonate (HCO) and protons... (Review)
Review
Carbonic anhydrases (CAs) catalyze a reaction fundamental for life: the bidirectional conversion of carbon dioxide (CO) and water (HO) into bicarbonate (HCO) and protons (H). These enzymes impact numerous physiological processes that occur within and across the many compartments in the body. Within compartments, CAs promote rapid H buffering and thus the stability of pH-sensitive processes. Between compartments, CAs promote movements of H, CO, HCO, and related species. This traffic is central to respiration, digestion, and whole-body/cellular pH regulation. Here, we focus on the role of mathematical modeling in understanding how CA enhances buffering as well as gradients that drive fluxes of CO and other solutes (facilitated diffusion). We also examine urinary acid secretion and the carriage of CO by the respiratory system. We propose that the broad physiological impact of CAs stem from three fundamental actions: promoting H buffering, enhancing H exchange between buffer systems, and facilitating diffusion. Mathematical modeling can be a powerful tool for: (1) clarifying the complex interdependencies among reaction, diffusion, and protein-mediated components of physiological processes; (2) formulating hypotheses and making predictions to be tested in wet-lab experiments; and (3) inferring data that are impossible to measure.
Topics: Animals; Buffers; Carbon Dioxide; Carbonic Anhydrase Inhibitors; Carbonic Anhydrases; Diffusion; Dose-Response Relationship, Drug; Enzyme Activation; Humans; Hydrogen-Ion Concentration; Membranes, Artificial; Metabolic Networks and Pathways; Models, Biological; Models, Theoretical; Respiratory Physiological Phenomena
PubMed: 31390837
DOI: 10.3390/ijms20153841 -
Journal of Biomechanics Aug 2017A buffer solution is often used to maintain tissue hydration during mechanical testing. The most commonly used buffer solution is a physiological concentration of...
A buffer solution is often used to maintain tissue hydration during mechanical testing. The most commonly used buffer solution is a physiological concentration of phosphate buffered saline (PBS); however, PBS increases the tissue's water content and decreases its tensile stiffness. In addition, solutes from the buffer can diffuse into the tissue and interact with its structure and mechanics. These bathing solution effects can confound the outcome and interpretation of mechanical tests. Potential bathing solution artifacts, including solute diffusion, and their effect on mechanical properties, are not well understood. The objective of this study was to measure the effects of long-term exposure of rat tail tendon fascicles to several concentrations (0.9-25%) of NaCl, sucrose, polyethylene glycol (PEG), and SPEG (NaCl+PEG) solutions on water content, solute diffusion, and mechanical properties. We found that with an increase in solute concentration the apparent water content decreased for all solution types. Solutes diffused into the tissue for NaCl and sucrose, however, no solute diffusion was observed for PEG or SPEG. The mechanical properties changed for both NaCl solutions, in particular after long-term (8h) incubation the modulus and equilibrium stress decreased compared to short-term (15min) for 25% NaCl, and the cross sectional area increased for 0.9% NaCl. However, the mechanical properties were unchanged for both PEG and SPEG except for minor alterations in stress relaxation parameters. This study shows that NaCl and sucrose buffer solutions are not suitable for long-term mechanical tests. We therefore propose using PEG or SPEG as alternative buffer solutions that after long-term incubation can maintain tissue hydration without solute diffusion and produce a consistent mechanical response.
Topics: Animals; Biomechanical Phenomena; Buffers; Dose-Response Relationship, Drug; Mechanical Phenomena; Polyethylene Glycols; Rats; Sodium Chloride; Solutions; Tendons; Water
PubMed: 28720201
DOI: 10.1016/j.jbiomech.2017.06.045 -
Kidney International. Supplement Dec 2003Buffer transport in peritoneal dialysis. The success of peritoneal dialysis as a robust modality of renal replacement therapy has invited a quest for ameliorations in... (Review)
Review
Buffer transport in peritoneal dialysis. The success of peritoneal dialysis as a robust modality of renal replacement therapy has invited a quest for ameliorations in its underlying technology aimed at enhancing patient satisfaction and preserving the central instrument of the therapy, namely the peritoneal membrane. The health and longevity of the membrane have motivated and continue to drive a series of iterative innovations in the composition, methods of production, and delivery of dialysis solutions. It is the purpose of this article to review aspects of these innovations pertaining to buffer composition in dialysis solutions and the peritoneal mechanisms of buffer transport.
Topics: Biological Transport; Buffers; Dialysis Solutions; Humans; Peritoneal Dialysis
PubMed: 14870876
DOI: 10.1046/j.1523-1755.2003.08804.x -
Scientific Reports Feb 2020Electroporation is an electro-physical, non-viral approach to perform DNA, RNA, and protein transfections of cells. Upon application of an electric field, the cell...
Electroporation is an electro-physical, non-viral approach to perform DNA, RNA, and protein transfections of cells. Upon application of an electric field, the cell membrane is compromised, allowing the delivery of exogenous materials into cells. Cell viability and electro-transfection efficiency (eTE) are dependent on various experimental factors, including pulse waveform, vector concentration, cell type/density, and electroporation buffer properties. In this work, the effects of buffer composition on cell viability and eTE were systematically explored for plasmid DNA encoding green fluorescent protein following electroporation of 3T3 fibroblasts. A HEPES-based buffer was used in conjunction with various salts and sugars to modulate conductivity and osmolality, respectively. Pulse applications were chosen to maintain constant applied electrical energy (J) or total charge flux (C/m). The energy of the pulse application primarily dictated cell viability, with Mg-based buffers expanding the reversible electroporation range. The enhancement of viability with Mg-based buffers led to the hypothesis that this enhancement is due to ATPase activation via re-establishing ionic homeostasis. We show preliminary evidence for this mechanism by demonstrating that the enhanced viability is eliminated by introducing lidocaine, an ATPase inhibitor. However, Mg also hinders eTE compared to K-based buffers. Collectively, the results demonstrate that the rational selection of pulsing conditions and buffer compositions are critical for the design of electroporation protocols to maximize viability and eTE.
Topics: Adenosine Triphosphatases; Animals; Buffers; Cell Survival; Electricity; Electroporation; Magnesium; Mice; NIH 3T3 Cells; Transfection
PubMed: 32080269
DOI: 10.1038/s41598-020-59790-x -
Journal of the American Society For... Mar 2013A dual-channel electrospray microchip has been developed for electrospray ionization mass spectrometry (ESI-MS) where aqueous samples are mixed at the Taylor cone with...
A dual-channel electrospray microchip has been developed for electrospray ionization mass spectrometry (ESI-MS) where aqueous samples are mixed at the Taylor cone with an organic buffer. Due to the fast and effective mixing in the Taylor cone, the aqueous sample can be well ionized with a high ion intensity. The influence of geometric parameters such as the distance between the two microchannels at their junction at the tip of the emitter has been investigated together with chemical parameters such as the organic buffer composition.
Topics: Buffers; Equipment Design; Microarray Analysis; Peptides; Solutions; Spectrometry, Mass, Electrospray Ionization; Water
PubMed: 23385957
DOI: 10.1007/s13361-012-0547-z -
PloS One 2017Functional studies on isolated mitochondria critically rely on the right choice of respiration buffer. Differences in buffer composition can lead to dramatically...
Functional studies on isolated mitochondria critically rely on the right choice of respiration buffer. Differences in buffer composition can lead to dramatically different respiration rates leading to difficulties in comparing prior studies. The ideal buffer facilities high ADP-stimulated respiratory rates and minimizes substrate transport effects so that the ability to distinguish between various treatments and conditions is maximal. In this study, we analyzed a variety of respiration buffers and substrate combinations to determine the optimal conditions to support mitochondrial function through ADP-stimulated respiration and uncoupled respiration using FCCP. The buffers consisted of a standard KCl based buffer (B1) and three modified buffers with chloride replaced by the K-lactobionate, sucrose, and the antioxidant taurine (B2) or K-gluconate (B3). The fourth buffer (B4) was identical to B2 except that K-lactobionate was replaced with K-gluconate. The substrate combinations consisted of metabolites that utilize different pathways of mitochondrial metabolism. To test mitochondrial function, we used isolated cardiac guinea pig mitochondria and measured oxygen consumption for three respiratory states using an Oroboros Oxygraph-2k. These states were the leak state (energized mitochondria in the absence of adenylates), ADP-stimulated state (energized mitochondria in the presence of saturating ADP concentrations), and uncoupled state (energized mitochondria in the presence of FCCP). On average across all substrate combinations, buffers B2, B3, and B4 had an increase of 16%, 26%, and 35% for the leak state, ADP-simulated state, and uncoupled state, respectively, relative to rates using B1. The common feature distinguishing these buffers from B1 is the notable lack of high chloride concentrations. Based on the respiratory rate metrics obtained with the substrate combinations, we conclude that the adenine nucleotide translocase, the dicarboxylate carrier, and the alpha-ketoglutarate exchanger are partially inhibited by chloride. Therefore, when the goal is to maximize ADP-stimulated respiration, buffers containing K-lactobionate or K-gluconate are superior choices compared to the standard KCl-based buffers.
Topics: Animals; Buffers; Cell Respiration; Guinea Pigs; Mitochondria, Heart
PubMed: 29091971
DOI: 10.1371/journal.pone.0187523 -
Biological & Pharmaceutical Bulletin 2014The protein size, electrical interaction, and conformational stability of etanercept (marketed as Enbrel®) were examined by thermodynamic and light scattering methods...
The protein size, electrical interaction, and conformational stability of etanercept (marketed as Enbrel®) were examined by thermodynamic and light scattering methods with changing pH and buffer concentration. As pH of etanercept increased from pH 6.6 to 8.6, electrical repulsion in the solution increased, inducing a decrease in protein size. However, the size changed less in high buffer concentration and irreversible aggregation issues were not observed; in contrast, aggregates of about 1000 nm were observed in low buffer concentration at the pH range. Three significant unfolding transitions (Tm) were observed by differential scanning calorimetry (DSC). Unlikely to Tm1, Tm2 and Tm3 were increased as the pH increased. Higher Tm at high buffer concentration was observed, indicating increased conformational stability. The apparent activation energy of unfolding was further investigated since continuous increase of Tm2 and Tm3 was not sufficient to determine optimal conditions. A higher energy barrier was calculated at Tm2 than at Tm3. In addition, the energy barriers were the highest at pH from 7.4 to 7.8 where higher Tm1 was also observed. Therefore, the conformational stability of protein solution significantly changed with pH dependent steric repulsion of neighboring protein molecules. An optimized pH range was obtained that satisfied the stability of all three domains. Electrostatic circumstances and structural interactions resulted in irreversible aggregation at low buffer concentrations and were suppressed by increasing the concentration. Therefore, increased buffer concentration is recommended during protein formulation development, even in the earlier stages of investigation, to avoid protein instability issues.
Topics: Buffers; Calorimetry, Differential Scanning; Drug Stability; Etanercept; Hydrogen-Ion Concentration; Immunoglobulin G; Particle Size; Protein Aggregates; Protein Conformation; Receptors, Tumor Necrosis Factor; Surface Properties; Thermodynamics; Transition Temperature
PubMed: 24790003
DOI: 10.1248/bpb.b13-00926 -
Molecular Pharmaceutics Oct 2020Dissolution is a crucial process for the oral delivery of drug products. Before being absorbed through epithelial cell membranes to reach the systemic circulation, drugs...
Hierarchical Mass Transfer Analysis of Drug Particle Dissolution, Highlighting the Hydrodynamics, pH, Particle Size, and Buffer Effects for the Dissolution of Ionizable and Nonionizable Drugs in a Compendial Dissolution Vessel.
Dissolution is a crucial process for the oral delivery of drug products. Before being absorbed through epithelial cell membranes to reach the systemic circulation, drugs must first dissolve in the human gastrointestinal (GI) tract. and dissolutions are complex because of their dependency upon the drug physicochemical properties, drug product, and GI physiological properties. However, an understanding of this process is critical for the development of robust drug products. To enhance our understanding of and dissolutions, a hierarchical mass transfer (HMT) model was developed that considers the drug properties, GI fluid properties, and fluid hydrodynamics. The key drug properties include intrinsic solubility, acid/base character, p, particle size, and particle polydispersity. The GI fluid properties include bulk pH, buffer species concentration, fluid shear rate, and fluid convection. To corroborate the model, dissolution experiments were conducted in the United States Pharmacopeia (USP) 2 dissolution apparatus. A weakly acidic (ibuprofen), a weakly basic (haloperidol), and a nonionizable (felodipine) drug were used to study the effects of the acid/base character, p, and intrinsic solubility on dissolution. 900 mL of 5 mM bicarbonate and phosphate buffers at pH 6.5 and 37 °C was used to study the impact of the buffer species on drug dissolution. To investigate the impacts of fluid shear rate and convection, the apparatus was operated at different impeller rotational speeds. Moreover, presieved ibuprofen particles with different average diameters were used to investigate the effect of particle size on drug dissolution. experiments demonstrate that the dissolution rates of both the ionizable compounds used in this study were slower in bicarbonate buffer than in phosphate buffer, with the same buffer concentration, because of the lower interfacial buffer capacity, a unique behavior of bicarbonate buffer. Therefore, using surrogates (i.e., 50 mM phosphate) for bicarbonate buffer for biorelevant dissolution testing may overestimate the dissolution rate for ionizable drugs. Model simulations demonstrated that, assuming a monodisperse particle size when modeling, dissolution may overestimate the dissolution rate for polydisperse particle size distributions. The hydrodynamic parameters (maximum shear rate and fluid velocity) under conditions in the USP 2 apparatus under different rotational speeds are orders of magnitude higher compared to the situation. The inconsistencies between the and drug dissolution hydrodynamic conditions may cause an overestimation of the dissolution rate under conditions. The dissolution data supported the accuracy of the HMT for drug dissolution. This is the first drug dissolution model that incorporates the effect of the bulk pH and buffer concentration on the interfacial drug particle solubility of ionizable compounds, combined with the medium hydrodynamics effect (diffusion, convection, shear, and confinement components), and drug particle size distribution.
Topics: Buffers; Cheminformatics; Chemistry, Pharmaceutical; Diffusion; Drug Liberation; Hydrodynamics; Hydrogen-Ion Concentration; Kinetics; Models, Chemical; Particle Size; Solubility
PubMed: 32886520
DOI: 10.1021/acs.molpharmaceut.0c00614 -
Experimental Physiology Mar 2020What is the topic of this review? The [Ca ]/[Mg ] in buffers are usually calculated using one of eight programs. These all give different values, thus [Ca ]/[Mg ] must... (Review)
Review
NEW FINDINGS
What is the topic of this review? The [Ca ]/[Mg ] in buffers are usually calculated using one of eight programs. These all give different values, thus [Ca ]/[Mg ] must be measured. What advances does it highlight? The ligand optimization method (LOM) using electrodes is an accurate method to do this. The limitations of the method are described. The LOM has been generalized to include calibration of fluorochromes and aequorin. It is the method of choice to measure intracellular equilibrium constants. Owing to the uncertainties for the values of resting [Ca ], ∆[Ca ] and the pK' values for intracellular Ca /Mg binding used in modelling, these values must now be re-examined critically.
ABSTRACT
Modelling intracellular regulation of Ca /Mg is now an established part of physiology. However, the conclusions drawn from such studies depend on accurate knowledge of intracellular [Ca ], ∆[Ca ] and the pK' values for the intracellular binding of Ca /Mg . Calculation of [Ca ]/[Mg ] in buffers is normal. The eight freely available programs all give different values for the [Ca ]/[Mg ] in the buffer solutions, varying by up to a factor of 4.3. As a result, concentrations must be measured. There are two methods to do this, both based on the ligand optimization method (LOM): (1) calibration solutions from 0.5 to 4 mmol l ; and (2) calibration solutions from 0.1 µmol l to 2 mmol l . Both methods can be used to calibrate Ca /Mg electrodes. Only Method 2 can be used directly to calibrate fluorochromes and aequorin. Software in the statistical program R to calculate the [Ca ]/[Mg ] in buffers is provided for both methods. The LOM has now been generalized for use with electrodes, fluorochromes and aequorin, making it the ideal method to determine the pK' values for intracellular binding of Ca /Mg . The [Ca ]/[Mg ] in buffers must be measured routinely, which is best done by calibrating electrodes with the LOM and software written in R. If [Ca ]/[Mg ] in buffers are calculated, the parameters used in modelling show the same degree of variability as the software programs. Uncritical acceptance of such parameters means that conclusions reached from such studies are relative, not absolute, and must now be re-examined.
Topics: Buffers; Calcium; Calibration; Electrodes; Ligands; Magnesium
PubMed: 31758871
DOI: 10.1113/EP088345 -
Stomatologija 2011OBJECTIVE. The purpose of this study is to evaluate the ability of two commercial strip tests and laboratory titration to detect saliva buffer capacity. MATERIALS AND... (Comparative Study)
Comparative Study
OBJECTIVE. The purpose of this study is to evaluate the ability of two commercial strip tests and laboratory titration to detect saliva buffer capacity. MATERIALS AND METHODS. Sixty-four patients were examined. Stimulated saliva was collected and buffer capacity was determined with two different chair-side strip tests in addition to immediate transportation to the laboratory to check the buffering ability by titrating with 0.005 M HCl and measuring pH by digital pH/Ion meter, used as a gold standart. The correlation were analyzed using the Spearman Rank Correlation Test, Cohen's Kappa coefficient and Pearson's Correlation test, p < 0.01. Sensitivity and specificity were used to measure precision of these tests. RESULTS. The response rate was 80%. High buffer capacity was found in 23.4% of cases, medium in 62.5%, and low in 14.1%. The Spearman Rank Correlation coefficient between the titration method and CRT Buffer test was 0.685 and the GC Saliva Check Buffer was 0.837. The Kappa coefficient for the CRT Buffer test was 0.508, while the coefficient for the GC Saliva Check Buffer was 0.752. The Pearson Correlation for the GC Saliva Check was 0.675. The difference is found in the buffer capacity at initial pH and at pH value 3. CONCLUSIONS. Both colorimetric tests correlate with the acid titration method in laboratory and are usable for saliva buffer capacity detection in dental offices. Buffer capacity detected in laboratory at different pH values can provide more information regarding caries risk.
Topics: Adult; Buffers; Clinical Laboratory Techniques; Colorimetry; Dental Caries Activity Tests; Humans; Hydrogen-Ion Concentration; Middle Aged; Reagent Kits, Diagnostic; Risk Assessment; Saliva; Sensitivity and Specificity; Statistics, Nonparametric; Surveys and Questionnaires; Young Adult
PubMed: 21822046
DOI: No ID Found