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Seminars in Nephrology Jul 2019Although students initially learn of ionic buffering in basic chemistry, buffering and acid-base transport in biology often is relegated to specialized classes,... (Review)
Review
Although students initially learn of ionic buffering in basic chemistry, buffering and acid-base transport in biology often is relegated to specialized classes, discussions, or situations. That said, for physiology, nephrology, pulmonology, and anesthesiology, these basic principles often are critically important for mechanistic understanding, medical treatments, and assessing therapy effectiveness. This short introductory perspective focuses on basic chemistry and transport of buffers and acid-base equivalents, provides an outline of basic science acid-base concepts, tools used to monitor intracellular pH, model cellular responses to pH buffer changes, and the more recent development and use of genetically encoded pH-indicators. Examples of newer genetically encoded pH-indicators (pHerry and pHire) are provided, and their use for in vitro, ex vivo, and in vivo experiments are described. The continued use and development of these basic tools provide increasing opportunities for both basic and potentially clinical investigations.
Topics: Acid-Base Equilibrium; Animals; Biological Transport; Buffers; Humans; Hydrogen; Hydrogen-Ion Concentration; Intracellular Fluid
PubMed: 31300088
DOI: 10.1016/j.semnephrol.2019.04.002 -
Physiological Reviews Oct 2023Calcium signaling underlies much of physiology. Almost all the Ca in the cytoplasm is bound to buffers, with typically only ∼1% being freely ionized at resting levels... (Review)
Review
Calcium signaling underlies much of physiology. Almost all the Ca in the cytoplasm is bound to buffers, with typically only ∼1% being freely ionized at resting levels in most cells. Physiological Ca buffers include small molecules and proteins, and experimentally Ca indicators will also buffer calcium. The chemistry of interactions between Ca and buffers determines the extent and speed of Ca binding. The physiological effects of Ca buffers are determined by the kinetics with which they bind Ca and their mobility within the cell. The degree of buffering depends on factors such as the affinity for Ca, the Ca concentration, and whether Ca ions bind cooperatively. Buffering affects both the amplitude and time course of cytoplasmic Ca signals as well as changes of Ca concentration in organelles. It can also facilitate Ca diffusion inside the cell. Ca buffering affects synaptic transmission, muscle contraction, Ca transport across epithelia, and the killing of bacteria. Saturation of buffers leads to synaptic facilitation and tetanic contraction in skeletal muscle and may play a role in inotropy in the heart. This review focuses on the link between buffer chemistry and function and how Ca buffering affects normal physiology and the consequences of changes in disease. As well as summarizing what is known, we point out the many areas where further work is required.
Topics: Humans; Calcium; Buffers; Cytoplasm; Heart; Synaptic Transmission; Calcium Signaling
PubMed: 37326298
DOI: 10.1152/physrev.00042.2022 -
Journal of Oleo Science 2021Monoammonium glycyrrhizinate is produced by the neutralization of glycyrrhizic acid from plant licorice with ammonia. In this study, the physicochemical properties of...
Monoammonium glycyrrhizinate is produced by the neutralization of glycyrrhizic acid from plant licorice with ammonia. In this study, the physicochemical properties of aqueous monoammonium glycyrrhizinate were investigated from the viewpoint of surface chemistry. The structure of the amphiphilic molecule is bola type, comprising two glucuronic acid moieties having two carboxylic acids groups and an aglycone part having a carboxylic acid at the opposite end of the molecule from the glucuronic acids. We found that the physicochemical properties of aqueous monoammonium glycyrrhizinate are dependent on the ionization of the carboxylic acid groups. The solubility of monoammonium glycyrrhizinate gradually increased above pH 4 in the buffer solution. The critical micelle concentration (CMC) and surface tension at the CMC (γ) of monoammonium glycyrrhizinate were determined by the surface tension method to be 1.5 mmol L and 50 mN m in pH 5 buffer and 3.7 mmol L and 51 mN m in pH 6 buffer, respectively. The surface tension gradually decreased with increasing concentration of monoammonium glycyrrhizinate in the pH 7 buffer, but the CMC was not defined by the curve. Light scattering measurements also did not reveal a clear CMC in the pH 7 buffer. The ionization of the carboxylic acid groups in the bola-type amphiphilic molecule with increasing pH is disadvantageous for micelle formation. Cryo-transmission electron microscopy showed that monoammonium glycyrrhizinate forms rod-like micelles in pH 5 buffer, and small angle X-ray scattering experiments confirmed that the average micellar structure was rod-like in pH 5 buffer. Thus, it was found that monoammonium glycyrrhizinate can form micelles only in weakly acidic aqueous solutions.
Topics: Buffers; Glycyrrhizic Acid; Hydrogen-Ion Concentration; Micelles; Solubility; Surface Tension
PubMed: 34193668
DOI: 10.5650/jos.ess21046 -
International Journal of Molecular... Oct 2021A useful tool to analyze the ligands and/or environmental contribution to protein stability is represented by the Synchrotron Radiation Circular Dichroism...
A useful tool to analyze the ligands and/or environmental contribution to protein stability is represented by the Synchrotron Radiation Circular Dichroism UV-denaturation assay that consists in the acquisition of several consecutive repeated far-UV SRCD spectra. Recently we demonstrated that the prevailing mechanism of this denaturation involves the generation of free radicals and reactive oxygen species (ROS). In this work, we analyzed the effect of buffering agents commonly used in spectroscopic measurements, including MOPS (3-(N-morpholino) propanesulfonic acid), HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid), TRIS-HCl (tris-hydroxymethil aminomethane hydrochloride), and phosphate, on the efficiency of protein denaturation caused by exposure to UV radiation. Fluorescence experiments confirmed the presence of ROS and were used to determine the rate of ROS generation. Our results indicate that the efficiency of the denaturation process is strongly influenced by the buffer composition with MOPS and HEPES acting also as scavengers and that the presence of proteins itself influenced the ROS formation rate.
Topics: Biological Assay; Buffers; Circular Dichroism; Free Radicals; Ligands; Protein Denaturation; Protein Stability; Proteins; Reactive Oxygen Species; Synchrotrons; Ultraviolet Rays
PubMed: 34768758
DOI: 10.3390/ijms222111325 -
The Journal of Histochemistry and... Apr 2017
Topics: Buffers; Ethanol; Fixatives; Formaldehyde; Tissue Fixation
PubMed: 28347267
DOI: 10.1369/0022155416687278 -
European Journal of Pharmaceutics and... Jun 2021In the pharmaceutical industry, cryoprotectants are added to buffer formulations to protect the active pharmaceutical ingredient from freeze- and thaw damage. We...
In the pharmaceutical industry, cryoprotectants are added to buffer formulations to protect the active pharmaceutical ingredient from freeze- and thaw damage. We investigated the freezing and thawing of aqueous sodium citrate buffer with various cryoprotectants, specifically amino acids (cysteine, histidine, arginine, proline and lysine), disaccharides (trehalose and sucrose), polyhydric alcohols (glycerol and mannitol) and surfactants (polysorbate 20 and polysorbate 80). Hereby, we employed optical cryomicroscopy in combination with differential scanning calorimetry in the temperature range to -80 °C. The effect of cryoprotectants on the morphology of the ice crystals, the glass transition temperature and the initial melting temperature is presented. Some of the cryoprotectants have a significant impact on ice crystal size. Disaccharides restrict ice crystal growth, whereas surfactants and glycerol allow ice crystals to increase in size. Cysteine and mannitol cause dehydration after thawing. Either one or two glass transition temperatures were detected, where arginine, surfactants, glycerol, proline and lysine suppress the second, implying a uniform freeze-concentrated solution. The initial melting temperature of pure buffer solution can be shifted up by adding mannitol, both disaccharides and both surfactants; but down by glycerol, proline and lysine.
Topics: Buffers; Calorimetry, Differential Scanning; Chemistry, Pharmaceutical; Cryoprotective Agents; Freezing; Microscopy; Solutions; Transition Temperature; Vitrification
PubMed: 33813056
DOI: 10.1016/j.ejpb.2021.03.015 -
Fly Dec 2021Sperm quality, an important male fitness trait, is commonly compared between studies. However, few studies consider how genetic and environmental variation affect sperm...
Sperm quality, an important male fitness trait, is commonly compared between studies. However, few studies consider how genetic and environmental variation affect sperm quality, even in the genetic model . Here we show that sperm viability, the proportion of live sperm, differed across the genotypes Oregon-R, Dahomey, and Canton-S by more than 15%, and across buffers (phosphate-buffered saline (PBS), Grace's Medium and Ringer solution) by more than 20%. In terms of genotype-buffer pair comparisons, nearly half of the comparisons would produce significant differences in sperm viability (15 in 36), or its temporal decrease in a stress medium (19 in 36). Grace's medium produced the longest-lived sperm and the smallest differences between genotypes, Ringer Solution produced the shortest lifespan and the largest differences. Our results suggest that fly and other sperm researchers would benefit from a standardized protocol of measuring sperm viability.
Topics: Animals; Buffers; Cell Survival; Culture Media; Drosophila melanogaster; Genotype; Male; Spermatozoa
PubMed: 33054517
DOI: 10.1080/19336934.2020.1837592 -
Proceedings of the National Academy of... Jan 2022Bioelectrochemistry employs an array of high-surface-area meso- and macroporous electrode architectures to increase protein loading and the electrochemical current...
Bioelectrochemistry employs an array of high-surface-area meso- and macroporous electrode architectures to increase protein loading and the electrochemical current response. While the local chemical environment has been studied in small-molecule and heterogenous electrocatalysis, conditions in enzyme electrochemistry are still commonly established based on bulk solution assays, without appropriate consideration of the nonequilibrium conditions of the confined electrode space. Here, we apply electrochemical and computational techniques to explore the local environment of fuel-producing oxidoreductases within porous electrode architectures. This improved understanding of the local environment enabled simple manipulation of the electrolyte solution by adjusting the bulk pH and buffer pK to achieve an optimum local pH for maximal activity of the immobilized enzyme. When applied to macroporous inverse opal electrodes, the benefits of higher loading and increased mass transport were employed, and, consequently, the electrolyte adjusted to reach -8.0 mA ⋅ cm for the H evolution reaction and -3.6 mA ⋅ cm for the CO reduction reaction (CORR), demonstrating an 18-fold improvement on previously reported enzymatic CORR systems. This research emphasizes the critical importance of understanding the confined enzymatic chemical environment, thus expanding the known capabilities of enzyme bioelectrocatalysis. These considerations and insights can be directly applied to both bio(photo)electrochemical fuel and chemical synthesis, as well as enzymatic fuel cells, to significantly improve the fundamental understanding of the enzyme-electrode interface as well as device performance.
Topics: Algorithms; Buffers; Electrochemical Techniques; Electrochemistry; Electrodes; Electrolytes; Enzymes; Microelectrodes; Molecular Structure; Porosity; Structure-Activity Relationship
PubMed: 35058361
DOI: 10.1073/pnas.2114097119 -
Advanced Drug Delivery Reviews Apr 2017Endosomes and lysosomes play a critical role in various aspects of cell physiology such as nutrient sensing, receptor recycling, protein/lipid catabolism, and cell... (Review)
Review
Endosomes and lysosomes play a critical role in various aspects of cell physiology such as nutrient sensing, receptor recycling, protein/lipid catabolism, and cell death. In drug delivery, endosomal release of therapeutic payloads from nanocarriers is also important in achieving efficient delivery of drugs to reach their intracellular targets. Recently, we invented a library of ultra pH-sensitive (UPS) nanoprobes with exquisite fluorescence response to subtle pH changes. The UPS nanoprobes also displayed strong pH-specific buffer effect over small molecular bases with broad pH responses (e.g., chloroquine and NHCl). Tunable pH transitions from 7.4 to 4.0 of UPS nanoprobes cover the entire physiological pH of endocytic organelles (e.g., early and late endosomes) and lysosomes. These unique physico-chemical properties of UPS nanoprobes allowed a 'detection and perturbation' strategy for the investigation of luminal pH in cell signaling and metabolism, which introduces a nanotechnology-enabled paradigm for the biological studies of endosomes and lysosomes.
Topics: Buffers; Endosomes; Humans; Hydrogen-Ion Concentration; Lysosomes; Signal Transduction
PubMed: 27612550
DOI: 10.1016/j.addr.2016.08.014 -
Journal of Chromatography. A Apr 2023Buffer management for biopharmaceutical purification processes include buffer preparation, storage of buffers and restocking the buffers when needed. This is usually...
Buffer management for biopharmaceutical purification processes include buffer preparation, storage of buffers and restocking the buffers when needed. This is usually performed manually by the operators for small scale operations. However, buffer management can become a bottleneck when running integrated continuous purification processes for prolonged times, even at small scale. To address this issue, a buffer management system for the application in continuous lab-scale bioprocessing is presented in this paper. For this purpose, an ÄKTA™ explorer chromatography system was reconfigured to perform the buffer formulation. The system formulated all buffers from stock solutions and water according to pre-specified recipes. A digital twin of the physical system was introduced in the research software Orbit, written in python. Orbit was also used for full automation and control of the buffer system, which could run independently without operator input and handle buffer management for one or several connected buffer-consuming purification systems. The developed buffer management system performed automatic monitoring of buffer volumes, buffer order handling as well as buffer preparation and delivery. To demonstrate the capability of the developed system, it was integrated with a continuous downstream process and supplied all 9 required buffers to the process equipment during a 10-day operation. The buffer management system processed 55 orders and delivered 38 L of buffers, corresponding to 20% of its capacity. The pH and conductivity profiles observed during the purification steps were consistent across the cycles. The deviation in conductivity and pH from the measured average value was within ±0.89% in conductivity and ±0.045 in pH, well within the typical specification for buffer release, indicating that the prepared buffers had the correct composition. The operation of the developed buffer management system was robust and fully automated, and provides one solution to the buffer management bottleneck on lab scale for integrated continuous downstream bioprocessing.
Topics: Buffers; Chromatography; Automation; Water
PubMed: 37015183
DOI: 10.1016/j.chroma.2023.463942