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Nano Letters Dec 2018Biological membranes possess intrinsic asymmetry. This asymmetry is associated not only with leaflet composition in terms of membrane species but also with differences...
Biological membranes possess intrinsic asymmetry. This asymmetry is associated not only with leaflet composition in terms of membrane species but also with differences in the cytosolic and periplasmic solutions containing macromolecules and ions. There has been a long quest for understanding the effect of ions on the physical and morphological properties of membranes. Here, we elucidate the changes in the mechanical properties of membranes exposed to asymmetric buffer conditions and the associated curvature generation. As a model system, we used giant unilamellar vesicles (GUVs) with asymmetric salt and sugar solutions on the two sides of the membrane. We aspirated the GUVs into micropipettes and attached small beads to their membranes. An optical tweezer was used to exert a local force on a bead, thereby pulling out a membrane tube from the vesicle. The assay allowed us to measure the spontaneous curvature and the bending rigidity of the bilayer in the presence of different ions and sugar. At low sugar/salt (inside/out) concentrations, the membrane spontaneous curvature generated by NaCl and KCl is close to zero, but negative in the presence of LiCl. In the latter case, the membrane bulges away from the salt solution. At high sugar/salt conditions, the membranes were observed to become more flexible and the spontaneous curvature was enhanced to even more negative values, comparable to those generated by some proteins. Our findings reveal the reshaping role of alkali chlorides on biomembranes.
Topics: Membranes, Artificial; Potassium Chloride; Sodium Chloride; Unilamellar Liposomes
PubMed: 30456959
DOI: 10.1021/acs.nanolett.8b03584 -
Sensors (Basel, Switzerland) Apr 2022In this paper, an improved double inputs direct contact and single output capacitively coupled conductivity detector (DISODCD) based on traditional contactless...
In this paper, an improved double inputs direct contact and single output capacitively coupled conductivity detector (DISODCD) based on traditional contactless capacitively coupled conductivity detector (CD) is developed. The sensor uses double inputs of the contact electrode and capacitively coupled output of the contactless electrode and a lock-in amplifier to reduce interfering noise signals and amplify gain. Parallel circuit counteracts the part of the adverse capacitance reactance introduced by electrode polarization and reduces the effect of the impedance caused by the coupled wall capacitance to measure the resistance of solution. The sensor reduces limit of detection (LOD) of analyte and improves the sensitivity of the device. The LOD of the potassium chloride solution is 1 nM, and the detection range is 0.01 μM to 10 mM in actual testing for a single sample. The ratio of the response of potassium chloride solution to background ultrapure water at low concentrations is better than that of double input capacitively coupled contactless conductivity detector (DICD) and direct contact conductivity detection (DCD) under the same condition. In the case that the test cell is contaminated with impurities, pollution of impurities has little effect on the response of DISODCD. In practical application, it has a good service life.
Topics: Electric Capacitance; Electric Conductivity; Electric Impedance; Limit of Detection; Potassium Chloride
PubMed: 35408343
DOI: 10.3390/s22072729 -
Arthritis and Rheumatism Dec 1965
Topics: Ammonium Chloride; Blood; Chlorothiazide; Humans; Potassium Chloride; Uric Acid; Urine
PubMed: 5884822
DOI: 10.1002/art.1780080612 -
Anaesthesia Jan 1985A patient is presented in whom 15 ml of 15% potassium chloride (30 mM) mixed with bupivacaine was injected epidurally for relief of pain resulting from widespread pelvic...
A patient is presented in whom 15 ml of 15% potassium chloride (30 mM) mixed with bupivacaine was injected epidurally for relief of pain resulting from widespread pelvic malignancy. Within minutes the patient complained of severe pain in both the lower limbs and rapidly became paraplegic with bladder and bowel incontinence. The paraplegia was permanent. The transient symptoms of pain may have been partly due to the irritant effects of a hyperosmolar solution of potassium chloride in the epidural space, while the permanent neurological damage might have been due to the very high extracellular concentration of potassium leading on to a depolarising phenomenon initially followed by nerve tissue necrosis.
Topics: Adult; Anesthesia, Epidural; Bupivacaine; Chronic Disease; Female; Humans; Medication Errors; Morphine; Pain Management; Paraplegia; Potassium Chloride
PubMed: 3970337
DOI: 10.1111/j.1365-2044.1985.tb10501.x -
Canadian Medical Association Journal Jan 1965
Topics: Humans; Intestinal Diseases; Intestinal Obstruction; Potassium Chloride; Thiazides; Toxicology; Ulcer
PubMed: 14232197
DOI: No ID Found -
The Canadian Veterinary Journal = La... Mar 2011Twelve parrots anesthetized with isoflurane were euthanized intravenously (IV) with 3 or 10 mEq/kg body weight (BW) of potassium chloride (KCl) resulting in ventricular...
Twelve parrots anesthetized with isoflurane were euthanized intravenously (IV) with 3 or 10 mEq/kg body weight (BW) of potassium chloride (KCl) resulting in ventricular asystole at 68.0 s and 32.8 s, respectively. Mild vocalization (1/6 birds, 3 mEq/kg BW) and involuntary muscle tremors (5/6 birds, 10 mEq/kg BW) were noted. Unlike barbiturates or T-61 no histologic artefacts resulted from this technique.
Topics: Animals; Euthanasia, Animal; Female; Histocytochemistry; Injections, Intravenous; Male; Parrots; Potassium Chloride
PubMed: 21629426
DOI: No ID Found -
The Journal of Biophysical and... Jul 1960The electrical capacity of the membrane of rat liver mitochondria is 0.5 to 0.6 micro./cm(2). This membrane capacity is obtained from the analysis of the frequency...
The electrical capacity of the membrane of rat liver mitochondria is 0.5 to 0.6 micro./cm(2). This membrane capacity is obtained from the analysis of the frequency dependence of the admittance of a suspension of swollen mitochondria. In potassium chloride media the mitochondrial membrane capacity does not depend on the ion concentration. The internal conductance of the mitochondria was approximately one-half that of the external medium; the same applies if the mitochondria are equilibrated in a medium with a 10-fold difference in potassium chloride concentration. Hence the swollen mitochondria investigated here appear to be able to adjust their internal ion concentration in proportion with that of the external phase. The similarity of the membrane capacity of isolated mitochondria with the range of values known for other membranes suggests a common molecular structure. The analysis of experimental data suggests an anisotropic electrical behavior of the interior of mitochondria. This anisotropy is readily explained by the existence of internal membranes.
Topics: Animals; Membranes; Mitochondria; Mitochondria, Liver; Mitochondrial Membranes; Potassium Chloride; Rats
PubMed: 14431035
DOI: 10.1083/jcb.7.4.589 -
PloS One 2015Potassium ion homeostasis plays an important role in regulating membrane potential and therefore resistance to cations, antibiotics and chemotherapeutic agents in...
BACKGROUND
Potassium ion homeostasis plays an important role in regulating membrane potential and therefore resistance to cations, antibiotics and chemotherapeutic agents in Schizosaccharomyces pombe and other yeasts. However, the precise relationship between drug resistance in S. pombe and external potassium concentrations (particularly in its natural habitats) remains unclear. S. pombe can tolerate a wide range of external potassium concentrations which in turn affect plasma membrane polarization. We thus hypothesized that high external potassium concentrations suppress the sensitivity of this yeast to various drugs.
METHODS
We have investigated the effect of external KCl concentrations on the sensitivity of S. pombe cells to a wide range of antibiotics, antimicrobial agents and chemotherapeutic drugs. We employed survival assays, immunoblotting and microscopy for these studies.
RESULTS
We demonstrate that KCl, and to a lesser extent NaCl and RbCl can suppress the sensitivity of S. pombe to a wide range of antibiotics. Ammonium chloride and potassium hydrogen sulphate also suppressed drug sensitivity. This effect appears to depend in part on changes to membrane polarization and membrane transport proteins. Interestingly, we have found little relationship between the suppressive effect of KCl on sensitivity and the structure, polarity or solubility of the various compounds investigated.
CONCLUSIONS
High concentrations of external potassium and other cations suppress sensitivity to a wide range of drugs in S. pombe. Potassium-rich environments may thus provide S. pombe a competitive advantage in nature. Modulating potassium ion homeostasis may sensitize pathogenic fungi to antifungal agents.
Topics: Antifungal Agents; Antiporters; Cations; Drug Resistance, Fungal; Fungicides, Industrial; Mutation; Potassium Chloride; Saccharomyces cerevisiae Proteins; Schizosaccharomyces
PubMed: 25793410
DOI: 10.1371/journal.pone.0119297 -
Scientific Reports Feb 2020Halophiles utilize two distinct osmoprotection strategies. The accumulation of organic compatible solutes such as glycine betaine does not perturb the functioning of...
Halophiles utilize two distinct osmoprotection strategies. The accumulation of organic compatible solutes such as glycine betaine does not perturb the functioning of cytoplasmic components, but represents a large investment of energy and carbon. KCl is an energetically attractive alternative osmoprotectant, but requires genome-wide modifications to establish a highly acidic proteome. Most extreme halophiles are optimized for the use of one of these two strategies. Here we examine the extremely halophilic Proteobacterium Halorhodospira halophila and report that medium K concentration dramatically alters its osmoprotectant use. When grown in hypersaline media containing substantial K concentrations, H. halophila accumulates molar concentrations of KCl. However, at limiting K concentrations the organism switches to glycine betaine as its major osmoprotectant. In contrast, the closely related organism Halorhodospira halochloris is limited to using compatible solutes. H. halophila performs both de novo synthesis and uptake of glycine betaine, matching the biosynthesis and transport systems encoded in its genome. The medium K concentration (~10 mM) at which the KCl to glycine betaine osmoprotectant switch in H. halophila occurs is near the K content of the lake from which it was isolated, supporting an ecological relevance of this osmoprotectant strategy.
Topics: Bacterial Proteins; Betaine; Halorhodospira halophila; Osmolar Concentration; Potassium Chloride; Proteome; Spectrophotometry
PubMed: 32098991
DOI: 10.1038/s41598-020-59231-9 -
Journal of Dairy Science Sep 2011The range of sodium chloride (salt)-to-moisture ratio is critical in producing high-quality cheese products. The salt-to-moisture ratio has numerous effects on cheese...
The range of sodium chloride (salt)-to-moisture ratio is critical in producing high-quality cheese products. The salt-to-moisture ratio has numerous effects on cheese quality, including controlling water activity (a(w)). Therefore, when attempting to decrease the sodium content of natural cheese it is important to calculate the amount of replacement salts necessary to create the same a(w) as the full-sodium target (when using the same cheese making procedure). Most attempts to decrease sodium using replacement salts have used concentrations too low to create the equivalent a(w) due to the differences in the molecular weight of the replacers compared with salt. This could be because of the desire to minimize off-flavors inherent in the replacement salts, but it complicates the ability to conclude that the replacement salts are the cause of off-flavors such as bitter. The objective of this study was to develop a model system that could be used to measure a(w) directly, without manufacturing cheese, to allow cheese makers to determine the salt and salt replacer concentrations needed to achieve the equivalent a(w) for their existing full-sodium control formulas. All-purpose flour, salt, and salt replacers (potassium chloride, modified potassium chloride, magnesium chloride, and calcium chloride) were blended with butter and water at concentrations that approximated the solids, fat, and moisture contents of typical Cheddar cheese. Salt and salt replacers were applied to the model systems at concentrations predicted by Raoult's law. The a(w) of the model samples was measured on a water activity meter, and concentrations were adjusted using Raoult's law if they differed from those of the full-sodium model. Based on the results determined using the model system, stirred-curd pilot-scale batches of reduced- and full-sodium Cheddar cheese were manufactured in duplicate. Water activity, pH, and gross composition were measured and evaluated statistically by linear mixed model. The model system method accurately determined the concentrations of salt and salt replacer necessary to achieve the same a(w) as the full-sodium control in pilot-scale cheese using different replacement salts.
Topics: Calcium Chloride; Cheese; Food Handling; Magnesium Chloride; Models, Theoretical; Potassium Chloride; Sodium Chloride; Sodium, Dietary; Water
PubMed: 21854908
DOI: 10.3168/jds.2011-4359