Activity Coefficient And Ionic Strength

Ionic Strength

Ionic strength of a buffer is divers every bit 0.5 ∑i(zi2ci), where zi is the valence of ion i and ci is its tooth concentration.

From: Methods in Enzymology , 2001

Immunochemical Techniques

Nader Rifai PhD , in Tietz Textbook of Clinical Chemistry and Molecular Diagnostics , 2018

Ion Species and Ionic Strength Effects

Cationic salts produce an inhibition of the binding of antibiotic with a cationic hapten. ⁶ The order of inhibition by various cations is cesium (Cs⁺) > rubidium (Rb⁺) > ammonium (

) > potassium (K⁺) > sodium (Na⁺) > lithium (Li⁺). This order corresponds to the decreasing ionic radius and the increasing radius of hydration. Similar results are observed with anionic haptens and anionic salts. For example, the order of inhibition of binding for anionic salts is thiocyanate (CNS⁻) > nitrate (NO₃ ⁻) > iodide (I⁻) > bromide (Br⁻) > chloride (Cl⁻) > fluoride (F⁻), which again is in the social club of decreasing ionic radius and increasing radius of hydration. If the competition theory equally suggested by these experiments is correct, the degree of inhibition would exist expected to be a concentration-dependent phenomenon, and indeed the rate of formation of immune complexes is slower in normal saline (NaCl, 0.15 mol/L) than the aforementioned reaction carried out in deionized water. Given the previous observation, F⁻ should be the anion of choice for immunochemical reaction buffers. In fact, F⁻ does provide a modest improvement over Cl⁻, but the advantage is so small that laboratories rarely substitute toxic fluoride ion for innocuous chloride ion in buffer solutions.

New Methods and Sensors for Membrane and Cell Volume Research

Luca Mantovanelli , ... Bert Poolman , in Electric current Topics in Membranes, 2021

5.2.6 Ionic strength sensors

Ionic strength tin exist measured via a FRET-based sensor that acts similarly to the macromolecular crowding sensor ( Liu, Poolman, & Boersma, 2017). This sensor also consists of 2 fluorescent proteins joined by a flexible linker. Hither, the linker consists of two α-helices with reverse charges. At depression ionic strength levels, the reverse charges of the helices attract each other, increasing the FRET efficiency. At college ionic strength levels, the charges of the linker are shielded past ions, which allows the FPs to stay further apart, which lowers the apparent FRET ratio.

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Systemic Anaphylaxis, Nutrient Allergy, and Insect Sting Allergy

Lee Goldman Doc , in Goldman-Cecil Medicine , 2020

Not–IgE-Dependent Agonists

Many non–IgE-dependent activators of mast cells do not crave processing and can arm-twist a response on kickoff exposure. These include radiocontrast dyes, most narcotics except for fentanyl, and vancomycin. The dose and rate of administration and individual variations in reactivity are determinants of severity. For radiocontrast dyes, those of low ionic force and iso-osmolarity are less likely than those of high ionic strength and hyper-osmolarity to elicit a systemic reaction. Vancomycin produces a non–IgE-dependent mast cell activation event known as "reddish man syndrome," typically involving pruritic flushing, only without cardiovascular compromise unless infused too rapidly. These reactions unremarkably are avoided by reducing the rate of assistants of the antibiotic, thereby reducing peak levels.

Endogenous mast cell activators include neuropeptides such as substance P, neurokinin A, and calcitonin gene-related peptide, defensins, and the complement anaphylatoxins C3a and C5a. Although C3a and C5a have their own receptors on mast cells, neurokinins, vancomycin, and narcotics actuate a G protein–coupled receptor selectively expressed on mast cells, called Mas-related G protein–coupled receptor X2 (MRGPCR-X2), causing histamine secretion.

Aspirin and Nonsteroidal Anti-inflammatory Drugs

Aspirin hypersensitivity typically manifests as either a respiratory reaction with bronchospasm, nasal congestion, and rhinorrhea or a cardiovascular reaction with hypotension and urticaria, although sometimes overlap occurs, including gastrointestinal signs and symptoms. In most cases, such reactions announced to be pharmacologically (not IgE) mediated, and in sensitive subjects they tin occur in response to any of the cyclooxygenase 1 (COX1) inhibitors. Although COX1 inhibitors may shunt arachidonic acrid metabolism to the lipoxygenase pathway, a mechanism to explicate mast jail cell activation has non nevertheless emerged. COX2-selective inhibitors appear to be safe in aspirin-intolerant asthmatics, but not always in the cardiovascular group. Less commonly, sensitivity occurs to but 1 of the drugs inside this grade, a clue that IgE against a unique chemical moiety on that particular drug is involved.

Concrete Stimuli

Concrete stimuli may precipitate urticaria or systemic anaphylaxis in certain individuals. Episodes can occur in response to exercise, estrus, solar radiations, vibration, force per unit area, or cold. Exercise-dependent anaphylaxis is sometimes associated with ingestion of whatsoever food, regardless of whether sensitivity to the food can be documented, occurring within several hours of ingestion and might exist avoided past delaying practise until several hours after eating. In some cases of familial common cold- or vibration-triggered urticaria, genetic defects take been found. ¹¹ ^, ¹²

Levels of Drug Targeting

Khushwant S. Yadav , ... Anil M. Pethe , in Basic Fundamentals of Drug Delivery, 2019

7.iii.3.3 Ionic Strength

The in vivo ionic strength affects both the drug release as well as targeting ability. A alter in the in vivo ionic forcefulness tin can decide the release of the encapsulated drug to occur within specific areas of the body. The dispersion buffer ionic strength and particle composition independently affect their uptake in vivo. Solvent ionic strength has an bear upon on electrostatic interactions.

A reduction in ionic strength causes an increment in electrostatic potential betwixt the epithelium and the particles. This principle is particularly of interest in nasal drug delivery as below a critical ionic strength; there is an enhanced intranasal particle uptake in vivo. Lower ionic force affects the targeting of peptides. The M cell-targeting ligand is highly dependent on ionic strength. A higher ionic forcefulness would cause greater particle electrostatic forces for better targeting. Increasing the ionic strength of the nanodispersion is associated with a modify in zeta potential also. By varying the ionic strength of the medium, there has been a alter in the targeted PLGA nanoparticles uptake. Lower ionic strengths led to PLGA nanoparticles to exist readily uptaken irrespective of the targeting peptide (Rajapaksa et al., 2010).

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Biological science of Basophils

A. Wesley Burks Doc , in Middleton's Allergy: Principles and Exercise , 2020

Histamine

Basophils constitutively store, on average, approximately 1 pg of histamine per cell, and this amount is remarkably consistent among allergic and nonallergic donor populations. Histamine is synthesized by the actions of histidine decarboxylase, which removes a carboxyl group from50 -histidine. Its storage in basophils is mediated through ionic interactions with the highly charged proteoglycan chondroitin sulfate, as opposed to heparin sulfate in the mast cell. These complexes dissociate with changes in pH and ionic force that occur during the process of degranulation, thus resulting in the release of histamine. The physiologic furnishings of histamine on smoothen muscle, the vasculature, and neural tissues are well documented. As a spasmogen, information technology is capable of shine muscle wrinkle; it causes vascular leakage through its ability to amplify terminal arterioles. The clinical efficacy of histamine H ₁ receptor antagonists in the treatment of allergic symptoms is partially mediated by their ability to prevent histamine from bounden to H₁ receptors in the airways and vasculature.

A Practical Guide to the Study of Calcium in Living Cells

Donald M. Bers , ... Richard Nuccitelli , in Methods in Jail cell Biology, 1994

B Ionic Strength Corrections

Ionic strength besides can alter the G′_Ca dramatically (come across Figs. three–five). We use the procedure described past Smith and Miller (1985) with ionic equivalents (I_east) rather than formal ionic strength (I_e = 0.five · ΣC_i , · |z_i |, where C_i and z_i are the concentration and valence of the i ^th ion). We will use the terms equivalently here. Then the expression used to adjust for ionic forcefulness is

(11) ${log}_{10} M^{'} = {log}_{10} K + 2 ten y ({log}_{10} f_{i} - {log}_{10} f_{j}^{'})$

where K′ is the constant later on conversion, Yard is the constant before, and x and y are the valences of cation and anion involved in the reaction. The terms log₁₀ f_j and logio f′_j are adjustment terms related to the activity coefficients for nada ionic strength and desired ionic strength, respectively. To suit for ionic strength,

(12) ${log}_{x} f_{j} = \frac{A \cdot I_{e}^{1 / 2}}{i + I_{e}^{i / 2}} - b \cdot I_{e}$

where b is a constant (0.25). A is a abiding that depends on temperature and on the dielectric constant of the medium (ϵ)

(13 $A = \frac{1.8246 \cdot x^{6}}{{(ϵ T)}^{3 / 2}}$

where T is the absolute temperature (°1000) and ϵ is the dielectric constant for water. The dielectric constant is temperature dependent and can be constitute in tables, but that is inconvenient for a computer program and then, using a curve-plumbing equipment program, the following equation provides an fantabulous empirical description over the range 0–50°C.

(14) $ϵ = 87.7251 - 0.3974762 \cdot T + 0.0008253 \cdot T^{two}$

where T is in °C. Thus, some intrinsic temperature dependence exists in the ionic forcefulness aligning itself (see Fig. 4A, dashed line). These corrections provide a reasonably good description of the influence of ionic strength on the M′_Ca in Figs. 3–v.

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Enzymes and Nucleic Acids

Hyone-Myong Eun , in Enzymology Primer for Recombinant Deoxyribonucleic acid Technology, 1996

iii. Ionic strength.

Ionic forcefulness ( I) is a measure of the concentration of charges in a solution. It is defined equally ∑C_iz_i ⁱⁱ/two, where C _i is the molar concentration of the ion species i and z _i is the net charge of the ion i. As the ionic strength of a solution increases, the action coefficient (γ) of an ion decreases according to the Debye–Hückel limiting police, log γ = −0.509zⁱⁱI^1/two. The modulation of enzyme activeness past ionic strength (or salts) is largely due to two furnishings: (a) the neutralizing effect by the counterion of the salts on the electrostatic interactions required for substrate binding and (b) the influence on the pOne thousand _a values of the ionizable residues on enzyme and substrates, thus affecting their electrostatic interactions. The ionic strength may also affect the activity of an enzyme by changing the stability and solubilities of the enzyme too equally those of the substrates. The effects of salts on stability becomes more important with more hydrophilic enzymes.

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Laboratory calculations

Steven One thousand. Truscott , in Contemporary Practice in Clinical Chemistry (Quaternary Edition), 2020

Ionic strength

Ionic forcefulness is a unitless quantity that accounts for the charge and concentration of all ions in a solution. It is used to guess the difference betwixt the activity (e.g., as measured past an ion-selective electrode) and the calculated concentration of the ion. The formula for calculating ionic force ( I) in any solution is

$I = \frac{1}{2} \sum c_{i} {z_{i}}^{2}$

where c _i is the molar concentration of each private ion, and z _i is the charge of each ion.

Instance 6.16

Determine the ionic strength of a 0.x M solution of MgCl ₂ at pH 7.0.

The concentrations of each ion in this solution are

[Mg^two+] = 0.10 M

[Cl⁻] = 0.20 M

[H⁺] = 1.0×ten^−vii Thou

[OH⁻] = 1.0×10⁻⁷ Chiliad

Because the hydrogen and hydroxide concentrations to exist negligible in this example, utilise the concentrations and charges for Mg²⁺ and Cl⁻ to calculate ionic strength:

$I = \frac{i}{2} [(0.1) {(+ 2)}^{2} + (0.two) {(- 1)}^{2}] = 0.30$

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Conception of proteins and monoclonal antibodies (mAbs)

Steven J. Shire , in Monoclonal Antibodies, 2015

Ionic force and tonicity modifiers

Ionic strength can affect the beliefs of proteins resulting in salting in (increased solubility) or salting out (decreased solubility). The subtract in solubility with an increase in ionic force is usually attributed to the colloidal stability of a protein. In this framework a protein at whatever given pH has a specific cyberspace charge. Thus the protein molecules repel each other and predominate over whatsoever attractive interactions. As the ionic strength is increased the net charge repulsion is decreased, resulting in potential attractive protein–protein interactions, resulting in subtract of solubility and increment in protein aggregation. It has been reported that the turbidity of an IgG _ane mAb solution increased with an increase in ionic force of the formulation and that the T _thou for unfolding as determined past DSC decreased with an increase in NaCl concentration (Wang, Hu, et al., 2009). It was besides observed that the viscosity of these more turbid mAb solutions increased with an increase in ionic force. In some other example, an IgG_i mAb showed increased turbidity with an increment in ionic strength, and appeared to correlate nicely with conclusion of the B22 and the DSC interaction parameter, thou_D (discussed in greater item in Affiliate 9) (Figure 4.5), i.east., positive B22 and grand_D at fifteen mM NaCl where net interactions are repulsive, and negative B22 and grand_D at 150 mM NaCl where net interactions are attractive.

The tonicity of a poly peptide formulation is related to the osmotic pressure gradient across a semipermeable membrane. This pressure gradient is generated due to the concentration of solutes outside the membrane compartment versus inside the membrane compartment. The traditional discussion of tonicity every bit it relates to biological systems is commonly assessed on the result of the solution tonicity on red claret cells. When the concentration of solute is higher in solution than inside the crimson claret cell water volition flow out through the prison cell membrane in order to balance the concentration of solutes across the membrane. The solution is hypotonic when the concentration of solutes within the crimson cell is greater than the solution outside the jail cell. This results in an influx of h2o often resulting in the bursting of the cell. The solution is termed isotonic when the fluid inside the cell has a similar concentration of solutes as outside the cell. Usually an IV injection or infusion requires an isotonic preparation, whereas an IM or SC injection may be able to handle hypertonic and hypotonic conditions since the protein drug is not administered direct into the blood. However, there has been business related to disruption of tissue and possible pain on injection. In a report in rabbits, NaCl solutions ranging from 0.9% (300 mOsm) to x% (3300 mOsm) were administered by IM and SC injections (Zietkiewicz, Kostrzewska, & Gregor, 1971). Tissue harm, as evidenced by necrosis, occurred between 3.9% (1300 mOsm) and 5.ane% (1670 mOsm). In this study, 69 drugs were likewise evaluated for tonicity and 22 were isotonic, 23 hypertonic, and 24 hypotonic. The last conclusion from this study was that solutions up to 1300 mOsm do not cause necrosis of SC and muscle tissue. Most importantly information technology was ended that for SC and IM injections the solutions do non demand to be isotonic, only should avoid the disquisitional limits of hypertonicity. Information technology should exist emphasized that this study only investigated tissue damage and did not address what the limits were for pain on injection. In some other study, factors associated with musculus hurting in humans were assessed using NaCl solutions of different tonicities (Brazeau, Cooper, Svetic, Smith, & Gupta, 1998). It was shown that muscle pain on IM injection just occurred for hypertonic solutions.

The tonicity of a protein formulation is modulated by inclusion of solutes, and the ionic force of the formulation is dictated by the presence of charged solutes. Ane of the nigh used excipients for adjusting tonicity and ionic strength is NaCl. Even so, NaCl tin hasten the corrosion of stainless steel, particularly the 316L grade used in the bioprocessing of protein drugs (Ryan, Williams, Chater, Hutton, & McPhail, 2002). Thus, alternative excipients should be used for aligning of ionic forcefulness and/or tonicity. Sugars, which are added every bit stabilizers, can as well be used to suit the tonicity. If information technology is not possible to utilise less corrosive excipients such as NaCl another strategy is to utilize a higher grade of stainless steel alloy, which contains very little iron. Hastelloy has been used and although more expensive, the rate of corrosion of this stainless steel alloy is decreased compared to the mutual 316L stainless steel, which has a higher iron content (Davis, 1994; Srindhar, 1992).

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Capillary Zone Electrophoresis

Robert Weinberger , in Practical Capillary Electrophoresis (Second Edition), 2000

D. EFFECT OF BUFFER CONCENTRATION

The expression for the zeta potential is (16)

(two.10) $ζ = \frac{4 π δ e}{ɛ},$

where ɛ = the buffer's dielectric constant, e = total excess accuse in solution per unit area, and δ is the double-layer thickness or Debye ionic radius. The Debye radius is δ = (3 × 10⁷)(Z)(C ^ane/2), where Z = number of valence electrons and C = the buffer concentration.

Every bit the ionic strength increases, the zeta potential and, similarly, the eof decreases in proportion to the foursquare root of the buffer concentration. This was confirmed experimentally (17) for a serial of buffers where the EOF was constitute linear to the natural logarithm ⁱⁱ of the buffer concentration. It was reported that equivalent EOF is found for different buffer types equally long equally the ionic strength is kept constant (17).

The effect of buffer concentration and field strength is shown in Figure 2.9 (18). The electroosmotic mobility is plotted against field strength for phosphate buffer at 3 different concentrations using a 50-μm-i.d. capillary. Every bit expected, the higher buffer concentrations showed lower EOF at all field strengths. Since mobility was plotted, all iii lines should exist flat. Slight positive slopes were reported for all three concentrations, presumably due to heating effects (Department two.6). The same data produced using a 100-μm-i.d. capillary will be examined in that section.

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