Free ionized

A-B relative or external motion undergo free-free transitions (E., E. + dE.) (Ej Ej+ dE within the translational continuum, while the structured particles undergo bound-bound (excitation, de-excitation, excitation transfer) or bound-free (ionization, dissociation) transitions = (a, 3) ->/= (a, (3 ) in their internal electronic, vibrational or rotational structure. The transition frequency (s ) for this collision is... 

Calcium ion-selective electrodes have recently been commercialized for the measurement of either total or ionized calcium Approximately 45 % of the calcium present in serum is bound to proteins, 5% is complexed to simple anions and 50% exists as the free ion. Traditionally, total calcium measurements have been made by releasing the protein bound fraction. An ion-selective electrode has now allowed the free (ionized) calcium to be measured directly. There has been much debate on the clinical significance of these measurements. The dependence of ionized calcium on pH must be considered. Samples must be either treated anaerobically, tonometered to a constant pH or have a correction factor applied. 

More than 99% of total body calcium is found in bone the remaining less than 1% is in the ECF and ICE Calcium plays a critical role in the transmission of nerve impulses, skeletal muscle contraction, myocardial contractions, maintenance of normal cellular permeability, and the formation of bones and teeth. There is a reciprocal relationship between the serum calcium concentration (normally 8.6 to 10.2 mg/dL [2.15 to 2.55 mmol/L]) and the serum phosphate concentration that is regulated by a complex interaction between parathyroid hormone, vitamin D, and calcitonin. About one-half of the serum calcium is bound to plasma proteins the other half is free ionized calcium. Given that the serum calcium has significant protein binding, the serum calcium concentration must be corrected in patients who have low albumin concentrations (the major serum protein). The most commonly used formula adds 0.8 mg/dL (0.2 mmol/L) of calcium for each gram of albumin deficiency as follows ... 

For acute symptomatic hypocalcemia, 200 to 300 mg of elemental calcium is administered IV and repeated until symptoms are fully controlled. This is achieved by infusing 1 g of calcium chloride or 2 to 3 grams of calcium at a rate no faster than 30 to 60 mg of elemental calcium per minute. More rapid administration is associated with hypotension, bradycardia, or cardiac asystole. Total calcium concentration is commonly monitored in critically ill patients. Under normal circumstances, about half of calcium is loosely bound to serum proteins while the other half is free. Total calcium concentration measures bound and free calcium. Ionized calcium measures free calcium only. Under usual circumstances, a normal calcium level implies a normal free ionized calcium level. Ionized calcium should be obtained in patients with comorbid conditions that would lead to inconsistency between total calcium and free serum calcium (abnormal albumin, protein, or immunoglobulin concentrations). For chronic asymptomatic hypocalcemia, oral calcium supplements are given at doses of 2 to 4 g/day of elemental calcium. Many patients with calcium deficiency have concurrent vitamin D deficiency that must also be corrected in order to restore calcium homeostasis.2,37,38... 

Figure 4.13. Model of peptide initiation of mast secretion. Insertion of the hydrophobic region of the peptide into the lipid bilayer properly orients the basic (+) groups at the N-terminus for binding to negatively charged membrane components. As a result, there is activation of the G protein complex with the subsequent generation of inositol triphosphate (IP ) and diacylglycerol (DAG). These intermediates then stimulate the mobilization of cellular Ca and possibly the transient influx of extracellular Ca as well as the activation ofprotein kinase C. As a consequence, the level of intracellular free ionized Ca is maintained at an elevated state. The end result is the exocytotic extrusion of secretory granules.

Rose B, Loewenstein WR Permeability of cell junctions and the local cytoplasmic free ionized calcium concentration A study with aequorin. J Membr Biol 1976 28 87-119. 

Fig. 3.1. Six images recorded in a DC field of 170 V/cm with the laser polarization along the detector axis, for different values of the scaled energy e = f5eieCtron/Af5sp. The images show the transition from predominantly indirect ionization close to the saddlepoint (s = —1) to direct ionization close to the field-free ionization limit...

From a consideration of these data, it would appear that precipitation of insoluble aconitates from molasses is an extremely complicated reaction and is a function not only of the relative amounts of acid and metallic ions present but also the status of the acid in solution. In this latter respect, it would seem that aconitic acid exists in molasses not only as free ionized acid but also as soluble complexes and the conversion of these soluble complexes to insoluble salts is an important yield-governing consideration. 

Flavopiridol, a weakly basic drug (i.e., B), was solubilized by HPPCD with concentrations of free un-ionized, complexed un-ionized, free ionized, and complexed ionized species at pH 4.3 of 0.06, 1.8, 1.5, and 11.3 mmol/L, respectively. The total concentration of HPpCD in the solution was 10% w/v. The pKa of the drug is 5.68. Calculate the complexation constants and the amount of HPpCD needed to make the total solubility of the drug 10.5 mmole/L at pH 5.1. 

The human organism contains 1-1.4 kg calcium, and about 1% of this is in the extracellular fluid. The rest is largely in bone. The serum calcium concentration is 9-11.5 mg/dL, of which 4.5-5.0 mg/dL is in the free, ionized, biologically active form. The rest is protein bound or complexed with a variety of chelators, such as citrate. The daily dietary calcium requirement is 400-500 mg, and each day, 300-400 mg calcium is lost in the urine and an additional 150 mg in the feces. Inorganic phosphorus (largely as HP042 ) amounts to 2.7-4.5 mg/dL in adult serum. 

The action of these two pancreatic exopeptidases on synthetic substrates, proteins, and peptides has been reviewed in detail by Neurath (1960). The specificity requirements which were deduced from studies with synthetic peptides have been confirmed by studies with polypeptides. The structural requirements of specific substrates for both types of carboxy-peptidase are analogous except for the nature of the amino acids which contain the free, ionized a-carboxyl group at the terminus of the substrate. Carboxypeptidase B hydrolyzes most rapidly those bonds formed by terminal lysyl and arginyl residues, whereas carboxypeptidase A hydrolyzes terminal bonds formed by a variety of aromatic, neutral, or acidic amino acids. Of the natural amino acids only carboxyl-terminal prolyl residues are resistant to the action of the enzyme. The rate of hydrolysis depends upon the nature of the side chains of the amino acids which form the susceptible bonds. Thus, differences in the rate of hydrolysis of different substrates may vary several thousandfold. The methods for application of these peptidases to hydrolysis of proteins have been discussed in detail by Canfield and Anfinsen (1963). 

Free ionized This is the active form of calcium and is half the total calcium in the body. 

With prolonged bed rest, fluid retention occurs and plasma protein and albumin concentrations may be decreased by an average of 0.5 and 0.3g/dL, respectively. The concentrations of protein-bound constituents are also reduced, although mobilization of calcium from bones with an increased free ionized fraction compensates for the reduced protein-bound calcium, so serum total calcium is less affected. Serum aspartate aminotransferase activity is usually slightly less in individuals confined to bed than in those undertaking normal physical activity. Initially and paradoxically, creatine kinase (CK) activity is increased as a result of its release from skeletal muscles, but ultimately, CK activity may be less than in active, healthy individuals. Serum potassium may be reduced by up to 0.5mmol/L because of reduction of skeletal muscle mass. 

Diuretic drugs often cause a mild reduction of the plasma potassium concentration hyponatremia may be observed. Hypercalcemia may occur with hemoconcentration, but occasionally the free-ionized and the protein-bound fraction is increased. Thiazides cause hyperglycemia and reduce glucose tolerance, especially in diabetics. Thiazides may cause prerenal azotemia with hyperuricemia as a result of decreased renal blood flow and GFR as a result of reduced blood volume. Thiazides, like other diuretics, by causing hemoconcentration increase the plasma concentration of lipids. Many thiazides induce microsomal enzymes and thus affect lipoprotein concentrations. 

The methods most widely used for quantifying calcium measure either free (ionized) calcium or total calcium. The term ionized calcium is a misnomer because all plasma or serum calcium is ionized whether or not it is associated with protein or small anions by ionic binding. Throughout this... 

Measurement of Free (Ionized) Calcium (See also Chapter 27.)... 

NEXAFS probes the empty electronic levels of the system, which, in the case of HCl, directly reveal if it is dissociated or not (or ionised/molecular). Our measurements show unambiguously the ionisation of HCl on ice at 20 K. This facile ionisation at very low temperature is in good agreement with the idea of a barrier- free ionization of HCl on ice. Furthermore, when measuring the NEXAFS spectra in Photon-Stimulated-Desorption mode (PSD), we greatly enhance the sensitivity to molecular HCl species that could eventually be adsorbed on the surface, especially at low temperature where HCl condensation can occur. Indeed, the PSD spectra show that at 20 K and at low coverage (0.1 L - 0.3 L) a small amount of molecular HCl is condensed at the side of the Cf anions. 

An important aspect of this reaction is the way in which reactants are concentrated near the oxide surface. The free, ionized carboxylate group of MPT - provides a basis for specific adsorption, through complex formation with surface Al centers. Monophenyl terephthalate also experiences favorable electrostatic attraction towards the positive-charged oxide surface. The positive Al oxide surface charge and extent of MPT adsorption both diminish as the pH is decreased (Stone, 1989a). The extent of MPT-adsorption also decreases as the ionic strength is increased, an indication that the surface complex is outer sphere rather than inner sphere (Hayes et al.,... 

Cellular Calcium Regulation Calciiun plays critical roles in cellular communication and regulation. The normally very low resting free ionized concentration of Ca is maintained by a variety of ion channels, pumps, and intracellular storage processes. The elevation of intracellular Ca levels during cell stimulation serves to couple information with cellular response -stimulus-response coupling. The control of Ca " homeostasis represents, therefore, a potentially powerful control of cellular excitability and response [ 5 ]. 

Copper Chlorophyll. Current efforts to improve the green color of processed foods include the use of copper complexes of chlorophyll derivatives. Copper complexes of pheophytin and pheophorbide are available commercially under the names copper chlorophyll and copper chlorophyllin, respectively. Their use in canned foods, soups, candy, and dairy products is permitted in most European countries under regulatory control of the European Economic Community (47). The Food and Agriculture Organization (FAO) of the United Nations (48) has certified their safe use in foods provided that no more than 200 ppm of free ionizable copper is present. Use of copper-containing chlorophyll derivatives in foods is not allowed in the United States under the Color Additive Amendment to the Food, Drug, and Cosmetic Act of 1938. 

Free ionized form, which is the biologically active form. Half of the patient s total calcium is in the free ionized form. 

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