Best literature values for the pK of carbonic and phosphoric acid under physiological conditions

Jungas, Robert L.

doi:10.1016/j.ab.2005.08.020

Cited by 20 publications

(15 citation statements)

References 42 publications

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“…The experimental pK values vary according the solvent composition, buffer composition and temperature [16]. For the pI calculations of phosphopeptides in this study the values summarized in Table 1 were used.…”

Section: Conceptual Considerationsmentioning

confidence: 99%

pI‐based phosphopeptide enrichment combined with nanoESI‐MS

2007

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IEF is introduced as a new principle for enrichment and separation of phosphopeptides as obtained after digestion of phosphoproteins by trypsin. Tryptic peptides and phosphopeptides exhibit pI values, which overlap in the range of about 4-6. However, after methyl esterification of all carboxyl functions, the pI values of tryptic peptides and phosphopeptides regroup in discrete clusters. In addition, mono- and diphosphorylated peptides show different but very homogeneous pI values, with variations when internal Arg, Lys, or His residues are present. Experimentally, this new concept was applied for separation of model peptides on IPG strips pH 3-10 as used in the first dimension of 2-DE. After IEF of methyl-esterified peptides, the IPG strip was cut into pieces followed by peptide extraction, desalting and MS analysis by nanoESI-MS. Phosphopeptides were found to focus in good agreement with their calculated pI values. This analytical strategy showed a resolution of about 0.2 pI units, and thus turned out to be capable of detecting minor differences in pI values, such as those occurring between pSer, pThr and pTyr residues. Using IPG strips with a pI range of 3-10, methyl esterified nonphosphorylated tryptic peptides are concentrated in the basic part of the IPG strip or even leave the strip. Thus, efficient enrichment of phosphopeptides and their subfractionation according to pI is obtained in one step. Minor hydrolytic side reactions including deamidation of Asn and partial hydrolysis of methyl esters are observed. The results show that IEF opens attractive avenues for the further advancement of analytical phosphoproteomics.

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Section: Conceptual Considerationsmentioning

confidence: 99%

pI‐based phosphopeptide enrichment combined with nanoESI‐MS

2007

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“…Blood gas analysis was performed at 37°C with a digital pH/blood gas analyzer (Corning 178 blood pH analyzer). The concentration of HCO 3 – in plasma (P HCO 3 ) was calculated from the pH and P CO 2 using a solubility factor of 0.0301 [14]. L -Lactate and glucose were measured by enzymatic analysis [13] and insulin was measured by radioimmunoassay [15].…”

Section: Methodsmentioning

confidence: 99%

An Acute Infusion of Lactic Acid Lowers the Concentration of Potassium in Arterial Plasma by Inducing a Shift of Potassium into Cells of the Liver in Fed Rats

Cheema‐Dhadli¹,

Chong²,

Kamel³

et al. 2012

Nephron Physiol

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Background: Potassium (K⁺) input occurs after meals or during ischemic exercise and is accompanied by a high concentration of L-lactate in plasma (P_L-lactate). Methods: We examined whether infusing 100 µmol L-lactic acid/min for 15 min would lead to a fall in the arterial plasma K⁺ concentration (P_K). We also aimed to evaluate the mechanisms involved in normal rats compared with rats with acute hyperkalemia caused by a shift of K⁺ from cells or a positive K⁺ balance. Results: There was a significant fall in P_K in normal rats (0.25 mM) and a larger fall in P_K in both models of acute hyperkalemia (0.6 mM) when the P_L-lactate rose. The arterial P_K increased by 0.8 mM (p < 0.05) 7 min after stopping this infusion despite a 2-fold rise in the concentration of insulin in arterial plasma (P_Insulin). There was a significant uptake of K⁺ by the liver, but not by skeletal muscle. In rats pretreated with somatostatin, P_Insulin was low and infusing L-lactic acid failed to lower the P_K. Conclusions: A rise in the P_L-lactate in portal venous blood led to a fall in the P_K and insulin was permissive. Absorption of glucose by the Na⁺-linked glucose transporter permits enterocytes to produce enough ADP to augment aerobic glycolysis, raising the P_L-lactate in the portal vein to prevent postprandial hyperkalemia.

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“…5 shows the concentration of human insulin (the molecular weight of human insulin: 5808 g/mol) as function of distance; it is seen that the measured human insulin concentrations were much lower than the applied buffer concentrations (0.17 and 0.067 M at pH 3.00 and 7.40, respectively). The concentrations of the acidic and basic species of the phosphate buffer (pK a (H 2 PO 4 À ) = 6.790 (Jungas, 2006)) at e.g. pH 7.40 and 7.01 were calculated to 0. , respectively.…”

Section: Microenvironmental Ph Measurementsmentioning

confidence: 99%