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PubMed1990

Haemoglobin pyridoxalation in phosphate buffer: comparison of results with those obtained with Tris-HCl buffer.

Most workers studying haemoglobin solutions re-establish a P50 close to physiological values by covalent fixation of pyridoxal phosphate (PLP) using the method first described by Benesch. This is performed with deoxyhaemoglobin in a Tris-HCl buffer, considered to be necessary for transimination. To simplify the chemical procedure of the conjugation of a macromolecule to Hb-PLP we have performed the pyridoxalation in a phosphate buffer. Physico-chemical analysis of pyridoxalated haemoglobin solutions show a slight degradation of the protein, a amount of fixed PLP to the haemoglobin and a right-shift of the dissociation curve similar whether the coupling is performed in the phosphate or the Tris buffer. The pharmacological evaluation by total and isovolumic exchange transfusion in rats, of solutions prepared from both methods of pyridoxalation show identical survival times, vascular persistence and stability of the conjugates. Thus the pyridoxalation takes place with a comparable yield whatever reagent is used, proving that Tris is not essential to haemoglobin pyridoxalation.

Animals↗
PubMed1989

Development of a buffer system for dialysis of bovine spermatozoa before freezing. I. Effect of zwitterion buffers.

The effect of N-TRIS(hydroxymethyl)methyl-2-aminoetane sulfonic acid (TES); N,N BIS (2 hydroxvethyl)-2 aminoethane sulfonic acid (BES), N-2(hydroxyethyl)piperazine-N-2-ethane sulfonic acid (HEPES), morpholinopropane sulfonic acid (MOPS), and piperazine-N-N-BIS(2-ethane sulfonic acid (PIPES) solutions on dialyzed semen was studied. Each was titrated to pH 7.0 with TRIS-(hydroxymethyl)-amino methane (TRIS) solution and the osmotic pressure was adjusted to between 320 to 325 mOsm/kg. The new solutions were identified as TEST, BEST, HEPEST, MOPST and PIPEST, respectively. The solutions were used 1) alone, 2) in a composite with equal parts (V/V) of each solution and 3) in a 1:1 (V/V) combination with isosmotic trisodium citrate solution. Later, TRIS and sodium hydroxide (NaOH) were compared as titration bases for piperazine-N-N-BIS (2-ethane sulfonic acid) (PIPES) and N-Tris(hydroxymethyl)methyl-2-aminoethane sulfonic acid (TES). Ejaculates were diluted 1:10 (V/V) in extenders containing buffer, 20% egg yolk and 5% glycerol (V/V). The samples were dialyzed (1:50) during cooling for a period of 2 h. Each sample was dialyzed against the same buffer system containing 5% glycerol without egg yolk and later it was frozen in pellets. The treatments were evaluated by observation of sperm motility in fresh and thawed semen samples. The latter were also analyzed by electronic count of cells that passed through the Sephadex column. Sperm survival was higher in PIPEST (PIPES titrated with TRIS) or the composite buffer, and the inclusion of 50% sodium citrate (Na citrate) improved significantly (P<0.05) sperm motility in fresh and frozen-thawed semen samples. There was no difference (P>0.05) between the titration bases. In the second experiment, sperm survival was superior in extenders containing PIPEST (P<0.05) than in those containing TEST independently of the inclusion of Na citrate.

Journal Article↗
PubMed1997

Avoiding interferences from Good's buffers: A contiguous series of noncomplexing tertiary amine buffers covering the entire range of pH 3-11.

Of the 20 well-known buffers proposed by Good, all but 3 form metal ion complexes which can result in serious interferences, particularly in protein analyses. The structural features responsible for such complex formation have been identified. Based on a mechanistic analysis of the metal complexation process, it is proposed that tertiary amine compounds, having N-substituents which are ethyl or larger, are sterically inaccessible for initial bond formation with solvated metal ions in aqueous solution. Thus, in the absence of donor atoms on the alpha-, beta-, or gamma-carbons, metal complexation cannot proceed. The proposed noncomplexing compounds include Good's 3 noncomplexing buffers (Mes, Mops, Pipes) plus six related species. Mixed-mode acid dissociation constants (hydrogen ion in terms of activity, conjugate acid-base species in molar concentrations) have been determined for all compounds in their protonated form at 25 degrees C, mu = 0.10 M (NaNO3). The values for four compounds in this series are reported here for the first time: viz., N,N'-diethylpiperazine for which log Ka1m = 4.67 +/- 0. 03 and log Ka2m = 8.83 +/- 0.02; N,N,N',N'-tetraethylmethylenediamine for which log Ka1m < 1 and log Ka2m = 11.01 +/- 0.03; N,N'-diethyl-N,N'-bis(3-sulfopropyl)ethylenediamine for which log Ka1m = 5.75 +/- 0.03 and log Ka2m = 9.37 +/- 0.02; and piperazine-N,N'-bis(2-ethanesulfonic acid) (Pipes) for which log Ka1m = 2.81 +/- 0.01 (the value of log Ka2m having been previously reported).

Amines↗
PubMed1991

Interference of Good's buffers and other biological buffers with protein determination.

Interference of low concentrations of Hepes and other buffers commonly used in protein determination was studied. The data show that some of these buffers interfere to differing degrees with protein determination according to the Lowry method. A study of the structure-interference relationship suggests that the group ethanolamine is involved in this interference. No interference was observed when protein was measured using bicinchonic acid at the same concentration as the Lowry reagent.

Buffers↗
PubMed1982

Comparison of intra-and extracellular buffering of clinically used buffer substances: tris and bicarbonate.

A large and important group of acid-base disturbances are the metabolic acidoses. In general, every type of metabolic acidosis can be treated with infusion of base when the underlying cause of the disturbances is removed. In our medical centers, the use of tris and bicarbonate is common. For a long time they were competitive agents and until now it was not possible to decide by available clinical methods which of these substances was more suitable for correction of metabolic acidosis. The intracellular pH of the whole rat (mean lcf-pH) was determined from the distribution of 14C labelled DMO (5,5-dimethyl-2,4-oxazolidinedione) and monitored for 6 h following intravenous application of tris or sodiumbiarbonate in a dose of 10 mmol per kg body mass. Arterial plasma pH and PCO2 were also measured. To determine and compare the effectiveness of the two buffer substances, intra- and extracellular bicarbonate were calculated from the Henderson-Hasselbalch equation. It was found that the buffering following bicarbonate infusion is more effective in both body compartments. Sodiumbicarbonate should be preferred in daily practice.

Acidosis↗
PubMed2006

Chiral separation of synthetic vicinal diol compounds by capillary zone electrophoresis with borate buffer and beta-cyclodextrin as buffer additive.

The investigation on capillary electrophoretic enantioseparation of six synthetic compounds containing vicinal diol groups has been undertaken to acquire the optimum conditions using native beta-cyclodextrin (beta-CD) as chiral selector and borate as a background electrolyte. The separation was carried out in an uncoated capillary (58.5 cm x 75 microm i.d., effective length 48.5 cm) and the effects of several important factors were investigated in detail. The results showed that beta-CD as a chiral selector exhibited good enantioselectivity and that the enantioseparation was greatly influenced by the structure of the diols, the borate concentration and the buffer pH. The optimum performance was obtained for the chiral vicinal diols under the conditions of 200 mM borate buffer of pH 9.8 containing 1.7% beta-CD at an applied voltage of 15 kV and a capillary temperature of 20 degrees C. Under the conditions, four diols were baseline separated with fast analysis time and the good theoretical plate numbers (above 10 x 10(4)) and favorable migration-time reproducibilities (RSDs below 3.0%) were obtained. The separation results were satisfactory.

Borates↗
PubMed1998

Pain at the injection site of subcutaneously administered erythropoietin: phosphate-buffered epoetin alpha compared to citrate-buffered epoetin alpha and epoetin beta.

Patients may complain of pain at the injection site after subcutaneous (s.c.) administration of erythropoietin (EPO). Local pain due to s.c. EPO into the thigh was evaluated in 60 hemodialysis patients in a double-blind, placebo-controlled study. Identical volumes and concentrations (2000 IU in 0.5 ml) of phosphate-buffered epoetin-alpha (EPO-alpha ph), citrate-buffered epoetin-alpha (EPO-alpha ci) and epoetin-beta (EPO-beta) were compared to 0.5 ml of 0.9% saline (SAL), used as placebo. The patients received the 4 injections at the same occasion. For pain evaluation, a verbal scale ranging from no pain (0) to extremely painful (5) and a 10 cm ungraduated visual analogue score (VAS) (0 = no pain, 10 = maximal pain) were used. Treatment acceptance was assessed (yes/no) and expressed as a percentage of the population. Ranking of the preparations from 1 to 4 according to increasing local discomfort was performed. Median verbal pain scores and interquartile ranges were 1.0 (0-2) for SAL, 0.0 (0-2) for EPO-beta, 1.5 (0-3) for EPO-alpha ph (p < or = 0.05 vs SAL and EPO-beta) and 3.0 (2-4) for EPO-alpha ci (p < or = 0.001 vs EPO-alpha ph). VAS was 0.9 (0.5-2.5) for SAL, 0.9 (0.4-2.4) for EPO-beta, 2.7 (0.8-5.7) for EPO-alpha ph (p < or = 0.001 vs SAL and EPO-beta) and 4.2 (1.7-6.4) for EPO-alpha ci (p < or = 0.001 vs EPO-alpha ph). Treatment acceptance was 73% for SAL, 78% for EPO-beta, 60% for EPO-alpha ph (p < or = 0.05 vs EPO-beta) and 32% for EPO-alpha ci (p < or = 0.05 vs EPO-alpha ph). Ranking was 2 (1-3) for SAL, 2 (1-2) for EPO-beta, 3 (1-4) for EPO-alpha ph (p < or = 0.05 vs SAL and EPO-beta) and 4 (3-4) for EPO-alpha ci (p < or = 0.05 vs SAL and EPO-beta) and 4 (3-4) for EPO-alpha ci (p < or = 0.001 vs EPO-alpha ph). In conclusion, s.c. EPO-alpha ph is better accepted than s.c. EPO-alpha ci. However, s.c. EPO-beta is less painful.

Aged↗
PubMed1998

Calcium buffering capacity of neuronal cell cytosol measured by flash photolysis of calcium buffer NP-EGTA.

N1E-115 mouse neuroblastoma cells were injected with a calcium buffer/indicator solution to allow both ratiometric measurement of free calcium concentration and the release of calcium ions upon UV flash. The solution contained sulforhodamine, a marker dye used to estimate the volume injected; fluo-3, a calcium indicator, and NP-EGTA, a high affinity calcium-selective buffer that is converted by UV flash to products with negligible calcium affinity. The calcium increase recorded upon UV irradiation (Delta[Ca2+]i) was small for small injection volumes, increased with larger injection volumes, but approached a plateau at the largest injection volumes. From this relation we estimate the buffering capacity of the cytosol as 1700 ions bound per ion free.

Animals↗
PubMedDate not supplied

Comparative studies on the interaction of proteins with a polydimethylsiloxane elastomer. I. Monolayer protein capture capacity (PCC) as a function of protein pl, buffer pH and buffer ionic strength.

Polydimethylsiloxane (PEP) is widely used in medical prostheses and therefore is in contact with plasma and secretory proteins. Two pair of globular proteins, lactoferrin (Lf) and transferrin (Trf), and bovine IgG1 and IgG2a, which differ substantially between pair members in their pl, were used to study the interaction of a PEP widely used in breast implants and soluble protein. Studies were done using iodinated proteins over a concentration range that resulted in an apparent protein monolayer. Secondary incubations with dilute protein solutions were needed to form the monolayer on PEP, possibly as a consequence of micro air bubbles trapped on its highly textured surface as shown by atomic force microscopy. Immunoassay quality polystyrene microtiter wells were used as controls. Adsorption studies were routinely performed at pH 4, 7 and 10 and at ionic strengths corresponding to 0.95, 9.5 and 90.0 mS. The protein capture capacity (PCC) of PEP for Lf and Trf was optimal at physiological pH and ionic strength and comparable under these conditions to that of Immulon 2 (Imm 2) microtiter wells. While increasing the ionic strength and pH further increases the PCC of Imm 2 for Lf and Trf, this markedly lowered the PCC of PEP for these proteins suggesting that initial polar interactions may precede subsequent hydrophobic bonding to PEP. This was tested using a hydrophilic variant of PEP, which when tested in a 90.0 mS buffer, showed a > five-fold lower PCC at neutral and alkaline pH. The greatly reduced PCC of the hydrophilic variant might also suggest that hydrophilic variants of silicone would be more biocompatible than those currently used. The PCC of PEP for the IgGs was less than that of Imm 2 but still optimal at physiological conditions. Consistent with the data on Lf/Trf, PCC progressively decreased with increasing ionic strength at alkaline pH. Differences in pl between the protein pairs had only a marginal effect on the PCC of PEP. Monolayer adsorption on both PEP and Imm 2 was slowly reversible and greater in the presence of free ligand (< 2% in 16 h) suggesting that the process follows Mass Law principles. However, even in the presence of non-ionic detergent and free ligand, 85-90% remained bound on either surface. Thus, desorption of proteins in the monolayer should not complicate subsequent immunochemical studies conducted on adsorbed monolayers.

Adsorption↗
PubMed1999

Aspirin absorption rates and platelet inhibition times with 325-mg buffered aspirin tablets (chewed or swallowed intact) and with buffered aspirin solution.

Large clinical trials such as the second International Study of Infarct Survival routinely gave patients with myocardial infarction a chewed aspirin, yet there are no data to show whether chewing of aspirin is better, or worse, than swallowing a whole tablet. We performed a randomized, placebo-controlled study to determine whether chewing aspirin or administering it in solution accelerates its absorption and antiplatelet activity. On separate days, 12 fasting volunteers ingested 325 mg of buffered aspirin, either by chewing a tablet for 30 seconds before swallowing it with 4 ounces of water, swallowing a whole tablet with 4 ounces of water, or drinking 4 ounces of Alka Seltzer. Frequent blood samples were obtained for serum aspirin, salicylate, and thromboxane B2 (TxB2) concentrations. With all formulations of aspirin, serum TxB2 decreased 50% when the plasma aspirin concentration reached approximately 1,000 ng/ml. A 50% and 90% decrease in serum TxB2 occurred more quickly after chewing a tablet than after a tablet was swallowed whole. For example, the t 50% for serum TxB2 inhibition was 5.0 +/- 0.6 minutes with the chewed tablet versus 12.0 +/- 2.3 minutes when the tablet was swallowed (p = 0.01). A 50% decrease in serum TxB2 occurred 7.6 +/- 1.2 minutes after Alka Seltzer solution (p = 0.04 vs chewing a tablet; p = 0.13 vs swallowing a whole tablet). Chewing an aspirin tablet is the most effective way of accelerating absorption of aspirin into the blood and shortening the time required for an antiplatelet effect.

Absorption↗
PubMed1999

Hydroquinone as a buffer additive for suppression of bubbles formed by electrochemical oxidation of the CE buffer at the outlet electrode in capillary electrophoresis/electrospray ionization-mass spectrometry.

Hydroquinone was found to suppress bubble formation at the outlet electrode of a sheathless capillary electrophoresis/electrospray ionization-mass spectrometer by replacing the oxidation of water (2H2O(1)<-->O2(g) + 4H+ + 4e) with that of more easily oxidized hydroquinone (hydroquinone<-->p-benzoquinone + 2H+ + 2e). Formation of p-benzoquinone replaces the formation of oxygen gas, effectively suppressing gas bubble formation. Several electrode materials, including platinum, gold-coated stainless steel, and stainless steel wires, were tested. However, hydroquinone suppressed bubbles only at the platinum electrode. Combination of the in-capillary electrode sheathless interface using platinum wire, hydroquinone as a buffer additive, and pressure programming at the inlet of the capillary electrophoresis provided a rugged high efficiency interface for analysis of protein digests using CE/ESI-MS.

Buffers↗
PubMed2001

Comparison of the biocompatibility of phosphate-buffered saline alone, phosphate-buffered saline supplemented with glucose, and dianeal 3.86%.

OBJECTIVE: We compared the effects of intraperitoneal infusion of phosphate-buffered saline (PBS, pH 7.4), of PBS supplemented with 3.86% glucose (G), and of standard dialysis solution [Dianeal 3.86%: Baxter Healthcare Corporation, Deerfield, IL, U.S.A. (D)] on intraperitoneal inflammation in dialyzed rats. METHODS: After catheter implantation, rats were infused on day 1 with PBS, on day 3 with PBS+G, on day 5 with D, and on day 7 again with PBS (PBS-2). After a 4-hour dwell, dialysate samples were collected and analyzed. RESULTS: All dialysate parameters studied [dialysate cell count, neutrophil:macrophage ratio (Ne:Ma), and total protein], except tumor necrosis factor alpha (TNFalpha), were comparable during both PBS infusions. During dialysis with PBS+G, the inflammatory response was suppressed as compared with the first dialysis with PBS (cell count, p < 0.001; Ne:Ma, p < 0.05; TNFalpha, p < 0.001; total protein, p < 0.001). During dialysis with D, peritoneal inflammatory parameters were further suppressed (cell count, p < 0.001 vs PBS and p < 0.01 vs PBS+G; Ne:Ma, p < 0.001 vs PBS and p < 0.05 vs PBS+G; TNFalpha, p < 0.001 vs PBS and p < 0.001 vs PBS+G; total protein, p < 0.001 vs PBS and p < 0.01 vs PBS+G). CONCLUSIONS: Hypertonicity of the dialysis fluid suppresses intraperitoneal inflammatory parameters in rats. The suppression was even more severe when Dianeal 3.86% was used. That finding could be due to the low pH and presence of GDPs in the fluid.

Animals↗
PubMed1989

Synthesis of buffers for generating immobilized pH gradients. II: Basic acrylamido buffers.

Six basic acrylamido buffers, for isoelectric focusing in immobilized pH gradients, are described: a strong titrant (pK greater than 12), QAE-acrylamide, and five weaker bases, namely: 2-morpholinoethyl acrylamide (pK 6.2), 3-morpholinopropyl acrylamide (pK 7.0), N,N-dimethyl aminoethyl acrylamide (pK 8.5), N,N-dimethyl aminopropyl acrylamide (pK 9.3) and N,N-diethyl aminopropyl acrylamide (pK 10.3). Their synthesis and general properties are described.

Acrylamides↗
PubMed1989

Synthesis of buffers for generating immobilized pH gradients. I: Acidic acrylamido buffers.

Five acidic acrylamido buffers for isoelectric focusing in immobilized pH gradients, are described: a strong titrant (pK 1.0) 2-acrylamido-2-methyl propane sulphonic acid and four weaker acids, namely 2-acrylamido glycolic acid (pK 3.1), N-acryloil glycine (pK 3.6), 3-acrylamido propanoic acid (pK 4.4) and 4-acrylamido butyric acid (pK 4.6). Their synthesis and general properties are described.

Acrylamides↗
PubMed2006

Carbohydrate-based switch-on molecular sensor for Cu(II) in buffer: absorption and fluorescence study of the selective recognition of Cu(II) ions by galactosyl derivatives in HEPES buffer.

[graph: see text] 1-(Beta-D-galactopyranosyl-1'-deoxy-1'-iminomethyl)-2-hydroxynaphthalene (L1), possessing an ONO binding core, was found to be selective for Cu2+ ions in N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid] buffer, at concentrations < or = 580 ppb, at physiological pH by eliciting switch-on behavior, whereas the other ions, viz., Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+, and Cd2+, caused no significant change in the fluorescence. Whereas the binding characteristics were ascertained by absorption spectroscopy, the species formed were shown by Q-TOF ES MS.

Cations↗