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PubMed2002

Retention of ionizable compounds on HPLC. 12. The properties of liquid chromatography buffers in acetonitrile-water mobile phases that influence HPLC retention.

The addition of acetonitrile to aqueous buffers to prepare RP HPLC mobile phases changes the buffer properties (pH and buffer capacity). This variation is studied for ace tate, phosphate, phthalate, citrate, and ammonia buffers in acetonitrile-water mixtures up to 60% in acetonitrile (v/v). Equations are proposed to relate pH and buffer capacity change of these buffers to the initial aqueous pH value and to the volume fraction of acetonitrile added. It is demonstrated that the pH change of the buffer depends not only on the initial aqueous pH of the buffer and on the percentage of acetonitrile added but also on the particular buffer used. The proposed equations allow an accurate prediction of this ionization for the studied buffers. Since the retention of acid/base compounds shows a strong dependence of their degree of ionization, the equations are used to predict the change in this ionization with addition of acetonitrile when the RP HPLC mobile phase is prepared. This prediction allows estimation of the retention of an acid/base compound in a particular acetonitrile-water buffered mobile phase.

Journal Article↗
PubMed1984

The effect of two different buffers on the high affinity 3H-ethylketocyclazocine and 3H-SKF10047 binding to guinea pig brain membranes.

In vitro mu and delta opioid receptor binding is known to be influenced by ions. High affinity 3H-SKF10047 and 3H-ethylketocyclazocine binding sites are found in brain membranes and postulated to be similar to mu opioid receptor binding. To investigate this postulate, we have studied how the high affinity binding of 3H-SKF10047, 3H-ethylketocyclazocine, a tritiated mu agonist, mu antagonist and delta agonist is altered when the radioreceptor binding assay incubation buffer is changed. The binding of 3H-ethylketocyclazocine and the mu antagonist (3H-naloxone) is highest in isotonic HEPES buffer, while the binding of the mu (3H-dihydromorphine) and delta (3H-D-ala-D-leu-enkephalin) agonist is highest in hypotonic Tris-HCl buffer. 3H-SKF10047 binding is similar in the two buffers. The inhibition of 3H-ethylketocyclazocine, 3H-SKF10047 and tritiated mu and delta opioid ligands by seven unlabeled ligands is then compared in the two buffers. Morphine chloride is a more potent inhibitor of 3H-ethylketocyclazocine binding and tritiated mu ligand in hypotonic Tris-HCl buffer than in isotonic HEPES buffer. The potency of naloxone, nalorphine, SKF10047, D-ala-D-leu-enkephalin, cyclazocine and phencyclidine in inhibiting 3H-ethylketocyclazocine binding is independent of the buffer system. None of the seven unlabelled substances change potency with buffer change when inhibiting the 1.2 nM 3H-SKF10047 binding. In sum our results show that 1 nM 3H-ethylketocyclazocine binding is influenced by buffer change in a manner very similar to mu ligand binding, while the 1.2 nM 3H-SKF10047 binding is only slightly influenced by buffer change and therefore different from mu ligand binding.

Analgesics, Opioid↗
PubMed2004

High-activity biocatalysts in organic media: solid-state buffers as the immobilisation matrix for protein-coated microcrystals.

Recently, we reported a new high-activity biocatalyst for use in organic media termed protein-coated microcrystals (PCMC) (Kreiner et al. [2001] Chem Commun 12:1096-1097). These novel particles consist of water-soluble micron-sized crystalline particles coated with the given biocatalyst(s) and are prepared in a one-step rapid dehydration process. In this study we extended the choice of immobilisation matrix from a simple inorganic salt, K(2)SO(4), to other compounds, both inorganic and zwitterionic, that act as solid-state buffers for biocatalysis in organic media. The catalytic activity of serine proteases subtilisin Carlsberg (SC) and alpha-chymotrypsin (CT) were significantly increased when coated onto the surface of solid-state buffers, as measured in acetonitrile/1wt% H(2)O. SC-PCMC with both organic and inorganic buffer carriers (Na-AMPSO, Na(2)CO(3), and NaHCO(3)) showed a 3-fold greater activity than that observed when using the unbuffered system (PCMC-SC/K(2)SO(4)). In comparison with freeze-dried preparations, this represents an approximately 3,000-fold increase in catalytic activity. Importantly, there is no improvement in catalytic activity upon external addition of any of the solid-state buffers to the reaction mixture. When acting in a solid-state buffer capacity, good buffering capacity was observed with SC-PCMC (3 wt% protein loading) prepared from a 1:1 mixture of AMPSO and AMPSO-Na. Alternatively, increasing the amount of solid-state buffer in the system allows improvement of the buffering. This can be achieved either by decreasing the protein loading of the SC/Na-AMPSO-PCMC or by addition of further external solid-state buffer to the reaction mixture. The catalytic activity of lipase-PCMC prepared from solid-state buffers was found less responsive to immobilisation.

Animals↗
PubMed2000

Protein denaturation during freezing and thawing in phosphate buffer systems: monomeric and tetrameric beta-galactosidase.

During freezing in sodium and potassium phosphate (NaP and KP) buffer solutions, changes in pH may impact the stability of proteins. Since the degradation pathways for the model proteins, monomeric and tetrameric beta-galactosidase (beta-gal), chosen for this study are governed by conformational changes (i.e., physical instability) as opposed to chemical transformations, we explored how the stresses of freezing and thawing alter the protein's native structure and if preservation of the native conformation during freeze-thawing is a requisite for optimal recovery of activity. During freezing in NaP buffer, a significant pH decrease from 7.0 to as low as 3.8 was observed due to the selective precipitation of the disodium phosphate; however, the pH during freezing in KP buffer only increased by at most 0.3 pH units. pH-induced inactivation was evident as seen by the lower recovery of activity when freeze-thawing in NaP buffer as compared to KP buffer for both sources of beta-gal. In addition, we investigated the effects of cooling rate and warming rate on the recovery of activity for monomeric and tetrameric beta-gal. Optimal recovery of activity for the NaP samples was obtained when the processing protocol involved a fast cool/fast warm combination, which minimizes exposure to acidic conditions and concentrated solutes. Alterations in the native secondary structure of monomeric beta-gal as measured by infrared spectroscopy were more significant when freezing and thawing in NaP buffer as opposed to KP buffer. Conformational and activity analyses indicate that pH changes during freezing in NaP buffer contribute to denaturation of beta-gal. These results suggest that proteins formulated in NaP buffer should be frozen and thawed rapidly to minimize exposure to low pH and high buffer salts.

Buffers↗
PubMed1999

Buffer effects on EcoRV kinetics as measured by fluorescent staining and digital imaging of plasmid cleavage.

We have developed a protocol to quantify polymer DNA cleavage which replaces the traditional radiolabeling and scintillation counting with fluorescent staining and digital imaging. This procedure offers high sensitivity, speed, and convenience, while avoiding waste and error associated with traditional 32P radiolabeling. This protocol was used to measure cleavage of pBR322 plasmid DNA by EcoRV, a type II restriction enzyme. EcoRV was found to exhibit an order of magnitude difference in binding in two apparently similar buffers used in previous investigations. To determine the origin of this effect, we measured reaction kinetics in buffers of different chemical nature and concentration: Tris, bis-Tris propane, Tes, Hepes, and cacodylate. We found that buffer concentration and identity had significant effects on EcoRV reaction velocity through large changes in specific binding and nonspecific binding (reflected in the Michaelis constant Km and the dissociation constant for nonspecific binding Kns). There were only small changes in Vmax. The source of the buffer effect is the protonated amines common to many pH buffers. These buffer cations likely act as counterions screening DNA phosphates, where both the protonated buffer structure and concentration affect enzyme binding strength. It appears that by choosing anionic buffers or zwitterionic buffers with a buried positive charge, buffer influence on the protein binding to DNA can be largely eliminated.

Buffers↗
PubMed1983

Peritubular buffering power and luminal acidification in proximal convoluted tubules of the rat.

Proximal tubular acidification was studied varying peritubular buffer concentration as well as the nature of the main peritubular buffer system. Two buffer systems were used: phosphate which varied between 1 and 20 mM, and glycodiazine, at 5 and 20 mM. Luminal perfusate was always 20 mM phosphate Ringer's. Acidification half times increased as peritubular buffer concentration decreased, independently of the nature of the buffer. At 1 mM phosphate, net H-ion flux (JH +) was 0.53 nmol . cm-2 . s-1; at 5 mM it was 0.73 nmol . cm-2 . s-1 and at 20 mM, 0.97 nmol . cm-2 . s-1. When the peritubular buffer was glycodiazine, JH + was 0.77 nmol . cm-2 . s-1 at 5 mM peritubular buffer concentration and 0.99 nmol . cm-2 . s-1 at 20 mM. Acetazolamide (10(-4) M) and DIDS (10(-4) M) both abolished the effect of peritubular buffer concentration changes on acidification half times. It was shown that these effects were related to the capacity of the peritubular buffer to attenuate changes in peritubular pH as consequence of base transfer by the peritubular membrane. Peritubular buffering power could act limiting intracellular pH increments consequent to luminal H-ion secretion.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2006

Ferritin-catalyzed consumption of hydrogen peroxide by amine buffers causes the variable Fe2+ to O2 stoichiometry of iron deposition in horse spleen ferritin.

Ferritin catalyzes the oxidation of Fe2+ by O2 to form a reconstituted Fe3+ oxy-hydroxide mineral core, but extensive studies have shown that the Fe2+ to O2 stoichiometry changes with experimental conditions. At Fe2+ to horse spleen ferritin (HoSF) ratios greater than 200, an upper limit of Fe2+ to O2 of 4 is typically measured, indicating O2 is reduced to 2H2O. In contrast, a lower limit of Fe2+ to O2 of approximately 2 is measured at low Fe2+ to HoSF ratios, implicating H2O2 as a product of Fe2+ deposition. Stoichiometric amounts of H2O2 have not been measured, and H2O2 is proposed to react with an unknown system component. Evidence is presented that identifies this component as amine buffers, including 3-N-morpholinopropanesulfonic acid (MOPS), which is widely used in ferritin studies. In the presence of non-amine buffers, the Fe2+ to O2 stoichiometry was approximately 4.0, but at high concentrations of amine buffers (0.10 M) the Fe2+ to O2 stoichiometry is approximately 2.5 for iron loadings of eight to 30 Fe2+ per HoSF. Decreasing the concentration of amine buffer to zero resulted in an Fe2+ to O2 stoichiometry of approximately 4. Direct evidence for amine buffer modification during Fe2+ deposition was obtained by comparing authentic and modified buffers using mass spectrometry, NMR, and thin layer chromatography. Tris(hydroxymethyl)aminomethane, MOPS, and N-methylmorpholine (a MOPS analog) were all rapidly chemically modified during Fe2+ deposition to form N-oxides. Under identical conditions no modification was detected when amine buffer, H2O2, and O2 were combined with Fe2+ or ferritin separately. Thus, a short-lived ferritin intermediate is required for buffer modification by H2O2. Variation of the Fe2+ to O2 stoichiometry versus the Fe2+ to HoSF ratio and the amine buffer concentration are consistent with buffer modification.

Amines↗
PubMed1991

Inhibition, survival and growth of Listeria monocytogenes on poultry as influenced by buffered lactic acid treatment and modified atmosphere packaging.

The effect of the treatment with various concentrations (2%, 5% and 10% w/v) of lactic acid/sodium lactate buffer (pH 3.0), modified atmosphere (MAP) packaging (90% CO2 and 10% O2) and 10% (w/v) lactic acid/sodium lactate buffer (pH 3.0) combined with MAP on Listeria monocytogenes Z7 serotype 1 and on the shelf life of chicken legs stored at 6 degrees C was investigated. The initial contamination level of L. monocytogenes on the chicken legs surface was 8.3 x 10(2) cfu/cm2 of skin. After 2 days of storage at 6 degrees C the number of L. monocytogenes on legs treated with 2%, 5%, 10% lactic acid/sodium lactate buffer (pH 3.0) and 10% lactic acid/sodium lactate buffer (pH 3.0) combined with MAP was significantly lower than the initial number of L. monocytogenes. Later, growth of L. monocytogenes was observed. After 13 days of storage at 6 degrees C the number of L. monocytogenes on legs treated with 10% lactic acid/sodium lactate buffer (pH 3.0) combined with MAP was still similar to the initial number. Legs treated with 2%, 5%, 10% lactic acid/sodium lactate buffer (pH 3.0), MAP and 10% lactic acid/sodium lactate buffer (pH 3.0) combined with MAP, have a shelf life at 6 degrees C of respectively 8, 9, 10, 13 and 17 days. This means a prolongation of 2, 3, 4, 7 and 11 days, respectively for storage at 6 degrees C. The antimicrobial effect of lactic acid buffer systems (pH 3.0) increased with increasing concentrations of lactic acid in the buffered system. The best results were obtained by the combined use of 10% acid/sodium lactate buffer (pH 3.0) and MAP.

Analysis of Variance↗
PubMed2005

Influence of pH, buffer species, and storage temperature on physicochemical stability of a humanized monoclonal antibody LA298.

The purpose of this work is to study the effect of pH, buffer species, and temperature on the physicochemical stability of a humanized monoclonal antibody LA298. The study was carried out in solution state of the antibody in the presence of different buffer species at different pH values and storage temperature. No significant changes in total protein content were observed for any of the solutions with different buffers at different pH values when stored for 8 weeks at both 5 degrees C and 25 degrees C or at 37 degrees C for 1 week. Known asparagines (Asn55) deamidation of LA298 was found to be dependent on pH, buffer type, and temperature. The estimated rate constant of the double heavy chain Asn55 deamidation in phosphate buffer at pH 6.5 and 7.0 was much higher than that in citrate buffer under the same storage conditions. However, comparable results were obtained for single heavy chain Asn55 deamidation in citrate and phosphate buffer. Aggregation of LA298 was not significant for samples at different pH values, buffers, and temperatures as the monomer of LA298 decreased dramatically over time. Less decrease in monomeric LA298 was observed in citrate buffer, pH 5.0-5.5. In conclusion, to minimize deamidation and loss of LA298 monomer, it is important to optimize its solution pH, buffer species, and storage temperature.

Antibodies, Monoclonal↗
PubMed2006

Quantitative assessment for stimulated saliva flow rate and buffering capacity in relation to different ages.

OBJECTIVES: To evaluate salivary flow rate and buffering capacity using a quantitative pH measurement among three broad age groups. METHODS: The population consisting of 117 patients was classified into three age groups: young, middle-aged, and elderly group. The volume of stimulated saliva after chewing gum was measured. Saliva samples were titrated with 0.1N HCl to evaluate the buffering capacity. Saliva pH change was measured directly using a hand-held pH meter. At the point of 50 microL of titrated HCl, individual salivary buffering capacities were ranked into one of the following three categories; high buffering capacity (above pH 5.5), medium buffering capacity (from pH 5.5 to 4.5), and low buffering capacity (below pH 4.5). RESULTS: Chi(2)-test showed that the proportional distribution of individuals in the three buffering capacity groups was not statistically different among the age groups (p>0.05). One-way ANOVA and Tukey's HSD test showed the flow rate of stimulated whole saliva in the young group was significantly greater than that of the middle-aged and elderly groups (p<0.05). Two-way ANOVA showed there was no significant interaction between the independent variables buffering capacity and age group (F=0.419, p=0.7950). One-way ANOVA and Tukey's HSD test indicated the flow rate showed significant differences among the three age and buffering capacity groups. CONCLUSIONS: Although a limited number of subjects were investigated in this study, the quantitative saliva assessment is useful as a screening method for different ages to identify patients with a low saliva flow rate and/or buffering capacity.

Adult↗
PubMed1994

Intrinsic cytosolic calcium buffering properties of single rat cardiac myocytes.

Intracellular passive Ca2+, buffering was measured in voltage-clamped rat ventricular myocytes. Cells were loaded with indo-1 (K+ salt) to an estimated cytosolic concentration of 44 +/- 5 microM (Mean +/- SEM, n = 5), and accessible cell volume was estimated to be 24.5 +/- 3.6 pl. Ca2+ transport by the sarcoplasmic reticulum (SR) Ca-ATPase and sarcolemmal Na-Ca exchange was inhibited by treatment with thapsigargin and Na-free solutions, respectively. Extracellular [Ca2+] was maintained at 10 mM and, in some experiments, the mitochondrial uncoupler "1799" was used to assess the degree of mitochondrial Ca2+ uptake. To perform single cell titrations, intracellular Ca2+ ([Ca2+]i) was increased progressively by a train of depolarizing voltage clamp pulses from -40 to +10 mV. The total Ca2+ gain with each pulse was calculated by integration of the Ca current and then analyzed as a function of the rapid change in [Ca2+]i during the pulse. In the range of [Ca2+]i from 0.1 to 2 microM, overall cell buffering was well described as a single lumped Michaelis-Menten type species with an apparent dissociation constant, KD, of of 0.63 +/- 0.07 microM (n = 5) and a binding capacity, Bmax, of 162 +/- 15 mumol/l cell H2O. Correction for buffering attributable to cytosolic indo-1 gives intrinsic cytosolic Ca2+ buffering parameters of KD = 0.96 +/- 0.18 microM and Bmax = 123 +/- 18 mumol/l cell H2O. The fast Ca2+ buffering measured in this manner agrees reasonably with the characteristics of known rapid Ca buffers (e.g., troponin C, calmodulin, and SR Ca-ATPase), but is only about half of the total Ca2+ buffering measured at equilibrium. Inclusion of slow Ca buffers such as the Ca/Mg sites on troponin C and myosin can account for the differences between fast Ca2+ buffering in phase with the Ca current measured in the present experiments and equilibrium Ca2+ buffering. The present data indicate that a rapid rise of [Ca2+]i from 0.1 to 1 microM during a contraction requires approximately 50 microM Ca2+ to be added to the cytosol.

Animals↗
PubMed1996

Effects of buffer concentration on voltage-gated H+ currents: does diffusion limit the conductance?

The single-channel proton conductance of the voltage-gated H(+)-selective channel, like that of the F0 component of the H(+)-ATPase, is nearly constant over a wide range of pH encompassing the physiological range. To examine the possible contributions of buffer diffusion and buffer-channel proton transfer reactions to this phenomenon, the effects of buffer concentration on voltage-activated H+ currents were explored in voltage-clamped rat alveolar epithelial cells. Changes in the external buffer concentration ([B]o), evaluated using the whole-cell configuration, had only small effects on H+ currents (IH). Lowering [B]o from 100 to 1 mM did not alter the voltage-activation curve or reversal potential (Vrev) but reduced IH, typically by 10-30%. Changes in internal buffer concentration ([B]i), examined in inside-out patches, usually altered IH more distinctly and subtly changed the kinetics. Overall, the effects of changing buffer concentration were small and subtle. The maximum attenuation of the single-channel H+ current at 1 mM buffer was estimated to be approximately 20% at either mouth of the H+ channel. Therefore, the rate-determining step in H+ permeation is neither deprotonation of buffer at the inner mouth of the channel nor protonation of buffer at the external surface. Evidently the rate of H+ permeation through the channel is itself small enough that diffusion of buffer in bulk solution does not directly limit the conductance significantly.

Animals↗
PubMed1997

Osmotic agents and buffers in peritoneal dialysis solution: monocyte cytokine release and in vitro cytotoxicity.

Peritonitis remains a major problem in peritoneal dialysis. The incidence of peritonitis may be reduced by the use of more "biocompatible" peritoneal dialysis solutions that do not impair local host defense mechanisms, such as occurs with conventional lactate-buffered glucose solutions. In the present study, we investigated the use of bicarbonate and lactate as buffer systems and glucose, amino acids, and glucose polymer as osmotic agents on specific cellular functions of isolated fresh blood monocytes in vitro. The bicarbonate-buffered solutions had a physiologic pH (7.0 to 7.6). Lactate-buffered solutions were tested with a pH between 5.5 and 7.3. RPMI 1640 (Roswell Park Memorial Institute, supplied by Biochrom, Berlin, Germany) and phosphate-buffered saline were used as control mediums. The test solutions were incubated with 200,000 monocytes/mL for 45 minutes followed by a 1:1 mix with RPMI 1640 (with supplements) during a 24- or 4-hour tetrazolium bromide test (MTT test) recovery period. Constitutive and lipopolysaccharide (LPS)-stimulated release of interleukin-1beta (IL-1beta) and IL-6 in the supernatants as parameters of cellular host defense and lactate dehydrogenase concentrations and MTT-formazan production as parameters for cell cytotoxicity were measured. Significantly higher IL-6 and IL-1beta release was found in the bicarbonate-buffered solutions, both under basal conditions and after LPS stimulation, compared with the lactate-buffered solutions (LPS stimulation: 1% amino acids/34 mmol/L bicarbonate, IL-1beta: 1,166 +/- 192 pg/mL; 1.5% glucose/34 mmol/L bicarbonate, IL-1beta: 752 +/- 107 pg/mL; 1.5% glucose/35 mmol/L lactate/pH 5.5, IL-1beta: 174 +/- 51 pg/mL). Some of these differences could even be detected in spent dialysate after a 6-hour dwell in continuous ambulatory peritoneal dialysis patients (n = 10). A lower degree of cellular cytotoxicity (lactate dehydrogenase activity) and better-preserved metabolic activity (MTT test) also were found for the bicarbonate-buffered solutions. Amino acids (1%) proved to be comparable to glucose (1.5%) as an osmotic agent at a neutral pH with regard to LPS-stimulated cytokine release and cytotoxicity. The incubation with a glucose polymer solution (7.5% glucose polymer in phosphate-buffered saline, pH 7.3) resulted in a significantly lowered cytokine release (LPS stimulation: IL-1beta, 69 +/- 19 pg/mL) compared with the other solutions with neutral pH (P < 0.01). These results suggest that bicarbonate as a buffer provided better biocompatibility with regard to mononuclear cytokine release and viability compared with lactate. Amino acids and glucose were equivalent to these parameters at a physiologic pH. The glucose polymer solution, however, was associated with a marked depression of cytokine release.

Amino Acids↗
PubMed2003

The luteinizing hormone receptor: influence of buffer composition on ligand binding and signaling of wild type and mutant receptors.

There is evidence that ligand binding to and ligand-mediated signaling by the luteinizing hormone receptor (LHR) are influenced by buffer conditions, including ionic type and strength, an issue that becomes important in comparing functional parameters obtained on receptor mutants under different conditions. In order to study this phenomenon, we performed binding (kinetic and saturation) and signaling studies of human chorionic gonadotropin (hCG) with wild type (wt) LHR and several mutants expressed in COS-7 cells using two common buffer systems. One buffer was of low ionic strength and contained a low concentration of Na+, while the other had a near-physiological concentration of Na+. Emphasis was placed on mutations of two amino acid residues in the hinge region of the ectodomain (E332 and D333). It was found that the buffer of higher ionic strength, primarily from Na+, led to an increase of about 4-fold in the Kd of hCG binding to wt and mutant LHRs. The reduced binding affinities were attributable to a comparable reduction in the rate constants of association, with no significant differences in the calculated rate constants of dissociation in the two buffers. Analysis of the signaling properties of these mutants showed that, when corrected for the amount of hCG bound under the conditions of the signaling assay, the maximal ligand-mediated cAMP produced in cells maintained in the buffer of low ionic strength was comparable for wt LHR and the mutants, only the D333A mutant being somewhat elevated. In the buffer of higher ionic strength, however, the response by wt LHR was significantly greater than that of the mutants. These results show that E332 and D333 are important in hormone-mediated signaling, but only in the buffer of higher Na+ concentration. In addition to mutants of these two residues, the buffer of higher ionic strength also led to reduced binding to a number of mutants throughout the receptor. Since these mutants included additional replacements in the ectodomain and transmembrane helices 6 and 7, the general nature of the buffer effect on wt and mutant LHRs suggests that electrostatic effects are contributing to ligand binding and/or that the LHR ectodomain may exist in two conformations, one being more accessible to ligand at reduced ionic strength.

Amino Acid Sequence↗
PubMed1998

Pain reduction in lidocaine administration through buffering and warming.

This study compared the pain from intradermal infiltration of (1) plain lidocaine, (2) warmed lidocaine, (3) buffered lidocaine, and (4) warmed, buffered lidocaine. A randomized, double-blind, Latin Square design of 20 volunteers was used. Each volunteer was injected with a series of four test solutions on four separate occasions, for 16 total injections each. Each volunteer served as his or her own control. The mean pain scores for the four solutions were: 44.2 for plain lidocaine, 42.2 for warmed lidocaine, 36.7 for buffered lidocaine, and 29.2 for warmed, buffered lidocaine. Buffered lidocaine was statistically less painful than both plain lidocaine and warmed lidocaine. Warmed, buffered lidocaine was significantly less painful than all other solutions, including buffered lidocaine (P < .005). However, warmed lidocaine did not yield pain scores significantly different from plain lidocaine. In this experimental model, warmed lidocaine was not superior to plain lidocaine, but warmed, buffered lidocaine caused significantly less pain than plain lidocaine, buffered lidocaine, or warmed lidocaine. Thus, there may be benefit from heating the buffered lidocaine now in common clinical use.

Adult↗
PubMed1997

Control of poorly soluble drug dissolution in conditions simulating the gastrointestinal tract flow. 2. Cocompression of drugs with buffers.

The objective of this study was to determine the primary formulation properties that affect the dissolution rate of poorly soluble nondisintegrating drugs. This work focused on compression of orally administered acidic drugs with ionizable buffers. Naproxen was used as the poorly soluble model drug, and calcium salts of carbonic, citric, and phosphoric acids were used as formulation buffers. Gastrointestinal tract (GI) dissolution was simulated in a laminar flow apparatus by exposing a drug/buffer tablet to aqueous solution of a given pH at a constant flow rate. Although formulation with a buffer resulted in reduced available drug surface area, the absolute drug dissolution rate and flux increased with increased buffer content to a maximum from tablets having equal weights of drug and buffer. This buffer-induced enhancement was seen not only in GI tract simulation (pH 7), but also at pH 2 (stomach conditions), where acidic drugs remain in their poorly soluble form upon dissolution. The flux increase was much greater than that achieved by using the same amount of an inert excipient in the solid formulation. Dissolution rates were also increased by decreased drug and buffer particle sizes and increased fluid flow rate. Drug dissolution rates were inversely proportional to intrinsic buffer solubilities: The model drug actually dissolved fastest when the buffer solubility was lower than that of the drug. Dissolution rates were apparently insensitive to the relative proximity of the drug and buffer ionization constants.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

Titration curves: a useful instrument for assessing the buffer systems of acidic mining waters.

BACKGROUND, AIMS AND SCOPE: The acidification of mine waters is generally caused by metal sulfide oxidation, related to mining activities. These waters are characterized by low pH and high acidity due to strong buffering systems. The standard acidity parameter, the Base Neutralization Capacity (BNC), is determined by endpoint titration, and reflects a cumulative parameter of both hydrogen ions and all buffering systems, but does not give information on the individual buffer systems. We demonstrate that a detailed interpretation of titration curves can provide information about the strength of the buffering systems. The buffering systems are of importance for environmental studies and treatment of acidic mining waters. METHODS: Titrations were carried out by means of an automatic titrator using acidic mining waters from Germany and Canada. The curves were interpreted, compared with each other, to endpoint titration results and to elemental concentrations contained therein. RESULTS AND DISCUSSION: The titration curves were highly reproducible, and contained information about the strength of the buffer systems present. Interpretations are given, and the classification and comparison of acidic mining waters, by the nature and strength of their buffering systems derived from titration curves are discussed. The BNC-values calculated from the curves were more precise than the ones determined by the standard endpoint titration method. Due to the complex buffer mechanisms in acidic mining waters, the calculation of major metal concentrations from the shape of the titration curve resulted in estimates, which should not be confused with precise elemental analysis results. CONCLUSION: Titration curves provide an inexpensive, valuable and versatile tool, by which to obtain sophisticated information of the acidity in acidic water. The information about the strength of the present buffer systems can help to understand and document the complex nature of acidic mining water buffer systems. Finally, the interpretation of titration curves could help to improve treatment measurements and the ecological understanding of these acidic waters.

Acids↗
PubMed1985

Role of histidine-related compounds to intracellular buffering in fish skeletal muscle.

Histidine-related compounds (HRC) were analyzed in fish skeletal muscle as a means of identifying their precise role in intracellular buffering. Fish muscle was used because it contains two functionally and spatially distinct fiber types, red and white. Two fish species, rainbow trout (Salmo gairdneri) and the Pacific blue marlin (Makaira nigricans), were studied because these species demonstrate widely different activity patterns. Marlin red and white muscle buffer capacity was two times higher than trout with white muscle, buffering being two times greater than red in both species. Buffer capacity was highest in the 6.5-7.5 pH range for all tissues, which corresponded to their high anserine levels. The titrated HRC buffering was greater than the observed HRC buffering, which suggested that not all HRC were available to absorb protons. The HRC contribution to total cellular buffering varied from a high of 62% for marlin white to a low of 7% for trout red. The other principal buffers were found to be phosphate and protein with taurine contributing within red muscle in the 7.0-8.0 pH range. HRC were found to be dominant in skeletal muscle buffering by principally accounting for the buffering capacity differences found between the species and fiber types.

Animals↗