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PubMed1996

Measurement of intratumor pH by pH indicator used in 19F-magnetic resonance spectroscopy. Measurement of extracellular pH decrease caused by hyperthermia combined with hydralazine.

RATIONALE AND OBJECTIVES: Without affect of metabolic changes, the authors measured intratumor pH by using 19F-magnetic resonance spectroscopy (MRS) with a fluorine compound (ZK-150471) on the basis of a calibration curve by pH electrode. METHODS: Using the 4.7-tesla magnetic resonance apparatus, a fluorine compound that had acid-base equilibrial change and was impermeable within cell membranes was used. The fluorine compound was injected intravenously. The signal was obtained from mouse mammary cancer by creating an experimental tumor on the leg of mice. And the tumors, which were heated with and without hydralazine. The pH evaluated from chemical shift of the fluorine compound. The pH data was obtained from an electrode for reference. RESULTS: The pH of nontreated tumors (n = 25) were 6.94 + 0.091. The pH decreased to 6.772 + 0.169 at 20 minutes even after 20 minutes of heating, and decreased to < 6.71 at 40 minutes after every heating time. The pH decreased to 6.456 at 20 minutes after 15 minutes of heating combined with hydralazine, and to 6.416 at 40 minutes after same treatment. CONCLUSIONS: It is possible to measure the extracellular pH by 19F-MRS with the fluorine compound noninvasively in vivo, even after heating.

Animals↗

PubMed1991

Crystal structure analysis of oxidized Pseudomonas aeruginosa azurin at pH 5.5 and pH 9.0. A pH-induced conformational transition involves a peptide bond flip.

The X-ray crystal structure of recombinant wild-type azurin from Pseudomonas aeruginosa was determined by difference Fourier techniques using phases derived from the structure of the mutant His35Leu. Two data sets were collected from a single crystal of oxidized azurin soaked in mother liquor buffered at pH 5.5 and pH 9.0, respectively. Both data sets extend to 1.93 A resolution. The two pH forms were refined independently to crystallographic R-factors of 17.6% (pH 5.5) and 17.5% (pH 9.0). The conformational transition previously attributed to the protonation/deprotonation of residue His35 (pKa(red) = 7.3, pKa(ox) = 6.2), which lies in a crevice of the protein close to the copper binding site, involves a concomitant Pro36-Gly37 main-chain peptide bond flip. At the lower pH, the protonated imidazole N delta 1 of His35 forms a strong hydrogen bond with the carbonyl oxygen from Pro36, while at alkaline pH the deprotonated N delta 1 acts as an acceptor of a weak hydrogen bond from HN Gly37. The structure of the remainder of the azurin molecule, including the copper binding site, is not significantly affected by this transition.

Aurintricarboxylic Acid↗

PubMed2003

Insertion of carbon fragments into P(III)-N bonds in aminophosphines and aminobis(phosphines): synthesis, reactivity, and coordination chemistry of resulting phosphine oxide derivatives. Crystal and molecular structures of (Ph(2)P(O)CH(2))(2)NR (R = Me, (n)Pr, (n)Bu), Ph(2)P(O)CH(OH)(n)()Pr, and cis-[MoO(2)Cl(2)((Ph(2)P(O)CH(2))(2)NEt-kappaO,kappaO)].

Reactions of N-aryl and N-alicyclic derivatives of aminophosphines with paraformaldehyde lead to methylene insertion into P-N bond followed by oxidation of phosphorus from the P(III) to P(V) state. When N-alkyl derivatives are reacted with paraformaldehyde, dimerization takes place to afford bis(phosphine oxide)s of the type Ph(2)P(O)CH(2)N(R)CH(2)P(O)Ph(2) (R = Me, (n)Pr, (n)Bu). Aminobis(phosphines) also undergo methylene insertion when treated with paraformaldehyde to give bis(phosphine oxides) Ph(2)P(O)CH(2)N(R)CH(2)P(O)Ph(2) (R = Me, Et, (n)()Pr, (i)()Pr, (n)Bu) in good yield. The reaction of aminophosphines with aromatic aldehydes ArCHO leads to insertion of "ArCH" into the P-N bond to give Ph(2)P(O)CH(R)N(H)Ph (R = C(6)H(5), furfuryl, o-C(6)H(4)OH), but with aliphatic aldehydes such as butanal, P-N bond cleavage takes place to afford alpha-hydroxy phosphine oxide. The reaction of aminobis(phosphines) with both aromatic and aliphatic aldehydes leads to the formation of alpha-hydroxy phosphine oxides through P-N bond cleavage whereas the reaction with furfural leads to the P-N bond insertion. The structure of the alpha-hydroxy derivative Ph(2)P(O)CR(H)(OH)(n)()Pr shows intermolecular hydrogen bonding between OH and P=O oxygen. The phosphine oxide derivatives act as bidentate ligands and form chelate complexes with Co(II), Mo(VI), Th(IV), and U(VI) derivatives. The crystal structure of the molybdenum complex, cis-[MoO(2)Cl(2)((OPPh(2)CH(2))(2)NEt-kappaO,kappaO)], shows the distorted octahedral geometry around Mo with two oxo groups cis to each other.

Journal Article↗

PubMed1989

Neuronal pH regulation: constant normal intracellular pH is maintained in brain during low extracellular pH induced by acetazolamide--31P NMR study.

The intracellular pH in the brain was studied in six healthy volunteers before and immediately after the administration of 2 g of acetazolamide. Phosphorus-31 nuclear magnetic resonance spectroscopy by a 1.5 tesla whole-body scanner was used. The chemical shift between the inorganic phosphate and the phosphocreatine resonance frequencies was used for indirect assessment of the intracellular pH. The mean baseline intracellular pH was 7.05 +/- 0.04 (SD). The mean pH changes obtained at 15-min intervals within the first hour of acetazolamide administration were -0.03 +/- 0.04 (SD), -0.02 +/- 0.03 (SD), and 0.00 +/- 0.04 (SD), i.e., no statistically significant pH decrease was observed during the period where extracellular pH is known to drop markedly. Although several factors contribute to the lack of change of the intraneuronal pH, we will discuss that this observation in addition might suggest a direct intracerebral effect of acetazolamide.

Acetazolamide↗

PubMed1982

Effects of commercial (pH approximately 3.5) and freshly prepared (pH approximately 6.5) lidocaine-adrenaline solutions on tissue pH.

Differences in the effects of commercially available, sodium bisulfite-containing (pH 3.5-4), and freshly prepared (pH 6.5) lidocaine-adrenaline solutions on tissue pH and tissue oxygenation were studied experimentally. In rabbits, a 5 x 5 cm area under the panniculum was infiltrated with 0.9% NaCl, plain lidocaine, plain adrenaline or one of the two lidocaine-adrenaline solutions. Tissue pH was measured continuously as well as intermittently in the infiltrated area with monocrystalline antimony needle electrodes. Infiltration of the tissue with the 4 ml volume of a test solution did not seem to induce any significant tissue injury. Tissue pH was decreased for 30 min following plain lidocaine and for 90 min or more following lidocaine-adrenaline infiltration. With the exception of the first few minutes, no significant differences in the effects on tissue pH between commercial and freshly prepared lidocaine-adrenaline solutions could be seen. Tissue hypoxia occurred only following infiltration with plain adrenaline. It may thus be concluded that in spite of the low pH and the O2-reducing properties of commercial lidocaine-adrenaline solutions, a rapid buffering occurs in the tissues. The use of commercial lidocaine-adrenaline solution for local infiltration thus seems as safe as that of freshly prepared lidocaine-adrenaline solutions.

Animals↗

PubMed1989

[pH determination in human crevicular fluids. Examination of the pH meter and evaluation of the correlation between pH level and clinical findings or the microflora in each periodontal pocket].

The purpose of this study was to investigate the accuracy and reproduction of a microelectrode with a glass capillary, and to discuss the correlation between the pH level and the microflora in periodontal pockets or the clinical findings in the various stages of periodontal disease. The upper or lower anterior teeth of 34 patients with mild to severe periodontal disease were examined. Before the measurement, supragingival plaque was removed from each tooth. A special glass capillary was incorporated in the microelectrode to cover its tip, so that it would not touch the pocket walls or tooth surfaces during pH measurement. After the pH in the crevicular fluid was determined, subgingival plaque was collected with paper points from each periodontal pocket. This bacterial plaque was sonicated with saline solution, and examined under a phase contrast microscope with a calibrated eyepiece graticule to count and morphotype groupings of microorganisms as 1) coccoid forms, 2) rods, 3) filaments, 4) motile rods, 5) spirochetes or other cell types. Crevicular fluid flow measurements and clinical findings (pocket depth, and gingival inflammation) were also investigated. The following conclusions were drawn: The electrode with capillary was useful to determine the pH of the crevicular fluid clinically. A reduction in pH level was seen in deep pockets or severe gingival inflammation. A close correlation was seen between salivary and crevicular pH. The pH level was significantly positively related with the proportion of coccoid forms, but was negatively correlated with the proportion of motile organisms that are reported to be related with periodontal disease.

Dental Instruments↗

PubMed1985

Intracellular pH shift leads to microtubule assembly and microtubule-mediated motility during sea urchin fertilization: correlations between elevated intracellular pH and microtubule activity and depressed intracellular pH and microtubule disassembly.

The regulation of the microtubule-mediated motions within eggs during fertilization was investigated in relation to the shift in intracellular pH (pHi) that occurs during the ionic sequence of egg activation in the sea urchins Lytechinus variegatus and Arbacia punctulata. Microtubule assembly during formation of the sperm aster and mitotic apparatus was detected by anti-tubulin immunofluorescence microscopy, and the microtubule-mediated migrations of the sperm and egg nuclei were studied with time-lapse video differential interference contrast microscopy. Manipulations of intracellular pH were verified by fluorimetric analyses of cytoplasmic fluorescein incorporated as fluorescein diacetate. The ionic sequence of egg activation was manipulated i) to block the pHi shift at fertilization or reduce the pHi of fertilized eggs to unfertilized values, ii) to elevate artificially the pHi of unfertilized eggs to fertilized values, and iii) to elevate artificially or permit the normal pHi shift in fertilized eggs in which the pHi shift at fertilization was previously prevented. Fertilized eggs in which the pHi shift was suppressed did not assemble microtubules or undergo the normal microtubule-mediated motions. In fertilized eggs in which the pHi was reduced to unfertilized levels after the assembly of the sperm aster, no motions were detected. If the intracellular pH was later permitted to rise, normal motile events leading to division and development occurred, delayed by the time during which the pH elevation was blocked. Microtubule-mediated events occurred in eggs in which the intracellular pH was elevated, even in unfertilized eggs in which the pH was artificially increased. These results indicate that the formation and normal functioning of the egg microtubules is initiated, either directly or indirectly, by the shift in intracellular pH that occurs during fertilization.

Animals↗

PubMed1999

Synthesis and Characterization of Zinc and Cadmium Compounds with Arenephosphinothiol Ligands. Crystal and Molecular Structures of [Cd(2){2-(Ph(2)PO)C(6)H(4)S}(4)], [Zn{2-(Ph(2)P)-6-(Me(3)Si)C(6)H(3)S}(2)], [Cd{2-(Ph(2)PO)-6-(Me(3)Si)C(6)H(3)S}(2)(CH(3)OH)], and [Zn{PhPO(C(6)H(4)S-2)(2)}(bipy)].

The electrochemical oxidation of a metallic anode (zinc or cadmium) in an acetonitrile solution of a series of arenephosphinothiol ligands, 2-(Ph(2)P)C(6)H(4)SH, 2-(Ph(2)P)-6-(Me(3)Si)C(6)H(3)SH, 2-(Ph(2)PO)-6-(Me(3)Si)C(6)H(3)SH, and PhP(C(6)H(4)SH-2)(2) [abbreviated RP-(SH)(x)(), x = 1 or 2], affords [M(RP-S)(2)] and [M(RP-S(2))], M = Zn, Cd. Adducts of several of these compounds with 1,10-phenanthroline and 2,2'-bipyridine have also been obtained by addition of these coligands to the electrolysis phase. The compounds obtained have been characterized by microanalysis, IR, UV-visible, FAB spectrometry and (1)H, (31)P NMR spectroscopic studies. The compounds, [Cd(2){2-(Ph(2)PO)C(6)H(4)S}(4)]CH(3)CN (1), [Zn{2-(Ph(2)P)-6-(Me(3)Si)C(6)H(3)S}(2)] (2), [Cd{2-(Ph(2)PO)-6-(Me(3)Si)C(6)H(3)S}(2)(CH(3)OH)] (3), and [Zn{PhPO(C(6)H(4)S-2)(2)}(bipy)] (4), have been also characterized by single-crystal X-ray diffraction. Compound 1 is binuclear with a {Cd(2)S(2)} core and distorted trigonal bipyramidal {CdO(2)S(3)} geometry about the Cd sites. Compounds 2, 3, and 4 are mononuclear with distorted tetrahedral {ZnP(2)S(2)}, distorted square pyramidal {CdO(3)S(2)}, and distorted trigonal bipyramidal {ZnON(2)S(2)} geometries, respectively. Crystal data: 1, C(42)H(37)N(3)O(2)P(2)S(2)Cd, triclinic, P&onemacr;, a = 13.5780(2) Å, b = 13.8505(2) Å, c = 13.9526(2) Å, alpha = 106.622(1) degrees, beta = 109.693(1) degrees, gamma = 107.137(1) degrees, V = 2133.30(5) Å(3), Z = 2, 9560 reflections, R = 0.0483; 2, C(46)H(50)N(2)P(2)S(2)Si(2)Zn, monoclinic, C2/c, a = 21.332(4) Å, b = 9.391(2) Å, c = 25.938(5) Å, beta = 113.84(3) degrees, V = 4753(2) Å(3), Z = 4, 2564 reflections, R = 0.0377; 3, C(43)H(48)CdO(3)P(2)S(2)Si(2), triclinic, P&onemacr;, a = 12.1237(4) Å, b = 14.0568(4) Å, c = 15.0938(2) Å, alpha = 70.836(2) degrees, beta = 83.410(2) degrees, gamma = 65.397(2) degrees, V = 2208.7(1) Å(3), Z = 2, 4936 reflections, R = 0.0738; 4, C(29)H(22)Cl(3)N(2)OP(2)S(2)Zn, triclinic, P&onemacr;, a = 8.9556(3) Å, b = 12.7911(4) Å, c = 14.0598(5) Å, alpha = 82.671(1) degrees, beta = 73.140(1) degrees, gamma = 74.113(1) degrees, V = 1480.44(9)(1) Å(3), Z = 2, 3820 reflections, R = 0.0511.

Journal Article↗

PubMedDate not supplied

Recent developments in two-dimensional gel electrophoresis with immobilized pH gradients: wide pH gradients up to pH 12, longer separation distances and simplified procedures.

Wide-range immobilized pH 3-12 and 6-12 gradients were generated. Depending on the extraction method of sample preparation, proteins with p/s up to pH 11.7 were resolved. Highly reproducible protein patterns, focused to the steady-state with round-shaped spots up to the basic end were obtained. Moreover, because a strong water transport from cathode to anode (reverse electroendosmotic flow) inherent to narrow immobilized pH gradients (IPGs) exceeding pH 11, such as IPG 10-12, was negligible, the wide-range IPGs 3-12 and 6-12 could be run under standard conditions as originally described by Görg et al (Electrophoresis 1988, 9, 531-546). The wide-range immobilized pH gradient 3-12 proved to be perfectly suited for an overview separation of total cell extracts. Resolution could be increased by extending the separation distance from 18 to 24 cm. Furthermore, two-dimensional gel electrophoresis with IPGs (IPG-Dalt) was simplified by the use of an integrated system (IPGphor) where sample application by in-gel rehydration and isoelectric focusing (IEF) are performed automatically in a one-step procedure, overnight, without human assistance.

Animals↗

PubMed1980

Intracellular pH and surface pH in skeletal and cardiac muscle measured with a double-barrelled pH microelectrode.

The construction of a double-barrelled pH sensitive microelectrode for intracellular use is described. Repetitive measurements of intracellular pH were obtained in rat soleus muscle and sheep Purkinje fibres. They yielded pH values ranging between 7.1 and 7.2 in a CO2/HCO3- buffered medium at 37 degrees C. A lower pH value than that of the bulk solution was found at the surface of the cells using either double-barrelled or single-barrelled pH sensitive microelectrodes.

Animals↗

PubMed1988

Changes in intracellular pH and pH regulating mechanisms in somitic cells of the early chick embryo: a study using fluorescent pH-sensitive dye.

1. Measurements of intracellular pH (pHi) have been made using the fluorescent dye dicyano-hydroquinone (DCH) in somites isolated from 2-day-old chick embryos. Measurements of pHi, from freshly dissected somites, gave values of 7.18 +/- 0.02 (mean +/- S.D., n = 12) while in somites kept in media containing 10% fetal calf serum for 2-5 h pHi was 7.36 +/- 0.02 (n = 11). 2. In freshly dissected control tissue recovery from an acid load (NH4Cl pre-pulse), in the nominal absence of HCO3-, was 0.007 +/- 0.003 pH units/min (n = 11). In the presence of 5 mM-HCO3- the rate of recovery was increased to 0.132 +/- 0.003 pH units/min (n = 11). This HCO3(-)-dependent recovery was inhibited by pre-treatment with DIDS (5 X 10(-4) M) and stopped when Na+ was replaced in the bathing medium with K+ or N-methylglucamine. Amiloride (10(-3) M) had no effect. 3. Replacement of Cl- with gluconate had little effect on pHi in control somites suggesting that absence of Cl(-)-HCO3- exchange. 4. These observations are consistent with the presence of a coupled Na+-HCO3- entry and the absence of Na+-H+ exchange. 5. In serum-treated cells recovery from an acid load was 0.101 +/- 0.01 pH units/min (n = 11) in the nominal absence of HCO3-. Increasing the HCO3- concentration (5-10 mM) or pre-treatment with DIDS had no effect on the rate of acid extrusion. Recovery is Na+ dependent and inhibitable with amiloride, indicating the presence of Na+-H+ exchange. 6. These results suggest that during somitic development the mechanisms regulating pHi and recovery from acid loading are modified from a Na+-HCO3- influx to a Na+-H+ exchanger. This transition allows the cells to increase pHi by up to 0.2 pH units and may have a role in somitic cell development.

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

PubMed1990

Differences in the skin surface pH and bacterial microflora due to the long-term application of synthetic detergent preparations of pH 5.5 and pH 7.0. Results of a crossover trial in healthy volunteers.

Skin cleansing preparations consisting of identical synthetic detergents but differing in pH-value (pH 5.5 and 7.0) were applied twice daily on the forehead and forearm of healthy volunteers in a randomized crossover trial. The skin surface pH was found to be significantly higher when the neutral preparation had been used, as was the propionibacterial count (p less than 0.05). The number of propionibacteria was significantly linked to the skin pH. Hence even minor differences in the pH of skin cleansing preparations seem to be of importance for the integrity of the skin surface. This should be taken into account when planning the formulation of optimal skin care products.

Adult↗

PubMed1978

[The determination of salivary pH by contact pH meter in individuals receiving psychotropic therapy. Study of pH on the tongue and at the orifice of Wharton's and Stenon's ducts (author's transl)].

The authors studied salivary pH at different sites in 172 patients receiving psychotropic therapy in hospital. For statistical purposes, the study was limited to individuals receiving a "moderate" dose of: --a benzodiazepine derivative --a neuroleptic and benzodiazepine --antidepressant, neuroleptic and benzodiazepine. Regardless of the type of psychotropic therapy and of the site of measurement, acidification of salivary pH which was statistically significant in comparison with values found in healthy subjects was noted. This acidification was particularly marked with regard to "lingual" pH. In addition, regardless of the site of measurement, a higher degree of acidification of salivary pH was seen in individuals receiving a combination of psychotropic agents. This acidification was particularly striking with regard to salivary pH in patients given a combination of antidepressant, neuroleptic and a benzodiazepine derivative. The cause of this acidification is not definitely known. A number of hypotheses may be put forward: decrease in salivary volume (Laudenbach, 6, and Vermeil, 7), excretion of acid metabolites by the salivary glands, effect of psychotropic agents upon the action itself of the salivary glands.

Antidepressive Agents↗

PubMed1996

Iodination of alpha-Phosphino Enolate Complexes of Palladium(II) and Platinum(II). Synthesis and Crystal Structures of [(dmba)Pd{Ph(2)PC(I)C(O)Ph}] and of the Dipalladium(II) Complex [(dmba)Pd{Ph(2)PCC(O)Ph}Pd(I)(tmeda)] Obtained by Palladium(0) Insertion into the Carbon-Iodine Bond.

Electrophilic attack of 1 equiv of I(2) on a PC(sp)2 carbon of the Pt(II) complex (1) afforded (2) in 90% yield. Complex 2 was subsequently deprotonated by NaOEt in ethanol to give the bis(enolato) complex (3). This alpha-phosphino, alpha-iodo enolato complex was obtained directly and quantitatively by the reaction of 1 with 1 equiv of N-iodosuccinimide (NIS). When 2 equiv of NIS was used, the symmetrical complex (4) was formed selectively. In contrast to I(2), NIS was also able to functionalize the phosphino enolate ligand of complexes to give the corresponding iodo derivatives (C N = dmba (5) or 8-mq (6)). These represent the first examples in which a phosphino enolate C-H bond has been directly functionalized, i.e. replaced by a C-X bond. Attempts to use this procedure with or with were unsuccessful. Reaction of 5 with Pd(dba)(2) in the presence of tetramethylenediamine (tmeda) or 2,2'-bipyridine (bipy) afforded (7) and (8), respectively. The solid state structures of complexes 5 and 7.CH(2)Cl(2) have been determined by single-crystal X-ray diffraction: 5 crystallizes in the monoclinic space group P2(1)/n with Z = 4 in a unit cell of dimensions a = 12.867(3) Å, b = 10.625(3) Å, c = 19.509(6) Å, and beta = 102.23(2) degrees; 7.CH(2)Cl(2) crystallizes in the monoclinic space group C2/c with Z = 8 in a unit cell of dimensions a = 35.906(3) Å, b = 13.565(3) Å, c = 15.775(2) Å, and beta = 95.099(10) degrees. Complex 7 contains two palladium(II) centers, in a square-planar environment, connected by the P-C unit of a phosphino enolate ligand which adopts an unprecedented &mgr;-eta(2)(P,C):eta(2)(P,O) bonding mode. The two coordination planes are almost orthogonal and make a dihedral angle of 88.0(2) degrees, which minimizes the steric hindrance between the ligands.

Journal Article↗

PubMed1999

Synthesis and Characterization of Indium Compounds with Phosphinothiol Ligands. The Crystal and Molecular Structures of [In{2-(Ph(2)P)C(6)H(4)S}(3)], [In{2-(Ph(2)P)-6-(Me(3)Si)C(6)H(3)S}(2){2-(Ph(2)PO)-6-(Me(3)Si)C(6)H(3)S}], and [NMe(4)][In{PhP(C(6)H(4)S-2)(2)}(2)].CH(3)CN.

The electrochemical oxidation of anodic indium metal in an acetonitrile solution of phosphinothiol ligands affords [In{2-(Ph(2)P)C(6)H(4)S}(3)] (1), [In{2-(Ph(2)P)-6-(Me(3)Si)C(6)H(3)S)}(2){2-(Ph(2)PO)-6-(Me(3)Si)C(6)H(3)S}] (2), [In{2-(Ph(2)PO)-6-(Me(3)Si)C(6)H(3)S}(3)] (3), and [NMe(4)][In{PhP(C(6)H(4)S-2)(2)}(2)].CH(3)CN (4) complexes exhibiting distorted six-coordinate geometries based on {InS(3)P(3)}, {InS(3)P(2)O}, and {InS(4)P(2)} cores, respectively. In all cases, the In-P bond distances are anomalously long, presumably as a consequence of steric crowding. The anion of 4 provides an unusual example of an In(III)-thiolate coordination complex ion. Crystal data: 1, C(54)H(42)InP(3)S(3), monoclinic, P2(1)/c, a = 16.6579(1) Å, b = 12.6628(2) Å, c = 22.5520(3) Å, beta = 96.42(1) degrees, V = 4727.15(1) Å(3), Z = 4, 6176 reflections, R = 0.0579; 2, C(63)H(66)InOP(3)S(3)Si(3), monoclinic, P2(1)/c, a = 11.53090(10) Å, b = 26.2505(3) Å, c = 20.4206(2) Å, beta = 94.0870(10) degrees, V = 6165.43(11) Å(3), Z = 4, 10 699 reflections, R = 0.0621; 4, C(42)H(41)InN(2)P(2)S(4), monoclinic, P2(1), a = 13.0052(2) Å, b = 11.2240(2) Å, c = 14.3070(3) Å, beta = 93.190(1) degrees, V = 2085.16(7) Å(3), Z = 2, 6651 reflections, R = 0.0352.

Journal Article↗

PubMed2002

Web-based two-dimensional database of Saccharomyces cerevisiae proteins using immobilized pH gradients from pH 6 to pH 12 and matrix-assisted laser desorption/ionization-time of flight mass spectrometry.

An image based two-dimensional (2-D) reference map of very alkaline yeast cell proteins was established by using immobilized pH gradients (IPG) up to pH 12 (IPG 6-12, IPG 9-12 and IPG 10-12) for 2-D electrophoresis and by using matrix-assisted laser desorption/ionization-time of flight mass spectrometry peptide mass fingerprinting for spot identification. Up to now 106 proteins with theoretical isoelectric points up to pH 11.15 and molecular mass between 7.5 and 115 kDa were localized and identified. Additionally, due to the improved resolution of steady-state isoelectric focussing with IPGs, even low copy number proteins with codon bias below 0.02 were detected and identified.

Databases as Topic↗

PubMed2005

Simulating phenol high-performance liquid chromatography retention times as the pH changes. Mobile phase pH versus buffer pH.

The HPLC retention times of several substituted phenols have been measured and simulated using Advanced Chemistry Development's LC simulator, using 50% acetonitrile (ACN) as the mobile phase. For alkyl- and nitro-substituted phenols, the quality of the simulation improves when pH of the mobile phase is estimated and used in the simulation. Simply using the pH of the buffer gives simulation results that are not as close to the actual retention times. However, the opposite is the case for halogenated phenols. The pK(a) values in 50% ACN for some of these phenols have also been determined, which tend to be one unit higher than the aqueous pK(a) values reported in the literature.

Acetonitriles↗

PubMed2001

The response of GS-NS0 myeloma cells to pH shifts and pH perturbations.

The perceived sensitivity of animal cells to hydrodynamic shear has limited agitation and aeration at large-scale. This makes it difficult to ensure adequate mixing of the vessel contents and may lead to inhomogeneities in operational parameters such as temperature, dissolved oxygen concentration, and especially pH. The effect of pH shifts and pH perturbations on the cellular responses, in batch culture, of a GS-NS0 mouse myeloma cell line, expressing a recombinant antibody, was investigated. In addition, the effect of extreme pH on the structure of the purified antibody product was studied using isoelectric focusing. The fermentation pH value was shifted abruptly from pH 7.3 to pH values ranging from 6.5 to 9.0. Culture pH was maintained at this new value for the remainder of the fermentation. All pH shifts of above 0.2 units caused a transient increase in apoptosis. However, cultures shifted to pH values between 7.0 and 8.0 continued to grow and the apoptotic fraction returned to initial levels. Cultures shifted to pH values above pH 8.0 and below pH 7.0 did not recover resulting in culture death. For example, a shift to pH 8.5 caused accumulation of cells in the G(2)/M phase of the cell cycle followed by apoptotic death. After the pH shift, maximum specific growth rate was observed over the range pH 7.3 to 7.5 and maximum viable cell number was seen at pH 7.3. Maximum volumetric antibody production, resulting from increased culture longevity, was seen at pH 7.0. It was also observed that glucose consumption increased with increasing pH. In a separate set of experiments cells were subjected to a single pH perturbation ranging in duration from 0 to 600 minutes. Exposure of cells to a pH value greater than 8.5 for more than 10 minutes caused a decrease in the proportion of viable cells and induced a lag in cell growth. At very low pH (6.5) similar effects were seen, but only for extended perturbations (600 min). However, after recovery from the pH perturbation, growth, product secretion and metabolism all returned to original levels. Incubation of the antibody, at the range of pH values investigated, indicated no alterations in the structure of the antibody as determined by the isoelectric focusing pattern.

Animals↗