Showing papers on "Titration published in 1983"
TL;DR: To evaluate the accuracy of pH determination by 31P-NMR, factors which influence the pK value of phosphate were appraised on the basis of the titration of 1 mM phosphate buffer solution.
Abstract: To evaluate the accuracy of pH determination by 31P-NMR, factors which influence the pK value of phosphate were appraised on the basis of the titration of 1 mM phosphate buffer solution. When the method is used for the determination of cytoplasmic pH, ionic strength is the major factor causing shifts of apparent pK (pK') value, and the magnitude of the shift can be predicted from the ionic strength calculated by means of the Debye-Huckel equation. Ions (Na+, K+, Mg2+, and Ca2+) and salivary protein affected the pK' value by 0.1 to 0.3 units in solution with a given ionic strength depending on the species of ion. The form of the titration curve varied with temperature. Based on these results, the value of 6.75 was obtained with the uncertainty of 0.12 for the intracellular pK' of frog muscle at 24 degrees C.
125 citations
TL;DR: The pK values of thermospermine, a novel asymmetric tetraamine, have been determined for the first time by the conventional titration method with subsequent data analyses and it was found to be the most basic polyamine among naturally occurring tetraamines.
Abstract: The pK values of thermospermine, a novel asymmetric tetraamine (4,8-diazadodecane-1,12-diamine), have been determined for the first time by the conventional titration method with subsequent data analyses. It was found to be the most basic polyamine among naturally occurring tetraamines. The 15N NMR titration method was applied to determine its protonation site. Natural-abundance 15N magnetic resonance spectra of the polyamine have been recorded as a function of pH from its free to the protonated form. Its apparent pK values, as well as the intrinsic chemical shifts for each stage of protonation, have been calculated from the NMR titration curve by using a nonlinear least-squares method. The four protonation sites of thermospermine have been successfully determined to be N12, N1, N-8, and N-4 in that order from the free to the completely protonated form. In a similar manner the protonation sites of spermidine and two symmetric tetraamines, thermine and spermine, have been established. 13C NMR experiments for the four polyamines were almost consistent with those of 15N NMR. Owing to the much higher concentration of the polyamines furnished for NMR titration experiments, the pK values obtained by NMR were larger than those derived by the conventional titration methods.
82 citations
TL;DR: It is concluded that polyelectrolyte titration offers an easy access to the determination of the surface charge of proteins and other biopolymers and supports the notion of the importance of electrostatic cooperative interactions in biological systems.
75 citations
TL;DR: The effects of the residual streaming potential and residual junction potential on the accuracy of pH and acidity measurements are discussed and quantified and a Gran's titration is used to assess total and strong acidity.
Abstract: The effects of the residual streaming potential and residual junction potential on the accuracy of pH and acidity measurements are discussed and quantified. Detailed analytical procedures minimizing these effects are described; a Gran's titration is used to assess total and strong acidity. The procedure for pH determination is shown to have a precision and accuracy of +/-0.01 pH unit. The acidity procedure shows acceptable accuracy and mean precision values (expressed as relative standard deviations) of 1.4% and 3.4% are obtained for strong and total acidity on the intervals 24-97 and 34-110 ..mu..equiv of H/sup +//L.
67 citations
TL;DR: In this article, a method for the determination of carbonates in soils and minerals is described, which consists of the digestion of a sample, containing between 0.5 and 15 mg C as carbonate, in 5N HCl under a stream of nitrogen gas, followed by the extraction of the evolved carbon dioxide in a sodium hydroxide trap.
Abstract: A method for the determination of carbonates in soils and minerals is described. It consists of the digestion of a sample, containing between 0.5 and 15 mg C as carbonate, in 5N HCl under a stream of nitrogen gas, followed by the determination of the evolved carbon dioxide in a sodium hydroxide trap. The carbon dioxide is titrated directly as carbonic acid in a two‐endpoint titration between pH 8.3 and 3.7.
54 citations
TL;DR: The results indicate that retention, in terms of salt concentration required for elution, is generally dependent upon the charge density of a protein.
53 citations
TL;DR: The binding of Cu2+ to soil-derived fulvic acid (SFA) measured by fluorescence quenching titration is much stronger than Co2+ and Mn2+ which are similar as mentioned in this paper.
Abstract: The binding of Cu2+ to soil-derived fulvic acid (SFA) measured by fluorescence quenching titration is much stronger than Co2+ and Mn2+ which are similar. The conditional stability constants from curve fitting at pH 6 are 1.1 × 105 for Cu2+, 5.1 × 103 for Co2+, and 4.2 × 103 for Mn2+. The slight advantage in strength for Co2+ over Mn2+ is also demonstrated by the binding curves at pH 6 and 7. These two metal ions not only tend to bind more weakly but also bind to fewer sites, giving complexing capacity values of about 1.5 × 10−6 M compared to 2.0 × 10−5 for Cu2+ at pH 6. This lower binding capacity may be due to outer sphere complexation that does not allow access to some sites complexed by inner sphere binding Cu2+. Scattering experiments demonstrate that Cu2+ is more effective at precipitating and aggregating SFA than Co2+ and Mn2+. Cu2+ probably neutralizes the negative charges on SFA molecules allowing larger hydrophobic aggregates to form and precipitate.
44 citations
TL;DR: In this article, the anion capacity of βFeOOH was shown to be a single valued function of the activity of acid (HCl) in the equilibrium solution, conveniently expressed in terms of pA = pH + pCl.
44 citations
TL;DR: In this paper, Dithallium(III) transferrin and the monothallium derivative with bicarbonate as synergistic ion have been prepared and characterized, and the signals for the two sites are well separated and have been assigned through titration with iron(III), at different pH values.
Abstract: Dithallium(III) transferrin and the monothallium derivative with bicarbonate as synergistic ion have been prepared and characterized. /sup 205/Tl NMR spectrosocpy is a reasonably good probe to monitor the occupancy of the two available binding sites. The signals for the two sites are well separated and have been assigned through titration with iron(III) at different pH values. Thallium shows larger affinity for the C-terminal site than for the N-terminal site all over the ph range investigated.
40 citations
TL;DR: It is concluded that, while some differences of redox reactivity do occur on protonation, these differences are not major and in general, the two proteins cyt c-551 and azurin react with each other with rates only weakly dependent upon pH.
Abstract: A fluorescence quenching experiment confirms that in the redox reaction between cytochrome c-551 and azurin, protein complexing is negligible. Azurin-pH indicator T-jump experiments show that Pseudomonas aeruginosa (Ps.) azurin exhibits a slow time constant, tau, in its return to pH equilibrium but Alcaligenes faecalis (Alc.) azurin does not. The decrease of l/tau with increasing pH shows that the rate-determining process is a slow transformation of the imidazolium form of histidine-35 from a conformation where it cannot ionize to one in which it can. The fast relaxation time constant of the redox reaction varies little with pH, but the slow time constant increased by a factor of approximately 2.5 increasing pH between pH 5 and pH 8. The corresponding amplitudes, especially the slow one, vary with pH. On the basis of all the present evidence it is concluded that, while some differences of redox reactivity do occur on protonation, these differences are not major. In general, the two proteins cyt c-551 and azurin react with each other with rates only weakly dependent upon pH. A classical pH titration was carried out on the reduced and oxidized form of Ps. and Alc. azurin with the result that two protons were released between pH 6 and pH 8, in the former from His-35 and -83 and in the latter from His-83 and Ala-1.
40 citations
TL;DR: The titrimetric determination of ascorbic acid in the presence of a variety of potentially physically and chemically interfering species in commercial liquid diets is presented and Iron(II, copper(II), cysteine, glutathione, sulfite, and tin(II) do not interfere.
TL;DR: The apparent equilibrium between alprazolam and the benzophenone compound at a given pH was estimated from the rate constants for the ring-opening and cyclization reactions, and the results agree with the apparent pKa measured by a conventional UV spectrophotometry and a titration technique.
TL;DR: In this paper, the possibility of using specific conductance and ionic strength of the solution as a means of determining appropriate endpoints in the titration sequence is discussed, which provides a means for the recovery of a substantial amount of the cost of generating an environmentally acceptable discharge.
TL;DR: In this paper, both oxidised and reduced glutathione bind iron(II) in the pH range 3-7 via the carboxylate groups, up to pH 7.
TL;DR: The pH-dependent polymerization of human leukocyte interferon A produced by recombinant DNA technology was investigated by potentiometric hydrogen ion titration and sedimentation velocity analytical ultracentrifugation, which results in a positive slope which is typical for self-aggregating systems.
Abstract: The pH-dependent polymerization of human leukocyte interferon A produced by recombinant DNA technology was investigated by potentiometric hydrogen ion titration and sedimentation velocity analytical ultracentrifugation. The titration curve is completely reversible from pH 6.2 to 2.5. Analysis of the side-chain carboxyl residues by using the Linderstrom-Lang equation yields a linear plot from pH 5.2 to 3.5. The resulting pKint and W values are 4.66 +/- 0.06 and 0.036 +/- 0.004, respectively. The titration curve from pH approximately 9.6 to 7 is also reversible. However, the reverse titration from pH 7 to 6 results in a time-dependent variation of pH. Sedimentation velocity analysis yields an increase in the corrected sedimentation coefficient, S20,w, from 2.0 to 4.0 S over a pH range of 2.5-9 at 0.38-0.25 mg/mL total protein concentration. The concentration dependence of the sedimentation coefficient at pH 7.0 over the range of 0.05-6.0 mg/mL results in a positive slope which is typical for self-aggregating systems. This aggregation phenomenon is discussed in terms of its ramifications for interferon therapy.
TL;DR: In this article, Amicon ultrafiltration has been employed to determine the extent of Cu, Ni, Co, Fe, Mn and Zu chelation in oxic waters from mineralized terrains.
TL;DR: Theoretical calculations were used to develop an electron titration curve for a hypothetical soil to show the characteristic redox poises (pe + pH values) maintained by various manganese and iron minerals as mentioned in this paper.
TL;DR: Fluorimetric titrations were carried out for various forms of 9-phenanthrylaminc and pKa* values were determined in this article, where an unusual behaviour observed in the fluorimetrie titration of the neutral form at moderate proton concentration is due to the quenching of the S1 state of PNH2 by H+.
Abstract: Fluorimetric titrations were carried out for various forms of 9-phenanthrylaminc and pKa* values were determined. An unusual behaviour observed in the fluorimetrie titration of the neutral form at moderate proton concentration is due to the quenching of the S1 state of PNH2 by H+.
TL;DR: Calcium ion titrations were performed on solutions of tobacco mosaic virus using a calcium-specific ion-exchange electrode to indicate that near neutrality, the virus particle possesses two calcium ion binding sites per subunit having apparent stability constants greater than 10(4) M-1.
TL;DR: In this article, it is shown how the standard error in measurements of the volume of reagent and the pH of the titration mixture effect the standard errors of the parameters that are calculated from the data by properly weighted regression analysis.
TL;DR: The mode of the binding of the anionic surfactant, sodium N-methyl N-oleoyltaurine, by gelatin in the pH region beyond the isoelectric point, where solutions are stable without precipitation, was investigated by acidimetric titration and by viscosity measurements as mentioned in this paper.
TL;DR: In this paper, the presence of carboxylate groups in polygalacturonic acid (PGA) complexes with Mn2+, Co2+ and Ni2+ was investigated by potentiometric titration of the polyelectrolyte in presence of varying amounts of metal ions.
01 Jan 1983
TL;DR: In this article, an expanded Tanford model was proposed for fulvic acid (FA) titration data, where both electrostatic and conformational terms were incorporated into an expanded version of the model.
Abstract: Gram quantities of reference fulvic acid (FA) have been extracted from natural waters for a systematic physico-chemical investigation of proton and metal binding properties. Electrophoretic and gel filtration chromatographic studies of FA indicate that during the course of an acid-base titration, marked conformational changes occurred with the molecular radius increasing from 0.65 nm (6.5A) at pH 1.15 to 1.32 nm (13.2 A) at pH 9.26. These conformational charges arise from intra-molecular electrostatic replusive forces associated with the build up of charge (Z) on the flexible FA polyanion. This in turn has a marked effect on the acid association constant (k). For this reason, the broad poly-disperse titration curves which are characteristic of FA could not be adequately explained by simple acid-base models which assume single values of k. However, by incorporating both electrostatic and conformational terms into an expanded Tanford model, we obtained a good fit to the titration data. The value of the intrinsic association constant ki (when Z = 0) derived from this model was rather acidic (log ki = 2.3−2.7) suggesting that the FA is strongly electron withdrawing. However, the combined effects of electrostatic and conformational changes is to spread the apparent constants over a wide range with the greatest number of sites having apparent log k = 4−5.
TL;DR: In this article, the SO + SO l S + SO2(2) was studied in the gas phase by using methyl thiirane as a titrant for sulfur atoms, and it was shown that k2 ≈ 3.5 × 10−15 cm3/s at 298 K.
Abstract: The reaction SO + SO l S + SO2(2) was studied in the gas phase by using methyl thiirane as a titrant for sulfur atoms. By monitoring the C3H6 produced in the reaction , we determined that k2 ≃ 3.5 × 10−15 cm3/s at 298 K.
TL;DR: In this paper, the optimal conditions for determination of 1:1 dissociation constants from NMR data are obtained from statistical analysis of simulated experiments in which changes in the spectral parameter(s) of a reagent (L) are monitored upon titration with another reagent(M).
TL;DR: Electrical conductivities in sediments of a strong cation-exchange resin were much higher than predicted by the junction artifact theory; electrode measurements of pH in sediment corresponded to titratable H(+)-content, and pH-changes induced by titration and salt addition were in accord with partitioning theory.
TL;DR: The proposed method was applied to the analysis of pharmaceutical preparations containing the drugs, and the results obtained compared favourably with those obtained by pharmacopoeial methods.
Abstract: An indirect titrimetric method is described for the determination of some N-substituted phenothiazine derivatives. The method involves the use of 1,3-dibromo-5,5-dimethylhydantoin or N-bromosuccinimide as the titrant. A known excess of either reagent is added and, after a specified time, the residual reagent is determined iodimetrically. The proposed method was applied to the analysis of pharmaceutical preparations containing the drugs, and the results obtained compared favourably with those obtained by pharmacopoeial methods.
TL;DR: In this article, conductometric evidence showed an interaction between alkali metals with protoporphyrin IXiron(III) in aqueous solutions and Mossbauer spectroscopic and pH titration data were also reported.
01 Jun 1983
TL;DR: P nuclear magnetic resonance (NMR), pH titration studies of the phosphoproteins tropomyosin and glycogen phosphorylase a show that the resonances for the phosphoserine regulatory sites shift with pH, leading to a proposal that mobility is a general feature of such regulatory sites.
Abstract: 31P nuclear magnetic resonance (NMR), pH titration studies of the phosphoproteins tropomyosin and glycogen phosphorylase a (in the presence of the inhibitor glucose) show that the resonances for the phosphoserine regulatory sites shift with pH. Analysis of line widths indicates that both residues have considerable mobility. These results are in agreement with studies on similar phosphorylated sites on other proteins, leading us to propose that mobility is a general feature of such regulatory sites. pH titration studies on a series of model compounds have indicated that an empirical correlation exists between the Hill coefficient n (a measure of the cooperativity of the titration curve) and the presence of charged groups in the vicinity of the phosphoryl moiety. Moreover, these studies showed that within one class of similarly substituted phosphorus compounds the chemical shifts, the titration behaviour, and the were comparable and allow for easy identification of these compounds. The values for phosphoser...