Simultaneous kinetic determination of mixtures by on-line regression analysis

Willis, Barry G.; Woodruff, William H.; Frysinger, James R.; Margerum, Dale W.; Pardue, Harry L.

doi:10.1021/ac60294a026

Cited by 75 publications

(20 citation statements)

References 2 publications

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“…Programs written in the BASIC language served to step the spectrometer from one frequency to the next (typically 1-cm-1 intervals), and to average together several hundred data conversions at each frequency. Assembly language subroutines necessary for on-line operation were similar to those used previously (19) in kinetics studies.…”

Section: Methodsmentioning

confidence: 99%

Resonance Raman Spectra of Cobalt-Substituted Hemoglobin: Cooperativity and Displacement of the Cobalt Atom upon Oxygenation

Woodruff

Spiro

Yonetani

1974

Proc. Natl. Acad. Sci. U.S.A.

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The resonance Raman spectra of oxy and deoxy cobalt-substituted hemoglobin (CoHb) are reported. Comparison of these spectra to those of hemoglobin, methemoglobin, cytochrome c, and model cobalt porphyrin complexes suggests that the displacement of the cobalt atom upon oxygenation of CoHb is no greater than the out-of-plane distance in five-coordinate Co(II) porphyrins, 0.15 A. Combining this distance with the expected contraction of the cobalt-histidine bond, Ibers has estimated a maximum displacement of 0.37 A for the proximal histidine with respect to the heme plane upon oxygenation, about one-third the corresponding distance estimated for iron hemoglobin. The free energy of cooperativity for cobalt hemoglobin is also estimated to be onethird that of iron hemoglobin. These results are therefore consistent with Hopfield's distributed energy model, which predicts proportionality between proximal histidine displacement and the free energy of cooperativity. By implication they support Perutz's trigger mechanism for cooperativity.

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Section: Methodsmentioning

confidence: 99%

Resonance Raman Spectra of Cobalt-Substituted Hemoglobin: Cooperativity and Displacement of the Cobalt Atom upon Oxygenation

Woodruff

Spiro

Yonetani

1974

Proc. Natl. Acad. Sci. U.S.A.

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“…One of the two components in the analyte mixture is measured and the other is estimated by difference. Wills et al (1) have made error analyses of the kinetic method using similar instruments and have shown an error function sensitive to rate constants. For this reason, an aquo iron reference was prepared for each Fe-GSH solution in a set of measurements at a given p H and rate constants were estimated for these references in conjunction with the corresponding analytes.…”

Section: Methodsmentioning

confidence: 99%

“…Interest in kinetic methods of analysis using stopped flow spectrometers has developed recently (1)(2)(3). It is useful for identification of individual components of mixtures where components can react to give an easily detectabie common product such that differential rutes of reaction to that common product allow for distinction among components.…”

Section: Introductionmentioning

confidence: 99%

“…In the present case, it is only necessary to establish phenomenological rate constants for reaction of SSA with Fe(1Il) in each mediwn. The treatment is developed according to the approach of Wills et al (1). For two Fe(II1) species rcacting with SSA to form the strong red colour ( X , , , 500 nm) the observed absorbance as a function of time, P, is written:…”

Section: Introductionmentioning

confidence: 99%

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Kinetic and spectrophotometric studies of binding of iron(III) by glutathione

Khan¹,

Langford²

1976

Can. J. Chem.

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. Can. 9. Chem. 54, 3192 (1976).In this report, determination of unbound aquo iron species is accomplished by a kirretic n~et/7oc/involving reaction with sulfosalicylic acid (SSA) on a time ssale which is very short with respect to reaction of SSA with the glutathione complexes of iron. The data are used to calculate conditional binding constants for Fe(lI1) to glutathione. Binding constants in 0.1 M ionic strength media were obtained between p H 1 and 2.4 by the kinetic method. and near p H = 3 by spectrophotometry arrd by examillation of the ratio of rate of complex formation and dissociation. The conditional binding 'constant' betweetz p H 1 and 3 is represented as pK = -1.96 -O.5OpH. This is consistent with the importance of reactions involving only very limited proton release. Spectrophotometric data show that the -OH group on Fe(OH)*-is lost on glutathione complexing. Kinetics of the complex formation reaction between aquo iron(I1I) species and glutathione are slower than rates of reaction of iron (111) with simple ligands.The glutathione system is regarded as a model system important to natural water chemistry because it is a widely distributed biological sulfur-containing chelating agent. Des donnkes spectrophotomCtriques demontrent que le groupe OH du Fe(OH)2+ est perdu lors de la complexation avec du glutathion. La cinktique de la reaction de formation du complexe entre les espkces aquo-ferriques et le glutathion sont plus faibles que les vitesses de rkaction du fer(II1) avec des ligands simples.On considkre que le systkme de glutathion est un systkme n~odkle important pour la chinlie de l'eau naturelle parce que c'est un agent biologique chelata~~t contenant du soufre qui est distribui trks largement.[Traduit par le journal]

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“…Quantitative analysis of mixtures in which the spectra of the chemical constituents are known is best performed by the use of linear least squares procedures (Blackburn, 1965;Antoon et aL, 1977;Easterling, 1980, 1982;Christian and Tucker, 1982;Willis et aL, 1970;James, 1981). The mathematical foundations of these techniques can be found in an excellent article by Blackburn (1965), which includes a detailed example that can be worked out on a hand calculator.…”

Section: Least Squaresmentioning

confidence: 99%