Characteristics of Polarographic Catalytic Waves Observed with Bovine-Serum Albumin: Kinetic or Diffusion Control

Kolthoff, I. M.; Yamashita, Kazuo; Hie, Tan Boen; Kanbe, Akira

doi:10.1073/pnas.70.7.2020

Cited by 14 publications

(7 citation statements)

References 4 publications

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“…The above medium originally proposed by Brdička [2] does not seem to be the best for the analysis of proteins because of its poorly controlled and rather high pH (about 9.5). Different media were therefore suggested by other authors [19,[26][27][28][29][30][31]. Here we use the medium containing 1 mM [Co(NH 3 ) 6 ] 3þ in glycine buffer, pH 8.5 [32].…”

Section: Catalytic Hydrogen Reduction In Cobalt-containing Solutionsmentioning

confidence: 99%

Constant Current Chronopotentiometric Stripping Analysis of Bioactive Peptides at Mercury and Carbon Electrodes

et al. 1998

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Constant current derivative chronopotentiometric stripping analysis (CPSA) was used to study bioactive peptides [Lys 8 ]-vasopressin and angiotensin II at carbon paste electrode (CPE) and hanging mercury drop electrode (HMDE). Both peptides contain a single tyrosine residue which is oxidized at CPE close to þ0.6 V (against Ag/AgCl/3 M KCl electrode) producing peak Y; this peak was by about 15 mV more positive in vasopressin than in angiotensin II. At HMDE vasopressin yielded peak S due to the reduction of the disulfidic bond in the peptide. No peak S was observed with angiotensin II as it does not contain any cystine/cysteine residues. Vasopressin produced different catalytic hydrogen reduction signals in media with cobalt ion and in media not containing any metal ion. The signal produced in the latter media (peak H), which appeared close to ¹1.7 V, was well separated from the background. No catalytic hydrogen reduction signal was obtained with angiotensin II. The above mentioned CPSA signals can be applied for the determination of the respective peptide at nanomolar concentrations. The least sensitive peak S appears which requires at least 100 nM vasopressin concentration at moderate accumulation time. By two orders of magnitude, higher sensitivities can be obtained with peaks Y and H. In measuring these peaks CPSA shows significant advantages over the voltammetric stripping techniques.

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Section: Catalytic Hydrogen Reduction In Cobalt-containing Solutionsmentioning

confidence: 99%

Constant Current Chronopotentiometric Stripping Analysis of Bioactive Peptides at Mercury and Carbon Electrodes

et al. 1998

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“…This is particularly true with reference to Brdicka currents, the magnitude of which is determined by the rates of several reactions which occur on the surface of the mercury drop (3,4 (10) concluded that the desorption potential of 0.05 mM tetrabutylammonium sulfate in 5 mM sodium sulfate is of the order of -1.6 V and that this potential becomes more negative at larger concentrations. These authors could not observe clearly the desorption potential of tetraethylammonium ions.…”

Section: Discussionmentioning

confidence: 99%

“…Characteristics of Brdicka currents (3)(4)(5)(6) and of presodium currents (7) under various conditions, also in the presence of various concentrations of urea (8), have been presented in previous publications. A few experiments have also been carried out on the effects on Abbreviations: BSA, bovine-serum albumin; TEAP, tetraethylammonium perchlorate; TMAC, tetramethylammonium chloride; TEAC, tetraethylammonium chloride; TPAB, tetrapropylammonium bromide; TBAB, tetrabutylammonium bromide; SCE, saturated calomel electrode; DME, dropping mercury electrode; -ipL presodium current.…”

mentioning

confidence: 99%

Effects of tetraalkylammonium salts on Brdicka and presodium currénts of bovine-serum albumin.

Kolthoff¹,

Yamashita²

1975

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

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Tetraethyl-, tetrapropyl-, and tetrabutylammonium ions are capillary-active on the interface water-mercury. In the adsorbed state they increase Brdicka and presodium currents. These currents drop sharply at potentials where tetrabutylammonium ions are desorbed, these potentials being -1.60, -1.66, -1.72, and -1.79 V versus the saturated calomel electrode (SCE) at tetrabutylammonium concentrations of 0.1, 0.25, 1, and 5 mM, respectively. Indications are that tetraethylammonium ions at a concentration of 50 mM are desorbed at a potential of the order of -1.9 V (versus SCE). Tetraethyl-, tetrapropyl-, and tetrabutylammonium salts are adsorbed from aqueous solutions on the surface of mercury. Mairanovskii and Churilina (1) report that these tetraalkylammonium ions have a significant effect on the kinetics and mechanism of electrode processes. Pungor and Farsang (2) found that at low concentrations tetraalkylammonium salts cause an increase in the catalytic hydrogen waves (comparable to "presodium" currents of bovine-serum albumin, BSA) of quinine, nicotinamide, and methylene blue in phosphate buffers. In order to explain the results by these authors, Mairanovskii et al. (1) studied the effect of tetraethylammonium perchlorate (TEAP) on catalytic hydrogen waves observed with pyridine and 2,6-lutidine in various buffers at the dropping mercury electrode. Under specified conditions they found an increase of the catalytic waves at concentrations of TEAP (10-40 mM). In general, they attribute the effect of TEAP to a retardation of electrochemical reactions by a film of cations adsorbed on the electrode, by a change in the electrokinetic potential, and by a specific action which is not completely understood.It appeared of interest to study the effects of tetraalkylammonium salts on Brdicka and presodium currents observed with BSA in various buffers. Characteristics of Brdicka currents (3-6) and of presodium currents (7) under various conditions, also in the presence of various concentrations of urea (8), have been presented in previous publications. A few experiments have also been carried out on the effects on Abbreviations: BSA, bovine-serum albumin; TEAP, tetraethylammonium perchlorate; TMAC, tetramethylammonium chloride; TEAC, tetraethylammonium chloride; TPAB, tetrapropylammonium bromide; TBAB, tetrabutylammonium bromide; SCE, saturated calomel electrode; DME, dropping mercury electrode; -ipL presodium current.Brdicka and presodium currents of BSA of tetraphenylarsonium ions, tetramethylguanidine, and diphenylguanidine, all capillary-active on the interface mercury-water. Finally, the effect of tetrabutylammonium ions on Brdicka currents of cysteine in the presence of cobalt(II) is described. EXPERIMENTAL Samples of BSA and several chemicals used have been described previously (3). Tetramethylammonium chloride (TMAC), tetraethylammonium chloride (TEAC), tetrapropylammonium bromide (TPAB), and tetrabutylammonium bromide (TBAB) were pure products from various firms. Details regarding the polarograph used and th...

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“…With cobalt(II) the same pattern was observed as with Co(III), the currents again being some 10-20% smaller than with Co(III). The difference between the effects of calcium upon Brdicka currents with native BSA and BSA in 8 M urea is particularly striking in a buffer 0.02 M in ammonium chloride and 1 complex, and being more rapidly electroreduced, than in ammonia buffers (2, 3).…”

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confidence: 94%

Brdicka currents observed with bovine serum albumin and completely reduced bovine serum albumin in the presence of urea.

Kolthoff¹,

Yamashita²,

Hie³

1975

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

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In ammonia buffers of varying composition and pH, native bovine serum albumin and completely reduced bovine serum albumin, denoted by G'(SH) 35, yield quite different Brdicka current-voltage (i-E) curves, but they are identical in the presence of 5 mM calcium chloride. This means that in the presence of calcium, bovine serum albumin becomes completely reduced to (P(SH)35. In 8 M urea and ammonia buffers the Brdicka i-E patterns of serum albumin and (P(SH)35 are identical even in the absence of calcium, the effect of calcium on the first wave being negligible while calcium slightly increases the second wave. The maximum polarographic effect is attained at urea concentrations of about 5-6 M. Quite generally, the appearance of a second Brdicka wave is attributed to complexation of Co(II) with S -and a group of ligands that is different on the second than on the first wave. The effect of calcium on Brdicka currents of bovine serum albumin in the absence of urea is attributed to an orientation of the protein on the surface of the electrode such that all disulfide groups are reduced and with' other ligands can complex with Co(II). Denaturation of bovine serum albumin in buffers with a pH less than 10.5, and which are 8 M in urea, is (polarographically) completely reversible if dilution is made within 15 minutes after preparation. Changes in Brdicka i-E patterns upon longer aging at varying pH are attributed-in part at least-to dimerization of the denatured protein by interaction of -S-in one molecule with -S-S-in another.In previous papers (1-4) Brdicka currents observed under various conditions in different buffers with native bovine serum albumin (BSA) and presodium currents (5) with native and modified BSA have been reported and a chain mechanism for the qualitative interpretation of the effects of pH and the kind of buffer on Brdicka currents has been proposed (3). Quite generally it was found that small concentrations of calcium (chloride) as well as magnesium greatly increase the total catalytic currents, or in buffers with two Brdicika waves, the second one, and also affect the shape of current-voltage curves in the voltage range in which Brdicka currents are observed (denoted as Brdicka i-E curves). It appeared of interest to investigate the effect of urea on Brdicka and presodium currents (5). For many years it has been known that urea in concentrations of 6-8 M is a denaturant of proteins, including BSA. Although the interpretation of the mechanism of this denaturation, and particularly the effect of urea on the structure of the protein, is incompletely understood (1-4), which yielded similar polarograms. All chemicals were C.P. products and the same, or of the same quality, as those used previously (1-5).Apparatus and Technique. These were the same as described previously (1-4). Unless stated otherwise, the currents in the presence of larger concentrations of urea have been corrected for viscosity of solutions by multiplying the observed currents by 1.1, 1.2, or 1.3 for 3, 6, or 8 M urea solutio...

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Characteristics of Polarographic Catalytic Waves Observed with Bovine-Serum Albumin: Kinetic or Diffusion Control

Abstract: Conditions are described under which the catalytic Brdicka currents observed in ammoniacal buffer solutions containing cobalt(III) hexammine chloride or cobalt(II) and very little bovine-serum albumin (0.1-0.2

Cited by 14 publications

References 4 publications

Constant Current Chronopotentiometric Stripping Analysis of Bioactive Peptides at Mercury and Carbon Electrodes

Constant Current Chronopotentiometric Stripping Analysis of Bioactive Peptides at Mercury and Carbon Electrodes

Effects of tetraalkylammonium salts on Brdicka and presodium currénts of bovine-serum albumin.

Brdicka currents observed with bovine serum albumin and completely reduced bovine serum albumin in the presence of urea.

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