Heterocyclic azo dyestuffs in analytical chemistry. A review

Anderson, R. G.; Nickless, G.

doi:10.1039/an9679200207

Cited by 209 publications

(59 citation statements)

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“…However, the introduction of a probe dependent on their interaction might signal their proximity in an "all-or-none" fashion. For this purpose, we have placed the arsanilazogroup on a single residue, Tyr 248, since such azophenols are well known to form zinc and other metal complexes, with a concomitant change in color from yellow or orange to red or purple (8). Indeed, the spectral characteristics of the apoarsanilazoenzyme and the zinc enzyme respectively, are closely similar to those of tetrazolylazo-N-carbobenzoxytyrosine and its zinc complex (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…It is well known that azophenols form colored metalcomplexes, which are useful as metal indicators (8). Fig.…”

Section: Resultsmentioning

confidence: 99%

“…We have now used diazotized arsanilic acid for the specific modification of tyrosine 248, an active-site residue of carboxypeptidase A (7). The resultant azophenol is capable of forming complexes with metal atoms (8) (2). Both the quantitation of amii)o-acid residues modified and the preparation of apoenzyme have been described (9).…”

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confidence: 99%

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Differences between the Conformation of Arsanilazotyrosine 248 of Carboxypeptidase A in the Crystalline State and in Solution

Johansen

Vallée

1971

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

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Coupling of carboxypeptidase A crystals with diazotized arsanilic acid specifically labels tyrosine 248, an active-site residue of the enzyme. Many azophenols are yellow and their zinc complexes are red; the "yellow" absorption spectrum of zinc arsanilazocarboxypeptidase crystals is characteristic of the arsanilazotyrosyl group, not of the zinc complex. This is consistent with the interpretation of x-ray data on native crystals of carboxypep, tidase A, indicating that tyrosine 248 and the zinc atom are too far apart to form a complex. However, the enzyme in solution is red, denoting the formation of a complex between zinc and arsanilazotyrosine 248. The most likely interpretation of the data is that the orientation of arsanilazotyrosine 248 in solution and in the crystal is different. If the unlabeled tyrosine 248 of native carboxypeptidase undergoes similar changes, these data may bear upon the low activity of the enzyme in the crystalline state and on the catalytic mechanism of the enzyme based on the crystal structure. The opportunities for analogous spectrochemical studies of other, similar systems are pointed out.The increasing importance of x-ray crystallography in studies of structure-function relationships of enzymes has generated considerable interest in the effect of crystallization on conformation. Knowledge of the relative conformations of enzymes in the solid state and in solution is now beginning to accumulate (1). For example, the properties of carboxypeptidase have been studied in particular detail from this point of view (2-4). The specific activity of carboxypeptidase in the crystalline state is only about 0.3% of that in solution. Further, the two physical states differ in the ease of zinc removal and in the enzymatic consequences of inorganic and organic modifications, though the basis of these phenomena has remained obscure. Hence, search for additional effects of the two states on conformation seemed indicated.We have emphasized the value of spectrochemical probes in the assessment of changes in local protein conformation. The coupling of tyrosyl residues with diazonium salts has proven particularly useful in this regard (5, 6). We have now used diazotized arsanilic acid for the specific modification of tyrosine 248, an active-site residue of carboxypeptidase A (7 METHODSA 50-fold molar excess of freshly prepared diazotized parsanilic acid was added to a suspension of carboxypeptidase crystals in 0.01 M KHCO3, pH 8.8, 00C and, after 3 hr, the reaction was stopped by centrifugation. The modified crystals were washed five times with metal-free water, suspended in 0.05 M Tris -HCl (pH 8.2), and fractionated as described by Richards et al. (2). Both the quantitation of amii)o-acid residues modified and the preparation of apoenzyme have been described (9). Tetrazolylazo-N-carbobenzoxytyrosine was prepared as described (10). Circular dichroic spectra were obtained with a Cary model 60 spectropolarimeter and absorption spectra with a Cary model 14R recording spectrophotometer. The absorpt...

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Section: Discussionmentioning

confidence: 99%

“…It is well known that azophenols form colored metalcomplexes, which are useful as metal indicators (8). Fig.…”

Section: Resultsmentioning

confidence: 99%

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Differences between the Conformation of Arsanilazotyrosine 248 of Carboxypeptidase A in the Crystalline State and in Solution

Johansen

Vallée

1971

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

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“…4-(2-piridylazo) resorcinol (PAR) is an important reagent of the nitrocompounds group, widely used as spectrometric reagent [8][9][10]. The main PAR advantage over other reagents is that their metallic compounds are soluble in water, simplifying the analytical procedure and avoiding subsequent stages of extraction with organic solvents.…”

Section: Introductionmentioning

confidence: 99%

Flow-batch analyser for preparation of calibration standard mixtures in simultaneous multicomponent spectrometric analysis

et al. 2009

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The application of multivariate calibration techniques to multicomponent analysis by UV-VIS molecular absorption spectrometry is a powerful tool for simultaneous determination of several chemical species. However, when this methodology is accomplished manually, it is slow and laborious, consumes high amounts of reagents and samples, is susceptible to contaminations and presents a high operational cost. To overcome these drawbacks, a flow-batch analyser is proposed in this work. This analyser was developed for automatic preparation of standard calibration and test (or validation) mixtures. It was applied to the simultaneous determination of Cu2+, Mn2+ and Zn2+ in polyvitaminic and polymineral pharmaceutical formulations, using 4-(2-piridilazo) resorcinol as reagent and a UV-VIS spectrophotometer with a photodiode array detector. The results obtained with the proposed system are in good agreement with those obtained by flame atomic absorption spectrometry, which was employed as reference method. With the proposed analyser, the preparation of calibration and test mixtures can be accomplished about four hours, while the manual procedure requires at least two days. Moreover, it consumes smaller amounts of reagents and samples than the manual procedure. After the preparation of calibration and test mixtures, 60 samples h-1 can be carried out with the proposed flow-batch analyser.

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“…The derivatives of thiazolylazophenols have often been referred because of their easier preparation (1,2). For extractive applications, reagents with one -OH group have been primarily utilized because they form uncharged complexes.…”

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confidence: 99%

Extractive-photometric Investigation of Cadmium Chelates of 4-(2-Thiazolylazo)-resorcinol (TAR)

Navrátil¹,

Frei²

1971

Can. J. Chem.

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A quantitative interpretation of the extractive distribution of cadmium chelates of TAR (= H2A) between liquid organic and water phases has been made and two groups of extractable species have been determined: (a) uncharged complexes of the type CdA in which co-ordinated water is replaced by suitable uncharged organic base (2,9-dimethyl-1,lO-phenanthroline) and (b) charged complexes CdAZ2-which are extracted as ionic pairs in the presence of charged organic bases.The evaluation of the character of the bases and the effect of p H and the nature and concentration of other inorganic anions are presented.

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Heterocyclic azo dyestuffs in analytical chemistry. A review

Cited by 209 publications

References 0 publications

Differences between the Conformation of Arsanilazotyrosine 248 of Carboxypeptidase A in the Crystalline State and in Solution

Differences between the Conformation of Arsanilazotyrosine 248 of Carboxypeptidase A in the Crystalline State and in Solution

Flow-batch analyser for preparation of calibration standard mixtures in simultaneous multicomponent spectrometric analysis

Extractive-photometric Investigation of Cadmium Chelates of 4-(2-Thiazolylazo)-resorcinol (TAR)

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