Spectrophotometric Determination of Microquantities of Iodine

Custer, J. J.; Natelson, Samuel

doi:10.1021/ac60032a040

Cited by 95 publications

(27 citation statements)

References 36 publications

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“…Solutions of HOCl of the required concentration and pH were freshly prepared from a 0.15 M NaOCl stock solution and standardized iodometrically [15,16]. The other reagents were of analytical grade from P.O.Ch.…”

Section: Muterialsmentioning

confidence: 99%

N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H₂O₂/Cl⁻ System

Stelmaszyńska¹,

Zgliczyński²

1978

European Journal of Biochemistry

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The chlorination of dipeptides by the myeloperoxidase/H20~/C1-system takes place at the N-terminal amino group, whereas no chlorination of the amide nitrogen of the peptide bond can be observed. The N-terminal amino group is chlorinated to N-monochloroamine or/and N-dichloroamine. N-Monochloropeptides were the main products at higher pH values, at lower pH a mixture of N-monochloropeptides and N-dichloropeptides was formed owing to the dismutation of N-monochloroamine to N-dichloroamine.N-Monochloropeptides decompose, yielding NH3 and the corresponding N-(2-oxoacyl)amino acids. N-Dichlorodipeptides decompose faster but to nitriles and the free C-terminal amino acids. N-Dichloroglycyl-amino acid decomposes through a relatively stable intermediate (cyano-formylamino acid) to hydrogen cyanide, cyanogen chloride and the free C-terminal amino acid. lnsulin chlorination also yields N-terminal glycyl and phenylalanyl N-monochloro derivatives, which deaminate to glyoxylyl and phenylpyruvyl residues.Myeloperoxidase of polymorphonuclear neutrophilic granulocytes catalyses the oxidation of CIions to HOCl by hydrogen peroxide [1-31. The chlorinating ability of myeloperoxidase seems to be important for the bactericidal mechanisms of neutrophils [4-61. The physiological role of the chlorination process was emphasized by its discovery in granulocytes undergoing phagocytosis [7]. Peptides and proteins may be target substrates for chlorination during phagocytosis. The incorporation of 36Cl into bovine albumin by purified myeloperoxidase was reported [7].From the chemical point of view, many different functional groups in protein are susceptible to HOCl attack : e.g. amino, imidazolium, guanidinium, indole residues, phenolic rings and the amide nitrogen of peptide bonds. In the enzymatic reaction, however, HOCl production by myeloperoxidase is impaired when the chlorination or oxidation of the HOClreactive substrate is slower than that of the enzyme itself. In such cases autodestruction of niyeloperoxidase occurs.Abbreviations. AcAla, N-acetyl-alanine; CIGly-Leu, N-monochloroglycyl-leucine; CIAla-Ala, N-monochloroalanyl-aianine; ClLeu-Gly, N-monochloroleucyl-glycine; ClzCly-Leu, N-dichloroglycyl-leucine.Enzyme. Myeloperoxidase (EC 1.11.1.7).It was established that amino compounds are effective acceptors of C1' ions formed in myeloperoxidase-mediated reactions [2,8] and protect myeloperoxidase against HOCl attack [9].Preliminary examination of bovine albumin chlorination by the myeloperoxidase system showed that 36Cl incorporated into protein was to a great extent K1-reactive, i.e. N-CI bonds were formed. These results focussed attention on the chlorination of the protein amino groups (N-terminal and 8-lysine amino groups) and the amide nitrogen of peptide bonds.It seemed reasonable to start the systematic elucidation of protein chlorination by examining the reactions of simple dipeptides without side-chain functional residues. This made it possible to check the reactions only of N-terminal amino groups and of the peptidebond ami...

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Section: Muterialsmentioning

confidence: 99%

N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H₂O₂/Cl⁻ System

Stelmaszyńska¹,

Zgliczyński²

1978

European Journal of Biochemistry

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“…The spectrophotometric method makes use of the color of the I -I 2 couple. The color of the resulting solution Ϫ 3 is quantified in a spectrophotometer, which can analyze it at several wavelengths (Custer and Natelson 1949).…”

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confidence: 99%

Rapid and precise determination of dissolved oxygen by spectrophotometry: Evaluation of interference from color and turbidity

Roland

Caraco

Cole

et al. 1999

Limnology & Oceanography

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Several researchers have proposed spectrophotometric modifications of the Winkler titrimetric method for measuring dissolved oxygen (DO). These modifications, although simple, are not widely used because of concern about accuracy, calibration, and possible sources of interference. Here we show, using natural samples from lakes and rivers as well as samples manipulated in the laboratory, that the spectrophotometric method can provide accurate and very precise measurements of DO over a wide range of concentrations (4 to ∼13 mg O2 liter−1). Further, interference from dissolved organic carbon (color) and turbidity are minor. We propose corrections for both color and turbidity, where necessary, that can be easily incorporated into the measurement design. Because of the speed and simplicity of the spectrophotometric method, it is easy to replicate measurements and thereby increase precision without greatly increasing analytical time. In 10 min of effort, we were able to achieve a coefficient of variation (CV) within one bottle of 0.09%, or 0.8% among different bottles. With n = 7 bottles, one can easily distinguish changes in DO of 0.05 mg liter−1 with this method, which makes it useful for metabolic studies in many environments. To achieve a comparable CV by conventional titration would require about 100 min of effort.

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“…A modification of this procedure uses a spectrophotometer to measure the iodine concentration by determining the absorption of the triiodide ion formed by addition of excess iodide [66].…”

Section: Quality Specifications and Testingmentioning

confidence: 99%

Bromine

Mills

Frim

Ukeles

et al. 2015

Ullmann's Encyclopedia of Industrial Chemistry

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Spectrophotometric Determination of Microquantities of Iodine

Cited by 95 publications

References 36 publications

N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H₂O₂/Cl⁻ System

N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H₂O₂/Cl⁻ System

Rapid and precise determination of dissolved oxygen by spectrophotometry: Evaluation of interference from color and turbidity

Bromine

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Spectrophotometric Determination of Microquantities of Iodine

Cited by 95 publications

References 36 publications

N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H2O2/Cl− System

N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H2O2/Cl− System

Rapid and precise determination of dissolved oxygen by spectrophotometry: Evaluation of interference from color and turbidity

Bromine

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N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H₂O₂/Cl⁻ System

N‐(2‐Oxoacyl)amino Acids and Nitriles as Final Products of Dipeptide Chlorination Mediated by the Myeloperoxidase/H₂O₂/Cl⁻ System