Spectrophotometric titration studies and ultraviolet difference spectra are two techniques which have been used in recent years for determining what role, if any, the tyrosine residues in a protein play in maintaining the secondary and tertiary structure of proteins. Crammer and Neuberger (2) utilized a spectrophotometric procedure to investigate the ionization of phenolic groups in ovalbumin a...

A simple sequential injection analysis (SIA) with spectrophotometric detection for an assay of acidity in fruit juice was investigated. An alkaline reagent (sodium hydroxide), a sample and an indicator (phenolphthalein) were first aspirated and stacked as adjacent zones in a holding coil. With flow reversal through a reaction coil to the detector, zone penetration occurred, leading to a neutral...

We have utilized 11beta-hydroxylase activity and visible absorption spectrophotometry to detect possible complex formation among adrenodoxin reductase, adrenodoxin, and cytochrome P-450(11)beta. At low ionic strength, a 1:1 complex between adrenodoxin reductase and adrenodoxin occurs but does not support maximal rates of 11beta hydroxylation; at least 1 additional molecule of adrenodoxin in exc...

The formation of complexes of Zn(II), Cd(II), Hg(II), and Pb(II) and N -carboxymethylD,L-threonine (H2CMT, H2L) in aqueous solutions has been studied by spectrophotometric and potentiometric methods. The complexation model for each system has been established by the HYPERQUAD program from the potentiometric data. Three different behaviors are found: ML2H, MLH, ML, MLOH, and ML2 complexes are fo...

The proposed approach relies on successive dilution of a solution containing a sample with standard addition and on titration of the solutions obtained until receiving a signal lower than the signal measured for the sample alone. Equations are derived for subsequent dilution factors for the automatic flow injection system applied. The overall calibration strategy including the possibility of pr...

The methods for determination of chitosan content recommended in the Chinese Pharmacopoeia and the European Pharmacopoeia are not applicable for evaluation of the extent of deacetylation (deacetylation degree, DD) in chitooligosaccharides (COS). This study explores two different methods for assessment of DD in COS having relatively high and low molecular weights: an acid-base titration with bro...

The presented review is devoted to analytical applications of reactions of Fe(III) and K(3)[Fe(CN)(6)] with 2,10-disubstituted phenothiazines (PT). It was found that iron(III) and hexacyanoferrate(III) ions in acidic media easily oxidized PT with the formation of colored oxidation products. This property has been exploited for spectrophotometric determination of iron(III) ions and phenothiazine...

In this paper, a comprehensive study has been made on the detection of free fatty acids (FFAs) in palm oil via an optical technique based on enzymatic aminolysis reactions. FFAs in crude palm oil (CPO) were converted into fatty hydroxamic acids (FHAs) in a biphasic lipid/aqueous medium in the presence of immobilized lipase. The colored compound formed after complexation between FHA and vanadium...

Cyclic voltammetric reduction of c60 to the radical anion, c60-, is unaffected by the presence of weak proton donors in o-dichlorobenzene, indicating that the monoanion is a weak base. Further reduction to the dianion results in a drastic increase in basicity, and an estimate of the acidity of the conjugate acid, C60H-, is obtained. Bulk electrolysis studies allow further characterization of th...

Protonation of a free-base meso-pyrimidinyl-substituted AB(2)-corrole (H(3)AB(2)) in ethanol solution by stepwise addition of sulfuric acid has been studied in the temperature range from 293 to 333 K. The formation rate of protonated species was found to depend profoundly on the temperature at which the titration was undertaken. Two steps in the titration curve were identified at temperatures a...