A calculational method is developed for spectrophotometric determination of stoichiometrics and individual equilibrium constants in the complexing of metal ions with metallochromic indicators. Implicit expressions are developed for the calculation of all parameters necessary to describe mixtures of 1 : 1, 1 : 2 and 2 : 1 metal-indicator complexes. The analysis of titration curves entails a seri...

Previously performed experiments showed that methylxanthines, especially caffeine, may protect cells against cytostatic or cytotoxic effects of several aromatic compounds. One of the proposed mechanisms of this protection is based on stacking interactions between pi electron systems of polycyclic aromatic molecules. In this work, we demonstrate that caffeine and other methylxanthines--pentoxify...

A rapid and sensitive technique, involving difference spectral titration with cobalt(III), to measure the epsilon values of chicken ovotransferrin, human serum transferrin, the N-lobe of human transferrin and several single point mutants is reported. The resulting epsilon values were compared with the values calculated from the equation proposed by Pace, Vajdos, Fee, Grimsley and Gray [(1995) P...

The base dependent binding of the cytotoxic alkaloid palmatine to four synthetic polynucleotides, poly(dA).poly(dT), poly(dA-dT).poly(dA-dT), poly(dG).poly(dC) and poly(dG-dC).poly(dG-dC) was examined by competition dialysis, spectrophotometric, spectrofluorimetric, thermal melting, circular dichroic, viscometric and isothermal titration calorimetric (ITC) studies. Binding of the alkaloid to va...

Teicoplanin, a new glycopeptide antibiotic belonging to the same family as vancomycin, inhibits cell wall synthesis in Bacillus subtilis; the inhibition is accompanied by an intracellular accumulation of UDP-N-acetyl-muramyl-pentapeptide. A cell-free system from Bacillus stearothermophilus, capable of synthesizing peptidoglycan, is 50% inhibited by teicoplanin at 40 micrograms/ml and 100% inhib...

A simple spectrophotometric method for the determination of tranexamic acid in pure form and pharmaceutical preparations was developed. The method is based on coupling tranexamic acid with 2,6-dichloroquinone-4-chlorimide (DCQ) in dimethyl sulfoxide (DMSO) to produce a colored product which absorbs maximally at wavelength ( ) 670nm. The molar ratio of tranexamic acid: DCQ is 2:1. Beer’s law is ...

A gas diffusion sequential injection system for spectrophotometric determination of free chlorine is described. The detection is based in the colorimetric reaction between free chlorine and a low toxicity reagent o-dianisidine. A gas diffusion unit is used to isolate free chlorine from the sample in order to avoid possible interferences. This feature results from the conversion of free chlorine...

Investigation of charge-transfer (CT) complexes of drugs has been recognized as an important phenomenon in understanding of the drug-receptor binding mechanism. Structural, thermal, morphological and biological behavior of CT complexes formed between drug quinidine (Qui) as a donor and quinol (QL), picric acid (PA) or dichlorodicyanobenzoquinone (DDQ) as acceptors were reported. The newly synth...

Separation methods used in organic chemistry are briefly reviewed, emphasis being placed on aspects that are frequently ignored, and special attention being paid to the analytical applications of separation. The relevance of physical, inorganic and analytical chemistry for organic chemistry is stressed. The term 'separation' can be used in analytical chemistry in both a literal and figurative s...

Iodometric Back Titration (IBT) and Spectrophotometric (SPM) determination are two commonly used methods for the determination of hydrogen sulfide (H2S) concentration in sea water. These two methods were applied in parallel for analysis of Black Sea anoxic waters and artificial solutions containing different H2S concentrations. The results of the SPM and IBT methods are in agreement when the H2...