On the Method of Continuous Variations.

Woldbye, Flemming; Lamm, C. G.; Risberg, Eilif; Lamm, Ole

doi:10.3891/acta.chem.scand.09-0299

Cited by 75 publications

(24 citation statements)

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“…The extrapolation of this method to obtain quantitative data on a series of complexes has been justly criticized (Woldbye, 1955). However, the qualitative detection of more than one complex is feasible.…”

Section: Resultsmentioning

confidence: 99%

Spectra of Molecular Complexes of Porphyrins in Aqueous Solution^*

Mauzerall¹

1965

Biochemistry

105

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The changes in the absorption and emission spectra of porphyrins in various molecular complexes in aqueous solution have been studied. These complexes are formed with a variety of molecules including large organic cations and planar neutral heterocyclic molecules. Spectral analysis by the method of continuous variation, the lack of isosbestic points, and a new analysis based on band widths all point to the formation of a series of complexes with several addends clustered about the porphyrin ring. Ionic and dispersion forces contribute to the stability of the complexes, but the water structure about these large hydrophobic molecules is an equally important factor. An estimate of the latter interaction based on interfacial tension is given.T he unique absorption spectra of the porphyrin pigments has allowed their identification and study throughout the biological realm. The large over-all variation of spectra with changes of structure has been used to identify these pigments. However, much information concerning the nonbonded or weakly bonded environment of these pigments remains untapped in minor spectral variations.In the course of experiments on the photoreactions of porphyrins, a marked effect of pyridinium salts (NAD' models) on the photochemistry was traced to the formation of complexes with the porphyrin. These complexes were found to occur with a wide class of compounds, many of biological importance. Their description is relevant to the problem of deciphering the effect of environment on porphyrin pigments in vivo. Moreover, some insight is gained into both the theory of porphyrin spectra and the binding of molecular complexes in aqueous solution. . This investigation was aided by a grant (GM 04922) from the U.S. Public Health Service.Abbreviation used in this work: NAD, nicotinamideadenine dinucleotide.The spectral changes, particularly the broadening of the Soret band and not of the red band I , are interpreted as a change in the nearly degenerate x and y components of the energy levels, and a model of the complex is derived.Studies at extreme dilution M), an analysis of the optical effects of aggregation on the spectra, and the absence of polarization of fluorescence all favor the view that the uroporphyrin is monomolecularly dispersed. A suggestion is made that such complexes occur in heme proteins as part of the phosphorylating mechanism and that the widespread occurrence of heterocyclic molecules in biological systems is related to the formation of complexes. otherwise stated, uroporphyrin isomer 111 or a mixture of isomers, mostly isomer 111, was used in this work. Most of the quaternary salts were synthesized in the laboratory and their melting points, analysis, and absorption spectra agreed with previously published data. Other compounds were the purest commercially available and were recrystallized when necessary, e.g., hexadecyltrimethylammonium bromide. The water was glass redistilled, and quantitative technique was used throughout. Absorption spectra were measured on a Cary Model 14 MR spectro...

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Section: Resultsmentioning

confidence: 99%

Spectra of Molecular Complexes of Porphyrins in Aqueous Solution^*

Mauzerall¹

1965

Biochemistry

105

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“…It is more reasonable to expect 34 that other complex species are also present in the solution, along with the principle 2:2:2 complex, when the complexation interaction is weak. In this case, the continuous variation curve loses its symmetric character (see curve 3a, Figure 4); and this inevitably will reflect on the reliability of the results 14,52,53 obtained by the Likussar-Boltz method. Table 4 shows that the influence of side reactions on the complex formation with INT can be neglected when the extraction is performed at the optimum conditions.…”

Section: Constants Of Extraction and Other Characteristics Concerningmentioning

confidence: 99%

Liquid-Liquid Extraction-Spectrophotometric Investigations of Three Ternary Complexes of Vanadium(V)

Gavazov¹,

Stefanova²

2014

Croat. Chem. Acta

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Abstract. Complex formation and liquid-liquid extraction (LLE) were studied in systems containing vanadium(V), 5-methyl-4-(2-thiazolylazo)resorcinol (TAO), tetrazolium salt (TZS), water and chloroform. The following three TZSs were used: 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT), 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chloride (Tetrazolium violet, TV), and 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT). Concentration of the reagents (TAO and TZS), pH of the aqueous medium, and shaking time were subjects of optimization experiments. Formation of ternary complexes with a composition of 2:2:2 was demonstrated by a set of different methods. Some key characteristics concerning the analytical application of the studied LLE-chromogenic systems were established as well.

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“…The method of continuous variations as modified by Woldbye (1955) was used. Beer-Lambert plots were obtained separately at 273 and 266 mp for penicilloic V acid and cupric chloride, and at 245 mp for penicilloic G acid and cupric chloride.…”

Section: Penicilloic Acid-cupric Ion Interactionsmentioning

confidence: 99%

Complexation of penicillins and penicilloic acids by cupric ion

Cressman

Sugita

Doluisio

et al. 1966

Journal of Pharmacy and Pharmacology

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A kinetic method was developed to study the interactions between cupric ion and penicillins G and V. Complexation was found to occur with the intact penicillins, followed by rapid hydrolysis of the complex into the corresponding penicilloic acidcupric ion complex. The logarithmic stability constants for the interaction between cupric ion and penicillins G and V were found to be 2.61 and 2.24, respectively. In addition, the method of continuous variation was used to determine the logarithmic stability constants for the cupric ion-penicilloic acid complexes. These were found to be 4.20 and 4-50, for penicilloic V and G acids respectively.NDER mildly acid conditions penicillins G and V have been shown U to be catalytically hydrolysed by cupric ion, into the corresponding penicilloic acids, at rates much too rapid for possible intact penicillincupric ion interactions to be measured by standard complexation techniques (Niebergall, Hussar, Cressman, Sugita & Doluisio, 1966). Therefore, a kinetic method was developed for determining the association constants for these interactions. Since the penicilloic acids were found to be the only degradation products produced under the conditions used, it also appeared desirable to determine their interactions with cupric ion. This was done spectrophotometrically using the method of continuous variation. Experimental REAGENTS AND EQUIPMENTAll the chemicals used were of reagent grade. The penicillin V (1530 units/mg) was supplied by Wyeth Laboratories, Inc. and the penicillin G (1595 units/mg) by the Eli Lilly Co. All solutions were made in water that had been deionised after distillation. In all work involving potentiometric titrations, the water was subsequently degassed by boiling for 30 min.Titrations were done automatically using the Radiometer TTT-lc titrator with the Radiometer Titragraph model SBR2c. Spectral curves were obtained using a Beckman model DB spectrophotometer with a Photovolt model 43 linear-log recorder. Single wavelength determinations were made using an Hitachi-Perkin Elmer spectrophotometer.Penicilloic acid solutions were made by the hydrolysis of penicillins at pH 12 for 15 min at room temperature in the manner described by Rapson & Bird (1963). The penicilloic acid solutions were adjusted to. pH 6-50 and either used or discarded within 4 hr of preparation.

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On the Method of Continuous Variations.

Cited by 75 publications

References 0 publications

Spectra of Molecular Complexes of Porphyrins in Aqueous Solution^*

Spectra of Molecular Complexes of Porphyrins in Aqueous Solution^*

Liquid-Liquid Extraction-Spectrophotometric Investigations of Three Ternary Complexes of Vanadium(V)

Complexation of penicillins and penicilloic acids by cupric ion

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On the Method of Continuous Variations.

Cited by 75 publications

References 0 publications

Spectra of Molecular Complexes of Porphyrins in Aqueous Solution*

Spectra of Molecular Complexes of Porphyrins in Aqueous Solution*

Liquid-Liquid Extraction-Spectrophotometric Investigations of Three Ternary Complexes of Vanadium(V)

Complexation of penicillins and penicilloic acids by cupric ion

Contact Info

Product

Resources

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Spectra of Molecular Complexes of Porphyrins in Aqueous Solution^*

Spectra of Molecular Complexes of Porphyrins in Aqueous Solution^*