Window factor analysis of methylene blue in water

Zhao, Zhouming; Malinowski, Edmund R.

doi:10.1002/(sici)1099-128x(199903/04)13:2<83::aid-cem529>3.0.co;2-2

Cited by 25 publications

(19 citation statements)

References 14 publications

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“…On the basis of our previous studies involving window factor analysis of MB in pure aqueous m edia, 10 we believe the three species in set B consist of a hydrated monomer, a hydrated dimer, and the anhydrated m onomer whose spectrum is portrayed in Fig. 1.…”

Section: Resultsmentioning

confidence: 91%

“…This spectrum is different from the absorptivity spectrum of MB in water reported in our earlier study. 10 In the sections that follow, we deduce the empirical form ula of this anhydride.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, a chemometric technique called window factor analysis (WFA) 8,9 has been developed for the purpose of studying complex formation in aqueous solution. In an earlier investigation, 10 we used this m odel-free technique to extract the concentration pro® les of the three MB species and found that the trimer contains one chlorine atom, (MB) 3 Cl 1 1 , with a formation constant of 3.2 3 10 2 11 M 3 .…”

Section: Introductionmentioning

confidence: 99%

“…Although water is necessar y for m ethylene blue aggregation, there has been no quantitative measurem ent of this aspect. During our previous studies of MB in aqueous m edia, 10 we did not consider hydration, because the concentration of water was so large that it was essentially constant throughout the spectral measurem ents, precluding any information concerning the extent of the hydration. With the addition of methanol to the system, the concentration of water can be m ade to var y from 0% to 100%.…”

Section: Introductionmentioning

confidence: 99%

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Determination of the Hydration of Methylene Blue Aggregates and Their Dissociation Constants Using Visible Spectroscopy

Zhao

Malinowski

1999

Appl Spectrosc

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The visible spectra of methylene blue (MB) in aqueous-methanol solutions were used to determine the extent of hydration of MB aggregates. The investigation was carried out at MB concentrations of 1.000 × 10−4 M and 1.000 × 10−3 M. Abstract factor analysis (AFA) was used to determine the number of chemical species responsible for the spectral data. The species were identified as aqueous MB monomer, dimer, and trimer, and a methanoic MB monomer. The absorptivity spectra of the aqueous MB species obtained from the previous studies were used to extract their concentration profiles in methanol–water mixtures. With the addition of methanol to the aqueous solvent, the concentration of water could be varied from 0% to 100%. This variation was used to determine the extent of hydration and solvation of each of the four MB species, as well as their mutual equilibria. The species were identified as (1) MB+CH3OH, MB monomer monomethanol; (2) MB+H2O, MB monomer monohydrate; (3) (MB)2++ 6H2O, MB dimer hexahydrate; and (4) (MB)3Cl++ (H2O)13, MB trimer monochloro tridecahydrate. The dissociation constants for the hydrated monomer, dimer, and trimer were determined to be 0.48, 1.29 × 103 M5 and 7.2 × 106 M13, respectively.

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Section: Resultsmentioning

confidence: 91%

“…This spectrum is different from the absorptivity spectrum of MB in water reported in our earlier study. 10 In the sections that follow, we deduce the empirical form ula of this anhydride.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determination of the Hydration of Methylene Blue Aggregates and Their Dissociation Constants Using Visible Spectroscopy

Zhao

Malinowski

1999

Appl Spectrosc

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“…In fact, there is no linear relationship between the absorbance and the concentration of methylene blue, because it tends to form dimers and trimers. 23,52 Despite the wide application of the methylene blue method, there is a colorimetric assay closely related to it that presents some improvements. This alternative reaction involves the formation of ethylene blue starting from sulphide and N,N-diethyl-pphenylenediamine.…”

Section: A Colorimetric Methodsmentioning

confidence: 99%

Hydrogen sulphide: novel opportunity for drug discovery

Martelli

Testai

Breschi

et al. 2010

Medicinal Research Reviews

152

128

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Hydrogen sulphide (H(2)S) is emerging as an important endogenous modulator, which exhibits the beneficial effects of nitric oxide (NO) on the cardiovascular (CV) system, without producing toxic metabolites. H(2)S is biosynthesized in mammalian tissues by cystathionine-β-synthase and cystathionine-γ-lyase. H(2)S exhibits the antioxidant properties of inorganic and organic sulphites, behaving as a scavenger of reactive oxygen species. There is also clear evidence that H(2)S triggers other important effects, mainly mediated by the activation of ATP-sensitive potassium channels (K(ATP)). This mechanism accounts for the vasorelaxing and cardioprotective effects of H(2)S. Furthermore, H(2)S inhibits smooth muscle proliferation and platelet aggregation. In non-CV systems, H(2)S regulates the functions of the central nervous system, as well as respiratory, gastroenteric, and endocrine systems. Conversely, H(2)S deficiency contributes to the pathogenesis of hypertension. Likewise, impairment of H(2)S biosynthesis is involved in CV complications associated with diabetes mellitus. There is also evidence of a cross-talk between the H(2)S and the endothelial NO pathways. In particular, recent observations indicate a possible pathogenic link between deficiencies of H(2 S activity and the progress of endothelial dysfunction. These biological aspects of endogenous H(2)S have led several authors to look at this mediator as "the new NO" that has given attractive opportunities to develop innovative classes of drugs. In this review, the main biological actions of H(2)S are discussed. Moreover, some examples of H(2)S-donors are shown, as well as some hybrids, in which H(2)S-releasing moieties are added to well-known drugs, for improving their pharmacodynamic profile or reducing the potential for adverse effects, are reported.

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Dedicated to Edmund R. Malinowski. Secondary, model‐based examination of model‐free analysis results: Making the most of soft‐modelling outcomes

Maeder

2023

Journal of Chemometrics

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Edmund R. Malinowski is well known for his factor analysis‐based work; he is clearly less well known for his chemical model‐based analyses of chemical data. In this contribution, we discuss the, at the time innovative, idea of subjecting the primary model‐free analysis results to a secondary quantitative model‐based evaluation. Two examples from his research serve as illustrations: the complexation of Cu2+ with cyclodextrin and the dimerisation and trimerisation of methylene blue. In both examples, the spectrophotometric titration data are first analysed by window factor analysis, WFA, resulting in the concentration profiles. These primary, model‐free results allowed Malinowski to gain qualitative insight in the chemical processes. Additional quantitative analyses of the concentration profiles, based on the previously obtained reaction model, resulted in the numerical values of the underlying equilibrium constants. This contribution relates and compares this methodology with alternative ways of analysing the same data.

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Window factor analysis of methylene blue in water

Cited by 25 publications

References 14 publications

Determination of the Hydration of Methylene Blue Aggregates and Their Dissociation Constants Using Visible Spectroscopy

Determination of the Hydration of Methylene Blue Aggregates and Their Dissociation Constants Using Visible Spectroscopy

Hydrogen sulphide: novel opportunity for drug discovery

Dedicated to Edmund R. Malinowski. Secondary, model‐based examination of model‐free analysis results: Making the most of soft‐modelling outcomes

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