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>3.3.co;2-u

Cited by 7 publications

(18 citation statements)

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“…In addition, Zhao and Malinowski determined the dissociation constant of trimer (3.2 × 10 -11 L 3 mol -3 ) by a window factor analysis, suggesting that one chlorine anion is incorporated into the trimer structure. The molar absorption coefficients for monomer, dimer, and trimer were reported within 4−9 × 10 4 M -1 cm -1 . The spectral characteristics of higher aggregates are distinct from each other indicating the strong π-interactions among MB molecules; the self-organization is promoted by electrostatic and dispersion forces as well as by hydrophobic effects.…”

Section: Introductionmentioning

confidence: 92%

Aggregation of Methylene Blue in Frozen Aqueous Solutions Studied by Absorption Spectroscopy

2005

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The paper presents a qualitative as well as quantitative spectroscopic study of methylene blue (MB) aggregation that occurs upon freezing the aqueous solutions over a wide concentration range. The Gaussian curve analysis and the multivariate curve resolution-alternating least squares method were used to determine the number and concentration of chemical species responsible for the overlaying absorption visible spectra measured. The results show the extent of aggregation for the concentrations above 10(-7) mol L(-1), being dependent on the freezing rate and the initial concentration. While the local concentration of MB at the grain boundaries of polycrystalline ice increased by approximately 3 orders of magnitude upon fast freezing at 77 K compared to the liquid phase, the concentration raised at least by 6 orders of magnitude upon slow freezing at 243 K. Since enhancement of the local concentration of solutes plays an important role in (photo)chemical transformations in solid aqueous media, this work helps to understand how the initial conditions control the course of the process. The results are relevant in other interdisciplinary fields, such as environmental chemistry, cosmochemistry, or geochemistry.

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Section: Introductionmentioning

confidence: 92%

Aggregation of Methylene Blue in Frozen Aqueous Solutions Studied by Absorption Spectroscopy

2005

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“…Close examination of the methylene blue method under the aforementioned conditions shows that methylene blue does not obey Beer's Law at concentrations greater than 1 μM due to the formation of dimer and trimer species. [6, 47] Additionally, formation of methylene blue occurs in the presence of a variety of sulfur species, including thiols, a common trigger of synthetic H 2 S donors, further complicating analysis. [46] Therefore, control experiments must be conducted to properly account for methylene blue derived from the H 2 S donor of interest compared with other potential sources.…”

Section: Measuring H2s Release Kineticsmentioning

confidence: 99%

A review of hydrogen sulfide (H2S) donors: Chemistry and potential therapeutic applications

Powell

Dillon

Matson

2018

Biochemical Pharmacology

459

319

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Hydrogen sulfide (HS) is a ubiquitous small gaseous signaling molecule, playing an important role in many physiological processes and joining nitric oxide and carbon monoxide in the group of signaling agents termed gasotransmitters. Endogenous concentrations of HS are generally low, making it difficult to discern precise biological functions. As such, probing the physiological roles of HS is aided by exogenous delivery of the gas in cell and animal studies. This need for an exogenous source of HS provides a unique challenge for chemists to develop chemical tools that facilitate the study of HS under biological conditions. Compounds that degrade in response to a specific trigger to release HS, termed HS donors, include a wide variety of functional groups and delivery systems, some of which mimic the tightly controlled endogenous production in response to specific, biologically relevant conditions. This review examines a variety of HS donor systems classified by their HS-releasing trigger as well as their HS release profiles, byproducts, and potential therapeutic applications.

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“…This assay, widely used with biological samples, such as plasma, is not devoid of limitations and faults because, besides the extreme toxicity and chemical instability of N,N ‐dimethyl‐ p ‐phenylenediamine, it shows an intrinsic problem due to the fact that the absorption spectra of aqueous solutions of methylene blue do not obey Beer's law at the concentration typically obtained during this assay on biological samples. In fact, there is no linear relationship between the absorbance and the concentration of methylene blue, because it tends to form dimers and trimers . Despite the wide application of the methylene blue method, there is a colorimetric assay closely related to it that presents some improvements.…”

Section: Determination Of Hydrogen Sulphide In Biological Samplesmentioning

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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Window factor analysis of methylene blue in water

Cited by 7 publications

References 0 publications

Aggregation of Methylene Blue in Frozen Aqueous Solutions Studied by Absorption Spectroscopy

Aggregation of Methylene Blue in Frozen Aqueous Solutions Studied by Absorption Spectroscopy

A review of hydrogen sulfide (H2S) donors: Chemistry and potential therapeutic applications

Hydrogen sulphide: novel opportunity for drug discovery

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