Organocation speciation. II. Methylene blue photosensitization as a model for speciation and toxicity of herbicides

A chemical model that employs the photosensitization properties of methylene blue to mimic herbicide toxicity is used to test size separation as a method of chemical speciation. A spectrophotometric study of the dye interactions with the humic colloid indicated that the dye – humic acid complex has a weaker absorption spectrum than the free dye. The absorption spectra suggested that the binding sites on the humic acid are sufficiently isolated to prevent dye–dye interactions on the colloid surface. The dye photosensitization of tryptophan degradation indicated that only the free methylene blue was active in the presence of humic acid, clay, and polystyrene sulphonic acid. The model suggests that if the pollutant must be in true solution to be biologically active then a size separation by dialysis would be a satisfactory speciation procedure.

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Predicting the Strength of Stacking Interactions Between Heterocycles and Aromatic Amino Acid Side Chains

10.26434/chemrxiv.7628939.v2 ◽

2019 ◽

Author(s):

Andrea N. Bootsma ◽

Analise C. Doney ◽

Steven Wheeler

Keyword(s):

Amino Acid ◽

Binding Sites ◽

Aromatic Amino Acid ◽

Aromatic Amino Acids ◽

Biologically Active ◽

Side Chains ◽

Stacking Interactions ◽

Inhibitor Binding ◽

Protein Binding Sites ◽

Amino Acid Side Chains

<p>Despite the ubiquity of stacking interactions between heterocycles and aromatic amino acids in biological systems, our ability to predict their strength, even qualitatively, is limited. Based on rigorous <i>ab initio</i> data, we have devised a simple predictive model of the strength of stacking interactions between heterocycles commonly found in biologically active molecules and the amino acid side chains Phe, Tyr, and Trp. This model provides rapid predictions of the stacking ability of a given heterocycle based on readily-computed heterocycle descriptors. We show that the values of these descriptors, and therefore the strength of stacking interactions with aromatic amino acid side chains, follow simple predictable trends and can be modulated by changing the number and distribution of heteroatoms within the heterocycle. This provides a simple conceptual model for understanding stacking interactions in protein binding sites and optimizing inhibitor binding in drug design.</p>

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Methylcellulose/tannic acid complex particles coated on alginate hydrogel scaffold via Pickering for removal of methylene blue from aqueous and quinoline from non-aqueous media

Chemosphere ◽

10.1016/j.chemosphere.2021.131597 ◽

2021 ◽

pp. 131597

Author(s):

Medhen W. Abebe ◽

Hern Kim

Keyword(s):

Methylene Blue ◽

Tannic Acid ◽

Aqueous Media ◽

Alginate Hydrogel ◽

Hydrogel Scaffold ◽

Acid Complex

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STUDIES ON ACTH-BINDING ANTIBODIES: CHARACTERIZATION OF IMMUNOLOGICAL SPECIFICITIES

Acta Endocrinologica ◽

10.1530/acta.0.0620521 ◽

1969 ◽

Vol 62 (3) ◽

pp. 521-536 ◽

Cited By ~ 7

Author(s):

M. L. Aubert ◽

J.-P. Felber

Keyword(s):

Binding Sites ◽

Competitive Inhibition ◽

Biologically Active ◽

Active Part ◽

Terminal Portion ◽

Plasma Acth ◽

Acth Fragments ◽

Selection Of

ABSTRACT In investigations on the production and the specificity of anti-ACTH antibodies used for radioimmunoassay, differences have been observed between the various antibodies obtained. It was shown by means of competitive inhibition with different ACTH fragments that the binding of the ACTH molecule to its antibody can occur at different sites along the ACTH peptide. By varying the concentrations of the fragments and the conditions of the assays, it was possible to study the properties of each antibody. Thus antibodies which bind the N-terminal portion, or which exclusively bind the biologically active part of the ACTH chain (1–20), are the most suitable for radioimmunoassay. It was found, however, that the production of antiserum was generally more frequent when binding occurred to the C-terminal portion of the ACTH peptide. Should the presence of such fragments in plasma be confirmed, then the use of these antisera could lead to erroneous measurement of biologically inactive ACTH fragments. Thus, this study reveals that a selection of the antibody for specificity might be necessary for its application to the radioimmunoassay of plasma ACTH, and that this selection could be performed with the use of ACTH fragments. An approach to the problem of binding sites between antigen and antibody has been described and the possibility of introducing a radioimmunoassay for plasma ACTH fragments discussed.

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Spectrophotometric study of the Sodium dodecyl sulfate in the presence of Methylene blue in the methanol-water mixed solvent system

Journal of Molecular Liquids ◽

10.1016/j.molliq.2021.117200 ◽

2021 ◽

pp. 117200

Author(s):

Pawan Shah ◽

Shikha Kumari Jha ◽

Ajaya Bhattarai

Keyword(s):

Methylene Blue ◽

Sodium Dodecyl Sulfate ◽

Mixed Solvent ◽

Sodium Dodecyl ◽

Spectrophotometric Study ◽

Solvent System ◽

Mixed Solvent System ◽

Dodecyl Sulfate

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Adsorption of the herbicide glyphosate on a metal-humic acid complex

The Science of The Total Environment ◽

10.1016/0048-9697(92)90134-e ◽

1992 ◽

Vol 123-124 ◽

pp. 77-82 ◽

Cited By ~ 36

Author(s):

A. Piccolo ◽

G. Celano ◽

G. Pietramellara

Keyword(s):

Humic Acid ◽

Acid Complex ◽

Herbicide Glyphosate

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Gamma-interferon modulates human monocyte/macrophage transferrin receptor expression

Blood ◽

10.1182/blood.v71.6.1590.bloodjournal7161590 ◽

1988 ◽

Vol 71 (6) ◽

pp. 1590-1595 ◽

Cited By ~ 1

Author(s):

R Taetle ◽

JM Honeysett

Keyword(s):

Binding Sites ◽

Blood Cells ◽

Interleukin 1 ◽

Human Monocyte ◽

Gamma Interferon ◽

Receptor Expression ◽

Biologically Active ◽

Gm Csf ◽

Fe Content ◽

Slot Blot Analysis

Although circulating human monocytes do not express transferrin (Tf) receptors, cultured adherent blood cells display high-affinity Tf binding sites. In the present studies, effects of various cytokines and biologically active proteins on human monocyte/macrophage Tf receptors were investigated. After culture, Tf receptor expression by adherent blood cells was time dependent and plateaued by 7 days. The addition of interleukin-1 (IL-1), alpha-interferon (alpha-IFN), granulocyte/macrophage-colony stimulating factor (GM-CSF), or human IgG to macrophages cultured for 4 days did not alter Tf receptor expression. Fe-saturated, human Tf caused a significant, dose-dependent decrease in receptor expression. At a dose of 100 U/mL, gamma- interferon (gamma-IFN) significantly increased Tf receptor expression by macrophages cultured for 4 (230% +/- 51% of control) or 7 days (150% +/- 22%). Scatchard analyses showed increased binding sites but no change in receptor affinity. Northern and slot blot analysis of cellular mRNA from macrophages cultured for 4 to 7 days and exposed to gamma-IFN showed a two- to fivefold increase in Tf receptor mRNA, but less than or equal to 30% increase in beta-actin mRNA. Ferritin content of gamma-IFN-treated macrophages was 47% to 63% of control cells. Net uptake of 59Fe from Tf by gamma-IFN-treated cells was 10% to 17% of control, but uptake of radiolabeled Tf was comparable. When macrophages were labeled with 59Fe and then exposed to gamma-IFN, cell-associated Fe was reduced by 43%, indicating that gamma-IFN caused macrophage Fe release. gamma-IFN specifically modulates Tf receptor display by inducing Fe release and reducing cellular Fe content. Regulation of Tf receptor expression in macrophages is controlled by cellular Fe content and is thus similar to regulatory mechanisms in dividing cells.

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