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The selectivity and functional variability of porphyrin cofactors are typically based on substrate binding of metalloporphyrins wherein the pyrrole nitrogen units only serve to chelate the metal ions. Yet, using the free base porphyrin inner core system for other functions is possible through conformational engineering. As a first step towards porphyrin 'enzyme-like' active centers, a structural and spectroscopic study of substrate binding to the inner core porphyrin system shows that a highly saddle distorted porphyrin with peripheral amino receptor groups [2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetrakis(2-aminophenyl)porphyrin] coordinates analytes in a switchable manner dependent on the acidity of the solution. The supramolecular ensemble exhibits exceptionally high affinity to the pyrophosphate anion (2.26 ± 0.021)⋅109 M-1 and does so in preference to other anions. 1H NMR spectroscopic studies provided insight into the likely mode of binding action and the characterization of atropisomers, all four of which were also studied by X-ray crystallography.
This article was published in the following journal.
Name: Angewandte Chemie (International ed. in English)
B lymphocytes use B cell receptors (BCRs) to recognize antigens. It is still not clear how BCR transduces antigen-specific physical signals upon binding across cell membrane for the conversion to chem...
Receptors alternate between resting↔active conformations that bind agonists with low↔high affinity. Here, we define a new agonist attribute, energy efficiency (η), as the fraction of ligand-bindi...
Meso-substituted calixpyrroles 2-6 containing direct meso-ethynyl linker displayed high binding affinities and unique conformational features on halide anion binding. A general conformational bias ...
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The prodrug, 5-Aminolevulinic acid (ALA), has been shown to lead to intracellular accumulation of fluorescent porphyrins in high grade malignant gliomas in the brain. On imaging, this accu...
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Receptors for ACTIVINS are membrane protein kinases belonging to the family of PROTEIN-SERINE-THREONINE KINASES, thus also named activin receptor-like kinases (ALK's). Activin receptors also bind TRANSFORMING GROWTH FACTOR BETA. As those transmembrane receptors of the TGF-beta superfamily (RECEPTORS, TRANSFORMING GROWTH FACTOR BETA), ALK's consist of two different but related protein kinases, Type I and Type II. Activins initiate cellular signal transduction by first binding to the type II receptors (ACTIVIN RECEPTORS, TYPE II ) which then recruit and phosphorylate the type I receptors (ACTIVIN RECEPTORS, TYPE I ) with subsequent activation of the type I kinase activity.
Stucturally-related receptors that are typically found on NATURAL KILLER CELLS. They are considered lectin-like proteins in that they share sequence homology with the carbohydrate binding domains of C-TYPE LECTINS. They differ from classical C-type lectins, however, in that they appear to lack CALCIUM-binding domains.
A site on an enzyme which upon binding of a modulator, causes the enzyme to undergo a conformational change that may alter its catalytic or binding properties.
Methods and techniques used to modify or select cells and develop conditions for growing cells for biosynthetic production of molecules (METABOLIC ENGINEERING), for generation of tissue structures and organs in vitro (TISSUE ENGINEERING), or for other BIOENGINEERING research objectives.
Porphyrins which are combined with a metal ion. The metal is bound equally to all four nitrogen atoms of the pyrrole rings. They possess characteristic absorption spectra which can be utilized for identification or quantitative estimation of porphyrins and porphyrin-bound compounds.
Enzymes are proteins that catalyze (i.e., increase the rates of) chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical re...
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