Evaluation of 4,6-Diamidino-2-phenylindole as a Fluorescent Probe Substrate for Rapid Assays of the Functionality of Human Multidrug and Toxin Extrusion Proteins

ABSTRACT: Multidrug and toxin extrusion protein 1 (MATE1) and MATE2-K are organic cation/H ؉ antiporters that have recently been identified and suggested to be responsible for the brush border secretory transport of many cationic drugs in renal tubules. We here report our finding that 4,6-diamidino-2-phenylindole (DAPI) can be used as a probe substrate for rapid assays of the functionality of the human MATEs, hMATE1, and hMATE2-K, by taking advantage of its fluorescent nature. The specific cellular uptakes of DAPI by cloned hMATE1 and hMATE2-K, which were assessed by fluorescence intensity, were found to be rapid and saturable with the Michaelis constants of 1.13 and 3.16 M, respectively, indicating that DAPI is a good substrate of both hMATEs. It was found that many organic cations inhibit the specific uptake of DAPI by hMATE1 and hMATE2-K, and the extents of inhibition are in good correlation with those of inhibition of the specific uptake of [ 3 H]cimetidine as a typical substrate, indicating comparable performances of both substrates as probes in identifying inhibitors. Thus, DAPI can be an alternative probe substrate that enables fluorometric rapid assays of the functionality of both hMATEs. It was also found that the other major renal organic cation transporters, human organic cation transporter 2 (hOCT2), hOCT3, human novel organic cation transporter 1 (hOCTN1), and hOCTN2, cannot transport DAPI, although hOCT1, which is mainly expressed in the liver, can. Therefore, the DAPI uptake assay can be a method specific to the hMATEs among organic cation transporters in the human kidney

Welwitindolinone C synthetic studies. Construction of the welwitindolinone carbon skeleton via a transannular nitrone cycloaddition

Described is the construction of the N-methylwelwitindolinone C core via an efficient strategy that employs a sequential rhodium carbenoid-mediated O–H insertion, Claisen rearrangement and transannular [3+2] nitrone cycloaddition

Crystal structure of 2-bromo-1,4-dihydroxy-9,10-anthraquinone

In an attempt to brominate 1,4-dipropoxy-9,10-anthraquinone, a mixture of products, including the title compound, C14H7BrO4, was obtained. The molecule is essentially planar (r.m.s. deviation = 0.029 Å) and two intramolecular O—H...O hydrogen bonds occur. In the crystal, the molecules are linked by weak C—H...O hydrogen bonds, Br...O contacts [3.240 (5) Å], and π–π stacking interactions [shortest centroid–centroid separation = 3.562 (4) Å], generating a three-dimensional network

4-(3-Bromopropyloxy)-1-hydroxy-9,10-anthraquinone

In the molecule of the title compound, C17H13BrO4, the anthraquinone ring system is slightly bent, with a dihedral angle of 169.99 (7)° between the planes of the two benzene rings. The side chain (O—C—C—C—Br) has a gauche–gauche conformation, as indicated by the O—C—C—C and C—C—C—Br torsion angles of −66.9 (2) and −65.8 (2)°, respectively. In addition, there is an intramolecular O—H...O hydrogen bond enclosing an S(6) ring motif. The hydrogen-bond donor is bifurcated; in the crystal, a pair of O—H...O hydrogen bonds connects two molecules, forming an inversion dimer with an R22(12) ring motif