We described a dual turn-on probe sensitive to both acidity and basicity, which could be designed by connecting a fluorophore to a quencher via metal-ligand interaction. Atto488-labeled nitrilotriacetic acid and polyhistidine peptide were used as the fluorophore and the quencher, respectively, and linked to each other by coordination with a cobalt(II) ion. After preparation of the probe, the pH...

A possibility of non-conventional two-step protonation of 1,8-bis(dimethylamino)naphthalene (proton sponge) is discussed. Unlike the generally accepted mechanism, involving relatively slow direct penetration of a proton into the cleft between the peri-NMe2 groups, it consists of the rapid addition of a proton to the out-inverted NMe2 group with the subsequent slower rotational transfer of the p...

Basicity constants for a series of 3,7-diazabicyclo[3.3.1]nonane derivatives in acetonitrile with a variation over 13 orders of magnitude have been determined using a spectrophotometric titration technique. An excellent correlation between basicity and calculated proton affinities obtained at PCM-B3LYP/6-31+G(d)//B3LYP/6-31G(d) level was found. The results are discussed in terms of substituent ...

A calcium phosphate cement (CPC) was shown to have the necessary attributes for endodontic materials except adequate basicity needed for antimicrobial properties. To enhance its basicity, tricalcium silicate (Ca3SiO5), a highly alkaline compound, was added to CPC at a mass fraction of 0.25, 0.5 or 0.75. The basicity, acid neutralization and physical properties of the CPC-Ca3SiO5 composites were...

The effects of preparative parameters on the surface basicity, composition, and transesterification activities of several Ca-La metal oxide catalysts were investigated. Four different preparation methods: ammonia-ethanol-carbon dioxide precipitation, physical mixing, impregnation, and coprecipitation, were studied. It was found that the ammoniaethanol-carbon dioxide precipitation method resulte...

Rate constants for the reactions of substituted quinuclidines with pnitrophenyl phosphate, 2,4-dinitrophenyl phosphate, 2,4-dinitrophenyl phosphate complexed with calcium, and phosphorylated pyridine decrease with increasing pKa of the amine. Plots of log k against pK, give slopes of @ , , = -0.05, -0.10, -0.1 1, and 4.10, respectively, for these.compounds; &, = -0.01 for phosphorylated 4-morph...

The thermodynamic selectivity for Gd(3+) relative to Ca(2+), Zn(2+), and Fe(3+) of two ligands of potential interest as magnetic resonance imaging (MRI) contrast agents has been determined by NMR spectroscopy and potentiometric and spectrophotometric titration. The two hexadentate ligands TREN-6-Me-3,2-HOPO (H(3)L2) and TREN-bisHOPO-TAM-EA (H(4)L3) incorporate 2,3-dihydroxypyridonate and 2,3-di...

The hydr6lysis of a series of substituted anilides of Nacetyl-L-tyrosine by cY-chymotrypsin has been investigated. Values of the kinetic parameters have been obtained in water and deuterium oxide solvent systems. It has been shown that the isotope effect decreases as the basicity of the substrate is increased. pH dependence studies have shown that the rate of hydrolysis, kz, is independent of p...

Electrospray ionization mass spectrometry is a critically important technique for the determination of small molecules, but its application for this purpose is complicated by its selectivity. For positive ion ESI-MS analysis of basic analytes, several investigators have pointed to the importance of analyte basicity as a source of selectivity. Currently, however, it is not known whether basicity...

This paper examines two mold powder related process problems experienced at BHP's Whyalla operations. Bands of deep transverse depressions extending about the perimeter of the strand in the first meter of cast product were identified as a potential cause of breakouts. These were associated with level drops in the mold during startup that allow sintered material to accumulate against the mold wa...