Two polar metabolites of mitoxantrone, a clinically active antitumor agent, have been isolated and purified from the urine of patients by sequential absorption on glass wool and Cu-Sep-Pak cartridges followed by preparative high-performance liquid chromatography. Negative ion chemical ionization mass spectrometry indicated that the two metabolites are the diand mono-carboxylic acids resulting f...

1-O-Allyloxycarbonyl (or ethyloxycarbonyl)-2-azido-2-deoxy-3-O-benzyl (or allyl, or benzoyl)-4,6-O-isopropylidene-beta-d-mannopyranose derivatives were prepared from the corresponding 2-hydroxy-beta-d-glucopyranosyl carbonates in high yields via triflation of the 2-hydroxyl group and subsequent SN2 displacement with azide ion. An N-acetyl-mannosamine-containing trisaccharide, a fragment of the ...

Remote sensing discoveries of hydroxyl and water on the lunar surface have reshaped our view of the distribution of water and related compounds on airless bodies such as the Moon1–3. The origin of this surface water is unclear4, but it has been suggested that hydroxyl in the lunar regolith can result from the implantation of hydrogen ions by the solar wind1,5. Here we present Fourier transform ...

By DFT calculation, we found that acid-catalyzed carboxylic acid esterification and ester hydrolysis are brief two-step reactions. First, the carboxylic acid hydroxyl-oxygen or ester alkyl-oxygen is protonated, which generates a highly active acylium ion. The protonation requires an activation energy (Ea) of 4-10 kcal mol(-1), and is the rate-controlling step of the esterification or hydrolysis...

The solvation of Al3+ and its hydrolyzed species in water clusters has been studied by means of ab initio molecular dynamics simulations. The hexa-hydrate Al(H2O) 3+ 6 ion formed a stable complex in the finite temperature cluster simulation of one aluminum ion and 16 waters. The average dipole moment of strongly polarized hydrated water molecules in the first solvation shell of Al(H2O) 3+ 6 was...

The location and orientation of the carbonate ion in the channel (A) and phosphate (B) positions of hydroxyapatite (CHAP) have been investigated by single-crystal X-ray structure and Fourier transform infrared (FTIR) spectroscopy, using crystals synthesized at high pressure. The type A carbonate ion is oriented in the apatite channel with two oxygen atoms close to the c-axis and the B carbonate...

For many years distinction has been made between acid denaturation, alkali denaturation, and the heat denaturation of proteins. In a recent review (24) heat is classified as a “physical” denaturing agent and hydrogen and hydroxyl ions as “chemical” denaturing agents. Nevertheless, it is clear that the intensity factors associated with acidity and alkalinity (the pH) and with heat (the temperatu...

A structure-based approach to the mechanism of ion pumping in bacteriorhodopsin (BR) has fostered new hypotheses for the detailed molecular changes that underlie ion transport in this light-driven pump. Isomerization of the retinal from all-trans to 13-cis in response to absorption of the energy of a photon is thought to lead to proton transfer from the initially protonated Schiff base to an an...