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At least 379 records · Page 21Linked to original sources
PubMed1995

Use of the derivatizing agent 4-aminobenzoic acid 2-(diethylamino)ethyl ester for high-sensitivity detection of oligosaccharides by electrospray ionization mass spectrometry.

A method for the high-sensitivity detection of oligosaccharides by electrospray ionization mass spectrometry (ESI-MS) is reported. The method involves the chemical derivatization with 4-aminobenzoic acid 2-(diethylamino)-ethyl ester (ABDEAE). This derivative, which contains a 2-(diethylamino)ethyl group, having a high proton affinity, enhances the ionization efficiency of analytes in the positive ESI mode. Experiments using maltohexaose as a model oligosaccharide revealed that derivatization with ABDEAE gave a remarkably large increase in molecular ion abundance. Using a mixture of acetonitrile, 2-methoxyethanol, 2-propanol, and water (1:1:1:1 v/v/v/v) as solvent for ESI, ABDEAE-derivatized maltohexaose could be detected at a level of 10 fmol. This represents a 5000-fold improvement in sensitivity over underivatized maltohexaose. ESI tandem mass spectrometry of the ABDEAE-derivatized maltohexaose provides structural information at the low-picomole level. In this spectrum, 1,5X' and 0,2A" series of sequence ions, arising from ring cleavage, were observed as the predominant ions.

Anions↗
PubMed2003

Synthesis of 6-mono-6-deoxy-beta-cyclodextrins substituted with isomeric aminobenzoic acids. Structural characterization, conformational preferences, and self-inclusion as studied by NMR spectroscopy in aqueous solution and by X-ray crystallography in the solid state.

The synthesis, purification, and characterization of mono-6-modified-beta-cyclodextrins bearing N-attached o-, m-, and p-aminobenzoic acids (2, 3, and 4, respectively) are presented. The structures in aqueous solution were investigated using one- and two-dimensional NMR spectroscopy. Detailed assignment of the spectra together with intramolecular NOE correlations revealed the way each of the isomeric appendages is positioned relative to the macrocyclic cavity. No self-inclusion is observed. The o-isomer 2 turns inward over the top of the primary side and interacts with specific protons of the substituted glucopyranose unit A and those of a neighboring unit. The m-isomer 3 displays two conformations, where the substituent resides above the primary side in a tilted manner and interacts either with the previous or the next unit. We propose that the carboxyl groups in both 2 and 3 are localized through H-bonding with one or two, respectively, primary hydroxyl groups of the neighboring glucopyranose units. In a similar positioning of the aromatic ring of the p-isomer 4, the hydrophilic carboxyl end is fully exposed to the aqueous environment. The X-ray structure of 4 shows that the solution conformation has evolved such that in the crystalline state, the aromatic moiety is inserted through its carboxyl part inside another CD where it establishes intermolecular H-bonds with inward-turned primary OH groups. Besides this stabilization, 4 forms parallel and antiparallel supramolecular chains in the crystal that are additionally stabilized by direct H-bonds.

Aminobenzoates↗
PubMed1980

Light scattering studies of the solubilization of some esters of p-aminobenzoic acid by lysophosphatidylcholine.

Light scattering equipment has been constructed using a vertically polarized helium-neon laser and a phase-sensitive detection system. The apparatus has been used to determine the micellar weight of lysophosphatidylcholine (LPC), giving values of 1.33 x 105 in water and 1.47 x 105 in 0.05 M sodium chloride; the sols showed some degree of polydispersity. The light scattering apparatus has also been used to study the solubilization by LPC of three n-alkyl esters of paraminobenzoic acid. These compounds caused a considerable increase in the scattered light, particularly at higher LPC concentrations.

4-Aminobenzoic Acid↗