ovalbumin and triethylamine

A novel vinyl monomer, 3-dimethylamino-6-(p-methacrylamidophenylazo)phenylboronic acid (AzoPBA), which had been prepared by the coupling of p-aminophenyl methacrylamide hydrochloride with m-dimethylaminophenylboronic acid in the presence of sodium nitrite, was polymerized with 3-dimethylaminopropylacrylamide (DMAPAA). The copolymer obtained (Poly(DMAPAA/AzoPBA)) bound to sugars such as fructose and glucose in a weakly alkaline region (8 < pH), which was indicated by the absorbance change of the diphenylazo group at 557 nm. In contrast with this, a copolymer of N,N-dimethylacrylamide (DMAA) and the AzoPBA (Poly(DMAA/AzoPBA)) bound to sugars in a more alkaline region (9 < pH). The larger sensitivity of the former copolymer to the sugars than the latter in a weakly alkaline region is due to the supporting effect of tertiary amino group in the DMAPAA residue to the binding of sugar to the phenylboronic acid moiety. The association constant (K) of boronic acid residue in these copolymers with fructose was larger than that with glucose. These results indicated the usefulness of the DMAPAA/AzoPBA copolymer for the sensing of sugars in the weakly alkaline region near the physiological pH.

Topics: Absorption; Azo Compounds; Boronic Acids; Carbohydrate Metabolism; Ethylamines; Fluorescence; Hydrogen-Ion Concentration; Kinetics; Ovalbumin; Polymers; Solutions; Spectrophotometry, Ultraviolet

Post source decay (PSD) analysis of precursor ions generated from matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is a powerful tool for amino acid sequencing and primary structure analysis of proteins. N-Terminal sulfonation has become an effective derivatization strategy in facilitating de novo peptide sequencing by the formation of predominate y-type ion series in MALDI PSD spectra. Recently, an effective and inexpensive N-terminal derivatization method has been reported using 4-sulfophenyl isothiocyanate (SPITC) as the derivatization reagent (J. Mass. Spectrom. 2003; 38: 373-377). In this paper, we report an improvement in the derivatization procedure with this reagent that involves replacing an organic co-reagent with other chemicals and eliminating the use of organic solvent. The method is demonstrated on a model peptide and on tryptic digests of two proteins. The results indicate that the improved sulfonation reaction can be implemented with high efficiency under aqueous conditions and that the sensitivity of mass detection can be increased considerably.

Topics: Acetates; Amino Acid Sequence; Ethylamines; Indicators and Reagents; Isothiocyanates; Molecular Sequence Data; Oligopeptides; Ovalbumin; Peptides; Protein Conformation; Quality Control; Reproducibility of Results; Salts; Sensitivity and Specificity; Sequence Analysis, Protein; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Sulfones