Sequencing hydroxyethylamine-containing peptides via Edman degradation

Hydroxyethylamine-containing peptides can be sequenced by automated Edman degradation to provide sequence information for peptide segments on either side of the peptide backbone modification. [reaction: see text]     

Monitoring apple flavor by use of quartz microbalances

"Electronic noses", i.e. arrays of differently coated quartz microbalances (QMB), have been used for selective detection of, and discrimination between, volatile organic compounds (VOC) formed during the post-harvest ripening of apples. The flavor components to be differentiated are chemically rather similar carbonyl compounds, chiefly aldehydes and esters. Because their relative ratios change during the post-harvest ripening period, appropriately selected sensor-active layers lead to characteristic patterns of the sensor responses which can be analyzed via pattern-recognition methods. This enables qualitative and quantitative identification of individual components whereby the post-harvest ripening of apples and other fruits can be monitored. Different kinds of apple differ in type and concentration of individual carbonyl compounds.     

Analysis of commercial vegetable tanning agents by reversed-phase liquid chromatography-electrospray ionization-tandem mass spectrometry and its application to wastewater

Commercial vegetable tanning agents that are derived from plants and consist of condensed or hydrolyzable tannins were analyzed by electrospray ionization–tandem mass spectrometry (ESI–MS/MS) to identify their major constituents and to study their collision-induced dissociation. In the condensed tannin wattle a series of proanthocyanidin dimers to tetramers was identified together with the flavonoid monomers catechin and gallocatechin. The composition of the hydrolyzable tannin chestnut was more heterogenous. Besides the monomers ellagic and gallic acid a variety of gallotannins were detected, namely mono-, di- and trigalloylglucose, and a variety of ellagitannins. Reversed-phase HPLC–ESI–MS/MS methods were developed to detect condensed and hydrolyzable tannins in tannery wastewaters by multiple reaction monitoring (MRM). The methods proved suitable even for highly loaded wastewaters. However, the detected amount of wattle tanning agent in spent retanning baths was about two orders of magnitude below the amount used for the retanning. This suggests that the condensed tannins of polyphenolic structure are rapidly transformed during the tanning process to yet unknown products.     

Arginine-based molecular transporters: the synthesis and chemical evaluation of releasable taxol-transporter conjugates

[structure: see text] A flexible and efficient procedure has been developed for the conjugation of taxol to various arginine-based molecular transporters via the taxol C2' O-chloroacetyl derivative. The resultant taxol-transporter conjugates are highly water soluble and release free taxol with half-lives of minutes to hours depending on the pH and the linker structure.     

Catalytic CO oxidation by free Au2-: experiment and theory

Temperature-dependent rf-ion trap mass spectrometry and first-principles simulations reveal the detailed reaction mechanism of the catalytic gas-phase oxidation of CO by free Au(2)(-) ions in the presence of O(2). A metastable intermediate with a mass of Au(2)CO(3)(-) was observed at low temperatures. Two alternative structures corresponding to digold carbonate or peroxyformate are predicted for this intermediate. Both structures are characterized by low activation barriers for the formation of CO(2). These combined experimental and theoretical investigations provide a comprehensive understanding of the kinetics, energetics, and atomic arrangements along the reaction path, thus allowing a formulation of the catalytic cycle for the oxidation reaction.