MALDI TOF/TOF tandem mass spectrometry as a new tool for amino acid analysis

This is the first report of an application of collisionally induced fragmentation of amino acids (AA) and their derivatives by MALDI TOF/TOF tandem mass spectrometry (MS). In this work, we collected the data on high-energy fragmentation reactions of a large group of protonated amino acids and their derivatives with the goal of determining which product ions are analyte specific and if yields of these fragment could be used for quantitative analysis. From 34 different amino acids (20 alpha-amino acids, beta-amino acids, homocysteine, GABA, and modified AA Met sulfone and sulfoxide, hydroxyproline, etc.) we observed that high yields of the target specific immonium ions and fragmentation patterns are most similar to EI or FAB CID on sector instruments. The major exceptions were two highly basic amino acids, Arg and Orn. It is noted that neither beta-, gamma-, nor delta-amino acids produce immonium ions. As might be predicted from high-energy CID work on peptides from the sectors and TOF/TOF, the presence of specific indicator ions in MALDI tandem MS allows distinguishing isomeric and isobaric amino acids. These indicator ions, in combination with careful control of data acquisition, ensure quantitative analysis of amino acids. We believe our data provide strong basis for the application of MALDI TOF/TOF MS/MS in qualitative and quantitative analysis of amino and organic acids, including application in clinical medicine.     

New approach to the synthesis of substituted 7H‐furo[3,2‐b]pyran‐7‐ones based on 5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one derivatives

A convenient approach to the synthesis of the previously unknown 7H‐furo[3,2‐b]pyran‐7‐ones based on the intramolecular cyclization of carbonyl derivatives of 5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one has been elaborated. Key intermediates in the synthesis of the target 7H‐furo[3,2‐b]pyran‐7‐ones are 3‐hydroxy‐6‐methyl‐2‐(2‐oxo‐2‐arylethyl)‐4H‐pyran‐4‐ones. They are formed as a result of multicomponent condensation of 5‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one with arylglyoxals and 4‐methoxyaniline.     

Stereoselective electrocatalytic transformation of arylidene- or alkylidenemalononitriles and malonate into alkyl (1R,5R,6R)* 6-substituted 5-cyano-4,4-dialkoxy-2-oxo-3-azabicyclo[3.1.0]hexane-1-carboxylates

Electrolysis of arylidene- or alkylidenemalononitriles and malonate in alcohol in an undivided cell in the presence of sodium halide as mediator results in the stereoselective formation of alkyl (1R,5R,6R)* 6-substituted 5-cyano-4,4-dialkoxy-2-oxo-3-azabicyclo[3.1.0]hexan-1-carboxylates in 50-70% yields.     

Non-linear inplane vibrations of wrinkling films

This paper presents analytical investigations of non-linear effects caused by wrinkling of films in the course of contraction and shearing. As shown, such non-linearities are important even for very small amplitudes of vibrations. Approximate analytical solutions for inplane vibrations are derived.     

Dynamics of film

The general theory of films as two-dimensional continua are elaborated upon. As physical realizations of such a model this paper examines: inextensible films, elastic films, and nets.The suggested dynamic equations have enabled us to find out the characteristic speeds of wave propagation of the invariants of external and internal geometry and formulate the criteria of instability of their shape. Also included herein is a detailed account of the equation describing the film motions beyond the limits of the shape stability accompanied by the formation of wrinkles.The theory is illustrated by examples.The effort was supported by Dr. A. Amos, Materials and Structures Division, Office of Aeronautics and Space Technology, National Aeronautics and Space Administration.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS7-100 sponsored by the National Aeronautics and Space Administration.     

Pyrrolidine-thioxotetrahydropyrimidinone as an efficient organocatalyst for the enantioselective Michael addition of cyclic ketones to nitrodienes

Among the various Michael additions, the enantioselective reaction between cyclic ketones and nitrodienes has received little attention in comparison to the corresponding reaction with nitroolefins. A bifunctional organocatalyst consisting of the pyrrolidine moiety and a thioxotetrahydropyrimidinone ring successfully catalyzed this asymmetric transformation. The products of the reaction between various ketones and nitrodienes were obtained in high yields (up to 96%) with excellent diastereo- (up to >98:2 dr) and enantioselectivities (up to 99:1% er).     

Photolysis of 3-(1-acyl-5-aryl-3-pyrazolinyl)coumarins—Effective Fluorescence Decay

Photophysical characteristics of new 3-(1-acyl-5-aryl-3-pyrazolinyl)coumarins have been measured. These coumarin derivatives are found to be effective fluorophores and show high values of quantum yields of fluorescence both in nonpolar and in polar solvents. The 3-(1-acyl-5-aryl-3-pyrazolinyl)coumarins turned to be photosensitive compounds and undergo photolysis under irradiation in the range of 310–465 nm. Photolysis is suggested to include retro-cyclization and retro-condensation steps. The process is accompanied by a sharp drop of fluorescence that can be of interest for the creation of new media in optical recording of information.