2-Methyl-(1Z,3E)-butadiene-1,3,4-tricarboxylic acid, "isoprenetricarboxylic acid".

[reaction: see text] The synthesis of the title compound 7 from ethyl glyoxylate and dimethyl and diethyl beta-methylglutaconate is described along with its physical properties that suggest its inability to assume a cis-dienoid structure due to steric hindrance between the methyl and carboxyl groups.

Detection and characterization of the product of hydroethidine and intracellular superoxide by HPLC and limitations of fluorescence.

Here we report the structural characterization of the product formed from the reaction between hydroethidine (HE) and superoxide (O(2)(.-)). By using mass spectral and NMR techniques, the chemical structure of this product was determined as 2-hydroxyethidium (2-OH-E(+)).

Divinyl sulfone as a postdigestion modifier for enhancing the a(1) Ion in MS/MS and postsource decay: potential applications in proteomics.

Divinyl sulfone reacts at pH 8-9 with the alpha-amino groups of N-terminal residues, proline, the epsilon-amino groups of lysine, and the histidine side chains of peptides. This reaction leads to great enhancement of the abundance of the normally weak or missing "a(1)" fragment ion in MS/MS analysis defining the N-terminal residue of a peptide in a digest. This provides "one-step Edman-like" information that, together with a fairly accurately determined mass, often enables one to correctly identify a protein or family of proteins.

Californium-252 Plasma Desorption Mass Spectrometry as an Aid in the Synthesis of a Series of Adenosine and Xanthine Conjugates.

Two series of biologically active purine derivatives have been analyzed using californium-252 plasma desorption mass spectrometry. The series of compounds are adenosine agonists ( -phenyladenosine derivatives) and antagonists (8-phenyl-1,3-dipropylxanthine derivatives) at extracellular purine receptors. Included are receptor probes synthesized through successive chain elongation reactions.