title: Isotope labeling studies on the formation of multiple addition products of alanine in the pyrolysis residue of glucose/alanine mixtures by high-resolution ESI-TOF-MS.
abstract: Pyrolysis was used as a microscale sample preparation tool to generate glucose/alanine reaction products to minimize the use of expensive labeled precursors in isotope labeling studies. The residue remaining after the pyrolysis at 250 °C was analyzed by electrospray time-of-flight mass spectrometry (ESI-TOF-MS). It was observed that a peak at m/z 199.1445 in the ESI-TOF-MS spectrum appeared only when the model system contained at least 2-fold excess alanine. The accurate mass determination indeed indicated the presence of two nitrogen atoms in the molecular formula (C(10)H(18)N(2)O(2)). To verify the origin of the carbon atoms in this unknown compound, model studies with [(13)U(6)]glucose, [(13)C-1]alanine, [(13)C-2]alanine, [(13)C-3]alanine, and [(15)N]alanine were also performed. Glucose furnished six carbon atoms, and alanine provides four carbon (2 × C-2 and 2 × C-3) and two nitrogen atoms. When commercially available fructosylalanine (N-attached to C-1) was reacted with only 1 mol of alanine, a peak at m/z 199.1445 was once again observed. In addition, when 3-deoxyglucosone (3-DG) was reacted with a 2-fold excess of alanine, a peak at m/z 199.1433 was also generated, confirming the points of attachment of the two amino acids at C-1 and C-2 atoms of 3-DG. These studies have indicated that amino acids can undergo multiple addition reactions with 1,2-dicarbonyl compounds such as 3-deoxyglucosone and eventually form a tetrahydropyrazine moiety.
authors: Department of Chemistry, Université du Québec à Montréal, Montréal, Québec, Canada.
authors: Fong Lam
authors: FL
authors: Chu
authors: Lekha
authors: L
authors: Sleno
authors: Varoujan A
authors: VA
authors: Yaylayan
mesh_terms: D000409:Alanine / Q000737:chemistry*; D002247:Carbon Isotopes / Q000737:chemistry; D005947:Glucose / Q000737:chemistry*; D007553:Isotope Labeling; D015394:Molecular Structure; D009587:Nitrogen Isotopes / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D005947:Glucose; D000409:Alanine