Testing isotopic labeling with [13C6]glucose as a method of advanced glycation sites identification

Non‐enzymatic glycation and glycoxidation protein products in foods and diseases: An interconnected, complex scenario fully open to innovative proteomic studies

“…These species present a Δ m = +144 (FL − H 2 O) or +126 (FL − 2 H 2 O) Da with respect to the unmodified peptide, and were associated with the structures reported in Figure . Isotopic labeling experiments with 12 C 6 / 13 C 6 glucose confirmed their occurrence, having an isotopic pattern consistent with dehydrated Amadori product structures (Kielmas et al, ). Similar results were also obtained on non‐labeled glycated proteins subjected to proteolytic digestion in H 2 18 O (Barnaby et al, ).…”

“…In most cases, formation of these compounds was attributed unambiguously (based on the sequence) to the modification of specific lysines; in other cases, the concomitant absence of Lys and occurrence of Arg residues in the analyzed peptide confirmed that they may be tentatively ascribed to arginine‐derived imidazolone or tetrahydropyrimidine species, both having a Δ m = +144 with respect to the unmodified peptide. The definitive assignment of the adducts with Δ m = +144 and +126 Da to specific Lys residues was achieved by nLC‐ESI‐MS/MS experiments performed on proteins glycated in vitro (Lapolla et al, ; Yeboah et al, ; Dai et al, ; Kielmas et al, ). Poor sequence informative MS/MS spectra under CID conditions were also obtained in this case.…”

“…Also for AGEs, in vitro labeling experiments with isotope‐containing reagents facilitated protein modification site assignment by simple peptide mapping experiments (Kielmas et al, ). When an isolated protein, labeled with a 1:1 mixture of a 12 C 6 / 13 C 6 reducing sugar, was digested with trypsin and the corresponding digest was analyzed by LC/high‐resolution MS, AGE‐containing peptides were easily identified on the basis of their specific isotopic patterns that, depending on their charge status, gave unique mass signatures of two molecular ions with equal intensity.…”

B12‐TiO2 Hybrid Catalyst for Light‐Driven Hydrogen Production and Hydrogenation of CC Multiple Bonds

“…Many studies on boronic acids (BA) have focused on their ability to interact specifically with cis ‐diol‐containing biomolecules through the formation of a reversible pair of covalent ester bonds [1–3]. This rather unique feature has been widely explored during the last 30 years in the development of carbohydrate sensors [4, 5], extraction of cis ‐diol‐containing molecules [6], labeling of proteins, and cell surfaces [7, 8] and in the affinity chromatographic separation of biomolecules such as glycoproteins, glycopeptides, nucleosides, and nucleic acids [9–14].…”

Selective Detection of Carbohydrates and Their Peptide Conjugates by ESI-MS Using Synthetic Quaternary Ammonium Salt Derivatives of Phenylboronic Acids

“…Another approach to the analysis of the primary structure of these compounds was based on a combination of enzymatic hydrolysis with mass spectrometry [8, 9]. Because of a very low concentration of modified proteins and peptides, new methods of selective detection based on isotopic labeling ( 13 C or 18 O) combined with mass spectrometry were researched [10, 11]. Another approach to overcome the low concentration of analyzed compounds is the application of sample preconcentration, frequently based on affinity methods.…”