Trends in the Hydrogen−Deuterium Exchange at the Carbon Centers. Preparation of Internal Standards for Quantitative Analysis by LC-MS

Abstract

The application of internal standards in quantitative and qualitative bioanalysis is a commonly used procedure. They are usually isotopically labeled analogs of the analyte, used in quantitative LC-MS analysis. Usually, 2H, 13C, 15N and 18O isotopes are used. The synthesis of deuterated isotopologues is relatively inexpensive, however, due to the isotopic effect of deuterium and the lack of isotopologue co-elution, usually they are not considered as good internal standards for LC-MS quantification. On the other hand, the preparation of 13C, 15N and 18O containing standards of drugs and their metabolites requires a complicated multistep de novo synthesis, starting from the isotopically labeled substrates, which are usually expensive. Therefore, there is a strong need for the development of low-cost methods for isotope-labeled standard preparations for quantitative analysis by LC-MS. The presented review concentrates on the preparation of deuterium-labeled standards by hydrogen−deuterium exchange reactions at the carbon centers. Recent advances in the development of the methods of isotopologues preparation and their application in quantitative analysis by LC-MS are evaluated.

Peptidyl-Resin Substrates as a Tool in the Analysis of Caspase Activity

“…The introduced deuterons do not undergo back exchange under acidic and neutral conditions, and the isotopologues present co-elution. This allowed us to prepare isotopically labeled standards of different compounds for their quantitative analysis by LC-MS [33][34][35]. Therefore, the presented tool for analysis of caspase activity and specificity may also be used in a quantitative way after preparation of appropriate deuterated QA-modified peptide sequences.…”

Site-selective deuteration of amino acids through dual protein catalysis

“…A few general approaches have been developed to access Cα and Cβ deuterated α-amino acids including de novo synthesis from deuterated building blocks or by preactivation of the amine, followed by hydrogen/deuterium (H/D) exchange under basic conditions. [9][10][11] Small molecule-based methods that avoid pre-functionalization of amino acids are rare and typically involve catalytic hydrogenation (Pd/C or Pt/C) in D2O. 12,13 This approach has been generally limited to the synthesis of Phe or Tyr isotopologs.…”

“…31 A second deprotonation was proposed to occur at Cβ to form an achiral enamine intermediate (10, Figure 1D). 31 Subsequent reprotonation of Cβ on the opposite face would lead to the observed epimerization and facially selective reprotonation at Cα would deliver L-allo-Ile (11) as the product. 31 Although a mechanism for the L-Ile (Ile) epimerization reaction was previously proposed, little is known about the role of each protein in this transformation.…”

Preparation of Deuterium-Labeled Armodafinil by Hydrogen–Deuterium Exchange and Its Application in Quantitative Analysis by LC-MS

“…Recently, we reported our investigation on the hydrogen–deuterium exchange of carbon-bounded hydrogen atoms in peptides containing N -substituted glycine and alanine residues, via base-catalyzed hydrogen–deuterium exchange [ 22 , 23 , 24 , 25 ]. This observation allowed us to developed methods of deuterated standards preparation of denatonium benzoate [ 26 ], cyclosporine A [ 27 ] and creatinine [ 28 ], which were successfully applied in their quantification by LC-MS. We found that the introduced deuterons do not undergo back-exchange either in an acidic or neutral conditions and that the isotopologues co-elute.…”