서강대학교

초록

In Chapter 1, an inproved free radical-initiated peptide backbone dissociation using newly designed TEMPO-mediated FRIPS reagent, 4-(2,2,6,6,-Tetramethylpiperidin-1-oxyl) methyl benzyl succinic acid N-hydroxysuccinimide (also known as p-TEMPO–Bn–Sc–NHS) is introduced. This reagent exhibits improved conjugation efficiency with targeted peptides as compared with previous cross linker, o-TEMPO–Bz-radical initiator. p-TEMPO–Bn–Sc–NHS achieves the FRIPS with higher energy collision induced dissociation (CID), which eventually enables the single-step MS3 to derive the peptide backbone fragmentation. pTEMPO–Bn–Sc–NHS was conjugated with model peptides and these conjugates were analyzed by MS/MS and MS3 to verify the single-step FRIPS in positive ionmode. Collisional activation enabled the homolytic cleavage of C-O bond between benzylic carbon and adjacent TEMPO oxygen in p-TEMPO–Bn–Sc–C(O)–peptides, leading to exclusive generation of •Bz–Sc–peptide radical. Successive radical migration and beta hydrogen (Hß) cleavage of peptide backbone produced fragment ions consisting mainly of a-/x-, c-/z-type ions and neutral loss ions produced by side chain loss. The energetic interpretation of p-TEMPO–Bn–Sc–C(O)-peptides was presented in the form of survival fraction to investigate the energetic dissociation of p-TEMPO conjugates. Also, p-TEMPO–Bn–Sc–NHS was applied to the phosphopeptides enriched from two different phosphoproteins, chicken egg albumin and alpha-casein, and the peptide backbone fragmentation patterns were compared with those obtained by the collisional activated dissociation and electron transfer dissociation. In Chapter 2, the development of mass spectrometry-based measurement for the critical micelle concentration of selected cationic and anionic surfactants is introduced. In this study, we found abnormal behaviors in the calibration curve of the selected cationic and anionic surfactants, such as sodium decyl sulfate (SDeS), sodium dodecyl sulfate (SDS), myristyltrimethylammonium bromide (MTAB), and benzyldimethyloctadecylammonium chloride (BAC‐18). As the concentration of the respective surfactant reaches their CMC, the linearity of the calibration curve suddenly changed or the calibration curve became flattened. Further direct-infusion ESI-MS analysis of the selected surfactants prepared at concentration above their CMC showed the formation of multimeric ions, which could be the evidence of the micelle formation. Also, the elution profile of the multimeric ions in chromatogrphic separation indicates the formation of ions with micellar characteristics. These abnormal behaviors in the calibration curve and the chromatographic seapration of the surfactants may be due to the formation of the micelle and the instability of the micellar ions. From a practical perspective, abnormal behaviors in the calibration curve suggest that concentrations close to the CMC should be avoided in the quantitative analysis of the surfactants to obtain accurate measurements.