Analytical Instrument Documents

MSTips No. 521

Introduction

Dipeptides have attracted increasing attention in recent years for their contributions to human health. Previous studies have reported that Tyr–Pro improves memory function, and that low‑molecular‑weight peptides, including Val–Tyr, exhibit antihypertensive effects [1, 2]. However, with conventional MALDI‑TOFMS, it is difficult to analyze the low‑molecular‑weight region below m/z 500, where dipeptides are typically detected. This difficulty arises from the following reasons: (1) low mass resolution caused by the short flight path length, which makes the spectra susceptible to interference from matrix‑derived ions, and (2) the presence of a large number of PSD (post‑source decay)‑derived ions observed as background signals. In contrast, the JMS‑S3000 NewSpiralTOF™ (Fig. 1) employs JEOL’s proprietary SpiralTOF ion‑optical system, which provides a long flight path of 17 m and enables the removal of PSD ions using an electric field sector. As a result, high mass resolution and high mass accuracy can be maintained even in the low‑mass region below m/z 500. In this application note, dipeptides extracted from natto were analyzed. The results of amino acid composition analysis using the SpiralTOF mode and structural analysis using the TOF‑TOF mode are reported.