Scorpions utilize venom to capture prey and protect themselves from predators by showing neurotoxicity against insects and mammals. The scorpion venom also contains various components such as inorganic salts, nucleic acids, lipids, peptides, and proteins. Among them, peptides are main components responsible for the biological activities of the venom. Most of these peptides contain multiple disulfide bonds, but linear peptides without disulfide bonds are also present in the venom, which often exhibit antimicrobial activity. Mass spectrometry plays an important role in the structure determination of these peptides. In this paper, we describe the structural determination of a linear peptide from the venom of the North African scorpion Buthacus leptochelys using de novo sequencing analysis.

Ion detectors for mass spectrometry imaging (MSI) in the microscope-mode need to acquire both the flight time and positional information of an incident ion. ION CAMERA, an ion detector that focuses on enhanced sensitivity and reduced measurement time of microscope-mode MSI, has been developed. ION CAMERA is a type of ion detector that converts an ion image into an optical image using a phosphor and photographs it with a camera. Aiming at applications in target analysis that acquire only the mass images of the target substances with high sensitivity, ION CAMERA adopts a gated image intensifier that can enhance the amount of light in the optical image up to approximately 5000 times in terms of the number of photons. In combination with a fast decay phosphor, it became possible to acquire a time-resolved ion image in a time window of as narrow as 3 ns. To evaluate the prototype ION CAMERA, a microscope-mode MSI apparatus was built as a test platform. A laser system forming a top-hat beam was implemented to achieve desorption ionization with a uniform intensity distribution in the irradiation area, which is ideal for microscope-mode MSI. A high-voltage power supply unit for the post-extraction differential acceleration (PEDA), which retains ion images and enhances mass resolution, was implemented. To acquire mass images of two substances with largely different masses, the high-voltage power supply unit is able to alternate between two PEDA settings for each laser irradiation event. A sample spot, in which an imaging area consisted of two different dye regions and was patterned with a fine grid, was measured for the verification of ION CAMERA. It was demonstrated that mass images of the two kinds of dyes in the imaging area of 700×700 μm were acquired in 20 s. In the case of target analysis whose MSI objectives are limited to a few kinds of analytes, ION CAMERA has a potential to conduct measurements in a shorter time than other detectors for microscope-mode MSI.