A novel insecticidal peptide (LaIT3) was isolated from the Liocheles australasiae venom. The primary structure of LaIT3 was determined by a combination of Edman degradation and MS/MS de novo sequencing analysis. Discrimination between Leu and Ile in MS/MS analysis was achieved based on the difference in side chain fragmentation assisted by chemical derivatization. LaIT3 was determined to be an 84-residue peptide with three intrachain disulfide bonds. The sequence similarity search revealed that LaIT3 belongs to the scorpine-like peptides consisting of two structural domains: an N-terminal α-helical domain and a C-terminal cystine-stabilized domain. As observed for most of the scorpine-like peptides, LaIT3 showed significant antibacterial activity against Escherichia coli, which is likely to be caused by its membrane-disrupting property.

Over 200 components with molecular mass ranging mainly from 400 to 4000 Da were characterized from the venom of the vermivorous cone snail Conus fulgetrum that inhabit Egyptian Red Sea. One major component having a molecular mass of 2946 Da was purified by HPLC, and its primary structure was determined by a combination of Edman degradation and MS/MS analysis.

Scorpion venom contains various bioactive peptides. Among them, peptides having two different structural domains constitute a toxin family known as β‐KTx or scorpine‐like peptides. These peptides consist of an α‐helical structure in the N‐terminal region and a cysteine‐stabilized structure in the C‐terminal region. This unique structure of β‐KTx peptides contributes to their diverse biological functions, but the importance of each domain for their activities is not fully understood. LaIT2 is a β‐KTx peptide isolated from the venom of the scorpion Liocheles australasiae, which shows both insecticidal and antimicrobial activities. In this study, we chemically synthesized full‐length LaIT2 using a native chemical ligation technique as well as its N‐terminally or C‐terminally truncated single‐domain analogs to evaluate structural factors important for the activities. Biological evaluation of these peptides revealed that the N‐terminal α‐helical domain of LaIT2 is essential for the expression of both insecticidal and antibacterial activities. This suggests that the disruption of membrane structures largely accounts for the biological activities of LaIT2.

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A novel anti-mollusk conopeptide pn4c was isolated from the Conus pennaceus venom by repeated HPLC fractionation based on the activity against freshwater snails. The primary structure of pn4c was determined by the mass spectrometric de novo sequencing analysis. In addition, pn3a was isolated from the same fraction containing pn4c, as a peptide with unknown functions.