Insect oostatic peptide: absence of effect on mice ovaries

Oostatic peptides

Oostatic peptides are organic molecules, which influence an insect reproduction due to a regulation of the eggs development. It was proved that decapeptide-H-Tyr-Asp-Pro-Ala-Pro-Pro-Pro-Pro-Pro-Pro-OH (YDPAPPPPPP)-isolated from mosquito Aedes aegypti, inhibits trypsin activity in the midgut of the mosquito. Therefore, it was named trypsin-modulating oostatic factor (Aea-TMOF). Feeding the recombinant cells with cloned and expressed TMOF on the coat protein of tobacco mosaic virus (TMV) to mosquito larvae, caused larval mortality. The TMOF was therefore designed for usage as a new biorational insecticide against mosquito. Similarly, a hexapeptide-H-Asn-Pro-Thr-Asn-Leu-His-OH (NPTNLH)-was isolated from the grey flesh fly Neobellieria bullata. This peptide and some of its analogs inhibited trypsin-like synthesis by the midgut in female flies and was therefore entitled Neb-TMOF. Interestingly, the synthetic Aea-TMOF and mainly its C-terminus shorten analogs, including those containing D-amino acids or methylene-oxy isosteric bond, quickly and strongly inhibited the hatchability and egg development in the flesh fly N. bullata.

CEC separation of insect oostatic peptides using a strong-cation-exchange stationary phase

The separation of several insect oostatic peptides (IOPs) was achieved by using CEC with a strong-cation-exchange (SCX) stationary phase in the fused-silica capillary column of 75 microm id. The effect of organic modifier, ionic strength, buffer pH, applied voltage, and temperature on peptides' resolution was evaluated. Baseline separation of the studied IOPs was achieved using a mobile phase containing 100 mM pH 2.3 sodium phosphate buffer/water/ACN (10:20:70 v/v/v). In order to reduce the analysis time, experiments were performed in the short side mode where the stationary phase was packed for 7 cm only. The selection of the experimental parameters strongly influenced the retention time, resolution, and retention factor. An acidic pH was selected in order to positively charge the analyzed peptides, the pI's of which are about 3 in water buffer solutions. A good selectivity and resolution was achieved at pH <2.8; at higher pH the three parameters decreased due to reduced or even zero charge of peptides. The increase in the ionic strength of the buffer present in the mobile phase caused a decrease in retention factor for all the studied compounds due to the decreased interaction between analytes and stationary phase. Raising the ACN concentration in the mobile phase in the range 40-80% v/v caused an increase in both retention factor, retention time, and resolution due to the hydrophilic interactions of IOPs with free silanols and sulfonic groups of the stationary phase.