H-PRO-PRO-PRO-PRO-OH

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.

The antioxidant properties of the barley glutelin hydrolysates were evaluated based on their radical scavenging capacity (DPPH/O₂(·-)/OH(·)), Fe(2+)-chelating effect and reducing power. Alcalase hydrolysates (AH) demonstrated significantly higher antioxidant capacity than those treated by flavourzyme in most of the assays. The AH was separated using ultra-filtration and reversed-phase chromatography, and assessment of the fractions indicated that the large-sized peptides (Mw>10 kDa) possessed stronger DPPH scavenging activity and reducing power, whereas small-sized peptides (Mw<1 kDa) were more effective in Fe(2+)-chelating and OH(·) scavenging effect. The hydrophobic fraction contributed more to Fe(2+)-chelating and OH(·) scavenging activity. Four peptides contributing to antioxidant activities were identified using LC-MS/MS: Gln-Lys-Pro-Phe-Pro-Gln-Gln-Pro-Pro-Phe, Pro-Gln-Ile-Pro-Glu-Gln-Phe, Leu-Arg-Thr-Leu-Pro-Met and Ser-Val-Asn-Val-Pro-Leu. Compared to the positive controls, AH exhibited excellent Fe(2+)-chelating activity and strong DPPH/OH scavenging effect. Thus hydrolyzed barley glutelin is a potential source of antioxidant peptides for food and nutraceutical applications.

Stabilities and conformational properties of two Pro --> Thr point mutation models were computed at the B3LYP/6-31G(d) level of theory for the parent triamino acid diamide Pro-Pro-Pro (HCO-Pro-Pro-Pro-NH2). Geometrical parameters for the amino acid sequences, used in the molecular orbital computations for Pro-Pro-Thr and Pro-Thr-Pro, were retrieved from the Protein Data Bank. Thermodynamic functions (S, H, G) were computed for the fully optimized geometries. To assess the stabilization energetics of these mutant models, relative to the parent Pro-Pro-Pro reference conformer epsilon(L) epsilon(L) gamma(L), isodesmic reactions were constructed to calculate DeltaS, DeltaH, and DeltaG. The importance of intramolecular hydrogen bonds involving the -OH group of the Thr side chain, which emerged after the point mutations, was also examined to determine the internal stabilization of these peptide models. This study describes an approach to analyzing a point mutation at the center of a peptide chain and compares its stability to that of a point mutation at a terminal end in a small peptide model.