Novel Casein-Derived Peptide-Zinc Chelate: Zinc Chelation and Transepithelial Transport Characteristics

Casein-derived peptides are recognized as promising candidates for improving zinc bioavailability through the form of a peptide-zinc chelate. In the present work, a novel 11-residue peptide TEDELQDKIHP identified from casein hydrolysate in our previous study was synthesized to investigate the zinc chelation characteristics. Meanwhile, the digestion stability and transepithelial transport of TEDELQDKIHP-Zn were also investigated. The obtained results indicated that the carboxyl groups (from Asp and Glu), amino groups (from Lys and His), pyrrole nitrogen group of Pro, and imidazole nitrogen group of His were responsible for zinc chelation. The complexation with zinc resulted in a more ordered structure of TEDELQDKIHP-Zn. In terms of digestion stability, the chelate of TEDELQDKIHP-Zn could remain stable to a large extent after gastric (78.54 ± 0.14%) and intestinal digestion (70.18 ± 0.17%). Moreover, TEDELQDKIHP-Zn was proven to be a well-absorbed biological particle with a P_app value higher than 1 × 10^-6 cm/s, and it could be transported across the intestine epithelium through transcytosis. TEDELQDKIHP-Zn exhibited more bioavailable effects on zinc absorption and ALP activity than inorganic zinc sulfate.

Antarctic Krill Derived Nonapeptide as an Effective Iron-Binding Ligand for Facilitating Iron Absorption via the Small Intestine

A novel nonapeptide DTDSEEEIR identified from Antarctic krill (Euphausia superba) iron-binding peptides was used in this study to analyze its iron-binding sites and structural changes after iron coordination. The enzymatic resistance and transport of DTDSEEEIR-iron during gastrointestinal digestion and absorption as well as the relationship between the DTDSEEEIR stability and the enhancement of iron absorption were further explored. Results revealed that iron ions spontaneously bound to the carboxyl, hydroxyl, and amino groups of the DTDSEEEIR peptide, which induced the folding of DTDSEEEIR to form a more orderly structure. The DTDSEEEIR peptide remained stable to a certain extent (79.60 ± 0.19%) after gastrointestinal digestion and the coordination of iron improved the digestive stability of the DTDSEEEIR peptide (93.89 ± 1.37%). Moreover, the stability of DTDSEEEIR across intestinal epithelium had a positive effect on iron absorption, which implied that DTDSEEEIR might carry iron ions through intestinal epithelial cells.

Water-Alcohol Bigels from Fatty Acylated Dipeptides

Peptide-based gels are emerging as an interesting class of biocompatible soft materials. 9-Fluorenylmethoxycarbonyl-protected amino acids and short peptides have gained considerable attention as promising gelators. Peptide amphiphiles, wherein an alkyl chain is appended to a polar peptidic moiety, are another important class of peptide-based gelators. Here, we report the alcohol/water bigels formed by the rather simple fatty acylated dipeptides wherein the peptidic moiety is made up of hydrophobic amino acids, viz., Val, Ile, and Leu. Lauroyl, myristoyl, and palmitoyl were investigated as the N-terminal fatty acyl groups. None of the lauroylated peptides caused gelation of methanol/water and ethanol/water mixtures up to 2 wt % peptide concentration. Eight out of the 27 peptides resulted in distinct bigels. The gels are composed of fibrous aggregates as characterized by electron microscopy. Infrared spectroscopy suggests the β-sheet conformation of the peptidic region in the gels. Using the Ma-IV ethanol/water bigel as the representative gel, entrapment and steady release of the anticancer drug docetaxel are demonstrated. Such bigels from rather simple amphipathic peptides that are easily synthesized and purified through solvent extraction could be attractive gelator candidates with potential application in drug delivery.

Calcium Delivery System Assembled by a Nanostructured Peptide Derived from the Sea Cucumber Ovum

In this study, the binding mechanism, morphological, and conformational analysis of the complex of a sea cucumber ovum derived octapeptide (EDLAALEK) with Ca²⁺ as well as its calcium delivery behavior via the gastrointestinal (GI) tract were investigated. The Ca²⁺ specifically bound to two carboxyl oxygen atoms of C-terminal Glu and Asp on the EDLAALEK peptide at a stoichiometric ratio of 1:1. Calcium coordination induced the self-assembly of the EDLAALEK peptide, resulting in the formation of a nanocomposite with a crystal structure. Furthermore, the formed nanocomposite went through dissociation and self-assembly during in vitro GI digestion, accompanied by the release and rechelation of Ca²⁺, which was related to changes in their secondary structure. Nevertheless, the GI digests of the EDLAALEK-calcium complex could significantly enhance Ca²⁺ absorption across Caco-2 cell monolayers. The findings suggest that the sea cucumber ovum derived peptide has the potential as an efficient nanocarrier to transport calcium through the GI system.

In vitrodigestion profile and calcium absorption studies of a sea cucumber ovum derived heptapeptide–calcium complex

A novel sea cucumber ovum derived heptapeptide (NDEELNK) could bind one calcium ionviaits carboxyl oxygen and amino nitrogen atoms, and the formed complex underwent disaggregation and self aggregation during simulated gastrointestinal digestion.

Reverse thermo-responsive hydrogels prepared from Pluronic F127 and gelatin composite materials

A series of F127–gelatin composite hydrogels with reverse thermo-responsive and tunable mechanical properties were developed.