Bioactive peptides physicochemical properties

Bioactive sequences of up to six amino acid residues known to assume (1- or "/-turns in the bioactive conformation are suitable for such libraries. If the sequence is short, residues have to be added in a manner to retain the desired physicochemical properties of the peptide (e.g., to short polar active sequences hydrophobic residues are preferentially added and vice versa). The choice of the scaffold depends on the number of structure-inducing amino acids such as Gly or Pro present in the native sequence. In absence of such residues scaffolds (1) or (4) (Scheme 24) are selected, whereas if Gly or Pro is present alternative scaffolds can be considered. Then the components of the four stereoisomeric sublibraries of Scheme 26 (or their equivalents if other scaffolds are chosen) are synthesized according to procedures described in the preceding sections. 

Because of their well-recognized physicochemical properties (relatively high hydrophobicity, cationic character, and short length) reversed-phase, size-exclusion, and cation exchange chromatographies are particularly appropriate to purify bioactive peptides from the immune system of invertebrates. The sensitivity of HPLC, MS, Edman degradation, and liquid growth inhibition assays allow one to use from narrow (e.g., 2.1-mm internal diameter) down to micro-or nano-columns. 

Most of the dosage forms of the bioactive protein or peptide are liquid preparations. The permeability of the intestinal mucosa to high-molecular-weight substances is very low. However, oral delivery systems may be developed by manipulation of the physicochemical property of the drug molecule or by devising an effective formulation. 

---