Abstract
We investigated the relationship between the ability of model peptides for group-3 late embryogenesis abundant (G3LEA) proteins as anti-aggregation reagents for dried liposomes and conformational features in the dried state mixed with liposomes. For this purpose, the following four peptides were tested: 1) PvLEA-22, which consists of two tandem repeats of the 11-mer motif characteristic to LEA proteins from an African sleeping chironomide, 2) its control, i.e., the peptide with the amino acid composition identical to that of PvLEA-22, although the amino acid sequence is randomly arranged, 3) Poly-L-glutamic acid, and 4) Poly-L-lysine. The peptides 1) and 2) suppressed the desiccation-induced aggregation of liposomes prepared with POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine). On the other hand, two homopolypeptides 3) and 4) exhibited no such protective effects. For all of these dried samples, Fourier transform infrared spectroscopic measurements were carried out to examine the gel-to-liquid crystalline phase transitions of the liposomes and to know the conformational structures of the mixed peptides. As a result, the G3LEA model peptide was found to be able to bind the dried liposome surface in an appropriate manner, accompanied by extension of its peptide backbone, and thereby to make itself capable of acting as a molecular shielding reagent of liposomes against desiccation-induced aggregation.
