The present invention provides a self-assembly of a compound or of a pharmaceutically acceptable salt thereof, the compound being represented by formula (I) R1-Gly LeuAla Met Ala Pro Ser Val Gly His ValArg Gln His Gly-R2 (I)(wherein R1 represents a linear or branched acyl group having 14 to 24 carbon atoms R2 represents OH, NH2, NR3R4, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted aralkyloxy group and R3 and R4 independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted aralkyl group, an alkoxy group, or a hydroxy group, provided that both R3 and R4 do not represent a hydroxy group or an alkoxy group simultaneously).
