r alkylamino, and NH--(CH2)2 NHR', wherein said substituted lower alkylamino is substituted with an amino or lower alkyl acylamino group and R' is a member selected from the group consisting of acetyl, p-hydroxyphenylpropionyl, d-biotinyl, alpha-bromo-acetyl, methyl fumaryl, d-biotinyl-??-aminocaproyl, an amino acid of the L-configuration, an amino acid of the D-configuration and a monoaryl grou