Structural investigation of microbial poly(?-L-lysine) derivatives with azo dyes by solid-state 13C and 15 N NMR

Abstract

Solid-state high-resolution 13C and 15N NMR spectra of microbial poly(e-lysine) (e-PL) derivatives with azo dyes have been measured. Chemically modified derivatives of e-PL, e-PL/MO and e-PL/DC were prepared through reactions with methyl orange (MO) and dabsyl chloride (DC), respectively. Side chain α-amino groups of e-PL in e-PL/MO are involved in ionic bonds with methyl orange to form poly-ion complexes, (e-PL)-NH3+SO3--(MO). On the other hand, e-PL is allowed to react with dabsyl chloride in e-PL/DC to form covalent sulfonamide bonds, (e-PL)-NH-SO2-(DC). These chemically modified e-PL’s exhibit 15N NMR signals characteristic of the binding mode at the α-amino groups. The spectral analysis reveals that the e-PL/DC sample contains a small amount of ion complexes with MO. It has been shown that 15N solid-state NMR is a useful tool for structural determination of e-PL and its derivatives.