Conformation of Pyrene-Labeled Amylose in DMSO Characterized with the Fluorescence Blob Model

Abstract

Amylose and poly(methyl acrylate) were randomly labeled with pyrene to yield a series of Py-Amylose and Py-PMA constructs, and their ability to form excimer in DMSO was characterized quantitatively by steady-state and time-resolved fluorescence. First, the ratio of the fluorescence intensity of the excimer over that of the monomer, namely the IE/IM ratio, was obtained from the fluorescence spectra. Second, the product ⟨kblob × Nblob⟩ was obtained from the fluorescence blob model (FBM) analysis of the fluorescence decays. Both IE/IM and ⟨kblob × Nblob⟩ yielded similar values when expressed in terms of moles of pyrene per backbone atom for Py-Amylose and Py-PMA. Since IE/IM and ⟨kblob × Nblob⟩ reflect the efficiency of pyrene excimer formation, the similar behavior observed for both parameters obtained for rigid amylose and flexible PMA could only be rationalized by postulating that amylose adopted a compact helical conformation in DMSO. To confirm whether this was possible, molecular mechanics optimization...