End-group distributions of multiple generations of spin-labeled PAMAM dendrimers.

Dendrimers are attractive templates to display functional molecular components. Since the behavior of dendrimer systems can depend greatly on the accessibility of these molecular components to the external environment, and on the spatial arrangement of functional groups attached to the dendrimer terminal branches (end-groups), techniques to determine the locations of end-groups are highly desirable. In this report, we describe a method to analyze the EPR spectra of multiple generations of poly(amidoamine) (PAMAM) dendrimers which have spin-labels attached to end-groups in variable percentages of the total number of available sites. The spectra are treated as a convolution of a narrow spin-label spectrum and a variable line broadening function. Trends in the parameters that describe the best-fit line broadening function with spin-label loading reveal the spatial arrangements and homogeneity of spin environments of the labels. We observe a shift in the end-group distribution from generation 3 (G(3)) to G(4) dendrimers that indicates a change in morphology from an open, extended structure to a more dense, compact arrangement.

Characterization of heterogeneously functionalized dendrimers by mass spectrometry and EPR spectroscopy.

Starburst dendrimers are receiving considerable attention as templates for the assembly of structured arrays of molecular components. This research motivates the development of improved methods for dendrimer characterization-specifically, for determining the numbers, distributions of numbers, and spatial distribution of molecular species synthetically attached to macromolecular templates. Such information provides the basis for advancing strategies aimed at controlling dendrimer functionalization, and thus represents enabling technology for tailoring the composition and structure of molecular arrays fashioned on dendrimer templates. Moreover, this information is vital to the proper interpretation of ongoing experiments in which dendrimers sparsely functionalized with reporter groups are used as probes. In this article, we report MALDI-TOF mass spectrometry and EPR spectroscopy of heterogeneously functionalized G(4)-PAMAM dendrimers bearing nitroxide spin-labels.

EPR and affinity studies of mannose-TEMPO functionalized PAMAM dendrimers.

Mannose-TEMPO functionalized G4-PAMAM dendrimers with increasing mannose loadings have been synthesized and characterized by MALDI-TOF MS and EPR spectroscopy. Analysis of linebroadening effects in the EPR spectra of these dendrimers allowed us to determine the relative presentation of mannose and TEMPO on the dendrimer surface. Hemagglutination assays and affinity chromatography/EPR experiments to assess the activity of the mannose-TEMPO dendrimers with Concanavalin A are presented.