Förster resonance energy transfer confirms the bacterial-induced conformational transition in highly-branched poly(N-isopropyl acrylamide with vancomycin end groups on binding to Staphylococcus aureus

Abstract

We describe a series of experiments designed to investigate the conformational transition that highly-branched polymers with ligands undergo when interacting with bacteria, a process that may provide a new sensing mechanism for bacterial detection. Fluorescent highly-branched poly(N-isopropyl acrylamide)s (HB-PNIPAM) were prepared by sequential self-condensing radical copolymerizations, using anthrylmethyl methacrylate (AMMA) and fluorescein-O-acrylate (FA) as fluorescent comonomers and 4-vinylbenzyl pyrrole carbodithioate as a branch forming monomer. Differences in reactivity necessitated to first copolymerize AMMA then react with FA in a separate sequential monomer feed step. Modifications of the chain ends produced vancomycin-functional derivatives (HB-PNIPAM-Van). The AMMA and FA labels allow probing of the conformational behaviour of the polymers in solution via Förster resonance energy transfer experiments. It was shown that interaction of this polymer's end groups with Staphylococcus aureus induced a macromolecular collapse. The data thus provide conclusive evidence for a conformational transition that is driven by binding to a bacterium.

Analysis using size exclusion chromatography of poly( N -isopropyl acrylamide) using methanol as an eluent

“…This shows that these polymers, which have been shown to be stimuli-responsive to bacteria in solution and to be useful for aggregation of bacteria [23], [37], [38], had broad molar mass distributions and that molar mass distributions changed following modification and purification (ultra-filtration and precipitation).…”

“…However, chain end functionalization affects their solubility in traditional SEC solvents [23], [37], [38]. The advent of a methanol based system means for the first time it will be possible to disclose the molar mass of these materials before and after chain-end modification.…”

“…In our experience, the analysis of polyacrylamides often requires changing the eluent if pendant or chain-end functionalities are modified. Some polymers, such as poly( N -isopropyl acrylamide) (PNIPAM) are susceptible to adsorption to the stationary phase and often salts, such as tetrabutylammonium bromide (TBAB), must be added to the mobile phase to prevent interaction [12], [23]. The use of salts requires careful control of eluent composition and in some cases salts precipitate and block components of the instrument.…”

Excited‐State Deactivation of Branched Phthalocyanine Compounds

“…Thus, there have been significant efforts to explore, design, and synthesize artificial molecules, as simplified model systems to simulate the key mechanism of energy and electron migration in natural photosynthetic systems . Their molecular structural features and intramolecular interactions should be suited to energy‐ and electron‐transfer processes . In the past few years, the self‐assembly of the organic chromophores has attracted widespread attention, for example, the discovery of the importance of the position of aggregated chlorophyll molecules in purple bacteria in energy transfer in photosynthesis and the study of excitation‐energy transfers from monomeric subunits to dimeric excimers in the artificial perylenetetracarboxylic diimide (PDI) trimer system .…”

A Novel Thermal-Resistance and Salt-Tolerance Gel with Low-Concentration Crosslinkers for Water Shutoff in Tahe Oilfield

“…Although a fairly wide number of new acrylamide polymers have been described in the literature (L. Mespouille, et al 2009;J. Genzer, et al 2008;P. Sarker, et al 2014), only a relatively small number of them, including acrylamide copolymers of t-butyl acrylate (tBA), N-vinyl pyrrolidone (N-VP), 2-acrylamido-2-methyl-propanesulfonate (AMPS), and N-vinyl acetamide (N-VA), have been commercialized.…”