Polymeric fluorescent dyes for labeling of proteins and nucleic acids

Modification of EDC method for increased labeling efficiency and characterization of low-content protein in gum acacia using asymmetrical flow field-flow fractionation coupled with multiple detectors

1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) is widely used as a crosslinker for fluorescence labeling of protein in the fields of biochemistry and food analysis. Many natural polysaccharides often contain some proteins or peptides that are very low in content but play a vital role in their biological function as well as technical applications. Determination of these low-content proteinaceous matters requires a highly sensitive and selective method. In this study, a methodological approach for investigations of the presence of proteinaceous material over the molar mass distribution (MD) of polysaccharides was developed using gum acacia (GA) as a model polysaccharide. EDC fluorescence-labeling method was modified by changing the pH (7, 9, and 11) of the solution for the analysis of low-content protein in food materials. Fluorescence spectroscopy and asymmetrical flow field-flow fractionation (AF4) were employed for characterizing the labeling efficiency and physiochemical properties of unlabeled and fluorescence-labeled GA. AF4 provided molar mass (M) and the radius of gyration (r_G) of arabinogalactan (AG) and arabinogalactan protein complex (AGP) and determined the presence of proteinaceous matter over the MD. The labeling efficiencies of GA at pH 7, 9, and 11 determined by fluorescence spectroscopy were 56.5, 68.4, and 72.0%, respectively, with an increment of 15.5% when pH was increased from 7 to 11. The modified EDC fluorescence-labeling method allows highly sensitive and selective analysis of low-content proteinaceous matters and their distribution in natural polysaccharides.

Ionomer and protein size analysis by analytical ultracentrifugation and electrospray scanning mobility particle sizer

By combining analytical ultracentrifugation (AUC) in liquid phase and scanning mobility particle sizer (SMPS) in the gas phase, additional information on the particle size and morphology has been obtained for rigid particles. In this paper, we transfer this concept to soft particles, allowing us to analyze the size and molar mass of the short side chain perfluorosulfonic acid ionomer Aquivion^® in a dilute aqueous suspension. The determination of the primary size and exact molar mass of this class of polymers is challenging since they are optically transparent and due to the formation of different aggregate structures depending on the concentration and solvent properties. First, validation of AUC and SMPS measurements was carried out using the well-defined biopolymers bovine serum albumin (BSA) and lysozyme (LYZ) to confirm the reliability of the results of the two unique and independent classifying methods. Then, the ionomer Aquivion^® was studied using both techniques. From the mean molar mass of 185 ± 14 kDa obtained by AUC, a mean hydrodynamic diameter of 7.6 ± 0.5 nm was calculated. The particle size obtained from SMPS (7.1 nm) agrees very well with the results from AUC showing that the molecule was transferred into the gas phase without significantly changing its structure. In conclusion, the Aquivion^® is molecularly dispersed in the used aqueous buffer solution without any aggregate formation in the investigated concentration range (< 2 g l^-1).

Radical polymerization in biosensing

This review briefly summarizes recently published work on radical polymerization in biosensor-related applications. Advancements in surface modification aimed at improving sensor biocompatibility and reducing nonspecific background noises are discussed. Direct applications of polymers as one of the key sensing elements in which they are used either as detection probes for the biomolecular binding events or as signal transducers to amplify sensing signals are detailed. Initial applications of radical polymerization reactions in biosensing are evident and appear promising.

Sustained off-resonance irradiation collision-induced dissociation of linear, substituted and cyclic polyesters using a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer

The fragment ions obtained from sustained off-resonance irradiation collision-induced dissociation of linear polyesters, substituted polyesters and cyclic polyesters have been characterized using a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer. Charge-induced and charge-remote fragmentation channels, together with the participation of other nucleophilic groups, are proposed for the substituted polyesters. The linear polyesters were found to fragment at equivalent positions along the polymer chain whereas, under the experimental conditions employed, the cyclic polyester produced a single fragment.