Capillary‐channeled polymer (C‐CP) fibers are demonstrated as a selective stationary phase for phosphopeptide analysis via LC–MS. Taking advantage of the oxidative self‐polymerization of dopamine under alkaline conditions, a simple system involving a dilute aqueous solution of 0.2% w/v dopamine hydrochloride in 0.15% w/v TRIS buffer, pH 8.5 was utilized to coat polydopamine onto nylon 6 C‐CP fibers. Confirmation of the polydopamine coating on the fibers (nylon‐PDA) was made through attenuated total reflection‐FTIR (ATR‐FTIR) analysis. Imaging using SEM was also performed to examine the morphology and topography of the nylon‐PDA. Subsequent loading of Fe3+to the nylon‐PDA matrix was confirmed by SEM/energy dispersive X‐ray spectroscopy (SEM/EDX). The Fe3+‐bound nylon‐PDA fibers packed in a microbore column format were tested in the off‐line preconcentration of phosphopeptides from a 1:100 mixture of β‐casein/BSA digests for MALDI‐TOF analysis. The packed column was also installed onto an HPLC system as a platform for the online sample clean‐up and enrichment of phosphopeptides from a 1:1000 mixture of β‐casein/BSA protein digests that were determined by subsequent ESI–MS analysis.
Inorganic salts usually demonstrate simple phasal behaviors in dilute aqueous solution mainly involving soluble (homogeneous) and insoluble (macrophase separation) scenarios. Herein, we report the discovery of complex phase behavior involving multiple phase transitions of clear solution – macrophase separation – gelation – solution – macrophase separation in the dilute aqueous solutions of a structurally well-defined molecular cluster [Mo7O24]6−macroanions with the continuous addition of Fe3+. No chemical reaction was involved. The transitions are closely related to the strong electrostatic interaction between [Mo7O24]6−and their Fe3+counterions, the counterion-mediated attraction and the consequent charge inversion, leading to the formation of linear/branched supramolecular structures, as confirmed by experimental results and molecular dynamics simulations. The rich phase behavior demonstrated by the inorganic cluster [Mo7O24]6−expands our understanding of nanoscale ions in solution.
more » « less- Award ID(s):
- 1904397
- NSF-PAR ID:
- 10413629
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 14
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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