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Spin labels as a probe of the molecular environment of covalently bound ligands in an hydrophobic and an hydrophilic polymer.

Authors
  • Pitt, C G1
  • Song, X C
  • Sik, R
  • Chignell, C F
  • 1 Chemistry and Life Sciences, Research Triangle Institute, Research Triangle Park, NC.
Type
Published Article
Journal
Biomaterials
Publisher
Elsevier
Publication Date
Oct 01, 1991
Volume
12
Issue
8
Pages
715–721
Identifiers
PMID: 1665991
Source
Medline
License
Unknown

Abstract

The molecular motions of spin-labelled ligands covalently bound by spacer groups to an hydrophobic and an hydrophilic polymer matrix were evaluated by ESR spectroscopy. The ligands were prepared by alkylation of 4-N-methylamino-TEMPO with the omega-bromocarboxylic esters, Br(CH2)nCOOEt, n = 1,4 and 10. The hydrolysed esters were coupled to a cross-linked aminoethylated polyacrylamide hydrogel (n = 1,4,10) and to a surface hydroxylated elastomeric polyester (n = 4). The rotational correlation times (tau c) of the nitroxide label in the hydrogels were measured in the dry state and after exposure to water at pH 4, 7.4 and 10.5. The tau c of the nitroxide label was insensitive to the length of the spacer group and to the degree of protonation of the tertiary amino group of the ligand. There was no evidence of self-association of the ligand and spacer, or more than a single phase within the polyacrylamide hydrogel. The tau c of the nitroxide labelled polyester was similarly insensitive to pH, but was sensitive to organic solvents. The low mobility of the spin label and its high concentration were consistent with the spin label being covalently bound within the hydrophobic polyester matrix to a depth of at least 5 microns.

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