ABSTRACT
The molecular-recognition abilities of a water-soluble chitin derivative, chitin-graft-polysarcosine (2) were investigated using chitinase, lysozyme, and wheat germ agglutinin (WGA). The enzymatic degradabilities of 2 were evaluated using chitinase and lysozyme. The molecular weight of those compounds of 2 with a higher affinity toward water decreased rapidly, as compared with partially deacetylated chitin (1). The 1H NMR spectrum of the low-molecular-weight fraction, yielded after lysozymic hydrolysis, indicated that saccharide residues in the chitinous backbone were specifically recognized by the lysozyme, then beta-glycosidic linkages in the backbone were selectively hydrolyzed. Furthermore, the molecular-recognition ability of the chitinous backbone of graft copolymer 2 toward the lectin WGA was elucidated by the enzyme-linked lectin-binding assay (ELLA). It was revealed that the graft copolymer with a lower degree of substitution (DS) value efficiently interacted with WGA. Interestingly, a graft copolymer having longer polysarcosine side chains showed higher recognition ability toward WGA than that having short side chains.
Subject(s)
Chitin/metabolism , Chitinases/metabolism , Muramidase/metabolism , Peptides/metabolism , Polymers/metabolism , Sarcosine/analogs & derivatives , Sarcosine/metabolism , Wheat Germ Agglutinins/metabolism , Chitin/chemistry , Peptides/chemistry , Polymers/chemistry , Sarcosine/chemistry , Substrate Specificity , Time Factors , Wheat Germ Agglutinins/chemistryABSTRACT
Binding of poly(amido amine) dendrimer to sodium hyaluronate (NaHA) in aqueous 0.25 M NaCl solution has been investigated by static light scattering. It was observed that the apparent weight-average molecular weight and the radius of gyration increase with the ratio of NH(2) terminal groups in the dendrimer to the carboxylate groups in the NaHA, [NH(2)]/[COO(-)]. Up to [NH(2)]/[COO(-)]=31, the observed variation of molecular weight was reproduced by the "average binding" model, where an average number of dendrimers binds to each NaHA chain. Based on the "critical binding" model, the maximum number, n(max), of dendrimers which can bind to a NaHA chain was calculated to be n(max)=300 for a solution of [NH(2)]/[COO(-)]=56. The obtained value corresponds to the binding of one dendrimer per 1.5 repeating units on a NaHA chain. It is suggested from the observed radius of gyration that, while the dendrimer-NaHA complexes of [NH(2)]/[COO(-)] up to 5 maintain a wormlike character similar to NaHA without bound dendrimers, those of [NH(2)]/[COO(-)] above 10 behave like rigid rods. It is concluded that the hydrogen-bonding interaction, besides the electrostatic interaction, should play an important role in the formation of the NaHA-dendrimer complexes.
Subject(s)
Hyaluronic Acid/chemistry , Polyamines/chemistry , Sodium Chloride/chemistry , Carboxylic Acids/chemistry , Dimerization , Electrochemistry , Light , Models, Chemical , Models, Molecular , Protein Binding , Scattering, RadiationABSTRACT
Stereoselective polymerization of racemic lactide (rac-LA) was examined using Al-achiral ligand complexes. By introduction of substituents in aromatic rings of Schiff base ligands, a higher selectivity was obtained without any chiral auxiliaries in the catalyst via a chain-end control mechanism. The T(m) values (T(m) 170-192 degrees C) were comparable to or higher than that of homochiral polymer, poly(L-LA) (T(m) 162 degrees C), and a thermally more stable polylactide than poly(L-LA) was prepared from rac-LA.
