Study of the interaction between end-capped telechelic polymers and the wheat lipid transfer protein LTP1, in solution and at the air/water interface

We report on the interaction, in solution, between a wheat lipid transfer protein (LTP1) and three telechelic polymers, constituted by a polyethylene oxide (PEO) unit of 20, 32 or 35 kDa and end-capped with either palmitic or stearic alkyl chains. These polymers were used as models of the plant polymers, cutin and suberin, which are constituted by esterified hydroxyl-fatty acids. Steady state fluorescence measurement reveal that the protein can bind all these telechelic polymers with a stoichiometry of one polymer per protein, that is, two alkyl chains. This suggests that LTP1 can interconnect alkyl polymers in solution forming macromolecular assemblies. These aggregates were further studied in the case of PEO 32 kDa end-capped with palmitic alkyl chains at the air/water interface by using surface pressure measurements and Brewster angle microscopy (BAM). The presence of domains revealed that aggregates were surface active but were removed from the interface at high surface pressure. This is consistent with the fact that the bound protein masks the alkyl chains making the hydrophobically modified polymer more soluble. Altogether, these results provide evidence that LTP1 could link in a non-covalent way several oligomers in solution and at an interface forming aggregates of macromolecular complexes. (C) 2003 Elsevier B.V. All rights reserved.