1: Immunology  1990 Feb;69(2):323-8 

Location of membrane-bound hapten with different length spacers.

Kimura K, Arata Y, Yasuda T, Kinosita K, Nakanishi M.

Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.

Immunogenic activity of a lipid hapten is strongly dependent of the length and
nature of the linker chain (spacer) connecting the hapten to the head group of
the lipid. A derivative containing a very short or a long spacer is known to be
less effective for antibody binding than that of an intermediate length. In the
present experiment, this was confirmed first by experiments of antibody binding
to TNP lipid haptens with different length of spacers and of antibody-dependent
macrophage binding to them. Second, we determined the location of the TNP
haptens in lipid bilayer membranes by fluorescence energy transfer. It was found
that vertical distances between TNP groups (acceptors), which were assumed to be
randomly distributed in a plan parallel to the membrane surface, and a pyrene
fluorophore (donor), which was embedded in the middle of lipid membranes, were
10.2-10.5 A in the DMPC membranes and 13.2-13.9 A in the DPPC membranes. The
vertical distances were about 3 A longer in the DPPC membranes than in the DMPC
membranes. However, they were almost independent of the length of spacers. This
indicates that TNP residues of the lipid haptens locate at the similar vertical
position on the membrane surfaces even if they have different length spacers.
From these results we suggested that the affinity of the spacer groups to the
bilayer surfaces can modulate the binding affinity of antibody to lipid hapten
on the membrane surfaces. This was partly supported by the binding experiments
of TNP spacers to the bilayer membranes.

PMID: 2307487 [PubMed - indexed for MEDLINE]