Analysis of the binding of polymyxin B to endotoxic lipid A and core glycolipid using a fluorescent displacement probe

S. A. David, K. A. Balasubramanian, V. I. Mathan, P. Balaram

Research output: Contribution to journalArticlepeer-review

49 Scopus citations


Dansylcadaverine, a cationic fluorescent probe binds to bacterial lipopolysaccharide and lipid A, and is displaced competitively by other compounds which possess affinity toward endotoxins. The binding parameters of dansylcadaverine for lipid A were determined by Scatchard analysis to be two apparently equivalent sites with apparent dissociation constants (Kd) ranging between 16 μM to 26 μM, while that obtained for core glycolipid from Salmonella minnesota Re595 yielded a Kd of 22 μM to 28 μM with three binding sites. The Kd of polymyxin B for lipid A was computed from dansylcadaverine displacement by the method of Horovitz and Levitzki (Horovitz, A., and Levitzki, A. (1987) Proc. Natl. Acad. Sci. USA 84, 6654-6658). The applicability of this method for analyzing fluorescence data was validated by comparing the Kds of melittin for lipid A obtained by direct Scatchard analysis, and by the Horovitz-Levitzki method. The displacement of dansylcadaverine from lipid A by polymyxin B was distinctly biphasic with Kds for polymyxin B-lipid A interactions corresponding to 0.4 μM and 1.5 μM, probably resulting as a consequence of lipid A being a mixture of mono- and di-phosphoryl species. This was not observed with core glycolipid, for which the Kd for polymyxin was estimated to range from 1.1 μM to 5.8 μM. The use of dansylcadaverine as a displacement probe offers a novel and convenient method of quantitating the interactions of a wide variety of substances with lipid A.

Original languageEnglish (US)
Pages (from-to)147-152
Number of pages6
JournalBiochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
Issue number2
StatePublished - Dec 2 1992

Bibliographical note

Funding Information:
This work was supportedb y grantsf rom the Indian Council of Medical Research, New Delhi, the Wellcome Trust, London, and the Rockefeller Foundation, New York. SD is a recipient of a Senior Research Fellowshipf rom The Council for Scientific and Industrial Research,G overnmento f India.

Copyright 2014 Elsevier B.V., All rights reserved.


  • Dansylcadaverine
  • Endotoxin
  • Glycolipid
  • Polymyxin B


Dive into the research topics of 'Analysis of the binding of polymyxin B to endotoxic lipid A and core glycolipid using a fluorescent displacement probe'. Together they form a unique fingerprint.

Cite this