Sepsis is a life-threatening health condition characterized by bacterial infection with a strong inflammatory response. The response from our innate immune system to the bacteria releases the inflammatory products and mediators which subsequently causes the pathogenesis of sepsis. A major component responsible for the inflammation is lipopolysaccharide (LPS), mostly found in the outer membrane of gram-negative bacteria, which also contributes significantly to the structural integrity of the gram-negative bacteria. The LPS interacts with the macrophage receptor protein, cluster of differentiation 14 (CD14), via its Lipid A moiety. The LPS-binding protein (LBP) is another important factor in the pathogenesis of gram-negative bacterial sepsis through LBP-LPS complexation. Our focus is to study the structures and interactions of Kdo2-Lipid A (KLA), a Re LPS, with the proteins LBP and CD14 and an LPS-antagonist; AM12, using Langmuir-Blodgett (LB) trough and atomic force microscopy (AFM). The LPS-antagonist; AM12 is a lipid analog containing a glucopyranoside core, hydrophobic ether substituents, and an amino acid to provide an ionic character, which has been shown to be an effective inhibitor of LPS-induced tumor necrosis factor-alpha (TNF-alpha) production in human macrophages. We study the monolayers of the Re LPS and some other membrane lipids, trying to mimic the outer membrane of gram-negative bacteria, using LB trough. The pressure-area isotherm obtained by the LB method is very helpful for investigating the phase transitions of the monolayers at different surface pressures and molecular areas. After transferring these monolayers onto a solid substrate, the AFM is used to study their surface structures, mechanical properties, and interactions with some proteins and LPS-antagonist mentioned above. In this poster, we focus on the monolayer study using a Re LPS along with some membrane lipids, for a better understanding of their structures and interactions, mainly with LBP, CD14, and AM12.

Monolayer study of Kdo2-Lipid A (KLA) and its interactions with some proteins (LBP and CD14) and an LPS-antagonist; AM12

ACS Spring Meeting 2021

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