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Related Concept Videos

Formation of Lipopolysaccharides01:19

Formation of Lipopolysaccharides

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Lipopolysaccharides (LPS) are crucial components of the outer membrane of Gram-negative bacteria, serving both structural and functional roles. It contributes to membrane stability and protects bacteria from host immune responses. LPS is composed of three major regions—lipid A, a core oligosaccharide, and an O antigen. The biosynthesis and assembly of LPS involve a highly coordinated set of enzymatic reactions and transport mechanisms. Additionally, LPS is recognized as an endotoxin,...
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Biosynthesis of Lipids01:29

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Microbial membranes exhibit remarkable diversity in lipid composition, reflecting evolutionary adaptations to various environmental conditions. The three domains of life—Bacteria, Archaea, and Eukarya—synthesize membrane lipids through distinct biosynthetic pathways, leading to fundamental structural differences that impact membrane stability, function, and adaptability.Fatty Acid-Based Lipids in Bacteria and EukaryaBacteria and eukaryotes share a common fatty acid biosynthesis...
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Outer Layers of the Cell Envelope01:18

Outer Layers of the Cell Envelope

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The outermost layers of prokaryotic cells play a critical role in their survival, virulence, and interaction with the environment. These layers, often composed of polysaccharides, polypeptides, or proteins, form protective and adhesive structures that vary in organization and function.Capsules and Slime LayersCapsules are highly organized, tightly bound layers that firmly attach to the bacterial cell wall. Capsules are usually made of polysaccharides, though some are made of polypeptides. These...
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Asymmetric Lipid Bilayer01:35

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Biological membranes show uneven distribution of different types of lipids in the inner and outer layers, resulting in transverse asymmetric membranes. The treatment of the erythrocyte membrane with the enzyme phospholipase confirmed the asymmetric nature of the lipid bilayer. The enzyme hydrolyzes lipids into fatty acids and hydrophilic groups. The phospholipase acts only on the outer layer of the membrane, while the inner layer remains intact. The phospholipase treatment resulted in 80%...
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Bacterial Cell Wall01:22

Bacterial Cell Wall

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The bacterial cell wall is an essential structural component that encases the plasma membrane, preserving cellular integrity, determining shape, and protecting against osmotic stress. This rigid yet flexible structure primarily comprises peptidoglycan, a polymer that forms a mesh-like matrix conferring mechanical strength and flexibility.Peptidoglycan Composition and StructurePeptidoglycan, the core of the bacterial cell wall, comprises alternating units of N-acetylglucosamine (NAG) and...
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Assembly of the Lipid Bilayer in the ER01:28

Assembly of the Lipid Bilayer in the ER

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Biological membranes are more than just a barrier separating cell cytoplasm from the outside environment. They are highly dynamic and help maintain the integrity and physiological stability of the cells as well as membrane-bound organelles. Membranes also play vital roles in cell-to-cell and intracellular communication.
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Related Experiment Video

Updated: Dec 28, 2025

Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria
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Ionic Environment Affects Bacterial Lipopolysaccharide Packing and Function.

Ali Rahnamoun1, Kyoungtea Kim2, Joel A Pedersen2,3

  • 1Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States.

Langmuir : the ACS Journal of Surfaces and Colloids
|February 19, 2020
PubMed
Summary
This summary is machine-generated.

Metal cations influence lipopolysaccharide (LPS) packing and stability in bacterial membranes. Cation properties like charge and size critically affect LPS aggregation and ligand interactions, impacting outer membrane function.

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Purification and Visualization of Lipopolysaccharide from Gram-negative Bacteria by Hot Aqueous-phenol Extraction
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Separation of the Cell Envelope for Gram-negative Bacteria into Inner and Outer Membrane Fractions with Technical Adjustments for Acinetobacter baumannii
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Purification and Visualization of Lipopolysaccharide from Gram-negative Bacteria by Hot Aqueous-phenol Extraction
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Purification and Visualization of Lipopolysaccharide from Gram-negative Bacteria by Hot Aqueous-phenol Extraction

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Area of Science:

  • Biophysics
  • Structural Biology
  • Microbiology

Background:

  • Lipopolysaccharides (LPS) are key components of the Gram-negative bacterial outer membrane.
  • LPS structure and stability are significantly influenced by interactions with metal cations.
  • Understanding these interactions is crucial for comprehending bacterial membrane function and developing antimicrobial strategies.

Purpose of the Study:

  • To investigate the impact of metal cation properties (valency and ionic radius) on the packing and stability of deep rough (Re) LPS.
  • To determine how the ionic environment affects LPS aggregation and the intercalation of ligands into LPS bilayers.
  • To elucidate the mechanisms by which cations modulate LPS-ligand interactions.

Main Methods:

  • Molecular dynamics simulations were employed to model LPS behavior in various ionic environments.
  • Langmuir balance experiments were conducted to measure LPS molecular area at the air-water interface.
  • Enhanced sampling techniques were used to calculate the free energy of ligand intercalation into LPS bilayers.

Main Results:

  • LPS array packing and aggregation are sensitive to both cation valency and ionic radius.
  • The mean molecular area of LPS, reflecting aggregation, varied significantly with different cations.
  • Cation-dependent affinity of LPS to oligo(allylamine HCl) was observed, with ion bridging and steric effects being more dominant than charge shielding at low ionic concentrations.

Conclusions:

  • Metal cations play a critical role in modulating the structural organization and stability of LPS.
  • The findings highlight the importance of ion bridging and steric factors in LPS-ligand interactions within the bacterial membrane.
  • This research provides insights into the fundamental biophysics of bacterial outer membranes and potential targets for therapeutic intervention.