Related Experiment Video
Updated: Apr 27, 2026
09:45
Fluorescence Lifetime Imaging of Molecular Rotors in Living Cells
Published on: February 9, 2012
27.6K
Influence of molecular coherence on surface viscosity
Siyoung Q Choi1, Kyuhan Kim, Colin M Fellows
1Chemical Engineering and Materials Science, University of Minnesota , Minneapolis, Minnesota 55455, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 4, 2014
Summary
Adding small amounts of cholesterol dramatically lowers the interfacial viscosity of dipalmitoylphosphatidylcholine (DPPC) monolayers. This occurs because cholesterol induces nanophase separation, altering molecular coherence and reducing viscosity.
Area of Science:
- Physical Chemistry
- Materials Science
- Biophysics
Background:
- Interfacial viscosity is crucial for understanding lipid monolayer behavior.
- Dipalmitoylphosphatidylcholine (DPPC) is a key component of biological membranes.
- Cholesterol's role in modulating lipid monolayer properties is of significant interest.
Purpose of the Study:
- To investigate the effect of small cholesterol fractions on DPPC monolayer interfacial viscosity.
- To elucidate the structural changes induced by cholesterol in DPPC monolayers.
- To develop a model explaining the relationship between molecular coherence and surface viscosity.
Main Methods:
- Grazing incidence X-ray diffraction (GIXD) was used to analyze monolayer structure.
- Interfacial viscosity measurements were performed.
- Data analysis involved applying the Cohen and Turnbull free area model.
Main Results:
- Cholesterol addition, even in small fractions, reduced interfacial viscosity by an order of magnitude.
- GIXD revealed nanophase separation into ordered DPPC and disordered DPPC-cholesterol phases.
- A universal logarithmic relation for surface viscosity was established based on free area and coherence.
Conclusions:
- Cholesterol incorporation into DPPC monolayers leads to nanophase separation, not ideal mixing.
- The free area model, modified for molecular coherence, successfully explains viscosity changes.
- Molecular coherence is a fundamental determinant of interfacial viscosity in ordered lipid monolayers.
Related Concept Videos
02:57Surface Tension, Capillary Action, and Viscosity
28.5K
Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
28.5K
01:22Surface Tension of Fluid
1.9K
Surface tension is a fundamental property of fluids, occurring at the boundary between a liquid and a gas or between two immiscible liquids. This phenomenon arises from the cohesive forces between molecules at the fluid's surface, creating an effect similar to a stretched elastic membrane. Inside each fluid, molecules are equally attracted in all directions by neighboring molecules, but surface molecules experience a net inward force, resulting in surface tension.
Surface tension varies...
Surface tension varies...
1.9K
01:19Viscosity of Fluid
2.2K
Viscosity measures the resistance a fluid offers to flow and deformation. It results from internal friction between layers of fluid moving relative to one another. Dynamic viscosity, denoted by the Greek letter mu (μ), quantifies the force needed to move one fluid layer over another. For Newtonian fluids like water and air, the relationship between the shearing stress and the rate of shearing strain is linear, meaning their viscosity remains constant regardless of the applied stress.
2.2K
01:16Surface Tension and Surface Energy
3.2K
When a paint brush is immersed in water, the bristles wave freely inside the water. When it is taken out, the bristles stick together. The reason behind this effect is surface tension.
Consider a beaker filled with liquid. The bulk molecules in the liquid experience equal attractive forces on all sides with the surrounding molecules. However, the surface molecules experience a net attractive force downward due to the bulk molecules. The surface of the liquid behaves like a stretched membrane,...
Consider a beaker filled with liquid. The bulk molecules in the liquid experience equal attractive forces on all sides with the surrounding molecules. However, the surface molecules experience a net attractive force downward due to the bulk molecules. The surface of the liquid behaves like a stretched membrane,...
3.2K
01:17Viscosity
5.6K
When water is poured into a glass, it falls freely and quickly, whereas if honey or maple syrup is poured over a pancake, it flows slowly and sticks to the surface of the container. This difference in the flow of different kinds of liquids arises due to the fluid friction between the liquid layers and the liquid and the surrounding material. This property of fluids is called fluid viscosity. In this example, water has a lower viscosity than honey and maple syrup.
The SI unit of viscosity is...
The SI unit of viscosity is...
5.6K
01:27Viscosity
174
Viscosity is a property of fluids that measures their resistance to flow. It is influenced by factors such as the surface area of contact, the gradient of flow speed, and the fluid's viscosity constant, called the coefficient of viscosity. The coefficient of viscosity, also known as dynamic viscosity, is denoted by the symbol η. It determines the proportionality between the viscous force and the gradient of flow speed.Newton's law of viscosity states that the viscous force on a...
174