Related Experiment Video
Updated: May 7, 2026
11:53
Crystallization of Membrane Proteins in Lipidic Mesophases
Published on: March 28, 2011
Crystalline polymorphism induced by charge regulation in ionic membranes.
Cheuk-Yui Leung1, Liam C Palmer, Sumit Kewalramani
1Departments of Physics and Astronomy, Chemistry, Materials Science and Engineering, and Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208.
Summary
Controlling 2D crystallization in amphiphile membranes is key for biology and biotechnology. Researchers found that pH and tail length tune molecular packing and crystalline phase symmetry in these self-assembling systems.
Area of Science:
- Biophysics
- Materials Science
- Supramolecular Chemistry
Background:
- Crystallization of molecules with both polar and hydrophobic groups, like ionic amphiphiles and proteins, is crucial in biology and biotechnology.
- Understanding the self-assembly and crystallization of amphiphiles is essential for designing novel materials and biotechnological applications.
Purpose of the Study:
- To investigate how to control the 2D crystallization process in amphiphile membranes by manipulating interactions between polar and hydrophobic groups.
- To explore the influence of pH and hydrophobic tail length on the molecular packing and crystalline phase symmetry of coassembled amphiphiles.
Main Methods:
- Coassembly of dilysine (+2) and carboxylate (-1) amphiphiles with varying tail lengths at different pH values.
- In situ small- and wide-angle X-ray scattering (SAXS/WAXS) to determine crystalline structures.
- Atomistic molecular dynamics (MD) simulations to analyze intermolecular interactions and packing.
Main Results:
- Hexagonal molecular ordering observed for C14 amphiphiles in crystalline bilayers.
- Decreased hexagonal lattice spacing with increasing tail length due to enhanced van der Waals interactions.
- A reentrant phase transition sequence (hexagonal-rectangular-C-rectangular-P-rectangular-C-hexagonal) observed for C16 and C18 amphiphiles with increasing pH.
- Increased stability of rectangular phases, maximizing tail packing, with longer hydrophobic tails.
Conclusions:
- The 2D crystallization of amphiphile membranes can be precisely controlled by tuning the balance of long-range and short-range interactions through pH and tail length.
- Systematic control over crystalline phase symmetry and molecular packing is achievable, offering pathways for energy exchange under physiological conditions.
- This study provides fundamental insights into the self-assembly behavior of ionic amphiphiles, with implications for biomaterials and nanotechnology.
Related Concept Videos
02:42Ionic Crystal Structures
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
01:15Potentiometry: Membrane Electrodes
Membrane electrodes, also known as p-ion electrodes, use membranes that selectively interact with free analyte ions, generating a potential difference across the membrane. The resulting membrane potential, known as the asymmetry potential, is not zero even when analyte concentrations on both sides of the membrane are equal. The membrane's response is typically not selective to a single analyte but proportional to the concentration of all ions in the sample solution capable of interacting at the...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:54Molecular and Ionic Solids
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions.
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
01:21Polymer Classification: Crystallinity
Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
01:28Ionic Association
The ionic association is the association of oppositely charged ions in an electrolyte solution to form ion pairs. Bjerrum defined ion pairs as two oppositely charged ions whose electrostatic attraction exceeds the thermal energy of the system, typically expressed as 2kT. Electrostatic attraction depends on ionic charge, separation distance, and the dielectric constant of the medium. Thermal energy, represented by kT, reflects the tendency of ions to move independently due to molecular motion.