How do chain lengths of acyl-l-carnitines affect their surface adsorption and solution aggregation?

Area of Science:

• Biochemistry
• Materials Science
• Physical Chemistry

Background:

• Acyl-l-carnitines (CnLC) are biocompatible surfactants with potential in technical, personal care, and healthcare applications.
• Understanding the relationship between CnLC molecular structure and physical properties is crucial for optimizing their use.
• Cellular energy generation involves acyl-l-carnitines in fatty acid transport.

Purpose of the Study:

• To investigate the influence of acyl chain lengths of acyl-l-carnitines (CnLC) on their solubility, surface adsorption, and aggregation behavior.
• To determine the critical micellar concentrations (CMCs) and analyze the structure of adsorbed CnLC layers.
• To explore the structural changes of micellar aggregates under varying environmental conditions.

Main Methods:

• Surface tension measurements to determine critical micellar concentrations (CMCs).
• Neutron reflection (NR) to study the structure and composition of adsorbed CnLC layers.
• Dynamic light scattering (DLS) and small angle neutron scattering (SANS) to analyze micellar aggregate structures.

Main Results:

• Solubility of CnLC decreases significantly with increasing acyl chain length, exhibiting hysteresis.
• CMCs decrease notably with longer acyl chains (C12LC: 1.1 mM, C14LC: 0.10 mM, C16LC: 0.010 mM at pH 7).
• Adsorbed layer thickness and area per molecule at CMC increase with acyl chain length, and spherical micelles show increased core radius.

Conclusions:

• Acyl chain length is a critical factor determining the physicochemical properties of acyl-l-carnitines.
• The study provides a foundational understanding of CnLC behavior, essential for developing targeted applications.
• CnLCs demonstrate tunable surfactant properties based on molecular structure and environmental conditions.