Stability, flow alignment and a phase transition of the lipidic cubic phase during continuous flow injection

Area of Science:

• Structural biology
• Materials science
• Biophysics

Background:

• Continuous flow injection is crucial for serial crystallography of protein crystals in lipidic cubic phases (LCP).
• The influence of the injection process on LCP structure and stability remains under-explored.
• Understanding LCP behavior during injection is vital for optimizing crystal delivery and data acquisition.

Purpose of the Study:

• To investigate the structural modifications of lipidic cubic phases induced by continuous flow injection.
• To determine how injection parameters affect LCP phase behavior and stability.
• To correlate observed phase changes with injection pressure and lipid flow dynamics.

Main Methods:

• Small-angle X-ray scattering (SAXS) was employed to analyze monoolein:water mixtures during continuous injection.
• High viscosity injectors were used for controlled delivery of the LCP.
• Finite element modeling (FEM) was utilized to simulate pressure effects on the lipid stream.

Main Results:

• Continuous injection caused alignment and structural modification of the LCP.
• The orientation of the cubic lattice showed anisotropy, not aligning with a single low-order zone axis.
• LCP phase transitions were observed, shifting from diamond (Pn3m) to gyriod (Ia3d) and lamellar (Lα) phases post-injection.
• Solvent fraction influenced LCP stability during the injection process.

Conclusions:

• The injection process significantly impacts LCP structure and phase composition.
• Injection pressure is a key factor driving observed phase transitions in monoolein:water mixtures.
• These findings highlight the importance of optimizing injection protocols for reliable serial crystallography experiments.