研究目的
To analyze the filtration behavior of protein crystal suspensions with low volume samples using a newly developed filtration cell for an analytical photocentrifuge, focusing on properties like cake resistance, compressibility, and crystal breakage.
研究成果
The study successfully demonstrates that the 3D-printed filtration cell with the LUMiSizer ? centrifuge enables efficient analysis of filtration properties using low-volume samples. Key findings include higher compressibility and cake resistance for needle-shaped lysozyme crystals compared to isometric ones, and crystal breakage occurs at low pressures. The method allows direct measurement of cake height and other parameters without complex models, making it valuable for optimizing solid-liquid separation in protein processing.
研究不足
The method is limited to small sample volumes and may not fully replicate conditions of large-scale filtration. The pressure decreases during centrifugation, affecting constant pressure assumptions. Membrane resistance measurements with water may not accurately represent particulate systems, and polydisperse materials can lead to differences in cake structure compared to conventional methods. The centrifuge's acceleration time can cause initial pressure variations.
1：Experimental Design and Method Selection:
The study uses a newly designed 3D-printed filtration cell integrated with the LUMiSizer ? analytical photocentrifuge to perform centrifugal filtration experiments. The method allows in-situ monitoring of cake height and filtration parameters using small sample volumes (200-300 μL). Theoretical models based on Darcy's equation and centrifugal pressure calculations are employed.
2：Sample Selection and Data Sources:
Lysozyme crystals (isometric and needle-shaped) are used as model protein crystals. They are produced via specific crystallization methods (e.g., displacement crystallization for isometric crystals and vacuum evaporation for needle-shaped crystals). Samples are characterized using static laser scattering for particle size distribution.
3：List of Experimental Equipment and Materials:
Equipment includes the LUMiSizer ? centrifuge (LUM GmbH, Germany), a 3D-printed filtration cell, filter membranes (e.g., pore sizes 0.20 μm, 0.22 μm, 0.45 μm), O-rings, support structures, and a static laser scattering device (Sympatec Helos, Germany). Materials include hen-egg lysozyme, sodium acetate buffer, sodium chloride, and other chemicals for crystallization.
4：20 μm, 22 μm, 45 μm), O-rings, support structures, and a static laser scattering device (Sympatec Helos, Germany). Materials include hen-egg lysozyme, sodium acetate buffer, sodium chloride, and other chemicals for crystallization.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The filtration cell is assembled with filter media and placed in the centrifuge. Samples (200-300 μL) are loaded, and centrifugation is performed at speeds from 200 to 4000 rpm. Light transmission profiles are recorded to track interfaces (e.g., liquid-gas, sedimentation front). Experiments include cake formation and cake wash procedures. Data on positions, pressures, and resistances are derived from transmission profiles.
5：Data Analysis Methods:
Data analysis involves determining phase positions from transmission profiles, calculating pressures using integrated equations, and deriving filtration resistances and solids volume fractions. Software like MATLAB ? and ImageJ is used for particle size analysis and distribution calculations. Empirical fits (e.g., Tiller and Kwon approach) are applied to characterize compressibility.
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