Membranes

We previously demonstrated that Sartobind Rapid A Protein A membrane provides better resolution than traditional resin-based Protein A column. It seems that, in comparison to the Protein A column, Sartobind Rapid A membrane can better differentiate species with different molecular weights. In the current work, we further studied Sartobind Rapid A’s molecular weight-based separation potential by using it to process eight Fc-containing molecules with distinct molecular weights. The data suggested that, except for one molecule, there is a strong correlation between a molecule’s retention time and its molecular weight. In general, larger molecules tend to have longer retention. In relevance to its application in antibody purification, Sartobind Rapid A membrane’s molecular weight-based separation potential can be translated into strong byproduct-removing capabilities. As demonstrated in the present work, under optimized conditions, Sartobind Rapid A membrane effectively removed aggregates and half-antibody, two common byproducts that are remarkably different from the product in molecular weight. Thus, Sartobind Rapid A membrane’s unique separation capability makes it a more attractive tool than resin-based Protein A columns in antibody/Fc-fusion purification, especially for molecules with complex byproduct profiles.

Synaptobrevin (Syb/VAMP) is the vesicular SNARE that drives synaptic vesicle fusion. Before fusion, Syb is located in the vesicle membrane. After fusion, Syb is translocated to the presynaptic plasma membrane and exposed to a different lipid environment. How its membrane-proximal juxtamembrane and transmembrane domains (JMD–TMDs) organize these different surrounding membrane environments remains incompletely understood. Here, we used MARTINI coarse-grained molecular dynamics simulations in planar membrane models to investigate Syb1/2 membrane organization and collective behavior. Syb1 and Syb2 induced similar and robust local lipid disorder, whereas the spatial organization of lipid disorder and membrane mismatch depended more strongly on membrane lipid composition. In ten-copy systems, mean cluster sizes over the final 100 ns were approximately 30% lower for wild-type Syb1 and 39% lower for wild-type Syb2 in PIP₂-depleted than in the corresponding PIP₂-containing plasma membranes. Collective Syb assembly was accompanied by pronounced PIP₂ redistribution and strong local enrichment, whereas PS showed substantially weaker local enrichment when both lipid species were present. Clustering spatially overlapped otherwise localized lipid-disordered regions without proportionally amplifying their magnitude. The applicability of these findings to curved vesicles and fusion or endocytic intermediates remains to be established. Together, these results distinguish robust local membrane disorder from composition-dependent geometric remodeling and identify PIP₂ as a prominent correlate of higher-order Syb organization that may contribute to post-fusion Syb reorganization before endocytic retrieval.

To address the severe membrane fouling caused by swine manure digestate, this study provides a systematic evaluation of how pore size governs purification efficiency and flux recovery. SEM-EDS and ATR-FTIR were employed to characterize the foulants across five different pore sizes. The results revealed significant differences in flux retention and permeate quality, with smaller-pore membranes exhibiting superior antifouling performance. At a volume reduction factor of 5, the flux decline rates of the 50, 200, 500, 800, and 1200 nm membranes were 34.7%, 8.8%, 33.6%, 40.5%, and 72.2%, respectively. Notably, the 200 nm membrane achieved the highest flux maintenance and recovery after chemical cleaning, whereas the 1200 nm membrane suffered the greatest flux decline and poorest effluent quality. The 800 nm membrane experienced severe fouling likely driven by particulate deposition and cake layer formation. Based on the combined characterization results, polysaccharides and protein-like substances are suggested to be the primary organic foulants. The proposed fouling mechanisms likely involve cake layer formation on the membrane surface, along with concentration polarization and pore blocking. Furthermore, the internal adsorption of soluble organics likely contributes to irreversible fouling. Overall, this study not only elucidates the pore size-dependent fouling mechanisms but also establishes the 200 nm ceramic membrane as a highly promising pre-treatment candidate for digestate concentration processes.