Browsing by Subject "Membranes"

Now showing 1 - 6 of 6
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    Cation-selective channel is regulated by anions according to their Hofmeister ranking
    (Wiley, 2017-03-20) Gurnev, Philip A.; Roark, Torri C.; Petrache, Horia I.; Sodt, Alexander J.; Bezrukov, Sergey M.; Physics, School of Science
    Specificity of small ions, the Hofmeister ranking, is long-known and has many applications including medicine. Yet it evades consistent theoretical description. Here we study the effect of Hofmeister anions on gramicidin A channels in lipid membranes. Counterintuitively, we find that conductance of this perfectly cation-selective channel increases about two-fold in the H2PO4−
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    Development and characterization of novel ZnO-loaded electrospun membranes for periodontal regeneration
    (Elsevier, 2015-09) Münchow, Eliseu A.; Albuquerque, Maria Tereza P.; Zero, Bianca; Kamocki, Krzysztof; Piva, Evandro; Gregory, Richard L.; Bottino, Marco C.; Department of Restorative Dentistry, IU School of Dentistry
    OBJECTIVES: This study reports on the synthesis, materials characterization, antimicrobial capacity, and cytocompatibility of novel ZnO-loaded membranes for guided tissue/bone regeneration (GTR/GBR). METHODS: Poly(ɛ-caprolactone) (PCL) and PCL/gelatin (PCL/GEL) were dissolved in hexafluoropropanol and loaded with ZnO at distinct concentrations: 0 (control), 5, 15, and 30wt.%. Electrospinning was performed using optimized parameters and the fibers were characterized via scanning and transmission electron microscopies (SEM/TEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), contact angle (CA), mechanical testing, antimicrobial activity against periodontopathogens, and cytotoxicity test using human dental pulp stem cells (hDPSCs). Data were analyzed using ANOVA and Tukey (α=5%). RESULTS: ZnO nanoparticles were successfully incorporated into the overall submicron fibers, which showed fairly good morphology and microstructure. Upon ZnO nanoparticles' incorporation, the PCL and PCL/GEL fibers became thicker and thinner, respectively. All GEL-containing membranes showed lower CA than the PCL-based membranes, which were highly hydrophobic. Overall, the mechanical properties of the membranes were reduced upon ZnO incorporation, except for PCL-based membranes containing ZnO at the 30wt.% concentration. The presence of GEL enhanced the stretching ability of membranes under wet conditions. All ZnO-containing membranes displayed antibacterial activity against the bacteria tested, which was generally more pronounced with increased ZnO content. All membranes synthesized in this study demonstrated satisfactory cytocompatibility, although the presence of 30wt.% ZnO led to decreased viability. SIGNIFICANCE: Collectively, this study suggests that PCL- and PCL/GEL-based membranes containing a low content of ZnO nanoparticles can potentially function as a biologically safe antimicrobial GTR/GBR membrane.
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    Interaction of TBC1D9B with Mammalian ATG8 Homologues Regulates Autophagic Flux
    (Springer Nature, 2018-09-10) Liao, Yong; Li, Min; Chen, Xiaoyun; Jiang, Yu; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of Medicine
    Autophagosomes are double-membraned vesicles with cytosolic components. Their destination is to fuse with the lysosome to degrade the enclosed cargo. However, autophagosomes may be fused with other membrane compartments and possibly misguided by the RAB molecules from these compartments. The mechanisms ensuring the proper trafficking are not well understood. Yeast ATG8 and its mammalian homologues are critically involved in the autophagosome formation and expansion. We hypothesized that they could be also involved in the regulation of autophagosome trafficking. Using the yeast two-hybrid system, we found that TBC1D9B, a GTPase activating protein for RAB11A, interacted with LC3B. TBC1D9B could also interact with other mammalian ATG8 homologues. This interaction was confirmed with purified proteins in vitro, and by co-immunoprecipitation in vivo. The interacting domain of TBC1D9B with LC3 was further determined, which is unique and different from the known LC3-interacting region previously defined in other LC3-interacting molecules. Functionally, TBC1D9B could be co-localized with LC3B on the autophagosome membranes. Inhibition of TBC1D9B suppressed the turnover of membrane-bound LC3B and the autophagic degradation of long-lived proteins. TBC1D9B can thus positively regulate autophagic flux, possibly through its GTPase activity to inactivate RAB11A, facilitating the proper destination of the autophagosomes to the degradation.
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    Quantitation of Trastuzumab and an Antibody to SARS-CoV-2 in Minutes Using Affinity Membranes in 96-Well Plates
    (American Chemical Society, 2022) Tan, Hui Yin; Yang, Junyan; Linnes, Jacqueline C.; Welch, Christopher J.; Bruening, Merlin L.; Chemistry and Chemical Biology, School of Science
    Quantitation of therapeutic monoclonal antibodies (mAbs) in human serum could ensure that patients have adequate levels of mAbs for effective treatment. This research describes the use of affinity, glass-fiber membranes in a 96-well-plate format for rapid (<5 min) quantitation of the therapeutic mAb trastuzumab and a mAb against the SARS-CoV-2 spike protein. Adsorption of a poly(acrylic acid)-containing film in membrane pores and activation of the -COOH groups in the film enable covalent-linking of affinity peptides or proteins to the membrane. Passage of mAb-containing serum through the affinity membrane results in mAb capture within 1 min. Subsequent rinsing, binding of a secondary antibody conjugated to a fluorophore, and a second rinse yield mAb-concentration-dependent fluorescence intensities in the wells. Calibration curves established from analyses on different days have low variability and allow determination of mAb levels in separately prepared samples with an average error <10%, although errors in single-replicate measurements may reach 40%. The assays can occur in diluted serum with physiologically relevant mAb concentrations, as well as in undiluted serum. Thus, the combination of 96-well plates containing affinity membranes, a microplate reader, and a simple vacuum manifold affords convenient mAb quantitation in <5 min.
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    Regulation of the Sae Two-Component System by Branched- Chain Fatty Acids in Staphylococcus aureus
    (American Society for Microbiology, 2022) Pendleton, Augustus; Yeo, Won-Sik; Alqahtani, Shahad; DiMaggio, Dennis A., Jr.; Stone, Carl J.; Li, Zhaotao; Singh, Vineet K.; Montgomery, Christopher P.; Bae, Taeok; Brinsmade, Shaun R.; Microbiology and Immunology, School of Medicine
    Staphylococcus aureus is a ubiquitous Gram-positive bacterium and an opportunistic human pathogen. S. aureus pathogenesis relies on a complex network of regulatory factors that adjust gene expression. Two important factors in this network are CodY, a repressor protein responsive to nutrient availability, and the SaeRS two-component system (TCS), which responds to neutrophil-produced factors. Our previous work revealed that CodY regulates the secretion of many toxins indirectly via Sae through an unknown mechanism. We report that disruption of codY results in increased levels of phosphorylated SaeR (SaeR~P) and that codY mutant cell membranes contain a higher percentage of branched-chain fatty acids (BCFAs) than do wild-type membranes, prompting us to hypothesize that changes to membrane composition modulate the activity of the SaeS sensor kinase. Disrupting the lpdA gene encoding dihydrolipoyl dehydrogenase, which is critical for BCFA synthesis, significantly reduced the abundance of SaeR, phosphorylated SaeR, and BCFAs in the membrane, resulting in reduced toxin production and attenuated virulence. Lower SaeR levels could be explained in part by reduced stability. Sae activity in the lpdA mutant could be complemented genetically and chemically with exogenous short- or full-length BCFAs. Intriguingly, lack of lpdA also alters the activity of other TCSs, suggesting a specific BCFA requirement managing the basal activity of multiple TCSs. These results reveal a novel method of posttranscriptional virulence regulation via BCFA synthesis, potentially linking CodY activity to multiple virulence regulators in S. aureus.