Lipopolysaccharides (LPS) are a major component of the protective outer membrane of Gram-negative bacteria. Understanding how the solution conditions may affect LPS-containing membranes is important to optimizing the design of antibacterial agents (ABAs) which exploit electrostatic and hydrophobic interactions to disrupt the bacteria membrane. Here, interactions between surface layers of LPS (Ra mutants) in aqueous media have been studied using a surface force apparatus (SFA), exploring the effects of temperature and divalent Ca cations. Complementary dynamic light scattering (DLS) characterization suggests that vesicle-like aggregates of diameter ∼28-80 nm are formed by LPS-Ra in aqueous media. SFA results show that LPS-Ra vesicles adsorb weakly onto mica in pure water at room temperature (RT) and the surface layers are readily squeezed out as the two surfaces approach each other. However, upon addition of calcium (Ca) cations at near physiological concentration (2.5 mM) at RT, LPS multilayers or deformed LPS liposomes on mica are observed, presumably due to bridging between LPS phosphate groups and between LPS phosphates and negatively charged mica mediated by Ca, with a hard wall repulsion at surface separation ∼ 30-40 nm. At 40 °C, which is above the LPS-Ra β-α acyl chain melting temperature ( = 36 °C), fusion events between the surface layers under compression could be observed, evident from δ ∼ 8-10 nm steps in the force-distance profiles attributed to LPS-bilayers being squeezed out due to enhanced fluidity of the LPS acyl-chain, with a final hard wall surface separation ∼ 8-10 nm corresponding to the thickness of a single bilayer confined between the surfaces. These unprecedented SFA results reveal intricate structural responses of LPS surface layers to temperature and Ca, with implications to our fundamental understanding of the structures and interactions of bacterial membranes.
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http://dx.doi.org/10.1021/acs.langmuir.9b02609 | DOI Listing |
Soft Matter
January 2025
Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
In this work, a theoretical approach is developed to investigate the structural properties of ionic microgels induced by a circularly polarized (CP) electric field. Following a similar study on chain formation in the presence of linearly polarized fields [T. Colla , , 2018, , 4321-4337], we propose an effective potential between microgels which incorporates the field-induced interactions a static, time averaged polarizing charge at the particle surface.
View Article and Find Full Text PDFEur J Nucl Med Mol Imaging
January 2025
Departments of Radiology and Medical Physics, University of Wisconsin - Madison, Madison, WI, 53705, USA.
Purpose: Trophoblast cell-surface antigen 2 (Trop2) is overexpressed in various solid tumors and contributes to tumor progression, while its expression remains low in normal tissues. Trop2-targeting antibody-drug conjugate (ADC), sacituzumab govitecan-hziy (Trodelvy), has shown efficacy in targeting this antigen. Leveraging the enhanced specificity of ADCs, we conducted the first immunoPET imaging study of Trop2 expression in gastric cancer (GC) and triple-negative breast cancer (TNBC) models using Zr-labeled Trodelvy ([Zr]Zr-DFO-Trodelvy).
View Article and Find Full Text PDFEur J Nucl Med Mol Imaging
January 2025
Institute of Radiation Medicine, Fudan University, Xietu Road 2094, Shanghai, 200032, China.
Objectives: Mesothelin (MSLN) is an antigen that is overexpressed in various cancers, and its interaction with tumor-associated cancer antigen 125 plays a multifaceted role in tumor metastasis. The serum MSLN expression level can be detected using enzyme-linked immunosorbent assay; however, non-invasive visualization of its expression at the tumor site is currently lacking. Therefore, the aim of this study was to develop a molecular probe for imaging MSLN expression through positron emission tomography (PET).
View Article and Find Full Text PDFACS Nano
January 2025
Creative Research Initiative Center for Nanospace-confined Chemical Reactions (NCCR), Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea.
Unlike homogeneous metal complexes, achieving absolute control over reaction selectivity in heterogeneous catalysts remains a formidable challenge due to the unguided molecular adsorption/desorption on metal-surface sites. Conventional organic surface modifiers or ligands and rigid inorganic and metal-organic porous shells are not fully effective. Here, we introduce the concept of "ligand-porous shell cooperativity" to desirably reaction selectivity in heterogeneous catalysis.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
Harbin Institute of Technology, School of Chemistry and Chemical Engineering, No. 92, West Dazhi Street, 150001, Harbin, CHINA.
Commercial hard carbon (HC) anode suffers from unexpected interphase chemistry rooted in the parasitic reactions between surface oxygen-functional groups and ester-based electrolytes. Herein, an innovative strategy is proposed to regulate interphase chemistry by tailoring targeted functional groups on the HC surface, where highly active undesirable oxygen-functional groups are skillfully converted into a Si-O-Si molecular layer favorable for anchoring anions. Then, an inorganic/organic hybrid solid electrolyte interphase with low interfacial charge transfer resistance and enhanced cycling durability is constructed successfully.
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