Molecular conformational changes in the collapsing and reswelling processes occurring during the phase transition at the lower critical solution temperature (LCST) of the polymer are not well understood. In this study, we characterized the conformational change of Poly(oligo(Ethylene Glycol) Methyl Ether Methacrylate)-144 (POEGMA-144) synthesized on silica nanoparticles using Raman spectroscopy and zeta potential measurements. Changes in distinct Raman peaks associated with the oligo(Ethylene Glycol) (OEG) side chains (1023, 1320, and 1499 cm) with respect to the methyl methacrylate (MMA) backbone (1608 cm) were observed and investigated under increasing and decreasing temperature profiles (34 °C to 50 °C) to evaluate the polymer collapse and reswelling around its LCST (42 °C). In contrast to the zeta potential measurements that monitor the change in surface charges as a whole during the phase transition, Raman spectroscopy provided more detailed information on vibrational modes of individual molecular moieties of the polymer in responding to the conformational change.
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http://dx.doi.org/10.3390/s23125713 | DOI Listing |
J Am Chem Soc
January 2025
Department of Chemistry, Brandeis University, 415 South St., Waltham, Massachusetts 02454, United States.
Despite their critical role in context-dependent interactions for protein functions, intrinsically disordered regions (IDRs) are often overlooked for designing peptide assemblies. Here, we exploit IDRs to enable context-dependent heterotypic assemblies of intrinsically disordered peptides, where "context-dependent" refers to assembly behavior driven by interactions with other molecules. By attaching an aromatic segment to oppositely charged intrinsically disordered peptides, we achieve a nanofiber formation.
View Article and Find Full Text PDFMethods Mol Biol
January 2025
Estrella Mountain Community College, Phoenix, AZ, USA.
Vacuole fusion is driven by SNARE proteins that require activation-or priming-by the AAA+ protein Sec18 (NSF) before they can bring membranes together and trigger the merger of two bilayers into a continuous membrane. Sec18 resides on vacuoles prior to engaging inactive cis-SNARE complexes through its interaction with the regulatory lipid phosphatidic acid (PA). Binding PA causes Sec18 to undergo large conformational changes that keeps it bound to the membrane, thus precluding its interactions with SNAREs.
View Article and Find Full Text PDFMethods Mol Biol
January 2025
Department of Chemistry, Institute of Biomedical Sciences and Multiscale Research Institute of Complex Systems, Fudan University, Shanghai, China.
Steered Molecular Dynamics (SMD) simulation is a powerful computational simulation technique that enables the controlled manipulation of molecular systems by applying external forces. This method is frequently utilized to investigate the slow processes of biomolecular systems that occur within sub-second to second time scales, achieved through SMD simulations that only span nanoseconds. SMD simulation can be utilized to study the detailed mechanism of protein conformational changes, protein unfolding, and ligand dissociation, etc.
View Article and Find Full Text PDFEMBO J
January 2025
The Hormel Institute, University of Minnesota, Austin, MN, 55912, USA.
ABCB1 is a broad-spectrum efflux pump central to cellular drug handling and multidrug resistance in humans. However, how it is able to recognize and transport a wide range of diverse substrates remains poorly understood. Here we present cryo-EM structures of lipid-embedded human ABCB1 in conformationally distinct apo-, substrate-bound, inhibitor-bound, and nucleotide-trapped states at 3.
View Article and Find Full Text PDFLeukemia
January 2025
The Clara D. Bloomfield Center for Leukemia Outcomes Research, The Ohio State University Comprehensive Cancer Center, Columbus, OH, USA.
The FLT3 gene frequently undergoes mutations in acute myeloid leukemia (AML), with internal tandem duplications (ITD) and tyrosine kinase domain (TKD) point mutations (PMs) being most common. Recently, PMs and deletions in the FLT3 juxtamembrane domain (JMD) have been identified, but their biological and clinical significance remains poorly understood. We analyzed 1660 patients with de novo AML and found FLT3-JMD mutations, mostly PMs, in 2% of the patients.
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