Solid-solid phase transitions (SSPTs) occur between distinguishable crystalline forms. Because of their importance in application and theory in materials science and condensed-matter physics, SSPTs have been studied most extensively in metallic alloys, inorganic salts and small organic molecular crystals, but much less so in biomacromolecular crystals. In general, the mechanisms of SSPTs at the atomic and molecular levels are not well understood. Here, the ordered molecular rearrangements in biomacromolecular crystals of the adenine riboswitch aptamer are described using real-time serial crystallography and solution atomic force microscopy. Large, ligand-induced conformational changes drive the initial phase transition from the apo unit cell (AUC) to the trans unit cell 1 (TUC1). During this transition, coaxial stacking of P1 duplexes becomes the dominant packing interface, whereas P2-P2 interactions are almost completely disrupted, resulting in 'floating' layers of molecules. The coupling points in TUC1 and their local conformational flexibility allow the molecules to reorganize to achieve the more densely packed and energetically favorable bound unit cell (BUC). This study thus reveals the interplay between the conformational changes and the crystal phases - the underlying mechanism that drives the phase transition. Using polarized video microscopy to monitor SSPTs in small crystals at high ligand concentration, the time window during which the major conformational changes take place was identified, and the kinetics have been simulated. Together, these results provide the spatiotemporal information necessary for informing time-resolved crystallography experiments. Moreover, this study illustrates a practical approach to characterization of SSPTs in transparent crystals.
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http://dx.doi.org/10.1107/S2052252521004826 | DOI Listing |
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Department of Genomics and Evolutionary Biology, National Institute of Genetics, Mishima 411-8540, Japan.
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January 2025
Rheology Department, Polymat Institute, University of the Basque Country, 20018 Donostia-San Sebastian, Euskadi, Spain.
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January 2025
Centro de Investigação em Química (CIQUP), Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal.
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January 2025
State Key Laboratory of High-Performance Precision Manufacturing, Dalian University of Technology, Dalian 116024, China.
Laser cladding technology is an effective method for producing wear-resistant coatings on damaged substrates, improving both wear and corrosion resistance, which extends the service life of components. However, the fabrication of hard and brittle materials is highly susceptible to the problem of cracking. Using gradient transition layers is an effective strategy to mitigate the challenge of achieving crack-free laser-melted wear-resistant coatings.
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January 2025
MOE Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, School of Resources, Environment and Materials, Guangxi University, Nanning 530004, China.
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