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Title: Jiří Brus: Domain-edited NMR Crystallography: A Strategy for Determining the Atomic-Resolution Structure of Micro-/Nanocrystalline Composite Solids from NMR Chemical Shifts
Number: 37/21
Status: Closing date exceeded
Begin: Thursday, 20.05. 2021, 14:00
Tutor: Václav Holý, Milan Dopita
Location: Zoom Meeting ID: 971 6810 9563

nanocent


Nano Seminar

 

Thursday, 20. 5. 2021, 14.00,

Join Zoom Meeting
https://cesnet.zoom.us/j/97168109563

Meeting ID: 971 6810 9563

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Jiří Brus

Institute of Macromolecular Chemistry CAS, Prague 6, Czech Republic

Domain-edited NMR Crystallography: A Strategy for Determining the Atomic-Resolution Structure of Micro-/Nanocrystalline Composite Solids from NMR Chemical Shifts

Nanomaterials have consistently attracted the attention for over 60 years. Advancing these materials, however, requires precise structural analysis of individual elements. This is a stringent requirement, as these systems exist at the borderline between crystalline and amorphous solids, for which high-quality diffraction data are inherently unavailable. This contribution thus addresses our attempt to formulate an efficient experimental-computational strategy for obtaining deep insight into the structure of complex polycrystalline composites with micro- and nanodomain architecture. To determine the atomic-resolution structure of these systems, we apply a procedure based on 1H NMR crystallography extended to collect the component-selective data. This strategy is based on the combined application of domain-selective solid-state NMR spectroscopy (ss-NMR), crystal structure prediction (CSP), and density functional theory (DFT)-based calculations of NMR chemical shifts. This combination enables one to determine the structural arrangements of molecules in situations which are not tractable by conventional spectroscopic techniques. Its applications should be of particular importance for the systems, in which phase transformations can occur, and new polymorphic forms can be spontaneously created under the influence of the matrix environment. The potential of this combined analytical approach is highlighted on the recently developed biodegradable, injectable polyanhydride microbead formulation of decitabine, an archetypal DNA methyltransferase inhibitor used as an efficient therapeutic for epigenetic cancer therapy. In this innovative drug-delivery formulation a mixture of microcrystalline domains of decitabine and nanodomains of sebacic acid is embedded in the semicrystalline matrix of poly(sebacic acid) carrier. The proposed method, which employs the confluence of computational data with measured NMR parameters, thus provides a way to distinguish between alternative candidate structures exclusively existing in the composite assembles, and to select the ones that are the most compatible with available information. In the second part of this presentation potentiality of this approach will be demonstrated in de-nuovo determination of the crystal structure of chemotactic N-formyl-L-Met-L-Leu-L-Phe-OH tripeptide. The whole process will be thoroughly discussed step-by-step, and the final crystal structure will be evaluated and compared with the parallelly (independently) determined XRPD model.

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Abstract Brus