| Autor: |
Nowotarski MS; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States., Potnuru LR; Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States., Straub JS; Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, United States., Chaklashiya R; Department of Materials, University of California, Santa Barbara, Santa Barbara, California 93106, United States., Shimasaki T; Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, United States., Pahari B; School of Physical and Applied Sciences, Goa University, Taleigao, Goa 403206, India., Coffaro H; Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, United States., Jain S; Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India., Han S; Department of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California 93106, United States.; Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States.; Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States. |
| Abstrakt: |
Crystallization pathways are essential to various industrial, geological, and biological processes. In nonclassical nucleation theory, prenucleation clusters (PNCs) form, aggregate, and crystallize to produce higher order assemblies. Microscopy and X-ray techniques have limited utility for PNC analysis due to the small size (0.5-3 nm) and time stability constraints. We present a new approach for analyzing PNC formation based on 31 P nuclear magnetic resonance (NMR) spin counting of vitrified molecular assemblies. The use of glassing agents ensures that vitrification generates amorphous aqueous samples and offers conditions for performing dynamic nuclear polarization (DNP)-amplified NMR spectroscopy. We demonstrate that molecular adenosine triphosphate along with crystalline, amorphous, and clustered calcium phosphate materials formed via a nonclassical growth pathway can be differentiated from one another by the number of dipolar coupled 31 P spins. We also present an innovative approach for examining spin counting data, demonstrating that a knowledge-based fitting of integer multiples of cosine wave functions, instead of the traditional Fourier transform, provides a more physically meaningful retrieval of the existing frequencies. This is the first report of multiquantum spin counting of assemblies formed in solution as captured under vitrified DNP conditions, which can be useful for future analysis of PNCs and other aqueous molecular clusters. |
