Abstract-The dynamic morphology of glucose as expressed via Raman and terahertz spectroscopy

Naomi V. Fredeen, Nikolai I. Lesack, Antonia Ciocoiu, Alexander M. Garner, Wesley F. Zandberg, Andrew Jirasek, and Jonathan F. Holzman

Experimental schematics for characterizations of quartz-glucose-quartz samples via (a) Raman spectroscopic analyses and (b) THz spectroscopic analyses. In (a), the continuous wave 780-nm pump laser beam is focused into the glucose layer of the sample to generate Raman spectra. In (b), the pulsed 780-nm pump and probe laser beams are directed onto the THz emitter and detector to generate a THz sample spectrum, 𝐸̃ s(𝑓)${\tilde{E}}_{\text{s}}(f)$, and THz reference spectrum, 𝐸̃ r(𝑓)${\tilde{E}}_{\text{r}}(f)$, with and without the sample present, respectively. The ratio of THz sample spectrum, 𝐸̃ s(𝑓)${\tilde{E}}_{\text{s}}(f)$, and THz input spectrum, 𝐸̃ r(𝑓)${\tilde{E}}_{\text{r}}(f)$exp(jk0(2dq+d)), is then used to extract the quartz layers’ refractive index, nq(f), and extinction coefficient, κq(f), and the glucose layer's refractive index, n(f), and extinction coefficient, κ(f). Here, k0 is the wavenumber for the frequency f, dq = 170 µm is the thickness of each quartz layer, and d = 180 µm is the thickness of the glucose layer.

https://www.osapublishing.org/osac/abstract.cfm?uri=osac-3-3-515

The proposed work introduces time-captured Raman and terahertz spectroscopic analyses as orthogonal probes of intramolecular and intermolecular modes in biomolecular structures. The work focuses on glucose given the complexity and dynamics of its anomeric conversion and crystallization. The Raman analyses capture the dynamics of its intramolecular modes – revealing conversion between α and β anomers. At the same time, the terahertz analyses capture the dynamics of its intermolecular modes – showing an evolution from amorphous to crystalline morphology. It is shown that time-captured Raman and terahertz spectroscopy together render a more complete depiction, and deeper understanding, of the biomolecular structure of glucose.

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