Browsing by Author "Harnaguchi, Hiro-o"

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Disentangling Dynamic Changes of Multiple Cellular Components during the Yeast Cell Cycle by in Vivo Multivariate Raman Imaging
(2012-07-03)
Huang, Chuan-Keng
;
Ando, Masahiro
;
Harnaguchi, Hiro-o
;
Shigeto, Shinsuke
;
應用化學系
Cellular processes are intrinsically complex and dynamic, in which a myriad of cellular components including nucleic acids, proteins, membranes, and organelles are involved and undergo spatiotemporal changes. Label-free Raman imaging has proven powerful for studying such dynamic behaviors in vivo and at the molecular level. To construct Raman images, univariate data analysis has been commonly employed, but it cannot be free from uncertainties due to severely overlapped spectral information. Here, we demonstrate multivariate curve resolution analysis for time-lapse Raman imaging of a single dividing yeast cell. A four-dimensional (spectral variable, spatial positions in the two-dimensional image plane, and time sequence) Raman data "hypercube" is unfolded. to a two-way array and then analyzed globally using multivariate curve resolution. The multivariate Raman imaging thus accomplished successfully disentangles dynamic changes of both concentrations and distributions of major cellular components (lipids, proteins, and polysaccharides) during the cell cycle of the yeast cell. The results show a drastic decrease in the amount of lipids by similar to 50% after cell division and uncover a protein-associated component that has not been detected with previous univariate approaches.
Estimating Percent Crystallinity of Polyethylene as a Function of Temperature by Raman Spectroscopy Multivariate Curve Resolution by Alternating Least Squares
(2017-03-07)
Samuel, Ashok Zachariah
;
Lai, Bo-Han
;
Lan, Shih-Ting
;
Ando, Masahiro
;
Wang, Chien-Lung
We have recently demonstrated a methodology to estimate the percent crystallinity (PC) of polymers directly with Raman spectroscopy and multivariate curve resolution (MCR) by alternating least-squares (ALS). In the MCR-ALS methodology, the Raman spectrum of a semicrystalline polymer is separated into two constituent components (crystalline and molten/amorphous) and their corresponding concentrations. The methodology necessitates that the Raman spectrum at any temperature be a linear combination of two MCR spectral components (one molten and one crystalline). This is true in the case of simple systems such as crystalline pendant alkyl domains in polymers (Samuel et al. Anal. Chem. 2016, 88, 4644). However, in the case of main chain polymer crystals (e.g., polyethylene), the situation can be complicated owing to several molecular changes in the lattice in addition to conformational reorganizations during melting. Under this circumstance, a simple two-state model may not be adequate and we describe the modifications required to treat such systems, keeping the basic principles of the proposed methodology unchanged. A comparative study with wide-angle X-ray scattering (WAXS) and Raman spectroscopy is also performed to substantiate our findings. In addition to estimating percent crystallinity (PC), our methodology is capable of revealing additional information, such as interchain interactions in crystal lattice, that in principle will help distinguishing polymorphic transformations, subtle changes in lamellar lattice dimensions, and other phase changes in polymers.