Browsing by Author "Yoshikiyo, Keisuke"

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Imaging phospholipid conformational disorder and packing in giant multilamellar liposome by confocal Raman microspectroscopy
(2017-12-05)
Noothalapati, Hemanth
;
Iwasaki, Keita
;
Yoshimoto, Chikako
;
Yoshikiyo, Keisuke
;
Nishikawa, Tomoe
Liposomes are closed phospholipid bilayer systems that have profound applications in fundamental cell biology, pharmaceutics and medicine. Depending on the composition (pure or mixture of phospholipids, presence of cholesterol) and preparation protocol; intra- and inter-chain molecular interactions vary leading to changes in the quality (order and packing) of liposomes. So far it is not possible to image conformational disorders and packing densities within a liposome in a straightforward manner. In this study, we utilized confocal Raman microspectroscopy to visualize structural disorders and packingefficiency within a giant multilamellar liposome model by focusing mainly on three regions in the vibrational spectrum (C-C stretching, C-H deformation and C-H stretching). We estimated properties such as trans/gauche isomers and lateral packing probability. Interestingly, our Raman imaging studies revealed gel phase rich domains and heterogeneous lateral packing within the giant multilamellar liposome. (C) 2017 Elsevier B.V. All rights reserved.
Studying anti-oxidative properties of inclusion complexes of alpha-lipoic acid with gamma-cyclodextrin in single living fission yeast by confocal Raman microspectroscopy
(2018-05-15)
Noothalapati, Hemanth
;
Ikarashi, Ryo
;
Iwasaki, Keita
;
Nishida, Tatsuro
;
Kaino, Tomohiro
alpha-lipoic acid (ALA) is an essential cofactor for many enzyme complexes in aerobic metabolism, especially in mitochondria of eukaryotic cells where respiration takes place. It also has excellent anti-oxidative properties. The acid has two stereo-isomers, R- and S-lipoic acid (R-LA and S-LA), but only the R-LA has biological significance and is exclusively produced in our body. A mutant strain of fission yeast, Delta dpsl, cannot synthesize coenzyme Q10, which is essential during yeast respiration, leading to oxidative stress. Therefore, it shows growth delay in the minimal medium. We studied anti-oxidant properties of ALA in its free form and their inclusion complexes with gamma-cyclodextrin using this mutant yeast model. Both free forms R- and S-LA as well as 1:1 inclusion complexes with gamma-cyclodexhin recovered growth of Delta dps1 depending on the concentration and form. However, it has no effect on the growth of wild type fission yeast strain at all. Raman microspectroscopy was employed to understand the anti-oxidant property at the molecular level. A sensitive Raman band at 1602 cm(-1) was monitored with and without addition of ALAs. It was found that 0.5 mM and 1.0 mM concentrations of ALAs had similar effect in both free and inclusion forms. At 2.5 mM ALAs, free forms inhibited the growth while inclusion complexes helped in recovered. 5.0 mM ALA showed inhibitory effect irrespective of form. Our results suggest that the Raman band at 1602 cm(-1) is a good measure of oxidative stress in fission yeast. (C) 2018 Elsevier B.V. All rights reserved.