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Thermal Behavior of Water in Sephadex(®) G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry

Water in a crosslinked dextran gel, Sephadex(®) G25, is known to remain partially unfrozen during cooling and undergoes ice crystallization during rewarming. However, the mechanism of ice crystallization during rewarming is still unclear. To elucidate the frozen state of water in the gel, thermal be...

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Autores principales: Onoda-Yamamuro, Noriko, Minato, Hiroaki, Nakayama, Eiji, Murase, Norio
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10010326/
https://www.ncbi.nlm.nih.gov/pubmed/36826296
http://dx.doi.org/10.3390/gels9020126
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author Onoda-Yamamuro, Noriko
Minato, Hiroaki
Nakayama, Eiji
Murase, Norio
author_facet Onoda-Yamamuro, Noriko
Minato, Hiroaki
Nakayama, Eiji
Murase, Norio
author_sort Onoda-Yamamuro, Noriko
collection PubMed
description Water in a crosslinked dextran gel, Sephadex(®) G25, is known to remain partially unfrozen during cooling and undergoes ice crystallization during rewarming. However, the mechanism of ice crystallization during rewarming is still unclear. To elucidate the frozen state of water in the gel, thermal behavior at low temperatures was investigated by using adiabatic calorimetry. Heat capacities and enthalpy-relaxation rates of the gel-containing water of mass ratio h (=g H(2)O/g dry G25) = 1.00 were measured between 80 and 300 K during rewarming, where the gel was intermittently heated at the rate of 50–100 mK min(−1). Although an exotherm indicating ice crystallization during rewarming was confirmed with the gel precooled rapidly, at 5 K min(−1), it disappeared when precooled slowly, at 20 mK min(−1). During rewarming after the rapid cooling, two glass transitions were observed at ca. 175 K and 240–242 K. A higher-temperature glass transition due to the water trapped by the polymer network was not so clear, as it was overlapped with an endotherm due to the melting of small ice crystals, which indicates that the ice crystals formed have a broad size-distribution and that water in the gel is vitrified when ice crystals of even the smallest size cannot be formed.
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spelling pubmed-100103262023-03-14 Thermal Behavior of Water in Sephadex(®) G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry Onoda-Yamamuro, Noriko Minato, Hiroaki Nakayama, Eiji Murase, Norio Gels Article Water in a crosslinked dextran gel, Sephadex(®) G25, is known to remain partially unfrozen during cooling and undergoes ice crystallization during rewarming. However, the mechanism of ice crystallization during rewarming is still unclear. To elucidate the frozen state of water in the gel, thermal behavior at low temperatures was investigated by using adiabatic calorimetry. Heat capacities and enthalpy-relaxation rates of the gel-containing water of mass ratio h (=g H(2)O/g dry G25) = 1.00 were measured between 80 and 300 K during rewarming, where the gel was intermittently heated at the rate of 50–100 mK min(−1). Although an exotherm indicating ice crystallization during rewarming was confirmed with the gel precooled rapidly, at 5 K min(−1), it disappeared when precooled slowly, at 20 mK min(−1). During rewarming after the rapid cooling, two glass transitions were observed at ca. 175 K and 240–242 K. A higher-temperature glass transition due to the water trapped by the polymer network was not so clear, as it was overlapped with an endotherm due to the melting of small ice crystals, which indicates that the ice crystals formed have a broad size-distribution and that water in the gel is vitrified when ice crystals of even the smallest size cannot be formed. MDPI 2023-02-02 /pmc/articles/PMC10010326/ /pubmed/36826296 http://dx.doi.org/10.3390/gels9020126 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Onoda-Yamamuro, Noriko
Minato, Hiroaki
Nakayama, Eiji
Murase, Norio
Thermal Behavior of Water in Sephadex(®) G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry
title Thermal Behavior of Water in Sephadex(®) G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry
title_full Thermal Behavior of Water in Sephadex(®) G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry
title_fullStr Thermal Behavior of Water in Sephadex(®) G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry
title_full_unstemmed Thermal Behavior of Water in Sephadex(®) G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry
title_short Thermal Behavior of Water in Sephadex(®) G25 Gels at Low Temperatures Studied by Adiabatic Calorimetry
title_sort thermal behavior of water in sephadex(®) g25 gels at low temperatures studied by adiabatic calorimetry
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10010326/
https://www.ncbi.nlm.nih.gov/pubmed/36826296
http://dx.doi.org/10.3390/gels9020126
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