Experimental Evidence of Slow Mode Water in the Vicinity of Poly(ethylene oxide) at Physiological Temperature

Tominaga, Taiki; Hishida, Mafumi; Murakami, Daiki; Fujii, Yoshihisa; Tanaka, Masaru; Seto, Hideki

doi:10.1021/acs.jpcb.1c09044

Cited by 16 publications

(32 citation statements)

References 45 publications

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“…One is that the relationship between the information obtained using various methods to observe hydration is unclear. Hydration can be observed by focusing on various physical properties using methods such as thermal measurements, ,, nuclear magnetic resonance (NMR) spectroscopy, ,, neutron scattering, ,,, dielectric relaxation spectroscopy, ,, terahertz spectroscopy, ,,,− and infrared spectroscopy. ,, However, because the physical quantities observed by these methods are essentially different, whether the observed hydration water is the same and the relationship between the physical quantities is unclear. Therefore, basic information such as the number of hydration water varies widely between reports, making it difficult to obtain a complete picture.…”

Section: Introductionmentioning

confidence: 99%

Contrasting Changes in Strongly and Weakly Bound Hydration Water of a Protein upon Denaturation

et al. 2023

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Water is considered integral for the stabilization and function of proteins, which has recently attracted significant attention. However, the microscopic aspects of water ranging up to the second hydration shell, including strongly and weakly bound water at the sub-nanometer scale, are not yet well understood. Here, we combined terahertz spectroscopy, thermal measurements, and infrared spectroscopy to clarify how the strongly and weakly bound hydration water changes upon protein denaturation. With denaturation, that is, the exposure of hydrophobic groups in water and entanglement of hydrophilic groups, the number of strongly bound hydration water decreased, while the number of weakly bound hydration water increased. Even though the constraint of water due to hydrophobic hydration is weak, it extends to the second hydration shell as it is caused by the strengthening of hydrogen bonds between water molecules, which is likely the key microscopic mechanism for the destabilization of the native state due to hydration.

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Section: Introductionmentioning

confidence: 99%

Contrasting Changes in Strongly and Weakly Bound Hydration Water of a Protein upon Denaturation

et al. 2023

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“…30,31 For example, neutron scattering revealed that linear PEG has a small amount of strongly bound water and a large amount of weakly bound water, and the results of THz-TDS are well coincident with the total amount of strongly and weakly bound water, which ranges about 2.1 water molecules per ethylene glycol unit. 31 Therefore, by using this method, a change in the hydration state due to dehydration is expected to be clearly observed. In fact, the dehydration of PNIPAAm at the cloud point has been reported by dielectric relaxation in the GHz range, 14 suggesting that weakly bound water is involved in dehydration at the cloud point.…”

Section: ■ Introductionmentioning

confidence: 89%

Hydration State on Poly(ethylene glycol)-Bearing Homopolymers and Random Copolymer Micelles: In Relation to the Thermoresponsive Property and Micellar Structure

Hishida,

Kanno,

Terashima

2023

Macromolecules

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Poly(ethylene glycol) (PEG)-bearing (co)polymers often show lower critical solution temperature-type solubility in water; the aqueous solution becomes clouded and/or phase-separated upon heating to a certain temperature (cloud-point temperature). In general, it has been interpreted that the thermoresponsive properties of (co)polymers in water originate from the dehydration of the polymer chains, whereas the hydration state of these polymers has not yet been evaluated. Herein, we report the amount of hydration water on PEG-bearing homopolymers and random copolymer micelles in water, analyzed by terahertz time-domain spectroscopy, and micellar structures (molecular packing in the hydrophilic layer) determined by small-angle X-ray scattering. Systematic investigation by changing the ratio of PEG side chains and alkyl side chains revealed a clear correlation between the thermoresponsive properties, molecular and micellar structures, and the amount of hydration water. The random copolymers induce self-folding or intermolecular self-assembly to form unimer or multichain micelles in water; the size of the micelles increases with an increasing number of hydrophobic monomer units. As the micelle size increases, the PEG chains tend to be densely packed in the hydrophilic shell layers, leading to a reduction in the amount of hydration water per ethylene glycol unit of PEG. Thus, the dehydration of the PEG chain likely becomes easier, and the cloud-point temperatures decrease with increasing hydrophobic monomer content.

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“…Another study that took advantage of the overlap of the time scales of these experimental techniques was performed by Tominaga et al [ 23 ]. They evaluated the kind of water existing on a biocompatible polymer, poly(ethylene oxide).…”

Section: Applications By Combined Analysismentioning

confidence: 99%

“…This review will introduce the differences between the information obtained from INS and THz-TDS, as well as the advantages and disadvantages of each and the experimental practical aspects, and emphasize the merits of the combined analysis of both methods. A few biomolecular analyses combining both methods will be presented [ 17 , 23 ]. The combined analysis of INS and THz-TDS will be very useful for analyzing the dynamics of biomolecules and hydration water.…”

Section: Introductionmentioning

confidence: 99%

Incoherent Neutron Scattering and Terahertz Time-Domain Spectroscopy on Protein and Hydration Water

Yamamoto

2023

Life

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Incoherent inelastic and quasi-elastic neutron scattering (INS) and terahertz time-domain spectroscopy (THz-TDS) are spectroscopy methods that directly detect molecular dynamics, with an overlap in the measured energy regions of each method. Due to the different characteristics of their probes (i.e., neutron and light), the information obtained and the sample conditions suitable for each method differ. In this review, we introduce the differences in the quantum beam properties of the two methods and their associated advantages and disadvantages in molecular spectroscopy. Neutrons are scattered via interaction with nuclei; one characteristic of neutron scattering is a large incoherent scattering cross-section of a hydrogen atom. INS records the auto-correlation functions of atomic positions. By using the difference in neutron scattering cross-sections of isotopes in multi-component systems, some molecules can be selectively observed. In contrast, THz-TDS observes the cross-correlation function of dipole moments. In water-containing biomolecular samples, the absorption of water molecules is particularly large. While INS requires large-scale experimental facilities, such as accelerators and nuclear reactors, THz-TDS can be performed at the laboratory level. In the analysis of water molecule dynamics, INS is primarily sensitive to translational diffusion motion, while THz-TDS observes rotational motion in the spectrum. The two techniques are complementary in many respects, and a combination of the two is very useful in analyzing the dynamics of biomolecules and hydration water.

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Experimental Evidence of Slow Mode Water in the Vicinity of Poly(ethylene oxide) at Physiological Temperature

Cited by 16 publications

References 45 publications

Contrasting Changes in Strongly and Weakly Bound Hydration Water of a Protein upon Denaturation

Contrasting Changes in Strongly and Weakly Bound Hydration Water of a Protein upon Denaturation

Hydration State on Poly(ethylene glycol)-Bearing Homopolymers and Random Copolymer Micelles: In Relation to the Thermoresponsive Property and Micellar Structure

Incoherent Neutron Scattering and Terahertz Time-Domain Spectroscopy on Protein and Hydration Water

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