Observation of salt effects on hydration water of lysozyme in aqueous solution using terahertz time-domain spectroscopy

Aoki, Katsuyoshi; Shiraki, Kentaro; Hattori, Toshiaki

doi:10.1063/1.4826699

Cited by 20 publications

(27 citation statements)

References 31 publications

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“…From the obtained waveforms, the refractive index, n, and the absorption coefficient, α, of the sample solutions were obtained as previously reported. 45 3 Results the lysozyme aqueous solution were smaller than that of pure water. This is caused by two effects: exclusion of water by the lysozyme molecules, and slowing down of the dynamics of water around the lysozyme.…”

Section: Methodsmentioning

confidence: 97%

“…Hen egg white lysozyme (L6876, Sigma-Aldrich, USA) was used as a model protein, which has a large pI value (11.35) The absorption coefficient spectra of the sample solutions were measured using a THz-TDS setup and a sample cell that were previously reported by the authors. 45 To avoid the effects of water vapor in the air, the path of the terahertz waves was purged with nitrogen gas and the relative humidity was reduced. All the measurements were carried out at a temperature of 19.5 ± 1.0 • C and a relative humidity of < 5.0 %.…”

Section: Methodsmentioning

confidence: 99%

“…Previously, we investigated the effect of ammonium sulfate on lysozyme hydration water using THz-TDS. 45 Hen egg white lysozyme (14307 Da, pI = 11.35) was used as a model protein. In this report, effects of specific salts on protein hydration were investigated under the conditions of pH < pI, using THz-TDS.…”

Section: Introductionmentioning

confidence: 99%

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Salt effects on the picosecond dynamics of lysozyme hydration water investigated by terahertz time-domain spectroscopy and an insight into the Hofmeister series for protein stability and solubility

Aoki

Shiraki

Hattori

2016

Phys. Chem. Chem. Phys.

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The addition of salts into protein aqueous solutions causes changes in protein solubility and stability, whose ability is known to be ordered in the Hofmeister series. We investigated the effects of Hofmeister salts on the picosecond dynamics of water around a lysozyme molecule using terahertz time-domain spectroscopy. The change in the absorption coefficient for 200 mg mL(-1) lysozyme aqueous solution by the addition of salts was found to depend on the salts used, whereas that for pure water was almost independent of salts. From the difference in the salt concentration dependence for various salts, it has been found that chaotropic anions make the dynamics of water around the lysozyme molecule slower, whereas kosmotropic anions make the dynamics faster. The ability of an anion to slow down the water dynamics was found to have the following order: SCN(-) > Cl(-) > H2PO4(-) > NO3(-) ≈ SO4(2-). This result indicates that the effects of anions on the dynamics of water around the lysozyme molecule are the opposite of those for bulk water. This finding agrees with a prediction from a molecular model proposed by Collins [K. D. Collins, Methods, 2004, 34, 300]. The results presented here are compared with the results from preferential interaction studies and the results from sum frequency generation spectroscopy. These discussions have led to the conclusion that the picosecond dynamics of protein hydration water strongly contributes to protein stability, whereas electrostatic interactions between protein molecules contribute to protein solubility.

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Section: Methodsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

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Salt effects on the picosecond dynamics of lysozyme hydration water investigated by terahertz time-domain spectroscopy and an insight into the Hofmeister series for protein stability and solubility

Aoki

Shiraki

Hattori

2016

Phys. Chem. Chem. Phys.

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“…In this study, terahertz waves were generated by irradiating a (111) p-type InAs wafer (carrier density: 2-4 x 10 17 cm -3 ) by 800 nm mode-locked Ti:sapphire laser pulses [2,3]. The incident angle of the laser light was 45º.…”

Section: Methodsmentioning

confidence: 99%

Improving a Terahertz Time-Domain Spectroscopy Apparatus Using Neodymium Magnets

Yano

Hattori

2015

ILCPA

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The signal-to-noise ratio obtained from terahertz time-domain spectroscopy is significantly affected by the low available power of terahertz waves. We constructed a terahertz-wave source with emission power enhanced by a magnetic field. The emitter is composed of an InAs wafer and two neodymium magnets. The emitter was irradiated by femtosecond laser pulses. The data quality of terahertz spectroscopic measurements was evaluated, and reduction of error in the data obtained due to the terahertz power enhancement was observed.

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“…Results of hydration study of protein (hen egg white lysozyme) aqueous solution with several ammonium salts [1,2] is briefly described below. Terahertz absorption coefficient of the protein-salt aqueous solutions and salt aqueous solutions were obtained as a function of the salt concentration.…”

Section: Introductionmentioning

confidence: 99%

Hydration of various solutions observed by terahertz spectroscopy

Hattori¹

2017

Proceedings of the Nano-Micro Conference 2017

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Use of terahertz waves for sensing various type of materials has been an important subject of research. The target materials include biological tissues, various kind of liquids, industrial products, etc. In most of cases, water is the most important absorber of terahertz waves. It is crucial, therefore, to understand the terahertz absorption properties of water in various situations.It is known that the terahertz absorption of water is strongly affected by the interaction with other molecules in solutions, gels, crystals, or other types of phases. In aqueous solutions, for example, the solute is stabilized by the interaction with surrounding water molecules, and the water molecules incorporated in this interaction are very often strongly bound to the solute, leading to reduced mobility and reduced terahertz absorption.We have constructed a high-precision terahertz time-domain spectroscopy apparatus for hydration study. Results of hydration study of protein (hen egg white lysozyme) aqueous solution with several ammonium salts [1,2] is briefly described below. Terahertz absorption coefficient of the protein-salt aqueous solutions and salt aqueous solutions were obtained as a function of the salt concentration. The difference between the results of protein-salt aqueous solutions and those of salt aqueous solutions exhibits the nature of the hydration water of the protein and also the effect of salt on them. It was found that the hydration layer of the protein is affected by ions (mostly anions) added to the solution, and that so-called kosmotropic ions (structure makers), such as sulfate ion, reduce the amount of immobile hydration water, whereas chaotropic ions (structure breakers), such as thiocyanate ions, increase it. It is shown that the dynamical properties of hydration water molecules is correlated with the stability of the macromolecules, whereas their density with the solubility.Measurements on other types of water-rich systems have shown that the mobility of water sometimes increases after hydration, or that the hydration number changes drastically upon a small change in the concentration. Study of hydration using terahertz waves is expected to produce fruitful results in various fields including solution chemistry, sol-gel science, biology, and medicine.

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Observation of salt effects on hydration water of lysozyme in aqueous solution using terahertz time-domain spectroscopy

Cited by 20 publications

References 31 publications

Salt effects on the picosecond dynamics of lysozyme hydration water investigated by terahertz time-domain spectroscopy and an insight into the Hofmeister series for protein stability and solubility

Salt effects on the picosecond dynamics of lysozyme hydration water investigated by terahertz time-domain spectroscopy and an insight into the Hofmeister series for protein stability and solubility

Improving a Terahertz Time-Domain Spectroscopy Apparatus Using Neodymium Magnets

Hydration of various solutions observed by terahertz spectroscopy

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