Key Differences of the Hydrate Shell Structures of ATP and Mg·ATP Revealed by Terahertz Time-Domain Spectroscopy and Dynamic Light Scattering

Abstract

ATP is one of the main biological molecules. Many of its biological and physicochemical properties, such as energy capacity of the phosphate bonds, significantly depend on hydration. However, the structure of the hydration shell of the ATP molecule is still a matter of discussion. In this work, the hydration shells of ATP in water and MgCl 2 solutions were examined by terahertz time-domain spectroscopy and dynamic light scattering. Terahertz spectroscopy reveals the distorted water structure in the ATP water solution displaying tightly bound water molecules, which could be explained by the hydration of phosphate groups. Upon ATP binding to a Mg 2+ ion, the situation is principally different: Instead of the distorted water structure, its arranged structure with increased hydrogen bond number is observed. Dynamic light scattering showed that the hydrodynamic diameter of ATP increases by 0.5 nm after Mg 2+ binding. Meanwhile, according the characteristics of scattering, the increase of the shell size occurs via formation of a layer with a refraction coefficient similar to water. This layer can be interpreted as hydration shell differing from unaltered water by increased number of hydrogen bonds.

Hydration Shells of DNA from the Point of View of Terahertz Time-Domain Spectroscopy

“…Since the concentration of water molecules in the compared solutions is almost identical, a conclusion on the presence of a higher number of hydrogen bonds in the DNA hydration shells compared to undisturbed water can be drawn. An analogous result was obtained earlier in the work [ 30 ] on hydration shells of ATP molecules. We should note that the average number of hydrogen bonds with a water molecule in pure water at 25 °C comprises 3.6 of a possible 4 [ 45 ].…”

“…It is interesting to analyze the discussed regularities for DNA solutions compared to the ATP solution. An investigation devoted to studying the hydration shells of ATP by THz-TDS [ 30 ] demonstrated that the effect of ATP and Mg·ATP complex on water can be reduced to the decrease of Δ ε 1 and increase of Δ ε 2 and A/ ω 2 . Similar changes of the same parameters are also observed in the current work for DNA.…”

“…Similar changes of the same parameters are also observed in the current work for DNA. Let us compare quantitative changes of three parameters occurring under the action of DNA ( Table 1 ) and ATP [ 30 ] in a 40 mM MgCl 2 solution. For DNA, Δ ε 1 is decreased 3.1 stronger, while Δ ε 2 is increased 3.6 times stronger, A/ ω 2 is increased 1.4 times stronger, compared to ATP, when normalized by molar concentration of nucleotides.…”

“…To obtain informative data on hydration shells, high-precision spectral measurement and specific approaches to data processing are required. In some of our works, the THz-TDS method has already been applied to study electrolyte solutions [ 27 ], protein hydration shells [ 28 ], liposomes [ 29 ], and ATP [ 30 ]. This work is the next step in this series of research articles, and it is focused on THz-TDS application to DNA solutions.…”

Relationships between Molecular Structure of Carbohydrates and Their Dynamic Hydration Shells Revealed by Terahertz Time-Domain Spectroscopy

“…This is due to the specifications of the THz spectral range corresponding to the intermolecular organization of water according to the specific times and energies. This is the only method sensitive to so-called dynamic hydration shells [ 42 , 45 , 56 , 57 , 58 ], which includes not just strongly bound water molecules in the primary layer, but also more distant molecules with slightly altered dynamics. In the case of aqueous sugar solutions, it is obviously confirmed by the fact that with increasing concentrations, the hydration number decreases starting from quite low concentrations, 0.15–0.3 M by monosaccharides [ 39 , 41 , 55 ].…”