The pH-dependence of preferential solvation as studied by intermolecular homo- and heteronuclear NOE measurements of adenosine in water?trifluoroethanol mixtures

Abstract

A study of the state of solvation of the adenine ring in adenosine and adenosine 5'-monophosphate disodium salt in water and in a (7.5:2.5) water-TFE mixture has been carried out by measurement of homo- and heteronuclear intermolecular NOE enhancements between water or TFE and the aromatic protons of these compounds. The results give evidence of site specificity in solute-solvent interaction for both solvent systems and preferential solvation of the solute by TFE in the water-TFE mixture. Significant pH dependence of these interactions has been discovered.

Weak Interactions between Folate and Osmolytes in Solution

“…However, both betaine and DMSO do preferentially solvate aromatic systems because the NOEs arising from the aromatic protons in NADPH decreased or, in the case of the nicotinamide ring, were completely eliminated, in the presence of either osmolyte. Reports showing intermolecular NOEs between the aromatic protons of adenosine and trifluoroethanol in a mixture with water, or in neat DMSO, indicate that osmolytes can preferentially solvate aromatic systems like adenine and nicotinamide rings. Additionally, our osmotic stress experiments suggest that sucrose interacts more strongly with P6C than water.…”

Solvation Structures of Tetraethylammonium Bromide and Tetrafluoroborate in Aqueous Binary Solvents with Ethanol, Trifluoroethanol, and Acetonitrile

“…In addition, the fluorinated alcohol of TFE has been known as a strong promotor of the secondary structure of peptides and proteins, such as α-helix and β-sheet, in aqueous solutions, − probably due to the C–H···F–C weak hydrogen bond. − It has not been known whether the weak hydrogen bond affects the hydrophobic groups of the highly charged species, such as TEA + . The promotion of the secondary structure of peptides and proteins and the mechanisms of biochemical reactions in a living cell, such as liquid–liquid phase separation, − are governed by the complexly tangled hydrophilic, hydrophobic, and electrostatic interactions.…”

A Study of the Solvation Structure of l‐Leucine in Alcohol–Water Binary Solvents through Molecular Dynamics Simulations and FTIR and NMR Spectroscopy

“…The interactions of the hydrophobic moieties of peptides and proteins with fluorinated alcohols have been independently studied by through the 1 H- 19 Fn uclear Overhauser effect by the groups of Berger [21][22][23] and Gerig [24][25][26] The NOE studies showedt he interactions between the hydrophobic groups and fluorinated alcohol molecules. The TFE fluoroalkyl group strongly interacts with the hydrophobic moieties of the peptides, whereas the interactions between EtOH and the hydrophobic moieties of the peptides are weak.…”

“…[40][41][42] In particular,b lue-shifting hydrogen bonds have not been observed in the promotion of the secondary structure of biomolecules by TFE and HFIP at the microscopic level, despite the NOE observation of the interactions between the hydrophobic moieties of biomolecules and fluorinated alcohols. [21][22][23][24][25][26] We aimed to clarifyt he solvation structure of the amino acid Leu in aliphatic-alcohol-water andf luorinated-alcohol-water solvents as the first stage of our investigations, because the structures of proteins and peptides are too complex to extract the interactions between their hydrophobic moiety and alcohol molecules by using spectroscopic techniques. The alcohols used include MeOH,E tOH, 2-PrOH, TFE, and HFIP.T he structure of the Leu molecule is depicted in Figure 1w ith the notation of the hydrogen and carbon atoms.I naneutrala queous solution, the carboxylg roup (COOH)o fL eu is deprotonated to form the carboxylate group (COO À ), whereas the Leu amino group (NH 2 )i sp rotonated to form the aminium group (NH 3 + ), because the pK a1 and pK a2 are 2.33 and 9.74, respectively.…”