Raman Spectroscopic Signatures of Noncovalent Interactions Involving Trimethylamine N-oxide (TMAO)

Munroe, Katherine L.; Magers, David H.; Hammer, Nathan I.; Champion, P. M.; Ziegler, L. D.

doi:10.1063/1.3482852

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“…The properties of hydrogen bonds within the solutions in the simulations were also examined. The average number of hydrogen bonds with water for each TMAO is about three, which agrees with the results from experiment 14,15 and ab initio calculations. 16,17 The lifetimes extrapolated at infinite dilution of TMAO-water hydrogen bonds (~30 ps) are much longer than water-water hydrogen bonds in pure water (3.46 ps), whereas the hydrogen bonds from the urea oxygen to water (~4 ps) and from the urea nitrogen to water (~1.5 ps) are on a similar timescale.…”

Section: Resultssupporting

confidence: 89%

“…13 Evidence indicates that the interactions between TMAO and water are very strong. A TMAO molecule forms hydrogen bonds with ~3 water molecules according to dielectric spectroscopy, 14 Raman spectroscopy, 15 and ab initio molecular dynamics (AIMD) simulations, 16,17 which have a much longer lifetime than typical hydrogen bonds between polar species based on dielectric spectroscopy 18 and AIMD simulations. [19][20][21] Moreover, the counteraction by TMAO of the denaturing effects of urea is even more debated.…”

Section: Introductionmentioning

confidence: 99%

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Dynamical Effects of Trimethylamine N-Oxide on Aqueous Solutions of Urea

Teng

Ichiye

2019

J. Phys. Chem. B

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Trimethylamine N-oxide (TMAO) stabilizes protein structures, whereas urea destabilizes proteins, and their opposing effects can be counteracted at a 1:2 ratio of TMAO to urea. To investigate how they affect solution dynamics, molecular dynamics simulations have been carried out for aqueous solutions of TMAO and urea at different concentrations. In the binary solutions, urea mainly slows the diffusion of waters that are hydrogen bonded to it (i.e., hydration water), whereas TMAO dramatically slows the diffusion of both hydration water and bulk water because of long-lived TMAO-water hydrogen bonds. In the ternary solutions, because TMAO decreases the diffusion rate of bulk water, the lifetimes of not only water-water but also urea-water hydrogen bonds increase. In addition, the constant forming and breaking of short lifetime hydrogen bonds between urea and water appears to impart energy into the bulk, whereas the long lifetime hydrogen bonds between TMAO and water slows down the bulk, resulting in the compensating effects on bulk water in the ternary solution. This suggests that the counteracting effects of TMAO on urea denaturation may be both to make longer lived hydrogen bonds to water and to counter the energizing effects of urea on bulk water.

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Section: Resultssupporting

confidence: 89%