Vibrational absorption and vibrational circular dichroism spectra of leucine in water under different pH conditions: Hydrogen-bonding interactions with water

Poopari, Mohammad Reza; Zhu, Peiyan; Dezhahang, Zahra; Xu, Yunjie

doi:10.1063/1.4767401

Cited by 33 publications

(27 citation statements)

References 25 publications

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“…Scheme 9 (S)-2-amino -4-methylpentanoic acid VCD and ROA: Experiment and Calculations the vCd C*h stretching and bending vibration bands of L-leucine in water were observed in early studies by the Nafie group [147,149]. Since then, no report on L-leucine vCd spectra was made until the very recent study performed by the Xu group [215][216][217]. the IR spectra of L-leucine in h 2 o and d 2 o were recorded under three representative ph conditions (1.0, 6.4, and 13); however, because of the poor solubility of L-leucine in strongly acidic or basic solutions, the vCd spectra were taken only at near-neutral ph/pd.…”

Section: L-serinementioning

confidence: 97%

α-Amino Acids In Water: A Review Of VCD And ROA Spectra

Dobrowolski

Lipiński

Rode

et al. 2013

Challenges and Advances in Computational Chemistry and Physics

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An up-to-date perspective on the capability of vibrational Circular dichroism (vCd) and Raman optical Activity (RoA) spectroscopy of the 20 encoded α-amino acids to solve the structural problems appearing in water is provided in this review. VCD and ROA spectroscopy of the α-amino acid molecules reviewed in this chapter refer only to free and single amino acids in water at various ph levels. to well understand the implications of such studies for biology and medicine, we devote one subchapter to the role of free amino acids in an organism's metabolism and physiology. A variety of side chains that modify the α-amino acids character from acidic to basic and from hydrophilic to hydrophobic makes the possible dissociation equilibria in water very complex and dependent on several factors. therefore, information on dissociation constants, isoelectric points, and hydrophobicity parameters of α-amino acids is summarised in the next subchapter. The conformational variety, complexity of interactions, and entanglement of equilibria makes considering the influence of these factors on vCd and RoA spectra with quantum chemical analysis absolutely necessary. the elements of the theory of chiroptical vibrational spectra and methods enabling solvent simulations are provided in the subsequent subchapter. We report on experimental methods, techniques and tricks for measuring and simulating the vCd and RoA spectra in water at different ph levels. the review is concluded by listing the not-yet-measured amino acids, a presentation of the main challenges for computational methods, and suggestions for the most promising experimental techniques that may be used in future studies. Keywords

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Section: L-serinementioning

confidence: 97%

α-Amino Acids In Water: A Review Of VCD And ROA Spectra

Dobrowolski

Lipiński

Rode

et al. 2013

Challenges and Advances in Computational Chemistry and Physics

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“…In these studies, it became quite clear that one must also take the bulk water solvent environment into account in order to reproduce the experimentally observed IR and VCD spectra. One amino acid studied under different pH condition is leucine (Poopari et al, 2012b ). Leucine exists in three dominant species, i.e., the protonated, zwitterionic, and deprotonated forms, under three representative pH conditions of 1, 6, and 13, respectively.…”

Section: Water Solvationmentioning

confidence: 99%

Section: Water Solvationmentioning

confidence: 99%

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The Clusters-in-a-Liquid Approach for Solvation: New Insights from the Conformer Specific Gas Phase Spectroscopy and Vibrational Optical Activity Spectroscopy

et al. 2016

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Vibrational optical activity spectroscopies, namely vibrational circular dichroism (VCD) and Raman optical activity (ROA), have been emerged in the past decade as powerful spectroscopic tools for stereochemical information of a wide range of chiral compounds in solution directly. More recently, their applications in unveiling solvent effects, especially those associated with water solvent, have been explored. In this review article, we first select a few examples to demonstrate the unique sensitivity of VCD spectral signatures to both bulk solvent effects and explicit hydrogen-bonding interactions in solution. Second, we discuss the induced solvent chirality, or chiral transfer, VCD spectral features observed in the water bending band region in detail. From these chirality transfer spectral data, the related conformer specific gas phase spectroscopic studies of small chiral hydration clusters, and the associated matrix isolation VCD experiments of hydrogen-bonded complexes in cold rare gas matrices, a general picture of solvation in aqueous solution emerges. In such an aqueous solution, some small chiral hydration clusters, rather than the chiral solutes themselves, are the dominant species and are the ones that contribute mainly to the experimentally observed VCD features. We then review a series of VCD studies of amino acids and their derivatives in aqueous solution under different pHs to emphasize the importance of the inclusion of the bulk solvent effects. These experimental data and the associated theoretical analyses are the foundation for the proposed “clusters-in-a-liquid” approach to account for solvent effects effectively. We present several approaches to identify and build such representative chiral hydration clusters. Recent studies which applied molecular dynamics simulations and the subsequent snapshot averaging approach to generate the ROA, VCD, electronic CD, and optical rotatory dispersion spectra are also reviewed. Challenges associated with the molecular dynamics snapshot approach are discussed and the successes of the seemingly random “ad hoc explicit solvation” reported before are also explained. To further test and improve the “clusters-in-a-liquid” model in practice, future work in terms of conformer specific gas phase spectroscopy of sequential solvation of a chiral solute, matrix isolation VCD measurements of small chiral hydration clusters, and more sophisticated models for the bulk solvent effects would be highly valuable.

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“…[36][37][38][39][40] These studies involved simulations of small molecules in water to account for solvent effects. After the simulation, the coordinates of the molecule(s) are exported at regular time intervals called snapshots.…”

Section: Introductionmentioning

confidence: 99%

Concentration Dependent Specific Rotations of Chiral Surfactants: Experimental and Computational Studies

Covington

Polavarapu

2016

J. Phys. Chem. A

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Recent experimental studies have shown unexpected chiroptical response from some chiral surfactant molecules, where the specific rotations changed significantly as a function of concentration. To establish a theoretical understanding of this experimentally observed phenomena, a novel methodology for studying chiral surfactants via combined molecular dynamics (MD) and quantum mechanical (QM) calculations is presented. MD simulations on the +10 000 atom surfactant systems have been performed using MD and QM/molecular mechanics (MM) approaches. QM calculations performed on MD snapshots coupled with extensive analysis on lauryl ester of phenylalanine (LEP) surfactant system indicate that the experimentally observed variation of specific rotation with concentration may be due to the conformational differences of the surfactant monomers in the aggregates. Though traditional MM simulations did not show significant differences in the conformer populations, QM/MM simulations using the forces derived from the PM6 method did predict conformational differences between aggregated and nonaggregated LEP molecules, which is consistent with experimental data. Additionally the electrostatic environment of charged surfactants may also be important, since dramatic changes in the Boltzmann populations of surfactant monomers can be noted in the presence of an electric field generated by the chiral ionic aggregates.

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Vibrational absorption and vibrational circular dichroism spectra of leucine in water under different pH conditions: Hydrogen-bonding interactions with water

Cited by 33 publications

References 25 publications

α-Amino Acids In Water: A Review Of VCD And ROA Spectra

α-Amino Acids In Water: A Review Of VCD And ROA Spectra

The Clusters-in-a-Liquid Approach for Solvation: New Insights from the Conformer Specific Gas Phase Spectroscopy and Vibrational Optical Activity Spectroscopy

Concentration Dependent Specific Rotations of Chiral Surfactants: Experimental and Computational Studies

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