Zwitterion formation in hydrated amino acid, dipole bound anions: How many water molecules are required?

Xu, Shou‐Jun; Nilles, J. Michael; Bowen, Kit H.

doi:10.1063/1.1620501

Cited by 188 publications

(155 citation statements)

References 45 publications

Supporting

Mentioning

150

Contrasting

Order By: Relevance

“…The minimum number of water molecules required to stabilize a zwitterion of an amino acid has been predicted to range from 2 to 6 for glycine 49 and to be 2 or 4 for alanine. 10,21a According to a recent neutron diffraction study of aqueous alanine solutions, the total number of water molecules within the first hydration shell of an alanine molecule can be estimated to be roughly 8-9; 18a most of the water molecules (6-7 of the 8-9) hydrate charged groups.…”

Section: First Hydration Shellmentioning

confidence: 99%

l-Alanine in a Droplet of Water: A Density-Functional Molecular Dynamics Study

et al. 2007

View full text Add to dashboard Cite

We report the results of a Born-Oppenheimer molecular dynamics study on an L-alanine amino acid in neutral aqueous solution. The whole system, the L-alanine zwitterion and 50 water molecules, was treated quantum mechanically. We found that the hydrophobic side chain (R ) CH 3 ) defines the trajectory path of the molecule. Initially fully hydrated in an isolated droplet of water, the amino acid moves to the droplet's surface, exposing its hydrophobic methyl group and R-hydrogen out of the water. The structure of an L-alanine with the methyl group exposed to the water surface was found to be energetically favorable compared to a fully hydrated molecule. The dynamic behavior of the system suggests that the first hydration shell of the amino acid is localized around carboxylate (CO 2 -) and ammonium (NH 3 + ) functional groups; it is highly ordered and quite rigid. In contrast, the hydration shell around the side chain is much less structured, suggesting a modest influence of the methyl group on the structure of water. The number of water molecules in the first hydration shell of an alanine molecule is constantly changing; the average number was found to equal 7. The molecular dynamics results show that L-alanine in water does not have a preferred conformation, as all three of the molecule's functional sites (i.e., CH 3 , NH 3 + , CO 2 -) perform rotational movements around the C R -site bond.

show abstract

Section: First Hydration Shellmentioning

confidence: 99%

l-Alanine in a Droplet of Water: A Density-Functional Molecular Dynamics Study

et al. 2007

View full text Add to dashboard Cite

show abstract

“…Timeof-flight mass spectra of laser evaporated tryptophan measured by Simons and coworkers show the presence of an unusually stable Trp(H 2 O) 3 cluster which is suggested to be zwitterionic [54]. Recent photoelectron spectroscopy results of Bowen and coworkers indicate that four water molecules transform the dipole bound anion of both phenylalanine and tryptophan to their zwitterion form [55]. Five water molecules were found to be necessary for glycine [55].…”

mentioning

confidence: 99%

“…Recent photoelectron spectroscopy results of Bowen and coworkers indicate that four water molecules transform the dipole bound anion of both phenylalanine and tryptophan to their zwitterion form [55]. Five water molecules were found to be necessary for glycine [55].…”

mentioning

confidence: 99%

“…The effects of water on amino acid structure have been investigated using theory [48 -52], spectroscopy [52][53][54][55], and by blackbody infrared radiative dissociation (BIRD) [45,56,57]. Calculations indicate that two water molecules can make the zwitterion form of glycine a local minimum on the potential energy surface, but this structure is still ϳ12 kcal/mol higher in energy than the nonzwitterion [48].…”

mentioning

confidence: 99%

See 1 more Smart Citation

Binding energies of water to lithiated valine: Formation of solution-phase structure in vacuo

Lemoff

Williams

2004

J. Am. Soc. Mass Spectrom.

100

View full text Add to dashboard Cite

Dissociation kinetics for loss of a water molecule from hydrated ions of lithiated valine, alanine ethyl ester and betaine are determined using blackbody infrared radiative dissociation at temperatures between Ϫ60 and 110°C. From master equation modeling of these data, values of the threshold dissociation energy are obtained for clusters containing one through three water molecules. By comparing the values for valine with its two isomers, one a model for the nonzwitterion structure, the other a model for the zwitterion structure, information about the structure of valine in these hydrated clusters is inferred. Structures, relative energies, and water binding energies for these ions are also calculated at the B3LYP/6-31ϩϩG** level of theory. With one water molecule, both experiment and theory indicate that valine is not a zwitterion and that the lithium ion coordinates with the amino nitrogen and the carbonyl oxygen (NO coordinated) and the water molecule interacts directly with the lithium ion. With two water molecules, the zwitterion and nonzwitterion structures are nearly isoenergetic, but the experiment clearly indicates a NO-coordinated nonzwitterion structure. With three water molecules, both the experimental data and theory indicate that the lithium ion binds to the carboxylate group of valine, i.e., valine is zwitterionic with three water molecules. The agreement between the experimentally determined and calculated binding energies is good for all the clusters, with deviations of Յ 0.12 eV. M olecular structure in solution depends on both the intrinsic properties of the molecule and on the effects of the surrounding solvent molecules. Exclusion of water from the interior of proteins influences protein folding and conformation. Similarly, lipid bilayer formation is due to differences in water interaction with the polar and hydrophobic ends of the lipid molecules. Gas-phase experiments make possible investigation of the intrinsic properties of the molecule. Differences between gas-phase and solution-phase structure can be attributed to solvent effects. Studies of gas-phase peptides indicate that ␣-helices can be stable in the absence of water and indicate that the propensity for helix formation for some amino acids differs in the gas phase and in solution [1,2]. For example, peptides with high valine content have a higher helix-forming propensity than their alanine analogues in the gas phase, but just the opposite is observed in aqueous solution [1].In the condensed phase, specific water molecules can play an important role in molecular structure. Such specific water molecules are often observed in crystal structures of proteins and other molecules. Evidence for specific water has been reported by Jarrold and coworkers for the molecule BPTI which tightly binds one water molecule in the gas phase [3,4]. Magic hydration numbers for gramicidin S at 8, 11, and 14 water molecules suggest stable solvation shells around the doubly protonated gas-phase ion [5], while a magic hydration number of 40 water molecules h...

show abstract

“…Amino acid monomers have the added kinetic disadvantage of existing primarily as zwitterions at environmentally and physiologically relevant pH values in bulk aqueous solution (5,7). Insightful experiments have been performed, yielding peptide bonds in anhydrous solvents with amino acid ester starting materials and copper(II) ion catalysis (8,9).…”

mentioning

confidence: 99%

In situ observation of peptide bond formation at the water–air interface

Griffith

Vaida

2012

Proc. Natl. Acad. Sci. U.S.A.

146

155

View full text Add to dashboard Cite

We report unambiguous spectroscopic evidence of peptide bond formation at the air-water interface, yielding a possible mechanism providing insight into the formation of modern ribosomal peptide bonds, and a means for the emergence of peptides on early Earth. Protein synthesis in aqueous environments, facilitated by sequential amino acid condensation forming peptides, is a ubiquitous process in modern biology, and a fundamental reaction necessary in prebiotic chemistry. Such reactions, however, are condensation reactions, requiring the elimination of a water molecule for every peptide bond formed, and are thus unfavorable in aqueous environments both from a thermodynamic and kinetic point of view. We use the hydrophobic environment of the air-water interface as a favorable venue for peptide bond synthesis, and demonstrate the occurrence of this chemistry with in situ techniques using Langmuir-trough methods and infrared reflection absorption spectroscopy. Leucine ethyl ester (a small amino acid ester) first partitions to the water surface, then coordinates with Cu 2þ ions at the interface, and subsequently undergoes a condensation reaction selectively forming peptide bonds at the air-water interface.

show abstract

Zwitterion formation in hydrated amino acid, dipole bound anions: How many water molecules are required?

Cited by 188 publications

References 45 publications

l-Alanine in a Droplet of Water: A Density-Functional Molecular Dynamics Study

l-Alanine in a Droplet of Water: A Density-Functional Molecular Dynamics Study

Binding energies of water to lithiated valine: Formation of solution-phase structure in vacuo

In situ observation of peptide bond formation at the water–air interface

Contact Info

Product

Resources

About