Progressive Stabilization of Zwitterionic Structures in [H(Ser)<sub>2–8</sub>]<sup>+</sup> Studied by Infrared Photodissociation Spectroscopy

Kong, Xianglei; Tsai, I-An; Sabu, Sahadevan; Han, Ching-Chih; Lee, Yuan T.; Chang, Huan‐Cheng; Tu, Shih‐Yu; Kung, A. H.; Wu, Chun‐Chieh

doi:10.1002/anie.200600597

Cited by 76 publications

(73 citation statements)

References 36 publications

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“…This is the reason why direct structural information is rarely available. Vibrational spectra of protonated homochiral serine clusters have been reported recently, [39,40] in particular that of the octamer, the outstanding stability of which is proposed to play a role in the homochirality of life. [41] Several studies have described the reactivity of simple aromatic ions produced by photoionization of jetcooled neutral complexes.…”

Section: Conclusion 6988mentioning

confidence: 99%

Chirality Recognition between Neutral Molecules in the Gas Phase

2008

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Noncovalent interactions are particularly intriguing when they involve chiral molecules, because the interactions change in a subtle way upon replacing one of the partners by its mirror image. The resulting phenomena involving chirality recognition are relevant in the biosphere, in organic synthesis, and in polymer design. They may be classified according to the permanent or transient chirality of the interacting partners, leading to chirality discrimination, chirality induction, and chirality synchronization processes. For small molecules, high-level quantum chemical calculations for such processes are feasible. To provide reliable connections between theory and experiment, such phenomena are best studied in vacuum isolation at low temperature, using rotational, vibrational, electronic, and photoionization spectroscopy. We review these techniques and the results which have become available in recent years, with special emphasis on dimers of permanently chiral molecules and on the influence of conformational flexibility. Analogies between the microscopic mechanisms and macroscopic phenomena and between intra- and intermolecular cases are drawn.

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Section: Conclusion 6988mentioning

confidence: 99%

Chirality Recognition between Neutral Molecules in the Gas Phase

2008

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“…The protonated octamer also has a strong homochiral preference, which has led some to suggest that serine may have played a role in the origin of homochirality in living systems 39-42, 53. The structure of the protonated octamer has been investigated by H/D exchange,54-56 ion mobility,42, 43, 48 infrared photodissociation spectroscopy,57 and quantum chemical calculations,39, 41, 43 from which evidence for at least two different forms of the octamer have been deduced.…”

Section: Introductionmentioning

confidence: 99%

Standard-Free Quantitation of Mixtures Using Clusters Formed by Electrospray Mass Spectrometry

2009

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Ion abundances in electrospray ionization mass spectra depend on many factors, including molecular hydrophobicity, basicity, solution composition, and instrumental parameters. A recently introduced method that uses nonspecific cluster ion abundances to obtain solution-phase molar fractions of analytes directly from ESI mass spectra without using standards was evaluated using solutions containing 0.03% to 24% L-threonine, D-threonine, L-leucine, L-lysine, L-glutamic acid or diglycine with L-serine as a major component. Because of the propensity of serine clusters to exhibit “magic” numbers, which can be chirally selective, these experiments provide a rigorous test of this standard-free cluster quantitation method, which requires that clusters form statistically from analytes in solution. For each of these solutions, the compositions of clusters containing ≥ 32 molecules reflect the solution molar fractions of each component. From the abundances of these larger clusters, the solution molar fraction can be determined to better than 10% accuracy over nearly three orders of magnitude in concentration. In contrast, the ionization/detection efficiency of the individual amino acids differs by as much as a factor of 460 in these experiments. The protonated octamer incorporates some molecules statistically but efficiently excludes other molecules that have significantly different properties or chirality. This standard-free quantitation method may be most advantageous for rapidly characterizing mixtures, such as products of chemical synthesis, which contain unknown products or molecules for which suitable standards are not readily available.

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“…IR spectroscopy without the use of IMS has been used to study the cationic protonated serine octamer with various substitutions in the X-H stretching region (X = N or O; 3000-4000 cm -1 ), however not yielding a definite structure for this complex. [30][31][32] The focus of this study lies on (Ser 8 Cl 2 ) 2-for which a structure with high symmetry and stability is proposed. This structural assignment is supported by the experimental results as well by ab-initio calculations and we speculate that this complex might also exist in the condensed phase.…”

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Infrared spectrum and structure of the homochiral serine octamer–dichloride complex

et al. 2017

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The amino acid serine is known to form a very stable octamer which has properties that sets it apart from serine complexes having different sizes or from complexes composed of other amino acids. For example, both singly protonated serine octamers and anionic octamers complexed with two halogen ions, strongly prefer homochirality even when assembled from racemic D, L mixtures.Consequently, the structures of these complexes are of great interest but no acceptable candidates have so far been identified. Here we investigate anionic serine octamers coordinated with two chloride ions using a novel ion mobility/infrared spectroscopy technique in combination with theoretical calculations. The results allow the identification of a unique structure for (Ser 8 Cl 2 ) 2-that is highly symmetric, very stable, homochiral and whose calculated properties match those observed in the experiments. 3Clusters of atoms or molecules with unusually high relative intensities in mass spectra are termed "magic". In many instances, those "magic" clusters could be assigned to specific structures, often of high symmetry. Examples are numerous and include rare gas clusters 1 , fullerenes, most notably C 60 , 2 Ti 8 C 12 "metallocarbohedrane", 3 metal clusters such as Au 20 , 4,5 and highly symmetric protonated water clusters. 6,7 In the case of C 60 , the initial observation of magic numbers in mass spectra eventually led to the discovery of a new group of materials and a new form of carbon.Occasionally a "magic" cluster resists structural characterization. A famous example is the serine octamer. After electrospray of solutions containing serine, it was first observed that a cluster with the composition (Ser 8 H) + dominated the mass spectrum. 8 This is in contrast to mass spectra of other amino acid clusters, for which the intensity patterns of peaks in their mass spectra show much smoother evolution. The experimental observations have spurred calculations, and several candidates for structures of cationic serine octamers have been proposed. 8,17,[19][20][21] However, for most of them, the proposed structures do not provide an obvious reason for the observed homochirality. In addition, while the calculations indicate that the proposed structures are stable, they are not dramatically more stable compared to serine clusters of different sizes. Thus, there is no general consensus of the structure of serine octamer clusters and the quest for finding a structure that is compatible with the experimental observations is still ongoing. 4In contrast to the abundance of studies on the cationic serine octamer, little attention has so far been given to the anionic species. Here, we present results from a study on serine cluster anions, in which we couple ion mobility-mass spectrometry (IMS-MS) with infrared (IR) spectroscopy.IMS-MS gives the absolute, angle averaged collision cross section (CCS) of specific clusters and this value can be used to determine the overall size of the cluster and to judge if particular calculated structures are compa...

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Progressive Stabilization of Zwitterionic Structures in [H(Ser)_2–8]⁺ Studied by Infrared Photodissociation Spectroscopy

Cited by 76 publications

References 36 publications

Chirality Recognition between Neutral Molecules in the Gas Phase

Chirality Recognition between Neutral Molecules in the Gas Phase

Standard-Free Quantitation of Mixtures Using Clusters Formed by Electrospray Mass Spectrometry

Infrared spectrum and structure of the homochiral serine octamer–dichloride complex

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Progressive Stabilization of Zwitterionic Structures in [H(Ser)2–8]+ Studied by Infrared Photodissociation Spectroscopy

Cited by 76 publications

References 36 publications

Chirality Recognition between Neutral Molecules in the Gas Phase

Chirality Recognition between Neutral Molecules in the Gas Phase

Standard-Free Quantitation of Mixtures Using Clusters Formed by Electrospray Mass Spectrometry

Infrared spectrum and structure of the homochiral serine octamer–dichloride complex

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Product

Resources

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Progressive Stabilization of Zwitterionic Structures in [H(Ser)_2–8]⁺ Studied by Infrared Photodissociation Spectroscopy