Figure Glutamine plays an important role in several neurodegenerative diseases including Huntington’s disease (HD) and Alzheimer’s disease (AD). An intriguing aspect of the structure of glutamine is its incorporation of an amide group in its side chain, thereby opening up the possibility of forming amide-amide H-bonds between the peptide backbone and side chain. In this study the conformational preferences of two capped gluatamines Z(carboxybenzyl)-Glutamine-X (X=OH, NHMe) are studied under jet-cooled conditions in the gas phase in order to unlock the intrinsic structural motifs that are favored by this flexible sidechain. Conformational assignments are made by comparing the hydride stretch ( 3100-3700 cm⁻¹) and amide I and II ( 1400-1800 cm⁻¹) resonant ion-dip infrared spectra with predictions from harmonic frequency calculations. Assigned structures will be compared to previously published results on both natural and unnatural residues. Particular emphasis will be placed on the comparison between glutamine and unconstrained γ-peptides due to the similar three-carbon spacing between backbone and side chain in glutamine to the backbone spacing in γ-peptides. The ability of the glutamine side-chain to form amide stacked conformations will be a main focus, along with the prevalence of extended backbone type structures.¹
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¹W. H. James, III, C W. Müller, E. G. Buchanan, M. G. D. Nix, L. Guo, L. Roskop, M. S. Gordon, L. V. Slipchenko, S. H. Gellman, and T. S. Zwier, J. Am. Chem. Soc., 2009, 131(40), 14243-14245.

2-Aminoisobutyric acid (Aib) is an achiral, α-amino acid having two equivalent methyl groups attached to C_α. Extended Aib oligomers are known to preferentially adopt a 3₁₀-helical structure in the condensed phase.¹ Here, we take a simplifying step and focus on the intrinsic folding propensities of Aib by looking at a single, capped Aib structure and then extending to longer oligomers in the gas phase, free from the influence of solvent molecules and cooled in a supersonic expansion. Resonant two-photon ionization and IR-UV holeburning will be used to record single-conformation UV spectra using the Z-cap as UV chromophore. Resonant ion-dip infrared (RIDIR) spectroscopy provides single-conformation IR spectra in the OH stretch, NH stretch, amide I and amide II regions. Two conformational isomers have been identified for the smallest unit in the study, Z-Aib-OH, and four conformational isomers were seen for Z-Aib-Aib-OH, with widely-varying IR spectral patterns. In addition to investigating the conformational dependence on oligomer length, this work also studies the steric and electrostatic impact of different capping groups, R-X where X = -OH, -OMethyl, and -OtButyl. These caps are considered here for the case of Z-Aib-Aib-X. Extension to larger Z-(Aib)_n-X oligomers will shed light on the extent to which the solution phase preference for 3₁₀-helix formation is retained in the gas phase, and when its onset first appears. When possible ¹³C isotopomers will be used to assist with the assignments and modulate the coupling between amide I fundamentals.
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¹Toniolo, C.; Bonora, G. M.; Barone, V.; Bavoso, A.; Benedetti, E.; Di Blasio, B.; Grimaldi, P.; Lelj, F.; Pavone, V.; Padone, C., Conformation of Pleionomers of α-Aminoisobutyric Acid. Macromolecules 1985, 18, 895-902.

Recent improvements in laser ablation molecular beam Fourier transform microwave spectroscopy (LA-MB-FTMW) have allowed the investigation of glutamine (COOH-CH(NH₂)-CH₂-CH₂-CONH₂), a natural amino acid with a long polar side chain. One dominant structure has been detected in the rotational spectrum. The nuclear quadrupole hyperfine structure of two ¹⁴N nuclei has been totally resolved allowing the conclusive identification of the observed species.

The rotational spectrum of the natural amino acid tryptophan has been observed using a recently constructed LA-MB-FTMW spectrometer, specifically designed to optimize the detection of heavier molecules at a lower frequency range. Independent analyses of the rotational spectra of individual conformers have conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The experimental values of the ¹⁴N nuclear quadrupole coupling constants have been found capital in the discrimination of the conformers. Both observed conformers are stabilized by a O-H…N hydrogen bond in the side chain and a N–H…π interaction forming a chain that reinforces the strength of hydrogen bonds through cooperative effects.

Resonance enhance multiphoton ionization (REMPI) and UV-UV double resonance spectra of L-β-homotryptophan (HTrp) was obtained. Hydrochloride salt of HTrp was applied on a lateral surface of a graphite disk, desorbed by 1064 nm nanosecond laser pulses, and subsequently cooled down by expanding gas from a pulsed valve. Formation of neutral HTrp by laser-desorption was confirmed by its mass spectrum. The REMPI spectrum shows several peaks in a UV region similar to that of tryptophan. UV-UV hole-burning spectrum was obtained and compared with quantum mechanical calculation. Based on the experimental and computational results, conformation preference of HTrp is discussed.

The rotational spectrum of the amino alcohol serinol CH₂OH-CH(NH₂)-CH₂OH, which constitutes the hydrophilic head of the lipid sphingosine, has been investigated using chirped-pulsed Fourier transform microwave spectroscopy in combination with laser ablation¹. Five different forms of serinol have been observed and conclusively identified by the comparison between the experimental values of their rotational and ¹⁴N quadrupole coupling constants and those predicted by ab initio calculations. In all observed conformers several hydrogen bonds are established between the two hydroxyl groups and the amino groups in a chain or circular arrangement. The most abundant conformer is stabilised by O-H···N and N-H···O hydrogen bonds forming a chain rather than a cycle. One of the detected conformers presents a tunnelling motion of the hydrogen atoms of the functional groups similar to that observed in glycerol².
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¹S. Mata, I. Peña, C. Cabezas, J. C. López, J. L. Alonso, J. Mol. Spectrosc. 2012, 280, 91 ²V. V. Ilyushin, R. A. Motiyenko, F. J. Lovas, D. F. Plusquellic, J. Mol. Spectrosc. 2008, 251, 129.

The most abundant conformer of the amino alcohol D-phenylglycinol has been observed in gas phase using broadband chirped pulse Fourier transform microwave spectroscopy (CP-FTMW) and laser ablation molecular beam Fourier transform microwave spectroscopy (LA-MB-FTMW). The rotational spectra corresponding to seven monosubstituted ¹³C, one monosubstituted ¹⁵N and one monosubstituted ¹⁸O species have been observed in their natural abundance, and the r_s structure has been derived. The observed conformer is stabilized by O-H…N, N-H…π intramolecular hydrogen bond network.

The nucleoside of uridine has been placed in the gas phase by laser ablation and the most stable C2'-anti conformation characterized by broadband chirped pulse (CP-FTMW) and narrowband molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopies. The quadrupole hyperfine structure, originated by two ¹⁴N nuclei, has been completely resolved. Intramolecular hydrogen bonds involving uracil and ribose moieties have been found to play an important role in the stabilization of the nucleoside.

A laser ablation method has been successfully used to vaporize the bioactive amino monosaccharide D-glucosamine. Three cyclic α-⁴C₁ pyranose forms have been identified using a combination of CP-FTMW and LA-MB-FTMW spectroscopy. Stereoelectronic hyperconjugative factors, like those associated with anomeric or gauche effects, as well as the cooperative OH…O, OH…N and NH…O chains, extended along the entire molecule, are the main factors driving the conformational behavior. All observed conformers exhibit a counter-clockwise arrangement (cc) of the network of intramolecular hydrogen bonds. The results are compared with those recently obtained for D-glucose.¹
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¹ J. L. Alonso, M. A. Lozoya, I. Peña, J. C. López, C. Cabezas, S. Mata, S. Blanco, Chem. Sci. 2014, 5, 515.

The dipeptide Ala-Gly has been examined in gas phase by laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy in the frequency region 3-12 GHz. Three rotamers have been detected in the supersonic expansion. The quadrupole hyperfine structure of two ¹⁴N (I=1) nuclei has been totally resolved allowing the conclusive identification of one conformer.

Carbohydrates have multiples roles in biological systems. It has been found that the glycoside bond is fundamentally important in many aspects of chemistry and biology and forms the basis of carbohydrate chemistry. That means the stereochemical information, namely, glycosidic linkages α or β, gives an significant features of the carbohydrate glycosidation position of the glycosylic acceptor. For these reasons, much effort was made for the synthesis and analysis of the glycoside bond. Vibrational circular dichroism VCD has some advantages over conventional electronic circular dichroism (ECD) due to the applicability to all organic molecules and the reliability of ab initio quantum calculation. However, for a molecule with many chiral centers such as carbohydrates, determination of the absolute configuration tends to be difficult because the information from each stereochemical center is mixed and averaged over the spectrum. In the CH stretching region, only two VCD studies on carbohydrates have been reported and spectra-structure correlation, as determined for the glycoside band, remains to be investigated. T. Taniguchi and collaborators report that methyl glycosides exhibit a characteristic VCD peak, the sign of which solely reflects the C-1 absolute configuration. This work is a theoretical contribution to study the behaviour of VCD spectrum's of the monosaccharides when the water molecules are taken explicitly. This study is focused on six different monosaccharides in theirs absolute configuration R and S. We used the method of density functional theory DFT by means of the B3LYP hybrid functional and 6-31G * basis set.

Figure One new synthetic probes for the detection of copper and Histidine in both vitro and living cells. In the absence of metal ions, the new established probes exhibits comparable fluorescence to that of free FITC. In the presence of metal ions, probes selectively coordinates with Cu²⁺, causing its fluorescence emission quenched via photoinduced electron transfer. Interestingly, as-formed complex selectively responds to _L-His among the 20 natural AAs by turning its fluorescence on. Using this dualfunctional probe, we also sequentially imaged Cu²⁺ and _L-His in living cells. Our new probe could be applied for not only environment monitoring or biomolecule detections, but also disease diagnoses in the near future.

Fully mining the valid information in soil spectral library, establishing a strong universal inversion model to predict soil total nitrogen (TN) content is one of the important applications of high spectral direction. Studies using partial least squares regression (PLSR) global model, locally weighted regression (LWR) and fuzzy K-means clustering methods combined with PLSR (FKMC-PLSR). 1661 soil samples were collected from 13 provinces in China, which include Tibet, Xinjiang, Heilongjiang, and Hainan. The samples represent 17 soil groups of the Chinese Soil (Genetic) Classification System, and Zhejiang province 104 paddy soil samples to predict. The results show that, under the national scale PLSR global model for high TN values underestimated the prevalence of samples to be predicted, resulting in low overall predictive accuracy; LWR (R² = 0.76, RPD_P2 = 2.1), especially FKMC-PLSR (R² = 0.82, RPD_P3 = 2.4) than the local model PLSR (R² = 0.64, RPD_P1 = 1.4) global model can more accurately inversion TN content. The results can take advantage of the national scale to establish stability and universal spectral database higher content of soil TN forecasting model to provide the necessary information.

This paper introduces a new approach called grey incidence analysis(GIA), by which high accuracy prediction model can be established combined with partial least squares regression(PLSR) to deal with Chinese soil vis-NIR spectral library and estimate soil total nitrogen content in local area. Using spectral matching algorithm such as Mahalanobis distance, spectral angle model (SAM) and spectral correlation fitting(SCF), fuzzy k-means clustering method only based on the spectral data without considering soil total nitrogen content in the library. Soil total nitrogen content have grey uncertainty relationship with each vis-NIR spectral band(400-2500nm). This method combine the soil total nitrogen value with spectrum data when performing spectral matching. In this study, 1661 soil samples in the library were collected from 13 provinces in China, which include Tibet, Xinjiang, Heilongjiang, and Hainan. The samples represent 17 soil groups of the Chinese Soil (Genetic) Classification System. After air-drying and sieving, the diffuse reflectance spectra of the samples were measured under laboratory conditions in the range between 400 and 2500 nm using a portable vis-NIR spectrometer. Hyperspectral inversion model was built based on 104 paddy soil samples in Zhejiang province to predict the soil total nitrogen content. The results show that the GIA-PLSR method presents great potential for predicting soil total nitrogen content in large soil vis-NIR library. The prediction accuracy: R² = 0.897, RMSE_P = 0.028, RPD_P = 3.151. This study also show that soil vis-NIR spectroscopy combined with TN value can be used to further improve the prediction performance of spectral models.