H-bonding Characteristics Research Articles

Direct evidence for a deprotonated lysine serving as a H-bond "acceptor" in a photoreceptor protein.

Deprotonation or suppression of the pKa of the amino group of a lysine sidechain is a widely recognized phenomenon whereby the sidechain amino group transiently can act as a nucleophile at the active site of enzymatic reactions. However, a deprotonated lysine and its molecular interactions have not been directly experimentally detected. Here, we demonstrate a deprotonated lysine stably serving as an "acceptor" in a H-bond between the photosensor protein RcaE and its chromophore. Signal splitting and trans-H-bond J coupling observed by NMR spectroscopy provide direct evidence that Lys261 is deprotonated and serves as a H-bond acceptor for the chromophore NH group. Quantum mechanical/molecular mechanical calculations also indicate that this H-bond exists stably. Interestingly, the sidechain amino group of the lysine can act as both donor and acceptor. The remarkable shift in the H-bond characteristics arises from a decrease in solvation, triggered by photoisomerization. Our results provide insights into the dual role of this lysine. This mechanism has broad implications for other biological reactions in which lysine plays a role.

Theoretical investigation of the effects of diverse hydrogen-bonding characteristics on the 17O chemical shielding and electric field gradient tensors within the active sites of MraYAA bound to nucleoside antibiotics capuramycin, carbacaprazamycin, 3′-Hydroxymureidomycin A, and muraymycin D2

This study builds upon our prior researches and seeks to investigate and clarify the influences of various characteristics of hydrogen bonds (H-bonds) and charge transfer (CT) interactions, which were detected within the inhibitor binding pockets (labeled as the QM models I–IV) of MraYAA–capuramycin, MraYAA–carbacaprazamycin, MraYAA–3′-hydroxymureidomycin A, and MraYAA–muraymycin D2 complexes by QTAIM and NBO analyses from DFT QM/MM MD calculations, on the 17O chemical shielding (CS) and electric field gradient (EFG) tensors of carboxylate (Oδ), carbonyl (C═O), and hydroxyl (O–H) oxygens in these models. The 17O CS and EFG tensors of these three types of oxygens in QM models I–IV were calculated at the M06-2X/6-31G** level by including the solvent effects using the polarizable continuum model. From the computed 17O CS and EFG tensors in these models, it was found that the nuclear shielding, σiso, for carboxylate or carbonyl oxygen increases (shielding effect) as the H-bond length decreases and the percentage p-character of nOδ/nC═O lone pair partner in the CT interaction enhances. In contrast, the σiso (17O–H) decreases (deshielding effect) with a reduction in the H-bond length as well as with an enhancement in percentage s-character of the nOH lone pair/σ*O–H antibond. By reducing the H-bond length or by increasing p-character of the nOδ/nC═O lone pair, the 17Oδ/17O═C quadrupole coupling constant smoothly decreases, while the 17Oδ/17O═C asymmetry parameter smoothly increases. Moreover, these calculated parameters are in a good agreement with the experimental values. The information garnered here is valuable particularly for further understanding of empirical correlations between 17O NMR spectroscopic and H-bonding characteristics in the protein–ligand complexes.

Thermodynamically Stable Cationic Dimers in Carboxyl-Functionalized Ionic Liquids: The Paradoxical Case of "Anti-Electrostatic" Hydrogen Bonding.

We show that carboxyl-functionalized ionic liquids (ILs) form doubly hydrogen-bonded cationic dimers (c+=c+) despite the repulsive forces between ions of like charge and competing hydrogen bonds between cation and anion (c+–a−). This structural motif as known for formic acid, the archetype of double hydrogen bridges, is present in the solid state of the IL 1−(carboxymethyl)pyridinium bis(trifluoromethylsulfonyl)imide [HOOC−CH2−py][NTf2]. By means of quantum chemical calculations, we explored different hydrogen-bonded isomers of neutral (HOOC–(CH2)n–py+)2(NTf2−)2, single-charged (HOOC–(CH2)n–py+)2(NTf2−), and double-charged (HOOC– (CH2)n−py+)2 complexes for demonstrating the paradoxical case of “anti-electrostatic” hydrogen bonding (AEHB) between ions of like charge. For the pure doubly hydrogen-bonded cationic dimers (HOOC– (CH2)n−py+)2, we report robust kinetic stability for n = 1–4. At n = 5, hydrogen bonding and dispersion fully compensate for the repulsive Coulomb forces between the cations, allowing for the quantification of the two equivalent hydrogen bonds and dispersion interaction in the order of 58.5 and 11 kJmol−1, respectively. For n = 6–8, we calculated negative free energies for temperatures below 47, 80, and 114 K, respectively. Quantum cluster equilibrium (QCE) theory predicts the equilibria between cationic monomers and dimers by considering the intermolecular interaction between the species, leading to thermodynamic stability at even higher temperatures. We rationalize the H-bond characteristics of the cationic dimers by the natural bond orbital (NBO) approach, emphasizing the strong correlation between NBO-based and spectroscopic descriptors, such as NMR chemical shifts and vibrational frequencies.

Towards thermodynamically stable anionic dimers with “anti-electrostatic” hydrogen bonds overcoming like-charge repulsion

We provide quantum chemical evidence for thermodynamically stable anionic dimers, wherein short-range, attractive hydrogen bonds overcome long-range, repulsive Coulomb interaction. We employed ab initio and density functional theory for studying the kinetic and thermodynamic stability for homodimers of singly deprotonated dicarboxylic acid anions. For the dimeric structures (HOOC(CH2)nCOO−)2 with n = 0–4 we calculated robust local minima with clear dissociation barriers preventing “Coulomb explosion” into separated anions. Already for n = 5 hydrogen bonding and dispersion forces fully compensate for the repulsive Coulomb forces between the anions allowing for the quantification of the two equivalent hydrogen bonds and dispersion interaction in the order of 62 kJmol−1 and 11 kJmol−1 respectively. The increasing kinetic stability even turns into thermodynamic stability with increasing number of methylene groups tethering the negative charges at the carboxylate groups. For n > 5 quantum-type short-range attraction wins over classical long-range electrostatic repulsion resulting in negative binding energies and providing the first energetically stable anionic dimers. For n = 6 and n = 7 we calculated negative free energies below 50 and 100 K, respectively. Even considering pressure effects, the dimers of the singly deprotonated octanedioic acid and nonanedioic acid anions should be detectable by means of cryogenic ion vibrational spectroscopy at temperatures from 10 to 30 K. We rationalize the H-bond characteristics of the dimers by the Natural Bond Orbital (NBO) approach, emphasizing the strong correlation between NBO-based and experimental descriptors.

Case Study in Kraft Lignin Fractionation: “Structurally Purified” Lignin Fractions—The Role of Solvent H-Bonding Affinity

Softwood kraft lignin SKL was fractionated using aprotic acetone and protic methanol to yield both previously reported “traditional” fractions and novel refined fractions thereof. Based on differences in mutual H-bonding affinities exerted by the solvents on one side and the OH group characteristics of the lignin oligo- and polymers on the other side, the 85% acetone-insoluble kraft lignin fraction AIKL, for example, could be further fractionated in 16% methanol-soluble and 67% methanol-insoluble parts. Sequential use of the two solvents practically resembled a refinement protocol that shed light on eventual “structural impurities” contained in the traditional fractions, which is not delineable easily in front of the background of a dominating spectroscopic image. Exploiting H-bonding characteristics offers a valid option for the facile generation of truly “structurally purified” lignin fractions. Acetone-insoluble, methanol-soluble MSAIKL, for example, exhibits 25% less aliphatic interunit bonding while being enriched in phenolic groups up to 25%, thus representing condensed, lower-molecular-weight structures with overall H-bond accepting character that was still contained in the overall larger-molecular-weight acetone-insoluble AIKL. More “polyphenylpropanoidic” parts practically free of condensed units, determining the overall structural picture of the unrefined lignins due to their overall abundance, are represented by the globally insoluble fractions like acetone-insoluble, methanol-insoluble MIAIKL. The original fractions and refined fractions generated based on targeting specific H-bonding affinities give a more homogeneous picture with respect to trends in glass transition temperatures, clearly indicating that Tg is dominated by actually both MW and nature of OH groups.

Long-Range Ordered Water Correlations between A–T/C–G Nucleotides

Summary The interactions between complementary base pairs are crucial to the helical duplex structure of DNA. Although base-base interactions have been widely reported, the study of long-range interactions in the base-pairing processes is still a major challenge in this field. Here, we first study the long-range interactions between the base pairs by atomic force microscopy-based single-molecule force spectroscopy (SMFS). The SMFS results of A–T/C–G imply that there are weak long-range interactions between them, which have a range of 15–25 nm. Raman spectroscopy results imply that these weak interactions can be attributed to multiplex hydrogen bond interaction of ordered water structure between A–T/C–G nucleotides. In addition, the theoretical calculations deduce that the ideal structure of these water molecules exhibits a specific helical structure. Our findings might open up a new understanding of biological assembly processes and provide helpful strategies for bio-nanotechnology.

Spatially resolved hydration shells and dynamics of different sulfur species in water from first-principle molecular dynamics simulations

A comprehensive ab initio molecular dynamics (AIMD) simulation study is performed on the waterborne S-IV and S-VI species for different oxidation states and characterized for their spatial hydration nature, hydrogen bonding (H-bonding) and spectroscopic aspects. The vibrational modes of the power spectra and the influence of H-bonding for each species in the condensed phases are characterized by comparing with the normal modes of the species in the gas phase. In particular, it has been found that the H-bonds formed by S–IV species are more in number than those of S–VI species per oxygen site and are at least 2 times more durable than those for the latter. It has been predicted that such characteristics of H-bonds will significantly change the transport characteristics of the species.

Structural and hydrogen-bonding properties of neat t-BuNH2 and its binary mixtures with CCl4, CHCl3 and DMSO

Many physicochemical features of substances are influenced by the inter-species interactions, most importantly hydrogen/halogen bonds (H-/X-bonds). In the present study, the structural and H-bonding characteristics of neat t-BuNH2 along with its binary mixtures with cosolvents CCl4, CHCl3 and DMSO‑d6 were investigated by ATR-FTIR and quantum chemical calculations. Excess absorption and two-dimensional correlation spectroscopies were used for further analysis of the obtained IR data. The results show that mixing CCl4 and CHCl3 with t-BuNH2 transform the dimer and the cyclic trimer of t-BuNH2 to monomer, with negligible effect of cross complexes on the spectral shapes in ʋ(N–H). However, as a strong H-bond acceptor, DMSO impacts the system in a significantly different manner. It develops strong H-bonds with t-BuNH2. In t-BuNH2‒DMSO system, all the species of t-BuNH2 including dimer and monomer transform to complexes with DMSO. It was also found that all the H-/X-bonds identified between t-BuNH2 and cosolvents are non-covalent in nature with more contribution from electrostatic interactions.

Dielectric-Dependent Strength of Interlipid Hydrogen Bonding in Biomembranes: Model Case Study.

Atomistic aspects of the structural organization, dynamics, and functioning of hydrated lipid bilayers-model cell membranes-are primarily governed by the fine balance of intermolecular interactions between all constituents of these systems. Besides the hydrophobic effect, which shapes the overall skeleton of lipid membranes, a very important contribution to their behavior is made by hydrogen bonds (H-bonds) between lipid head groups. The latter determine crucial phenomena in cell membranes, such as dynamic ultrananodomain organization, hydration, and fine-tuning of microscopic physicochemical properties that allow the membrane to adapt quickly when binding/insertion external agents (proteins, etc.). The characteristics of such H-bonds (strength, spatial localization, etc.) dramatically depend on the local polarity properties of the lipid-water environment. In this work, we calculated free energies of H-bonded complexes between typical donor (NH3+, NH, OH) and acceptor (C═O, OH, COO-, COOH) groups of lipids in vacuo and in a set of explicit solvents with dielectric constants (ε) from 1 to 78.3, which mimic membrane environment at different depths. This was done using Monte Carlo simulations and an assessment of the corresponding potential of mean force profiles. The strongest H-bonded complexes were observed in the nonpolar environment, and their strength increased sharply with decreasing ε below 17. When ε changed, the largest free energy gain (>10.8 kcal/mol) was observed for pairs of acceptors C═O and O(H) with donor NH3+. The complexation of the same acceptors with NH donor in this range of ε values was rather less sensitive to the environmental polarity, by ∼1.5 kcal/mol. Dielectric-dependent interactions of polar lipid groups with water were evaluated as well. The results explain the delicate balance that determines the unique pattern of H-bonds for a particular lipid bilayer. Understanding the factors that regulate the propensity for H-bonding in lipid bilayers provides a fundamental basis for the rational design of new membrane nano objects with predefined properties.

Nanoconfined Water within Graphene Slit Pores Adopts Distinct Confinement-Dependent Regimes.

In view of the increasing importance of nanoconfined aqueous solutions for various technological applications, it has become necessary to understand how strong confinement affects the properties of water at the level of molecular and even electronic structure. By performing extensive ab initio simulations of two-dimensionally nanoconfined water lamellae between graphene sheets subject to different interlayer spacings, we find new regimes at interlayer distances of 10 Å and less where water can be described neither to behave like interfacial water nor to be bulklike at the level of its H-bonding characteristics and electronic structure properties. It is expected that this finding will offer new opportunities to tune both diffusive and reactive processes taking place in aqueous environments that are strongly confined by chemically inert hard walls.

Fine Tuning of Microscopic Properties in Two-Component Zwitterionic-Anionic Lipid Bilayers: Determinant Role of H-Bonding

Structure, dynamics, and functioning of hydrated lipid bilayers - model cell membranes - are governed by a thin balance of intermolecular interactions between constituents of these systems. Besides the hydrophobic effect, which determines the overall bilayer skeleton, important contribution is made by H-bonds between lipids, water, and ions. This determines crucial phenomena in cell membranes: dynamic clustering, hydration, fine tuning of microscopic physico-chemical properties, which permit fast adaptation of membranes to external agents (e.g., proteins). Characteristics of H-bonds (strength, spatial location, etc.) dramatically depend on local polarity properties of water-lipid environment. Here, we calculated free energies of H-bonded complexes between lipids and water in explicit solvents of different polarity (water, methanol, chloroform) mimicking membrane environment at different depth. The strongest H-bonds were observed in nonpolar environment, although the overall bilayer organization imposes serious limitations on the distribution of various types of H-bonds over hydrophobic/hydrophilic regions (corresponding to dielectric media with low and high permeability). This creates a delicate balance, which determines a unique H-bonding pattern for each particular lipid bilayer. This was confirmed via atomistic molecular dynamics (MD) of several hydrated lipid bilayers. Understanding of the factors regulating H-bonding propensities in such systems is indispensable for rational design of new membrane-like materials with predefined properties. One example - an artificial lipid with engineered hydroxyl group - is studied via MD simulations. It is shown that such lipids can induce significant changes of key characteristics of model membranes. This opens new avenues in goal-oriented design of artificial membranes with engineered properties. Acknowledgements: Russian Science Foundation (14-50-00131), Russian Foundation for Basic Research (16-04-00578), RAS MCB Program, Supercomputer Center “Polytechnical” (St. Petersburg Polytechnic University), Joint Supercomputer Center of RAS (Moscow).

The Origin of Chalcogen-Bonding Interactions.

Favorable molecular interactions between group 16 elements have been implicated in catalysis, biological processes, and materials and medicinal chemistry. Such interactions have since become known as chalcogen bonds by analogy to hydrogen and halogen bonds. Although the prevalence and applications of chalcogen-bonding interactions continues to develop, debate still surrounds the energetic significance and physicochemical origins of this class of σ-hole interaction. Here, synthetic molecular balances were used to perform a quantitative experimental investigation of chalcogen-bonding interactions. Over 160 experimental conformational free energies were measured in 13 different solvents to examine the energetics of O···S, O···Se, S···S, O···HC, and S···HC contacts and the associated substituent and solvent effects. The strongest chalcogen-bonding interactions were found to be at least as strong as conventional H-bonds, but unlike H-bonds, surprisingly independent of the solvent. The independence of the conformational free energies on solvent polarity, polarizability, and H-bonding characteristics showed that electrostatic, solvophobic, and van der Waals dispersion forces did not account for the observed experimental trends. Instead, a quantitative relationship between the experimental conformational free energies and computed molecular orbital energies was consistent with the chalcogen-bonding interactions being dominated by n → σ* orbital delocalization between a lone pair (n) of a (thio)amide donor and the antibonding σ* orbital of an acceptor thiophene or selenophene. Interestingly, stabilization was manifested through the same acceptor molecular orbital irrespective of whether a direct chalcogen···chalcogen or chalcogen···H-C contact was made. Our results underline the importance of often-overlooked orbital delocalization effects in conformational control and molecular recognition phenomena.

Ab initio study of hydrogen bonding in the H3PO2 dimer and H3PO2-DMF complex.

The molecular structures and H-bonding interactions in the phosphinic acid dimer and the complex of phosphinic acid with N,N-dimethylformamide (DMF) were investigated by density functional theory calculations at the B3LYP level of theory. In order to better understand these phenomena, the individual molecules were also studied. The results were compared with previously obtained data for similar H-bonded complexes of phosphoric and phosphorous acids with DMF. Various correlations were found between geometric characteristics and parameters derived from Bader's theory and natural bond orbital analysis. Graphical abstract Irina V. Fedorova and Lyubov P. Safonova. Ab initio study of hydrogen bonding in the H3PO2 dimer and H3PO2-DMF complex. The acids of phosphorus are considered suitable candidates for ionomers due to their efficient proton transport properties. In order to better understand their molecular structures and their H-bond characteristics in real liquids, the most stable configurations of the H3PO2 dimer and the H3PO2-DMF complex were examined using computational methods in quantum chemistry. It was found that the strength of the H-bonding interactions in these systems depends strongly on the environment.

Universality of hydrogen bond distributions in liquid and supercritical water

Monte Carlo and molecular dynamics computer simulations using the rigid TIP4P and the flexible BJH intermolecular H2O potentials were carried out for 50 states of supercritical water characterizing a very wide range of thermodynamic conditions, 573≤T≤1273K; 0.02≤ρ≤1.67g/cm3; 10≤P≤10,000MPa. Good agreement with available experimental data of the simulated thermodynamic and structural properties give confidence to the quantitative statistical analysis of intermolecular hydrogen bonding under the conditions studied. Energetic, geometric, and angular characteristics of supercritical H-bonds and their distributions at a given temperature remain almost invariant over the entire density range studied from dilute gas-like (~0.03g·cm−3) to highly compressed liquid-like (~1.5g·cm−3) states. The increase of temperature from ambient to supercritical affects the characteristics of H-bonding in water much more dramatically than the changes in density along any supercritical isotherm. Compared to H-bonds in liquid water under ambient conditions, the H-bonds at 773K are, on average, 10% weaker, 5% longer, and less linear.Both above and below the H-bonding percolation threshold the fractions of H2O molecules involved in a certain number of H-bonds in liquid and supercritical water closely follow the universal binomial distribution as a function of the average number of H-bonds per one water molecule in the system, as predicted by the independent bond theory. This universal distribution remains intact even when dynamic criteria of H-bonding lifetimes are additionally applied.

Theoretical study on electronic and vibrational properties of hydrogen bonds in glycine-water clusters

The hydrogen bond (H-bond) in organic-water molecules is essential in nature, and it present unique properties distinct from those in pure water or organic clusters. Combining with the charge-transfer and energy decomposition analyses, we investigated the penetrating molecular-orbitals in glycine-water clusters, which give evidences of the covalent-like characteristics of H-bonds in this system. Besides, the infrared spectral features provide a rare opportunity to discover the exceedingly-evident redshifts of symmetric stretching modes (Symst) in water on forming H-bond, in contrast to the slightly-redshifted asymmetric stretching modes (Asyst) in water. To explain these intriguing behaviors, we further analyzed the nuclear vibrating patterns, which clearly reveal that H-bond retains two unexpected effects on nuclear motions in water: (i) Intensifying donor Symst, and (ii) Inhibiting donor Asyst. Furthermore, we also quantified the impact of anharmonic quantum fluctuations on each hydrogen bond. For the stretching modes involved in H-bonds, red shifts up to more than one hundred wave numbers are observed under anharmonic vibration, explicitly indicating the increased ‘covalency’ of H-bonds. These finds shed light on the essential understanding of H-bonding comprehensively, and should provide incentives for future experimental studies.

Chemoselective intermolecular hydrogen bonding in peptides: An electronic and topological study on the H-bonding selectivities in peptidomimetic HCV protease inhibitor telaprevir

Chemoselectivity in intermolecular hydrogen bonding in polypeptides is demonstrated via a comprehensive study on the H-bonding characteristics of the peptidomimetic hepatitis C protease inhibitor telaprevir (1) using well-established computational tools. Starting with a QTAIM and NBO analysis of the H-bonding selectivities observed in the crystal structure of 1 and its 4-HBA cocrystal, the analysis was extended to model systems of the amino acid residues of 1 (P1res, P3res, and P4res) complexed with formic acid. The carboxylic acid/amide H-bonding of these models showed consistently stronger H-bonding at the P3 residue. The degree of chemoselectivity was quantified by comparing the QTAIM and NBO parameters between the P1res-FA, P3res-FA, and P4res-FA models. The chemoselectivity in 1 is consistent with the calculations of the FA residue models. These results demonstrate the impact of chemoselectivity in non-covalent interactions and can be extended to understanding H-bonding selectivities in polypeptides, proteins, and other macromolecular systems.

Quantum-сhemical analysis of geometric and energetic characteristics of hetero associates m9Ade•m1Ura in main tautomeric form

For the first time, on the quantum-mechanical level of theory MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p), a full set of hydrogen (H)-bonded hetero associates m 9 Ade·m 1 Ura in the main tautomeric forms consisting of 18 different structures was obtained. Their structural and energetical parameters were characterized and basic physical and chemi­cal characteristics of intermolecular H-bonds that stabilize the investigated complexes were described. It was shown that global minimum of Gibbs free energy corresponds to Hoogsteen pair, after it with a small margin follow Watson–Crick pair, inverse Hoogsteen pair and inverse Watson–Crick pair. It was found that in stabilization of identified hetero associates four types of H-bonds – NH...O, NH...N, CH...O and CH...N are involved. In this case non-canonical CH...O and CH...N bonds show a linear dependence of energy on electron density in the corresponding critical point. Obtained data may be useful for experimental interpretation of the features of non-canonical base pairs association by common methods of spectroscopy, including NMR and vibrational spectroscopy. They are also important for understanding the problem of mutational variability that is caused by formation of non-complementary pairs of nucleotide bases whose role is not clear yet. Keywords: quantum chemistry, hetero associates of nucleotide bases, hydrogen bonds, adenine, uracil.

Effects of hydrogen bonds and the solubility of onium hexafluorosilicates

The relationship between the water solubility of hexafluorosilicates with different types of onium cations and the characteristics of interionic H-bonds in their structures was analyzed. The antibate correlation between the solubility and the number of short interionic H-bonds was revealed for salts with aromatic heterocyclic and arylammonium cations.

Discovery of 4-(5-(Cyclopropylcarbamoyl)-2-methylphenylamino)-5-methyl-N-propylpyrrolo[1,2-f][1,2,4]triazine-6-carboxamide (BMS-582949), a Clinical p38α MAP Kinase Inhibitor for the Treatment of Inflammatory Diseases

The discovery and characterization of 7k (BMS-582949), a highly selective p38α MAP kinase inhibitor that is currently in phase II clinical trials for the treatment of rheumatoid arthritis, is described. A key to the discovery was the rational substitution of N-cyclopropyl for N-methoxy in 1a, a previously reported clinical candidate p38α inhibitor. Unlike alkyl and other cycloalkyls, the sp(2) character of the cyclopropyl group can confer improved H-bonding characteristics to the directly substituted amide NH. Inhibitor 7k is slightly less active than 1a in the p38α enzymatic assay but displays a superior pharmacokinetic profile and, as such, was more effective in both the acute murine model of inflammation and pseudoestablished rat AA model. The binding mode of 7k with p38α was confirmed by X-ray crystallographic analysis.

An ab initioand AIM investigation into the hydration of 2-thioxanthine

BackgroundHydration is a universal phenomenon in nature. The interactions between biomolecules and water of hydration play a pivotal role in molecular biology. 2-Thioxanthine (2TX), a thio-modified nucleic acid base, is of significant interest as a DNA inhibitor yet its interactions with hydration water have not been investigated either computationally or experimentally. Here in, we reported an ab initio study of the hydration of 2TX, revealing water can form seven hydrated complexes.ResultsHydrogen-bond (H-bond) interactions in 1:1 complexes of 2TX with water are studied at the MP2/6-311G(d, p) and B3LYP/6-311G(d, p) levels. Seven 2TX...H2O hydrogen bonded complexes have been theoretically identified and reported for the first time. The proton affinities (PAs) of the O, S, and N atoms and deprotonantion enthalpies (DPEs) of different N-H bonds in 2TX are calculated, factors surrounding why the seven complexes have different hydrogen bond energies are discussed. The theoretical infrared and NMR spectra of hydrated 2TX complexes are reported to probe the characteristics of the proposed H-bonds. An improper blue-shifting H-bond with a shortened C-H bond was found in one case. NBO and AIM analysis were carried out to explain the formation of improper blue-shifting H-bonds, and the H-bonding characteristics are discussed.Conclusion2TX can interact with water by five different H-bonding regimes, N-H...O, O-H...N, O-H...O, O-H...S and C-H...O, all of which are medium strength hydrogen bonds. The most stable H-bond complex has a closed structure with two hydrogen bonds (N(7)-H...O and O-H...O), whereas the least stable one has an open structure with one H-bond. The interaction energies of the studied complexes are correlated to the PA and DPE involved in H-bond formation. After formation of H-bonds, the calculated IR and NMR spectra of the 2TX-water complexes change greatly, which serves to identify the hydration of 2TX.