Inclusion Of Water Molecules Research Articles

Effect of ectoine on hydration spheres of peptides–spectroscopic studies

In this paper, we use FTIR spectroscopy to characterize the hydration water of ectoine, its interactions with two peptides–diglycine and NAGMA, and the properties of water molecules in the hydration spheres of both peptides changed by the presence of the osmolyte. We found that the interaction of ectoine with the peptide hydration shells had no effect on its own hydration sphere. However, the enhanced hydration layer of the osmolyte influences the hydration shells of both peptides and does so in a different way for both peptides: (1) the interfacial interaction of the NAGMA peptide and ectoine hydration spheres strengthened the hydration shell of this peptide; (2) the inclusion of water molecules from the ectoine hydration sphere into the diglycine hydration sphere had only a marginally enhancing effect. Since ectoine is being used in more and more biopharmaceutical products and cosmetics, knowledge of the properties of its hydration shell and its effect on the hydration shell of other molecules is extremely relevant to understanding its protective mechanism.

Site-specific relaxation of peptide bond planarity induced by electrically attracted proton/deuteron observed by neutron crystallography.

In structural biology, peptide bonds, fundamental linkages between hundreds of amino acids, of which a protein molecule is composed, have been commonly treated as a plane structure just as Linus Pauling et al. proposed. In this paper, a site-specific peptide bond relaxation mechanism by deuterons whose localization has been suggested by neutron crystallography is proposed. Such deuteron was observed as an arm of neutron scattering length density protruding from the carbonyl oxygen atoms in the main chain in the omit map drawn by neutron crystallography of human lysozyme. Our comprehensive study using x-ray and neutron diffraction and 15 N chemical shifts of individual amide nitrogen atoms within the same peptide bond strongly suggests the relaxation of the electronic resonance structure because of site-specific modulation by protons/deuterons localized on the electron orbital of the carbonyl oxygen. All experimental data used in this examination were obtained at room temperature, which is preferable for enzymatic activity. Such a close interaction between the electron resonance structure of a peptide bond and the exchangeable protons/deuterons well agreed with that observed in an intermediate state in an amide hydrolytic reaction simulated by the ab-initio calculation including water molecules.

Synthesis, Structural, FT-IR, UV-Vis. Spectroscopic, Thermal, and BET Studies of Magnesium Ion Doped Strontium Pyrophosphate Nano-Particles

Pyrophosphates are very useful as bioactive ceramics; particularly, calcium pyrophosphate has made impressive progress as biocompatible material promoting tissue formation. 2% Mg, 5% Mg, and 10% Mg ion doped SrPPi nano-particles are synthesized using a surfactant-mediated approach. The Powder XRD pattern confirms the tetragonal structure of materials and nano-structured in nature. The transmission Electron Microscopy (TEM) study confirmed the nano-size and the dimensions in the range from 7.46 nm to 51.70 nm. P-O-P and PO3 have both symmetric and asymmetric stretching vibrations, according to the FT-IR spectroscopy investigation. The direct optical energy band gap for 2% Mg, 5% Mg, and 10% Mg ion doped Sr2P2O7 samples is found to be 4.98 eV, 4.75 eV, and 4.55 eV using UV-NIR absorption spectroscopy, spanning the spectral range of 210–1200 nm. EDAX analysis confirmed the elemental presence. Thermogravimetric analysis proved that the sample included water molecules. According to TGA, the samples become anhydrous and almost remain stable when heated over 600 °C–1000 °C. Photoluminescence studies indicate the emission is in the visible range. BET analysis gives information on surface area and pore size.

Stepwise hydration of [CH3COOMg]+ studied by cold ion trap infrared spectroscopy: insights into interactions in the magnesium channel selection filters.

The magnesium channel controls Mg2+ concentration in the cell and plays an indispensable role in biological functions. The crystal structure of the Magnesium Transport E channel suggested that Mg2+ hydrated by 6 water molecules is transported through a selection filter consisting of COO- groups on two Asp residues. This Mg2+ motion implies successive pairing with -OOC-R and dissociation mediated by water molecules. For another divalent ion, however, it is known that RCOO-⋯Ca2+ cannot be separated even with 12 water molecules. From this discrepancy, we probe the structure of Mg2+(CH3COO-)(H2O)4-17 clusters by measuring the infrared spectra and monitoring the vibrational frequencies of COO- with the help of quantum chemistry calculations. The hydration by (H2O)6 is not enough to induce ion separation, and partially-separated or separated pairs are formed from 10 water molecules at least. These results suggest that the ion separation between Mg2+ and carboxylate ions in the selection-filter of the MgtE channel not only results from water molecules in their first hydration shell, but also from additional factors including water molecules and protein groups in the second solvation shell of Mg2+.

AMOEBA Force Field Trajectories Improve Predictions of Accurate pKa Values of the GFP Fluorophore: The Importance of Polarizability and Water Interactions.

Precisely quantifying the magnitude, direction, and biological functions of electric fields in proteins has long been an outstanding challenge in the field. The most widely implemented experimental method to measure such electric fields at a particular residue in a protein has been through changes in pKa of titratable residues. While many computational strategies exist to predict these values, it has been difficult to do this accurately or connect predicted results to key structural or mechanistic features of the molecule. Here, we used experimentally determined pKa values of the fluorophore in superfolder green fluorescent protein (GFP) with amino acid mutations made at position Thr 203 to evaluate the pKa prediction ability of molecular dynamics (MD) simulations using a polarizable force field, AMOEBA. Structure ensembles from AMOEBA were used to calculate pKa values of the GFP fluorophore. The calculated pKa values were then compared to trajectories using a conventional fixed charge force field (Amber03 ff). We found that the position of water molecules included in the pKa calculation had opposite effects on the pKa values between the trajectories from AMOEBA and Amber03 force fields. In AMOEBA trajectories, the inclusion of water molecules within 35 Å of the fluorophore decreased the difference between the predicted and experimental values, resulting in calculated pKa values that were within an average of 0.8 pKa unit from the experimental results. On the other hand, in Amber03 trajectories, including water molecules that were more than 5 Å from the fluorophore increased the differences between the calculated and experimental pKa values. The inaccuracy of pKa predictions determined from Amber03 trajectories was caused by a significant stabilization of the deprotonated chromophore's free energy compared to the result in AMOEBA. We rationalize the cutoffs for explicit water molecules when calculating pKa to better predict the electrostatic environment surrounding the fluorophore buried in GFP. We discuss how the results from this work will assist the prospective prediction of pKa values or other electrostatic effects in a wide variety of folded proteins.

Corrosion protection mechanisms of graphene oxide-reinforced polypropylene coating for mild carbon steel by advanced molecular dynamics simulations with emphasis on resistance to water and chloride ion penetration

Polypropylene can be used as a raw material for manufacturing corrosion-resistant coatings to protect the surface of the mild carbon steel substrate. To improve the properties of polypropylene (PP), graphene oxide (GO) can be added to the coating. In this research, molecular dynamics (MD) simulations were employed to evaluate the effect of GO additives on the PP coating using COMPASS Force-Filed of the Forcite module. The results of molecular modeling, such as mean square displacement (MSD), diffusion coefficient, concentration profile, and gyration radius (Rg), revealed that the permeability of corrosive agents, including water molecules and chloride ions in the composite coating (PP/GO), is much lower than pure one (PP). In addition, by reducing the surface energy from 77 to 68 mJ/m2, the water contact angle (WCA) is improved from 150◦ for the pure PP coating to 170◦ for the composite one. It can also be due to an 18% increase in system compaction in the presence of GO. In the other hand, the free fraction volume (FFV) in the presence of GO is reduced by about 4%. The adhesion of the coating to the mild carbon steel substrate has also been ameliorated by 38% for the PP/GO coating compared to the pure PP. Therefore, most of the simulated parameters reported the positive effects of compositing PP with GO.

Surface and Void Space Analysis of the Crystal Structures of Two Lithium Bis(pentafluoroethanesulfonyl)imide Salts

Analysis of two crystal structures of lithium bis(pentafluoroethanesulfonyl)imide is presented. Two orientations of the anion, that is a cis and trans orientation, are observed. Both structures exhibit unique interactions leading to the formation of discrete fluorous domains in the solid-state. A notable difference in the F···F interactions is seen when contrasting the two orientations wherein the trans geometry has a higher percentage of fluorine interactions than the cis orientation. The inclusion of water molecules in one of the structures also leads to the formation of a polar domain formed through a series of cyclical hydrogen bonding rings. The two structures allow for a detailed examination of the bond distances and angles involved in the formation of the two structures. Analysis of the void space in the two structures leads to the observation that the trans conformation exhibits notably higher void space as compared with the cis orientation. Hirshfeld surface analysis is used to help rationalize the interactions leading to unique changes in geometries and structure.

Controlling Plasmonic Chemistry Pathways through Specific Ion Effects

AbstractPlasmon‐driven dehalogenation of brominated purines has been recently explored as a model system to understand fundamental aspects of plasmon‐assisted chemical reactions. Here, it is shown that divalent Ca2+ ions strongly bridge the adsorption of bromoadenine (Br‐Ade) to Ag surfaces. Such ion‐mediated binding increases the molecule's adsorption energy leading to an overlap of the metal energy states and the molecular states, enabling the chemical interface damping (CID) of the plasmon modes of the Ag nanostructures (i.e., direct electron transfer from the metal to Br‐Ade). Consequently, the conversion of Br‐Ade to adenine almost doubles following the addition of Ca2+. These experimental results, supported by theoretical calculations of the local density of states of the Ag/Br‐Ade complex, indicate a change of the charge transfer pathway driving the dehalogenation reaction, from Landau damping (in the lack of Ca2+ ions) to CID (after the addition of Ca2+). The results show that the surface dynamics of chemical species (including water molecules) play an essential role in charge transfer at plasmonic interfaces and cannot be ignored. It is envisioned that these results will help in designing more efficient nanoreactors, harnessing the full potential of plasmon‐assisted chemistry.

Molecular dynamics simulation or structure refinement of proteins: are solvent molecules required? A case study using hen lysozyme

In protein simulation or structure refinement based on values of observable quantities measured in (aqueous) solution, solvent (water) molecules may be explicitly treated, omitted, or represented by a potential of mean-solvation-force term, depending on protein coordinates only, in the force field used. These three approaches are compared for hen egg white lysozyme (HEWL). This 129-residue non-spherical protein contains a variety of secondary-structure elements, and ample experimental data are available: 1630 atom–atom Nuclear Overhauser Enhancement (NOE) upper distance bounds, 213 3 J-couplings and 200 S2 order parameters. These data are used to compare the performance of the three approaches. It is found that a molecular dynamics (MD) simulation in explicit water approximates the experimental data much better than stochastic dynamics (SD) simulation in vacuo without or with a solvent-accessible-surface-area (SASA) implicit-solvation term added to the force field. This is due to the missing energetic and entropic contributions and hydrogen-bonding capacities of the water molecules and the missing dielectric screening effect of this high-permittivity solvent. Omission of explicit water molecules leads to compaction of the protein, an increased internal strain, distortion of exposed loop and turn regions and excessive intra-protein hydrogen bonding. As a consequence, the conformation and dynamics of groups on the surface of the protein, which may play a key role in protein–protein interactions or ligand or substrate binding, may be incorrectly modelled. It is thus recommended to include water molecules explicitly in structure refinement of proteins in aqueous solution based on nuclear magnetic resonance (NMR) or other experimentally measured data.

Giant Ln 30 -Cluster-Embedded Polyoxotungstate Nanoclusters with Exceptional Proton-Conducting and Luminescent Properties

Giant Ln ₃₀ -Cluster-Embedded Polyoxotungstate Nanoclusters with Exceptional Proton-Conducting and Luminescent Properties

Sodium and Potassium tert-Butyl Peroxide Hydrates: Crystal Structure and Properties

Sodium and potassium tert-butyl peroxide hydrates 2Na+·2C4H9{text{O}}_{2}^{ - }·7H2O (I) and 2K+· 2C4H9{text{O}}_{2}^{ - }·4H2O (II) were prepared. According to X-ray diffraction data (CIF files CCDC no. 2081025 (I) and no. 2081024 (II)), the compounds are coordination polymers in which alkali metal atoms have C.N.(Na) of 6 or C.N.(K) of 6 and 8. The crystal packings comprise layers with clearly defined hydrophobic surfaces consisting of hydrocarbon groups and hydrophilic inner areas including water molecules, alkali metal cations, and peroxy groups of the tert-butyl peroxide anions. Compounds were characterized by vibrational spectroscopy, 1H, 13C NMR spectroscopy, thermogravimetry, and differential scanning calorimetry.

Square network based upon the molecular salt of the tetraprotonated photoproduct rtct-tetrakis(pyridin-4-yl)cyclobutane and the sulfate anion.

The formation and crystal structure of a hydrated molecular salt that results in a square network is reported. The crystalline solid is based upon the tetraprotonated photoproduct rtct-tetrakis(pyridin-4-yl)cyclobutane (4H-rtct-TPCB)4+ along with two sulfate anions (SO42-) and eight waters of hydration, namely, 4,4',4'',4'''-(cyclobutane-1,2,3,4-tetrayl)tetrapyridinium bis(sulfate) octahydrate, C24H24N44+·2SO42-·8H2O. The fully protonated photoproduct acts as a four-connecting node within the square network by engaging in four charge-assisted N+-H...O hydrogen bonds to the sulfate anion. The observed hydrogen-bonding pattern in this square network is akin to T-silica, which is a metastable form of SiO2. The included water molecules and sulfate anions engage in numerous O-H...O hydrogen bonds to form various hydrogen-bonded ring structures.

Molecular Origin for Strong Agarose Gels: Multi-Stranded Hydrogen Bonding

Agarose gels are currently used in separation, purification, and characterization of DNA, RNA, proteins, and polysaccharides in gel electrophoresis, gel filtration, affinity chromatography, and ion chromatography techniques. Specifically, it is used in PCR (Polymerase Chain Reaction) test. Although, double stranded intermolecular hydrogen bonding between OH-2 and 3,6-ring oxygen atoms of 1,4-linked anhydro-α-L-galactopyranose residues on different molecules take place, triple- or multi-stranded secondary association occur with increasing concentration. The multi-stranded gelation mechanism of agarose molecules is the first to report. The associated agarose molecules play a dominant role in the centre of tetrahedral cavities that are occupied by ice-like hydrogen bonded water molecules which are caused thermodynamically by cage and hydrophobic effects. Many investigations the gelling properties of the polysaccharides have been undertaken to elucidate the structure-function relationship, but no other researchers have established the mechanisms at the molecular level including water molecules. There are structural and theoretical consistencies in our investigation. This paper provides important information not only academia, but also to industrial fields, such as bio-physicochemical analysis, food, cosmetics, agriculture, pharmaceuticals, drug delivery, drug storage, tissue engineering, and biotechnology.

Solubility and Aggregation of Selected Proteins Interpreted on the Basis of Hydrophobicity Distribution.

Protein solubility is based on the compatibility of the specific protein surface with the polar aquatic environment. The exposure of polar residues to the protein surface promotes the protein’s solubility in the polar environment. The aquatic environment also influences the folding process by favoring the centralization of hydrophobic residues with the simultaneous exposure to polar residues. The degree of compatibility of the residue distribution, with the model of the concentration of hydrophobic residues in the center of the molecule, with the simultaneous exposure of polar residues is determined by the sequence of amino acids in the chain. The fuzzy oil drop model enables the quantification of the degree of compatibility of the hydrophobicity distribution observed in the protein to a form fully consistent with the Gaussian 3D function, which expresses an idealized distribution that meets the preferences of the polar water environment. The varied degrees of compatibility of the distribution observed with the idealized one allow the prediction of preferences to interactions with molecules of different polarity, including water molecules in particular. This paper analyzes a set of proteins with different levels of hydrophobicity distribution in the context of the solubility of a given protein and the possibility of complex formation.

Structural variation of protein-ligand complexes of the first bromodomain of BRD4.

The bromodomain-containing protein 4 (BRD4), a member of the bromodomain and extra-terminal domain (BET) family, plays a key role in several diseases, especially cancers. With increased interest in BRD4 as a therapeutic target, many X-ray crystal structures of the protein in complex with small molecule inhibitors are publicly available over the recent decade. In this study, we use this structural information to investigate the conformations of the first bromodomain (BD1) of BRD4. Structural alignment of 297 BRD4-BD1 complexes shows a high level of similarity between the structures of BRD4-BD1, regardless of the bound ligand. We employ WONKA, a tool for detailed analyses of protein binding sites, to compare the active site of over 100 of these crystal structures. The positions of key binding site residues show a high level of conformational similarity, with the exception of Trp81. A focused analysis on the highly conserved water network in the binding site of BRD4-BD1 is performed to identify the positions of these water molecules across the crystal structures. The importance of the water network is illustrated using molecular docking and absolute free energy perturbation simulations. 82% of the ligand poses were better predicted when including water molecules as part of the receptor. Our analysis provides guidance for the design of new BRD4-BD1 inhibitors and the selection of the best structure of BRD4-BD1 to use in structure-based drug design, an important approach for faster and more cost-efficient lead discovery.

A Distinct Motif in a Prokaryotic Small Ras-Like GTPase Highlights Unifying Features of Walker B Motifs in P-Loop NTPases

A hallmark of the catalytically essential Walker B motif of P-loop NTPases is the presence of an acidic residue (aspartate/glutamate) for efficient Mg2+ coordination. Although the Walker B motif has been identified in well-studied examples of P-loop NTPases, its identity is ambiguous in many families, for example, in the prokaryotic small Ras-like GTPase family of MglA. MglA, belonging to TRAFAC class of P-loop NTPases, possesses a threonine at the position equivalent to Walker B aspartate in eukaryotic Ras-like GTPases. To resolve the identity of the Walker B residue in MglA, we carried out a comprehensive analysis of Mg2+ coordination on P-loop NTPase structures. Atoms in the octahedral coordination of Mg2+ and their interactions comprise a network including water molecules, Walker A, Walker B and switch motifs of P-loop NTPases. Based on the conserved geometry of Mg2+ coordination, we confirm that a conserved aspartate functions as the Walker B residue of MglA, and validate it through mutagenesis and biochemical characterization. Location of the newly identified aspartate is spatially equivalent to the Walker B residue of the ASCE division of P-loop NTPases. Furthermore, similar to the allosteric regulation of the Walker B aspartate conformation in MglA, we identify protein families in which large conformational changes involving Walker B motif potentially function as allosteric regulators. The study unravels conserved features of Mg2+ coordination among divergent families of P-loop NTPases, especially between ancient Ras-like GTPases and ASCE family of ATPases. The conserved geometric features provide a foundation for design of nucleotide-hydrolyzing enzymes.

IMPROVING STRENGTH OF HOT-ROLLED PIPES IN OIL AND GAS PIPELINE TRANSPORTATION SYSTEMS AND HEAT SUPPLY SYSTEMS

Purpose. Development of new anticorrosion treatment technologies including prevention of inter-crystalline corrosion propagation inside the solid material in order to increase hot-rolled pipes life.Methodology. Based on the analysis of pipes manufacture and operation conditions, the main reason for reduction of the life of oil and gas transport pipelines made of hot-rolled pipes has been defined to be the poor corrosion resistance, which consequently causes propagation of fatigue processes. In course of theoretical and practical studies, one of the reasons for low corrosion resistance was revealed – complete absence of anticorrosion treatment inside the solid metal in order to prevent propagation of dangerous inter-crystalline corrosion.Results. Based on the conducted experimental studies, practices have been developed to carry out anticorrosion treatment inside the solid material by ensuring feeding of the inhibitor in ionic form into the solid material. This is done through plastic flow deformation of the material with grain refinement. As a result, mobility of grains and their fragments under conditions of deformation cause formation of "conductance channels", along which the inhibitor ions are transported to the solid material under the influence of electrostatic fields of the natural or, if necessary, artificial background. The most important result of this is the inhibitory treatment of the grains surface inside the solid material with prevention of electrochemical inter-crystalline corrosion propagation.Originality. Based on the practical works, anticorrosion treatment inside the solid material has been carried out for the first time, thereby eliminating the extremely dangerous inter-crystalline corrosion that latently propagates inside the solid material. A prerequisite for transportation of the inhibitor in ionic form inside the solid material are numerous examples of various elementary formations movements inside the solid body of material. This fact can be confirmed by inter-crystalline corrosion propagation in the solid material that generates in the manner of electrochemical corrosion, i.e. with water involved. This suggests the presence of water molecules in the solid material and possible channels of its penetration into the solid body. Many other examples can be given; their analysis reveals a common feature – in all cases there is an electrical nature, including water molecules that have an electrical dipole moment. Another precondition for the possibility of the inhibitor transportation is the presence of transportation channels. They are formed of free volumes, that are characteristic for crystalline structures, and volumes generated as a result of plastic flow deformation. The third precondition for the inhibitor ions transportation inside the solid material is the presence of driving forces; the forces of the electrical nature act in this case, ensuring "instantaneous" movements of micro-objects. Their source is the electrostatic fields of the material being the result of a large number of potential differences arising from the numerous and diverse inhomogeneities of materials. They form the natural electrostatic background, which ensures movement of micro-objects in the "solid body" of the material in vivo. If necessary, it can be supplemented with the artificial electrostatic background created by a grinding brush that removes scale from the pipe surface.Practical implications. The deterioration degree of operated pipeline systems is high; the required amount of repair work significantly exceeds the scope of work for the newly constructed systems. A similar situation both in terms of operating conditions and in technical state is with heating pipeline systems, also being of great length. Failures in operation of both abovementioned systems due to their underground laying bring high economic losses; the same is in case of their repair. For these reasons, extension of hot-rolled pipes service life is of great economic importance, which is hard to overestimate.

Excision of 5-Carboxylcytosine by Thymine DNA Glycosylase.

5-Methylcytosine (mC) is an epigenetic mark that is written by methyltransferases, erased through passive and active mechanisms, and impacts transcription, development, diseases including cancer, and aging. Active DNA demethylation involves TET-mediated stepwise oxidation of mC to 5-hydroxymethylcytosine, 5-formylcytosine (fC), or 5-carboxylcytosine (caC), excision of fC or caC by thymine DNA glycosylase (TDG), and subsequent base excision repair. Many elements of this essential process are poorly defined, including TDG excision of caC. To address this problem, we solved high-resolution structures of human TDG bound to DNA with cadC (5-carboxyl-2'-deoxycytidine) flipped into its active site. The structures unveil detailed enzyme-substrate interactions that mediate recognition and removal of caC, many involving water molecules. Importantly, two water molecules contact a carboxylate oxygen of caC and are poised to facilitate acid-catalyzed caC excision. Moreover, a substrate-dependent conformational change in TDG modulates the hydrogen bond interactions for one of these waters, enabling productive interaction with caC. An Asn residue (N191) that is critical for caC excision is found to contact N3 and N4 of caC, suggesting a mechanism for acid-catalyzed base excision that features an N3-protonated form of caC but would be ineffective for C, mC, or hmC. We also investigated another Asn residue (N140) that is catalytically essential and strictly conserved in the TDG-MUG enzyme family. A structure of N140A-TDG bound to cadC DNA provides the first high-resolution insight into how enzyme-substrate interactions, including water molecules, are impacted by depleting the conserved Asn, informing its role in binding and addition of the nucleophilic water molecule.

Theoretical study of the stability and NMR spectroscopic properties of vanadium(V) complexes

Several vanadium(V) complexes have been investigated as possible antidiabetic and anticancer therapeutic agents. Among these, vanadium(V) complexes linked to tridentate ONO Schiff bases stand out for their potential in the treatment for cancer. However, further studies are necessary in order to learn about their specific action at the cellular level. We investigate structural and spectroscopic properties of these particular complexes, which are formed by a Schiff base linked to a [VO2]+ ion that contains different functional groups. Molecular structure optimizations of these vanadium-containing complexes were performed by the ONIOM (QM1:QM2) method, where the high layer (complexes) were described by density functional theory methods whereas the low layer (eight water molecules) were described by the HF approach. Various solvation models were utilized; however, the introduction of both implicit (using a solvation model based on density, SMD) and explicit (eight water molecules) solvation improves the stability of the systems. Interestingly, we found that the location of the explicit water molecules in the different octahydrated vanadium complexes was conserved surrounding the oxo-vanadate moiety. A detailed analysis of the chemical shift (δ) values for 1H, 13C and 51V is presented based on the ONIOM optimized geometries using the gauge-independent atomic orbital methodology. For obtaining accurately chemical shifts, the complete basis set using the correlation-consistent Dunning basis sets from double-ξ to quadruple-ξ and the Ahlrichs basis set were utilized. The results from the methodology presented here are consistent with those reported experimentally for 1H. Again, the inclusion of explicit water molecules in the inner solvation shell during the calculation of the chemical shifts was crucial. The analysis of solvation energies also indicates the relevance of including explicit water molecules as the main stabilization factor suggesting the central role of intermolecular interaction in the stability of the metallic complexes. From this analysis, a possible vanadium complex candidate for further evaluation in the cellular environment is suggested. This work not only provides evidence of a suitable methodology for studying the structural and spectroscopic properties of vanadium complexes but also highlights the relevance of explicitly including water molecules in their inner shell.

Water in Ras Superfamily Evolution.

The Ras GTPase superfamily of proteins coordinates a diverse set of cellular outcomes, including cell morphology, vesicle transport, and cell proliferation. Primary amino acid sequence analysis has identified Specificity determinant positions (SDPs) that drive diversified functions specific to the Ras, Rho, Rab, and Arf subfamilies (Rojas et al. 2012, J Cell Biol 196:189-201). The inclusion of water molecules in structural and functional adaptation is likely to be a major response to the selection pressures that drive evolution, yet hydration patterns are not included in phylogenetic analysis. This article shows that conserved crystallographic water molecules coevolved with SDP residues in the differentiation of proteins within the Ras superfamily of small GTPases. The patterns of water conservation between protein subfamilies parallel those of sequence-based evolutionary trees. Thus, hydration patterns have the potential to help elucidate functional significance in the evolution of amino acid residues observed in phylogenetic analysis of homologous proteins. © 2019 Wiley Periodicals, Inc.