Associate Hydrations and Energies of Nucleotide Bases as Revealed by Low-Temperature Field Ionization Mass-Spectrometric Data

Abstract

The formation of water clusters, polyhydrates of nucleotide bases and their associates during simultaneous condensation of water and base molecules in vacuo onto a surface of a needle emitter cooled to 170 K was studied by field ionization mass spectrometry. It was found that different emitter temperatures are characterized by a specific distribution of intensities of cluster currents, depending on the number of water molecules in clusters. These distributions correlate with structural peculiarities and the relative energetics of formation of water clusters, polyhydrates of nucleotide bases and their associates at low temperature. The features observed in mass spectra for clusters m⁹Ade (H₂O)₅, m¹Ura (H₂O)₄ and m⁹Ade m¹Ura (H₂O)₂ are treated as a result of formation of energetically favorable structures stabilized by H-bonded bridges of water molecules.

The relative association constants and formation enthalpies of the noncomplementary pairs Ade Cyt, Gua Ura and the associates which model the aminoacid-base complexes m¹Ura Gin and m₂ ^1,3Thy Gin were determined from the temperature dependencies of the intensities of mass spectra peaks in the range 290–320 K.     

Hydration of complementary 9-methyladenine.1-methyluracil pairs at low temperatures according to data from field mass spectrometry

The hydration of nucleotide bases of m9Ade(A), m1Ura(U) and a complementary pair A.U was studied by field ionization mass-spectrometry at room and low (170 K) temperatures in vacuum. Enthalpies of A.U-pair formation and its monohydrate A.U(H2O) were measured using temperature dependences of association constants. From the analysis of intensities of mass-spectrum peaks, corresponding to monohydrates U(H2O), A(H2O), A.U(H2O), A.U-pair and initial components A, U, and also measured enthalpies it is supposed that monohydration of bases A and U essentially prevents the formation of the coplanar pair A.U. A qualitative information about the structure and energetics of hydrate clusters A(H2O)n, U(H2O)n and A.U(H2O)n for n = 1 divided by 7 was obtained from low temperature mass-spectra. The observed peculiarities in hydrate structures A(n = 5), U(n = 4), A.U(n = 4) are treated as a consequence of cyclization of water molecules around bases.     

Experimental and theoretical study of energetics of complex formation between nucleic acid bases and the bases with amide group.

A number of nucleic acid base pairs and complexes between the bases and the amide group of acrylamide have been studied experimentally by using mass spectrometry and theoretically by the method of atom-atom potential function calculations. It has been found from temperature dependencies of peak intensities in mass spectra of m2.2.9(3) Gua.m1Ura, m9 Ade.m1Cyt, m2.2.9(3) Gua.m1Gua.m1Cyt pairs that enthalpy values, delta H, of the complex formation are equal to 14.2 +/- 1.1, 13.5 +/- 1.3 and 16.4 +/- 1.4 kcal/M, respectively, and those of acrylamide with m1.3(2) Ura and m1Thy corresponds to 9.7 +/- 1.0 and 6.8 +/- 0.6 kcal/M. There is a good agreement of the experimental data with calculations when taking into account both the amino-oxo and the amino-hydroxy tautomeric forms of guanine. A combined use of the data allows us to determine the energy, the modes of interaction and the structure of the complexes. The results are discussed in connection with the modelling of molecular structure of biopolymers by the method of classical potential functions, protein-nucleic acids recognition and fidelity of nucleic acids biosynthesis.     

Mass-spectrometric investigations on hydration of nucleic acid components in vacuum

Association reactions between water and alkylated uracils. occurring under field-ionization conditions in a mass spectrometer at the tungsten point emitter surface, were studied at several temperatures. The origin of peaks observed in the mass spectra at m/e ratios corresponding to M+H and M+H-H2O were attributed to M-H2O and M-(H2O)2 hydrates, respectively, hydrogen-bonded via carbonyl groups of the diketopyrimidines (M) investigated. The appearance of these ions is explained in terms of the field-ionization mechanism of the neutral hydrates involving intramolecular H+ transfer and concomitant release of the OH+ radical. Measurements of the relative peak intensities allowed the calculation of apparent equilibrium constants. K(ass). for the association reactions, and hence the respective van't Hoff enthalpies of hydrat'on. The latter are discussed in connection with the available quantum-mechanical hydration energies for specific groups of respective canonical nucleic acid bases and experimental enthalpies of hydration of alkylated uracils with water. Specific hydration is estimated to contribute about 15-20% to the total enthalpy of interaction of the solutes with their hydration shells.     

C-H ... O hydrogen bonding in solutions of methylated nucleic acid base analogs as revealed by NMR

Formation and thermodynamic characteristics of C-H ... O hydrogen bonding of methylated uracils and caffeine have been studied by nmr along two lines. 1. The concentration and temperature dependencies of the PMR spectra of 1,3-dimethyluracil (m2 1,3Ura), 1,3-dimethylthymine (m2 1,3Thy), and 1,3,6-trimethyluracil (m3 1,3,6Ura) in chloroform at high concentrations of base analogs indicated the self-association of m2 1,3Ura and m2 1,3Thy via C(6)H ... O hydrogen bonding and the competitive formation of C-H ... O bonds between carbonyl oxygens and chloroform. The intermolecular interaction energy and the arrangement of molecules in the local minima of various m2 1,3Ura dimers were calculated by the method of atom-atom potentials. The deepest minimum for the m2 1,3Ura coplanar dimer corresponds to a C(6)-H ... O hydrogen-bond formation. 2. At low concentration of m2 1,3Ura and caffeine in CCl4, C(6)-H ... O bonding for m2 1,3Ura and C(8)-H ... O bonding for caffeine with oxygens of dimethyl sulfoxide (DMSO) and acetone were observed. The association constants of these complexes were obtained at different temperatures. The enthalpies delta H, of the m2 1,3Ura-DMSO, m2 1,3Ura-accetone, caffeine-DMSO, and caffeine-acetone complexes were -2 +/- 0.1 kcal/mol. The calculations showed that the deepest minimum of the caffeine-acetone coplanar complex corresponds to C(8)-H ... O bonding with energy of -3.5 kcal/mol and that of the m2 1,3Ura-acetone complexes corresponds to C(6)-H ... O bonding with energy of -3.4 kcal/mol. The approximate correction for the solvent effect provides good agreement of the experimental data with the calculations.     

Mass-spectrometric investigations on hydration of nucleic acid components in vacuum. II. N-methylated adenines

Association reactions between water and N-methylated adenines (M), occurring under field-ionization conditions in a mass spectrometer at the tungsten point emitter surface, were studied at a number of temperatures. The origin of the peaks observed in the mass spectra at m/e ratios corresponding to MH+ was assigned to M X H2O monohydrates , of those corresponding to (MH X H2O)+ and (MH2)2+ to double hydrates M(H2O)3. Measurements of the relative peak intensities allowed calculation of apparent equilibrium constants, Kass, for successive hydration steps, and hence the respective van't Hoff enthalpies of hydration. Both the equilibrium and the energy parameters obtained support the available quantum-mechanical single-layer hydration schemes of adenine and of its N-methylated derivatives.     

Active internal waters in the bacteriorhodopsin photocycle. A comparative study of the L and M intermediates at room and cryogenic temperatures by infrared spectroscopy

We present time-resolved room-temperature infrared difference spectra for the bacteriorhodopsin (bR) photocycle at 8 cm (-1) spectral and 5 micros temporal resolution, from 4000 to 800 cm (-1). An in situ hydration method allowed for a controlled and stable sample hydration (92% relative humidity), largely improving the quality of the data without affecting the functionality of bR. Experiments in both H 2 (16)O and H 2 (18)O were conducted to assign bands to internal water molecules. Room-temperature difference spectra of the L and M intermediates minus the bR ground state (L-BR and M-BR, respectively) were comprehensively compared with their low-temperature counterparts. The room-temperature M-BR spectrum was almost identical to that obtained at 230 K, except for a continuum band. The continuum band contains water vibrations from this spectral comparison between H 2 (16)O and H 2 (18)O, and no continuum band at 230 K suggests that the protein/solvent dynamics are insufficient for deprotonation of the water cluster. On the other hand, an intense positive broadband in the low-temperature L-BR spectrum (170 K) assigned to the formation of a water cavity in the cytoplasmic domain is absent at room temperature. This water cavity, proposed to be an essential feature for the formation of L, seems now to be a low-temperature artifact caused by restricted protein dynamics at 170 K. The observed differences between low- and room-temperature FTIR spectra are further discussed in light of previously reported dynamic transitions in bR. Finally, we show that the kinetics of the transient heat relaxation of bR after photoexcitation proceeds as a thermal diffusion process, uncorrelated with the photocycle itself.     

Thermochemistry of aqueous solutions of alkylated nucleic acid bases. I. Apparent molar heat capacities of uracil, thymine and their derivatives

Apparent molar heat capacities phiC(p(1,3)) of uracil, thymine and a series of their alkylated derivatives: m(1)Ura,m(1,3)(2) Ura, m(1,3)(2)Thy, mi(1,3,6)(3)Ura, m(1,3)(2),e(5)Ura and e(1,3)(2)Thy in dilute aqueous solutions were measured in the temperature range of 293.15-388.15 K, using a differential adiabatic scanning microcalorimeter. They were found to lie (i) much higher than the estimated heat capacities C(p)(s) of solid compounds, (ii) comparable with the respective partial molar heat capacities at infinite dilution, C(o)(p2), and (iii) linearly related to the number nH of hydrogen atoms covalenuy bound to the solute molecules. The increment thus obtained DeltaC(o)(p2)=42.8 J mole(-1) K(-1)n(-1)(H) per each hydrogen atom at 298.15 K proved (i) to coincide closely with those found previously for homologous series of aliphatic amides and hydrocarbons, and (ii) to decrease with a rise of temperature. These findings imply the involvement of hydrophobic hydration of the solutes.     

Formation and removal of DNA adducts after treatment of Chinese hamster ovary cells with N-methyl- and N-ethyl-N-nitrosourea

We have studied formation and stability of alkylguanines following treatment of Chinese hamster ovary cells with either N-[3H]methyl-N-nitrosourea (MeNOUr) (applied at 50 microM and 40 microM concentrations) or N-[3H]ethyl-N-nitrosourea (EtNOUr) (applied at 43.1 microM). Analyses of acid hydrolysates of the methylated DNA revealed that 9.3% and 57.0% of the total DNA were O6-methylguanine (m6Gua) and 7-methylguanine (m7Gua), respectively. Analysis of enzymic hydrolysate resulted in 8.2% m6Gua and 50.3% m7Gua. For ethylation, the % of ethylated purines identified as O6-ethylguanine (e6Gua) and 7-ethylguanine (e7Gua) were 20.4% and 31.3%, respectively. Half-lives of the main alkylated purines were determined by analysing DNA of dividing cultures over a time interval of 48 h after treatment with carcinogens. Half-lives measured for methylated DNA bases were: m1Ade, 20.6 h; m3Ade, 25.5 h; m7Ade, 0.9 h; m3Gua, 1.1 h; m6Gua, infinity; m7Gua, 39.1 h. Determinations at the level of deoxyribonucleosides resulted in similar half-lives: m3dA, 15.2 h; m7dA, 2.7 h; m3dG, 2.3 h; m6dG, 224 h; m7dG, 25.6 h. The corresponding values for ethylated purines were: e3Ade, 2.9 h; e7Ade, 7.1 h; e3Gua, 1.4 h; e6Gua, infinity; e7Gua, 42.6 h. The relatively high yields of the premutagenic m6Gua and e6Gua, and their long half-lives (greater than or equal to 224 h) are consistent with the suggestion that these adducts play a dominant role in mutation induction at the hypoxanthine-guanine phosphoribosyltransferase (hgprt) locus in CHO cells.     

Determination of the configuration of epimeric diols of vitamin D3 series by mass spectrometry.

The mass spectral elimination of water in epimeric 1,3-diols of vitamin D3 (colecalciferol) series has been investigated. It was found that the mass spectra of these steroisomers differ sharply in the relative intensities of the ions M-H2O (m/e 382) and a-H2O (m/e +/- 34), where ion a (formed via formal cleavage of the 7, 8-double bond) is characteristic of vitamin D3 and its derivatives. So while epimeric 1, 3-diols of vitamin D3 series have very close UV and NMR characteristics, the comparison of the ratios of the peaks M-H2O and M.+, a-H2O and a, respectively, makes it possible to distinguish between stereoisomeric 1 alpha, 3 beta-, 1 beta, 3 beta-, 1 alpha, 3 alpha- and 1 beta, 3 alpha-diols using their mass spectra.     

Interaction of nucleic acid bases with water molecules and formation of mismatched nucleotide pairs

The possibility of the inclusion of water molecules in the formation of mismatched nucleotide pairs was considered in relation to the mechanisms of point errors in template directed biosynthesis. Calculations of the intermolecular interaction energy for systems containing two bases and one water molecule were carried out by the method of atom-atom potential functions. There exist energy minima for each base pair, corresponding to a single N--H...O or N--H...N H-bond between the bases and H-bonding of the water molecule with both bases. The relative positions of glycosyl bonds in some of these minima are closer to those for Watson--Crick pairs, than the positions of minima for these pairs without water. For other minima, the H-bond formation between the water molecule and the two bases additionally stabilizes the relative base position in wobble-pairs with two H-bonds between the bases. The base and water positions in energy minima are compared with the positions in some pairs proposed on the basis of NMR and X-ray data for double helical oligonucleotides.     

Variable temperature infrared spectroscopy of cytosine-guanine base pairs: tautomerism versus polarization.

This report describes an infrared (IR) spectroscopic study of a model cytosine-guanine base pair. This base pair is part of a self-consistent experimental system based on lipophilic ribose derivatives of cytidine (C), guanosine (G) and O6-methylguanosine (O6MeG) that are soluble in non-aqueous, low dielectric solvents at appreciable concentrations. Previous experiments on this system have revealed different rotation dynamics for the amino bonds within the CG base pair, an observation that could be explained by the presence of rare tautomers (P.O. Lowdin, Reviews of Modern Physics 35,724 (1963)), or by mutual polarization of the base pairs (L.D. Williams, N.G. Williams and B.R. Shaw,J.Am.Chem.Soc. 112,829 (1990)). The IR spectra in the OH and NH stretching region indicate formation of hydrogen-bonded CG base pairs and self associates in 1,2-dichlorobenzene over a temperature range from 10 to 290K. Changes in the lineshapes and intensities of the IR bands with temperature correlate with phase transitions of the solvent, but no evidence is seen for an OH stretching band that would indicate the formation of hydroxyl tautomers within base pairs. Similarly, the relative intensities of the C = O stretching bands of CG in cyclohexane solution remain constant over this same temperature range, confirming that within the base pair, the tautomeric states of the bases remain essentially unperturbed in the 2-amino/6-keto form of G and the 2-keto/4-amino form of C. The spectra of O6-MeG aid in the band assignments, since this molecule is frozen in an equivalent of the 2-amino/6-hydroxyl tautomer, but without the OH group and its associated stretching band. We conclude that the probability of tautomerism does not appear to be sufficient to explain the different rotation dynamics for the two amino bonds of the CG base pair. Rather it is argued that mutual polarization within the base pair, which would increase the bond order of the amino bond of C within the base pair, can explain the results without the formation of unconventional tautomers.     

Base-specific binding of copper(II) to Z-DNA. The 1.3-A single crystal structure of d(m5CGUAm5CG) in the presence of CuCl2

The single crystal structure of d(m5CGUAm5CG) soaked with copper(II) chloride was solved to atomic (1.3 A) resolution to study the base specificity of copper binding to double-stranded DNA. In the present copper(II) chloride-soaked structure, four crystallographically unique copper(II) complexes were observed bound to five of the six purine bases in the hexamer duplex. Covalent copper(II) binding occurred at N-7 of all four guanine bases and at one of the two adenine bases in the DNA duplex. Copper binding was not observed at the position (Ade4) located in an open solvent channel, whereas the second adenine site (Ade10) shared a complex with a guanine residue (Gua12) of a neighboring symmetry-related hexamer. The coordination geometries and distribution of these copper(II) complexes at the guanine bases in the crystal were comparable to the analogous sites in the isomorphous copper(II) chloride-soaked d(CGCGCG) crystal (Kagawa, T., Geierstanger, B. H., Wang, A. H.-J., and Ho, P.S. (1991) J. Biol. Chem. 266, 20175-20184). Thus, the decreased copper(II) binding affinity for Ade4 was not an artifact of crystal packing, but is intrinsic to the chemical properties of this purine base in duplex DNA. This suggests that the adenine bases in dilute solutions of Z-DNA and more generally other duplex DNA conformations are not susceptible to copper(II) modification. Thus, preferential copper(II) binding at guanine bases over adenine bases in double-stranded DNA may explain the observed specificity of copper(II)-induced oxidative DNA damage near guanine residues (Yamamoto, K., and Kawanishi, S. (1989) J. Biol. Chem. 264, 15435-15440; Sagripanti, J.-L., and Kraemer, K. H. (1989) J. Biol. Chem. 264, 1729-1734). The sharing of a single copper(II) complex by Ade10 and Gua12 of an adjacent hexamer suggests that additional and perhaps specific DNA-DNA interactions, as may be found in the densely packed environment of the nuclear matrix in the cell, may render N-7 of adenine bases prone to copper(II) modification.     

UV spectra of adenine methyl and glycosyl derivatives and their transformation induced by amino acid carboxylic groups

UV absorption spectra of adenine, adenosine and their methyl derivatives were studied in dimethylsuloxide (DMSO). Considerable changes in UV spectra of adenine under methylation at the 1 and 3 positions, and adenosine under methylation at the 1 position attested the essential structural reconstruction of adenine purine ring. Ade and m6Ade were shown to form complexes with deprotonated carboxylic group of amino acids (carboxylate-ion) through two H-bonds involving amino group and N7H imino group, tautomeric transition N9H-->N7H being initiated namely by interaction with carboxylate-ion. Considerable changes in UV spectra of m1Ade, m1A, and m3Ade under interaction with neutral carboxylic group of amino acids were interpreted as a result of proton transfer from amino acid to the base.     

Mass spectrometric profiling of glucosamine, glucosamine polymers and their catecholamine adducts. Model reactions and cuticular hydrolysates of Toxorhynchites amboinensis (Culicidae) pupae.

Glucosamine (Gln), glucosamine polymers, and their catecholamine adducts were characterized using positive ion electrospray mass spectrometry (ESMS) and tandem mass spectrometry (ESMS-MS). N-acetyldopamine (NADA), a catecholamine found in many insect cuticles, was oxidized using mushroom tyrosinase, and the resulting quinone derivatives were reacted with Gln, (Gln)3, and polymeric glucosamine (chitosan). Adducts of glucosamine and its trisaccharide with NADA were readily identified as [M + H]+ ions in ESMS spectra, and ESMS-MS of selected ions confirmed the condensation of 1-3 NADA residues with Gln. In addition to Gln modification by the quinone derivatives of NADA, other spectra were consistent with the formation of adducts with N-acetylnoradrenaline and moieties formed by intramolecular cyclization following oxidation. The primary amine of glucosamine was involved in initial adduct formation, but the sites for subsequent additions of oxidized NADA to glucosamine, presumably via hydroxyl groups, could not be identified by ESMS alone. The ESMS spectra of chitosan films infused into the spectrometer following solubilization in acidic methanol/water produced spectra similar to that of (Gln)3 up to m/z 502. Ions of gradually decreasing intensity consistent with (Gln)x, where x = 4-8, were observed. Modification of chitosan films following incubation with NADA plus tyrosinase rendered the films insoluble in dilute acid, simulating the cross-linking process proposed to occur during insect cuticle sclerotization. Acid hydrolysates of the pupal stage of the mosquito Toxorhynchites amboinensis, using only two pupal exuviae for the hydrolyses, were infused into the mass spectrometer without preliminary chromatography. Eight amino acids, glucosamine, N-acetylglucosamine, catecholamines, and a variety of polymers incorporating these compound classes were identified.     

Investigation of the distribution of water clusters in vegetables, fruits, and natural waters by flicker noise spectroscopy

The distribution of water clusters in fresh rain water and in rain water that was aged for 30 days (North Germany, 53 degrees 33' N, 12 degrees 47' E, 293 K, rain on 25.06.06) as well as in fresh vegetables and fruits was studied by flicker noise spectroscopy. In addition, the development of water clusters in apples and potatoes during ripening in 2006 was investigated. A different distribution of water clusters in irrigation water (river and rain) and in the biomatrix of vegetables (potatoes, onions, tomatoes, red beets) and fruits (apples, bananas) was observed. It was concluded that the cluster structure of irrigation water differs from that of water of the biomatrix of vegetables and fruits and depends on drought and the biomatrix nature. Water clusters in plants are more stable and reproducible than water clusters in natural water. The main characteristics of cluster formation in materials studied were given. The oscillation frequencies of water clusters in plants (biofield) are given at which they interact with water clusters of the Earth hydrosphere. A model of series of clusters 16(H2O)100 <--> 4(H2O)402 <--> 2(H2O)903 <--> (H2O)1889 in the biomatrix of vegetables and fruits was discussed.     

Aromaticity of azines through dyotropic double hydrogen transfer reaction

The thermodynamic stabilities and IR spectra of the three water clusters (H₂O)_20, (H₂O)_54,, and (H₂O)₁₀₀ are studied by quantum-chemical computations. After full optimization of the (H₂O)_20,54,100 structures using the hybrid density functional B3LYP together with the 6-31+G(d,p) basis set, the electronic energies, zero-point energies, internal energies, enthalpies, entropies, and Gibbs free energies of the water clusters at 298 K are investigated. The OH stretching vibrational IR spectra of (H₂O)_20,54,100 are simulated and split into sub-spectra for different H-bond groups depending on the conformations of the hydrogen bonds. From the computed spectra the different spectroscopic fingerprint features of water molecules in different H-bond conformations in the water clusters are inferred.     

Metal-ion interactions with sugars. The crystal structure and FTIR study of an SrCl2-fructose complex

The single-crystal structure of SrCl2 x 2C6H12O6 x 3H2O was determined with Mr = 572.88, a = 16.252, b = 7.941(2), c = 10.751(3) angstroms, beta = 127.652(4) degrees, V = 1098.5(6) angstroms3, C2, Z = 2, mu = 0.71073 angstroms and R = 0.0296 for 1998 observed reflections. The fructose moiety of the complex exists as a beta-d-pyranose. The strontium atom is surrounded by eight oxygen atoms, which are arranged in symmetry-related pairs that are derived from four sugar and two water molecules. Three nonvicinal hydroxyl groups of fructose are involved in strontium binding. All the hydroxyl groups and water molecules are involved in forming an extensive hydrogen-bond network. The Sr-fructose complex is isostructural with the Ca-fructose complex, and the crystal structures and FTIR spectra of the two complexes are compared in this article. The O-H, C-O, and C-O-H vibrations are shifted, and the relative intensities changed in the complexes IR spectra, which indicate sugar metalation. By studying the metal-binding properties of fructose, it is hoped that such would aid in the understanding of the structural chemistry of metal ions interacting with saccharides, as an actual biological system, and thereby aid in the interpretation of some particular biological processes.     

Sugar interaction with metal ions. The coordination behavior of neutral galactitol to Ca(II) and lanthanide ions

The crystal structures of CaCl(2).galactitol.4 H(2)O and 2EuCl(3).galactitol.14 H(2)O were determined to compare the coordination behavior of Ca and lanthanide ions. The crystal system of the Ca-galactitol complex, CaCl(2).C(6)H(14)O(6).4 H(2)O, is monoclinic, Cc space group. Each Ca ion is coordinated to eight oxygen atoms, four from two galactitol molecules and four from water molecules. Galactitol provides O-2, -3 to coordinate to one Ca(2+), and O-4, -5 with another Ca(2+), to form a chain structure. The crystal system of the Eu-galactitol complex, 2EuCl(3).C(6)H(14)O(6).14 H(2)O, is triclinic, P1; space group. Each Eu ion is coordinated to nine oxygen atoms, three from an alditol molecule and six from water molecules. Each galactitol provides O-1, -2, -3 to coordinate with one Eu(3+) and O-4, -5, -6 with another Eu(3+). The other water molecules are hydrogen-bonded in the structure. The similar IR spectra of Pr-, Nd-, Sm-, Eu-, Dy-, and Er-galactitol complexes show that those lanthanide ions have the same coordination mode to neutral galactitol. The Raman spectra also confirm the formation of metal ion-carbohydrate complexes.     

Sugar interaction with metal ions. The crystal structure and Raman spectra study of SmCl3-galactitol complex

The crystal structure of 2SmCl3.galactitol.14H2O has been determined. The crystal system is triclinic, space group: P-1. The unit cell dimensions: a = 9.683(2) A, b = 10.341(2) A, c = 7.990(2) A; alpha = 108.01(3) degrees, beta = 92.71(3) degrees, gamma = 88.42(3) degrees. Each Sm atom is coordinated to nine oxygen atoms, three from the alditol and six from water molecules, with Sm-O distance from 2.417 to 2.520 A. The seventh water molecule is hydrogen-bonded by the hydroxy hydrogen on O-3 (O(3)-H(13)...O(10), 2.635 A). After forming complexes the peaks have shifted and the relative intensities have changed in the IR and Raman spectra, which are corresponding to the changes in bond distances and bond angles of the structures. The IR and Raman spectra of Pr-, Nd- and Sm-galactitol complexes are similar, which show that the three metal ions have the same coordination mode.