OH Bonds Of Water Research Articles

Water-Structure-Specific Entropic Dominance in the Filling of Boron Nitride Nanotubes

The filling of nanometer and sub-nanometer channels/tubes with water governs applications ranging from desalination and filtration to nanoscale energy conversion. Here, we report the most nonintuitive entropy-dominated filling of mildly hydrophilic boron nitride nanotubes (BNNTs) with diameters ranging from 0.85 to 1.69 nm. For all the BNNT sizes, water inside the BNNT is more stable than water in the bulk. The factor dictating the favorable nature of the entropy depends on the specific-BNNT-diameter-dictated structure of the water molecules. For example, for the 0.85 nm BNNT, the rotational entropic component dominates due to the presence of a significant fraction of the dangling water OH bonds that do not participate in hydrogen bonding. The fraction of such dangling OH bonds (the average HBs per molecule) decreases (increases) with an increase in the BNNT diameter, leading to a progressively reduced contribution of the rotational entropy. For the 1 nm BNNT, the translational entropic component dominates due to the enhanced in-plane motion of the water molecules caused by the single-file nature of water molecules spanning a significant radial expanse inside the BNNT. For larger BNNTs, translational entropy decreases with an increase in the BNNT diameter, although it remains the dominant factor governing the entropy-driven filling of BNNTs. This favorable translational entropy for larger BNNTs can be associated with (1) the presence of chain-like regions formed by water in 1.13 nm BNNT and (2) the presence of a high specific water volume and reduced number of HBs per molecule (as compared with bulk water) in 1.27, 1.41, 1.55, and 1.69 nm BNNTs.

Survival and efficacy of entomopathogenic nematodes on exposed surfaces

Entomopathogenic nematodes (EPN) species differ in their capability to withstand rapid desiccation (RD). Infective juveniles of Steinernema carpocapsae are a better adaptable and tolerant than Steinernema feltiae or Heterorhabditis bacteriophora as, an optimal RH of > 90% is required by S. feltiae and H. bacteriophora while maintaining RH equivalent to 74% could sustain survival of S. carpocapsae under RD. Our findings from infectivity suggest that following application, shrunk IJs are acquired passively by the larvae, probably rehydrate and resume infection within the insect gut. Water loss rate is a key factor affecting survival of S. carpocapsae on exposed surfaces. The present study provides the foundation for characterizing mechanism of rapid rate of water loss in EPN. ATR-FTIR is a rapid and reliable method for analysis of water loss. Changes in peak intensity was observed at 3100–3600 cm−1 (OH bonds of water), 2854 cm−1 (CH stretching of symmetric CH2, acyl chains), 2924 cm−1 (CH stretching of anti-symmetric CH2, lipid packing heterogeneity), 1634 cm−1 (amide I bonds) indicate major regions for hydration dependent changes in all EPN species. FTIR data also indicates that, S. carpocapsae contains strong water interacting regions in their biochemical profile, which could be an influencing factor in their water holding capacity under RD. ATR-FTIR were correlated to water content determined gravimetrically by using Partial Least square –Regression and FTIR multivariate method, which could be used to screen a formulation’s potential to maintain or delay the rate of water loss in a rapid and efficient manner.

Influence of steroids on hydrogen bonds in membranes assessed by near infrared spectroscopy

The covalent OH bonds of water vibrate and absorb radiation in the near infrared (NIR) region at wavelengths that vary according to the strength of the bonds which, at the same time, are sensitive to the number and/or strength of hydrogen bonds. By means of multivariate analytical tools, such spectral shift was exploited to study the effect of temperature, 25-hydroxycholesterol and progesterone on the H-bonded network of water in DMPA membranes. Temperature was found as the dominating factor altering the NIR spectra of water and then the H-bonds. Increasing temperatures disrupt the H-bonds network, strengthening the OH covalent bonds. The disruption of the H-bonds along the 13–58 °C range was noticeably greater than that caused by lipids or steroids at 500 μM. The H-bonded network of the interfacial water in DMPA membranes was disrupted by the presence of 25-hydroxycholesterol, but no significant disruption was observed in the presence of progesterone. The reduction of the H-bonds entails a reduction in the aggregation of the interfacial water by a reduction in the number of H-bonded molecules. It is proposed that the number of water molecules bonded with two H-bonds diminishes and the number of molecules with no H-bond increases roughly at similar proportions, with a constant population of molecules with one H-bond. The opposed effects of steroids are discussed in the context of their opposed effects on the phase state of membranes, the membrane water content and the steroid molecular structure.

Conformer selective monohydrated clusters of 1,2,3,4 –tetrahydroisoquinoline in S0: I-Potential energy surface studies, vibrational signatures and NBO analysis

The global minima in the potential energy surface of 1, 2, 3, 4-tetrahydroisoquinoline (THIQ):(H2O) prefer the twisted equatorial orientation of the NH group. It is characterized by a strong OH⋅⋅⋅N and a weak O-H⋅⋅⋅π hydrogen bonds. The computations at the ab initio level and DFT methods with M06–2X and ωB97X-D functionals generated consistent results. The monohydrate with the axial orientation of NH having a single OH⋅⋅⋅N bond in the twisted configuration of THIQ is higher by 240 ± 40 cm−1. The N⋅⋅⋅H bond length is smaller in the latter. All the clusters are located in the potential energy surface of THIQ :(H2O) drawn with the variation of the dihedral angles of the saturated ring of THIQ. Various kinds of hydrogen bonds are observed. Binding energy of each structure is computed incorporating BSSE corrections. Interestingly, the largest of them correspond to a conformer of THIQ, where it was a transition state in the bare molecule. The vibrational analysis of the clusters indicates the reassignment of a number of bands in the observed IR spectra. The red-shifts observed in the different stretching modes of water in the two lowest energy clusters are suitably explained. This is further verified from NBO computations. The changes in s-character, NBO energies and OH bond lengths with the variation of hydrogen bond distances clearly signify the dominant nature of hyperconjugation mechanism. The natures of each OH bonds of water are investigated thoroughly. The bond which is not taking part in hydrogen bonding shows some apparently unexpected behaviors. HOMO and LUMO plots and their energy differences are employed to qualitatively explain the experimental results observed earlier. Changes in Molecular Electrostatic Potentials (MEP) on cluster formation are explained and confirm our computations. Maximum hardness principle (MHP) is followed by the most stable monohydrate only. Hardness values display a certain arrangement depending on the type of hydrogen bonding sites. We suggest further experiments to confirm our key observations.

Atomic-level insights into nano-salt droplets wetting on the MgO surface using molecular dynamics simulations

The effects of NaCl solution concentrations on the water wettability of the MgO surface have been studied using molecular dynamics simulations. We find that ion hydration has a strong ability to dominate the structure of water network in the hydration layer. It can transform the orientation of water OH bonds, and reconstruct an ordered water network in the first layer, which in turn reduces the density of inter-layer hydrogen bonds. This further results in weak interactions between the first hydration layer and the actual droplet above the hydration layer, eventually increasing the hydrophobicity of the MgO(001) surface and corrosion resistance.

Ab initio investigation of the ground and excited states of RuO+,0,- and their reaction with water.

High-level quantum chemical calculations on RuO0,± elucidate the electronic structure of their low-lying electronic states. For thirty-two states, we report the electronic configurations, bond lengths, vibrational frequencies, spin-orbit splittings, and excitation energies. The electronic states of RuO can be generated from those of RuO+ by adding one electron to the σ non-bonding orbital closely resembling the 5s atomic orbital of Ru. The ground states for RuO and RuO- are clearly identified as 5Δ and 4Δ, but the two states (4Δ and 2Π) compete for RuO+. The difficulty of calculations is revealed by our small binding energies compared to the experimental values. In addition, we studied the reaction of the three species with water in their ground and selected low-lying electronic states. We found a consistent decrease of the activation energy barriers and higher exothermicity as we add electrons to the system. RuO- is found to facilitate the reaction for both kinetic and thermodynamic reasons.

Aqueous hydroxyl group as the vibrational probe to access the hydrophobicity of amide derivatives

First principles molecular dynamics (FPMD) simulations of relatively dilute aqueous solutions of N-methylformamide (NMF), N, N-dimethylacetamide (DMA), N-methylacetamide (NMA) were carried out to elucidate the effects of variation of hydrophobicity of amide molecules on structure, dynamics and spectral properties of solvating water molecules. A quantitative analysis of dangling OH groups of water molecules, one of the consequences of hydrophobicity, around the amide molecules was performed to explore the structure of surrounding water molecules. We observe that DMA has the most hydrophobic character among the three amide molecules; the lifetime of dangling OH mode of water molecules and the number of such modes are found to be more inside the solvation shell of DMA as compared to NMA and NMF molecules. Overall this lifetime is more inside the solvation shell of amides compared to the bulk water molecules for all aqueous solutions of amides. Rotational dynamics calculation suggests significant retardation of OH bonds of water near the amide oxygen atom (O) due to the OwHw⋯O strong hydrogen bonds. A moderate slowdown of reorientational dynamics is also observed for OH modes that are close to the hydrophobic surface of DMA in its aqueous solution. Vibrational density of states (VDOS) and frequency distribution calculations point out the higher average stretching frequency (~3600–3850 cm−1) of free OH groups. Hydrogen bond lifetime calculations conceive that DMA, having three methyl groups, makes stronger hydrogen bonds through the CO moiety. Vibrational spectral diffusion of bulk water and solvation shell water molecules were also calculated in combination with wavelet transform and frequency-frequency autocorrelation functions. The CO group affected OH stretching frequency bands for aqueous solutions of NMF and NMA molecules are more pronounced than that of DMA. However, NH affected OH frequency bands are less pronounced for NMA and DMA due to the presence of more number of hydrophobic methyl groups. Going from NMF to DMA, the OH frequency bands inside the amide solvation shells shift towards the higher value due to the enhancement of hydrophobicity. The vibrational spectral diffusion of OH modes around CO and NH (N for DMA) groups, as well as for bulk water molecules, is also investigated. Three time scales were found for these calculations for all the cases. The fast time scales in the range ~50–100 fs are due to the amide-water intact hydrogen bonding, and two slower time scales in the range ~0.6–3.90 ps and ~10–20 ps were found. The time scales in the range of ~0.6 to 3.90 ps can be attributed to carbonyl-water and N-H-water hydrogen bonding, and the very long time scales are due to the escape dynamics water molecules from the solvation shell of CO and NH (N for DMA) groups.

Closest-Packing Water Monolayer Stably Intercalated in Phyllosilicate Minerals under High Pressure.

The directional hydrogen-bond (HB) network and nondirectional van der Waals (vdW) interactions make up the specificity of water. Directional HBs could construct an ice-like monolayer in hydrophobic confinement even in the ambient regime. Here, we report a water monolayer dominated by vdW interactions confined in a phyllosilicate interlayer under high pressure. Surprisingly, it was in a thermodynamically stable state coupled with bulk water at the same pressure (P) and temperature (T), as revealed by the thermodynamic integration approach on the basis of molecular dynamics (MD) simulations. Both classical and ab initio MD simulations showed water O atoms were stably trapped and exhibited an ordered hexagonal closest-packing arrangement, but OH bonds of water reoriented frequently and exhibited a specific two-stage reorientation relaxation. Strikingly, hydration in the interlayer under high pressure had no relevance with surface hydrophilicity rationalized by the HB forming ability, which, however, determines wetting in the ambient regime. Intercalated water molecules were trapped by vdW interactions, which shaped the closest-packing arrangement and made hydration energetically available. The high pressure-volume term largely drives hydration, as it compensates the entropy penalty which is restricted by a relatively lower temperature. This vdW water monolayer should be ubiquitous in the high pressure but low-temperature regime.

Role of a Water Network around the Mn4CaO5 Cluster in Photosynthetic Water Oxidation: A Fourier Transform Infrared Spectroscopy and Quantum Mechanics/Molecular Mechanics Calculation Study.

Photosynthetic water oxidation takes place at the Mn4CaO5 cluster in photosystem II. Around the Mn4CaO5 cluster, a hydrogen bond network is formed by several water molecules, including four water ligands. To clarify the role of this water network in the mechanism of water oxidation, we investigated the effects of the removal of Ca(2+) and substitution with metal ions on the vibrations of water molecules coupled to the Mn4CaO5 cluster by means of Fourier transform infrared (FTIR) difference spectroscopy and quantum mechanics/molecular mechanics (QM/MM) calculations. The OH stretching vibrations of nine water molecules forming a network between D1-D61 and YZ were calculated using the QM/MM method. On the the calculated normal modes, a broad positive feature at 3200-2500 cm(-1) in an S2-minus-S1 FTIR spectrum was attributed to the vibrations of strongly hydrogen-bonded OH bonds of water involving the vibrations of water ligands to a Mn ion and the in-phase coupled vibration of a water network connected to YZ, while bands in the 3700-3500 cm(-1) region were assigned to the coupled vibrations of weakly hydrogen-bonded OH bonds of water. All the water bands were lost upon Ca(2+) depletion and Ba(2+) substitution, which inhibit the S2 → S3 transition, indicating that a solid water network was broken by these treatments. By contrast, Sr(2+) substitution slightly altered the water bands around 3600 cm(-1), reflecting minor modification in water interactions, consistent with the retention of water oxidation activity with a decreased efficiency. These results suggest that the water network around the Mn4CaO5 cluster plays an essential role in the water oxidation mechanism particularly in a concerted process of proton transfer and water insertion during the S2 → S3 transition.

Reversible water activation driven by contraction and expansion of a 12-vertex-closo-12-vertex-nido biscarborane cluster.

The activation of O-H bonds of water at room temperature driven by the cage-opening rearrangement of a biscarborane-based cluster is reported. The reaction of the 12-vertex-closo-12-vertex-nido biscarborane cluster with water led to the quantitative and selective two-vertex decapitation of a carborane cluster and formation of the pendent boronic acid hydride B(H)(OH) group. Remarkably, this transformation can be quantitatively reversed with the release of water and re-formation of the starting biscarborane cage. The flexibility of cage decapitation/expansion and its influence on the reactivity of an exohedral substituent represent a new approach to cluster-induced organic transformations.

The highly reactive benzhydryl cation isolated and stabilized in water ice.

Diphenylcarbene (DPC) shows a triplet ground-state lying approximately 3 kcal/mol below the lowest singlet state. Under the conditions of matrix isolation at 25 K, DPC reacts with single water molecules embedded in solid argon and switches its ground state from triplet to singlet by forming a strong hydrogen bond. The complex between DPC and water is only metastable, and even at 3 K the carbene center slowly inserts into the OH bond of water to form benzhydryl alcohol via quantum chemical tunneling. Surprisingly, if DPC is generated in amorphous water ice at 3 K, it is protonated instantaneously to give the benzhydryl cation. Under these conditions, the benzhydryl cation is stable, and warming to temperatures above 50 K is required to produce benzhydryl alcohol. Thus, for the first time, a highly electrophilic and extremely reactive secondary carbenium ion can be isolated in a neutral, nucleophilic environment avoiding superacidic conditions.

A Highly Oxidizing and Isolable Oxoruthenium(V) Complex [RuV(N4O)(O)]2+: Electronic Structure, Redox Properties, and Oxidation Reactions Investigated by DFT Calculations

The electronic structure and redox properties of the highly oxidizing, isolable Ru(V)=O complex [Ru(V)(N4O)(O)](2+), its oxidation reactions with saturated alkanes (cyclohexane and methane) and inorganic substrates (hydrochloric acid and water), and its intermolecular coupling reaction have been examined by DFT calculations. The oxidation reactions with cyclohexane and methane proceed through hydrogen atom transfer in a transition state with a calculated free energy barrier of 10.8 and 23.8 kcal mol(-1), respectively. The overall free energy activation barrier (ΔG(≠)=25.5 kcal mol(-1)) of oxidation of hydrochloric acid can be decomposed into two parts: the formation of [Ru(III)(N4O)(HOCl)](2+) (ΔG=15.0 kcal mol(-1)) and the substitution of HOCl by a water molecule (ΔG(≠)=10.5 kcal mol(-1)). For water oxidation, nucleophilic attack on Ru(V)=O by water, leading to O-O bond formation, has a free energy barrier of 24.0 kcal mol(-1), the major component of which comes from the cleavage of the H-OH bond of water. Intermolecular self-coupling of two molecules of [Ru(V)(N4O)(O)](2+) leads to the [(N4O)Ru(IV)-O2-Ru(III)(N4O)](4+) complex with a calculated free energy barrier of 12.0 kcal mol(-1).

Effect of the nature of ions on the position of the absorption bands of water OH bonds in diffuse reflection spectra in the near-infrared region

The effect of the nature of anions and cations on the position of the absorption bands of free and crystallization water in inorganic salts in the near-infrared region (7400–4000 cm−1) was systematically studied. It was shown experimentally that the shift of the absorption bands of free water to the high-frequency region is 100 cm−1 in the region of 6900 and 62.1 cm−1 in the region of 5160 cm−1. It was concluded that the results on the shift of the water absorption bands in moisture-containing solid-state compounds with respect to those of pure liquid water can serve for a qualitative estimate of the bond energy of water with the substance under study and can be used to choose the wavelength for measuring the humidity of these objects and those more complicated in composition by means of near-infrared spectroscopy.

Non-monotonic dependence of water reorientation dynamics on surface hydrophilicity: competing effects of the hydration structure and hydrogen-bond strength

The reorientation dynamics of interfacial water molecules was recently shown to change non-monotonically next to surfaces of increasing hydrophilicity, with slower dynamics next to strongly hydrophobic (apolar) and very hydrophilic surfaces, and faster dynamics next to surfaces of intermediate hydrophilicities. Through a combination of molecular dynamics simulations and analytic modeling, we provide a molecular interpretation of this behavior. We show that this non-monotonic dependence arises from two competing effects induced by the increasing surface hydrophilicity: first a change in the hydration structure with an enhanced population of water OH bonds pointing toward the surface and second a strengthening of the water-surface interaction energy. The extended jump model, including the effects due to transition-state excluded volume and transition-state hydrogen-bond strength, provides a quasi-quantitative description of the non-monotonic changes in the water reorientation dynamics with surface hydrophilicity.

Water reorientation, hydrogen-bond dynamics and 2D-IR spectroscopy next to an extended hydrophobic surface

The dynamics of water next to hydrophobic groups is critical for several fundamental biochemical processes such as protein folding and amyloid fiber aggregation. Some biomolecular systems, like melittin or other membrane-associated proteins, exhibit extended hydrophobic surfaces. Due to the strain these surfaces impose on the hydrogen (H)-bond network, the water molecules shift from the clathrate-like arrangement observed around small solutes to an anticlathrate-like geometry with some dangling OH bonds pointing toward the surface. Here we examine the water reorientation dynamics next to a model hydrophobic surface through molecular dynamics simulations and analytic modeling. We show that the water OH bonds lying next to the hydrophobic surface fall into two subensembles with distinct dynamical reorientation properties. The first is the OH bonds tangent to the surface; these exhibit a behavior similar to the water OHs around small hydrophobic solutes, i.e. with a moderate reorientational slowdown explained by an excluded volume effect due to the surface. The second is the dangling OHs pointing toward the surface: these are not engaged in any H-bond, reorient much faster than in the bulk, and exhibit an unusual anisotropy decay which becomes negative for delays of a few picoseconds. The H-bond dynamics, i.e. the exchanges between the different configurations, and the resulting anisotropy decays are analyzed within the analytic extended jump model. We also show that a recent spectroscopy technique, two-dimensional time resolved vibrational spectroscopy (2D-IR), can be used to selectively follow the dynamics of dangling OHs, since these are spectrally distinct from H-bonded ones. By computing the first 2D-IR spectra of water next to a hydrophobic surface, we establish a connection between the spectral dynamics and the dynamical properties that we obtain directly from the simulations.

Theoretical Study of Photochemical Mechanisms of C3O Formation

Photolysis of the C3·H2O complex in an argon matrix with λ ≥ 400 nm leads to the formation of propynal and tricarbon oxide. One pathway to the formation of propynal has been shown experimentally and theoretically to involve the intermediate hydroxypropadienylidene (HPD). This intracomplex mechanism involves the photoinitiated insertion of C3 into an OH bond of water followed by migration of H atoms along the CCCO backbone to form the end product, propynal. The mechanism by which tricarbon oxide, C3O, is formed is examined in this investigation. To probe this pathway, the H2C3O potential surface, including H atom loss and later attachment, has been calculated at the MP2/6-31G* level of theory. It is shown that two photoconversion pathways exist. One leads to HPD (and thence to propynal), while the other involves H atom loss to a HC3O intermediate, which then either loses another hydrogen atom to form C3O or captures a hydrogen atom to produce propynal. In addition, bimolecular mechanisms involving C atoms,...

Theoretical characterization of the reaction CH3+OH→CH3OH→products: The 1CH2+H2O, H2+HCOH, and H2+H2CO channels

The potential energy surface (PES) for the CH3OH system has been characterized for the 1CH2+H2O, H2+HCOH, and H2+H2CO product channels using complete-active-space self-consistent-field (CASSCF) gradient calculations to determine the stationary point geometries and frequencies followed by CASSCF/internally contracted configuration-interaction (CCI) calculations to refine the energetics. The 1CH2+H2O channel is found to have no barrier. The long range interaction is dominated by the dipole–dipole term, which orients the respective dipole moments parallel to each other but pointing in opposite directions. At shorter separations there is a dative bond structure in which a water lone pair donates into the empty a″ orbital of CH2. Subsequent insertion of CH2 into an OH bond of water involves a non-least-motion pathway. The H2+HCOH, and H2+H2CO pathways have barriers located at −5.2 and 1.7 kcal/mol, respectively, with respect to CH3+OH. From comparison of the computed energetics of the reactants and products to known thermochemical data it is estimated that the computed PES is accurate to ±2 kcal/mol.

Molecular dynamics of phenol at the liquid-vapor interface of water.

Molecular dynamics results are presented for phenol at the water liquid-vapor interface at 300 K. The calculated excess free energy of phenol at the interface is -2.8 +/- 0.4 kcal/mol, in good agreement with the recent experimental results of Eisenthal and co-workers. The most probable orientation of the phenol molecule at the surface is such that the aromatic ring is perpendicular to the interface and the OH group is fully immersed in water. The hydroxyl substituent has a preferred orientation which is similar to the orientation of OH bonds of water at the pure water liquid-vapor interface. The transition between interfacial and bulk-like behavior of phenol is abrupt and occurs when the center of mass of the solute is located about 6 angstroms from the Gibbs surface of water. In this region the para carbon atom of the hydrophobic benzene ring can reach the interface and become partially dehydrated. This result suggests that the width of the interfacial region in which the behavior of a simple amphiphilic solute in water is influenced by the presence of the surface depends primarily on the size of its hydrophobic part. The role of the OH substituent was investigated by comparing phenol at the interface with two model systems: benzene with and without partial charges on carbon and hydrogen atoms. It is shown that in the absence of the hydrophilic substituent the solute is located further away from the liquid phase and is more likely to be oriented parallel to the interface. However, when the center of mass of the solute is moved into the interfacial region where the density of water approaches that of the bulk solvent, all three molecules become oriented perpendicularly to the surface. In this orientation the work of cavity formation needed to accommodate the hydrophobic ring in aqueous solvent is minimized.

Rotational and vibrational energy distributions of 16OH(X 2Π) and 18OH(X 2Π) produced in the reaction of O(1D) with H2O and H2 18O

Laser induced fluorescence measurements of the rotational population distributions for the 16OH(X 2Πi, v = 0, 1) products of the reaction of O(1D) with H2O and the 16OH(X 2Πi, v = 0, 1) and 18OH(X 2Πi, v = 0, 1) products of the reaction of O(1D) with H2 18O are presented here. The rotational and vibrational distributions of the 16OH formed in the normal isotopic abundance reactions were found to be close to those expected if the energy of the reaction is statistically distributed amongst all available product states. Isotopic labeling of the oxygen atom in the reactant water molecule demonstrated that the vibrational distribution of the new 16OH bond formed is significantly more energetic than the remaining 18OH bond, while the rotational distributions were similar. These results are interpreted as H atom abstraction (or stripping) dynamics predominating over O atom insertion into the water OH bonds.

Investigation of the reaction between oligo-oxyethylene urethane methacrylates and ozone in order to determine double bonds

fact tha t with an increase m the degree of drying, the absorbed is characterized by a stronger H bond with cellulose molecules. As K ~ is the ratio of absorption coefficients for bond-stretching and deformation vibrations of the OH bond of water, on increasing chsturbance due to the H bond, the increase m the absorption coefficient for bond-stretching mbrations is less than for deformation vlbrahons. According to modern views of the structure of cellulose, the disordered region is characterlzed by varying abili ty to absorb moisture, Le. one can talk about a set or spectrum of disordered regions of cellulose Cellulose materials of different origin are characterized both by a different water surface [5] and different heats of wetting. The constancy of K~i t values according to moisture content m further evidence of the heterogeneity of cellulose m dmordered regions. CONCLUSIONS