High Degree Of Hydration Research Articles

Crystal structure of ilyukhinite, a new mineral of the eudialyte group

The crystal structure of ilyukhinite, a new mineral of the eudialyte group, is studied by X-ray diffraction. The mineral found in pegmatite bodies of the Kukisvumchorr Mountain (Khibiny alkaline complex) is characterized by low sodium content, high degree of hydration, and predominance of manganese over iron. The trigonal cell has the following parameters: a = 14.1695(6) and c = 31.026(1) A; space group R3m. The structure is refined to final R = 0.046 in the anisotropic approximation of atomic displacements using 1527F > 3σF. The idealized formula of ilyukhinite (Z = 3) is written as (H3O,Na)14Ca6Mn2Zr3Si26O72(OH)2 · 3H2O. The new mineral differs from other representatives of the eudialyte group by the predominance of both oxonium in the N positions of extra-framework cations and manganese in the М2 position centering the tetragonal pyramid.

Thermogravimetric research into fish and plant semifinished products made of raw and blanched tissues of Azov goby and wheat bran

According to results of thermogravimetric and differentia-thermal studies, we compared characteristics of the amount of adsorption– and capillary-bound moisture in the experimental samples of fish and plant semifinished products, as well as determined the values of activation energy of the molecules of water at different temperatures of moisture removal. By the results of analysis of the DTG peaks, it is established that the largest amount of osmotic– and adsorption-bound moisture is observed in samples made on the base of raw fish raw materials due to the higher degree of hydration of protein molecules in minces. It is found that the application of hydrothermal pre-treatment of muscle, connective and skeletal tissue complex of Azov goby leads to the reduction in the amount of adsorption-bound moisture and decreses the energy of its bond with the product. The use of wheat bran somewhat increases the amount of bound moisture in the fish mince structure as a result of increase in the number of available hydroxyl groups and the formation of macroporous structure, which causes the increase in its hydrofilicity. It is established experimentally that the influence of plant raw materials on the increase in activation energy of the molecules of water for the experimental fish and plant semifinished products is less significant than the use of native fish raw material. The obtained results allow better understanding of the structural changes that occur in the process of drying the fish and plant semifinished products. They might be applied to optimize the drying processs of fish and plant semifinished products and to predict their technological behavior in various food systems, as well as while storing.

Steam reforming of toluene, methane and mixtures over Ni/ZrO2 catalysts

This work studied the performance of Ni catalysts supported on three different zirconia structures for SR of toluene, methane and methane/toluene mixtures. The presence of both reactants in the feed decreased the conversion of toluene and methane. This was due to the increase in the concentration of CHx species on the surface of the metallic particle. All Ni/ZrO2 catalysts deactivated during SR of toluene, methane or the mixture. Scanning electron microscopy and thermogravimetric analysis revealed the formation of carbon deposits over the surface of catalysts. However, the amount of carbon deposited depended on the reaction conditions and the structure of zirconia. Monoclinic zirconia exhibits a lower densitiy of acid sites and a higher degree of hydration, which contributes to the lower carbon formation. The amount of carbon deposited over all catalysts significantly increased during SR of the mixture. This is due to a decrease in the rate of the gasification reaction and an increase in the rate of the CHx species formation reaction, which enhances the catalysts deactivation rate.

Effect of Aluminum Insertion Material on the Properties of AAC

Study on the compressive strength, shrinkage and effect of aluminum insertion materials on the hydration products of Autoclaved Aerated Concrete (AAC). The types and properties of hydration products are studied by X-Ray Diffraction Analysis (XRD), Differential Thermal Analysis (DTA), Scanning Electron Microscope analysis (SEM) and so on. The results showed that the strength and the shrinkage resistance capability of the product could be improved effectively. Al3+successfully doped into C-S-H gel and tobermorite crystals, then replaced si4+of tobermorite and formed the system of C-A-S-H. Tobermorite in aluminum insertion aerated concrete is smaller and more compact. All hydration products interlace to form a whole, then the structure turns denser. Low porosity, high crystal gel volume ratio and high hydration degree are the key of the high strength aluminum insertion aerated concrete. Aluminum insertion materials improve the performance of the products.

Effects of operating parameters on the pressurized Bunsen reaction for the integrated operation of sulfur–iodine hydrogen production process

The sulfur–iodine hydrogen production process (SI process) is an efficient thermochemical process. Developing composition data of the Bunsen products that are obtained under pressurized conditions is important for the integrated operation of SI process. We investigated the characteristics of the pressurized Bunsen reaction by varying operating parameters (pressure, temperature, I2 and H2O feed concentrations). An HIx solution that consisted of HI, I2 and H2O was used as the reactant. When the pressure increased, the extent of Bunsen reaction was enhanced by increasing the solubility of SO2 gas in the HIx solution. In addition, the amount of H2SO4 phase solution increased due to the decrease in the amount of HIx complex, which has a high degree of hydration. Increasing temperature enhanced the separation performance of the Bunsen products, while the extent of Bunsen reaction decreased. When I2 feed concentration increased, the occurrence of side reaction was inhibited, but the separation performance of the Bunsen products decreased. Although increasing H2O feed concentration was favorable for the pressurized Bunsen reaction, the H2O feed concentration should be controlled by considering the solubility of I2 in the HIx solution.

Self-aggregation of the pyrene labeled poly(acrylic acid) in nanoscopically crowded environments

Abstract The paper investigates the behavior of pyrene labeled poly(acrylic acid) with various graft content in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles (RMs) at various hydration degrees (w 0 ). The work is carried out by UV–vis, steady-state and time-resolved fluorescence as well as dynamic light scattering (DLS). The report indicates new insights regarding the interactions and dynamics of the fluorescent labeled polymer in the nanoscopic aqueous host. It was found that the spectral properties of the polymer depend on the H-bonds and π-π interactions. The efficiency of pyrene excimer formation indicated the “on-off” control of the polymer chain in RMs by triggering of w 0 . The constriction of the polymer coil in different nanocages of RMs influenced the formation of excimers. At low w 0 , the pyrene labeled poly(acrylic acid) senses the micellar interface. At higher hydration degree, the grafted polymer resides in the water pool of RMs with elevated polarity similar to that in the bulk water. The study discloses the ability of the pyrene-labeled polymer to sense the crowded nano-environments.

Effects of graphene oxide on the properties and microstructures of the magnesium potassium phosphate cement paste

This paper presents the effect of graphene oxide (GO) on the properties and microstructures of the magnesium potassium phosphate cement (MKPC) paste with a lower water to solid ratio (w/s) of 0.15. The influence of GO on the workability, hydration degree, mechanical behavior and microstructures of the MKPC paste is systematically investigated. The experimental results showed that the addition of GO shorted the final setting time and decreased the workability of the MKPC paste, but the compressive and flexural strength of the MKPC paste were improved by a moderate addition of GO. It was clearly indicated that compared with the fresh MKPC paste, the addition of 0.05wt.% GO can improve the compressive and flexural strength of the MKPC paste by 6.8% and 8.3%, respectively. The improved mechanical strength is not only attributed to the excellent mechanical properties of GO itself, but also the higher hydration degree and lower porosity of the MKPC paste by the GO addition. The microstructures of the MKPC paste with GO addition of 0.05wt.% become much denser and better crystallization of the hydration products can be achieved, compared with the fresh MKPC paste. However, more GO addition 0.10wt.% has a negative effect on the crystallization of the hydration products and mechanical behavior of the MKPC paste. Finally, the FTIR spectra indicated that there was no chemical bonding between the hydration products of the MKPC paste and GO. It is concluded that GO, as a promising nanofiller, has a great potential for reinforcing the MKPC paste.

Setting constraints on the nature and origin of the two major hydrous sulfates on Mars: Monohydrated and polyhydrated sulfates

AbstractMonohydrated Mg sulfate (MgSO4·H2O) and polyhydrated sulfate are the most common and abundant hydrous sulfates observed thus far on Mars. They are widely distributed and coexist in many locations. On the basis of results from two new sets of experiments, in combination with past experimental studies and the subsurface salt mineralogy observed at a saline playa (Dalangtan, DLT) in a terrestrial analogue hyperarid region on the Tibet Plateau, we can now set new constraints on the nature and origin of these two major Martian sulfates. Starkeyite (MgSO4·4H2O) is the best candidate for polyhydrated sulfate. MgSO4·H2O in the form of “LH‐1w,” generated from dehydration of Mg sulfates with high degrees of hydration, is the most likely mineral form for the majority of Martian monohydrated Mg sulfate. Two critical properties of Mg sulfates are responsible for the coexistence of these two phases that have very different degrees of hydration: (1) the metastability of a substructural unit in starkeyite at relatively low temperatures, and (2) catalytic effects attributed to coprecipitated species (sulfates, chlorides, oxides, and hydroxides) from chemically complex brines that help overcome the metastability of starkeyite. The combination of these two properties controls the coexistence of the LH‐1w layer and starkeyite layers at many locations on Mars, which sometimes occur in an interbedded stratigraphy. The structural H2O held by these two broadly distributed sulfates represents a large H2O reservoir at the surface and in the shallow subsurface on current Mars.

Effects of cations on the “salt in” of myofibrillar proteins

The solubilities of myofibrillar proteins (MPs) increased monotonically with increasing NaCl concentration at pH = pI (isoelectric point), but decreased monotonically with increasing NaCl concentration at pH < pI. At pH > pI, the solubilities decreased initially, but increased with increasing NaCl concentrations from 0.2 to 0.8 M. For chloride salts, the “salt in” effect of cations decreased in the order: Li+ > Na+ > K+ > Rb+. For sodium salts, the “salt in” effect of anions decreased in the sequence: Cl¯ > Br¯ > I¯ > SCN¯. The “salt in” effect of cations were stronger than that of anions. No evidence of increased electrostatic interaction was found during “salt in”. Presence of CH3COO¯ decreased the solubilization effect of Na+. These results indicate the “salt in” of MPs is more affected by the cations with higher degree of hydration, which may be interfered by the presence of highly hydrated anions.

Microstructural and mechanical properties study of the curing process of self-compacting concrete

A microstructural and mechanical properties study was conducted to investigate the effect of the curing conditions on the final properties of self-compacting concrete. Two different curing conditions were considered simulating the summer conditions in coastal (20°C and 70% relative humidity, RH) and central (cycles of 40°C) zones in Spain. Different microstructural and mechanical parameters were measured to study the hydration using different techniques: Micro-Raman spectroscopy, nuclear magnetic resonance, compressive strength and ultrasonic testing. After 7days of hydration the central conditions produce samples with higher hydration degree than coastal conditions, but after 28days of curing, the hydration degree was very similar in both curing conditions. This high hydration degree after 7days conducted to a decline or stabilization in compressive strength at long curing times. The mean chain length of the C-S-H gel formed in the studied concrete was quite high comparing with other works since more Al was incorporated in the C-S-H gel. It was also obtained that for high temperatures after 7days of curing all microstructural and mechanical parameters were quite stable meaning that high temperatures accelerate the hydration of the samples.

Encumbrance in desilylation triggered fluorogenic detection of the fluoride ion - a kinetic approach.

Highly selective fluorogenic detection of the fluoride ion becomes viable due to its propensity towards cleaving Si-O and Si-C bonds, the key reactive elements in fluoride selective chemodosimeters. Herein, acridinedione derived, two novel fluorescent probes bearing tertiarybutyldiphenylsilyloxy (TBDPS) and tertiarybutyldimethylsilyloxy (TBDMS) groups were synthesized and their fluoride selective dosimetric action in organic solvents and in mixed aqueous medium was established through steady state and time resolved fluorescence techniques. Unusually, these molecular probes maintain their sensitivity down to 10 ppb in both organic and mixed aqueous medium; hence they can be considered as highly selective and sensitive fluorescent probes for the fluoride anion. By following the kinetics of the desilylation process it is established that the reaction follows second order kinetics with respect to fluoride ion concentration in acetonitrile whereas it becomes first order in mixed aqueous medium owing to its high degree of hydration. Also, the hydrophobic and sterically crowded substitution on the silyl receptor hampers the reaction kinetics only in organic solvents whereas its influence in mixed aqueous medium is relatively very less. However, common inorganic cations (Na+) effectively hinder the reaction kinetics through strong ion pair interaction and prolong the response time. Therefore, the indigenous influences of three different factors which encumber the desilylation process were quantitatively enumerated and the prospective application of these fluorescent probes in detecting and validating fluoride ions in various environmental samples is demonstrated.

SODIUM CITRATE INFLUENCE ON FORMATION OF CEMENT STONE IN THE ALUMINOUS BINDER

The paper deals with the effect of sodium citrate on the formation of a cement stone in the aluminous binder. Formation of cement stone framework in cement hydraulic binder is accompanied with complicated physical and chemical processes of interphase interactions and dispersion, these processes are predicated on qualitative and quantitative composition of the cement mortar, continuous changes in its properties from preparation stage till curing. Addition of sodium citrate to tempering water enhances hydration of both Portland cement and calcium aluminate cement. Process pertaining to an increase of cement hydration rate is considered as a consequence of destruction in surface formations and exclusion of damping effect in respect of hydration rate and hydrolysis of products resulted from interaction of clinker material with tempering. It has been established that sodium citrate makes it possible to control processes of hydration, hydrolysis, binding and curing for cement mass. High degree of hydration of aluminous cement in the presence of sodium citrate provides fast binding and curing of binder, low porosity and rather high compression breaking strength of cement stone for all curing stages. An increase in concentration of sodium citrate in cement mixture up to 10 % of the cement mass exerts an influence not only on the process of cement mortar liquefaction, reduction of time for cement mass setting and hardening but also increases compression strength of cement stone. An analysis of the structure for cleavage surface of cement stone gives ground to declare that the addition of sodium citrate provides cement stone sealing and reduces its water absorption.

Synthesis and study of hybrid materials based on a nafion membrane and hydrated titania

The properties of hybrid membranes based on a perfluorosulfonated Nafion polymer and hydrated titania are described. The membranes have been prepared by casting from a solution containing particles of a dopant preformed by precipitation at different pH values or a precursor for further synthesis of titania. The dependence of the conductivity of these samples on relative humidity and temperature has been studied. Modification leads to an increase in the proton conductivity of the membranes; higher values are obtained for the samples prepared using preformed TiO2 particles. It has been shown that the background of the dopant has an effect on the conductivity value: at low relative humidity, higher values are obtained using titania with a higher degree of hydration. The introduction of small amounts of the dopant (1.5–3 wt %) leads to an increase in the cation transport selectivity compared to that of the unmodified membrane.

Evaluation of the hemocompatibility and rapid hemostasis of (RADA)4 peptide-based hydrogels

(RADA)4 peptides are promising biomaterials due to their high degree of hydration (<99.5% (w/v)), programmability at the molecular level, and their subsequent potential to respond to external stimuli. Interestingly, these peptides have also demonstrated the ability to cause rapid (∼15s) hemostasis when applied directly to wounds. General hemocompatibility of (RADA)4 nanofibers was investigated systematically using clot formation kinetics, C3a generation, and platelet activation (morphology and CD62P) studies. (RADA)4 nanofibers caused a rapid clot formation, but yielded a low platelet activation and low C3a activation. The study suggests that the rapid hemostasis observed when these materials are employed results principally from humoral coagulation, despite these materials having a net neutral charge and high hydration at physiological conditions. The observed rapid hemostasis may be induced due to the available nanofiber surface area within the hydrogel construct. In conclusion, our experiments strongly support further development of (RADA)4 peptide based biomaterials. Statement of SignificanceBiomedicine based applications of (RADA)4 peptides are being extensively studied for the purpose of improving drug carriers, and 3D peptide nanofiber scaffolds. However, this peptide’s biocompatibility has not been investigated till now. One particular study has reported a revolutionary and very desirable ability of (RADA)4 peptide to achieve complete and rapid hemostasis, nevertheless, the literature remains inconclusive on the underlying molecular mechanism. In this manuscript we bridge these two main knowledge gaps by providing the much needed systematic biocompatibility analysis (morphology analysis, platelet and C3a activation) of the (RADA)4 based hydrogels, and also investigate the underlying hemostatic mechanism of this peptide-induced hemostasis. Our work not only provides the much-needed biocompatibility of the peptide for applicative research, but also explores the molecular mechanism of hemostasis, which will help us design novel biomaterials to achieve hemostasis.

Crystal structure and genesis of the hydrated analog of rastsvetaevite

The crystal structure of the hydrated analog of the mineral rastsvetaevite (tentatively called “hydrorastsvetaevite”), which was found by A.P. Khomyakov in ultraagpaitic pegmatites at the Rasvumchorr Mountain of the Khibiny alkaline massif (Kola Peninsula), has been determined by single crystal X-ray diffraction. The trigonal unit-cell parameters are as follows: a = 14.2812(2) A, c = 60.533(5) A, V = 10691.54(3) A3, sp. gr. R3m. The structure was refined to R = 5.9% in the isotropic and anisotropic approximation of atomic displacement parameters based on 2068 ref lections with |F| > 3σ(F). “Hydrorastsvetaevite” is on the whole analogous to other 24-layer representatives of the eudialyte group (called “megaeudialytes”), but is characterized by a high potassium content and is distinguished from other potassium-rich minerals (rastsvetaevite, davinciite, and andrianovite) by low sodium and alkaline-earth metal content, as well as by a high degree of hydration accompanied by the insertion of H3O groups, which partially or completely replace large cations. The idealized formula of “hydrorastsvetaevite” (Z = 3) is (Na11(H3O)11K6(H2O)1.5Sr)Ca12Fe3Na2MnZr6Si52O144(OH)4.5Cl3.5(H2O)0.5. In alkaline pegmatites, “hydrorastsvetaevite” occurs as a secondary mineral developed from the original rastsvetaevite through decationation and hydration. The characteristic features of the genesis of eudialyte-group minerals containing potassium as a species-forming cation are discussed in terms of the concept of transformational mineral species. an]Mis||Original Russian Text © R.K. Rastsvetaeva, S.M. Aksenov, K.A. Rozenberg, 2015, published in Kristallografiya, 2015, Vol. 60, No. 6, pp. 897–905.

An insight into hydration structure of sodium glycinate from ab initio quantum chemical study.

The hydration structure of sodium glycinate (Na(+)GL(-)) is probed by the Monte-Carlo multiple minimum (MCMM) method combined with quantum mechanical (QM) calculations at the MP2/6-311++G(d,p) level. In the gas phase, the energy of [Na(+)GL(-)]β is more than 30 kJ mol(-1) higher than [Na(+)GL(-)]α. With higher degrees of hydration, our results indicate that the most stable conformers of [Na(+)GL(-)]∙(H2O)8 were derived from [Na(+)GL(-)]β instead of [Na(+)GL(-)]α. The stable conformers determined by the conductor-like polarizable continuum model (CPCM) also show that [Na(+)GL(-)]β is more stable than [Na(+)GL(-)]α in the liquid phase. By analyzing the hydration process, water…water hydrogen bonding interaction will be more preferable than ion…water interaction as the number of water molecules increases. According to the electronic density at the bond critical point on the Na-X bonds (X = O1, O2, N) in the low-energy conformers, Na(+)GL(-) will be dissociated as Na(+) and GL(-) in the bulk water, which is not predicted by the CPCM model. The structure features and the charge redistribution of Na(+)GL(-) will provide a physical explanation for the weakening Na-O1 interaction.

Isoeugenol has a non-disruptive detergent-like mechanism of action.

Isoeugenol is an essential oil constituent of nutmeg, clove, and cinnamon. Despite isoeugenol's promising antimicrobial activity, no studies have yet investigated its mode of antibacterial action at the molecular level. The aim of this study is to clarify isoeugenol's antibacterial mode of action using the Gram-negative and Gram-positive model organisms Escherichia coli and Listeria innocua, respectively. We determined the antimicrobial activity of isoeugenol against the model organisms, and examined how isoeugenol affects cell morphology, cell membrane permeabilization, and how isoeugenol interacts with phospholipid membranes using vesicle and supported lipid bilayer models. Isoeugenol demonstrated a bactericidal activity against E. coli and L. innocua that did not affect cell morphology, although the cell membrane was permeabilized. We hypothesized that the cell membrane was the primary site of action, and studied this interaction in further detail using purified membrane model systems. Isoeugenol's permeabilization of calcein-encapsulated vesicles was concentration dependent, and isoeugenol's interaction with giant unilamellar vesicles indicated increased membrane fluidity and a non-disruptive permeabilization mechanism. This contradicted membrane fluidity measurements on supported lipid bilayers (SLBs), which indicated decreased membrane fluidity. However, further investigations demonstrated that the interaction between isoeugenol and bilayers was reversible, and caused membranes to display heterogeneous topography, an increased mass, and a higher degree of hydration. In conclusion, we propose that isoeugenol interacts with membranes in a reversible non-disruptive detergent-like manner, which causes membrane destabilization. Furthermore, we argue that isoeugenol increases membrane fluidity. Our work contributes to the understanding of how essential oil constituents interact with cell components.

Investigating the interactions of resveratrol with phospholipid vesicle bilayer and the skin: NMR studies and confocal imaging

In this work, phospholipid vesicle-based nanoformulations were developed to deliver antioxidant resveratrol (RSV) to the skin. Penetration enhancer-containing vesicles (PEVs) were prepared adding Oramix™ CG110 or Lauroglycol™ FCC to phosphatidylcholine to favor RSV diffusion through the skin, which was investigated using Franz cells.Vesicles were approximately 100nm in size, negatively charged and fairly round in shape, as shown via transmission electron microscopy. Nuclear magnetic resonance studies were performed to investigate the RSV/vesicle interactions at the molecular scale, which revealed that RSV was deeply embedded in the bilayer, as shown by the restricted mobility of the drug. Moreover, PEVs improved drug local accumulation 1.7- to 2.1-fold, as compared to the control liposomes. Confocal imaging displayed broadened intercellular spaces in the viable epidermis of PEVs treated skin and high degree of hydration, which are presumably due to the occlusive film formed on the skin surface by the vesicles. These phenomena may be responsible for the higher RSV accumulation achieved when administering PEVs, as compared to control liposomes. Finally, the toxicity of the vesicular formulations was evaluated in vitro against 3T3 fibroblasts, showing no alteration on cell viability after 24h incubation with RSV loaded vesicles.The results from this study suggest that the proposed formulations may be a potential therapeutic alternative to treat skin disorders associated with oxidative stress.

C-1001: Small molecule inhibitors of ice recrystallization – From design to mechanism of action and applications

Ice recrystallization has been identified as a significant contributor to cellular injury and death during cryopreservation. Unfortunately, many cryopreservation protocols are suboptimal. Thus, interest has arisen in designing novel ice recrystallization inhibitors and using these moleclues as cryoprotectants. Recently, our laboratory has reported several classes of small molecules that have the ability to inhibit ice recrystallization. These classes include amino acid-based organogelators, non-ionic carbohydrate-based amphiphiles (aryl and alkyl alditols) and O-linked alkyl and aryl glycoside derivatives. We have conducted comprehensive structure function studies to optimize the ability of these molecules to inhibit ice recrystallization and also facilitate a more thorough understanding of their mechanism of action. These studies have revealed that long alkyl chains or substituted aryl groups that add “hydrophobicity” to the molecule are essentail for potent inhibition of ice recrystallization and that the relative position of these groups is important. In addition, the choice of counterion can have a dramatic effect on the ability of these compounds to inhibit ice recrystallization. Collectively, our results suggest that a high degree of hydration of these small molecules (and their counterions where appropriate) is a prerequisite for a potent inhibitor of ice recrystallization.?A number of these small molecules described above have been investigated as cryoprotectants and have been found to freeze human red blood cells (RBCs) using low amounts of glycerol. Deglycerolization studies and analysis of RBC recoveries have revealed important insights in the mechanism of action of these small molecule ice recrystallization inhibitors.

Preparation of two glycoside hydrolases for use in micro-aqueous media

Enzymatic synthesis of alkyl glycosides using glycoside hydrolases is well studied, but has yet to reach industrial scale, primarily due to limited yields. Reduced water content should increase yields by limiting the unwanted hydrolytic side reaction. However, previous studies have shown that a reduction in water content surprisingly favors hydrolysis over transglycosylation. In addition, glycoside hydrolases normally require a high degree of hydration to function efficiently. This study compares six enzyme preparation methods to improve resilience and activity of two glycoside hydrolases from Thermotoga neapolitana (TnBgl3B and TnBgl1A) in micro-aqueous hexanol. Indeed, when adsorbed onto Accurel MP-1000 both enzymes increasingly favored transglycosylation over hydrolysis at low hydration, in contrast to freeze-dried or untreated enzyme. Additionally, they displayed 17–70× higher reaction rates compared to freeze-dried enzyme at low water activity, while displaying comparable or lower activity for fully hydrated systems. These results provide valuable information for use of enzymes under micro-aqueous conditions and build toward utilizing the full synthetic potential of glycoside hydrolases.