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1.
Ultrathin MoS2 Nanosheets as Anode Materials for Sodium‐Ion Batteries with Superior Performance
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Few‐layer MoS2 nanosheets are successfully synthesized using a simple and scalable ultrasonic exfoliation technique. The thicknesses of the MoS2 nanosheets ares about 10 nm as measured by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The unique nanosheet architecture renders the high‐rate transportation of sodium ions due to the short diffusion paths provided by ultrathin thickness and the large interlayer space within the MoS2 crystal structure (d(002) = 6.38 Å). When applied as anode materials in sodium‐ion batteries, MoS2 nanosheets exhibit a high, reversible sodium storage capacity and excellent cyclability. The MoS2 nanosheets also demonstrate good electrochemical performance at high current densities. 相似文献
2.
MoS2/Graphene Nanosheets from Commercial Bulky MoS2 and Graphite as Anode Materials for High Rate Sodium‐Ion Batteries
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Dan Sun Delai Ye Ping Liu Yougen Tang Jun Guo Lianzhou Wang Haiyan Wang 《Liver Transplantation》2018,8(10)
Tuning heterointerfaces between hybrid phases is a very promising strategy for designing advanced energy storage materials. Herein, a low‐cost, high‐yield, and scalable two‐step approach is reported to prepare a new type of hybrid material containing MoS2/graphene nanosheets prepared from ball‐milling and exfoliation of commercial bulky MoS2 and graphite. When tested as an anode material for a sodium‐ion battery, the as‐prepared MoS2/graphene nanosheets exhibit remarkably high rate capability (284 mA h g?1 at 20 A g?1 (≈30C) and 201 mA h g?1 at 50 A g?1 (≈75C)) and excellent cycling stability (capacity retention of 95% after 250 cycles at 0.3 A g?1). Detailed experimental measurements and density functional theory calculation reveal that the functional groups in 2D MoS2/graphene heterostructures can be well tuned. The impressive rate capacity of the as‐prepared MoS2/graphene hybrids should be attributed to the heterostructures with a low degree of defects and residual oxygen containing groups in graphene, which subsequently improve the electronic conductivity of graphene and decrease the Na+ diffusion barrier at the MoS2/graphene interfaces in comparison with the acid treated one. 相似文献
3.
Iqbal Ahmad Zubair Anwar Sofia Ahmed Muhammad Ali Sheraz Raheela Bano Ambreen Hafeez 《AAPS PharmSciTech》2015,16(5):1122-1128
The kinetics of photolysis of riboflavin (RF) in water (pH 7.0) and in organic solvents (acetonitrile, methanol, ethanol, 1-propanol, 1-butanol, ethyl acetate) has been studied using a multicomponent spectrometric method for the assay of RF and its major photoproducts, formylmethylflavin and lumichrome. The apparent first-order rate constants (kobs) for the reaction range from 3.19 (ethyl acetate) to 4.61 × 10−3 min−1 (water). The values of kobs have been found to be a linear function of solvent dielectric constant implying the participation of a dipolar intermediate along the reaction pathway. The degradation of this intermediate is promoted by the polarity of the medium. This indicates a greater stabilization of the excited-triplet states of RF with an increase in solvent polarity to facilitate its reduction. The rate constants for the reaction show a linear relation with the solvent acceptor number indicating the degree of solute–solvent interaction in different solvents. It would depend on the electron-donating capacity of RF molecule in organic solvents. The values of kobs are inversely proportional to the viscosity of the medium as a result of diffusion-controlled processes.KEY WORDS: dielectric constant, kinetics, photolysis, riboflavin, solvent effect, viscosity 相似文献
4.
In a visualized example of the ancient past connecting with modern times, we describe the preparation and exfoliation of CaCuSi4O10 and BaCuSi4O10, the colored components of the historic Egyptian blue and Han blue pigments. The bulk forms of these materials are synthesized by both melt flux and solid-state routes, which provide some control over the crystallite size of the product. The melt flux process is time intensive, but it produces relatively large crystals at lower reaction temperatures. In comparison, the solid-state method is quicker yet requires higher reaction temperatures and yields smaller crystallites. Upon stirring in hot water, CaCuSi4O10 spontaneously exfoliates into monolayer nanosheets, which are characterized by TEM and PXRD. BaCuSi4O10 on the other hand requires ultrasonication in organic solvents to achieve exfoliation. Near infrared imaging illustrates that both the bulk and nanosheet forms of CaCuSi4O10 and BaCuSi4O10 are strong near infrared emitters. Aqueous CaCuSi4O10 and BaCuSi4O10 nanosheet dispersions are useful because they provide a new way to handle, characterize, and process these materials in colloidal form. 相似文献
5.
Hyeonyeol Jeon Jae‐Min Jeong Heon Gyu Kang Hyung‐Jin Kim Jeyoung Park Do Hyun Kim Young Mee Jung Sung Yeon Hwang Young‐Kyu Han Bong Gill Choi 《Liver Transplantation》2018,8(18)
Highly conductive and ultrathin 2D nanosheets are of importance for the development of portable electronics and electric vehicles. However, scalable production and rational design for highly electronic and ionic conductive 2D nanosheets still remain a challenge. Herein, an industrially adoptable fluid dynamic exfoliation process is reported to produce large quantities of ionic liquid (IL)‐functionalized metallic phase MoS2 (m‐MoS2) and defect‐free graphene (Gr) sheets. Hybrid 2D–2D layered films are also fabricated by incorporating Gr sheets into compact m‐MoS2 films. The incorporated IL functionalities and Gr sheets prevent aggregation and restacking of the m‐MoS2 sheets, thereby creating efficient and rapid ion and electron pathways in the hybrid films. The hybrid film with a high packing density of 2.02 g cm?3 has an outstanding volumetric capacitance of 1430.5 F cm?3 at 1 A g?1 and an extremely high rate capability of 80% retention at 1000 A g?1. The flexible supercapacitor assembled using a polymer‐gel electrolyte exhibits excellent resilience to harsh electrochemical and mechanical conditions while maintaining an impressive rate performance and long cycle life. Successful achievement of an ultrahigh volumetric energy density (1.14 W h cm?3) using an organic electrolyte with a wide cell voltage of ≈3.5 V is demonstrated. 相似文献
6.
Vertically Aligned MoS2 Nanosheets Patterned on Electrochemically Exfoliated Graphene for High‐Performance Lithium and Sodium Storage
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Gang Wang Jian Zhang Sheng Yang Faxing Wang Xiaodong Zhuang Klaus Müllen Xinliang Feng 《Liver Transplantation》2018,8(8)
Molybdenum disulfide (MoS2) has been recognized as a promising anode material for high‐energy Li‐ion (LIBs) and Na‐ion batteries (SIBs) due to its apparently high capacity and intriguing 2D‐layered structure. The low conductivity, unsatisfied mechanical stability, and limited active material utilization are three key challenges associated with MoS2 electrodes especially at high current rates and mass active material loading. Here, vertical MoS2 nanosheets are controllably patterned onto electrochemically exfoliated graphene (EG). Within the achieved hierarchical architecture, the intimate contact between EG and MoS2 nanosheets, interconnected network, and effective exposure of active materials by vertical channels simultaneously overcomes the above three problems, enabling high mechanical integrity and fast charge transport kinetics. Serving as anode material for LIBs, EG‐MoS2 with 95 wt% MoS2 content delivered an ultrahigh‐specific capacity of 1250 mA h g?1 after 150 stable cycles at 1 A g?1, which is among the highest values in all reported MoS2 electrodes, and excellent rate performance (970 mA h g?1 at 5 A g?1). Moreover, impressive cycling stability (509 mA h g?1 at 1 A g?1 after 250 cycles) and rate capability (423 mA h g?1 at 2 A g?1) were also achieved for SIBs. The area capacities reached 1.27 and 0.49 mA h cm?2 at ≈1 mA cm?2 for LIBs and SIBs, respectively. This work may inspire the development of new 2D hierarchical structures for high efficiency energy storage and conversion. 相似文献
7.
Secundo F Fialà S Fraaije MW de Gonzalo G Meli M Zambianchi F Ottolina G 《Biotechnology and bioengineering》2011,108(3):491-499
A broader exploitation of enzymes in organic synthesis can be achieved by increasing their tolerance toward organic solvents. In this study, the stability and activity of Baeyer–Villiger monooxygenases from Thermobifida fusca (PAMO) and Acinetobacter sp. (CHMO) in the presence of water miscible organic solvents were compared. PAMO was more stable than CHMO. The concentration of solvent (v/v) at which it halved its activity (C50) was 4‐ to 16‐fold higher than that observed for CHMO. For PAMO, the C50 varied from 16% to 55% of solvent and followed the destabilizing order methanol < ethanol < 1,4‐dioxane < acetonitrile < trifluoroethanol. In the case of CHMO, the maximal C50 was 7% with methanol and even lower with the other solvents. Therefore, methanol was the most tolerated solvent. In the case of PAMO, methanol induced a significant increase of enzyme activity (up to fivefold), which was optimal at 20% (v/v) solvent. Only minor spectral variations were observed with PAMO in 20% methanol, suggesting that the increase of activity observed in this condition is not due to marked conformational changes. Fluorescence and circular dichroism analyses showed that the lower stability of CHMO toward organic solvent correlates with a more pronounced destructive effect on its secondary and tertiary structure. A possible rationale for the higher stability of PAMO could be inferred from inspection of the PAMO and CHMO (two enzymes of similar size) structure, which revealed a higher (up to twofold) number of ionic bridges in PAMO with respect to CHMO. Biotechnol. Bioeng. 2011; 108:491–499. © 2010 Wiley Periodicals, Inc. 相似文献
8.
Mats Reslow Patrick Adlercreutz Bo Mattiasson 《Applied microbiology and biotechnology》1987,26(1):1-8
Summary The influence of solvents on enzymatic activity and stability was investigated. As a model reaction the -chymotrypsin-catalyzed esterification of N-acetyl-l-phenylalanine with ethanol was used. The enzyme was adsorbed on porous glass beads and used in various solvents. Small amounts of water were added to increase the enzymatic activity. These enzyme preparations obeyed. Michaelis-Menten kinetics. K
m,app decreased slightly with the log P value of the solvent while V
app increased markedly with the log P value. Log P values were also useful for generalizing the influence of solvents on enzyme stability. The enzyme preparations showed a markedly higher thermostability in dry solvents having log P values >0.7 than in less hydrophobic solvents.Also the operational stability was better in the more hydrophobic solvents. The amount of water added to the enzyme preparations greatly influenced the initial reaction rates. For some solvents optimal water contents were determined. The thermostability decreased with increasing water content.The observations are summarized in the conclusion that more hydrophobic solvents are preferable to less hydrophobic ones. The log P value gives a good guidance when selecting an organic solvent for enzymatic conversions. 相似文献
9.
Jia‐Zhao Wang Lin Lu Mustafa Lotya Jonathan N. Coleman Shu‐Lei Chou Hua‐Kun Liu Andrew I. Minett Jun Chen 《Liver Transplantation》2013,3(6):798-805
Layered MoS2 prepared by liquid‐phase exfoliation has been blended with single‐walled carbon nanotubes (SWNTs) to form novel composite thin films for lithium battery applications. The films were formed by vacuum filtration of blended dispersions onto nitrocellulose membranes. The resulting composite films were transferred onto Cu foil electrodes via a facile filtration/wet transfer technique from nitrocellulose membranes. The morphology of the film was characterised by field emission scanning electron microscopy, which suggests that the MoS2‐SWNT composite film shows good adherence to the Cu foil substrate. The MoS2‐SWNT composite thin films show strong electrochemical performance at different charge‐discharge rates. The capacity of a MoS2‐SWNT composite film with thickness of 1 μm is approximately 992 mAh g?1 after 100 cycles. The morphology study showed that the MoS2‐SWNT thin film retains structural integrity after 100 cycles, while the MoS2 thin film without SWNTs displays significant cracking. In addition, the novel composite thin film preparation and transfer protocols developed in this study could be extended to the preparation of various layered‐material‐based composite films, with the potential for new device designs for energy applications. 相似文献
10.
Ion Transport Nanotube Assembled with Vertically Aligned Metallic MoS2 for High Rate Lithium‐Ion Batteries
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Yucong Jiao Alolika Mukhopadhyay Yi Ma Lei Yang Ahmed M. Hafez Hongli Zhu 《Liver Transplantation》2018,8(15)
Metallic phase molybdenum disulfide (MoS2) is well known for orders of magnitude higher conductivity than 2H semiconducting phase MoS2. Herein, for the first time, the authors design and fabricate a novel porous nanotube assembled with vertically aligned metallic MoS2 nanosheets by using the scalable solvothermal method. This metallic nanotube has the following advantages: (i) intrinsic high electrical conductivity that promotes the rate performance of battery and eliminates the using of conductive additive; (ii) hierarchical, hollow, porous, and aligned structure that assists the electrolyte transportation and diffusion; (iii) tubular structure that avoids restacking of 2D nanosheets, and therefore maintains the electrochemistry cycling stability; and (iv) a shortened ion diffusion path, that improves the rate performance. This 1D metallic MoS2 nanotube is demonstrated to be a promising anode material for lithium‐ion batteries. The unique structure delivers an excellent reversible capacity of 1100 mA h g?1 under a current density of 5 A g?1 after 350 cycles, and an outstanding rate performance of 589 mA h g?1 at a current density of 20 A g?1. Furthermore, attributed to the material's metallic properties, the electrode comprising 100% pure material without any additive provides an ideal system for the fundamental electrochemical study of metallic MoS2. This study first reveals the characteristic anodic peak at 1.5 V in cyclic voltammetry of metallic MoS2. This research sheds light on the fabrication of metallic 1D, 2D, or even 3D structures with 2D nanosheets as building blocks for various applications. 相似文献
11.
The equilibrium of hydrolytic reactions can be shifted toward condensation by carrying out the reaction at low water concentration. The rate and yield of urease-catalyzed urea synthesis from (NH4)2CO3 or NH4HCO3 has been examined as a function of water concentration (in mixtures with organic solvents), substrate and H+ concentration, and polarity of the nonaqueous component of the solvent. Similar effects of organic solvents are observed on the reaction rate in both directions; the results suggest that at least in some conditions the reaction proceeds through nonenzymically formed carbamate. The equilibrium concentration of urea, in 50% () water, varies over 10-fold, depending on the nature of the nonaqueous component of the solvent; nonhydroxylic solvents such as acetone given the highest yield. Solubility measurements suggest that the interactions of the solvent mixtures with (NH4)2CO3 (or carbamate), rather than urea, are responsible for the variations in urea yield. Activities of water and the ionic components of the equilibrium are strongly influenced by the nature of the nonaqueous component of the solvent, as well as its concentration. 相似文献
12.
The effect of organic solvent on the structure and dynamics of proteins was investigated by multiple molecular dynamics simulations (1 ns each) of Candida rugosa lipase in water and in carbon tetrachloride. The choice of solvent had only a minor structural effect. For both solvents the open and the closed conformation of the lipase were near to their experimental X-ray structures (C rms deviation 1–1.3 Å). However, the solvents had a highly specific effect on the flexibility of solvent-exposed side chains: polar side chains were more flexible in water, but less flexible in organic solvent. In contrast, hydrophobic residues were more flexible in organic solvent, but less flexible in water. As a major effect solvent changed the dynamics of the lid, a mobile element involved in activation of the lipase, which fluctuated as a rigid body about its average position. While in water the deviations were about 1.6 Å, organic solvent reduced flexibility to 0.9 Å. This increase rigidity was caused by two salt bridges (Lys85–Asp284, Lys75–Asp79) and a stable hydrogen bond (Lys75–Asn 292) in organic solvent. Thus, organic solvents stabilize the lid but render the side chains in the hydrophobic substrate-binding site more mobile.
Figure Superimposition of open (black, PDB entry 1CRL) and closed (gray, PDB entry 1TRH) conformers of C. rugosa lipase. The mobile lid is indicatedThis revised version was published online in October 2004 with corrections to the Graphical Abstract. 相似文献
13.
The thermal stability of Candida rugosa (C. rugosa) lipase was investigated and compared in n-hexane, benzene, dibutyl-ether as well as [bmim]PF6 and [omim]PF6 ionic liquids and the effect of solvent polarity and water activity were evaluated. Deactivation of the enzyme followed a series-type kinetic model. First order deactivation rate constants and the ratios of specific activities were determined and the kinetics of deactivation were studied. Among the organic solvents, the best stability was observed in n-hexane with a half-life of 6.5?h at water activity of 0.51. In ionic liquids, however, even longer half lives were obtained, and the enzyme was stable in these solvents at 50°C. The highest half-life times were obtained in [bmim]PF6 (12.3?h) and [omim]PF6 (10.6?h). A direct correlation was found between solvent polarity and thermal stability since the higher the polarity of the solvent, the lower was the stability decrease at 50°C comparing to that at 30°C. 相似文献
14.
Dual‐Functional N Dopants in Edges and Basal Plane of MoS2 Nanosheets Toward Efficient and Durable Hydrogen Evolution
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Wen Xiao Peitao Liu Jingyan Zhang Wendong Song Yuan Ping Feng Daqiang Gao Jun Ding 《Liver Transplantation》2017,7(7)
Herein, the authors explicitly reveal the dual‐functions of N dopants in molybdenum disulfide (MoS2) catalyst through a combined experimental and first‐principles approach. The authors achieve an economical, ecofriendly, and most efficient MoS2‐based hydrogen evolution reaction (HER) catalyst of N‐doped MoS2 nanosheets, exhibiting an onset overpotential of 35 mV, an overpotential of 121 mV at 100 mA cm?2 and a Tafel slope of 41 mV dec?1. The dual‐functions of N dopants are (1) activating the HER catalytic activity of MoS2 S‐edge and (2) enhancing the conductivity of MoS2 basal plane to promote rapid charge transfer. Comprehensive electrochemical measurements prove that both the amount of active HER sites and the conductivity of N‐doped MoS2 increase as a result of doping N. Systematic first‐principles calculations identify the active HER sites in N‐doped MoS2 edges and also illustrate the conducting charges spreading over N‐doped basal plane induced by strong Mo 3d –S 2p –N 2p hybridizations at Fermi level. The experimental and theoretical research on the efficient HER catalysis of N‐doped MoS2 nanosheets possesses great potential for future sustainable hydrogen production via water electrolysis and will stimulate further development on nonmetal‐doped MoS2 systems to bring about novel high‐performance HER catalysts. 相似文献
15.
Bacteria tolerant to organic solvents 总被引:5,自引:0,他引:5
The toxic effects that organic solvents have on whole cells is an important drawback in the application of these solvents
in environmental biotechnology and in the production of fine chemicals by whole-cell biotransformations. Hydrophobic organic
solvents, such as toluene, are toxic for living organisms because they accumulate in and disrupt cell membranes. The toxicity
of a compound correlates with the logarithm of its partition coefficient with octanol and water (log P
ow). Substances with a log P
ow
value between 1 and 5 are, in general, toxic for whole cells. However, in recent years different bacterial strains have been
isolated and characterized that can adapt to the presence of organic solvents. These strains grow in the presence of a second
phase of solvents previously believed to be lethal. Different mechanisms contributing to the solvent tolerance of these strains
have been found. Alterations in the composition of the cytoplasmic and outer membrane have been described. These adaptations
suppress the effects of the solvents on the membrane stability or limit the rate of diffusion into the membrane. Furthermore,
changes in the rate of the biosynthesis of the phospholipids were reported to accelerate repair processes. In addition to
these adaptation mechanisms compensating the toxic effect of the organic solvents, mechanisms do exist that actively decrease
the amount of the toxic solvent in the cells. An efflux system actively decreasing the amount of solvents in the cell has
been described recently. We review here the current knowledge about exceptional strains that can grow in the presence of toxic
solvents and the mechanisms responsible for their survival.
Received: January 22, 1998 / Accepted: February 16, 1998 相似文献
16.
Md. Zahid Kamal Poornima Yedavalli Mandar V. Deshmukh Nalam Madhusudhana Rao 《Protein science : a publication of the Protein Society》2013,22(7):904-915
Studying alterations in biophysical and biochemical behavior of enzymes in the presence of organic solvents and the underlying cause(s) has important implications in biotechnology. We investigated the effects of aqueous solutions of polar organic solvents on ester hydrolytic activity, structure and stability of a lipase. Relative activity of the lipase monotonically decreased with increasing concentration of acetone, acetonitrile, and DMF but increased at lower concentrations (upto ~20% v/v) of dimethylsulfoxide, isopropanol, and methanol. None of the organic solvents caused any appreciable structural change as evident from circular dichorism and NMR studies, thus do not support any significant role of enzyme denaturation in activity change. Change in 2D [15N, 1H]‐HSQC chemical shifts suggested that all the organic solvents preferentially localize to a hydrophobic patch in the active‐site vicinity and no chemical shift perturbation was observed for residues present in protein's core. This suggests that activity alteration might be directly linked to change in active site environment only. All organic solvents decreased the apparent binding of substrate to the enzyme (increased Km); however significantly enhanced the kcat. Melting temperature (Tm) of lipase, measured by circular dichroism and differential scanning calorimetry, altered in all solvents, albeit to a variable extent. Interestingly, although the effect of all organic solvents on various properties on lipase is qualitatively similar, our study suggest that magnitudes of effects do not appear to follow bulk solvent properties like polarity and the solvent effects are apparently dictated by specific and local interactions of solvent molecule(s) with the protein. 相似文献
17.
Summary A new technique is presented to determine gas-to-water overall volumetric mass transfer coefficients (k
l
a) in a stirred-tank reactor containing solvent-in-water dispersions. The compound to be transferred from the gas to the water was toluene; the water-immiscible organic solvent was FC40, a perfluorocarbon. The k
l
a was determined in steady-state conditions in the absence of biological consumption. Toluene removal was achieved by passing a continuous flow of toluene-free water through the reactor. When solvent was present it was separated from the water at the reactor outlet by means of a small settler and recycled back to the vessel. The k
l
a was found to increase with the FC40 volume fraction. An enhancement of 1.9 times on an aqueous-phase-volume basis was found at 15 % (v/v) FC40. 相似文献
18.
Summary The influence of pH, temperature, substrate concentration and organic solvents (dimethylformamide, dimethylsulfoxide) on the -chymotrypsin stability in a water/organic solvent system was studied. The enzyme activity was measured as the dipeptide, AcPheLeuNH2 synthesis and the ester substrate hydrolysis. Enzyme stability was enhanced by lower pH and temperature values and higher substrate concentrations. Dimethylsulfoxide allowed an higher enzyme stability than dimethylformamide. -Chymotrypsin displayed an higher stability in the water medium when it was compared to the organic system. 相似文献
19.
Molybdenum Disulfide/Nitrogen‐Doped Reduced Graphene Oxide Nanocomposite with Enlarged Interlayer Spacing for Electrocatalytic Hydrogen Evolution
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Yu‐Jia Tang Yu Wang Xiao‐Li Wang Shun‐Li Li Wei Huang Long‐Zhang Dong Chun‐Hui Liu Ya‐Fei Li Ya‐Qian Lan 《Liver Transplantation》2016,6(12)
Facile design of low‐cost and highly active catalysts from earth‐abundant elements is favorable for the industrial application of water splitting. Here, a simple strategy to synthesize an ultrathin molybdenum disulfide/nitrogen‐doped reduced graphene oxide (MoS2/N‐RGO‐180) nanocomposite with the enlarged interlayer spacing of 9.5 Å by a one‐step hydrothermal method is reported. The synergistic effects between the layered MoS2 nanosheets and N‐doped RGO films contribute to the high activity for hydrogen evolution reaction (HER). MoS2/N‐RGO‐180 exhibits the excellent catalytic activity with a low onset potential of ?5 mV versus reversible hydrogen elelctrode (RHE), a small Tafel slope of 41.3 mV dec?1, a high exchange current density of 7.4 × 10?4 A cm?2, and good stability over 5 000 cycles under acidic conditions. The HER performance of MoS2/N‐RGO‐180 nanocomposite is superior to the most reported MoS2‐based catalysts, especially its onset potential and exchange current density. In this work, a novel and simple method to the preparation of low‐cost MoS2‐based electrocatalysts with the extraordinary HER performance is presented. 相似文献
20.
《Journal of Molecular Catalysis .B, Enzymatic》2011,68(3-4):208-213
Benzaldehyde lyase from Pseudomonas fluorescens Biovar I [BAL; E.C.4.1.2.38] catalyzes the stereoselective formation of C–C bonds coupling aldehydes to generate alpha-hydroxy ketones. A broad range of poorly water-soluble substrates are accepted in forward and reverse reactions. In this study, the stability of BAL in aqueous–organic biphasic systems as promising reaction media was systematically investigated using methyl-tert-butylether, 2-octanone, and toluene as the organic phase. Surprisingly, a strong individual molecular toxicity of these water-immiscible solvents was observed along with the interfacial toxicity exerted by the aqueous–organic interfaces. They could be considerably reduced by covalent attachment of methoxy-poly(ethylene) glycol (mPEG750 and mPEG2000) to the enzyme surface increasing the half-life by a factor of up to 18. However, under reactive conditions solvent effects were strongly superimposed by an additional deactivating effect, possibly caused by the aldehyde substrate, and no differences between unmodified and modified BAL were detectable. For technical application of the enzyme in aqueous–organic biphasic media additional strategies for stabilization will therefore be desirable. 相似文献