Home About us Contact
|
Home About us Contact | ||
|
|
||
Microcrystalline Cellulose (microcrystalline + cellulose)
Selected AbstractsOlefin metathesis applied to cellulose derivatives,Synthesis, analysis, and properties of new crosslinked cellulose plastic filmsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2005Nicolas Joly Abstract New crosslinked cellulose-based plastic films were synthesized with olefin metathesis as a crosslinking reaction. Microcrystalline cellulose was first dissolved in a lithium chloride/N,N -dimethylacetamide solvent system and acylated by ,-undecenoyl chloride under microwave irradiation with N,N -dimethyl-4-aminopyridine as the catalyst. Cellulose unsaturated fatty acyl esters with a degree of substitution (DS) ranging from 1.4 to 2.0 were then crosslinked by olefin metathesis with a first generation Grubbs catalyst. Crosslinking ratios (T) ranging from 20 to 90% were obtained for low catalyst amounts (<1.2%), but gels appeared when T was too high. To avoid this gel formation, cellulose was acylated with a mixture of lauroyl and ,-undecenoyl chlorides. This internal dilution allowed us to obtain films of every case and various T (varying from 10 to 80% for a catalyst amount below 3.5%). Plastics were characterized by Fourier transform infrared (FTIR) spectroscopy, and the fatty acid mixture resulting from the hydrolysis of cellulose esters were analyzed by gas chromatography (GC) and NMR spectroscopy. Mechanical properties showed that the elastic modulus and tensile failure stress was higher when the plastic films were crosslinked. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 407,418, 2005 [source] Application of 1-Allyl-3-(1-butyl)imidazolium Chloride in the Synthesis of Cellulose Esters: Properties of the Ionic Liquid, and Comparison with Other SolventsMACROMOLECULAR BIOSCIENCE, Issue 8 2009Ludmila C. Fidale Abstract The ionic liquid (IL), 1-allyl-3-(1-butyl)imidazolium chloride (AlBuImCl), has been synthesized and its properties determined. Increase in the temperature increased its conductivity and decreased its density, polarity, and viscosity. Microcrystalline cellulose (MCC), dissolves in this IL by heating at 80,°C; this did not affect its degree of polymerization, decreased its index of crystallinity (Ic), and changed in morphology after regeneration. Convenient acylation of MCC was achieved by using 50% excess anhydride at 80,°C, for 24 or 48 h for acetic and butyric anhydride, respectively. The composition of the mixed esters depended on the initial ratio of the anhydrides, and their order of addition. [source] Cellulose-binding modules from extracellular matrix proteins of Dictyostelium discoideum stalk and sheathFEBS JOURNAL, Issue 15 2001Yingzi Wang Cellulose-binding modules (CBMs) of two extracellular matrix proteins, St15 and ShD, from the slime mold Dictyostelium discoideum were expressed in Escherichia coli. The expressed proteins were purified to >,98% purity by extracting inclusion bodies at pH 11.5 and refolding proteins at pH 7.5. The two refolded CBMs bound tightly to amorphous phosphoric acid swollen cellulose (PASC), but had a low affinity toward xylan. Neither protein exhibited cellulase activity. St15, the stalk-specific protein, had fourfold higher binding affinity toward microcrystalline cellulose (Avicel) than the sheath-specific ShD CBM. St15 is unusual in that it consists of a solitary CBM homologous to family IIa CBMs. Sequence analysis of ShD reveals three putative domains containing: (a) a C-terminal CBM homologous to family IIb CBMs; (b) a Pro/Thr-rich linker domain; and (c) a N-terminal Cys-rich domain. The biological functions and potential role of St15 and ShD in building extracellular matrices during D. discoideum development are discussed. [source] Application of ultrasonic waves in activation of microcrystalline celluloseJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Xianling Wang Abstract In this work, microcrystalline cellulose (MCC) was activated with ultrasonic waves. The influences of ultrasonic treatment on the changes of supramolecular structures and morphology structure were studied by WAXS and SEM. The accessibility of the MCC was characterized by water retention value (WRV) and specific surficial area. The influence of ultrasonic treatment on the reactivity of MCC was investigated through the reaction of MCC being oxidized into 2,3-diadehyde cellulose (DAC) by periodate sodium. The mechanism of the reactivity change of ultrasonically treated MCC was examined. The results showed that the degree of crystallinity of MCC decreased and the degree of polymerization showed little change after treatment with ultrasonic waves. The morphologial variation of the treated MCC was significant when compared with the untreated MCC, which contribute to the improvement of accessibility. The aldehyde content of DAC prepared from ultrasonically treated MCC was improved from 64.19 to 85.00%, indicating that the regioselective oxidation reactivity of MCC was significantly improved. The aldehyde content was found to first increase with time of ultrasonic treatment to a point, and then decrease as time progressed. In addition, the aldehyde content was found to increase with an increase in ultrasonic power. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Bootstrap methods for assessing the performance of near-infrared pattern classification techniquesJOURNAL OF CHEMOMETRICS, Issue 5 2002Brandye M. Smith Abstract Two parametric bootstrap techniques were applied to near-infrared (NIR) pattern classification models for two classes of microcrystalline cellulose, Avicel® PH101 and PH102, which differ only in particle size. The development of pattern classification models for similar substances is difficult, since their characteristic clusters overlap. Bootstrapping was used to enlarge small test sets for a better approximation of the overlapping area of these nearly identical substances, consequently resulting in better estimates of misclassification rates. A bootstrap that resampled the residuals, referred to as the outside model space bootstrap in this paper, and a novel bootstrap that resampled principal component scores, referred to as the inside model space bootstrap, were studied. A comparison revealed that classification rates for both bootstrap techniques were similar to the original test set classification rates. The bootstrap method developed in this study, which resampled the principal component scores, was more effective for estimating misclassification volumes than the residual-resampling method. Copyright © 2002 John Wiley & Sons, Ltd. [source] Kinetics of cellulose conversion at 25 MPa in sub- and supercritical waterAICHE JOURNAL, Issue 1 2004Mitsuru Sasaki Abstract Experiments of microcrystalline cellulose conversion in subcritical and supercritical water were conducted at temperatures between 290 and 400°C, a pressure of 25 MPa, and residence times of 0.02,13.1 s using a continuous-flow-type microreactor. First, the reaction mechanism of microcrystalline cellulose in subcritical and supercritical water was proposed on the basis of detailed product analyses. Next, the kinetic description of this reaction in subcritical and supercritical water using a grain model was carried out to verify the proposed reaction mechanism and consequently found that the reaction-rate models were able to express the reaction of microcrystalline cellulose at identical conditions. © 2004 American Institute of Chemical Engineers AIChE J, 50: 192,202, 2004 [source] Evaluation of a rotary tablet press simulator as a tool for the characterization of compaction properties of pharmaceutical productsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2010F. Michaut Abstract The Stylcam 100R, a rotary press simulator, was designed to simulate speed profiles of rotary tablet presses. Such a simulator was qualified by numerous laboratories and, actually, its ability to be used for studying the behaviour of powders under pressure should be examined. Then, the purpose of this work was to investigate the performances of the Stylcam 100R for characterizing the compaction behaviour and the tabletting properties of pharmaceutical powders. The compressibility of three pharmaceutical excipients (microcrystalline cellulose, dicalcium phosphate dihydrate and ,-lactose monohydrate) was studied. Four compression speeds were used on the compaction simulator. Force,displacement cycles were associated with two energy parameters, the specific total energy (Estot) and the specific expansion energy (Esexp). The mean yield pressure was calculated from Heckel's plots obtained with the in-die method. The diametral tensile strength of compacts was measured in order to evaluate mechanical properties. To evaluate the accuracy of all these parameters, a comparative study was carried out on an eccentric instrumented press. The values of energy parameters and tensile strengths of tablets are close between the eccentric press and the compaction simulator, whatever the compression speed on the latter. The mean yield pressure values obtained using the two presses are different. Finally, the Stylcam 100R seems to be a good tool for characterising tabletting properties of powders, except for the Heckel's model probably due to an unadapted equation of deformation and a lack of accuracy of the displacement transducers. Future improvements should allow correcting these two points. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2874,2885, 2010 [source] The rheological properties of modified microcrystalline cellulose containing high levels of model drugsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2009Paul E. Knight Abstract The rheological properties of different types of microcrystalline cellulose (MCC) mixed with model drugs and water have been evaluated to identify the influence of sodium carboxymethylcellulose (SCMC) added to the cellulose during preparation. A ram extruder was used as a capillary rheometer. The mixtures consisted of 20% spheronizing agent (standard grade MCC or modified types with 6% or 8% of low viscosity grade SCMC) and 80% of ascorbic acid, ibuprofen or lactose monohydrate. The introduction of SCMC changed all rheological parameters assessed. It produced more rigid systems, requiring more stress to induce and maintain flow. Degree of non-Newtonian flow, angle of convergence, extensional viscosity, yield and die land shear stress at zero velocity, and static wall friction were increased, but recoverable shear and compliance were decreased. The presence of SCMC did not remove the influence of the type of drug. The mixture of ibuprofen and standard MCC had the lowest values for shear stress as a function of the rate of shear, extensional viscosity, and angle of convergence, but the highest values for recoverable shear and compliance. The findings indicate that the system has insufficient rigidity to form pellets. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:2160,2169, 2009 [source] A near-infrared spectroscopic investigation of relative density and crushing strength in four-component compactsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2009Steven M. Short Abstract Near-infrared spectroscopy (NIRS) is commonly employed for the analysis of chemical and physical attributes of intact pharmaceutical compacts. Specifically, NIRS has proven useful in the nondestructive measurement of tablet hardness or crushing strength. Near-infrared (NIR) reflectance and transmittance spectra were acquired for 174 13-mm compacts, which were produced according to a four-constituent mixture design (29 points) composed of anhydrous theophylline, lactose monohydrate, microcrystalline cellulose, and soluble starch. Six compacts were produced for each design point by compacting at multiple pressures. Physical testing and regression analyses were used to model the effect of variation in relative density (and crushing strength) on NIR spectra. Chemometric analyses demonstrated that the overall spectral variance was strongly influenced by anhydrous theophylline as a result of the experimental design and the component's spectroscopic signature. The calibration for crushing strength was more linear than the relative density model, although accuracy was poorer in comparison to the density model due to imprecision of the reference measurements. Based on the consideration of reflectance and transmittance measurements, a revised rationalization for NIR sensitivity to compact hardness is presented. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1095,1109, 2009 [source] Combined effects of wetting, drying, and microcrystalline cellulose type on the mechanical strength and disintegration of pelletsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2009Maria Balaxi Abstract Effects of wetting and drying conditions on micromeritic, mechanical and disintegration properties of microcrystalline cellulose (MCC) pellets were evaluated. Extrusion/spheronization and three drying methods (fluidized bed, microwaves, and freeze drying) were applied using two wetting liquids (water or water-isopropanol 60:40 w/w) and three MCC types: (standard, silicified, and modified). Additionally, the effects of drying method were compared on highly porous pellets prepared by the incorporation and extraction of pore former (NaCl). It was found that the drying method has the greatest effect on the pellet size and porosity followed by the wetting liquid. The modification of MCC resulted in reduced water retention ability, implying hornification, increased porosity, reduced resistance to deformation and tensile strength of pellets. The disintegration time also decreased markedly due to the modification but only in the low porosity range <37%. Silicification increased greatly the disintegration time of the low porosity pellets (<14%). Combination of water-isopropanol, freeze drying and modified MCC gave the greatest increase in pellet size and porosity. The increase in pellet porosity caused exponential reduction in the resistance to deformation, tensile strength and disintegration time, as expected. Compared to fluidized bed, the freeze drying resulted in 20,30% higher porosity for pellets prepared without pore former and 6% for those with pore former, indicating the possibility of preparing highly porous pellets by employing freeze drying. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:676,689, 2009 [source] Compaction of pharmaceutical tablets with different polymer matrices studied by FTIR imaging and X-ray microtomographyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2008Patrick Wray Abstract Water soluble polymers are often used in tablet compaction for their desirable compaction and dissolution properties. ATR-FTIR spectroscopic imaging has been used to analyze in situ the spatial distribution of different components in tablets with different compositions. Caffeine tablets made of three different polymer matrices, microcrystalline cellulose, hydroxypropyl methylcellulose (HPMC) and lactose, were investigated. It was found that the distribution of caffeine is strongly affected by the composition of polymer matrix used in the tablet. X-ray tomography was used to analyze the caffeine distribution as a complementary technique. The results obtained were compared to the ATR-FTIR spectroscopic images. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4269,4277, 2008 [source] Phase transformation of erythromycin A dihydrate during fluid bed dryingJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2008Meike Römer Abstract An in-line near infrared (NIR) spectrometer was employed to monitor phase transformations of erythromycin dihydrate during a miniaturized fluid bed drying process. The pellets, containing 50% (w/w) erythromycin dihydrate and 50% (w/w) microcrystalline cellulose, were dried at 30, 45, and 60°C. Principal component analysis was used to determine solid-state changes. For this purpose the wavelength range of 1360,2000 nm was selected and preprocessed to remove multiplicative effects. Transformation to erythromycin dehydrate was observed for the pellets dried at 45 and 60°C by NIR spectrometry and X-ray powder diffractometry (XRPD). The formation of erythromycin dehydrate was observed at a moisture content 1.4% (w/w) (mass of water per dry mass of sample) while at 1.8% (w/w) neither XRPD nor NIR were able to detect dehydration. Transformation to erythromycin dehydrate therefore depends strongly on the moisture content of the pellets. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4020,4029, 2008 [source] Quantifying effects of particulate properties on powder flow properties using a ring shear testerJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2008Hao Hou Abstract Effects of particle size, morphology, particle density, and surface silicification, on powder flow properties were investigated using a ring shear tester. Flow properties were quantified by flow function (FF), that is, unconfined yield strength, fc, as a function of major principal stress. A total of 11 powders from three series of microcrystalline cellulose (MCC): Avicel (regular MCC, elongated particles), Prosolv (silicified MCC, elongated particles), and Celphere (spherical MCC), were studied. Particle size distribution in each type of MCC was systematically different. Within each series, smaller particles always led to poorer powder flow properties. The slope of FF line was correlated to degree of powder consolidation by external stress. A key mechanism of the detrimental effect of particle size reduction on flow properties was the larger powder specific surface area. Flow properties of Celphere were significantly better than Avicel of comparable particles size, suggesting spherical morphology promoted better powder flow properties. Flow properties of powders different in densities but similar in particle size, shape, and surface properties were similar. When corrected for density effect, higher particle density corresponded to better flow behavior. Surface silicification significantly improved flow properties of finer MCC, but did not improve those of coarser. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4030,4039, 2008 [source] Use of chitosan-alginate as alternative pelletization aid to microcrystalline cellulose in extrusion/spheronizationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2007Nattawut Charoenthai Abstract Two types of different molecular weight chitosan were investigated as a pelletization aid in extrusion/spheronization using water as granulation liquid. Spherical pellets with a maximum fraction of 60% w/w chitosan could be produced when 1.25,2.5% w/w sodium alginate was included in the formulations with no microcrystalline cellulose (MCC). Chitosan with lower molecular weight of 190 kDa showed a better pellet forming property. The pellets obtained had acceptable physical characteristics and a fast drug release. The results from Fourier transform infrared spectroscopy, differential scanning calorimetry and 13C CP-MAS nuclear magnetic resonance spectroscopy confirmed the formation of polyelectrolyte complex (PEC) between chitosan and sodium alginate, which might be a reason for successful pelletization by extrusion/spheronization. Moreover, the presence of PEC might influence the physical characteristics and dissolution behavior of chitosan-alginate pellets. The results indicated an achievement in production of pellets by extrusion/spheronization without using MCC. Moreover, chitosan combined with sodium alginate could be used as a promising alternative pelletization aid to MCC in extrusion/spheronization. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 2469,2484, 2007 [source] In situ measurement of solvent-mediated phase transformations during dissolution testingJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2006Jaakko Aaltonen Abstract In this study, solvent-mediated phase transformations of theophylline (TP) and nitrofurantoin (NF) were measured in a channel flow intrinsic dissolution test system. The test set-up comprised simultaneous measurement of drug concentration in the dissolution medium (with UV-Vis spectrophotometry) and measurement of the solid-state form of the dissolving solid (in situ with Raman spectroscopy). The solid phase transformations were also investigated off-line with scanning electron microscopy. TP anhydrate underwent a transformation to TP monohydrate, and NF anhydrate (form ,) to NF monohydrate (form II). Transformation of TP anhydrate to TP monohydrate resulted in a clear decrease in the dissolution rate, while the transformation of NF anhydrate (form ,) to NF monohydrate (form II) could not be linked as clearly to changes in the dissolution rate. The transformation of TP was an order of magnitude faster than that of NF. The presence of a water absorbing excipient, microcrystalline cellulose, was found to delay the onset of the transformation of TP anhydrate. Combining the measurement of drug concentration in the dissolution medium with the solid phase measurement offers a deeper understanding of the solvent-mediated phase transformation phenomena during dissolution. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:2730,2737, 2006 [source] A novel method for deriving true density of pharmaceutical solids including hydrates and water-containing powdersJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2004Changquan (Calvin) Sun Abstract True density is commonly measured using helium pycnometry. However, most water-containing powders, for example, hydrates, amorphous drugs and excipients, and most tablet formulations, release water when exposed to a dry helium atmosphere. Because released water brings significant errors to the measured true density and drying alters the nature of water-containing solids, the helium pycnometry is not suitable for those substances. To overcome this problem, a novel method has been developed to accurately calculate powder true density from compaction data. No drying treatment of powder samples is required. Consequently, the true density thus obtained is relevant to tableting characterization studies because no alteration to the solid is induced by drying. This method involves nonlinear regression of compaction pressure-tablet density data based on a modified Heckel equation. When true density values of water-free powders derived by this novel method were plotted against values measured using pycnometry, a regression line with slope close to unity and intercept close to zero was obtained. Thus, the validity of this method was supported. Using this new method, it was further demonstrated that helium pycnometry always overestimates true densities of water containing powders, for example, hydrates, microcrystalline cellulose (MCC), and tablet formulations. The calculated true densities of powders were the same for different particle shapes and sizes of each material. This further suggests that true density values calculated using this novel method are characteristic of given materials and independent of particulate properties. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:646,653, 2004 [source] The characterization of fluidization behavior using a novel multichamber microscale fluid bedJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2004Eetu Räsänen Abstract In the preformulation stage, there is a special need to determine the process behavior of materials with smaller amounts of samples. The purpose of this study was to assemble a novel automated multichamber microscale fluid bed module with a process air control unit for the characterization of fluidization behavior in variable conditions. The results were evaluated on the basis of two common computational methods, the minimum fluidization velocity, and the Geldart classification. The materials studied were different particle sizes of glass beads, microcrystalline cellulose, and silicified microcrystalline cellulose. During processing, the different characteristic fluidization phases (e.g., plugging, bubbling, slugging, and turbulent fluidization) of the materials were observed by the pressure difference over the bed. When the moisture content of the process air was increased, the amount of free charge carriers increased and the fine glass beads fluidized on the limited range of velocity. The silicification was demonstrated to improve the fluidization behavior with two different particle sizes of cellulose powders. Due to the interparticle (e.g., electrostatic) forces of the fine solids, the utilization of the computational predictions was restricted. The presented setup is a novel approach for studying process behavior with only a few grams of materials. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93: 780,791, 2004 [source] Factorial designed experiment to study the effects of excipients on the mechanical properties of pelletsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2006Abraham B. Bashaiwoldu The aim of this work was to determine the effects of formulation factors on the mechanical properties of pellets produced by the process of extrusion and spheronisation. A range of properties from a simple fracture load to detailed load/displacement curves were used to study the effects of the levels of lactose monohydrate and glyceryl monostearate on the mechanical properties of pellets in terms of their surface tensile strength, pellet deformability and linear strain. A series of independent 22 -factorial designs were employed to establish the relationships between composition of the formulations and pellet properties, whereby the concept of an excess variable was explored. It was found that the spheronisation aid used, microcrystalline cellulose, is the domineering factor in most mechanical properties studied, except for the surface tensile strength, which decreased significantly with an increase in glyceryl monostearate concentration. The change in binder liquid from water to a water/ethanol mixture further changed the behaviour of the systems significantly. The assumption of an excess variable being less critical for the statistical outcome of a factorial experiment has not been found feasible for the systems studied. [source] The change in characteristics of microcrystalline cellulose during wet granulation using a high-shear mixerJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2001Tatsuya Suzuki The objective of this study was to investigate the mechanism of hard granule formation and to demonstrate the applicability of X-ray diffraction methods for studying the polymeric pharmaceutical excipients. Using a high-shear mixer, microcrystalline cellulose (MCC) was granulated with water as the granulating liquid. The hardness of the MCC granules increased with granulation time and the amount of water added. The specific surface area measured by the N2 adsorption method was reduced during the process. Crystallite size of cellulose, calculated by Scherrer's equation adapted for wide angle X-ray diffraction method, decreased with granulation time and with increasing amounts of water added. Debye plots for X-ray small scattering patterns suggested that the average magnitude of the continuous solid region in MCC granules became significantly greater, whereas the specific surface area of the MCC granules, calculated from Debye plots, became smaller in comparison with that of intact MCC. These findings suggested that the long-chain structures in MCC were disrupted, resulting in smaller units with shorter chain lengths due to the strong shear force of the impeller. These smaller units then form a network within the granules. Thus, MCC granules are strengthened with longer granulation time and greater amounts of water, resulting in a more intricate network. The change in MCC chain length and physical structure can be experimentally detected using the small-angle X-ray scattering and wide-angle powder X-ray diffraction methods. [source] Microwave-assisted derivatization of cellulose in an ionic liquid: An efficient, expedient synthesis of simple and mixed carboxylic estersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2010Shirley Possidonio Abstract Microwave (MW)-assisted cellulose dissolution in ionic liquids (ILs) has routinely led either to incomplete biopolymer solubilization, or its degradation. We show that these problems can be avoided by use of low-energy MW heating, coupled with efficient stirring. Dissolution of microcrystalline cellulose in the IL 1-allyl-3-methylimidazolium chloride has been achieved without changing its degree of polymerization; regenerated cellulose showed pronounced changes in its index of crystallinity, surface area, and morphology. MW-assisted functionalization of MCC by ethanoic, propanoic, butanoic, pentanoic, and hexanoic anhydrides has been studied. Compared with conventional heating, MW irradiation has resulted in considerable decrease in dissolution and reaction times. The value of the degree of substitution (DS) was found to be DSethanoate > DSpropanoate > DSbutanoate. The values of DSpentanoate and DShexanoate were found to be slightly higher than DSethanoate. This surprising dependence on the chain length of the acylating agent has been reported before, but not rationalized. On the basis of the rate constants and activation parameters of the hydrolysis of ethanoic, butanoic, and hexanoic anhydrides in aqueous acetonitrile (a model acyl transfer reaction), we suggest that this result may be attributed to the balance between two opposing effects, namely, steric crowding and (cooperative) hydrophobic interactions between the anhydride and the cellulosic surface, whose lipophilicity has increased, due to its partial acylation. Four ethanoate-based mixed esters were synthesized by the reaction with a mixture of the two anhydrides; the ethanoate moiety predominated in all products. The DS is reproducible and the IL is easily recycled. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 48: 134,143, 2010 [source] Efficacy and tolerability of a new formulation of sodium phosphate tablets (INKP-101), and a reduced sodium phosphate dose, in colon cleansing: a single-center open-label pilot trialALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 4 2005M. Khashab Summary Background :,The tablet form of sodium phosphate for bowel preparation for colonoscopy contains microcrystalline cellulose. This inactive ingredient produces a residue that obscures mucosal visualization and is time-consuming to remove during colonoscopy. Aim :,To perform an open-label study of efficacy and tolerability of a modified formulation with microcrystalline cellulose reduced by 50% (code named INKP-101) and a lower total dose of sodium phosphate. Methods :,Patients scheduled for colonoscopy self-administered 28 INKP-101 tablets (42 g sodium phosphate). Colon cleansing efficacy was evaluated using a standard 4-point scoring system and the amount of microcrystalline cellulose present and time spent removing it using an 8-point scale. Results :,A total of 31 patients were screened and enrolled. Thirty patients had a colonoscopy and were evaluated for colon cleansing efficacy. Overall colon cleansing was rated as excellent and good in 90% and 10% of patients respectively. About 77% of patients had microcrystalline cellulose scores of 2 or 3 (corresponding to <1 or 1,2 min spent removing microcrystalline cellulose, respectively). The drug was well-tolerated and adverse events were generally benign. Conclusion :,A new formulation of sodium phosphate with reduced microcrystalline cellulose and a lower total dose of sodium phosphate was effective for colonoscopy and well-tolerated. [source] Developmental expression and biochemical properties of a ,-1,4-endoglucanase family in the soybean cyst nematode, Heterodera glycinesMOLECULAR PLANT PATHOLOGY, Issue 2 2004Bingli Gao SUMMARY The soybean cyst nematode, Heterodera glycines, produces ,-1,4-endoglucanases (cellulases) that are secreted during infection of soybean. The gene structures of three, hg-eng-4, hg-eng-5 and hg-eng-6, of the six ,-1,4-endoglucanase genes, all family 5 glycosyl hydrolases previously identified from H. glycines, are presented here. Furthermore, we present the detailed expression analyses of ,-1,4-endoglucanase genes as well as the biochemical properties of four H. glycines endoglucanase enzymes. Two of the endoglucanases, HG-ENG-5 and HG-ENG-6, differed significantly in their amino acid sequence of the catalytic domains and their gene structure from that of the other four ,-1,4-endoglucanases. Quantitative real-time RT-PCR revealed distinct developmental expression differences among the hg-eng family members during the early stages of parasitism and relatively low expression levels in late parasitic stages, with the exception of the adult male stage for some eng genes. Recombinant HG-ENGs degraded carboxymethylcellulose and optimum enzyme activity ranged from pH 5.5 for HG-ENG-5 to pH 8 for HG-ENG-6. EDTA, Ca2+, Co2+, Mg2+ and Fe2+ did not affect enzyme activity of any ENG protein, whereas Zn2+, Cu2+ and Mn2+ inhibited enzyme activity from 23% to 73% in some cases. In tests with 12 different polysaccharide substrates, enzyme activity was restricted to ,-1,4 linkages with all ENG proteins tested. Only HG-ENG-5 and HG-ENG-6 had relatively high activity on xylan and slightly degraded microcrystalline cellulose. Together, these data reveal distinct differences in expression and biochemistry of cyst nematode parasitism genes and proteins, respectively, and cast light on the intricate interactions between a parasitic animal and its plant host. [source] Gas Classification of Particles Using a Packed BedPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2008Wei Yang Abstract Gas classification of particles using a packed bed is, for the first time, proposed and tested for two materials, i.e., glass ballotini and microcrystalline cellulose (MCC). A 2,m long column with 9.5,mm diameter is packed with 2,mm spherical particles. The particles to be classified are injected into the inlet of the packed bed by a carrier gas. Measurements of the breakthrough curves of the particles are carried out at the outlet of the packed bed. The results show that the particle elution order is particle size dependent with large particles elutriated faster than small ones. Taking the particle size into account, the retention time of irregular MCC particles is much longer than that of spherical glass beads and the difference is attributed to the particle shape and cohesiveness. Based on the findings, binary mixtures of both, glass and MCC beads are injected into the packed bed for the classification experiments. The results show different dependence on the superficial gas velocity of the particle classification efficiency. The particle classification efficiency of glass particles increases with decreasing superficial gas velocity, whereas that of MCC particles increases with increasing superficial gas velocity. [source] Energy Transfer from Chemically Attached Rhodamine 101 to Adsorbed Methylene Blue on Microcrystalline Cellulose Particles,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2007Hernán B. Rodríguez Rhodamine 101 (R101) was chemically attached onto microcrystalline cellulose and methylene blue (MB) was adsorbed to a sample bearing nearby 6 × 10,7 mol R101 (g cellulose),1. The system was studied by reflectance and emission spectroscopy in the solid state. R101 shows no aggregation in these conditions and, while pure MB builds up dimers on cellulose even at 2 × 10,8 mol g,1, in the presence of R101 no evidence on selfaggregation or heteroaggregation is found up to around 10,6 mol g,1. No exciplex formation is found as well. The overall fluorescence quantum yield measured on thick layers, once re-absorption effects are accounted for, amounts to 0.80 ± 0.07 for pure R101 and decreases steadily on increasing the concentration of MB. Results demonstrate the occurrence of radiative and nonradiative singlet energy transfer from R101 to MB. For thick layers of particles, the combined effect of both kinds of energy transfer amounts to nearly 80% at the highest acceptor concentration, while nonradiative transfer reaches 60% both for thin and optically thick layers. The dependence of nonradiative energy transfer efficiencies on the acceptor concentration is analyzed and the origin of departures from Förster behavior at low acceptor concentration is discussed. [source] Fast track to a phosphoprotein sketch , MALDI-TOF characterization of TLC-based tryptic phosphopeptide maps at femtomolar detection sensitivityPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 21 2006Vitaly Kochin Abstract Tryptic phosphopeptide mapping by TLC on microcrystalline cellulose has been a convenient method to get a fast and highly reproducible overview of the number of phosphopeptides present in any given 32P-labeled phosphoprotein. This method also provides an immediate presentation of the relative phosphorylation stoichiometry between individual phosphopeptides. However, so far, traditional tryptic phosphopeptide maps have not been useful for phosphoproteomics applications, as the S/N has been very poor, due to the large number of quenching substances and contaminants present on cellulose plates. In this study, we present a rapid and easy method for phosphopeptides identification from 2-D phosphopeptide maps (2-D-PPMs). We obtain improved sensitivity (femtomole levels) upon MALDI-TOF MS analysis of phosphopeptides extracted from 2-D-PPMs. Using this approach we could confidently characterize the major phosphorylation sites of in,vivo and in,vitro32P-labeled proteins. [source] Purification, crystallization and preliminary crystallographic analysis of the catalytic domain of the extracellular cellulase CBHI from Trichoderma harzianumACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 9 2010Francieli Colussi The filamentous fungus Trichoderma harzianum has a considerable cellulolytic activity that is mediated by a complex of enzymes which are essential for the hydrolysis of microcrystalline cellulose. These enzymes were produced by the induction of T. harzianum with microcrystalline cellulose (Avicel) under submerged fermentation in a bioreactor. The catalytic core domain (CCD) of cellobiohydrolase I (CBHI) was purified from the extracellular extracts and submitted to robotic crystallization. Diffraction-quality CBHI CCD crystals were grown and an X-ray diffraction data set was collected under cryogenic conditions using a synchrotron-radiation source. [source] A novel microplate-based screening strategy to assess the cellulolytic potential of Trichoderma strainsBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Stefano Cianchetta Abstract Bioconversion of lignocellulosic biomass to fuel requires a hydrolysis step to obtain fermentable sugars, generally accomplished by fungal enzymes. An assorted library of cellulolytic microbial strains should facilitate the development of optimal enzyme cocktails specific for locally available feedstocks. Only a limited number of strains can be simultaneously assayed in screening based on large volume cultivation methods, as in shake flasks. This study describes a miniaturization strategy aimed at allowing parallel assessment of large numbers of fungal strains. Trichoderma strains were cultivated stationary on microcrystalline cellulose using flat bottom 24-well plates containing an agarized medium. Supernatants obtained by a rapid centrifugation step of the whole culture plates were evaluated for extracellular total cellulase activity, measured as filter paper activity, using a microplate-based assay. The results obtained were consistent with those observed in shake-flask experiments and more than 300 Trichoderma strains were accordingly characterized for cellulase production. Five strains, displaying on shake-flasks at least 80% of the activity shown by the hyper-cellulolytic mutant Trichoderma Rut-C30, were correctly recognized by the screening on 24-well plates, demonstrating the feasibility of this approach. Cellulase activity distribution for the entire Trichoderma collection is also reported. One strain (T. harzianum Ba8/86) displayed the closest profile to the reference strain Rut-C30 in time course experiments. The method is scalable and addresses a major bottleneck in screening programs, allowing small-scale parallel cultivation and rapid supernatant extraction. It can also be easily integrated with high-throughput enzyme assays and could be suitable for automation. Biotechnol. Bioeng. 2010;107: 461,468. © 2010 Wiley Periodicals, Inc. [source] Cloning, expression, and characterization of novel thermostable family 7 cellobiohydrolasesBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008Sanni P. Voutilainen Abstract As part of the effort to find better cellulases for bioethanol production processes, we were looking for novel GH-7 family cellobiohydrolases, which would be particularly active on insoluble polymeric substrates and participate in the rate-limiting step in the hydrolysis of cellulose. The enzymatic properties were studied and are reported here for family 7 cellobiohydrolases from the thermophilic fungi Acremonium thermophilum, Thermoascus aurantiacus, and Chaetomium thermophilum. The Trichoderma reesei Cel7A enzyme was used as a reference in the experiments. As the native T. aurantiacus Cel7A has no carbohydrate-binding module (CBM), recombinant proteins having the CBM from either the C. thermophilum Cel7A or the T. reesei Cel7A were also constructed. All these novel acidic cellobiohydrolases were more thermostable (by 4,10°C) and more active (two- to fourfold) in hydrolysis of microcrystalline cellulose (Avicel) at 45°C than T. reesei Cel7A. The C. thermophilum Cel7A showed the highest specific activity and temperature optimum when measured on soluble substrates. The most effective enzyme for Avicel hydrolysis at 70°C, however, was the 2-module version of the T. aurantiacus Cel7A, which was also relatively weakly inhibited by cellobiose. These results are discussed from the structural point of view based on the three-dimensional homology models of these enzymes. Biotechnol. Bioeng. 2008;101: 515,528. © 2008 Wiley Periodicals, Inc. [source] Effect of Cellulase Mole Fraction and Cellulose Recalcitrance on Synergism in Cellulose Hydrolysis and BindingBIOTECHNOLOGY PROGRESS, Issue 1 2006Tina Jeoh Elucidating the molecular mechanisms that govern synergism is important for the rational engineering of cellulase mixtures. Our goal was to observe how varying the loading molar ratio of cellulases in a binary mixture and the recalcitrance of the cellulose to enzymatic degradation influenced the degree of synergistic effect (DSE) and degree of synergistic binding (DSB). The effect of cellulose recalcitrance was studied using a bacterial microcrystalline cellulose (BMCC), which was exhaustively hydrolyzed by a catalytic domain of Cel5A, an endocellulase. The remaining prehydrolyzed BMCC (PHBMCC) was used to represent a recalcitrant form of cellulose. DSE was observed to be sensitive to loading molar ratio. However, on the more recalcitrant cellulose, synergism decreased. Furthermore, the results from this study reveal that when an exocellulase (Cel6B) is mixed with either an endocellulase (Cel5A) or a processive endocellulase (Cel9A) and reacted with BMCC, synergism is observed in both hydrolysis and binding. This study also revealed that when a "classical" endocellulase (Cel5A) and a processive endocellulase (Cel9A) are mixed and reacted with BMCC, only limited synergism is observed in reducing sugar production; however, binding is clearly increased by the presence of the Cel5A. [source] Cooperative and Competitive Binding in Synergistic Mixtures of Thermobifida fuscaCellulases Cel5A, Cel6B, and Cel9ABIOTECHNOLOGY PROGRESS, Issue 4 2002Tina Jeoh Synergism between cellulases facilitates efficient hydrolysis of microcrystalline cellulose. We hypothesize that the effects of synergism, observed as enhanced extents of hydrolysis, are related to cellulase binding to the substrate in mixtures. In this study, direct measurements of bound concentrations of fluorescence-labeled T. fuscaCel5A, Cel6B, and Cel9A on bacterial microcrystalline cellulose were used to study binding behaviors of cellulases in binary component reactions. The accuracy of the determination of fluorescence-labeled cellulase concentrations in binary component mixtures was in the range of 7,9%. Data at 5 °C show that binding levels of cellulases in mixture reactions are only 22,70% of the binding levels in single component reactions. At 50 °C, however, most of the cellulase components in the same mixtures bound to extents of 40,126% higher than in the corresponding single component reactions. The degrees of synergistic effect (DSE) observed for the reactions at 50 °C were greater than 1, indicating that the components in the mixture acted synergistically, whereas DSE < 1 was generally observed for the reactions at 5 °C indicating anti-synergistic behavior. Degrees of synergistic binding (DSB) were also calculated, where anti-synergistic mixtures had DSB < 1 and synergistic mixtures had DSB>1. We conclude that the lower extents of binding at 5 °C are due to competition for binding sites by the cellulase components in the mixtures and the enhanced binding extents at 50 °C are due to increased availability of binding sites on the substrates brought about by the higher extents of hydrolysis. [source] | |||||||||||||||||||