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1.
Int J Biol Macromol ; 253(Pt 4): 127029, 2023 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-37742903

RESUMO

Effective separation of lignin macromolecules from the xylose pre-hydrolysates (XPH) during the xylose production, thus optimizing the separation and purification process of xylose, is of great significance for reducing the production costs, achieving the high value-added utilization of lignin and increasing the industrial revenue. In this study, a simple and robust method (pH adjustment) for the separation of lignin from XPH was proposed and systematically compared with the conventional acid-promoted lignin precipitation method. The results showed that the lignin removal ratio (up to 60.34 %) of this simple method was higher than that of the conventional method, and the proposed method eliminated the necessity of heating and specialized equipment, which greatly reduced the separation cost. Meanwhile, this simple method does not destroy the components in XPH (especially xylose), ensuring the yield of the target product. On the other hand, the obtained lignin was nano-scale with less condensed structures, which also possessed small molecular weights with narrow distribution, excellent antioxidant activity (8-14 times higher than commercial antioxidants) and UV protection properties. In conclusion, the proposed simple separation method could effectively separate lignin from XPH at low cost, and the obtained lignin had potential commercial applications, which would further enhance the overall profitability of industrial production.


Assuntos
Lignina , Xilose , Lignina/química , Xilose/química , Hidrólise , Bebidas Alcoólicas
2.
Guang Pu Xue Yu Guang Pu Fen Xi ; 29(8): 2148-51, 2009 Aug.
Artigo em Zh | MEDLINE | ID: mdl-19839327

RESUMO

The conformational transition of poly gamma-glutamic acid (gamma-PGA) embedded with magnetite nanoparticles under various pH conditions was investigated by Fourier transform infrared spectroscopy (FTIR). The secondary structure content was determined through the analysis of amide I bands of Fourier deconvolution spectra, secondary derivative spectra and the Gaussian curve fitting of the original infrared spectra. The results showed that the conformation of the gamma-PGA was affected by solution pH. The total contents of beta-sheet and beta-turn were higher than 65%, while alpha-helix and random coil were low. The content of beta-turn increased with increasing pH, while the beta-sheet decreased. Additionally, the zeta potential results showed that the pH-sensitive secondary structure of gamma-PGA had influence on the stability of suspension of magnetic gamma-PGA nanospheres. The minimum value of zeta potential (-35. 4 mV) was obtained at pH 10.2.


Assuntos
Nanopartículas de Magnetita , Ácido Poliglutâmico/análogos & derivados , Amidas/química , Concentração de Íons de Hidrogênio , Ácido Poliglutâmico/química , Estrutura Secundária de Proteína , Espectroscopia de Infravermelho com Transformada de Fourier
3.
J Phys Chem B ; 112(49): 15659-65, 2008 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-19367948

RESUMO

A novel method has been developed to prepare vesicles from aqueous solutions of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, by adding anionic surfactant sodium dodecyl sulfate (SDS) and inorganic salt NaF. As determined by TEM and dynamic light scattering (DLS) measurements, the average diameter of vesicles is about 800 nm having 50 nm outer shell thickness. Identifying hydrophobic interactions between the block copolymers and the microenvironments around the vesicles using FTIR, 1H NMR, and fluorescence spectroscopy techniques revealed the vesicle formation mechanism. The spontaneously formed vesicles were further cross-linked by converting the terminal hydroxyl groups of block copolymers into aldehydes, and then chemically bridging the polymer chains by the reaction between aldehydes and diamine compounds. The cross-linked vesicles are proved much more stable than free vesicles even at higher dilutions. The obtained vesicles with good stability and biocompatibility are promising candidates for widespread applications.


Assuntos
Polietilenoglicóis/química , Propilenoglicóis/química , Reagentes de Ligações Cruzadas/química , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica de Transmissão , Temperatura
4.
J Phys Chem B ; 111(47): 13371-8, 2007 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-17958413

RESUMO

By using a combination of 1H NMR spectroscopy, two-dimensional heteronuclear single-quantum coherence-resolved (1)H{(13)C} and homonuclear rotating-frame Overhauser enhancement NMR correlation experiments with diffusion ordered spectroscopy (DOSY), the location and distribution of a hydrophobic drug, paeonol, have been established with respect to the methyl groups of the poly(ethylene oxide)-poly(propylene oxide) -poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer. The interaction between them is adjustable according to the different temperature-dependent hydrophilicities or hydrophobicities of the triblock copolymer components. On the other hand, such interactions influence the self-assembly properties of the block copolymer amphiphiles in solution. The amount of anhydrous methyl groups of PPO segments shows an increase with increasing paeonol concentration. It was also demonstrated that the shell-crosslinking of the Pluronic polymer has an effect in increasing the amount of anhydrous methyl groups and thus increasing the hydrophobicity of Pluronic micelles. This might be the deeper reason underlying the increase in drug-loading capacity and prolongation in release time of Pluronic micelles for drug delivery after the shell-crosslinking. Changes in self-diffusion coefficients of paeonol with varying copolymer concentrations and types were also determined by the diffusion-based NMR DOSY technique, and values of K(a), DeltaG, and n were calculated.


Assuntos
Acetofenonas/química , Espectroscopia de Ressonância Magnética , Polietilenoglicóis/química , Propilenoglicóis/química , Cinética , Micelas , Polímeros/química , Temperatura , Termodinâmica
5.
J Phys Chem B ; 111(38): 11140-8, 2007 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-17764167

RESUMO

The oil-induced aggregation behavior of PEO-PPO-PEO Pluronic P84 [(EO)19(PO)39(EO)19] in aqueous solutions has been systematically investigated by 1H NMR spectroscopy, freeze-fracture transmission electron microscopy (FF-TEM), and dynamic light scattering (DLS). The critical micellization temperature (CMT) for P84 in the presence of oils decreases with increasing oil concentration. The effectiveness of various oils in decreasing the CMT of block copolymer follows the order m-xylene (C(8)H(10)) > toluene (C(7)H(8)) > benzene (C(6)H(6)) > n-octane (C(8)H(18)) > n-hexane (C(6)H(14)) approximately cyclohexane (C(6)H(12)). It was found that the amount of anhydrous PO methyl groups increases whereas the amount of hydrated PO methyl groups decreases upon the addition of oils. At low oil concentration, the oil molecules are entrapped by the micellar core, but as the oil concentration increases above a certain value, the micellar core swells significantly as a result of the penetrated oil molecules, and much larger aggregates are formed. Intermolecular rotating-frame nuclear Overhauser effect (ROE) measurements between P84 and benzene were performed at 10 and 40 degrees C. The specific interaction between benzene and the methyl groups of PPO was determined, and it was observed that the interaction site remained unchanged as the temperature was increased.


Assuntos
Óleos/química , Poloxaleno/análogos & derivados , Poloxaleno/química , Polímeros/química , Água/química , Benzeno/química , Espectroscopia de Ressonância Magnética , Micelas , Microscopia Eletrônica de Transmissão , Peso Molecular , Soluções , Temperatura , Xilenos/química
6.
J Phys Chem B ; 111(19): 5155-61, 2007 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-17439172

RESUMO

Solution 1H NMR techniques were used to characterize the interaction of urea with poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers. The urea was established to interact selectively with the PEO blocks of the block copolymer, and the interaction sites were found not to change with increasing temperature. Such interactions influence the self-assembly properties of the block copolymer in solution by increasing the hydration of the block copolymers and stabilizing the gauche conformation of the PPO chain. Therefore, urea increases the critical micellization temperature (CMT) values of PEO-PPO-PEO copolymers, and the effect of urea on the CMT is more pronounced for copolymers with higher PEO contents and lower for those with increased contents of PPO segments.


Assuntos
Poloxâmero/química , Ureia/química , Espectroscopia de Ressonância Magnética , Soluções/química
7.
Guang Pu Xue Yu Guang Pu Fen Xi ; 26(9): 1598-600, 2006 Sep.
Artigo em Zh | MEDLINE | ID: mdl-17112025

RESUMO

FTIR spectroscopy was applied to investigate the interaction of anionic surfactant Sodium Dodecyl Sulfate (SDS) and Bovine Serum Albumin (BSA). Amide band I of BSA was analyzed to obtain the change in secondary structure of BSA when different concentration of SDS was added and during different interaction period. In short interaction period and at low concentration of SDS, the alpha-helixes increased and the random coil decreased. In long interaction period or at high concentration of SDS, SDS unfolded the protein by decreasing the alpha-helix structure and increasing the random coil.


Assuntos
Soroalbumina Bovina/química , Dodecilsulfato de Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Animais , Ânions , Bovinos , Concentração de Íons de Hidrogênio , Ligação Proteica , Dobramento de Proteína , Estrutura Secundária de Proteína , Soroalbumina Bovina/metabolismo , Dodecilsulfato de Sódio/metabolismo , Tensoativos/química , Tensoativos/metabolismo , Fatores de Tempo
8.
J Microbiol Biotechnol ; 26(1): 1-8, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26403818

RESUMO

The new movement towards green chemistry and renewable feedstocks makes microbial production of chemicals more competitive. Among the numerous chemicals, organic acids are more attractive targets for process development efforts in the renewable-based biorefinery industry. However, most of the production costs in microbial processes are higher than that in chemical processes, among which over 60% are generated by separation processes. Therefore, the research of separation and purification processes is important for a promising biorefinery industry. This review highlights the progress of recovery processes in the separation and purification of organic acids, including their advantages and disadvantages, current situation, and future prospects in terms of recovery yields and industrial application.


Assuntos
Ácidos/isolamento & purificação , Bactérias/metabolismo , Meios de Cultura/química , Microbiologia Industrial , Ácidos/metabolismo , Bactérias/genética , Bactérias/crescimento & desenvolvimento , Biomassa , Meios de Cultura/metabolismo , Fermentação , Microbiologia Industrial/métodos , Microbiologia Industrial/tendências
9.
Wei Sheng Wu Xue Bao ; 45(5): 733-7, 2005 Oct.
Artigo em Zh | MEDLINE | ID: mdl-16342766

RESUMO

Several bacteria, Bacillus brevis R-6, Pseudomonas delafleldii R-8, Nocardia globerula R-9, Bacillus sphaericus R-16, Rhodococcus erythropolis LSSE8-1 and Gordonia nitida LSSEJ-1, which can convert dibenzothiophene into 2-hydroxybiphenyl and sulfate, were investigated. Desulfurization products were quantitively determined by HPLC. Result revealed that each of these bacteria desulfurize DBT at a different rate. In order to obtain more information, the fragments encoding desulfurizing enzymes were studied. Desulfurization genes of R-6 and R-8 were separately amplified via PCR with specific primers based on the related sequences of Rhodococcus sp. IGTS8. Both sequences areminimally 99% related to IGTS8 sequence. Afterwards, dsz operon of LSSEJ-1 and R-9 were amplified and cloned. Sequences are also highly conservative. Data shows that identity of dszA between R-9 and IGTS8 is 99.6%, and identity of dszA between LSSEJ-1 and IGTS8 is 99.9%; dszB sequence of R-9 and LSSEJ-1 is 99.6% similarity to their counterpart sequence from IGTS8;Identity of dszC between R-9 and IGTS8 is 99.9%, and identity of dszC between LSSEJ-1 and IGTS8 is 99.1% . It may be deduced that the origins of desulfurization genes from mesophilic bacteria are the same.


Assuntos
Bactérias/metabolismo , Genes Bacterianos , Enxofre/metabolismo , Tiofenos/metabolismo , Bacillus/metabolismo , Bactérias/genética , Bactéria Gordonia/metabolismo , Reação em Cadeia da Polimerase , Pseudomonas/metabolismo , Rhodococcus/metabolismo
10.
Chem Biol Interact ; 240: 134-44, 2015 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-26282491

RESUMO

Ganoderic acids (GAs) produced by Ganoderma lucidum possess anticancer activities with the generation of reactive oxygen species (ROS). However, the role of oxidative stress in apoptotic process induced by GAs is still undefined. In this study, the effects of four structurally related GAs, i.e. GA-T, GA-Mk, and two deacetylated derivatives of GA-T (GA-T1 and GA-T2) on the antioxidant defense system and induced apoptosis in cervical cancer cells HeLa were investigated in vitro. Our results indicated that the tested GAs (5-40 µM) induced apoptotic cell death through mitochondrial membrane potential decrease and activation of caspase-9 and caspase-3. Furthermore, GAs increased the generation of intracellular ROS and attenuated antioxidant defense system by decreasing glutathione (GSH) level, superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities. The above effects were remarkably blocked by the exogenous antioxidants, i.e. N-acetylcysteine, catalase and diphenyleneiodonium chloride. The potency of the four GAs toward induced apoptosis, generation of ROS and suppression of antioxidant defense system was in the order of: GA-T > GA-Mk ≈ GA-T1 > GA-T2 in HeLa cells. These findings suggest that GAs induced mitochondria-dependent cell apoptosis in HeLa cells are mediated via enhancing oxidative stress and depressing antioxidant defense. Additionally, the acetylation of hydroxyl groups in GAs may contribute to their pro-oxidant activities and cytotoxicity, which is helpful to the development of novel chemotherapy agents.


Assuntos
Apoptose/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Triterpenos/farmacologia , Antioxidantes/química , Antioxidantes/metabolismo , Feminino , Células HeLa , Humanos , Estrutura Molecular , Espécies Reativas de Oxigênio , Triterpenos/química , Triterpenos/classificação , Neoplasias do Colo do Útero/tratamento farmacológico
11.
J Colloid Interface Sci ; 251(2): 417-23, 2002 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-16290748

RESUMO

Fourier transform infrared (FTIR) spectroscopy was used to study the conformational changes of the polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) block copolymer, Pluronic P104, in a large concentration range in a polymer-water system as a function of temperature. The melt in which the conformational transition of the PEO blocks occurs gives remarkable changes in the spectral behavior. A small amount of water in Pluronic P104 can induce the PEO block amorphism. The addition of more water only swells the PEO dominant region and gives no significant difference in the conformational structure of the block copolymer in the ordered phases of Pluronic P104-water mixtures. The PPO blocks of Pluronic P104 are hydrated only in a condition of lower temperature and higher water content. The temperature dependent micellization of Pluronic P104 in water was analyzed by a FTIR spectroscopic method. The appearance of the symmetric deformation band of the anhydrous methyl groups at temperature below the CMT indicates the existence of a hydrophobic microenvironment. The appearance of the symmetric deformation band of the hydrated methyl groups at higher temperatures indicates that the micellar core must contain some amount of water. The results of FTIR data show that the proportion of the anhydrous methyl groups increases and water content in the micellar core decreases during the micellization process.


Assuntos
Micelas , Polietilenoglicóis/química , Propilenoglicóis/química , Espectroscopia de Infravermelho com Transformada de Fourier
12.
J Colloid Interface Sci ; 264(2): 526-31, 2003 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-16256674

RESUMO

The effect of sodium chloride (NaCl) upon the thermally induced association behavior of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer, Pluronic P103, has been investigated using pyrene fluorescence spectroscopy. The critical micellization temperature (CMT) of Pluronic P103 in aqueous solution is decreased by the addition of NaCl. The standard enthalpy and entropy of micellization for Pluronic P103 in water are increased in the presence of small amounts of NaCl, but further addition of NaCl decreases the standard enthalpy and entropy of micellization. The I1/I3 ratio of pyrene in aqueous Pluronic P103 solutions at temperature below the CMT decreases with increases of NaCl concentration, which is related to the decrease of PPO solubility. The decrease in polarity of the PPO shifts the CMT toward lower temperature.

13.
Bioresour Technol ; 100(21): 5092-6, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19541480

RESUMO

In situ cell separation and immobilization of bacterial cells for biodesulfurization were developed by using superparamagnetic Fe(3)O(4) nanoparticles (NPs). The Fe(3)O(4) NPs were synthesized by coprecipitation followed by modification with ammonium oleate. The surface-modified NPs were monodispersed and the particle size was about 13 nm with 50.8 emu/g saturation magnetization. After adding the magnetic fluids to the culture broth, Rhodococcus erythropolis LSSE8-1 cells were immobilized by adsorption and then separated with an externally magnetic field. The maximum amount of cell mass adsorbed was about 530 g dry cell weight/g particles to LSSE8-1 cells. Analysis showed that the nanoparticles were strongly absorbed to the surface and coated the cells. Compared to free cells, the coated cells not only had the same desulfurizing activity but could also be easily separated from fermentation broth by magnetic force. Based on the adsorption isotherms and Zeta potential analysis, it was believed that oleate-modified Fe(3)O(4) NPs adsorbed bacterial cells mainly because of the nano-size effect and hydrophobic interaction.


Assuntos
Bactérias/citologia , Bactérias/isolamento & purificação , Magnetismo/métodos , Enxofre/isolamento & purificação , Tiofenos/isolamento & purificação , Adsorção , Biodegradação Ambiental , Células Imobilizadas , Óxido Ferroso-Férrico/metabolismo , Nanopartículas Metálicas
14.
Langmuir ; 23(19): 9596-605, 2007 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-17655339

RESUMO

The effects of temperature, polymer composition, and concentration on the micellization and gelation properties of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers in aqueous solutions were investigated by 1H NMR spectroscopy. It was found that the temperature-dependent behavior of PPO blocks, observed as changes in chemical shift, half-height width, and integral value, could be attributed as an intrinsic tool to characterize the transition states during unimer to micelle formation. The 1H NMR spectral analysis revealed that the hydrophobic part, PPO, of the Pluronic polymers plays a more significant role in the temperature-induced micellization, whereas the transitional behavior of Pluronic polymer, i.e., from micellization to liquid crystals formation, resulted in the drastic broadening of the spectral signals for the PEO, indicating that the PEO segments play a more significant role in the crystallization process. It was also observed that the temperature-dependent changes in the half-height width of the PEO -CH2- signal are sensitive to the liquid crystalline phase formation, which could be attributed to the close packing of spherical micelles at high polymer concentrations or temperatures.


Assuntos
Micelas , Polietilenoglicóis/química , Propilenoglicóis/química , Água/química , Géis/química , Espectroscopia de Ressonância Magnética , Prótons , Soluções/química , Temperatura
15.
Langmuir ; 23(25): 12669-76, 2007 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-17988160

RESUMO

In this study, temperature-responsive magnetite/polymer nanoparticles were developed from iron oxide nanoparticles and poly(ethyleneimine)-modified poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymer. The particles were characterized by TEM, XRD, DLS, VSM, FTIR, and TGA. A typical product has an approximately 20 nm magnetite core and an approximately 40 nm hydrodynamic diameter with a narrow size distribution and is superparamagnetic with large saturation magnetization (51.34 emu/g) at room temperature. The most attractive feature of the nanoparticles is their temperature-responsive volume-transition property. DLS results indicated that their average hydrodynamic diameter underwent a sharp decrease from 45 to 25 nm while evaluating the temperature from 20 to 35 degrees C. The temperature-dependent evolution of the C-O stretching band in the FTIR spectra of the aqueous nanoparticles solution revealed that thermo-induced self-assembly of the immobilized block copolymers occurred on the magnetite solid surfaces, which is accompanied by a conformational change from a fully extended state to a highly coiled state of the copolymer. Consequently, the copolymer shell could act as a temperature-controlled "gate" for the transit of guest substance. The uptake and release of both hydrophobic and hydrophilic model drugs were well controlled by switching the transient opening and closing of the polymer shell at different temperatures. A sustained release of about 3 days was achieved in simulated human body conditions. In primary mouse experiments, drug-entrapped magnetic nanoparticles showed good biocompatibility and effective therapy for spinal cord damage. Such intelligent magnetic nanoparticles are attractive candidates for widespread biomedical applications, particularly in controlled drug-targeting delivery.


Assuntos
Sistemas de Liberação de Medicamentos , Compostos Férricos/química , Nanopartículas/química , Polietilenoglicóis/química , Propilenoglicóis/química , Temperatura , Animais , Modelos Animais de Doenças , Amarelo de Eosina-(YS)/química , Amarelo de Eosina-(YS)/farmacocinética , Feminino , Compostos Férricos/síntese química , Ibuprofeno/química , Ibuprofeno/farmacocinética , Magnetismo , Modelos Moleculares , Conformação Molecular , Tamanho da Partícula , Ratos , Ratos Sprague-Dawley , Propriedades de Superfície , Distribuição Tecidual
16.
Langmuir ; 23(6): 3075-83, 2007 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-17269812

RESUMO

An aqueous micellar solution of a PEO-PPO-PEO triblock copolymer, pluronic F88 (EO103PO39EO103), in the presence of salt (KCl) has been investigated by 1H NMR spectroscopy. The hydrogen-bonding structure in water is directly changed by the strong polarization effect of added salt, which indirectly weakens the interaction of polymer molecules with water. Both EO and PO blocks are dehydrated by the addition of salt in a similar way, whereas the solubility of the PO blocks may be affected in a more pronounced way, which results in the decrease of the critical micellization temperature (CMT). It is found that the addition of salt favors a more compact micellar core, where the water content is decreased and an effective PO-PO interaction is increased. Increasing the salt concentration would result in a decrease in the number of gauche conformers in the PPO chain, which may be the deeper reason for the decreasing solubility of PPO segments in aqueous salt solution. The temperature region over which the micellization occurs is broad, indicating that micelles and unimers coexist over an extended temperature range, whereas this transition region is significantly narrowed by the addition of salt. The addition of salt offers a good substitute way of changing the temperature to induce micellization. The critical micellization salt concentration (CMSC) is determined to be 1.0 mol l-1 for KCl in 2.5% aqueous pluronic F88 solution at 25 degrees C, and the transition region in which both free and associated copolymer molecules coexist is defined to range from 1 to 2 mol L-1.


Assuntos
Espectroscopia de Ressonância Magnética/métodos , Polímeros/química , Sais/farmacologia , Físico-Química/métodos , Óxido de Deutério , Ligação de Hidrogênio , Micelas , Conformação Molecular , Cloreto de Potássio/química , Prótons , Solubilidade , Temperatura , Fatores de Tempo , Água/química
17.
Bioprocess Biosyst Eng ; 28(4): 267-73, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16341554

RESUMO

Nattokinase is a novel fibrinolytic enzyme that is considered to be a promising agent for thrombosis therapy. In this study, reverse micelles extraction was applied to purify and concentrate nattokinase from fermentation broth. The effects of temperature and phase volume ratio used for the forward and backward extraction on the extraction process were examined. The optimal temperature for forward and backward extraction were 25 degrees C and 35 degrees C respectively. Nattokinase became more thermosensitive during reverse micelles extraction. And it could be enriched in the stripping phase eight times during backward extraction. It was found that nattokinase could be purified by AOT reverse micelles with up to 80% activity recovery and with a purification factor of 3.9.


Assuntos
Bacillus/metabolismo , Fracionamento Químico/métodos , Coloides/química , Coloides/isolamento & purificação , Subtilisinas/isolamento & purificação , Ultrafiltração/métodos , Micelas , Soluções , Temperatura
18.
Langmuir ; 22(23): 9704-11, 2006 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-17073500

RESUMO

In this paper we present the effect of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer micelles and their hydrophobicity on the stabilization of gold nanoparticles. Gold nanoparticles were prepared by a method developed by Sakai et al. (Sakai, T.; Alexandridis, P. Langmuir 2004, 20, 8426). An absorption centered at 300-400 nm in time-dependent UV spectra provided evidence that the very first step of the synthesis was to form primary gold clusters. Then the gold clusters grew in size and were stabilized by block copolymer micelles. The stabilization capacities of the micelles were modulated by tuning the block copolymer concentration and composition and by adding salts. With good stabilization, gold particles were spherical and uniform in size with a diameter of 5-10 nm. Otherwise they were aggregates with irregular shapes such as triangular, hexagonal, and rodlike. The presence of a small amount of NaF significantly increased the stabilization capacity of the micelles and consequently modified the quality of the gold particles. Using FTIR and 1H NMR spectroscopy, micellization of the block copolymers and hydrophobicity of the micelles were proven very important for the stabilization. A higher hydrophobicity of the micelle cores was expected to favor the entrapment of primary gold clusters and the stabilization of gold nanoparticles.


Assuntos
Ouro/química , Interações Hidrofóbicas e Hidrofílicas , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Micelas , Polietilenoglicóis/química , Propilenoglicóis/química , Coloides , Cor , Microscopia Eletrônica de Transmissão , Soluções , Espectrofotometria , Temperatura
19.
Biotechnol Lett ; 25(23): 1977-81, 2003 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-14719809

RESUMO

Pseudomonas delafieldii was immobilized in magnetic polyvinyl alcohol (PVA) beads using a hydrophilic magnetic fluid, which was prepared by a co-precipitation method. The beads had distinct super-paramagnetic properties and were compared with immobilized cells in non-magnetic PVA beads. Their desulfurizing activity was increased slightly from 8.7 to 9 mmol sulfur kg(-1) (dry cell) h(-1). The main advantages was that the magnetic immobilized cells maintain a high desulfurization activity and remain in good shape after 7 times of repeated use, while the non-magnetic immobilized cells could only be used for 5 times. Furthermore, the magnetic immobilized cells could be easily collected or separated magnetically from the biodesulfurization reactor.


Assuntos
Aderência Bacteriana/fisiologia , Biofilmes/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Técnicas de Cultura de Células/métodos , Magnetismo , Álcool de Polivinil , Pseudomonas/fisiologia , Enxofre/metabolismo , Biodegradação Ambiental , Células Imobilizadas/fisiologia , Materiais Revestidos Biocompatíveis/síntese química , Microesferas , Pseudomonas/isolamento & purificação
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