Dai-Di Fan

Northwest University, Florida, United States

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Publications (15)24.79 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: From the self-assembly of the typical Salen-type Schiff-base ligand H 2 L and Zn(OAc)2·2H2O in the molar ratio of 1:1 or 1:2, the mononuclear [Zn(L)(H2O)] (1) or binuclear [Zn2(L)(OAc)2(H2O)] (2) are obtained, respectively. For both complexes 1 and 2, the unsaturated five-coordinate coordination environment to the catalytic active centers (Zn2+ ions) permits the monomer insertion for the effective solution copolymerization of cyclohexene oxide and maleic anhydride. All the solution copolymerizations afford poly(ester-co-ether)s, while lower catalyst and co-catalyst concentrations are helpful for the formation of alternating polyester. Of the three co-catalysts, 4-(dimethylamino)pyridine is found to be the most efficient, while an excess thereof is detrimental for chain growth of the copolymers.
    Chinese Journal of Polymer Science 06/2014; 32(6). · 1.27 Impact Factor
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    ABSTRACT: Based on the half-unit Schiff-base ligand precursor HL1 and the asymmetrical bis-Schiff-base ligand precursor H2L2 synthesized from the reaction of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP), o-phenylenediamine and/or o-vanillin, three complexes containing low toxicity Zn2+ ions, mononuclear [Zn(L1)2] (1), [Zn(L2)(H2O)] (2) and trinuclear [Zn3(L2)2(OAc)2] (3), are obtained, respectively. Complex 1 proves to be inactive, resulting from its saturated octahedral coordination environment around the central Zn2+ ion, while in complex 2 or 3, the unsaturated five and/or four-coordinate coordination environment for the catalytic active centers (Zn2+ ions) permits the monomer insertion for the effective bulk or solution copolymerization of CHO (cyclohexene oxide) and MA (maleic anhydride). All the bulk copolymerizations afford poly(ester-co-ether)s, while some of the solution copolymerizations produce perfectly alternating polyester copolymers. Moreover, higher polymerization temperature, lower catalyst and co-catalyst concentration and shorter reaction time are helpful for the formation of alternating copolymers in bulk or solution copolymerization. Of the three co-catalysts, DMAP (4-(dimethylamino)pyridine) is found to be the most efficient, while an excess thereof is detrimental for chain growth of the copolymers.
    Journal of Molecular Catalysis A Chemical 02/2014; 382:136–145. · 3.19 Impact Factor
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    ABSTRACT: In order to greatly improve vitality of probiotic bacteria within the application, a novel biocompatible vehicle, N,O-carboxymethyl chitosan (NOCs) with appropriate degrees of substitution coat alginate (ALg) microparticles, was prepared by electrostatic droplet generation. The amount of chitosan (Cs) and N,O-carboxymethyl chitosan (NOCs) coated on the ALg microparticles was determined by differential scanning calorimetry. The surface morphology of ALg microparticles, Cs coated ALg microparticles and NOCs coated ALg microparticles was determined using scanning electron microscopy. The coating thickness of Cs coated ALg microparticles and that of NOCs coated ALg microparticles was directly observed with confocal laser scanning microscopy. In order to assess pH sensitivity of microparticles, the bovine serum albumin release from the microspheres was tested in acid solution (pH2.0) for 2h and subsequently in alkaline solution (pH7.0) for 2h. The survival of Bifidobacterium longum BIOMA 5920 loaded in NOCs coated with ALg microparticle was improved in simulated gastric juice (pH2.0, for 2h) compared to that of B. longum BIOMA 5920 loaded in ALg microparticles and Cs coated ALg microparticles. After incubation in simulated intestinal juices (pH7.0, 2h), the release of microencapsulated B. longum BIOMA 5920 was investigated.
    Materials science & engineering. C, Materials for biological applications. 07/2013; 33(5):3047-53.
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    ABSTRACT: To increase the target protein production and reduce acetic acid accumulation during fed-batch cultivation of recombinant Escherichia coli BL21 in a 30-L bioreactor, 12 different models of pulse feeding were performed to evaluate the effect of pulse feeding at different cultivation phases and pulse frequency on cell growth, acetic acid accumulation, and human-like collagen (HLC) synthesis. The results showed that the acetate concentration was kept at a low level (below 0.5 g/L) in all cases when pulse feeding was introduced before induction, whereas the pulse frequency affected cytoactivity significantly through cell growth rate, oxygen uptake rate, carbon dioxide evolution rate, and the synthesis of the target protein. The final biomass and HLC reached 75.46 and 7.26 g/L, respectively, in the model of 8-Sec feedings per 188 Sec. After induction, the pulse frequency had a great effect on HLC synthesis after high-temperature induction; low frequency was adverse to microorganisms. The model of 3-Sec feeding per 27 Sec was best and resulted in the highest biomass and HLC production. Compared to the pseudo-exponential feeding, pulse feeding reduced acetic acid accumulation effectively.
    Biotechnology and Applied Biochemistry 09/2012; 59(5):330-7. · 1.35 Impact Factor
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    ABSTRACT: Alginate (ALg)-human-like collagen (HLC) microspheres were prepared by the technology of electrostatic droplet generation in order to develop a biocompatible vehicle for probiotic bacteria. Microparticles were spherical with mean particle size of 400μm. The encapsulation efficiency (EE) of ALg-HLC microspheres could reach 92-99.2%. Water-soluble and fibrous human-like collagen is combined with sodium alginate through intermolecular hydrogen bonding and electrostatic force which were investigated by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), thus the matrix of ALg-HLC was very stable. Bifidobacterium longum BIOMA 5920, as a kind of probiotic bacteria, was encapsulated with alginate-human-like collagen to survive and function in simulated gastrointestinal juice. Microparticles were very easy to degradation in simulated intestinal juices. After incubation in simulated gastric (pH 2.0, 2h), the encapsulated B. longum BIOMA 5920 numbers were 4.81 ± 0.38 log cfu/g.
    International journal of biological macromolecules 08/2011; 49(5):979-84. · 2.37 Impact Factor
  • Yuan-Yuan Yu, Dai-Di Fan
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    ABSTRACT: In the present investigation, the complex of recombinant human-like collagen (r-HLC) with zinc (II) has been synthesized in aqueous solution and was analyzed by UV-vis spectroscopy, FTIR spectroscopy, circular dichroism (CD) spectroscopy, thermo gravimetric (TG) and differential scanning calorimetry (DSC) analysis. It can be concluded from UV-vis spectra that there exists interaction between r-HLC and zinc, and the complex is a new chemical compound different from pure r-HLC. In the complex of Zn, recombinant human-like collagen acts as ligand, linking the zinc ion via both groups of C=O and N-H. Besides, the results of TG and DSC confirm that the complex was significantly different from ligand, and the former is more thermally stable in comparison with the latter. The results obtained from the current investigation are of crucial importance to understand the r-HLC-Zn complex and provide theoretical evidence for the further study.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 06/2011; 81(1):412-6. · 1.98 Impact Factor
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    ABSTRACT: Production of recombinant human-like collagen (RHLC) by thermoinduction of recombinant Escherichia coli BL 21 during high cell density cultivation was investigated in a 30 L bioreactor. The effects of induction temperature (T), pH, and carbon-to-nitrogen molar ratio of the nutrient medium (C/N) were examined. The optimal thermoinduction protocol for RHLC production was determined by using a model coupling genetic algorithm and artificial neural networks. The optimal operating conditions were as follows: maintenance of induction temperature at 42°C for 3 H and then at 39.4°C until the end, induction pH at 7.03, and C/N at 4.8 (mol/mol). The theoretical maximum concentration of RHLC was 12.5 g/L, whereas the experimental value was 12.1 g/L under the optimal induction conditions.
    Biotechnology and Applied Biochemistry 05/2011; 58(3):175-84. · 1.35 Impact Factor
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    ABSTRACT: A monometallic (Ni2+, 1) and a series of bimetallic (Ni2+–Ln3+, Ln = Ce (2); Ln = Nd (3); Ln = Sm (4); Ln = Eu (5); Ln = Tb (6); Ln = Ho (7); Ln = Tm (8)) complexes based on the Salen-type Schiff-base ligand H2L (H2L = N,N′-bis(3-methoxysalicylidene)ethylene-1,2-diamine) were synthesized and characterized by EA, FT-IR, ESI-MS and X-ray crystallography. The catalysis results showed that the two kinds of complexes with different active species, could efficiently catalyze the bulk solvent-free melt ring-opening polymerization (ROP) of l-lactide with moderate molecular weights and narrow molecular weight distributions. Especially for the series of bimetallic complexes 2–8, the involvement of rare ions effectively passivated the catalytic behaviors on the ROP of l-lactide, while was in favor of the increase of polymeric molecular weights (Mw or Mn) and the polymerization controllability, and the type of rare ions was important and influential factor contributing to the catalytic behaviors.
    Journal of Molecular Catalysis A Chemical 03/2011; 337(s 1–2):25–32. · 3.19 Impact Factor
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    ABSTRACT: A monometallic (Ni2+, 1) and a series of heterometallic (Ni2+–Ln3+, Ln=Ce (2); Ln=Nd (3); Ln=Sm (4); Ln=Eu (5); Ln=Tb (6); Ln=Ho (7); Ln=Tm (8)) complexes based on the acyclic Salen-type Schiff-base ligands H2L (H2L = N,N′-bis(3-methoxysalicylidene)propane-1,2-diamine) were synthesized and characterized by FT-IR, ESI-MS and X-ray crystallography. The catalysis results showed that the two kinds of complexes with different active species, could efficiently catalyze the bulk solvent-free melt ring-opening polymerization (ROP) of l-lactide with moderate molecular weights and narrow molecular weight distributions. Especially for the series of bimetallic complexes 2–8, the involvement of rare ions slightly decreased the catalytic activities on the ROP of l-lactide, while was in favor of the increase of polymeric molecular weights (Mw or Mn) and the polymerization controllability, and the type of rare ions was important and influential factor contributing to the catalytic behaviors.
    Applied Organometallic Chemistry 02/2011; 25(4):310 - 316. · 2.01 Impact Factor
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    ABSTRACT: Interaction between human-like collagen (HLC) and endotoxin makes endotoxin removal from HLC more complicated. In this study, a simple, effective, and low-cost method was developed for endotoxin removal. A 0.4% (volume fraction) TritonX-100 solution was used to dissociate the HLC-endotoxin complexes and Q XL resin was used to remove endotoxin from the HLC solution. Product solution containing 1.2 mg · ml−1 HLC in Tris-HCl buffer (pH 7.5) and 50 mM NaCl was added to the Q XL resin; the endotoxin removal efficiency was more than 98% and HLC recovery of up to 95% could be obtained; HLC purity was also enhanced after this process. The residual TritonX-100 was removed by using a superdex-200 column. This method greatly reduced the cost of purification but provided high endotoxin removal efficiency and HLC recovery.
    Separation Science and Technology 11/2010; 45(16):2400-2405. · 1.16 Impact Factor
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    ABSTRACT: Polyhydroxyalkanoates (PHAs) as an attractive biopolymer with a wide range of applications have been extensively studied. Many new strategies have been employed to effectively and economically produce PHAs. This mini-review mainly focuses on the research and development of new PHAs-producing strains, utilization of renewable materials or industrial wastes, and high cell density culture technologies for PHAs production developed in recent years. The status of PHAs mass production is also introduced here.
    AFRICAN JOURNAL OF BIOTECHNOLOGY 04/2009; 8:709-714. · 0.57 Impact Factor
  • Xiao-Jun Wang, Dai-Di Fan, Yan-E Luo
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    ABSTRACT: The adsorption of recombinant human-like collagen by metal chelate media was investigated in a batch reactor and in a fixed-bed column. The adsorption equilibrium and kinetics had been studied by batch adsorption experiments. Equilibrium parameters and protein diffusivities were estimated by matching the models with the experimental data. Using the parameters of equilibrium and kinetics, various models, such as axial diffusion model, linear driving force model, and constant pattern model, were used to simulate the breakthrough curves on the columns. As a result, the most suitable isotherm was the Langmuir-Freundlich model, and the ionic strength had no effect on the adsorption capacity of chelate media. In addition, the pore diffusion model fitted very well to the kinetic data. The pore diffusivities decreased with increasing the initial protein concentration, however had little change with the ionic strength. The results also indicated that the models predict breakthrough curves reasonably well to the experimental data, especially at low initial protein concentration (0.3 mg ml(-1)) and low flow rate (34 cm h(-1)). By the results, we optimized the experimental conditions of a chromatographic process using immobilized metal affinity chromatography to purify recombinant human-like collagen.
    Applied biochemistry and biotechnology 10/2008; 158(2):262-76. · 1.94 Impact Factor
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    ABSTRACT: A study of the effect of drug, kanamycin, on the growth metabolism of recombinant Escherichia coli B1 was carried out by microcalorimeter monitoring of the metabolic activity of treated cells. Power-time curves of growing recombinant Escherichia coli cell suspensions, treated with different kanamycin doses, were recorded. The extent of the effect was evaluated by changes in the slopes of the microcalorimetric curves and the kinetics of the drug action was interpreted from the time at which these changes reached their maximum values and maintained their maximum values. Experimental dose-effect relationships conform to the median-effect principle of the mass-action law: fa/(1−fa)=(D/D50)m. A plot of y=lg[(fa)1−1]−1 versus x=lg D gives the slope m, D50 and R∞. The experimental results revealed that high concentration of kanamycin had an inhibitory effect on the growth of recombinant Escherichia coli B1 in the lg phase, and had a promoting effect in the stationary period. Moreover, it was demonstrated that microcalorimetry was a reliable method for the detection of modulatory effects in biology.
    Chinese Journal of Chemistry 01/2007; 25(1):20-24. · 0.92 Impact Factor
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    ABSTRACT: For investigating the relationship between thermal properties and biodegradability of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), several films of PHBV containing different polyhydroxyvalerate (HV) fractions were subjected to degradation in different conditions for up to 49 days. Differential scanning calorimetry (DSC), thermogravimetry (TG), specimen weight loss and scanning electron microscopy (SEM) were performed to characterize the thermal properties and enzymatic biodegradability of PHBV. The experimental results suggest that the degradation rates of PHBV films increase with decreasing crystallinity; the degradability of PHBV occurring from the surface is very significant under enzymatic hydrolysis; the crystallinity of PHBV decreased with the increase of HV fraction in PHBV; and no decrease in molecular weight was observed in the partially-degraded polymer.
    Journal of Polymers and the Environment 20(1). · 1.50 Impact Factor
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    ABSTRACT: With the Zn-Schiff-base [ZnL(CH3CN)] from the Salen-type Schiff-base ligand H2L (H2L = N,N′-bis(3-methoxy-salicylidene)cyclohexane-1,2-diamine) with the flexible linker as the precursor, a series of hetero-trinuclear Zn2Ln complexes [Zn2Ln(L)2(Cl)3] (Ln = Nd, 1; Ln = Yb, 2; Ln = Er, 3; Ln = Gd, 4) are obtained by the further reaction with LnCl3·6H2O, respectively. The results of their photophysical studies show that the strong and characteristic NIR luminescence with emissive lifetimes in the microsecond range, has been sensitized from the excited state (both 1LC and 3LC) of the ligand due to the effective intramolecular energy transfer.
    Inorganic Chemistry Communications 20:33–36. · 2.02 Impact Factor