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Biomedical subjects

Yan Sun

Publications and source records attributed to Yan Sun.

At least 199 records · Page 11Linked to original sources
PubMed2002

[Fluorescence probe two-hybridization technique and its application in medical genechips].

OBJECTIVE: To establish a new nucleic acid hybridization detection technique which may be used in medical genechips. METHODS: The specific DNA fragment was detected by sequential two hybridization of fluorescence probe with template DNA and fixed DNA probe. RESULTS: Fluorescence probe two-hybridization (FPTH) was applied to genechips for the detection of sex-transmitted pathogens from culture strains, and the results showed that the values of fluorescence density of the positive groups decreased remarkably when compared with those of the negative group. Both the sensitivity and specificity for detecting clinical samples are higher than 90%. There is no need of any additional reagent in hybridization procedure, and the hybridization detection can be accomplished in 40 minutes. CONCLUSION: The FPTH technique is rapid, simple and reliable, it can also make the clinical detection process completely automatic and integrative.

DNA Probes↗
PubMed2002

[Nested coamplification polymerase chain reaction].

OBJECTIVE: To develop a simple and reliable method for intensifying the hybridization signals of gene chips. METHODS: The authors added EDTA and another FAM-labeled probe to the normal PCR products, denatured the mixture by heat, and then let the mixture hybridize with the fastened probes on the chip. RESULTS: With the use of EDTA and another FAM-labeled probe, the hybridization signals increased by 6 times or greater. CONCLUSION: Adding EDTA and another probe to the normal PCR products is a simple and efficient method to intensify the hybridization signal of chips.

Base Sequence↗
PubMed2002

[Observation on treatment of ectopic pregnancy by combination therapy of Chinese herbal medicine with mifepristone or methotrexate].

OBJECTIVE: To find a simpler, effectiver with less side-effect method for treatment of ectopic pregnancy. METHODS: One hundred and fourteen patients of ectopic pregnancy were divided into two groups, the 56 patients in Group A were treated with Mifepristone and Chinese herbal medicine (CHM), and 58 patients in Group B were treated with Methotrexate and CHM. The therapeutic effect in both groups was observed and compared. RESULTS: The rate of success in Group A was 82.14% and in Group B 70.69%, comparison between them showed no significance (P > 0.05). Time for successful treatment was 14.54 +/- 5.87 days in Group A and 9.00 +/- 5.09 days in Group B, comparison of them showed significant difference (P < 0.01). Insignificance revealed in comparison between the occurrence of side-effects for the groups, such as nausea, vomiting, diarrhea, liver dysfunction and lowering of white blood cells, but significance was shown in re-menstruation time (43.43 +/- 1.77 days vs 38.38 +/- 1.13 days, P < 0.05). CONCLUSION: Treatments of combined CHM with Mifepristone or Methotrexate showed similar therapeutic effect in treating ectopic pregnancy, but the latter showed a quicker initiation and less side-effects in delaying the re-menstruation time.

Abortifacient Agents↗
PubMed2002

[Results of combined therapy for 1260 patients with small cell lung cancer].

OBJECTIVE: To evaluate the efficacy of combined modality treatment and determine the prognostic factors for small cell lung cancer (SCLC). METHODS: From January 1974 to December 1995, 1260 patients with SCLC treated were retrospectively evaluated, with limited lesions in 732 patients, extensive lesions in 500 and stage unrecorded in 28. 553 patients were alloted into chemotherapy + radiotherapy (C + R) group, 355 into C + R + C group, 97 into R + C group, 126 into C group, 64 into R group and 65 into surgery (S + C + R) group. Patients with limited lesions received 2 - 4 cycles of chemotherapy including COMC, COMP, COMVP and CE-CAP. Radiotherapy was given to a dose of 40 - 70 Gy/4 - 7 w. Radiation portals for patients with limited lesions encompassed the primary tumor, hilar lymphatic drainage areas, partial mediastinum and bilateral supraclavicular regions. Patients with extensive lesions mainly received chemotherapy with or without palliative irradiation. RESULTS: The overall CR and PR rates were 26.7% and 52.3%. Local recurrence and distant metastasis rates were 58.8% and 61.5%. The 1-, 3- and 5-year survival rates were 50.2%, 14.7% and 11.7%, with median survival time of 12 months. The era, sex, age, tumor stage and treatment modality were all significant prognostic factors by both uni-variate and multi-variate analyses (P < 0.05). The result of S + C + R rated the best among these modalities and the result of C + R + C was superior to C + R, though the difference of which was not significant. CONCLUSION: Surgical resection should be considered as one part of comprehensive therapy for small cell lung cancer patients with limited lesions whenever possible. On top of routine chemotherapy early administration of radiotherapy is advisable.

Adult↗
PubMed2001

Effect of Guanidinium Chloride Concentration on the Renaturation of Denatured Lysozyme.

The effect of guanidinium chloride (GdmCl) on the renaturation of denatured-reduced chicken egg white lysozyme was studied. It was found that the renaturation yield was significantly related to the GdmCl concentration, that is, the GdmCl concentration required to obtain a high renaturation yield increased with the increase of the denatured lysozyme concentration. When denatured lysozyme concentrations were lower than 0.21 g/L, the presence of 0.7 mol/L GdmCl resulted in the complete renaturation of lysozyme, while higher GdmCl concentration, i.e., 1.0--1.5 mol/L, was needed to yield more than 95% renaturation of 0.6--1.05 g/L of the denatured lysozyme. In addition, lysozyme renaturation rate decreased with increasing GdmCl concentration. Therefore, it is considered that optimizing GdmCl concentration is the key step to enhance the renaturation yield of denatured proteins.

Journal Article↗
PubMed1996

Characterization of the Potent Insulin Mimetic Agent Bis(maltolato)oxovanadium(IV) (BMOV) in Solution by EPR Spectroscopy.

Bis(maltolato)oxovanadium(IV) (abbreviated BMOV or VO(ma)(2)) has been characterized by electron paramagnetic resonance (EPR) spectroscopy in CH(2)Cl(2), H(2)O, MeOH, and pyridine at both room and low temperatures. Spin Hamiltonian parameters for mono- and bis(maltolato)oxovanadium(IV) complexes [VO(ma)](+) (=[VO(ma)(H(2)O)(n)()](+), n = 2 or 3) and VO(ma)(2) (Hma = 3-hydroxy-2-methyl-4-pyrone, maltol) have been obtained by computer simulation (SOPHE). Configurations of solvated vanadyl/maltol complexes, VO(ma)(2)S, in solution (S = solvent) are proposed on the basis of a comparison of their hyperfine coupling constants with those obtained for related vanadium(IV) compounds in the literature. Whereas at room temperature pyridine coordinates to VO(ma)(2) in a position cis to the oxo ligand (cis isomer), in H(2)O or in MeOH solvated and unsolvated cis and trans adducts of VO(ma)(2) are all formed, with the cis isomer dominant. As expected, the coordinating ability was found to be in the order py > H(2)O approximately MeOH > CH(2)Cl(2). In aqueous solutions at room temperature and neutral pH, cis- and trans-VO(ma)(2)(H(2)O) complexes are present as major and minor components, respectively.

Journal Article↗
PubMed1996

Oxidation Kinetics of the Potent Insulin Mimetic Agent Bis(maltolato)oxovanadium(IV) (BMOV) in Water and in Methanol.

The kinetics of oxidation of bis(maltolato)oxovanadium(IV), BMOV or VO(ma)(2), by dioxygen have been studied by UV-vis spectroscopy in both MeOH and H(2)O media. The VO(ma)(2):O(2) stoichiometry was 4:1. In aqueous solution, the pH-dependent rate of the VO(ma)(2)/O(2) reaction to generate cis-[VO(2)(ma)(2)](-) is attributed to the deprotonation of coordinated H(2)O, the deprotonated species [VO(ma)(2)(OH)](-) being more easily oxidized (k(OH) = 0.39 M(-)(1) s(-)(1), 25 degrees C) than the neutral form VO(ma)(2)(H(2)O) (k(H)()2(O) = 0.08 M(-)(1) s(-)(1), 25 degrees C). The activation parameters for the two second-order reactions in aqueous solution were deduced from variable temperature kinetic measurements. In MeOH, VO(ma)(2) was oxidized by dioxygen to cis-VO(OMe)(ma)(2), whose structure was characterized by single-crystal X-ray diffraction; the crystals were monoclinic, C2/c, with a = 28.103(1) Å, b = 7.721(2) Å, c = 13.443(2) Å, beta = 94.290(7) degrees, and Z = 8. The structure was solved by Patterson methods and was refined by full-matrix least-squares procedures to R = 0.043 for 1855 reflections with I >/= 3sigma(I). The kinetic results are consistent with a mechanism involving an attack of O(2) at the V(IV) center, followed by the formation of radicals and H(2)O(2) as transient intermediates.

Journal Article↗
PubMedDate not supplied

Cooperative effect of artificial chaperones and guanidinium chloride on lysozyme renaturation at high concentrations.

It has been recognized that the artificial chaperone system, cetyltrimethylammonium bromide and beta-cyclodextrin, is effective for enhancing protein renaturation. In this work, we studied the effect of the artificial chaperone system and guanidinium chloride (GdmCl) on the oxidative renaturation of lysozyme at 0.21-1.05 mg/mL, and a kinetic model based on the competition between protein folding and aggregation was employed to express the renaturation process. The refolding rate constant increased, while the aggregation rate constant decreased, with increasing concentration of the artificial chaperones. With increasing GdmCl concentration (0.28-2 M), both rate constants decreased, but there existed a specific GdmCl concentration that maximized the ratio of the two rate constants and thus the renaturation yield. The results obviously indicated the cooperative effect of GdmCl and the artificial chaperones on enhancing protein renaturation.

Guanidine↗
PubMedDate not supplied

Expanded bed adsorption of protein with DEAE Spherodex M.

In this article, the bed expansion behavior and the hydrodynamic and protein adsorption properties of the DEAE Spherodex M in expanded bed with mobile phases of different viscosities have been studied. The axial liquid-phase dispersion coefficient is found to be on the order of 10(-6) m(2)/s, falling into the common range from 1.0 x 10(-6) to 1.0 x 10(-5) m(2)/s observed previously in expanded bed operation. Because of the small size of the adsorbent, the high pore diffusivity of protein and the favorable column efficiency (low dispersion coefficient), the dynamic binding capacity (DBC) of bovine serum albumin (BSA) at 5% breakthrough in the expanded bed reaches over 80% that of the equilibrium adsorption density (EAD). Moreover, a theoretical model with unadjustable model parameters is used for the prediction of the breakthrough curves. Computer simulations show that the model agrees well with the experimental results at breakthrough less than about 50%. It indicates that the model is promising in the prediction of protein breakthrough behavior because breakthrough profiles at 5-50% breakthrough points are more important in practical applications.

Adsorption↗
PubMedDate not supplied

Development of rigid bidisperse porous microspheres for high-speed protein chromatography.

Development of a high-performance stationary phase is an essential demand for high-speed separation of proteins by liquid chromatography. Based on a novel porogenic mode, that is, using superfine granules of calcium carbonate as solid porogen and a mixture of cyclohexanol and dodecanol as liquid porogen, a rigid spherical biporous poly(glycidyl methacrylate-co-ethylene dimethacrylate) matrix has been prepared by radical suspension-polymerization. The epoxide groups of the matrix were modified with diethylamine to afford the ionizable weak base 1-N,N-diethylamino-2-hydeoxypropy functionalities that are required for ion exchange chromatography. Results from scanning electron microscopy and mercury intrusion porosimetry measurements revealed that the matrix contained two families of pores, that is, micropores (10-90 nm) and macropores (180-4000 nm). Furthermore, the biporous medium possesses specific surface area as high as 91.3 m(2)/g. Because of the presence of the macropores that provided convective flow channels for the mobile phase, the dynamic adsorption capacity was found to be as high as 54.6 mg/g wet bead at 300 cm/h, approximately 63.2% of its static capacity. In addition, the column efficiency and dynamic binding capacity decreased only slightly with mobile-phase flow rate in the range of 300-3000 cm/h. These properties made the packed bed with the bidisperse porous matrix suitable for high-speed protein chromatography.

Adsorption↗
PubMedDate not supplied

Application of magnetic agarose support in liquid magnetically stabilized fluidized bed for protein adsorption.

A novel magnetic agarose support (MAS) was fabricated for application in a liquid magnetically stabilized fluidized bed (MSFB). It was produced by water-in-oil emulsification method using a mixture of agarose solution and nanometer-sized superparamagnetic Fe(3)O(4) particles as the aqueous phase. The MAS showed good superparamagnetic responsiveness in a magnetic field. A reactive triazine dye, Cibacron blue 3GA (CB), was coupled to the gel to prepare a CB-modified magnetic agarose support (CB-MAS) for protein adsorption. Lysozyme was used as a model protein to test the adsorption equilibrium and kinetic behavior of the CB-MAS. The dependence of bed expansion in the MSFB with a transverse magnetic field on liquid velocity and magnetic field intensity was investigated. Liquid-phase dispersion behavior in the MSFB was examined by measurements of residence time distributions and compared with that obtained in packed and expanded beds. Dynamic lysozyme adsorption in the MSFB was also compared with those in packed and expanded beds. The dynamic binding capacity at 10% breakthrough was estimated at 55.8 mg/mL in the MSFB, higher than that in the expanded bed (31.1 mg/mL) at a liquid velocity of 45 cm/h. The results indicate that the CB-MAS is promising for use in liquid MSFB for protein adsorption.

Adsorption↗
PubMedDate not supplied

A model for the salt effect on adsorption equilibrium of basic protein to dye-ligand affinity adsorbent.

A model describing the salt effect on adsorption equilibrium of a basic protein, lysozyme, to Cibacron Blue 3GA-modified Sepharose CL-6B (CB-Sepharose) has been developed. In this model, it is assumed that the presence of salt causes a fraction of dye-ligand molecules to lodge to the surface of the agarose gel, resulting from the induced strong hydrophobic interaction between dye ligand and agarose matrix. The salt effect on the lodging of dye-ligand is expressed by the equilibrium between salt and dye-ligand. For the interactions between protein and vacant binding sites, stoichiometric equations based either on cation exchanges or on hydrophobic interactions are proposed since the CB dye can be regarded as a cation exchanger contributed by the sulfonate groups on it. Combining with the basic concept of steric mass-action theory for ion exchange, which considers both the multipoint nature and the macromolecular steric shielding of protein adsorption, an explicit isotherm for protein adsorption equilibrium on the dye-ligand adsorbent is formulated, involving salt concentration as a variable. Analysis of the model parameters has yielded better understanding of the mechanism of salt effects on adsorption of the basic protein. Moreover, the model predictions are in good agreement with the experimental data over a wide range of salt and ligand concentrations, indicating the predictive nature of the model.

Adsorption↗
PubMedDate not supplied

Solvent-free enzymatic synthesis of 1,3-diconjugated linoleoyl glycerol optimized by response surface methodology.

An operation mode with N(2) bubbling under vacuum was employed for the solvent-free synthesis of 1,3-diconjugated linoleoyl glycerol (1,3-dCLG) from conjugated linoleic acid (CLA) catalyzed by Novozym 435. The response surface methodology (RSM) was adopted for the optimization of the reaction conditions with five major factors (incubation time, temperature, enzyme load, substrate mole ratio, and system vacuum) and three responses (CLA conversion, 1,3-dCLG yield, and acyl migration). Two sets of optimal conditions were recommended. Validation of the RSM model was verified by the good agreement between the experimental and the predicted values of 1,3-dCLG yield. Under the optimal conditions, the yield of 1,3-dCLG up to 93% was obtained. The reaction was scaled up to a production level of 100 g of 1,3-dCLG at a yield of 90.7%, indicating a promising feature of the technology in industrial applications.

Algorithms↗
PubMedDate not supplied

Characteristics of immobilized lipase on hydrophobic superparamagnetic microspheres to catalyze esterification.

A novel immobilized lipase (from Candida rugosa) on hydrophobic and superparamagnetic microspheres was prepared and used as a biocatalyst to catalyze esterification reactions in diverse solvents and reaction systems. The results showed that the immobilized lipase had over 2-fold higher activities in higher log P value solvents. An exponential increase of lipase activity against log P of two miscible solvent mixtures was observed for the first time. Both free and immobilized lipase achieved its maximum activity at the range of water activity (a(w)) 0.5-0.8 or higher. At a(w) 0.6, the immobilized lipase exhibited markedly higher activities in heptane and a solvent-free system than did the native lipase. In multicompetitive reactions, the alcohol specificity of the lipase showed a strong chain-length dependency, and the immobilized enzyme exhibited more preference for a longer-chain alcohol, which is different from previous reports. The immobilized lipase showed higher specificities for butyric acid and the medium-chain-length fatty acids (C(8)-C(12)). Then, the immobilized lipase was extended to solvent-free synthesis of glycerides from glycerol and fatty acids. Recovered by magnetic separation, the immobilized lipase exhibited good reusability in repeated batch reaction, indicating its promising feature for biotechnology application.

Adsorption↗
PubMedDate not supplied

Influence of pH and ionic strength on the steric mass-action model parameters around the isoelectric point of protein.

The ion-exchange equilibrium and the dependence of the parameters in the steric mass-action (SMA) model on salt concentration and buffer pH around the isoelectric point of protein were studied. Bovine serum albumin (BSA, isoelectric point = 5.4) was used as a model protein and DEAE Sepharose FF as an ion exchanger. Finite batch adsorption experiments and isocratic elution chromatography were performed for the determination of the model parameters (i.e., characteristic charge, equilibrium constant, and steric factor). The results showed that pH had significant effects on the parameters. With an increase of pH from 4.5 to 6.5, the characteristic charge increased from 0.9 to 3.0 and leveled off as a plateau at pH above 5.5. The charge groups in the contact region of protein surface were considered to play a crucial role on the characteristic charge. The decrease of pH and increase of salt concentration lowered the absolute value of the zeta potential of the protein surface and led to a decrease of the equilibrium constant. The steric factor remained unchanged at about 31 at pH 5.5 and 6.0 and increased to 44.5 at pH 5.0 and 96.8 at pH 4.5, mainly as a result of the lower adsorption capacity of BSA at pH <5.5. Furthermore, the increase of the molecular volume of BSA at pH 4.5 would be an additional reason for the increase of the steric factor. Taking into account the effect of the pH and salt concentration on these parameters, the SMA model described the ion exchange equilibrium of protein more accurately.

Adsorption↗
PubMedDate not supplied

Modeling and simulation of fed-batch protein refolding process.

The simplified kinetic model that assumes competition between first-order folding and third-order aggregation was used to model the fed-batch refolding of denatured-reduced lysozyme. It was found that the model was able to describe the process at limited concentration ranges, i.e., 1-2 and 5-7 mg mL(-)(1), respectively, at extensive guanidinium chloride (GdmCl) concentrations and controlled concentrations of oxidizing and reducing agents. The folding or aggregation rate constant was different at the two protein concentration ranges and strongly dependent on the denaturant concentration. As a result, both rate constants at the two concentration ranges were expressed as functions of GdmCl concentration. The rate constants determined by fed-batch experiments could be employed for the prediction of the fed-batch process but were not able to be extended to a batch refolding by direct dilution. Computer simulations show that the denaturant concentration and fed-batch flow rate are important factors influencing the refolding yield. Prolonged fed-batch time is beneficial to keep the transient intermediate concentration at a low level and to increase the yield of correctly folded protein. This is of importance when the denaturant concentration in refolding buffer solution is low. Thus, at a low denaturant concentration, fed-batch time should be sufficiently long, whereas at an appropriately high GdmCl concentration, a short fed-batch time or a high feed rate of the denatured protein is effective to give a high refolding yield.

Guanidine↗
PubMedDate not supplied

Protein refolding mediated by reverse micelles of Cibacron Blue F-3GA modified nonionic surfactant.

An affinity-based reverse micellar system formulated with nonionic surfactant was applied to the refolding of denatured-reduced lysozyme. The nonionic surfactant of sorbitan trioleate (Span 85) was modified with Cibacron Blue F-3GA (CB) as an affinity surfactant (CB-Span 85) to form affinity-based reverse micelles in n-hexane. The water content of 15 was found optimal for lysozyme refolding in the reverse micellar system of 62.7 mmol/L Span 85 with coupled CB of 0.3 and 0.5 mmol/L. In addition, the operating conditions such as pH and the concentrations of urea and redox reagents were optimized. Under the optimized conditions, complete renaturation of lysozyme at 3-3.5 mg/mL was achieved, whereas dilution refolding in the bulk aqueous phase under the same conditions gave much lower activity recovery. Moreover, the secondary structure of the refolded lysozyme was found to be the same as the native lysozyme. Over 95% of the refolded lysozyme was recovered from CB-Span 85 reverse micelles by a stripping solution of 0.5 mol/L MgCl(2). Thus, the present system is advantageous over the conventional reverse micellar system formed with ionic surfactants in the ease of protein recovery.

Animals↗