Biomedical subjects

Lan Ding

Publications and source records attributed to Lan Ding.

At least 19 recordsLinked to original sources

PubMed2026

A MIL-88@Ru-based molecularly imprinted electrochemiluminescence sensor for highly selective and sensitive detection of enrofloxacin residues in animal-derived foods.

Using a metal-organic framework (MOF) - supported Ru(bpy)32+ (MIL-88@Ru) composite luminescent material, this study innovatively adopted electropolymerization to fabricate a molecularly imprinted polymer-based electrochemiluminescent (MIP-ECL) sensor for enrofloxacin (ENR) detection in animal-derived foods. Systematic investigation of the ECL luminescence and ENR's quenching mechanism confirmed that the sensor integrates ECL's high sensitivity and MIP's high specificity, enabling rapid and accurate recognition of ENR. Experimental results show a good linear response in the range of 1 nmol/L-20 μmol/L (R2 = 0.99), a limit of detection (LOD) as low as 0.28 nmol/L, as well as excellent selectivity and stability. Recoveries of ENR in all investigated matrices ranged from 97.7% to 106.4%, confirming the reliability of the established method. This ECL-MIP coupling strategy provides a new technical approach and application references for the efficient detection of trace pollutants in food safety and environmental monitoring fields.

Enrofloxacin↗

PubMed2006

On-line coupling of dynamic microwave-assisted extraction with high-performance liquid chromatography for determination of andrographolide and dehydroandrographolide in Andrographis paniculata Nees.

A novel technique based on dynamic microwave-assisted extraction (DMAE) coupled on-line with high-performance liquid chromatography (HPLC) through a flow injection interface has been developed for determination of andrographolide and dehydroandrographolide in Andrographis paniculata Nees. A TM(010) microwave resonance cavity built in the laboratory was applied to concentrating the microwave energy. An extraction vessel was placed in microwave irradiation zone. The extraction was performed in a recirculating system. When a number of extraction cycles were completed, the fractional extract (20muL) was driven to the analytical column by 65% aqueous methanol and was measured by diode array detector (DAD) at 225nm. The optimized extraction conditions are follows: extraction solvent 60% aqueous methanol; microwave forward power 80W; extraction time 6min; extraction solvent flow-rate 1.0mLmin(-1). The detection and quantification limits obtained are 0.5 and 1.7microgmL(-1) for andrographolide and 0.6 and 1.9microgmL(-1) for dehydroandrographolide, respectively. The within-day and between-day precision (RSD) are 2.1% and 3.7% for andrographolide and 1.7% and 4.1% for dehydroandrographolide, respectively. Mean recoveries for andrographolide and dehydroandrographolide are 97.7% and 98.7%, respectively. Compared with ultrasonic extraction used in the Chinese pharmacopoeia, the proposed method was demonstrated to obtain higher extraction yield in a shorter time. In addition, only small quantities of solvent (5mL) and sample (10mg) were required.

Andrographis↗

PubMed2006

Rapid analysis of the essential oils from dried Illicium verum Hook. f. and Zingiber officinale Rosc. by improved solvent-free microwave extraction with three types of microwave-absorption medium.

A new method of extracting essential oils from dried plant materials has been studied. By adding a microwave-absorption medium (MAM) to a reactor, solvent-free microwave extraction (SFME) was improved and can be used to extract essential oils from dried plant material without pretreatment. With a microwave irradiation power of 85 W it took only approximately 30 min to extract the essential oils completely. The whole extraction process is simple, rapid, and economical. Three types of MAM, iron carbonyl powder (ICP), graphite powder (GP), and activated carbon powder (ACP), and two types of dried plant material, Illicium verum Hook. f. and Zingiber officinale Rosc., were studied. The results were compared with those obtained by use of conventional SFME, microwave-assisted hydrodistillation (MAHD), and conventional hydrodistillation (HD), and the conclusion drawn was that improved SFME was a feasible means of extracting essential oils from dried plant materials, because there were few differences between the composition of the essential oils extracted by improved SFME and by the other methods.

Adsorption↗

PubMed2006

Mammalian alkaline phosphatase catalysis requires active site structure stabilization via the N-terminal amino acid microenvironment.

In mammalian alkaline phosphatase (AP) dimers, the N-terminus of one monomer embraces the other, stretching toward its active site. We have analyzed the role of the N-terminus and its microenvironment in determining the enzyme stability and catalysis using human placental (PLAP) and tissue-nonspecific AP (TNAP) as paradigms. Deletion of nine amino acid (aa) residues in PLAP reduced its AP activity and heat stability, while deletion of 25 aa resulted in an inactive enzyme. In turn, deletion of five and nine N-terminal aa in TNAP reduced and abolished AP activity, respectively. The N-terminal aa deletions in both isozymes affected the rate of substrate catalysis (k(cat)), with an only minor effect on the Michaelis constant (K(m)) explained by decelerated intramolecular transition rates in the active site. Arg370 in PLAP, and the corresponding Arg374 in TNAP, critically control the structure and function of the enzymes, but the Glu6-Arg370 bond predicted by the PLAP crystal structure appeared to be irrelevant with respect to PLAP stability or catalysis. Structural disruption was also noted in [R374A]TNAP, [Delta5]TNAP, [Delta9]TNAP, and [Delta25]TNAP using a panel of 19 anti-TNAP antibodies illustrating the structural role of the N-terminus. Our data reveal that the N-terminal alpha-helical folding is more crucial for the structural stability of the second monomer in TNAP than in PLAP. The correct folding of the N-terminus and of interacting loops in its immediate environment is essential for overall structural integrity and for execution of intramolecular transitions during enzyme catalysis. These findings provide a mechanistic interpretation for loss-of-function mutations of N-terminal TNAP residues in cases of hypophosphatasia.

Alkaline Phosphatase↗

PubMed2006

Development of an analytical method for organotin compounds in fortified flour samples using microwave-assisted extraction and normal-phase HPLC with UV detection.

The normal high-performance liquid chromatography with UV detection was applied for the determination of tributyltin chloride (TBT), triphenyltin chloride (TPhT), tetraphenyltin (TrPhT), triethyltin chloride (TET) and tetraethyltin (TrET) from flour samples. The separation was performed in the isocratic mode on cyanopropyl column with a mobile phase of hexane-acetonitrile-THF (97/1/2). Under the experimental conditions used, quantitative limit of TBT, TPhT, TrPhT, TET and TrET are 0.95, 0.46, 0.97, 0.75 and 0.96 microg/ml, respectively. Microwave-assisted extraction of organotin (OT) compounds at 100 degrees C with an extraction time of 3 min was described. The extraction of organotin can be finished in acetic acid-hexane (20/80) medium. The quantitative extraction of five organotin compounds was achieved with recoveries ranging from 88 to 101% R.S.D. 3-8%.

Analytic Sample Preparation Methods↗

PubMed2006

Investigation on the interaction between colloidal gold and human complement factor 4 at different pH by spectral methods.

The interaction between colloidal gold and human complement factor 4 (human C4) at different pH was investigated by spectral methods, including absorption and resonance light-scattering spectrometry. According to the changes of color and absorption spectra of colloidal gold solution in presence of human C4, the interaction between colloidal gold and human C4 was quantitatively investigated using a semi-empirical "flocculation parameter". At the same time, the changes of resonance light-scattering spectra and transmission electron microscopy (TEM) images indicate that the aggregation of colloidal gold happens by electrostatic interaction in presence of human C4 in the pH range 5-6. However, the colloidal gold solution remains stable at pH >6 and pH <5 due to the repulsive electrostatic interaction between colloidal gold and human C4. The flocculation parameter is directly proportional to the concentration of human C4 in the range from 9.7 to 233.0 microgl(-1). In addition, the interactions between the colloidal gold and bovine serum albumin (BSA) as well as human serum albumin (HSA) were also investigated using the same methods. It was found that there was no aggregation of colloidal gold in presence of BSA and HSA in the pH range 5-6. However, when the pH of solution is 4, the aggregation of colloidal gold happens. Because BSA and HSA have different structure, the intensity of aggregation of colloidal gold in presence of BSA is greater than that in presence of HSA at pH 4.

Animals↗

PubMed2005

Determination of human complement factor C4 using resonance light-scattering technique with sodium dodecylbenzene sulphonate probe.

Based on the interaction between human complement factor C4 (human C4) and sodium dodecylbenzene sulphonate (SDBS) and the resonance light-scattering (RLS) technique, a highly sensitive assay for human C4 using resonance light-scattering technique was developed. At pH 2.8 Na2HPO4-citric acid buffer solution, the RLS intensities of SDBS system at 283, 503 and 600 nm were obviously enhanced in the presence of human C4. The effects of surfactant, pH, incubation time, concentration of SDBS and foreign substances on the enhanced RLS intensity of system were investigated. Under the optimum conditions, the enhanced RLS intensity is directly proportional to the concentration of human C4 in the range of (0.5-120)x10(-6)gl-1 and the linear regression equation was obtained with high correlation coefficient. This RLS technique was applied to the determination of human C4 in some synthetic samples with good recovery. Moreover, it was found that the electrostatic interaction is the main binding force between SDBS and human C4.

Benzenesulfonates↗

PubMed2005

Differential regulation of proteasome activity in the nucleus and the synaptic terminals.

Proteasome is a multi-subunit proteolytic complex that degrades proteins covalently linked to multiple molecules of ubiquitin. Earlier studies showed a role for the ubiquitin-proteasome pathway in several models of long-term memory and other forms of synaptic plasticity. In Aplysia, the ubiquitin-proteasome pathway has been shown to contribute to the induction of long-term facilitation. In other model systems, ubiquitin-proteasome-mediated proteolysis has also been shown to play a role in synapse development. Previous studies of synaptic plasticity focused on changes in components or the substrates of the ubiquitin-proteasome pathway in whole neurons. Modification of specific synapses would require precise spatial and temporal regulation of the components of the ubiquitin-proteasome pathway within the subcellular compartments of neurons during learning. As a first step towards testing the idea of local regulation of the ubiquitin-proteasome pathway in neurons, we investigated proteasome activity in nuclear and synaptosomal fractions. Here we show that proteasome activity in the synaptic terminals is higher compared to the activity in the nucleus in the Aplysia nervous system as well as in the mouse brain. Furthermore, the proteasome activity in the two neuronal compartments is differentially modulated by protein kinases. Differential regulation of proteasome activity in neuronal compartments such as the synaptic terminals is likely to be a key mechanism underlying synapse-specific plasticity.

Animals↗

PubMed2005

Improved solvent-free microwave extraction of essential oil from dried Cuminum cyminum L. and Zanthoxylum bungeanum Maxim.

Solvent-free microwave extraction (SFME) is a recently developed green technique which is performed in atmospheric conditions without adding any solvent or water. SFME has already been applied to extraction of essential oil from fresh plant materials or dried materials prior moistened. The essential oil is evaporated by the in situ water in the plant materials. In this paper, it was observed that an improved SFME, in which a kind of microwave absorption solid medium, such as carbonyl iron powders (CIP), was added and mixed with the sample, can be applied to extraction of essential oil from the dried plant materials without any pretreatment. Because the microwave absorption capacity of CIP is much better than that of water, the extraction time while using the improved SFME is no more than 30 min using a microwave power of 85 W. Compared to the conventional SFME, the advantages of improved SFME were to speed up the extraction rate and need no pretreatment. Improved SFME has been compared with conventional SFME, microwave-assisted hydrodistillation (MAHD) and conventional hydrodistillation (HD) for the extraction of essential oil from dried Cuminum cyminum L. and Zanthoxylum bungeanum Maxim. By using GC-MS system the compositions of essential oil extracted by applying four kinds of extraction methods were identified. There was no obvious difference in the quality of essential oils obtained by the four kinds of extraction methods.

Chromatography, Liquid↗

PubMed2005

Novel and simple nonaqueous capillary electrophoresis separation and determination bioactive triterpenes in Chinese herbs.

Three bioactive triterpenes ursolic acid, oleanolic acid and 2alpha,3beta,24-trihydroxy-urs-12-en-28-oic acid were simultaneously separated by nonaqueous capillary electrophoresis (NACE) with methanol:acetonitrile (65:35 v/v) mixture containing 90 mm trishydroxymethylaminomethane (Tris) at an applied voltage of +25 kV and a hydrodynamic injection of 5s. The effect of solvent composition, electrolyte nature and concentration on the electrophoretic behavior of the analytes were systematically studied. Separations were carried out in a fused-silica capillary tube with UV detection at 214 nm. Good separation and correlation coefficients were obtained. Meanwhile, the method was applied to separation and determination the three components in six Chinese herbs extraction. It is concluded that this method could be used for speedy and accurate qualitative and quantitative analysis of bioactive triterpenes in Chinese herbs.

Acetonitriles↗

PubMed2005

[Studies on the flavonoid constituents in herb of Eremosparton songoricum].

OBJECTIVE: To study the chemical constituents from Eremosparton songoricum. METHOD: The compounds were isolated with silica gel column chromatography and the structures of these compounds were elucidated by means of spectral analysis. RESULT: The seven compounds were identified as: 5,7,4'-trihydroxyflavone (apigenin) (I), 5-hydroxy-7,4'-dimethoxyflavone (II), 5,7-dihydroxy-3',4'-dimethoxyflavone (III), 5,7-dihydroxy-4'-methoxyflavone (acacetin) (IV), 5,7,4'-trihydroxy-3'-methoxyflavone (chrysoeriol) (V), 5,6,3',4'-tetrahydroxy-7-methoxyflavone (pedalitin) (VI) and 5,4'-dihydroxy-7,3'-dimethoxyflavone-4'-O-D-glucoside (flavogadorinin) (VII). CONCLUSION: These constituents were obtained from E. songoricum for the first time.

Apigenin↗

PubMed2005

[Studies on chemical constituents in herb of Lamium maculatum var. kansuense (II)].

OBJECTIVE: To study the chemical constituents from Lamium maculatum var. kansuense. METHOD: The chemical constituents were isolated and repeatedly purified on silica gel column and the structures were elucidated by the NMR spectra and physico-chemical properties. RESULT: Six compounds were obtained and identified as polypodine B (I), 5-OH-8-epiloganin (II), shlanzhiside methyl ester (III), liriodendrin (IV), quercitroside (V), uridine (VI). CONCLUSION: Compound IV was found from genus Lamium for the first time and the rest of the compounds were found from Lamium maculatum var kansuense for the first time.

Ecdysterone↗

PubMed2005

Cytotoxic ent-kaurane diterpenoids from Isodon weisiensis C. Y. Wu.

A new ent-kaurane diterpenoid, weisiensin B (1), was isolated from the leaves of Isodon weisiensis C. Y. Wu, along with four known ones, kamebanin (2), kamebacetal A (3), macrocalyxin D (4) and excisanin D (5). Their structures were determined by spectroscopic means. Compound 1-4 showed significant cytotoxic activity against Bel-7402 and HO-8910 cells.

Antineoplastic Agents, Phytogenic↗

PubMed2005

[A Chinese autosomal dominant polycystic kidney disease family probably related to PKD2 gene].

OBJECTIVE: To study the genetic heterogeneity of autosomal dominant polycystic kidney disease (ADPKD) in Chinese. METHODS: Using polymerase chain reaction (PCR) and non-denatured polyacrylamide gel electrophoresis, the authors analyzed eight microsatellite markers closely linked to PKD1 or PKD2 genes respectively in a Chinese ADPKD family. RESULTS: Seven informative markers were found in this family, including KG8, SM6, CW4 and CW2 which are tightly linked to PKD1, and D4S1563, D4S414 and D4S423 which are linked to PKD2. After the process of genotyping, the haplotypes were estimated with Cyrillic 2.0, and the linkage-based analysis suggested that the disease is not linked to PKD1 other than PKD2. CONCLUSION: In China this non-PKD1 family is the second one, but it is the first reported PKD2 family showing the genetic heterogeneity of ADPKD in Chinese. In the family the affected mother transmits the disease and the affected members' phenotypes are eterogeneous. In addition, the existing "anticipation" and the presence of the disease in a child of this family suggest that non-PKD1 linked families may have early-onset of the disease in child.

Adult↗

PubMed2005

[Studies on triterpenoid constituents from Rabdosia japonica var. galaucocalyx].

OBJECTIVE: To study the chemical constitutes in Rabdosia japonica var. galaucocalyx . METHOD: The compounds were isolated by nomal phase silica gel chromatography. The structures were identified by physical and spectral data. RESULT: Nine triterpenoids were isolated and identified as friedelin (I), 3beta, 28-dihydroxy-ursane (II), ursolic acid (III), 3beta-acetyloxy-ursolic acid (IV), 2alpha, 3alpha-dihydroxy-urs-12-en-28-oic acid (V), 2alpha, 3alpha, 23-trihydroxy-urs-12-en-28-oic acid (VI), oleanic acid (VII), beta-sitosterol (VIII), daucousterol (IX). CONCLUSION: Compounds I, II, IV, V and VI were isolated from R. japonica var. galaucocalyx for the first time.

Isodon↗

PubMed2004

Suppression of tumor growth and angiogenesis in vivo by a truncated form of 24-kd fibroblast growth factor (FGF)-2.

Efforts to treat tumors have routinely depended on disruption of cell proliferation by a variety of methods, many involving stimulation of apoptosis. We have previously shown that a truncated form of 24-kd basic fibroblast growth factor consisting of the amino terminal 86 amino acids inhibits migration of tumor and endothelial cells in vitro. In the present study, this peptide was tested for its ability to suppress angiogenesis and tumor growth using the murine dorsal skin-fold chamber model in vivo. Treatment of MCF-7 breast carcinoma tumor spheroids with this peptide resulted in cessation of the angiogenic response and a significant reduction in tumor size. Blood vessels that did form were poorly developed. In addition to inhibiting angiogenesis, the peptide also inhibited migration of Lewis lung carcinoma cells away from the tumor core before onset of angiogenesis indicating that the peptide-mediated inhibition of migration affects both angiogenesis and tumor growth independently. Despite inhibition of tumor cell migration, the peptide had no effect on neutrophil or eosinophil chemotaxis. This study demonstrates that the truncated form of 24-kd basic fibroblast growth factor is effective in suppressing tumor development in vivo through inhibition of angiogenesis as well as inhibition of tumor cell migration without compromising other homeostatic events.

Angiogenesis Inhibitors↗

PubMed2004

[Effect of Fe and Fe2+ on hydrogen production capacity with mixed culture].

The effects of Fe and Fe2+ concentration in the external environment on hydrogen production capacity of ethanol-type fermentative microorganism flora were investigated. The optimum range of Fe and Fe2+ concentration enhanced hydrogen production were obtained and the characteristic of fermentation types at different concentration of Fe and Fe2+ were discussed. It was demonstrated that both Fe and Fe2+ were able to enhance the hydrogen production capacity of microorganism flora. The maximum hydrogen production yield of 143.7mL x g(-1) glucose and the maximum specific hydrogen production rate 21.2mL x (h x g)(-1) were obtained at Fe2+ concentration of 200mg x L(-1) and 50mg x L(-1). The maximum hydrogen production yield of 156.1mL x g(-1) glucose and the maximum specific hydrogen production rate 23.5mL x (h x g)(-1) were obtained at Fe concentration of 1000mg x L(-1) and 500mg x L(-1). At the same concentration, the enhancement of Fe is better than Fe2+ when the concentration is higher than 50 mg x L(-1). A sequential extraction technique was used to represent arbitrary divisions between different metal forms of Fe2+ in the mixed culture.

Bacteria↗

PubMed2002

Inhibition of cell migration and angiogenesis by the amino-terminal fragment of 24kD basic fibroblast growth factor.

The 24-kDa form of basic fibroblast growth factor inhibits the migration of endothelial cells and mammary carcinoma cells while continuing to promote cell proliferation. This molecule consists of the 18-kDa fibroblast growth factor sequence plus an additional 55 amino acids at the amino-terminal end. Antibody neutralization studies suggested that the inhibition of migration is associated with these 55 amino acids, whereas the promotion of proliferation localizes to the 18-kDa domain. To determine whether 24kD basic fibroblast growth factor could be modified to eliminate its effect on cell proliferation but retain its inhibition of migration, portions of the carboxyl-terminal end of 24kD fibroblast growth factor were deleted, and the products were tested on MCF-7 and endothelial cells. A protein consisting of the 55 amino acids of the amino-terminal end and the first 31 amino acids of 18kD basic fibroblast growth factor (ATE+31) inhibited migration by 80% but did not promote cell growth. Arginine to alanine substitutions within the first 21 amino acids of the carboxyl-terminal end substantially reduced the efficacy of ATE+31, whereas substitutions in the remaining part of the molecule had no effect. Competition binding experiments showed that ATE+31 does not compete with 24kD basic fibroblast growth factor for binding to fibroblast growth factor receptor 1. In an in vivo matrigel plug assay, 150 nm ATE+31 peptide reduced angiogenesis by 80%. These studies demonstrate that the amino-terminal end of 24kD basic fibroblast growth factor is responsible for an activity that inhibits the migration rates of cultured cells as well as the angiogenic response in vivo.

Angiogenesis Inhibitors↗