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Xiangming Fang

Publications and source records attributed to Xiangming Fang.

14 recordsLinked to original sources
PubMed2007

Modeling the probability distribution of positional errors incurred by residential address geocoding.

BACKGROUND: The assignment of a point-level geocode to subjects' residences is an important data assimilation component of many geographic public health studies. Often, these assignments are made by a method known as automated geocoding, which attempts to match each subject's address to an address-ranged street segment georeferenced within a streetline database and then interpolate the position of the address along that segment. Unfortunately, this process results in positional errors. Our study sought to model the probability distribution of positional errors associated with automated geocoding and E911 geocoding. RESULTS: Positional errors were determined for 1423 rural addresses in Carroll County, Iowa as the vector difference between each 100%-matched automated geocode and its true location as determined by orthophoto and parcel information. Errors were also determined for 1449 60%-matched geocodes and 2354 E911 geocodes. Huge (> 15 km) outliers occurred among the 60%-matched geocoding errors; outliers occurred for the other two types of geocoding errors also but were much smaller. E911 geocoding was more accurate (median error length = 44 m) than 100%-matched automated geocoding (median error length = 168 m). The empirical distributions of positional errors associated with 100%-matched automated geocoding and E911 geocoding exhibited a distinctive Greek-cross shape and had many other interesting features that were not capable of being fitted adequately by a single bivariate normal or t distribution. However, mixtures of t distributions with two or three components fit the errors very well. CONCLUSION: Mixtures of bivariate t distributions with few components appear to be flexible enough to fit many positional error datasets associated with geocoding, yet parsimonious enough to be feasible for nascent applications of measurement-error methodology to spatial epidemiology.

Censuses↗
PubMed2006

Vector prime/protein boost vaccine that overcomes defects acquired during aging and cancer.

We showed that the Ad-sig-TAA/ecdCD40L vaccine induces a tumor suppressive immune response to the hMUC-1 and rH2N tumor-associated self Ags (TAA) and to the Annexin A1 tumor vascular Ag, even in mice in which anergy exists to these Ags. When the TAA/ecdCD40L protein is given s.c. as a boost following the Ad-sig-TAA/ecdCD40L vector, the levels of the TAA-specific CD8 T cells and Abs increase dramatically over that seen with vector alone, in young (2-mo-old) as well as old (18-mo-old) mice. The Abs induced against hMUC-1 react with human breast cancer. This vaccine also induces a 4-fold decrement of negative regulatory CD4CD25FOXP3-T cells in the tumor tissue of 18-mo-old mice. These results suggest that the Ad-sig-TAA/ecdCD40L vector prime-TAA/ecdCD40L protein boost vaccine platform may be valuable in reducing postsurgery recurrence in a variety of epithelial neoplasms.

Aging↗
PubMed2005

Tandem repeat mhBD2 gene enhance the soluble fusion expression of hBD2 in Escherichia coli.

Human beta-defensin-2 (hBD2) is a cysteine-rich cationic antimicrobial peptide with low molecular weight that exhibits a broad range of antimicrobial activity. To improve the expression level of hBD2 in Escherichia coli, tandem repeats of mature hBD2 gene were constructed and expressed as fusion proteins (TrxA-nmhBD2, n = 1, 2, 4, 8) by constructing the vectors of pET32-nsmhBD2 (n = 1, 2, 4, 8). The results showed that the tandem repeats of mhBD2 gene were highly expressed in our constructed system. Comparing the expression levels of soluble mhBD2, BL21(DE3)/pET32-2smhBD2 was selected as an ideal recombinant strain for mature hBD2 production. Under the optimized conditions of cultivation and isopropylthiogalactoside (IPTG) induction, the maximum expression level of soluble mature hBD2 (0.76 g/l) with the highest percentage of fusion protein in soluble proteins (62.2%) was obtained in the present work, which was the highest yield of hBD2 reported so far.

Biotechnology↗
PubMed2005

Recent advances in the research and development of human defensins.

Human defensins are a family of cationic antimicrobial peptides with molecular weights of 4-5 kDa, containing a conserved six disulphide-linked cysteine motif. During the last two decades a series of endogenous alpha- and beta-human defensins were discovered. They exhibit a broad range of antimicrobial properties and are thought to be ideal therapeutic agents because of their potential ability to circumvent the problems of acquired resistance often observed with other antimicrobial therapies. Because of their appealing medical and pharmaceutical potential there has been an emphasis on human defensins in medical and molecular biology research in recent years. This paper aims to present a comprehensive review of recent advances in the study of human defensins including their discovery, classification, molecular properties, expression, mechanisms of action and potential medical applications. In addition, the advances in producing human defensins via genetic engineered cells are summarized from research works in our group (besides host cells including E. coli, B. subtilis and yeast systems, the cell-free protein synthesis system was also employed to express human beta-defensin-2) along with other related published works. The present challenges and prospects for the potential application of human defensins are also discussed.

Gene Expression Regulation↗
PubMed2005

Immunoaffinity separation of plasma proteins by IgY microbeads: meeting the needs of proteomic sample preparation and analysis.

Separation of complex protein mixtures that have a wide dynamic range of concentration, such as plasma or serum, is a challenge for proteomic analysis. Sample preparation to remove high-abundant proteins is essential for proteomics analysis. Immunoglobulin yolk (IgY) antibodies have unique and advantageous features that enable specific protein removal to aid in the detection of low-abundant proteins and biomarker discovery. This report describes the efficiency and effectiveness of IgY microbeads in separating 12 abundant proteins from plasma with an immunoaffinity spin column or LC column. The protein separation and sample preparation process was monitored via SDS-PAGE, 2-DE, LC-MS/MS, or clinical protein assays. The data demonstrate the high specificity of the protein separation, with removal of 95-99.5% of the abundant proteins. IgY microbeads against human proteins can also selectively remove orthologous proteins of other mammals such as mouse, rat, etc. Besides the specificity and reproducibility of the IgY microbeads, the report discusses the factors that may cause potential variations in protein separation such as protein-protein interactions (known as "Interactome"), binding and washing conditions of immunoaffinity reagents, etc. A novel concept of Seppromics is introduced to address methodologies and science of protein separation in a context of proteomics.

Albumins↗
PubMed2005

Expression of human beta-defensin-2 with multiple joined genes in Escherichia coli.

Human beta-defensin (HBD)-2 is a small cationic peptide with a broad range of antimicrobial activity. In this study, multiple copies of the hBD2 gene were linked in tandem, and a number of different Escherichia coli expression vectors were evaluated, including pQE-30, pBV220, pET-28a(+), and pGEX-4T-2. No expression of multiple joined genes was detectable in the pQE-30 expression system, whereas in pBV220 with one or two joined hBD2 genes and in pET-28a(+) with one, two, or four copies, target proteins were expressed at a low level. Only when pGEX-4T-2 was applied as expression plasmid with one or two joined hBD2 genes were target proteins expressed in high level, and the expressed fusion proteins account for 26 and 16% of the total insoluble proteins, respectively. In the pGEX-4T-2 and pET-28a(+) expression systems, the effects of multiple joined genes on the growth of host strains and plasmid stability were examined. Host cells containing plasmid carrying fewer copies of hBD2 genes were faster in cell growth. Plasmid stability decreased with an increase in multiple joined genes, which was especially noticeable in the pET-28a(+) system. Furthermore, the presence of glucose in culture medium brought about a positive effect on plasmid stability when using pET28-nhBD2 as expression vectors.

Blotting, Western↗
PubMed2004

Fusion expression of human beta-defensin-2 from multiple joined genes in Escherichia coli.

Human beta-defensin-2 (hBD-2) is a cysteine-rich cationic low molecular weight antimicrobial peptide, which exhibits a broad range of antimicrobial activity without observed acquired resistance. In this work, multiple copies of the hBD-2 gene were linked in tandem and the expression of the multiple joined genes in two fusion expression system, pET28a(+) and pGEX-4T-2, was examined. Using plasmid pET28a(+) with one, two, and four copies of the hBD-2 gene, the expressed level was relatively low, whereas much higher with plasmid pGEX-4T-2, and the fusion products, most of which in insoluble form, account for approximately 26% of the total insoluble cellular proteins.

Cloning, Molecular↗
PubMed2004

Preferential codons enhancing the expression level of human beta-defensin-2 in recombinant Escherichia coli.

Human beta-defensin-2 (hBD2) is a small antimicrobial peptide with potential as a therapeutic agent. The effect of codon usage on the expression of hBD2 in Escherichia coli was studied. Two coding sequences encoding the same hBD2 precursor were both expressed as fusion protein with thioredoxin in E. coli BL21 (DE3). One is the wild-type human cDNA and the other is a gene synthesized by a PCR-based method in which rare codons were altered to those frequently used in E. coli. The expression level of recombinant hBD2 was over 50% of the total cellular protein when the synthetic gene with preferential codons was employed which was a 9-fold enhancement over the wild-type cDNA. The result shows the codon bias of the host was a major barrier in high-level expression of recombinant hBD2 and suggests a similar approach may be used in the expression of other defensins in E. coli.

Amino Acid Sequence↗
PubMed2003

IL-10 polymorphism is associated with increased incidence of severe sepsis.

OBJECTIVE: To investigate whether three biallelic polymorphisms at positions -592, -819 and -1082 in the promoter region of the IL-10 gene are associated with increased incidence of severe sepsis. METHODS: The IL-10 -592, -819 and -1082 polymorphisms were typed using polymerase chain reaction followed by digestion with the restriction enzymes RsaI, MaeIII and MnlI, respectively. RESULTS: Patients with severe sepsis were more likely to have IL-10 -1082 allele 1, compared with controls (P < 0.05). Genotype distribution of the IL-10 -1082 polymorphism significantly differed between patients and controls (P < 0.05). However, the allele frequencies and genotype distribution of the IL-10 -1082 polymorphism did not differ between surviving and dead patients (P > 0.05). No significant differences in the genotype distribution and allele frequencies of the IL-10 -592 and IL-10 -819 polymorphisms were observed between patients with severe sepsis and healthy controls, nor between surviving and dead patients (P > 0.05). CONCLUSIONS: The polymorphism at position -1082 in the promoter region of the IL-10 gene may be associated with susceptibility to severe sepsis. In contrast, the other two highly linked IL-10 polymorphisms are not associated with incidence or the outcome of severe sepsis.

Alleles↗
PubMed2002

Cloning and expression of human beta-defensin-2 gene in Escherichia coli.

Human beta-defensin-2 (hBD-2), a small cationic peptide, exhibits a broad range of antimicrobial activity. It has been found to play important roles in innate and adaptive immune responses against microbial invasion. For the purposes of this study, hBD-2 gene was cloned from the lesions of human condyloma acuminatum. An expression vector was constructed and transformed into E. coli. hBD-2 was expressed as a fusion protein in both the soluble and insoluble forms, which was further confirmed by western blotting analysis.

Anti-Bacterial Agents↗
PubMed2002

[Association of tumor necrosis factor microsatellites TNF with the susceptibility to and outcome of postoperative severe sepsis].

OBJECTIVE: To investigate whether tumor necrosis factor microsatellites TNFa and TNFb were associated with the susceptibility to and outcome of post operative severe sepsis. METHODS: 122 postoperative patients suffering from severe sepsis and 138 ethnically matched healthy individuals (controls) were included in this study. The genotypes of microsatellites TNFa and TNFb were analyzed using modified nested-PCR followed by polyacrylamide gel electrophoresis with silver staining. RESULTS: Microsatellites TNFa and TNFb consisted of 14 alleles (TNFa1-14) and 5 alleles (TNFb1, 3-5, 7) respectively. The frequency of TNFa6 microsatellite allele was significantly higher in patients with severe sepsis than in controls (20.1% versus 10.5%, P < 0.05). The frequency of TNFa2 microsatellite allele was significantly lower in patients with severe sepsis than in controls (21.3% versus 31.5%, P < 0.05). Furthermore, among patients with severe sepsis, the frequency of TNFa10 microsatellite allele was significantly higher in non-survivors than in survivors (19.5% versus 9.5%, P < 0.05). Whereas, there was no significant difference in the distribution of TNFb microsatellite alleles between patients and controls, and non-survivors and survivors (both P > 0.05). CONCLUSION: Microsatellite TNFa is significantly associated with both the susceptibility to and outcome of severe sepsis. In contrast, microsatellite TNFb is neither associated with the susceptibility to severe sepsis nor with the outcome of severe sepsis.

Disease Susceptibility↗
PubMed1999

Catalytic Approach for the Formation of Optically Active Allyl alpha-Amino Acids by Addition of Allylic Metal Compounds to alpha-Imino Esters.

A new catalytic enantioselective approach for the formation of allyl alpha-amino acid derivatives by reaction of N-tosyl alpha-imino esters with allyl stannanes and silanes catalyzed by chiral copper(I) complexes has been developed. A series of different BINAP and phosphine-oxazoline (P,N) ligands have, in combination with various Lewis acids, been tested as chiral catalysts for allylation of N-tosyl alpha-imino esters. It has been found that both type of ligands, in combination with copper(I) salts, give highly valuable unsaturated alpha-amino acid derivatives. The reaction has been investigated for different allyl stannanes and silanes, and it has been found that tri-n-butyl allyl stannane gives the best results of the simple allyl compounds tested, leading to gamma,delta-unsaturated alpha-amino acid derivatives in up to 94% yield and with up to 83% ee, which can be improved to be >95% ee by recrystallization. The reaction has also been investigated using different acyclic and cyclic allyl stannanes leading to various types of unsaturated alpha-amino acid derivatives in very high yield (up to 95%) and with up to 98% ee. The stereochemistry and absolute configurations of the allyl alpha-amino acid derivatives have been determined by X-ray analysis, and it is suggested that the reaction takes place as an ene-like reaction.

Journal Article↗
PubMedDate not supplied

High-level expression of a soluble functional antimicrobial peptide, human beta-defensin 2, in Escherichia coli.

In this work, taking human beta-defensin-2 (HBD2) as a demonstrative molecule, the strategies for high efficient production of functional human beta-defensins in E. coli were studied. Fusion mature HBD2 (TrxA-mHBD2) showed high solubility and productivity without the need for lowering the cultivation temperature. The solubility of target fusion protein could attain 81.3% even at 37 degrees C with a volumetric productivity as high as 235 mg/L in a rich medium MBL at the same temperature and reached 346 mg/L at 28 degrees C. The His-Tag in the fusion protein enabled the application of affinity chromatography separation to obtain high purity of the overexpressed recombinant fusion protein. After digestion by enterokinase, purification via cationic exchange chromatography, and desalting by ultrafiltration, mature HBD2 product was obtained with a purity of 95% in an overall recovery of 29.2%. The antimicrobial activity of the recombinant mature HBD2 and the influence factors were tested using E. coli K12D31 as a sensitive strain.

Amino Acid Sequence↗