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Biomedical subjects

Xiaoming Wu

Publications and source records attributed to Xiaoming Wu.

10 recordsLinked to original sources
PubMed2003

Biomimetic synthesis of gramicidin s and analogues by enzymatic cyclization of linear precursors on solid support.

[reaction: see text] Gramicidin S is a potent decapeptide antibiotic with high hemolytic activity but is unlikely to provoke microbial resistance. Here we demonstrate that gramicidin thioesterase (GrsB TE) correctly cyclizes immobilized linear decapeptide precursors into head-to-tail products, indicating its suitability for parallel solid-phase synthesis of gramicidin analogues from linear precursors on solid support. This chemoenzymatic method will enable the optimization of the therapeutic index of the natural product to fight microbial resistance.

Anti-Bacterial Agents↗
PubMed2003

[In vivo measurement of rabbits brain impedance frequency response and the elementary imaging of EIT].

The in vivo measurements of rabbit brain tissue impedance were taken under both normal and ischemic conditions by using two-electrode measurement method in the frequency range from 0.1 Hz to 1 MHz. The dynamic images about the resistivity of cerebral ischemia were reconstructed based on a 16-electrode system. The results of in vivo measurement showed that the ratio of impedance increased can be as high as 75% at frequencies lower than 10 Hz. In the range from 1 KHz to 1 MHz, the ratio showed a constant value of 15%. The electrical impedance tomography (EIT) images obtained suggested that the regions of impedance changes highly correspond to the position of ischemia. It is confirmed that the brain function changes caused by local deficiency of blood can be detected and imaged by EIT method.

Animals↗
PubMed2003

[The complex impedance frequency response and the equivalent circuit model of human brain].

The complex impedance measurements of human brain tissue in vitro are made by using four-electrode measurement methods in the frequency range from 0.1 Hz to 1 MHz. The Solartron 1255 B frequency response analyzer is used. The frequency response curves of the imaginary part of human brain's complex impedance do not appear as a single peak curve which other bio-tissues show, and the Cole-Cole diagram of human brain is different from the others as well. The construction of the equivalent circuit model obtained is more complex. However, these characteristics of human brain are all the same as rabbit brain's. The equivalent circuit model obtained will be helpful to constructing the equivalent circuit model of human head in the EIT researches.

Adult↗
PubMed2002

Synthesis of tyrocidine A and its analogues by spontaneous cyclization in aqueous solution.

[reaction: see text] Head-to-tail cyclization of peptides is a multistep process involving tedious C-terminal activation and side chain protection. Here we report a facile, quantitative cyclization method in aqueous ammonia solution for the total syntheses of the cyclic decapeptide antibiotic Tyrocidine A and its analogues from their fully deprotected linear thioester precursors on a solid support. This novel aqueous method is conformation-dependent and may be applicable to syntheses of other natural cyclic peptides.

Anti-Bacterial Agents↗
PubMed2002

Detection of CYP I A1 polymorphisms with a colorimetric method based on mismatch hybridization.

BACKGROUND: CYP I A1 polymorphisms, which have been reported to be associated with an elevated risk of lung cancer, are usually detected through conventional methods such as PCR-restriction fragment length polymorphism, allele-specific PCR and single-strand conformational polymorphism. METHODS: An assay that makes use of differences in thermal stability between perfect match and non-perfect match hybrids has been developed. Two oligonucleotides probes for each CYP1A1 polymorphic site were designed and labeled with digoxigenin. After hybridization with amplified DNA fragment, the hybrids were detected with a colorimetric method and the genotype were identified by calculating the ratio of signals obtained with two probes. RESULTS: The ratios for three genotypes obtained from 50 samples can be divided into three distinctive nonoverlapped groups when applying to m(1) and m(2) sites of CYP1A1 locus, which demonstrated the feasibility of this assay to detect CYP I A1 polymorphisms. CONCLUSION: Compared with other methods, this assay has lower cost, is fast, simple and is suitable for a screening test in routine laboratory.

Alleles↗
PubMed2002

[Exploratory study on natural focus and its causative agent of genotype of Lyme disease by polymerase chain reaction in the forest areas of Beijing].

OBJECTIVE: To learn the existence of natural focus of Lyme disease and its distribution. METHODS: A semi-nested polymerase chain reaction (PCR) method was developed for detection and genotyping of Borrelia burgdorferi on basis of outer surface protein A (OspA) gene. Ticks and mice collected from 6 forest areas in Beijing were detected with above methods. The positive PCR products were cloned and sequenced. The sequences were compared with published sequences for homology. IFA as used to detect IgG antibody on Borrelia burgdorferi. Lyme disease spirochete were isolated from H. longicornis were also attempted. RESULTS: B. Burgdorferi sensu lato were detected from 939 ticks and 250 mice specimens collected from above 6 study sites using primer pairs OA(1)/OA(4) and SL/OA(4). Only the specimens collected from Dongling mountain showed positive amplification. One in three adult Ixodes persulcatus with one of 57 nymph Ixodes persulcatus showed positive while 9 of 119 (7.56%) mice specimens showed positive, of which 8 were B. grinii and one B. afzelii. In this study, we attempted to isolate B. burgdorferi sensu lato strains from 160 H. longicornis ticks (20/group) but failed. Serological survey showed a 9.1% (5/55) infection rate with B. burgdorferi sensu lato in the mice of Dongling mountain forest areas. CONCLUSIONS: The natural focus of Lyme disease including B. garinii and B. afzelii might have existed in Dongling mountain of Mentougou district, Beijing. Ixodes persulcatu and mice may serve as vectors and reservoirs, respectively.

Animals↗
PubMed2002

[Hidden Markov model used in protein sequence analysis].

Hidden Markov model (HMM) used in the research of protein is a new field of bioinformatics. Nowadays large amount of data about protein sequences and structures have been obtained. Traditional methods of protein analysis are no longer used. Biologists have updated their research methods with computer technology and statistics, which can deal with large amount of data. HMM can be used to distinguish protein sequence with the same characteristics. A family of protein from SCOP database was selected, through which a HMM model representing the family was obtained, and then the model was utilized to analyze protein sequences. Results indicate that HMM can express particular family of protein, and recognize the given protein sequences of the family from many sequences.

Algorithms↗
PubMed2002

[The impedance frequency response of the human skull].

The human skull impedance was quantitatively measured by means of Frequency Response Analyzer and its software. The impedance-frequency response curves of human skull were obtained. By analyzing the curves, we found that the characteristic frequency of human skull should be around 10 KHz.

Adult↗