Biomedical subjects

T Z Wu

Publications and source records attributed to T Z Wu.

6 recordsLinked to original sources

PubMed2001

Exploring the recognized bio-mimicry materials for gas sensing.

This study was undertaken to synthesize peptides that are partially similar to the binding sites of human olfactory receptor protein. First, a putative 3-D model structure of human olfactory receptor protein (P30953) was modeled using a molecular simulation method. The computer docking simulation was then performed to determine the most plausible binding sites between the model structure and target gases, trimethylamine, ammonia, acetic acid, and o-xylene. According to the simulation result, a series of polypeptide sequences, horp61 for TMA, horp103 for o-xylene, horp109 for ammonia, and horp193 for acetic acid as recognized molecules were designed for gas sensing purposes. Preparing these peptides as corresponding gas sensing probes, the results showed a high relative sensitivity response of 6.7 for TMA (probe horp61), 5.1 for o-xylene (probe horp103), 11 for ammonia (probe horp109), and 28 for acetic acid (probe horp193), respectively. These results indicate that peptide mimicking of binding domain on olfactory receptor opens a new window and offers a novel strategy for the further development of recognized materials for gas sensing.

Amino Acid Sequence↗

PubMed2000

Synthetic peptide mimicking of binding sites on olfactory receptor protein for use in 'electronic nose'.

A putative tertiary structure model of the dog's olfactory receptor (olfd canfa) is established in this study. By using a target odorous compound (trimethylamine), it is possible to locate the most plausible binding sites between the receptor model structure and the target odorous molecules through computer docking simulations. The two short oligo-peptide sequences (orp61 and orp188) for trimethylamine sensing were identified, synthesized, purified and coated onto the surface of the separate piezoelectric gold electrodes. These two peptides show a high binding capability for trimethylamine. To further enhance the sensitivity of the polypeptides towards the target compound, the polarity and the degree of docking were changed by a site-specific modification technique. The orp61 sequence was modified by substituting two amino acids in the binding pocket resulting in 33% increase in sensitivity towards trimethylamine and reduced noises from other non-target chemicals. The techniques used in the present study offer a unique approach for synthesizing peptides in mimicking binding domain of olfactory receptors. The approach can be easily applied to further development of recognized molecules for gas sensing, especially for use in 'electronic noses'.

Amino Acid Sequence↗

PubMed2000

Purification and characterization of neutral sphingomyelinase from Helicobacter pylori.

Phospholipase activities of human gastric bacterium, Helicobacter pylori, are regarded as the pathogenic factors owing to their actions on epithelial cell membranes. In this study, we purified and characterized neutral sphingomyelinase (N-SMase) from the superficial components of H. pylori strains for the first time. N-SMase was purified 2083-fold with an overall recovery of 37%. The purification steps included acid glycine extraction, ammonium sulfate precipitation, CM-Sepharose, Mono-Q, and Sephadex G-75 column chromatography. Approximate molecular mass for the native N-SMase was around 32 kDa. When N-omega-trinitrophenylaminolauryl sphingomyelin (TNPAL-SM) was used as a substrate, the purified enzyme exhibited a K(m) of 6.7 microM and a V(max) of 15.6 nmol of TNPAL-sphingosine/h/mg of protein at 37 degrees C in 50 mM phosphate-buffered saline, pH 7.4. N-SMase reaches optimal activity at pH 7.4 and has a pI of 7.15. The enzyme activity is magnesium dependent and specifically hydrolyzed sphingomyelin and phosphatidylethanolamine. The enzyme also exhibits hemolytic activity on human erythrocytes. According to Western blot analysis, a rabbit antiserum against purified N-SMase from H. pylori cross-reacted with SMase from Bacillus cereus. Sera from individuals with H. pylori infection but not uninfected ones recognizing the purified N-SMase indicated that it was produced in vivo. In enzyme-linked immunosorbent assays, the purified N-SMase used as an antigen was as effective as crude protein antigens in detecting human antibodies to H. pylori.

Antibodies, Bacterial↗

PubMed2000

Expression of capsid [correction of caspid] protein VP1 for use as antigen for the diagnosis of enterovirus 71 infection.

To produce enterovirus 71 antigen for diagnostic purposes, the gene encoding the entire capsid protein VP1 was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned and expressed in Escherichia coli as a poly-histidine fusion protein. Western blotting experiments with sera from patients with enterovirus 71 infection indicated that immunoglobulin G (IgG) and IgM antibodies bound to a single polypeptide VP1. According to these results, IgM anti-VP1 appeared in sera of patients with a symptomatic enterovirus 71 acute infection, whereas IgG anti-VP1 was present in sera of past infection. This finding suggests that detecting IgG and IgM immune responses against linear epitopes of recombinant VP1 is an effective means of determining the different phases of enterovirus 71 infection. In addition, sera containing coxsackie virus 16 (CA16) antibodies did not cross-react with the recombinant VP1 of enterovirus 71, despite the homology between VP1 proteins of both viruses. Comparison with reference PCR and neutralization assays showed these antibody tests to be appropriate for the serodiagnosis of enterovirus 71 infection.

Antibodies, Viral↗

PubMed1999

A piezoelectric biosensor as an olfactory receptor for odour detection: electronic nose.

Humans can detect and differentiate the presence of different odours even at trace levels of these odorous compounds. The odour quantification of any particular samples is normally based on conventional panel decisions. Other analytical instruments could be used to detect trace levels of odorous molecules. This study presents the results of a biological sensor system subject to different odorants. The system consists of a sensor in which the isolated olfactory receptor proteins (ORPs) from bullfrogs (Rana spp.) were coated onto the surface of a piezoelectric (PZ) electrode, similar to the mechanism of human olfaction. The PZ crystal served as a signal transducer. The results indicate rapid (about 400 s), reversible, and longterm (up to 3 months) stable responses to different volatile compounds such as n-caproic acid, isoamyl acetate, n-decyl alcohol, beta-ionone, linalool, and ethyl caporate. The sensitivity of the sensor ranges from 10(-6)-10(-7) g, fully correlated with the olfactory threshold values of human noses. An array of six sensors consisting of five fractionated ORPs and one referenced phospholipid probe is able to respond to different odorants and form a typical fingerprint for each odorant.

Animals↗

PubMed1990

Gene probe coated piezoelectric biosensors for biochemical analysis.

A new method has been developed to monitor DNA hybridization by using piezoelectric (PZ) crystal biosensor system. AT-cut crystals, with a basic resonant frequency of 9 MHz, were modified by a series of surface pretreatment as followings: gold plated, anoidical oxidation and gamma-aminopropyltriethoxysilane treatment. Single stranded DNA probe was electro-blotted onto the surface of crystal electrodes. The DNA probe was further fixed on the crystal surface by UV crosslinking. The crystal sensor is dipped into the hybridization solution and the surface mass increase, caused by hybridization, is measured by the decrease in the resonant frequency of the crystal. The potential capability to obtain qualitative as well as quantitative information on a sample through such an DNA hybridization assay makes this technique an attractive alternative to conventional analytical techniques that require use of radio-isotope.

Biosensing Techniques↗