PeerDB-Peering into Personal Databases

In this talk, we will present the design and evaluation of PeerDB, a peer-to-peer (P2P) distributed data sharing system. PeerDB distinguishes itself from existing P2P systems in several ways. First, it is a full-fledge data management system that supports fine-grain content-based searching. Second, it facilitates sharing of data without shared schema. Third, it combines the power of mobile agents into P2P systems to perform operations at peers' sites. Fourth, PeerDB network is self-configurable, i.e., a node can dynamically optimize the set of peers that it can communicate directly with based on some optimization criterion.Singapore-MIT Alliance (SMA

Detection of hepatitis B virus core antigen by phage display mediated TaqMan real-time immuno-PCR

The core antigen (HBcAg) of hepatitis B virus (HBV) is one of the markers for the identification of the viral infection. The main purpose of this study was to develop a TaqMan real-time detection assay based on the concept of phage display mediated immuno-PCR (PD-IPCR) for the detection of HBcAg. PD-IPCR combines the advantages of immuno-PCR (IPCR) and phage display technology. IPCR integrates the versatility of enzyme-linked immunosorbent assay (ELISA) with the sensitivity and signal generation power of PCR. Whereas, phage display technology exploits the physical association between the displayed peptide and the encoding DNA within the same phage particle. In this study, a constrained peptide displayed on the surface of an M13 recombinant bacteriophage that interacts tightly with HBcAg was applied as a diagnostic reagent in IPCR. The phage displayed peptide and its encoding DNA can be used to replace monoclonal antibody (mAb) and chemically bound DNA, respectively. This method is able to detect as low as 10 ng of HBcAg with 108 pfu/ml of the recombinant phage which is about 10,000 times more sensitive than the phage-ELISA. The PD-IPCR provides an alternative means for the detection of HBcAg in human serum samples

Purification of bacteriophage M13 by anion exchange chromatography

M13 is a non-lytic filamentous bacteriophage (phage). It has been used widely in phage display technology for displaying foreign peptides, and also for studying macromolecule structures and interactions. Traditionally, this phage has been purified by cesium chloride (CsCl) density gradient ultracentrifugation which is highly laborious and time consuming. In the present study, a simple, rapid and efficient method for the purification of M13 based on anion exchange chromatography was established. A pre-packed SepFast™ Super Q column connected to a fast protein liquid chromatography (FPLC) system was employed to capture released phages in clarified Escherichia coli fermented broth. An average yield of 74% was obtained from a packed bed mode elution using citrate buffer (pH 4), containing 1.5 M NaCl at 1 ml/min flow rate. The purification process was shortened substantially to less than 2 h from 18 h in the conventional ultracentrifugation method. SDS-PAGE revealed that the purity of particles was comparable to that of CsCl gradient density ultracentrifugation method. Plaque forming assay showed that the purified phages were still infectious

Keyword Join: Realizing Keyword Search in P2P-based Database Systems

In this paper, we present a P2P-based database sharing system that provides information sharing capabilities through keyword-based search techniques. Our system requires neither a global schema nor schema mappings between different databases, and our keyword-based search algorithms are robust in the presence of frequent changes in the content and membership of peers. To facilitate data integration, we introduce keyword join operator to combine partial answers containing different keywords into complete answers. We also present an efficient algorithm that optimize the keyword join operations for partial answer integration. Our experimental study on both real and synthetic datasets demonstrates the effectiveness of our algorithms, and the efficiency of the proposed query processing strategies.Singapore-MIT Alliance (SMA

Keyword Join: Realizing Keyword Search for Information Integration

Information integration has been widely addressed over the last several decades. However, it is far from solved due to the complexity of resolving schema and data heterogeneities. In this paper, we propose out attempt to alleviate such difficulty by realizing keyword search functionality for integrating information from heterogeneous databases. Our solution does not require predefined global schema or any mappings between databases. Rather, it relies on an operator called keyword join to take a set of lists of partial answers from different data sources as input, and output a list of results that are joined by the tuples from input lists based on predefined similarity measures as integrated results. Our system allows source databases remain autonomous and the system to be dynamic and extensible. We have tested our system with real dataset and benchmark, which shows that our proposed method is practical and effective.Singapore-MIT Alliance (SMA

The release of hepatitis B core antigen from Escherichia coli by batch mode bead milling

The performance of a batch model bead mill on the release of hepatitis B core antigen (HBcAg) from Escherichia coli was investigated in this study. The operating parameters examined were impeller tip speed (8–14 m/s), biomass concentration [5–20% (w/v)] and bead loading [65–80% (v/v)]. The highest yield (24.3 mg/g cell) and rate constant (0.471 l/min) of HBcAg release were achieved at impeller tip speed of 14 m/s. However, the high-shear stress under these operating conditions caused damage of the HBcAg. The highest yield (22.7 mg/g cell) and rate constant (0.344 l/min) of HBcAg release were observed at biomass concentration of 20% (w/v). There was no significant effect of bead loading on the performance of bead milling being observed. In conclusion, the optimal operating condition for the release of HBcAg was at bead loading of 75% (v/v), biomass concentration of 20% (w/v) and impeller tip speed of 10 m/s

Urethral masson’s tumour: a rare and puzzling entity

Intravascular papillary endothelial hyperplasia (IPEH) or Masson’s tumour is a benign vascular proliferation that mimics other malignant vascular tumour. To date, this is the fourth case of Masson’s tumour at urethra being reported in the literature. A 65-year-old female Para 2, presented with post-menopausal bleeding. Examination revealed a 4x3x3 cm growth surrounding the urethral meatus. She underwent examination under anaesthesia and excision of the periurethral mass. Histopathological examination confirmed Masson’s tumour. Diagnosis and management of this uncommon tumour at a rare location was discussed

The direct recovery of recombinant hepatitis B core antigen from disruptate derived from continuous-flow bead milling

HBcAg (hepatitis B core antigen) is a nanoplex bioproduct that has a great potential in the development of therapeutic drugs and vaccines. In the present study, a continuous-flow bead milling for the disruption of Escherichia coli was optimized and a direct recovery protocol to isolate the recombinant HBcAg from the unclarified E. coli disruptate was developed. The optimal condition for continuous-flow bead milling for the release of HBcAg from E. coli was achieved at a feed flow rate of 15 litres/h, biomass concentration of 10% [ww/v (wet weight/vol.)] and impeller tip speed of 14 m/s. The sucrose-density-gradient analysis showed that the particulate form of the HBcAg released by this optimal condition is still preserved. In the direct purification of HBcAg from the unclarified disruptate, the AE-EBAC (anion-exchange expanded-bed adsorption chromatography) technique was employed. A 54% adsorption and 50.7% recovery of HBcAg were achieved in this direct recovery process. The purity of HBcAg recovered was 49.8%, which corresponds to a purification factor of 2.0. ELISA showed that the HBcAg recovered is functionally active