Cloning and characterization of the gene for amylosucrase from Neisseria polysaccharea: production of a linear alpha-1,4-glucan.

The gene for the amylosucrase from Neisseria polysaccharea (ATCC 43768) was cloned by use of a functional expression system in Escherichia coli XL1-Blue. The deduced amino acid sequence of the protein has homology to the sequences of the alpha-amylase class of enzymes, with the highest similarities being found to the sequences of the trehalose synthase from Pimelobacter sp. strain R48 (17) and amylomaltase from Thermotoga maritima (11). However, the regions of highest homology within the alpha-amylase class of enzymes, which are essential for the catalytic activity, are only scarcely found in the sequence of amylosucrase. By using the enzyme isolated from culture supernatants of transformed E. coli cells, it is possible to synthesize linear alpha-1,4-glucans from sucrose, indicating that the enzyme is not capable of producing alpha-1,6-glycosidic linkages on its own

Information retrieval: implementing and evaluating search engines

Information retrieval is the foundation for modern search engines. This textbook offers an introduction to the core topics underlying modern search technologies, including algorithms, data structures, indexing, retrieval, and evaluation. The emphasis is on implementation and experimentation; each chapter includes exercises and suggestions for student projects. Wumpus -- a multiuser open-source information retrieval system developed by one of the authors and available online -- provides model implementations and a basis for student work. The modular structure of the book allows instructors to use it in a variety of graduate-level courses, including courses taught from a database systems perspective, traditional information retrieval courses with a focus on IR theory, and courses covering the basics of Web retrieval. In addition to its classroom use, Information Retrieval will be a valuable reference for professionals in computer science, computer engineering, and software engineering

Adding Full-Text Filesystem Search To Linux

this article we report on experiences we had while developing Wumpus, a full-text filesystem search engine for Linux. We discuss major design decisions and point out some changes that, from a search engine developer's point of view, need to be made to the Linux kernel to support real-time filesystem indexing and search. The goal of our research efforts is the development of a unified filesystem search engine that can be used by multiple users and that can cover multiple storage devices, both local and network-wide (local hard drives, USB sticks, NFS mounts, etc.). Search results returned by the engine should always be consistent with the current content of the file system. Inconsistencies resulting from recent file changes should have a lifetime of at most a few seconds. The vehicle we are using to reach that goal is the Wumpus search engine, a hybrid filesystem search and general-purpose information retrieval system. Wumpus is free software, licensed under the terms of the GNU General Public License, and is available for download from the Wumpus Web site, http://www.wumpus-search.org/. It is work in progress and not yet suitable for everyday use as a filesystem search engine. Wumpus is a keyword-based search engine. It supports state-of-the-art result ranking algorithms, as well as structural queries (phrase queries and near operators) and Boolean operators. Its backend index data structure is a set of inverted files. Each inverted file realizes a mapping from terms to their respective occurrences within the file system. (For a thorough discussion of inverted files and their advantages over alternative index data structures, see Zobel et al. [4]). In conjunction, the inverted files can be used to efficiently obtain a list of all occurrences of a given term within the ..