Improving the testability of switched-capacitor filters

A design-for-test methodology for SC filters is presented, based on an architecture using some additional circuitry and providing extra capabilities for both off- and on-line tests. The approach uses a comparison (voting) mechanism to indicate whether or not two copies of a filter element (a biquad, for instance) have a similar response during their actual operation. The design and implementation of a few filter examples are included to assess the potential usefulness of this new approach.     

Putting reader roles to the test: an ethnomethodological approach

That readers read within roles has long been argued by literary theorists and more recently by technical communication theorists. Yet few scholars have attempted to put their theories to a test. The study reported in this paper attempts to do by using a conversation analysis tool called ethnomethodology. In an experimental setting, subjects were videotaped reading and responding to a set of instructions. Their responses indicate that: readers will often choose to play a role different from the one embedded in a text, especially if the text role offends them in some way; readers with similar education and interest may display different reader roles, making these roles difficult to predict; and within a single reading, a reader may change roles frequently. The paper concludes by discussing the implications of the findings and the appropriateness of ethnomethodology for reader-role research     

Amoebapore homologs of Caenorhabditis elegans

It is shown that the Caenorhabditis elegans genome contains several distantly related members of the gene family of saposin-like proteins. The putative products of genes T07C4.4, T08A9.7A, T08A9.7B, T08A9.8, T08A9.9, T08A9.10 are similar to the amoebapores of Entamoeba histolytica, granulysin of cytotoxic T lymphocytes and a putative amoebapore-related protein of the liver fluke Fasciola hepatica inasmuch as they consist of only a single saposin-like domain and a secretory signal peptide. The saposin-like domain of protein T07C4.4, which is most closely related to NK-lysin and granulysin, has been expressed in Escherichia coli and the recombinant protein was shown to have a circular dichroism spectrum consistent with the helix bundle structure characteristic of saposin-like domains. Recombinant T07C4.4 protein was found to have antibacterial activity, suggesting that these amoebapore homologs may play a role in antibacterial mechanisms of C. elegans.     

The detection of oligonucleotide N3'-->P5' phosphoramidate/RNA duplexes with capillary gel electrophoresis

Oligonucleotide N3'-->P5' phosphoramidates (3'-phosphoramidates) are DNA analogs that are presently under investigation as potential therapeutic agents. These compounds may also hold promise as a diagnostic tool. Here, we describe a rapid method for the analysis of single-stranded RNA fragments utilizing 3'-phosphoramidate oligonucleotides as probes in conjunction with capillary gel electrophoresis (CGE). 3'-Phosphoramidate 9-mers were mixed with complimentary RNA, and CGE was used to monitor duplex formation. Complimentary strands of RNA and 3'-phosphoramidate formed duplexes that gave unique relative mobilities based on an internal standard. The ability of CGE to discriminate between perfect duplexes and duplexes that contain a base mismatch was also investigated. However, the primary focus of this work was to determine CGE's ability to detect the presence of the 3'-phosphoramidates/RNA duplex under routine electrophoretic running conditions. Polyacrylamide gel electrophoresis analysis was utilized to verify duplex formation.     

Laser interferometer with fine-focused beams to monitor the spatial position of an object

Analogies with interferometers using a light source with low temporal coherence are used to analyze the principles of the construction of laser interferometers with averaging over the photodetector aperture, whose sensitivity to the position of an object being monitored at the maximum of the output signal is as good as that of low-coherence interferometry and tomography. Pis’ma Zh. Tekh. Fiz. 24, 19–24 (February 26, 1998)     

Trp82 and Tyr332 are involved in two quaternary ammonium binding domains of human butyrylcholinesterase as revealed by photoaffinity labeling with [3H]DDF

Purified butyrylcholinesterase (BuChE) was photolabeled by [3H]-p-N, N-dimethylamino benzene diazonium ([3H]DDF) to identify the quaternary ammonium binding sites on this protein [Ehret-Sabatier, L. , Schalk, I., Goeldner, M., and Hirth, C. (1992) Eur. J. Biochem. 203, 475-481]. The covalent photoincorporation occurs with a stoichiometry of one mole of probe per mole of inactivated site and could be fully prevented by several cholinergic inhibitors such as tacrine or tetramethylammonium. After complete deglycosylation of the enzyme using N-glycosidase F, the alkylated protein was trypsinolyzed and the digests were analyzed by HPLC coupled to ES-MS. A direct comparison of tryptic fragments from labeled and unlabeled BuChE allowed us to identify the tryptic peptide Tyr61-Lys103 as carrying the probe. Purification of the labeled peptides by anion-exchange chromatography gave a major radioactive peak which was further fractionated by reversed-phase HPLC leading to three, well-resolved, radioactive peaks. Microsequencing revealed that two of these peaks contained an overlapping sequence starting at Tyr61, while the third peak contained a sequence extending from Thr315. Radioactive signals could be unambiguously attributed to positions corresponding to residues Trp82 and Tyr332. This labeling study establishes the existence of two different binding domains for quaternary ammonium in BuChE and exemplifies additional cation/pi interactions in cholinergic proteins. This work strongly supports the existence of a peripheral anionic site in BuChE, implying residue Tyr332 as a key element.