Visual information processing using bacteriorhodopsin-based complex LB films.

Image extraction and visual information processing using bacteriorhodopsin (bR)-based bioelectronic devices is presented. Image extraction was achieved using a photoreceptor consisting of bR and spiropyran films. The undesired signals from the photoreceptor were automatically eliminated from the whole signal by spiropyran films acting as an optical noise filter that increases the target signal to an undesired signal ratio. For the information processing, the photoreceptor consisting of bR and lipid films deposited with different configurations was used and the target signals were processed to achieve the pattern recognition. The pattern recognition was based on not only the response variability of bacteriorhodopsin, induced by different film configurations, but also on the initial learning process. The input patterns were predicted by simple calculation with the known signals through the initial learning process.

Participation of the 3'-CCA of tRNA in the binding of catalytic Mg2+ ions by ribonuclease P.

Ribonuclease P (RNase P) contains a catalytic RNA that cleaves precursor tRNA (pre-tRNA) to form the mature 5'-end of tRNA. Previous kinetic analyses with mutant pre-tRNAs indicated that both C residues of the invariant 3'-terminal CCA form specific interactions with RNase P RNA that contribute to the energetics of substrate binding (1, 2). In the present study, we have used single-turnover kinetic analysis to investigate whether specific changes in the 3'-terminal CCA influence the rate of the chemical step through which enzyme-bound substrate is converted to product (k2). At optimal ionic strength (1.0 M NH4Cl, 25 mM MgCl2), deletion or substitution of the 3'-proximal C residue (CCA) reduced the rate of the chemical step of cleavage (k2) by 60-fold. Similar changes to the 5'-proximal C residue (CCA) or the 3'-terminal A residue (CCA) reduced k2 only a few fold. Each mutant substrate exhibited weakened affinity for Mg2+, as measured by Hill plots, and the severity of these defects correlated with the observed reductions in k2. Furthermore, elevated concentrations of Mg2+ partially, but not completely, suppress the k2 defects caused by deletion or substitution of the 3'-proximal C residue. We conclude that the 3'-CCA of pre-tRNA, particularly the 3'-proximal C residue, comprises part of the catalytic pocket formed in the pre-tRNA-RNase P complex and participates in the binding of Mg2+ ions that are essential for catalysis by RNase P RNA.

Potentiometric properties of ion-selective electrode membranes based on segmented polyether urethane matrices.

Potentiometric responses of polyurethane (PU)-based membranes containing valinomycin and varying amounts of plasticizer (DOA) and/or lipophilic additive (KTpClPB) were examined as a function of soft segment [poly(tetramethylene ether glycol)] contents in aromatic diisocyanate-based PU matrices. Upon increasing the weight percentages (w(soft)) of soft segments, which in part behave like a built-in plasticizer, providing the matrices with rubbery structure (glass transition temperature below -58 °C), the amounts of DOA and/or KTpClPB necessary to result in near-Nerntian response (e.g., slope > 50 mV/decade) to potassium were substantially lowered. The apparent effect of adding plasticizer to PU-based membranes was comparable to that resulting from an increase of free carrier concentration in normal PVC-based membranes. Owing to the chemical interaction between mobile anionic sites and urethane chains, plasticizer-free PU membranes could be prepared with the PU matrices with high soft segment contents (w(soft) ≥ 60 wt %). PUs composed of 60 ≤ w(soft) < 80 wt % were recommended as the matrix for fabricating ISE membranes with no or low plasticizer content.

One-component room temperature vulcanizing-type silicone rubber-based calcium-selective electrodes.

New calcium-selective membranes for all-solid-state ion sensors are developed with a highly adhesive one-component room temperature vulcanizing-type silicone rubber (RTV-1-type SR) matrix. The membranes are formulated with 21.6 wt % bis(2-ethylhexyl) adipate, 0.3 wt % tetradodecylammonium tetrakis(p-chlorophenyl)borate (ETH 500), 0.1 wt % potassium tetrakis(p-chlorophenyl)borate, and 0.8 wt % calcium-selective neutral carrier ETH 129 or ETH 1001. Plasticizer added to the RTV-1-type SR matrix not only decreases the bulk membrane resistance but also increases the solubility of electroactive components incorporated in the membrane without significantly deteriorating its adhesive strength. It is found that the lipophilic salt ETH 500 remarkably enhances the calcium selectivity of ETH 129 or ETH 1001 ligands in the SR matrix; the selectivity coefficients ([Formula: see text] by separate solution method, where j = Li(+), Na(+), K(+), or Mg(2+)) for the optimized membranes were below 10(-5). Potentiometric characteristics of planar-type Ag electrodes coated with optimized RTV-1-type SR membranes, e.g., response slope 29.0 ± 0.5 mV/decade, detection limit below 5.0 × 10(-7) M a(Ca)((2+)), and 2-3 mV of potential drift per day, were virtually the same as those of the corresponding poly(vinyl chloride) membrane-based conventional electrodes, but with greatly enhanced sensor-to-sensor reproducibility and lifetime (3-9 weeks).

Interaction of the 3'-end of tRNA with ribonuclease P RNA.

Ribonuclease P, which contains a catalytic RNA subunit, cleaves 5' precursor-specific sequences from pre-tRNAs. It was previously shown that the RNase P RNA optimally cleaves substrates which contain the mature, 3'-terminal CCA of tRNA. In order to determine the contributions of those individual 3'-terminal nucleotides to the interaction, pre-tRNAs that have CCA, only CC or C or are without CCA at the 3'-end were synthesized by run-off transcription, tested as substrates for cleavage by RNase P RNA and used in photoaffinity crosslinking experiments to examine contact sites in the ribozyme. In order to generalize the results, analyses were carried out using three different bacterial RNase P RNAs, from Escherichia coli, Bacillus subtilis and Thermotoga maritima. At optimal (Kcat/Km) ionic strength (1 M NH4+/25 mM Mg2+), Km increases incrementally 3- to 10-fold upon stepwise removal of each nucleotide from the 3'-end. At high ionic strength (2 M NH4+/50 mM Mg2+), which suppresses conformational effects, removal of the 3'-terminal A had little effect on Km, indicating that it is not a specific contact. Analysis of the deletion and substitution mutants indicated that the C residues act specially; their contribution to binding energy at high ionic strength (approximately 1 kcal/mol) is consistent with a non-Watson-Crick interaction, possibly irregular triple-strand formation with some component of the RNase P RNA. In agreement with previous studies, we find that the RNase P holoenzyme in vitro does not discriminate between tRNAs containing or lacking CCA. The structural elements of the three RNase P RNAs in proximity to the 3'-end of tRNA were examined by photoaffinity crosslinking. Photoagent-labeled tRNAs with 3'-terminal CCA, only CC or C, or lacking all these nucleotides were covalently conjugated to the three RNase P RNAs by irradiation and the sites of crosslinks were mapped by primer extension. The main crosslink sites are located in a highly conserved loop (probably an irregular helix) that is part of the core of the RNase P RNA secondary structure. The crosslinking results orient the CCA of tRNA with respect to that region of the RNase P RNA.

10Sa RNA, a small stable RNA of Escherichia coli, is functional.

The ssrA gene, coding for the metabolically stable 10Sa RNA, affects cell growth. A mutant in which the chromosomal 10Sa RNA gene is interrupted by a cat insert does not produce detectable levels of 10Sa RNA, and it grows more slowly than the parental strain.

Location of a gene (ssrA) for a small, stable RNA (10Sa RNA) in the Escherichia coli chromosome.

The gene for 10Sa RNA, which is a major small, stable RNA in Escherichia coli, is a unique gene in the E. coli chromosome. The 10Sa RNA gene (ssrA) has been located between 2,760 and 2,761 kilobases on the E. coli genome.

Sequential joint scintigraphy in rheumatoid arthritis.

In this sequential study joint scintigraphy was compared with clinical and röntgenological evaluation in 19 patients with rheumatoid arthritis. Scintigraphy sometimes preceded clinical and radiological abnormalities and scan results were independent of radiological findings showing no differences when large and small joints were compared. Scan findings in 2 patients with arthralgias only were negative, suggesting that arthritis was unlikely.