Different conformations of nascent peptides on ribosomes

The length at which the N terminus of nascent proteins becomes available to antibodies during their synthesis on ribosomes was determined. Three different proteins, bovine rhodanese, bacterial chloramphenicol acetyltransferase and MS2 coat protein, were synthesized with coumarin at their N terminus in a cell-free system derived from Escherichia coli. A derivative of coumarin was cotranslationally incorporated as N-coumarin-methionine at the N terminus of polypeptides. The interaction of specific anti-coumarin antibodies with this N-terminal coumarin of ribosome-bound nascent peptides was examined. The results indicate that short nascent peptides of each of the three proteins are unreactive, that the length at which they become accessible to the antibodies is different for the three proteins, and that longer peptides differ in their reactivity. It is suggested that these differences are due to differences in the conformation acquired by the peptides as they are synthesized on the ribosomes.     

Generation of Liapunov functions for time-varying nonlinear systems

A procedure for the generation of Liapunov functions for time-varying nonlinear systems is described. A composite differential one-form is derived from the basic system equations. A line integral of the one-form, withtheld constant, produces the candidate for a Liapunov function. An example is included.     

Pipeline Reconfigurable FPGAs

While reconfigurable computing promises to deliver incomparable performance, it is still a marginal technology due to the high cost of developing and upgrading applications. Hardware virtualization can be used to significantly reduce both these costs. In this paper we describe the benefits of hardware virtualization, and show how it can be achieved using the technique of pipeline reconfiguration. The result is PipeRench, an architecture that supports robust compilation and provides forward compatibility. Our preliminary performance analysis on PipeRench predicts that it will outperform commercial FPGAs and DSPs in both overall performance and in performance normalized for silicon area over a broad range of problem sizes.     

Sorption of Scandium from Sulfuric–Chloride Solutions by Activated Carbons

Sorption of scandium by activated carbons of VSK, DAS, and PFT brands of different origin (coconut shell, anthracite, and thermosetting-plastic waste, respectively) from sulfuric–chloride solutions (pH 2) simulating the composition of solutions for the underground leaching of complex ores is studied in batch conditions. It is established that the sorption of scandium by carbons of DAS and VSK brands proceeds with the highest distribution coefficients (133 and 45.8 cm3/g, respectively). Herewith, the sorption of scandium by DAS carbon is also characterized by a large volume coefficient (116 $${{{\text{cm}}_{{{\text{sln}}}}^{{\text{3}}}} \mathord{\left/ {\vphantom {{{\text{cm}}_{{{\text{sln}}}}^{{\text{3}}}} {{\text{cm}}_{{{\text{carb}}}}^{{\text{3}}}}}} \right. \kern-0em} {{\text{cm}}_{{{\text{carb}}}}^{{\text{3}}}}}$$). Sorption isotherms of scandium by these carbons are linear and described by the Henry equation with constants 133 ± 21 and 46 ± 7 cm3/g, respectively. The integral kinetic curves of sorption of scandium are found by the method of the limited volume of the solution, and their linearization according to the kinetic models of the pseudo-first and pseudo-second order, the Elovich model, and the Weber–Morris intraparticle diffusion model evidences that the sorption kinetics of scandium by VSK carbon with a higher correlation coefficient (0.999) is described using the pseudo-second-order model. Processing the kinetic data on the sorption of scandium by DAS carbon showed that, when using all models, the correlation coefficient is low (<0.939) and the highest value is observed when applying the intraparticle diffusion model. It is assumed that the sorption of scandium occurs in the mixed diffusion region. The possibility of eluting scandium from VSK and DAS carbons by the sodium carbonate solution (10%) is studied under the batch conditions and the degree of desorption of scandium for two elution steps is 84.0 and 90.4%, respectively.     

Interaction of finger representation in the human first somatosensory cortex: a neuromagnetic study

The authors studied immunologic features of saliva in 1714 workers exposed to vibration and other occupational hazards in microbiologic, chemical enterprises. The examinees demonstrated lower activity of lysozyme and concentrations of IgA, higher levels of IgG. Immunologic features of saliva was proved to have extreme diagnostic importance, therefore could be used to detect early signs of exposure to occupational hazards and to diagnose pathologic conditions caused by those hazards.     

Differential use of the betaL subunit of the type I interferon (IFN) receptor determines signaling specificity for IFNalpha2 and IFNbeta

The signaling specificity for cytokines that have common receptor subunits is achieved by the presence of additional cytokine-specific receptor components. In the type I interferon (IFN) family, all 14 subtypes of IFNalpha, IFNbeta, and IFNomega bind to the same alpha and betaL subunits of the type I IFN-R, yet differences in signaling and biological effects exist among them. Our data demonstrate that IFNalpha2 and IFNbeta utilize different regions of the betaL subunit for signaling. Thus, in contrast to other cytokine systems, signal diversity in the type I IFN system can be accomplished within the same receptor complex by utilizing different regions of the same receptor subunits.     

Differential affinity cross-linking of phosphorylase kinase conformers by the geometric isomers of phenylenedimaleimide

Phosphorylase b kinase (PbK) from skeletal muscle is a highly regulated oligomer consisting of four copies of four distinct subunits (alphabetagamma)delta4. The gamma subunit is catalytic, and the remaining subunits are regulatory. To characterize effector-induced changes in the quaternary structure of the enzyme, we utilized the ortho-, meta, and para-isomers of phenylenedimaleimide (PDM), which in addition to having different geometries, also vary 2.5-fold in their cross-linking spans. Even at concentrations equivalent to the alphabetagammadelta protomers of PbK, all three isomers caused specific, rapid, and extensive cross-linking of the holoenzyme to form primarily alphabeta dimers, plus smaller amounts of betagammagamma and alphagammagamma trimers. The formation of these three conjugates was nearly totally inhibited by a 10-fold molar excess over PDM of N-(o- and p-tolyl)succinimide, which are chemically inert structural analogs of PDM. This inhibition suggests that PbK has binding sites for PDM and that PDM acts as an affinity cross-linker in binding to these sites prior to forming cross-linked conjugates. The largest effect on cross-linking in progressing from o- to p-PDM was on the alphagammagamma trimer, which is preferentially formed by the p-isomer. Activation of the enzyme by either phosphorylation or the allosteric activators ADP and GDP resulted in large increases in the amount of alphagammagamma formed, small increases in betagammagamma, and little change in alphabeta. When cross-linked in the presence of the reversibly activating nucleoside diphosphates, PbK remained activated after their removal, indicating that cross-linking had locked it in the active conformation. Our results provide direct evidence for perturbations in the interactions of the catalytic gamma subunit with the regulatory alpha and beta subunits upon activation of PbK.