To study the cleavage mechanism of bacterial Nase P RNA, we have synthesized precursor tRNA substrates carrying a single Rp- or Sp-phosphorothioate modification at the RNase P cleavage site. Both the Sp- and the Rp-diastereomer reduced the rate of processing by Escherichia coli RNase P RNA at least 1000-fold under conditions where the chemical step is rate-limiting. The Rp-modification had no e...

Prokaryotes protect their genomes from foreign DNA with a diversity of defence mechanisms, including a widespread restriction-modification (R-M) system involving phosphorothioate (PT) modification of the DNA backbone. Unlike classical R-M systems, highly partial PT modification of consensus motifs in bacterial genomes suggests an unusual mechanism of PT-dependent restriction. In Salmonella ente...

The peptide, MKATKLVLGAVILGSTLLAGCSSN, corresponding to the N-terminal24 amino acids of Braun’s prolipoprotein, was used to study the lipid modification of prolipoprotein in Escherichia coli by measuring the rate of incorporation of either [2-SH]glycerol or [9,10SH]palmitate from the corresponding labeled phosphatidylglycerol into the peptide. Using E. coli strains containing varying levels of ...

in this paper, dynamical behavior of the delay mechanism of a special projectile controller is studied, using 3d finite element simulation. the controller considered here is among of high-acceleration mechanical controllers. due to high linear and angular accelerations of the projectile and also explosion risk, experimental investigation is very limited and almost impossible. so, numerical simu...

Startle modification is a robust phenomenon that has been used as a tool in the research of emotion and motivation. In a picture viewing paradigm, valence of affective pictures modulates startle magnitude. There is a debate on whether emotional or attentional processes are the mechanism of startle modification. The present study sought to address this question by investigating the individual di...

A quantum mechanical model on histone modification is proposed. Along with the methyl / acetate or other groups bound to the modified residues the torsion angles of the nearby histone chain are supposed to participate in the quantum transition cooperatively. The transition rate W is calculated based on the non-radiative quantum transition theory in adiabatic approximation. By using W’s the reac...

Chemical modification of biological molecules is a general mechanism for cellular regulation. A quantitative approach has been developed to measure the extent of modification on HS (heparan sulphates). Sulphation on HS by sulphotransferases leads to variable sulphation levels, which allows cells to tune their affinities to various extracellular proteins, including growth factors. With stable is...

The type IX secretion system (T9SS) of Porphyromonas gingivalis secretes proteins possessing a conserved C-terminal domain (CTD) to the cell surface. The C-terminal signal is essential for these proteins to translocate across the outer membrane via the T9SS. On the surface the CTD of these proteins is cleaved prior to extensive glycosylation. It is believed that the modification on these CTD pr...

A simple, inexpensive modification in the elevator mechanism of a liquid scintillation counter allows for radioimmunoassay tubes (12 X 75 mm) containing the antibody-bound radioligand to be counted directly, thereby obviating the need for counting vials and considerably decreasing the amount of fluor used. Furthermore, because assay and counting are all done in the same tube, the modification s...

Throughout all domains of life, nucleic acid-based epigenetic modification of DNA is established as a regulatory mechanism that can affect different processes ranging from the replicative mismatch repair to the transcriptional activity of genes. Modifications can be preserved during cell divisions and play important roles in development-with consequences of aberrant regulation of modification s...