Xenotransplantation of porcine tissues has the potential to treat a wide variety of major health problems including organ failure and diabetes. Balanced against the potential benefits of xenotransplantation, however, is the risk of human infection with a porcine microorganism. In particular, the transmission of porcine endogenous retrovirus (

Short RNA sequences exhibiting the activity of a target RNA cleavage are promising for cellular gene regulation and biosensor research, but the reaction media different from an aqueous solution may cause unanticipated molecular interactions and properties. In this study, we investigated the molecular crowding effects arising from steric crowding and altered solvent properties on the hammerhead ribozyme activity using water-soluble neutral cosolutes. Poly(ethylene glycol) (PEG) and other cosolutes at 20 wt % increased the RNA hydrolysis rate by a factor of 2.0-6.6 at 10 mM MgCl(2) and much more at lower MgCl(2) concentrations. Remarkably, although the cosolutes decreased the stability of the ribozyme stem helices, the thermal inactivation temperature of the ribozyme was significantly raised, resulting in a higher reaction rate, up to 270 times at 50 degrees C. More significantly, PEG decreased the metal ion concentration to perform the reaction even with a limiting Mg(2+) or Na(+) concentration, facilitated the catalytic turnover, and activated a catalytically less active ribozyme sequence. These observations agreed that the cosolutes acted as an osmolyte stabilizing the water-release reaction of the RNA tertiary folding but destabilizing the water-uptake reaction of Watson-Crick base pairing. The opposite cosolute effect on the stabilities of RNA secondary and tertiary structures, which is fundamentally different from a protein folding, suggests how RNA stabilizes a tertiary structure and enhances the catalytic activity in molecular crowding media.

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We isolated four kinds of cDNA clones of isotypes of catalytic subunits of protein phosphatase 1 (PP‐1) from rat liver and testis cDNA libraries. For the cloning, cDNA fragments of dis2ml and dis2m2, which encode mouse PP‐1 catalytic subunits, were used as probes. Two of the four isotypes were thought to be derived from the same gene and produced by alternative splicing. Based on the comparative study of their nucleotide and deduced amino acid sequences with those reported, these cDNA clones were named rat PP‐1α, PP‐1γ1, PP‐1γ2 and PP‐δ. The deduced amino acid sequences of these four cDNA clones showed about 90% identity. Their amino‐terminal regions were highly conserved, and their differences were mainly in the carboxy‐terminal regions. Furthermore, several amino acids located in the middle regions of the peptides were conserved in all the isotypes of the catalytic subunits of PP‐1, PP‐2A, PP‐2B and PP‐2C. These conserved regions are suggested to be the functional domains of the catalytic subunits of protein phosphatases. Rat hepatocellular carcinomas induced by a food mutagen, 2‐amino‐3,8‐dimethylimidazo[4,5‐f]quinoxaline showed increased expression of PP‐1α, but no increased expression of PP‐1γ1, PP‐1γ2 or PP‐1δ. Involvement of PP‐1α in hepatocarcinogenesis or in hepatic cell proliferation was suspected.

Historical and recent advances of lanthanide mononuclear complexes, polynuclear clusters, coordination polymers (CPs) and metal–organic frameworks (MOFs) with temperature-dependent luminescence are reviewed for future thermo-sensitive paints.