Over the past few years, it has become increasingly apparent that double-stranded RNA (dsRNA) plays a far greater role in the life cycle of a cell than previously expected. Numerous proteins, including helicases, polymerases, and nucleases interact specifically with the double helix of dsRNA. To understand the detailed nature of these dsRNA-protein interactions, the (bio)chemical, electrostatic, and mechanical properties of dsRNA need to be fully characterized. We present measurements of the persistence length of dsRNA using two different single-molecule techniques: magnetic tweezers and atomic force microscopy. We deduce a mean persistence length for long dsRNA molecules of 63.8 +/- 0.7 nm from force-extension measurements with the magnetic tweezers. We present atomic force microscopy images of dsRNA and demonstrate a new method for analyzing these, which yields an independent, yet consistent value of 62 +/- 2 nm for the persistence length. The introduction of these single-molecule techniques for dsRNA analysis opens the way for real-time, quantitative analysis of dsRNA-protein interactions.

Increased binding of IgM to donor platelets was detected in serum of a patient demonstrating the phenomenon of pseudothrombocytopenia. The elevated IgM binding was dependent on EDTA concentration and temperature, and could not be demonstrated when platelets of patients with Glanzmann's disease were used. Immunoblotting and crossed immunoelectrophoresis showed that the IgM antibody reacted with platelet glycoprotein GP IIb. Evidence is presented that the antigenic binding site on GP IIb is made accessible to the antibody by means of the effect of EDTA on the Ca2+ dependent GP IIb/IIIa complex.

The effects of nitrous oxide-induced cobalamin inactivation on homocysteine and folate metabolism have been investigated. Plasma levels of cobalamin, folate, homocysteine, and methionine were determined in 40 patients before and after operation under nitrous oxide anesthesia (range of exposure time, 70 to 720 minutes). Twelve patients anesthetized with total intravenous anesthesia served as control subjects (range of exposure time, 115 to 600 minutes). Postoperative plasma levels of folate and homocysteine increased (p less than 0.001) up to 220% and 310%, respectively, in nitrous oxide-exposed patients, whereas plasma levels of methionine decreased (p less than 0.025). Response occurred after 75 minutes of nitrous oxide exposure. The percentage increase of plasma folate and homocysteine correlated significantly with exposure time (p less than 0.025 and p less than 0.0001, respectively). In eight patients receiving nitrous oxide anesthesia plasma homocysteine levels had not returned to preoperative levels within 1 week (p less than 0.01). Urinary excretion of folate and homocysteine increased during and after nitrous oxide exposure (p less than 0.01 and p less than 0.002, respectively) and correlated with exposure time (p less than 0.01 and p less than 0.005, respectively). It can be concluded that disturbance of homocysteine and folate metabolism by nitrous oxide develops with little delay and return to normal levels requires several days. Elevation of plasma homocysteine levels may therefore be used for monitoring nitrous oxide-induced cobalamin inactivation.