Fluorescence resonance energy transfer analysis of RNase L-catalyzed oligonucleotide cleavage.

A method is described for monitoring the cleavage of an oligoribonucleotide substrate by the 2-5A-dependent RNase L based on fluorescence resonance energy transfer (FRET). The oligoribonucleotide, rC11U2C7, was labeled covalently at its 5'-terminus with fluorescein and at its 3'-terminus with rhodamine to provide a substrate for RNase L. On cleavage, the fluorescence at 538 nm (with 485 nm excitation) increased by a factor of 2.

Using fluorescence resonance energy transfer (FRET) for measuring 2-5A analogues ability to activate RNase L.

The development of a method for measuring the ability of 2-5A analogues to activate the cleavage of an oligoribonucleotide substrate by RNase L is described. This method is based on fluorescence resonance energy transfer. The method is easily performed with 96-well plates, allowing for quantitative high-throughput analyses of 2-5A analogues under different reaction conditions.

Mean velocity and Reynolds stress measurements in the regurgitant jets of tilting disk heart valves in an artificial heart environment.

Laser Doppler velocimetry, with a high temporal resolution (1 ms time windows), was used to measure the flow field in two regions (major and minor orifices) near the aortic and mitral valves (Bjork Shiley monostrut Nos. 25 and 27, respectively) of the Penn State artificial heart. The motion of each valve was also investigated using a 1000 frame/s video camera in order to estimate the valve's closing velocity.