4 research outputs found
The influence of high speed swimsuits on the lactate curve test among competitive swimmers
departmental bulletin pape
A Fluorescent Split Aptamer for Visualizing RNA–RNA Assembly <i>In Vivo</i>
RNA–RNA
assembly governs key biological processes and is
a powerful tool for engineering synthetic genetic circuits. Characterizing
RNA assembly in living cells often involves monitoring fluorescent
reporter proteins, which are at best indirect measures of underlying
RNA–RNA hybridization events and are subject to additional
temporal and load constraints associated with translation and activation
of reporter proteins. In contrast, RNA aptamers that sequester small
molecule dyes and activate their fluorescence are increasingly utilized
in genetically encoded strategies to report on RNA-level events. Split-aptamer
systems have been rationally designed to generate signal upon hybridization
of two or more discrete RNA transcripts, but none directly function
when expressed <i>in vivo</i>. We reasoned that the improved
physiological properties of the Broccoli aptamer enable construction
of a split-aptamer system that could function in living cells. Here
we present the Split-Broccoli system, in which self-assembly is nucleated
by a thermostable, three-way junction RNA architecture and fluorescence
activation requires both strands. Functional assembly of the system
approximately follows second-order kinetics <i>in vitro</i> and improves when cotranscribed, rather than when assembled from
purified components. <i>Split-Broccoli</i> fluorescence
is digital <i>in vivo</i> and retains functional modularity
when fused to RNAs that regulate circuit function through RNA–RNA
hybridization, as demonstrated with an RNA Toehold switch. <i>Split-Broccoli</i> represents the first functional split-aptamer
system to operate <i>in vivo</i>. It offers a genetically
encoded and nondestructive platform to monitor and exploit RNA–RNA
hybridization, whether as an all-RNA, stand-alone AND gate or as a
tool for monitoring assembly of RNA–RNA hybrids
Selective Inactivation of Functional RNAs by Ribozyme-Catalyzed Covalent Modification
The
diverse functions of RNA provide numerous opportunities for
programming biological circuits. We describe a new strategy that uses
ribozyme K28min to covalently tag a specific nucleobase within an
RNA or DNA target strand to regulate and selectively inactivate those
nucleic acids. K28min variants with appropriately reprogrammed internal
guide sequences efficiently tagged multiple sites from an mRNA and
from aptamer and ribozyme targets. Upon covalent modification by the
corresponding K28min variant, an ATP-binding aptamer lost all affinity
for ATP, and the fluorogenic Mango aptamer lost its ability to activate
fluorescence of its dye ligand. Modifying a hammerhead ribozyme near
the catalytic core led to loss of almost all of its substrate-cleaving
activity, but modifying the same hammerhead ribozyme within a tertiary
stabilizing element that reduces magnesium dependence only impaired
substrate cleavage at low magnesium concentration. Thus, ribozyme-mediated
covalent modification can be used both to selectively inactivate and
to fine-tune the activities of targeted functional RNAs, analogous
to the effects of post-translational modifications of proteins. Ribozyme-catalyzed
covalent modification could therefore be developed to regulate nucleic
acids components of synthetic and natural circuits
Study on the perfection of in situ P-injection synthesis LEC-InP single crystals
Undoped, S-doped and Fe-doped InP crystals with diameter up to 4-inch have been pulled in drop 10 0 drop -direction under P-rich condition by a rapid P-injection in situ synthesis liquid encapsulated Czochralski (LEC) method. High speed photoluminescence mapping, etch-pit density (EPD) mapping and scanning electron microscopy have been used to characterize the samples of the single crystal ingots. Dislocations and electrical homogeneity of these samples are investigated and compared. By controlling the thermal field and the solid-liquid interface shape, 4-inch low-EPD InP single crystals have been successfully grown by the rapid P-injection synthesis LEC method. The EPD across the wafer of the ingots is less than 5 x 10(4) cm(-2). Cluster defects with a pore center are observed in the P-rich LEC grown InP ingots. These defects are distributed irregularly on a wafer and are surrounded by a high concentration of dislocations. The uniformity of the PL intensity across the wafer is influenced by these defects. (C) 2004 Elsevier B.V. All rights reserved