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Research has been conducted on the tertiary structure of 16S rRNA within 30S ribosomal subunits. The localization of 16S rRNA regions proximal to the decoding region has been carried out.

A study was conducted on 16S ribosomal RNA proximal to transfer RNA bound at the P-site of Escherichia coli ribosomes. The results indicate that the sites are protected from chemical modification by tRNA binding and are cross-linked to P-site-bound tRNA. Use of cleavage reagent analysis reveals the existence of additional regions of rRNA that may be proximal to bound tRNA. The findings also reveal an extended set of nucleotides in the 16S rRNA that may interact with tRNA while bound at the P-site.

The mechanism by which the the cleavage of 16S ribosomal RNA controls the position of the messenger RNA was determined through utilization of mRNA modified with phenanthroline by covalent bonding. Results have shown that phenanthroline cleaved rRNA in the presence of Cu2+ and reducing agent in the regions proximal to the mRNA. Regions of the rRNA helix were specifically cleaved by phenanthroline covalently to the A-site of a strategically positioned mRNA.

The exit (E) site of the Escherichia coli ribosome was investigated using DNA probes complementary to single-stranded regions of 23S ribosomal RNA. The results provide evidence for tRNA/rRNA interaction at or near the E site of the E. coli ribosome and suggest that a conformational change occurs in the E site when deacylated tRNA is bound to the peptidyl (P) site. It was shown that the presence of deacylated tRNA in the P site makes the E site more available for probe hybridization.

A study was conducted on ribosomal RNA (rRNA) conformation in Escherichia coli ribosome. 16S rRNA nucleotides 1397 to 1404 were found to have unusually accesible sequences in both active and inactive subunits while nucleotides 919-924 were partially available for activation in active and more in inactive subunits. Nucleotides 1534-1542 were found to be freely accesible in active but partially accesible in inactive subunits while nucleotides 1490-1505 and 1530-1533 were found to be inaccesible in both subunits. The results inducate a radical conformational change accompanying subunit activation.

Despite the key role microalgae play in introducing toxicants into aquatic food webs, little is known about the effects of environmental factors on metal accumulation by these primary producers. Environmental factors such as light and nutrients alter growth rates and may consequently influence metal concentrations in microalgae through growth dilution. Laboratory experiments suggested that metal uptake and elimination by microalgal biofilms were gradual enough to enable dilution of metals within the biofilms by photosynthetically accrued carbon, and a simple kinetic model of metal accumulation predicted significant variation in metal content due to growth dilution over the natural range of microalgal growth rates. The ratio of metal uptake to carbon uptake by microalgal biofilms decreased exponentially with increasing light in short-term laboratory experiments because photosynthesis was much more sensitive to a light gradient than was metal uptake. The effect of light on biofilm metal concentrations was confirmed in situ with a long-term experiment in which experimental shading of biofilms in a metal-contaminated stream decreased biofilm growth rates and caused a 3&yimes; increase in biofilm concentrations of twelve metals, including methylmercury. Slow growth at the primary producer level is a likely contributor to higher biotic metal concentrations in shaded, oligotrophic, or cold ecosystems. [ABSTRACT FROM AUTHOR]