Marine Surfaces and the Expression of Specific Byssal Adhesive Protein Variants in Mytilus.

Mytilus foot protein-3 (Mfp-3) is a highly polymorphic protein family located in the byssal adhesive plaques of blue mussels. Previous evidence suggested that the deposition of selected Mfp-3 variants might be influenced by the type of surface to which the mussel attaches; therefore, we undertook to rigorously investigate whether a correlation exists between surface type and Mfp-3 variants. Two hypotheses were tested in M. galloprovincialis and M. edulis. One hypothesis was that individual mussels deposit specific Mfp-3 variants on different surfaces. Laser desorption-ionization mass spectrometry was used to detect Mfp-3 variants on the underside of byssal adhesive plaques. The other hypothesis was that the transcription of specific Mfp-3s is induced by different surfaces. This was measured by using denaturing gradient gel electrophoresis to separate closely related amplified complementary DNAs among individual mussels attached to stainless steel, glass, or polyethylene surfaces. Band stabs of several Mfp-3 cDNAs were sequenced. The results clearly showed that individual mussels secreted a similar suite of Mfp-3 variants onto glass, plastic, and steel. Likewise, the expression of Mfp-3 cDNA transcripts in individual mussels revealed no clear correlation between messenger RNA expression and the type of surface. Thus, the expression and secretion of specific Mfp-3 variants do not appear to be surface-induced. These results underscore the importance of following individual mussels rather than populations in surface studies.

Equatorial X-ray Emissions: Implications for Jupiter's High Exospheric Temperatures

Observations with the High Resolution Imager on the Rontgensatellit reveal x-ray emissions from Jupiter's equatorial latitudes. The observed emissions probably result from the precipitation of energetic (>300 kiloelectron volts per atomic mass unit) sulfur and oxygen ions out of Jupiter's inner radiation belt. Model calculations of the energy deposition by such heavy ion precipitation and of the resulting atmospheric heating rates indicate that this energy source can contribute to the high exospheric temperatures(>800 kelvin at 0.01 microbar) measured by the Galileo probe's Atmospheric Structure Instrument. Low-latitude energetic particle precipitation must therefore be considered, in addition to other proposed mechanisms such as gravity waves and soft electron precipitation, as an important source of heat for Jupiter's thermosphere.