Arts & Sciences
Understanding the interactions among polyelectrolytes by using inorganic polyoxometalate molecular clusters as model systems
Nanometer-scaled polyoxometalate (POM) molecular clusters exist as hydrophilic, highly soluble macroions in water and other polar solvents. Very interestingly, they do not stay as discrete ions even in very dilute solutions. Instead, we find that they universally tend to self-assemble into highly stable, monodispersed, hollow, spherical, single-layered shell-like structures (we call them “blackberries”), by using laser light scattering, TEM, SEM and SAXS studies.
The blackberry size can be accurately tuned by adjusting solution content and/or solution pH. The transitions between discrete macroions to blackberry structures, and between blackberries with different sizes, can be also achieved. The driving forces of the blackberry formation are not due to hydrophobic interaction, van der Waals forces or chemical interactions. Instead, we believe that the counter-ion effects and hydrogen bonds are critical. Synchrotron SAXS studies clearly show the radial distribution of small cations around large POM anions and the relation between the counter-ion association and the blackberry formation. › Continue reading
Novel Splicing Generates Unique mRNA Isoforms from the Ribosomal Protein L22-like Gene in Drosophila melanogaster
Alternative splicing contributes to protein diversity by creating multiple mRNAs from a single gene that may encode functionally-distinct protein variants. Little is known about alternative splicing of ribosomal protein (rp) genes as a possible mechanism to generate ribosome diversity itself. As complex organelles, eukaryotic ribosomes contain several RNAs and ~80 rp components, each represented as a single copy. Paralogous proteins exist in several rp families and their presence may indicate functional redundancy or specialized functions. Incorporation of specialized paralogs into ribosomes could generate functionally-distinct classes of ribosomes, possibly dedicated to translation of specific mRNAs or to differential regulation of protein synthesis within cells/tissues/developmental stages. Drosophila rp L23a and L22 contain a unique N-terminal extension (of unknown function) with homology to histone H1 (Koyama et al., 1999). Gene expression profiling revealed a novel transcript called “L22-like” that displays an embryonic gonad-specific expression pattern by in situ hybridization compared to a constitutive pattern for L22 mRNA (Shigenobu et al., 2006; Kai et al., 2005). Noticeably, this paralog contains a similar histone H1- like domain, and if expressed at the protein level and assembled into ribosomes, could define a unique class of ribosomes within the fly gonad. Whether or not L22-like and L22 are interchangeable within the ribosome is unknown. Further insight into L22-like expression was determined by RT-PCR analysis using RNA from embryo, larval, and adult stages, as well as from S2 cells. Full-length L22-like mRNAs were detected at all stages. Surprisingly, lower molecular weight (MW) amplicons were also present. Cloning and sequencing revealed that the lower MW amplicons (designated “L22-like short”) are mRNA variants, in which non-canonical splice sites within an exon are used for RNA splicing to remove a previously unidentified intron. Northern blot analysis confirmed the presence of multiple L22-like mRNAs. Preliminary Western blot analyses show protein products of the predicted size for both L22-like and L22-like short isoforms in S2 cells. Whether or not the L22-like isoforms are incorporated into ribosomes is yet to be determined. Collectively, these experiments provide a foundation for understanding developmental regulation of L22-like rp gene expression and how rp variants may contribute to ribosome diversity within cells.
Retention and Release of Cryptosporidium parvum Oocysts by Experimental Biofilms Composed of Natural Stream Microbial Communities
Cryptosporidium is a group of waterborne protozoan parasites that cause significant gastrointestinal disease in humans. The potential exists for these parasites to accumulate in stream or pipe surface biofilms and to be subsequently released to contaminate the water supply. Natural microbial assemblages were collected from three streams for three seasons (fall, winter, and spring) and used to grow biofilms in laboratory microcosms. These biofilms were then exposed to Cryptosporidium parvum oocysts via continuous inflow to determine daily influx, efflux, and biofilm retention and sloughing. Daily oocyst counts showed that oocysts attached to the biofilm quickly (within hours) and released slowly (within days). In these experiments, at least 40% of the oocysts added to the system attached to the biofilm in the first 72 hours, and at least 20% of the oocysts remained attached to the biofilm beyond 72 hours after the oocyst supply was removed. Although variation across site and season exists, likely as a result of variable microbial communities, all biofilms captured at least 40% of the oocysts and retained some of those oocysts for at least five days. The biofilm attachment and detachment dynamics of C. parvum oocysts have important implications for public health and suggest that biofilm monitoring should be included in routine water supply monitoring.
Cannibalism, Titus Andronicus and the Re-Making of Rome
Reading cannibalism as a subversively benevolent sort of violence in Shakespeare’s Titus Andronicus—as incorporation and, potentially, a drive toward wholeness with other individuals, with the earth, and with primordial origins—can break down boundaries between bodies and individuals and re-vision horrific violence as a healing enterprise on a psycho-cultural level. Though it is difficult to see violent acts as positive, I argue that symbolism, representation and language in the text can lend themselves to this interpretation. Cannibalistic violence is a rage turned both outward and inward, but in this turning inward there is a reconstitution and redemption inherent in the act. How might we re-vision the ending of the play by thinking about cannibalism in this alternative way? What then might we learn about the evolution of the cycle of violence and the ways in which extreme violent acts inflame or end it? Cannibalism at its very core incorporates rather than deconstructs. Collapsing the boundaries between self and other, and between self and earth might some way be seen as a movement toward ending the cycle of violence, but only after we have seen the most horrific form we can imagine.