Homeotic transformation induced by protein transduction

One of the most fundamental features of living organisms is that cells are separated from their external environment by a thin, but highly complex plasma membrane constituted of a lipid bilayer. Although, the lipid bilayer is only a few nanometers in width, it is impermeable to most molecules apart from small hydrophobic ones. The ability of small molecules to diffuse through a lipid bilayer is related to their lipid solubility. Hydrophilic macromolecular Antennapedia homeodomain peptide has been shown to be able to translocate from extracellular space into the cytoplasm of cells in a receptor-independent manner. Its third α-helix domain, designated as “Penetratin”, was proposed to be the functional transduction domain that is responsible for the translocation, and it is widely used for intracellular delivery of various exogenous proteins. Although Penetratin has been regarded to be the only element conferring the capacity of its parent polypeptide to penetrate through the plasma membrane, we found that the complete Antennapedia homeodomain exhibits an appreciably higher level of translocation efficiency as compared to Penetratin. Pharmacological analysis demonstrated that macropinocytic endocytosis plays a significant role underlying the process of the homeodomain internalization, and this is consistent with the observation that internalized polypeptide co-localizes with a fluid phase dye. Our studies identify macropinocytosis as a major mechanism by which Antennapedia homeodomain obtains the access to the interior of cells. In the process of macropinocytosis, signaling from the plasma membrane is required for actin remodeling to generate mechanical deformation forces; the interaction between positively charged Antennapedia homeodomain and negatively charged extracellular heparan sulfate could trigger the signaling cascade for fluid phase endocytosis. This would presumably explain why positively charged peptides, polymers, and liposomes are able to penetrate cells. As a fluid phase macropinocytosis provides cells with a way to non-selectively internalize large quantities of solute, it represents an effective means for drug delivery into cells. Both of “Penetratin” and Antennapedia homeodomain exploit macropinocytosis to a certain extent, the comparison between them may advance our understanding of the mechanisms triggering macropinocytotic endocytosis

Assessing the effect of organic residue quality on active decomposing fungi in a tropical Vertisol using 15N-DNA stable isotope probing

15N-DNA stable isotope probing (15N-DNA-SIP) combined with 18S rRNA gene-based community analysis was used to identify active fungi involved in decomposition of 15N-labeled maize and soybean litter in a tropical Vertisol. Phylogenetic analysis of 15N-labeled DNA subjected to 18S rRNA gene-based community fingerprinting showed that organic residue quality promoted either slow (i.e. Penicillium sp., Aspergillus sp.) or fast growing (i.e. Fusarium sp., Mortierella sp.) fungal decomposers in soils treated with maize or soybean residues, respectively, whereas Chaetomium sp. were found as dominant decomposers in both residue treatments. Therefore, we have clear evidence that specific members of the fungal community used 15N derived from the two different organic resources for growth and stimulated early decomposition of maize or soybean decomposition. In conclusion, our study showed that 15N-DNA-SIP-based community analyses cannot only follow the flow of N from organic resources into bacteria, but also into the actively decomposing fungal communities of soils

Microwave and Millimeter Wave Techniques

Contains reports on three research projects.Joint Services Electronics Program (Contract DAAB07-75-C-1346