Dendrimers are macromolecular, nanoscale objects that are widely recognized as precise, mathematically defined, covalent core-shell assemblies. As such, they are composed of quantized numbers of atoms, monomers, and terminal functional groups relative to the respective shell levels (generations) surrounding their cores. Dendrimers have been referred to as molecular-level analogs of atoms. This ...

Supramolecular protein assemblies are an emerging area within the chemical sciences, which combine the topological structures of the field of supramolecular chemistry and the state-of-the-art chemical biology approaches to unravel the formation and function of protein assemblies. Recent chemical and biological studies on natural multimeric protein structures, including fibers, rings, tubes, cat...

Since its inception in the mid-1990s, dynamic combinatorial chemistry (DCC), the chemistry of complex systems under thermodynamic control, has proved valuable in identifying unexpected molecules with remarkable binding properties and in providing effective synthetic routes to complex species. Essentially, in this approach, one designs the experiment rather than the molecule. DCC has also provid...

RPA is a single-stranded DNA binding protein that physically associates with the BLM complex. RPA stimulates BLM helicase activity as well as the double Holliday junction dissolution activity of the BLM-topoisomerase IIIα complex. We investigated the effect of RPA on the ssDNA decatenase activity of topoisomerase IIIα. We found that RPA and other ssDNA binding proteins inhibit decatenation by t...

In Escherichia coli, complete unlinking of newly replicated sister chromosomes is required to ensure their proper segregation at cell division. Whereas replication links are removed primarily by topoisomerase IV, XerC/XerD-dif site-specific recombination can mediate sister chromosome unlinking in Topoisomerase IV-deficient cells. This reaction is activated at the division septum by the DNA tran...

Chromosomal and plasmid DNA molecules in bacterial cells are maintained under torsional tension and are therefore supercoiled. With the exception of extreme thermophiles, supercoiling has a negative sign, which means that the torsional tension diminishes the DNA helicity and facilitates strand separation. In consequence, negative supercoiling aids such processes as DNA replication or transcript...

Members of the protozoan order Kinetoplastida (Honigberg et al., 1964), which includes the genera Trypanosoma, Leishmania, and Crithidia, are characterized by the presence of a body known as a kinetoplast. The kinetoplast is a modified region of a mitochondrion (Meyer et al., 1958; Steinert, 1960; Clark and Wallace, 1960) which contains so much DNA that it can be detected by Feulgen staining (B...