Mismatch repair (MMR) is initiated by MutS family proteins (MSH) that recognize DNA mismatches and recruit downstream repair factors. We used a single-molecule DNA-unzipping assay to probe interactions between S. cerevisiae MSH2-MSH6 and a variety of DNA mismatch substrates. This work revealed a high-specificity binding state of MSH proteins for mismatch DNA that was not observed in bulk assays and allowed us to measure the affinity of MSH2-MSH6 for mismatch DNA as well as its footprint on DNA surrounding the mismatch site.

We have investigated the electrical transport properties of insulating and metallic constrictions of dimensions 10nm-10μm in the charge-density wave (CDW) conductor NbSe 3. The constrictions are made in a variety of ways: focused ion beam, reactive ion etching through a resist mask, and in a mechanically-controlled break junction configuration. We find that the behaviour of the junctions is independent of the fabrication method, and, depending on the size of the constriction, that the low-temperature behaviour of the constrictions is metallic or insulating.

The motion of protein drops on crystallization media during routine handling is a major factor affecting the reproducibility of crystallization conditions. Drop stability can be enhanced by chemical patterning to more effectively pin the drop's contact line. As an example, a hydrophilic area is patterned on an initially flat hydrophobic glass slide. The drop remains confined to the hydrophilic area and the maximum drop size that remains stable when the slide is rotated to the vertical position increases.

In whisker-like samples of the quasi-1D conductor NbSe3, the presence of longitudinal steps causes shearing of the CDW, and leads to a loss of transverse correlations. We use a microdiffraction setup with a spatial resolution of 300 nm and an angular sensitivity of 5 indeg to image the resulting CDW contrast between thick and thin portions of the sample.

A modified capillary-growth method is described that has substantial advantages for standard and high-throughput protein crystal growth. Protein-containing drops are injected into vapor-permeable flexible X-ray-transparent polyester tubing. The protein concentration in the drop increases over time by water transport through the tubing wall at a rate controlled by the wall thickness and ambient relative humidity.

Hydrogel microstructures with micrometer-scale topography and controllable functionality have great potential for numerous nanobiotechnology applications including, for example, three-dimensional structures that exhibit controlled interactions with proteins and cells.

A new method for mounting protein crystals and other environmentally sensitive samples for room-temperature diffraction measurements is described. A crystal is retrieved using a microfabricated sample mount as recently reported, and the mount is inserted into a modified goniometer-compatible base. A transparent thin-wall polyester tube sealed at one end and filled with stabilizing liquid is then drawn over the crystal and sealed to the goniometer base.

The distinct contributions of histone tails and their acetylation to nucleosomal stability were examined by mechanical disruption of individual nucleosomes in a single chromatin fiber using an optical trap. Enzymatic removal of H2A/H2B tails primarily decreased the strength of histone-DNA interactions located ∼±36 bp from the dyad axis of symmetry (off-dyad strong interactions), whereas removal of the H3/H4 tails played a greater role in regulating the total amount of DNA bound.

The present experiments have established the potential of X-ray fluorescence to reveal traces of letters on abraded surfaces of ancient inscriptions, and to provide information about how the inscriptions were created. The small number of inscriptions examined here is not sufficient to establish this method's overall effectiveness and the factors relevant to its successful application. A proof-of-concept study on an inscription with unrecovered text is required.

The growth processes and defect structures of protein and virus crystals have been studied in situ by atomic force microscopy (AFM), X-ray diffraction topography, and high-resolution reciprocal space scanning. Molecular mechanisms of macromolecular crystallization were visualized and fundamental kinetic and thermodynamic parameters, which govern the crystallization process of a number of macromolecular crystals, have been determined.