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.

We present a kinetic model for the sequence-dependent motion of RNA polymerase (RNAP) during transcription elongation. For each NTP incorporation, RNAP has a net forward translocation of one base-pair along the DNA template. However, this process may involve the exploration of back-tracked and forward-tracked translocation modes. In our model, the kinetic rates for the reaction pathway, calculated based on the stabilities of the transcription elongation complex (TEC), necessarily lead to sequence-dependent NTP incorporation rates.

Studies of insect flight have focused on aerodynamic lift, both in quasi-steady and unsteady regimes. This is partly influenced by the choice of hovering motions along a horizontal stroke plane, where aerodynamic drag makes no contribution to the vertical force. In contrast, some of the best hoverers - dragonflies and hoverflies - employ inclined stroke planes, where the drag in the down- and upstrokes does not cancel each other. Here, computation of an idealized dragonfly wing motion shows that a dragonfly uses drag to support about three quarters of its weight.

The shear plasticity of charge density waves (CDW) in NbSe3 single crystals with cross sections having a single microfabricated thickness step was investigated. Thickness-dependent CDW pinning was found to be responsible for the origin of shear stresses along the step. The CDW depinned elastically at the volume average depinning field for small thickness differences, whereas the weak pinned side depinned first through plastic shear, for large thickness differences. Shear plasticity contributed substantial dissipation above the depinning field in large thickness differences.