Modulation of frustration in folding by sequence permutation.

Folding of globular proteins can be envisioned as the contraction of a random coil unfolded state toward the native state on an energy surface rough with local minima trapping frustrated species. These substructures impede productive folding and can serve as nucleation sites for aggregation reactions. However, little is known about the relationship between frustration and its underlying sequence determinants.

Sub-millisecond time-resolved SAXS using a continuous-flow mixer and X-ray microbeam.

Small-angle X-ray scattering (SAXS) is a well established technique to probe the nanoscale structure and interactions in soft matter. It allows one to study the structure of native particles in near physiological environments and to analyze structural changes in response to variations in external conditions. The combination of microfluidics and SAXS provides a powerful tool to investigate dynamic processes on a molecular level with sub-millisecond time resolution.

L X-ray fluorescence cross sections experimentally determined for elements with 45 < Z < 50 at 9 keV.

Experimental determination of L fluorescence cross-sections for elements with 45 View Article and Find Full Text PDF

Phase-space analysis and experimental results for secondary focusing at X-ray beamlines.

Micro-focusing optical devices at synchrotron beamlines usually have a limited acceptance, but more flux can be intercepted if such optics are used to focus secondary sources created by the primary optics. Flux throughput can be maximized by placing the secondary focusing optics close to or exactly at the secondary source position. However, standard methods of beamline optics analysis, such as the lens equation or matching the mirror surface to an ellipse, work poorly when the source-to-optics distance is very short.

Biological applications of X-ray microprobes.

Purpose: To present an overview of the workshop on X-ray fluorescence microscopy (XFM).

Results: Talks presented at the workshop and the associated works are highlighted.

Conclusions: Use of XFM in biomedical sciences is growing and may be advanced even further by adding (i) high resolution microprobes, and (ii) high throughput approaches to the XFM toolbox.

Synchrotron X-ray imaging reveals a correlation of tumor copper speciation with Clioquinol's anticancer activity.

Tumor development and metastasis depend on angiogenesis that requires certain growth factors, proteases, and the trace element copper (Cu). Recent studies suggest that Cu could be used as a novel target for cancer therapies. Clioquinol (CQ), an antibiotic that is able to form stable complexes with Cu or zinc (Zn), has shown proteasome-inhibitory, androgen receptor-suppressing, apoptosis-inducing, and antitumor activities in human cancer cells and xenografts.

High-flux hard X-ray microbeam using a single-bounce capillary with doubly focused undulator beam.

A pre-focused X-ray beam at 12 keV and 9 keV has been used to illuminate a single-bounce capillary in order to generate a high-flux X-ray microbeam. The BioCAT undulator X-ray beamline 18ID at the Advanced Photon Source was used to generate the pre-focused beam containing 1.2 x 10(13) photons s(-1) using a sagittal-focusing double-crystal monochromator and a bimorph mirror.

Clioquinol, a therapeutic agent for Alzheimer's disease, has proteasome-inhibitory, androgen receptor-suppressing, apoptosis-inducing, and antitumor activities in human prostate cancer cells and xenografts.

Tumor growth and metastasis depend on angiogenesis that requires the cofactor copper. Consistently, high levels of copper have been found in many types of human cancers, including prostate, breast, colon, and lung. Recent studies suggest that copper could be used as a novel selective target for cancer therapies.

1s2p resonant inelastic X-ray scattering of iron oxides.

1s2p resonant inelastic X-ray scattering (RIXS) spectroscopy has been measured for a series of iron oxides, including octahedral and tetrahedral Fe(II) and Fe(III) systems. Their spectral shapes have been analyzed and explained using crystal-field multiplet simulations. The RIXS planes and the K-edge and L-edge X-ray absorption spectra related to these RIXS planes will be discussed with respect to their analytical opportunities.

Spectrochemical analysis of dental calculus by synchrotron radiation X-ray fluorescence.

This work presents elemental composition studies of human dental calculus by X-ray fluorescence analysis using synchrotron radiation. The intrinsic characteristics of synchrotron light allow for a quantitative analysis of major, minor, and trace elements of very small samples in a single measurement. At present, several theories of calculus formation exist, but none of them can describe completely all the complicated mechanisms involved in the mineralization processes.