Pin the tail on the hydrogens: X-ray diffraction has been the method of choice for determining the positions of atoms within a crystal. However, the technique works better for atoms with higher atomic numbers and requires single crystals of a minimum size. Palatinus et al. used electron diffraction, a technique of increasing importance for analyzing very small crystals, to identify the positions of hydrogen atoms in organic and inorganic materials (see the Perspective by McCusker). Science , this issue p. 166 ; see also p. 136

The novel trinuclear Pd(II) complex with an aryl oxime ligand, [Pd₃(C,N-(C₆H₄C(Cl)NO)-4)₆], was synthesized and structurally characterized by elemental analysis (C, H, N), IR, resonance signals in the NMR, and single crystal X-ray crystallography. The interaction ability of the complex with native calf thymus DNA (CT-DNA) was monitored as a function of the metal complex–DNA molar ratio by UV-Vis absorption spectrophotometry, fluorescence spectroscopy, circular dichroism (CD) and thermal denaturation methods. All the experimental evidence indicated that this complex could strongly bind to CT-DNA via a groove mechanism. Further, the albumin interactions of the complex were investigated using fluorescence quenching and synchronous fluorescence spectra. The results of fluorescence titration suggested that the fluorescence quenching of BSA by the complex was a static quenching procedure. The site marker displacement experiment has suggested the location of the complex binding to BSA was Sudlow's site I in subdomain IIA. Finally, the molecular docking experiment confirmed the above results and effectively proved the binding of the Pd(II) complex to BSA and DNA.

Discontinuous modulation functions called crenel and saw-tooth have been developed for description and refinement of strongly modulated crystal structures with abrupt changes of modulation parameters. Although used for refinement of many modulated structures and mentioned in books on aperiodic crystals, technical details of such refinements have never been published and remained hidden in the source code of the refinement program Jana2006. In this article we explain how to recognize discontinuous modulations in a Fourier map and how to refine structures where crenel or saw-tooth functions are combined with additional secondary modulation. Three sets of functions suitable for such combination are presented: the traditional ortho-harmonics, and newly developed sets of Legendre polynomials and x-harmonics. Tiny differences between refinements based on particular function sets are demonstrated using simulated as well as existing modulated structures.

A new method of azide–alkyne cycloaddition (AAC) in the presence of Zn(OAc)₂ as an inexpensive and environmentally friendly catalyst in neat water has been developed.