Understanding the Glycopeptide Antibiotic Crosslinking Cascade: In Vitro Approaches Reveal the Details of a Complex Biosynthesis Pathway

The glycopeptide antibiotics (GPAs) are a fascinating example of complex natural product biosynthesis, with the nonribosomal synthesis of the peptide core coupled to a cytochrome P450-mediated cyclisation cascade that crosslinks aromatic side chains within this peptide. Given that the challenges associated with the synthesis of GPAs stems from their highly crosslinked structure, there is great interest in understanding how biosynthesis accomplishes this challenging set of transformations. In this regard, the use of in vitro experiments has delivered important insights into this process, including the identification of the unique role of the X-domain as a platform for P450 recruitment. In this minireview, we present an analysis of the results of in vitro studies into the GPA cyclisation cascade that have demonstrated both the tolerances and limitations of this process for modified substrates, and in turn developed rules for the future reengineering of this important antibiotic class.

Ultrafast charge rearrangement and nuclear dynamics upon inner-shell multiple ionization of small polyatomic molecules

Ionization and fragmentation of methylselenol (CH(3)SeH) molecules by intense (>10(17) W/cm(2)) 5 fs x-ray pulses (ħω=2 keV) are studied by coincident ion momentum spectroscopy. We contrast the measured charge state distribution with data on atomic Kr, determine kinetic energies of resulting ionic fragments, and compare them to the outcome of a Coulomb explosion model. We find signatures of ultrafast charge redistribution from the inner-shell ionized Se atom to its molecular partners, and observe significant displacement of the atomic constituents in the course of multiple ionization.

Ultrafast charge rearrangement and nuclear dynamics upon inner-shell multiple ionization of small polyatomic molecules

Ionization and fragmentation of methylselenol (CH(3)SeH) molecules by intense (>10(17) W/cm(2)) 5 fs x-ray pulses (ħω=2 keV) are studied by coincident ion momentum spectroscopy. We contrast the measured charge state distribution with data on atomic Kr, determine kinetic energies of resulting ionic fragments, and compare them to the outcome of a Coulomb explosion model. We find signatures of ultrafast charge redistribution from the inner-shell ionized Se atom to its molecular partners, and observe significant displacement of the atomic constituents in the course of multiple ionization.

Femtosecond free-electron laser x-ray diffraction data sets for algorithm development

We describe femtosecond X-ray diffraction data sets of viruses and nanoparticles collected at the Linac Coherent Light Source. The data establish the first large benchmark data sets for coherent diffraction methods freely available to the public, to bolster the development of algorithms that are essential for developing this novel approach as a useful imaging technique. Applications are 2D reconstructions, orientation classification and finally 3D imaging by assembling 2D patterns into a 3D diffraction volume.