3 research outputs found
Helvetane and Israelane - Molecule of the Month August 1996 [Archived version]
This is the Molecule of the Month entry for August 1996 about the asteranes (helvetane and israelane). It is a pdf archive version of the HTML webpage
Observation of Ordered Structures in Counterion Layers near Wet Charged Surfaces: A Potential Mechanism for Charge Inversion
Charged (e.g., colloidal) particles
in aqueous solutions will sometimes
behave as though their effective charge has reversed, rather than
reduced, by the attracted counterions. This is counterintuitive because
it increases the electrostatic energy, but it has been proposed that
lateral ordering of the ions could lower the free energy and favor
overcharging (charge inversion). Using X-ray diffraction, we have
observed sharp diffraction peaks from incommensurate Er<sup>3+</sup> counterion monolayers near charged surfaces formed by floating molecular
monolayers. When the counterion lattice does not match the molecular
surface lattice, this means that there is no specific attachment of
ions, and thus the ionic lattice is formed due to interactions between
charges in the counterlayer. Therefore, the existence of incommensurate
ion lattices indicates that counterion ordering is a realistic mechanism.
However, in this system our data rule out a well-known proposed “physical”
mechanismthe Wigner liquid phase driven by Coulomb interactions
Additional file 1: of Enzyme intermediates captured “on the fly” by mix-and-inject serial crystallography
Figure S1. Schematics of the short-time-point mixing injector. Figure S2. Selected views of the CEF binding site in the BlaC shard crystals including simulated annealing omit maps. Figure S3. Structural details, and simulated annealing omit maps, shard crystal form, subunit B (stereo representation, from 30 ms to 2 s). Figure S4. Structural details and simulated annealing omit maps, shard crystal form, subunit D (stereo representation, from 30 ms to 2 s). Figure S5. Structural details, and simulated annealing omit maps, needle crystal form (stereo representation, from 30 ms to 2 s). Figure S6. Backside view of the catalytic cleft of BlaC in the shard crystal form, structural details and simulated annealing omit maps (stereo representation, selected time points). Figure S7. 2mFo-DFc electron density in the catalytic clefts of BlaC in the shard crystal form (stereo representation, from 30 ms to 2 s). Figure S8. 2mFo-DFc electron density and structural details in the catalytic clefts of BlaC in the needle crystal form (stereo representation from 30 ms to 2 s). Figure S9. Details in the catalytic cleft of subunit B in the shard crystal form at 500 ms including the stacked CEF, 2FoFc maps, and simulated annealing omit maps (stereo representation). Figure S10. The catalytic cleft of BlaC, further details, including a difference map between the 500 ms and 100 ms time points. Figure S11. Crystal packing in shards and needles. Figure S12. Dynamic light scattering results. Table S1. B-factors for CEF species observed in the shard crystals at different time delays. (PDF 1646 kb