13 research outputs found
Photocurrent Enhancement for Ti-Doped Fe<sub>2</sub>O<sub>3</sub> Thin Film Photoanodes by an In Situ Solid-State Reaction Method
In this work, a higher concentration of Ti ions are incorporated
into hydrothermally grown Ti-doped (2.2% by atomic ratio) micro-nanostructured
hematite films by an in situ solid-state reaction method. The doping
concentration is improved from 2.2% to 19.7% after the in situ solid-state
reaction. X-ray absorption analysis indicates the substitution of
Fe ions by Ti ions, without the generation of Fe<sup>2+</sup> defects.
Photoelectrochemical impedance spectroscopy reveals the dramatic improvement
of the electrical conductivity of the hematite film after the in situ
solid-state reaction. As a consequence, the photocurrent density increases
8-fold (from 0.15 mA/cm<sup>2</sup> to 1.2 mA/cm<sup>2</sup>), and
it further increases up to ∼1.5 mA/cm<sup>2</sup> with the
adsorption of Co ions. Our findings demonstrate that the in situ solid-state
reaction is an effective method to increase the doping level of Ti
ions in hematite films with the retention of the micro-nanostructure
of the films and enhance the photocurrent
Micro-Nano-Structured Fe<sub>2</sub>O<sub>3</sub>:Ti/ZnFe<sub>2</sub>O<sub>4</sub> Heterojunction Films for Water Oxidation
IronÂ(III) oxide photoelectrodes show promise in water
oxidation
applications. In this study, micro-nano-structured hematite films
are synthesized, and Ti ions are doped to improve photoelectric conversion
efficiency. The photocurrent increases for enhanced electrical conductivity.
Further enhanced photocurrent is achieved for Fe<sub>2</sub>O<sub>3</sub>:Ti/ZnFe<sub>2</sub>O<sub>4</sub> heterojunction electrodes.
Cyclic voltammograms combined with optical absorbance examinations
demonstrate that the conduction and valence band edges of ZnFe<sub>2</sub>O<sub>4</sub> shift from those of Ti doped Fe<sub>2</sub>O<sub>3</sub> to the negative direction, which facilitates the efficient
separation of electron–hole pairs at the Fe<sub>2</sub>O<sub>3</sub>:Ti/ZnFe<sub>2</sub>O<sub>4</sub> interface. These findings
demonstrate that, by doping hematite and by engineering the interface
between the hematite and the electrolyte, charge separation can be
effectively promoted and photocurrent density can be dramatically
increased
A Maltose-Binding Protein Fusion Construct Yields a Robust Crystallography Platform for MCL1
<div><p>Crystallization of a maltose-binding protein MCL1 fusion has yielded a robust crystallography platform that generated the first apo MCL1 crystal structure, as well as five ligand-bound structures. The ability to obtain fragment-bound structures advances structure-based drug design efforts that, despite considerable effort, had previously been intractable by crystallography. In the ligand-independent crystal form we identify inhibitor binding modes not observed in earlier crystallographic systems. This MBP-MCL1 construct dramatically improves the structural understanding of well-validated MCL1 ligands, and will likely catalyze the structure-based optimization of high affinity MCL1 inhibitors.</p></div
The structure of Apo MBP-MCL1 determined at 1.90 Ã….
<p>(A) The MBP domain (red) is connected by a short GS linker (orange) to MCL1 173–321 (blue). A portion of alpha helix four is not ordered in the structure (red dashed-line). Maltose ligand is shown in yellow. (B) The MCL1 domain is structurally very similar to the NMR structure of Apo-MCL1 (gray).</p
Comparison of PDB 4HW3 and MBP-MCL1 with fragment 4.
<p>The structure of MBP-MCL1 with fragment <b>4</b> (yellow) determined to 2.4 Å (blue) overlaid with the structure of MCL1 171–323 determined at 2.4 Å (PDB ID 4HW3, gray). The carboxylic acid of 4HW3 adopts multiple conformations depending on the chain; only chain A is shown for clarity.</p
The structure of MBP-MCL1 bound to fragment 5 determined at 1.9 Ã….
<p>Fragment <b>5</b> (yellow) binds similarly in comparison to the elaborated ligand from PDB ID 4OQ6 (gray).</p
The conformational flexibility of the binding pocket of MCL1.
<p>Surface representations are shown as side views and ligands are shown as yellow sticks. (A and B) Fragment 4 maps onto L78 of NoxaB from PDB ID 2NLA, with only minor structural perturbation of the BH3-binding groove of MCL1. In contrast, binding of fragment 6 creates a significant pocket (C) which is further expanded upon binding of ligand 1 (D).</p
Binding affinity (K<sub>D</sub>) of ligands to MCL1 and MBP-MCL1.
<p>All experiments are n ≥ 3, and averaged values for K<sub>D</sub> are reported.</p><p>Binding affinity (K<sub>D</sub>) of ligands to MCL1 and MBP-MCL1.</p
MCL1 ligands used in co-crystallization experiments.
<p>MCL1 ligands used in co-crystallization experiments.</p
Structure of MBP-MCL1 bound to fragment 6 determined at 2.0 Ã….
<p>(A) The surface side-view shows that fragment <b>6</b> shifts and makes water mediated hydrogen bond contacts with the peptide backbone of R263. (B) The elaborated ligand of fragment <b>6</b> (PDB ID 4OQ5) shifts to allow the methyl-naphthalene to bind in the hydrophobic pocket, requiring the carboxylic acid to make a single hydrogen bond with the sidechain of R263. (C) Overlay of crystallized fragment <b>6</b> and the elaborated ligand in PDB ID 4OQ5 reveals a distinct binding pose for <b>6</b>.</p