Chemistry Lit Feature Vol. IV

Have you seen a good paper lately? Written one? Send it in and have it featured here! treetownchem@gmail.com

In case you're looking for a little school pride to give you a boost for your end-of-semester activities, for this edition of the Chemistry Literature Feature I've managed to find recent publications in every cluster by University of Michigan students. This month, we'll take a look at inorganic complexes that act like proteins, nanowire solar cells deposited from aqueous solution, and more.

But first, some truth told by a recent seminar speaker:

Overheard at Michigan:

"This is what assistant professors do - just dump a lot of information on you and try to convince you that we know what we're doing."

Analytical: Unveiling the Membrane-Binding Properties of N-Terminal and C-Terminal Regions of G-Protein Coupled Receptor Kinase 5 by Combined Optical Spectroscopies
Some of the most important proteins in your body operate within the cell membrane, and figuring out how membrane proteins work is notoriously complicated. Analytical and biological chemists are always looking for new techniques to help. In a recent paper ($) published in Langmuir (ACS), the authors describe the binding modes and secondary structure of a membrane-bound kinase using two flavors of surface-sensitive infrared spectroscopy (sum frequency generation and attenuated total reflectance). These techniques reveal the equilibrium structure of the protein in the membrane, and are also applied to probe how the structure changes over the course of normal signaling events.
-University of Michigan research from Dr. Zhan Chen's group

Analytical chemists experienced in electrochemistry might enjoy the Materials paper.

Chemical Biology: Model complexes of key intermediates in fungal cytochrome P450 nitric oxide reductase (P450nor)
The reduction of nitric oxide (NO) to nitrous oxide (N₂O) is an important biological pathway in the denitrification arm of the global nitrogen cycle. In cells, the reaction is catalyzed by cytochrome P450 nitric oxide reductases (P450nor) in a process that is not fully understood. One way to shed light on the mechanism is to create synthetic molecular complexes that look and act like the P450nor active sites. These model complexes are much easier to interrogate. In a recent review ($) in Current Opinion in Chemical Biology (Elsevier), the authors review findings from several projects attempting to learn about P450nor's nuts and bolts by making and studying model organometallic complexes.
-Review written by the University of Michigan's Dr. Nicolai Lehnert's group

Fans of Chem Bio may also enjoy the Analytical paper and, if you're involved in simulations, the Physical paper.

Inorganic: A 3-Fold-Symmetric Ligand Based on 2-Hydroxypyridine: Regulation of Ligand Binding by Hydrogen Bonding
Organometallic chemistry has historically focused its efforts on elucidating how chemical reactions take place at the metal center of a complex. However, a newer direction in the field is to exploit the second coordination sphere - parts of the organic ligand that are in proximity to the metal center - to provide new reactivity. In this short communication ($) published in Inorganic Chemistry (ACS), the authors describe the synthesis and characterization of a new three-fold symmetric tautomerizable ligand. The ligand is successfully reacted with copper to create metal complexes with second coordination spheres suited for reacting with small molecules.
-University of Michigan research from Dr. Nathaniel Szymczak's group

Readers specializing in Inorganic chemistry might also like the Chem Bio paper.

Materials: Electrochemical Liquid-Liquid-Solid Deposition of Crystalline Ge Nanowires as a Function of Ga Nanodroplet Size
Synthesizing electrodes of pure germanium, which may be useful in both batteries and solar cells, can be very expensive. Harsh reagents and high temperatures are required. A recent effort ($) published in the Journal of the Electrochemical Society (ECS) continues the work of Dr. Stephen Maldonado's group in synthesizing materials for solar cells via an aqueous solution-based electrochemical process much closer to room temperature. In this work, the authors find that the size of the liquid gallium catalyst employed in the deposition directly controls the morphological properties of the germanium nanowires grown. These nanowires may find applications in lithium batteries, similar to the silicon wires discussed in this post.
-University of Michigan research from Dr. Stephen Maldonado's group

Organic: Directing Group-Controlled Regioselectivity in an Enzymatic C-H Bond Oxygenation
Biocatalysis is a field of chemistry in which naturally-occuring enzymes are used to effect chemical transformations, often on substrates with which they do not typically react. A common line of investigation is to mutate the enzyme of interest, deducing the important parts of its structure by observing how the mutations affect the reactivity for common substrates. In this Journal of the American Chemical Society paper ($), the authors take the reverse approach. Using so-called "substrate engineering," the authors demonstrate that, by changing a specific part of the structure of their macrocyclic substrate, they can effect changes in stereoselectivity several carbon centers away. They provide several useful synthetic observations, but also comment on the prospect of using this approach as a platform to learn more about protein function.
-University of Michigan research collaboration between Dr. Montgomery's and Dr. Sherman's groups

Physical: WExplore: Hierarchical Exploration of High-Dimensional Spaces Using the Weighted Ensemble Algorithm
Molecular dynamics simulations are often used to model the mechanisms of proteins and other biological systems. A classic problem in the field is that it is difficult for a simulation to access rare events, such as large conformational changes in a protein's structure, that are often critical to its function. A recent article ($) featured on the cover of the Journal of Physical Chemistry B (ACS) describes a new algorithm, called WExplore, which allows a simulation to more easily access these exotic regions of configurational space. The algorithm works by assigning a weight to configurations experienced by the simulation. High-probability states are weighted down and are thus less likely to be visited again. Low-probability states are weighted up. The authors use a small peptide simulation to show that the WExplore method accesses protein configurations not often seen in normal simulations.
-University of Michigan research from Dr. Charles Brooks, III's group.
-suggested by Jessica Gagnon

Remember, if you come across an article that you think should be featured here, send it in! treetownchem@gmail.com

ACS - American Chemical Society
ECS - The Electrochemical Society