Synthesis of uniformly deuteratedn-dodecyl-β-d-maltoside (d39-DDM) for solubilization of membrane proteins in TROSY NMR experiments

Unprecedented Convergent Synthesis of Sugar-Functionalization of Phosphinic Acids under Metal-Free Conditions

A novel TEA-catalyzed sugar-esterification of phosphinic acids was used as a general and efficient approach for the synthesis of a variety of phosphinates without any transition metal. The high efficiency of the current methodology and a convenient experimental procedure compensate for the moderate yields obtained. Another advantage is that the reaction tolerates different substituents attached to the phosphinic acids and the sugar moieties alongside the ease of isolation of the product.

Contrast-Matching Detergent in Small-Angle Neutron Scattering Experiments for Membrane Protein Structural Analysis and Ab Initio Modeling

The biological small-angle neutron scattering instrument at the High-Flux Isotope Reactor of Oak Ridge National Laboratory is dedicated to the investigation of biological materials, biofuel processing, and bio-inspired materials covering nanometer to micrometer length scales. The methods presented here for investigating physical properties (i.e., size and shape) of membrane proteins (here, MmIAP, an intramembrane aspartyl protease from Methanoculleus marisnigri) in solutions of micelle-forming detergents are well-suited for this small-angle neutron scattering instrument, among others. Other biophysical characterization techniques are hindered by their inability to address the detergent contributions in a protein-detergent complex structure. Additionally, access to the Bio-Deuteration Lab provides unique capabilities for preparing large-scale cultivations and expressing deuterium-labeled proteins for enhanced scattering signal from the protein. While this technique does not provide structural details at high-resolution, the structural knowledge gap for membrane proteins contains many addressable areas of research without requiring near-atomic resolution. For example, these areas include determination of oligomeric states, complex formation, conformational changes during perturbation, and folding/unfolding events. These investigations can be readily accomplished through applications of this method.

Designing Mixed Detergent Micelles for Uniform Neutron Contrast

Micelle-forming detergents provide an amphipathic environment that mimics lipid bilayers and are important tools used to solubilize and stabilize membrane proteins in solution for in vitro structural investigations. Small-angle neutron scattering (SANS) at the neutron contrast match point of detergent molecules allows observing the signal from membrane proteins unobstructed by contributions from the detergent. However, we show that even for a perfectly average-contrast matched detergent there arises significant core-shell scattering from the contrast difference between aliphatic detergent tails and hydrophilic head groups. This residual signal interferes with interpreting structural data of membrane proteins. This complication is often made worse by the presence of excess empty (protein-free) micelles. We present an approach for the rational design of mixed micelles containing a deuterated detergent analog, which eliminates neutron contrast between core and shell and allows the micelle scattering to be fully contrast-matched to unambiguously resolve membrane protein structure using solution SANS.