Search

Your search keyword '"Robert J Nicholas"' showing total 2 results
Start Over Author "Robert J Nicholas"
2 results on '"Robert J Nicholas"'

1. Development of an Efficient, High Purity Continuous Flow Synthesis of Diazepam

Author

Robert J. Nicholas, Michael A. McGuire, Seok-Hee Hyun, Madeline N. Cullison, and David H. Thompson

Subjects
diazepam, benzodiazepine, continuous syntheses, reaction scale-up, common ion effect, process optimization, Technology, Chemical technology, TP1-1185
Abstract

In an effort to strengthen the resiliency of supply chains for active pharmaceutical ingredients (API), continuous manufacturing processes may be optimized with respect to improved chemoselectivity, production rate, yield, and/or process intensity. We report an efficient two-step continuous flow synthesis of diazepam, an agent on the World Health Organization’s (WHO) list of essential medicines. Different conditions were rapidly screened in microfluidic chip reactors by varying residence times, temperatures, solvents, and ammonia sources to identify the best telescoped reaction conditions. We report a telescoped flow synthesis that uses two microreactors in series set to 0°C and 60°C, respectively, to produce a 96% yield of 91% pure diazepam within 15 min using an NH4Br/NH4OH solution in the second step. Diazepam of >98% purity was obtained after a single recrystallization.

Published
2022
Full Text
View/download PDF

2. Affinity Capture of p97 with Small-Molecule Ligand Bait Reveals a 3.6 Å Double-Hexamer Cryoelectron Microscopy Structure

Author

David H. Thompson, Wen Jiang, Kunpeng Li, Donna M. Huryn, Rejaul Hoq, Frank S. Vago, Peter Wipf, Robert J Nicholas, and Marina Kovaliov

Subjects
Schiff base, Capture antibody, Cryoelectron Microscopy, General Engineering, Small molecule ligand, General Physics and Astronomy, 02 engineering and technology, Random hexamer, 010402 general chemistry, 021001 nanoscience & nanotechnology, Electrostatics, Ligands, 01 natural sciences, AAA proteins, Antibodies, 0104 chemical sciences, Physical Phenomena, chemistry.chemical_compound, chemistry, Microscopy, Biophysics, Humans, General Materials Science, 0210 nano-technology, Histidine
Abstract

Recent progress in the development of affinity grids for cryoelectron microscopy (cryo-EM) typically employs genetic engineering of the protein sample such as histidine or Spy tagging, immobilized antibody capture, or nonselective immobilization via electrostatic interactions or Schiff base formation. We report a powerful and flexible method for the affinity capture of target proteins for cryo-EM analysis that utilizes small-molecule ligands as bait for concentrating human target proteins directly onto the grid surface for single-particle reconstruction. This approach is demonstrated for human p97, captured using two different small-molecule high-affinity ligands of this AAA+ ATPase. Four electron density maps are revealed, each representing a p97 conformational state captured from solution, including a double-hexamer structure resolved to 3.6 A. These results demonstrate that the noncovalent capture of protein targets on EM grids modified with high-affinity ligands can enable the structure elucidation of multiple configurational states of the target and potentially inform structure-based drug design campaigns.

Published
2021

Catalog

Books, media, physical & digital resources
See catalog results