Microfluidic Production of Pyrophosphate Catalyzed by Mineral Membranes with Steep pH Gradients

Pyrophosphate might have functioned as an energy storage/currency molecule on early Earth, essential for the emergence of life. Here we synthesized mineral membranes involving iron(II), iron(III), and other divalent metal cations (calcium, manganese, cobalt, copper, zinc, and nickel) and tested their ability to catalyze the formation of pyrophosphate from phosphate and acetyl phosphate across steep pH gradients in microfluidic devices. We studied the chemical compositions of the precipitate membranes (which included vivianite, goethite, and green rust) using in situ and ex situ micro-Raman spectroscopy. The yields of pyrophosphate were determined by aqueous ³¹P NMR spectroscopy. We found that Fe²⁺ and Ca²⁺ were the best catalysts for pyrophosphate synthesis among investigated ions; Fe³⁺ and mixed-valence iron membranes were also able to promote pyrophosphate formation. In addition, the pH gradients across the membranes affected the pyrophosphate yields and the smallest pH gradient resulted in the highest yield. These results suggest a possible route of substrate phosphorylation in prebiotic hydrothermal systems.     

Computing projections with LSQR

LSQR uses the Golub-Kahan bidiagonalization process to solve sparse least-squares problems with and without regularization. In some cases, projections of the right-hand side vector are required, rather than the least-squares solution itself. We show that projections may be obtained from the bidiagonalization as linear combinations of (the-oretically) orthogonal vectors. Even the least-squares solution may be obtained from orthogonal vectors, perhaps more accurately than the usual LSQR solution. (However, LSQR has proved equally good in all examples so far.) Presented at the Cornelius Lanczos International Centenary Conference, North Carolina State University, Raleigh, NC, December 1993. Partially supported by Department of Energy grant DE-FG03-92ER25117, National Science Foundation grants DMI-9204208 and DMI-9500668, and Office of Naval Research grants N00014-90-J-1242 and N00014-96-1-0274.     

A tandem Petasis-Ugi multi component condensation reaction: solution phase synthesis of six dimensional libraries

Amino acids with three points of diversity generated from the Petasis boronic acid-Mannich reaction can be used as one of the four components of the Ugi condensation to prepare six dimensional libraries of dipeptide amides.