title: Steep pH Gradients and Directed Colloid Transport in a Microfluidic Alkaline Hydrothermal Pore.
abstract: All life on earth depends on the generation and exploitation of ionic and pH gradients across membranes. One theory for the origin of life proposes that geological pH gradients were the prebiotic ancestors of these cellular disequilibria. With an alkaline interior and acidic exterior, alkaline vents match the topology of modern cells, but it remains unknown whether the steep pH gradients persist at the microscopic scale. Herein, we demonstrate the existence of 6 pH-unit gradients across micrometer scales in a microfluidic vent replicate. Precipitation of metal sulfides at the interface strengthens the gradients, but even in the absence of precipitates laminar flow sustains the disequilibria. The gradients drive directed transport at the fluid interface, leading to colloid accumulation or depletion. Our results confirm that alkaline vents can provide an exploitable pH gradient, supporting their potential role at the emergence of chemiosmosis and the origin of life.
authors.affiliation: Systems Biophysics, Physics Department, Nanosystems Initiative Munich and Center for NanoScience, Ludwig-Maximilians-Universität München, Amalienstraße 54, 80799, München, Germany.
authors.forename: Friederike M
authors.initials: FM
authors.lastname: Möller
authors.affiliation: Systems Biophysics, Physics Department, Nanosystems Initiative Munich and Center for NanoScience, Ludwig-Maximilians-Universität München, Amalienstraße 54, 80799, München, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Kriegel
authors.affiliation: Systems Biophysics, Physics Department, Nanosystems Initiative Munich and Center for NanoScience, Ludwig-Maximilians-Universität München, Amalienstraße 54, 80799, München, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Kieß
authors.affiliation: Systems Biophysics, Physics Department, Nanosystems Initiative Munich and Center for NanoScience, Ludwig-Maximilians-Universität München, Amalienstraße 54, 80799, München, Germany.
authors.forename: Victor
authors.initials: V
authors.lastname: Sojo
authors.affiliation: Systems Biophysics, Physics Department, Nanosystems Initiative Munich and Center for NanoScience, Ludwig-Maximilians-Universität München, Amalienstraße 54, 80799, München, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Braun
keywords: alkaline vents; diffusiophoresis; molecular electrochemistry; molecular evolution; origin of life