Search

Mechanisms of nucleic acid accumulation were likely critical to life's emergence in the ferruginous oceans of the early Earth. How exactly prebiotic geological settings accumulated nucleic acids from dilute aqueous solutions, is poorly understood. As a possible solution to this concentration problem, we simulated the conditions of prebiotic low-temperature alkaline hydrothermal vents in co-precipitation experiments to investigate the potential of ferruginous chemical gardens to accumulate nucleic acids via sorption. The injection of an alkaline solution into an artificial ferruginous solution under anoxic conditions (O 2  < 0.01% of present atmospheric levels) and at ambient temperatures, caused the precipitation of amakinite ("white rust"), which quickly converted to chloride-containing fougerite ("green rust"). RNA was only extractable from the ferruginous solution in the presence of a phosphate buffer, suggesting RNA in solution was bound to Fe 2+ ions. During chimney formation, this iron-bound RNA rapidly accumulated in the white and green rust chimney structure from the surrounding ferruginous solution at the fastest rates in the initial white rust phase and correspondingly slower rates in the following green rust phase. This represents a new mechanism for nucleic acid accumulation in the ferruginous oceans of the early Earth, in addition to wet-dry cycles and may have helped to concentrate RNA in a dilute prebiotic ocean., (© 2023 The Authors. Geobiology published by John Wiley & Sons Ltd.)

Alkaline vents (AVs) are hypothesized to have been a setting for the emergence of life, by creating strong gradients across inorganic membranes within chimney structures. In the past, three-dimensional chimney structures were formed under laboratory conditions; however, no in situ visualization or testing of the gradients was possible. We develop a quasi-two-dimensional microfluidic model of AVs that allows spatiotemporal visualization of mineral precipitation in low-volume experiments. Upon injection of an alkaline fluid into an acidic, iron-rich solution, we observe a diverse set of precipitation morphologies, mainly controlled by flow rate and ion concentration. Using microscope imaging and pH-dependent dyes, we show that finger-like precipitates can facilitate formation and maintenance of microscale pH gradients and accumulation of dispersed particles in confined geometries. Our findings establish a model to investigate the potential of gradients across a semipermeable boundary for early compartmentalization, accumulation, and chemical reactions at the origins of life.

Background: The impact of frailty on walking recovery after hip fracture has not been reported. We describe the prevalence of frailty approximately 3 months after hip fracture, and identify the impact of baseline frailty on ambulation recovery., Methods: Data from the Community Ambulation Project, that examined the effects of 2 multicomponent home exercise programs on 6-minute walk test in participants post hip fracture, were used to reconstruct the 5-item frailty phenotype. We detailed the prevalence of frailty by subgroup and assessed the comparability between frailty groups for the categorical variable of achieving 300 m in 6-minute walk test (community ambulation threshold), and the continuous variable of total distance in 6-minute walk test before and after 16 weeks of intervention., Results: Of the 210 participants, 9% were nonfrail, 59% were prefrail, and 32% were frail. The odds of a nonfrail participant achieving the 300-m threshold were 14.4 (95% CI: 2.4-87.6) times the odds of a frail participant, while a prefrail participant's odds were 6.1 (95% CI: 1.3-28.4) times after controlling for treatment group and baseline walking distance. The nonfrail participants had an increase of 92.1 m from baseline to 16 weeks, the prefrail had a 50.8 m increase, and the frail group had the smallest increase of 36.6 m (p < .001 for all)., Conclusions: Prefrailty and frailty were highly prevalent in this sample of community-dwelling survivors of a recent hip fracture. Gains in walking distance and attaining a level of community ambulation were affected significantly by the level of baseline frailty., (© The Author(s) 2021. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)