the week of Sunday, April 22nd, 2018

Wednesday, April 25th, 2018, Wednesday Seminar

4:10 PM, 55 Roessler
Tea and cookies at 3:45 in the aviary - (2110 EPS)

“Protocell Self-Assembly in the Origins of Life”

      – by Dr. Nita Sahai, University of Akron

The potential roles of minerals in the origins of life have long been postulated but few
studies have been conducted under geochemically relevant conditions using minerals, rocks and
aqueous solution compositions expected to have been present on early Earth. In our group, we
attempt to (i) determine the constraints placed by atmosphere-water-rock interactions on the self-assembly of the molecular building blocks of the earliest living cell-like entities, 'protocells,'
and (ii) identify structure-activity relationships (SAR) for these mineral-organic interactions that
should enable us to predict which environments are capable of supporting the origins of life. We
are studying the stability of protocell membranes.

In one study, we discovered a SAR between the surface charge (isoelectric point) of
minerals and the formation-rates of amphiphile vesicles and with critical vesicle concentration.
The vesicles represent model protocell membranes. However, minerals did not affect membrane
integrity of pre-formed vesicles. Thus, minerals could have affected initial protocell membrane
self-assembly but, once formed, protocells could have survived in contact with rock surfaces.

In a second study, we addressed the problem that modern geochemical concentrations of
total dissolved phosphate (PT) and Mg2+ are much lower than are required for non-enzyamtic
(prebiotic) RNA synthesis, while Mg2 and Ca2+ concentrations are too high for membrane
stability, so how did life emerge on early Earth? We used a geochemical thermodynamic
modeling approach, to show that a single, unified and globally-occurring geological process of
komatiite rock weathering and evaporation of the resulting solutions under specific partial
pressures of atmospheric CO2 (PCO2) and temperatures can quantitatively provide the PT , Mg2+ and
Ca2+ concentrations required biologically for nucleotide synthesis, RNA polymerization and
protocell-membrane stability. It is fascinating that, conversely, the biologically-required
concentrations of PT , Mg2+ and Ca2+ place constraints on the PCO2 levels on early Earth compared
to previous estimates for PCO2 on Hadean and early Archean Earth which have ranged over five
orders of magnitude.

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Friday, April 27th, 2018, Friday Brown Bag

12:10 PM, 1316 Earth and Physical Sciences

“The age of the Earth's inner core”

      – by Prof. John Tarduno, Department of Earth and Environmental Sciences, University of Rochester

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