Education and work:
- BS in Molecular Biology, 110/110 Magna Cum Laude, University of Bologna, Italy (2002)
- PhD in Genetics/Astrobiology, University of Florence, Italy (2007)
- Postdoctoral Research Fellow, Astrobiology & RNA Biochemistry, University of Missouri-Columbia (2007-2012)
- Research Scientist at FfAME (2012-present)
My current research focuses on evolving AEGIS-based DNA and RNA aptamers against potential bioterroristic threats through in-vitro selection (SELEX). At the moment our main targets are Ricin Chain-A, and Anthrax Protective Antigen. The presence of the stronger Z-P pair in these aptamers amplifies the sequence space and 3D landscape of starting populations, and should ensure increased stability, lower kd values, and better detection limits compared to standard ACT/UG-based aptamers.
Other ongoing projects involve:
- Post-selection modification of ACUG-selected aptamers with Z and P bases for improved activity
- Evolution of aptamers able to bind Z and P nucleosides, to facilitate the detection of AEGIS-DNA and RNA, and separation from standard nucleic acids
- Development of AEGIS-based and standard ACTG DNA nanostructures to create easy assembly educational kits and for nanotechnology applications
When Did Life Likely Emerge on Earth in an RNA-First Process?
S. A. Benner, E. A. Bell, E. Biondi, R. Brasser, T. Carell, H.-J. Kim, S. J. Mojzsis, A. Omran, M. A. Pasek, D. Trail
2 , Chemistry Europe (2020) e1900035
The widespread presence of ribonucleic acid (RNA) catalysts and cofactors in the Earth's biosphere today suggests that RNA was the first biopolymer to support Darwinian evolution. However, most "path-hypotheses" to generate building blocks for RNA require reduced nitrogen-containing compounds not made in useful amounts in the CO2-N2-H2O atmospheres of the Hadean. We review models for Earth's impact history that invoke a single ~1023 kg impactor (Moneta) to account for measured amounts of platinum, gold, and other siderophilic ("iron-loving") elements on the Earth and Moon. If it were the last sterilizing impactor, by reducing the atmosphere but not the mantle Moneta, would have opened a "window of opportunity" for RNA synthesis, a period when RNA precursors rained from the atmosphere onto land holding oxidized minerals that stabilize advanced RNA precursors and RNA. Surprisingly, this combination of physics, geology, and chemistry suggests a time when RNA formation was most probable, ~120±100 million years after Moneta's impact, or ~4.36±0.1 billion years ago. Uncertainties in this time are driven by uncertainties in rates of productive atmosphere loss and amounts of sub-aerial land.
Prebiotic Chemistry that Could Not Not Have Happened
Benner S.A., Kim H.-J., and Biondi E.
9 (4) , MDPI 84 (2019) https://doi.org/10.3390/life9040084
We present a direct route by which RNA might have emerged in the Hadean from a fayalite-magnetite mantle, volcanic SO2 gas, and well-accepted processes that must have created substantial amounts of HCHO and catalytic amounts of glycolaldehyde in the Hadean atmosphere. In chemistry that could not not have happened, these would have generated stable bisulfite addition products that must have rained to the surface, where they unavoidably would have slowly released reactive species that generated higher carbohydrates. The formation of higher carbohydrates is self-limited by bisulfite formation, while borate minerals may have controlled aldol reactions that occurred on any semi-arid surface to capture that precipitation. All of these processes have well-studied laboratory correlates. Further, any semi-arid land with phosphate should have had phosphate anhydrides that, with NH3, gave carbohydrate derivatives that directly react with nucleobases to form the canonical nucleosides. These are phosphorylated by magnesium borophosphate minerals (e.g., luneburgite) and/or trimetaphosphate-borate with Ni2+ catalysis to give nucleoside 5'-diphosphates, which oligomerize to RNA via a variety of mechanisms. The reduced precursors that are required to form the nucleobases came, in this path-hypothesis, from one or more mid-sized (1023-1020 kg) impactors that almost certainly arrived after the Moon-forming event. Their iron metal content almost certainly generated ammonia, nucleobase precursors, and other reduced species in the Hadean atmosphere after it transiently placed the atmosphere out of redox equilibrium with the mantle. In addition to the inevitability of steps in this path-hypothesis on a Hadean Earth if it had semi-arid land, these processes may also have occurred on Mars. Adapted from a lecture by the Corresponding Author at the All-Russia Science Festival at the Lomonosov Moscow State University on 12 October 2019, and is an outcome of a three year project supported by the John Templeton Foundation and the NASA Astrobiology program. Dedicated to David Deamer, on the occasion of his 80th Birthday.
Artificially Expanded Genetic Information Systems
for New Aptamer Technologies
Elisa Biondi and Steven A. Benner
, MDPI (2018) 6, 53; doi:10.3390/biomedicines6020053
Directed evolution was first applied to diverse libraries of DNA and RNA molecules a
quarter century ago in the hope of gaining technology that would allow the creation of receptors,
ligands, and catalysts on demand. Despite isolated successes, the outputs of this technology have been
somewhat disappointing, perhaps because the four building blocks of standard DNA and RNA have
too little functionality to have versatile binding properties, and offer too little information density
to fold unambiguously. This review covers the recent literature that seeks to create an improved
platform to support laboratory Darwinism, one based on an artificially expanded genetic information
system (AEGIS) that adds independently replicating nucleotide "letters" to the evolving "alphabet".
Mineral-Organic Interactions in Prebiotic
Synthesis. The Discontinuous Synthesis Model for the Formation of RNA in Naturally Complex Geological Environments.
Steven A. Benner, Hyo-Joong Kim, and Elisa Biondi
Nucl. Acids & Mol. Bio.
35 , Springer 31-83 (2018) https://doi.org/10.1007/978-3-319-93584-3_3
A common criticism of "prebiotic chemistry research" is that it is done
with starting materials that are too pure, in experiments that are too directed, to get
results that are too scripted, under conditions that could never have existed on Earth.
Planetary scientists in particular remark that these experiments often arise simply
because a chemist has a "cool idea" and then pursues it without considering external
factors, especially geological and planetary context. A growing literature addresses
this criticism and is reviewed here. We assume a model where RNA emerged
spontaneously from a prebiotic environment on early Earth, giving the planet its
first access to Darwinism. This "RNA First Hypothesis" is not driven by the intrinsic
prebiotic accessibility; quite the contrary, RNA is a "prebiotic chemist's nightmare."
However, by assuming models for the accretion of the Earth, the formation of the
Moon, and the acquisition of Earth's "late veneer," a reasonable geological model
can be envisioned to deliver the organic precursors needed to form the nucleobases
and ribose of RNA. A geological model having an environment with dry arid land
under a carbon dioxide atmosphere receiving effluent from serpentinizing igneous
rocks allows their conversion to nucleosides and nucleoside phosphates. Mineral
elements including boron and molybdenum prevent organic material from devolving
to form "tars" along the way. And dehydration and activation allows the formation of
oligomeric RNA that can be stabilized by adsorption on available minerals.
Adsorption of RNA on mineral surfaces and mineral precipitates
Elisa Biondi, Yoshihiro Furukawa, Jun Kawai, and Steven A. Benner
Beilstein J. Org. Chem.
, Beilstein Institute (2017) 13, 393-404
The prebiotic significance of laboratory experiments that study the interactions between oligomeric RNA and mineral species is difficult to know. Natural exemplars of specific minerals can differ widely depending on their provenance. While laboratory-generated samples of synthetic minerals can have controlled compositions, they are often viewed as "unnatural". Here, we show how trends in the interaction of RNA with natural mineral specimens, synthetic mineral specimens, and co-precipitated pairs of synthetic minerals, can make a persuasive case that the observed interactions reflect the composition of the minerals themselves, rather than their being simply examples of large molecules associating nonspecifically with large surfaces. Using this approach, we have discovered Periodic Table trends in the binding of oligomeric RNA to alkaline earth carbonate minerals and alkaline earth sulfate minerals, where those trends are the same when measured in natural and synthetic minerals. They are also validated by comparison of co-precipitated synthetic minerals. We also show differential binding of RNA to polymorphic forms of calcium carbonate, and the stabilization of bound RNA on aragonite. These have relevance to the prebiotic stabilization of RNA, where such carbonate minerals are expected to have been abundant, as they appear to be today on Mars.
Laboratory evolution of artificially expanded DNA gives redesignable aptamers that target the toxic form of anthrax protective antigen
Biondi E, Lane JD, Das D, Dasgupta S, Piccirilli JA, Hoshika S, Bradley KM, Krantz BA, Benner SA
Nucl. Acids Res.
(2016) Oct 3. pii: gkw890. PubMed PMID: 27701076
Reported here is a laboratory in vitro evolution (LIVE)
experiment based on an artificially expanded genetic
information system (AEGIS). This experiment delivers
the first example of an AEGIS aptamer that binds
to an isolated protein target, the first whose structural
contact with its target has been outlined and
the first to inhibit biologically important activities of
its target, the protective antigen from Bacillus anthracis.
We show how rational design based on secondary
structure predictions can also direct the use
of AEGIS to improve the stability and binding of the
aptamer to its target. The final aptamer has a dissociation
constant of ~35 nM. These results illustrate
the value of AEGIS-LIVE for those seeking to
obtain receptors and ligands without the complexities
of medicinal chemistry, and also challenge the
biophysical community to develop new tools to analyze
the spectroscopic signatures of new DNA folds
that will emerge in synthetic genetic systems replacing
standard DNA and RNA as platforms for LIVE.
Opal Absorbs and Stabilizes RNA - A Hierarchy of Prebiotic Silica
Biondi, E.; Howell, L.; Benner, S.A.
(2016) 27, A-E
A widely held 'RNA first' model proposes that RNA gave organic
matter on Earth its first access to Darwinism. Such a proposal,
which requires a mechanism to generate RNA from a prebiotic 'soup',
must also manage the intrinsic instability of any RNA so formed. Here,
we show that silicon dioxide (silica, SiO2), in the form of synthetic opal,
adsorbs and stabilizes RNA from aqueous solution. The extent of absorption
on fully amorphous silica is less, as is the extent of adsorption
on the surface of crystalline quartz. We show that the RNA adsorbed on
opal is considerably more stable than the same RNA molecule free in
aqueous solution at pH 9.5. This provides a mechanism by which any
RNA formed in a prebiotic environment could have been concentrated
and stabilized so that it could have later participated in the first Darwinian
RNA structural analysis by enzymatic digestion
Biondi E., Burke D.H.
Methods Mol Biol
, Springer (2014) 1086:41-52
Potent Inhibition of HIV-1 Reverse Transcriptase and Replication by Nonpseudoknot, "UCAA-motif" RNA Aptamers
Whatley A.S., Ditzler M.A., Lange M.J., Biondi E., Sawyer A.W., Chang J.L., Franken J.D., Burke D.H.
Mol Ther Nucleic Acids
, Nature (2013) 2:e71
Lewis acid catalysis of phosphoryl transfer from a copper(II)-NTP complex in a kinase ribozyme
Biondi E., Poudyal R.R., Forgy J.C., Sawyer A.W., Maxwell A.W., Burke D.H
Nucl. Acids Res.
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