September 21, 2011
microRNAs, Molecular Clocks and Metazoan Macroevolution
Kevin J. Peterson (Dartmouth College)

Diverse bilaterian clades emerged apparently within a few million years during the early Cambrian, and various environmental, developmental, and ecological causes have been proposed to explain this abrupt appearance. A compilation of the patterns of fossil and molecular diversification, comparative developmental data, and information on ecological feeding strategies, indicate that the major animal clades diverged many tens of millions of years before their first appearance in the fossil record, establishing a macroevolutionary lag between the establishment of their developmental toolkits during the Cryogenian (850-635 Ma), and their later ecological success during the Ediacaran and Cambrian periods. We argue that this diversification involved new forms of developmental regulation, as well as innovations in networks of ecological interaction within the context of permissive environmental circumstances.

November 16, 2011
New paradigms at the proto-life/synthetic biology interface
Stephen Mann (University of Bristol-UK)

The advent of life from pre-biotic origins remains a deep and possibly inexplicable scientific mystery. Nevertheless, the logic of living cells offers potential insights into an unknown proto-biological world that can be used to stimulate novel advances in living technologies, artificial life and systems chemistry. In this talk, I will review some recent studies undertaken in our laboratory that provide alternative paradigms at the interface between proto-life research and synthetic biology. Two themes will be addressed (somewhat obliquely!). Firstly, can proteins maintain their structure and function in the absence of water (or any other solvent) whilst retained in the liquid state? And secondly, can protocell models be constructed without an enclosing organic membrane? Specifically, I will describe our current studies on the first known examples of solvent-less liquid proteins [1,2], including studies on the dioxygen binding and temperature-dependent chain unfolding properties of liquid myoglobin. Then I will discuss our recent investigations on artificial protocells that are derived from inorganic [3] or membrane-free [4] compartmentalization, and illustrate respectively how such structures can be used as bio-inorganic reactors for enzyme catalysis and in vitro gene expression, or as a plausible model of pre-biotic organization. [1] Perriman A W, Cölfen H, Hughes R W, Barrie C L and Mann S. Protein melts and protein liquid crystals in solvent-free media. Angew. Chemie Int. Ed. 48, 6247-6250 (2009). [2] Perriman A W, Brogan A P S, Cölfen H, Tsoureas N, Owen G R and Mann S. Reversible dioxygen binding in solvent-free liquid myoglobin. Nature Chemistry 2, 622-626 (2010). [3] Koga S, Williams D S, Perriman A W, and Mann S. Peptide/nucleotide micro-droplets as a step towards a membrane-free protocell model. Nature Chemistry 3, 720-724 (2011). [4] Li M, Green D C, Anderson J L R, Binks B P and Mann S. In vitro gene expression and enzyme catalysis in bio-inorganic protocells, Chemical Science, 2, 1739-1745 (2011).

February 15, 2012
How do bugs' gases alter planetary atmospheres?
Paul Falkowski (Rutgers University)

A basic principle of a living organism, that is often unrecognized, is that it must exchange materials with its environment. On Earth, the exchanges are primarily through gases and virtually all gas fluxes are mediate via microbes. Microbial metabolism on Earth is based on a very straightforward, integrated electronic circuit - with a power supply from the sun, the membranes of organisms acting as circuit boards, and enzymes acting as transistors. The input functions are reduced or oxidized molecules - the output functions are the converse of the substrates. Given the hierarchy of redox reactions, we can theoretically propose an outcome of metabolism that can define life on an extrasolar planet.

March 21, 2012
Water Beyond Earth: A Remote Sensing Perspective
Ralph Milliken (University of Notre Dame)

Water has without question played an important role in the evolution of our solar system. In particular, both laboratory and remote spectroscopic techniques have led to the discovery of hydration on Mars, in meteorites and on their potential asteroid parent bodies, the dwarf planet Ceres, and the surface of the Moon. Coupled with laboratory and theoretical studies, these remotely-acquired data have also led to the first quantitative spatial and temporal maps of the water content of the optical surface of Mars. In addition, detailed spectral analyses of Martian clay minerals suggests that many may have experienced diagenesis, as is common on Earth, raising questions about their potential for preserving organic material. Beyond Mars, recent interpretations of ground-based telescopic data of Ceres, a target of NASA’s Dawn mission in 2015, have suggested the presence of significant amounts of brucite and Mg-carbonates on the dwarf planet. This composition puts into question proposed compositional and genetic links between this body and the carbonaceous chondrites, and it may even suggest Ceres has experienced more extensive aqueous alteration than anything represented in current meteorite collections. This talk will examine the past, present, and future of remote spectroscopic techniques for addressing outstanding questions related to the amount and extent of aqueous alteration in our solar system, with a focus on current and upcoming missions such as the Mars Science Laboratory rover, the Moon Mineralogy Mapper, and the Dawn mission.

April 18, 2012
Southpaw Solar System: L-Amino Acid Excesses in Meteorites and Implications for the Origin of Life
Daniel Glavin (NASA-Goddard Space Flight Center)

Meteorites provide a record of the chemical processes that occurred in the early solar system before life began on Earth. The delivery of complex organic compounds by carbonaceous chondrites to the early Earth and other planetary bodies could have been an important source of prebiotic compounds required for the emergence of life. Of particular interest is the study of meteoritic amino acids and their enantiomeric compositions since these molecules are the monomers of proteins common to all life on Earth. The single chirality observed in biological molecules - left-handed amino acids and right-handed sugars - is a property important for molecular recognition processes and is thought to be a prerequisite for life. In contrast to biology, all known abiotic syntheses of amino acids result in equal mixtures of left- and right-handed (L = D) amino acids. Therefore, how the nearly exclusive production of one hand of such molecules arose from what were presumably equal mixtures of L and D molecules in a prebiotic world has been an area of intensive research. A predominance of left- over right-handed amino acids has been found in some meteorites, but the origin of the asymmetry remains unclear. In this talk, I will discuss recent data of the distribution, enantiomeric composition, and carbon isotopic ratios of amino acids in a variety of carbonaceous meteorites that have undergone a wide range of aqueous alteration on the meteorite parent body by using both ultra-high performance liquid chromatography fluorescence detection and time-of-flight mass spectrometry and gas chromatography mass spectrometry and isotope ratio mass spectrometry techniques. For certain chiral amino acids, the magnitude of the L-excess appears to correlate with the degree of aqueous alteration of the meteorite and suggests that liquid water played an important role in the amplification of L- over D-amino acid acids on the parent asteroid. Possible explanations for the formation of meteoritic amino acids and their enantiomeric excesses will be discussed.

May 16, 2012
On the Chemical Origins of Nucleotides
Matthew Powner (University College, London)

A plausible abiotic chemical route to the canonical nucleotides is a major goal in origins of life research. Some of our most recent efforts to understand the intrinsic chemical requirements for nucleotide synthesis in water will be discussed.(1)(2) Having previously reported a chemoselective, prebiotically plausible route to activated canonical pyrimidine ribonucleotides;(3)(4) we have recently demonstrated the first chemical steps towards a divergent pyrimidine and purine ribonucleotide synthesis.(5) A one-pot multicomponent reaction (MCR) was demonstrated to stereoselectively tether and consequently regiospecifically glycosylate purine precursors and masked pentose sugars, whilst concurrently furnishing known pyrimidine ribonucleotide precursors. RNA is ribonucleotide polymer linked homogeneously by 5'-3'-phosphodiester backbone. However, ribonucleotides have a linkage ambiguity (5'-3' vs. 5'-2') at every phosphodiester bond. Ostensibly the linkage heterogeneity must be addressed, in the absence of sophisticated enzymatic catalysis, for the effective abiotic synthesis of RNA. An acyl-transfer cascade, which is a potential solution to RNA linkage heterogeneity and the experimental demonstration of ribozyme catalysis in heterogeneous 5'-3'/5'-2' RNA will be presented. Finally, although RNA has often been considered as a candidate for the first biopolymer of life, extant biology utilizes two chemically distinct, but related, nucleotide polymers, RNA and DNA. DNA is usually viewed as a late evolutionary adaptation of earlier RNA-based life. However, it would not be possible to make DNA without deoxyribonucleotides, and yet in the absence of DNA there is no obvious reason for the evolution of the biochemical pathways for the synthesis of deoxyribonucleotides. The possible implications of organosulfur compounds towards a concurrent abiotic synthesis of both RNA and DNA will be addressed. (1) Powner, M. W.; Sutherland, J. D.; Szostak, J. W. Synlett, 2011, 14, 1956. (2) Powner, M. W.; Sutherland, J. D. Phil. Trans. R. Soc. B. 2011, 366, 2870. (3) Powner, M. W.; Gerland, B.; Sutherland, J. D. Nature 2009, 495, 239. (4) Powner, M. W.; Sutherland, J. D. Angew. Chem. Int. Ed. 2010, 49, 4641. (5) Powner, M. W.; Sutherland, J. D.; Szostak, J. W. J. Am. Chem. Soc. 2010, 132, 16677.