The clay montmorillonite is known to catalyze the polymerization of RNA from activated ribonucleotides. Here we report that montmorillonite accelerates the spontaneous conversion of fatty acid micelles into vesicles. Clay particles often become encapsulated in these vesicles, thus providing a pathway for the prebiotic encapsulation of catalytically active surfaces within membrane vesicles. In addition, RNA adsorbed to clay can be encapsulated within vesicles. Once formed, such vesicles can grow by incorporating fatty acid supplied as micelles and can divide without dilution of their contents by extrusion through small pores. These processes mediate vesicle replication through cycles of growth and division. The formation, growth, and division of the earliest cells may have occurred in response to similar interactions with mineral particles and inputs of material and energy.
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The potential for self-replication makes RNA an attractive candidate as a primordial catalysis in the origin of life. Catalysis may have occurred in some kind of compartment, possibly a fatty acid vesicle. However, RNA catalysis generally requires high levels of magnesium, which are incompatible with fatty acid vesicle integrity. Adamala and Szostak (p. [1098][1]) screened magnesium chelators and found that several—including citrate, isocitrate, and oxalate—could maintain the membrane stability of fatty acid vesicles in the presence of Mg2+. Citrate also allowed Mg2+-dependent RNA synthesis within protocell-like vesicles, while at the same time protecting RNA from Mg2+-catalyzed degradation. Efforts to recreate a prebiotically plausible protocell, in which RNA replication occurs within a fatty acid vesicle, have been stalled by the destabilizing effect of Mg2+ on fatty acid membranes. Here we report that the presence of citrate protects fatty acid membranes from the disruptive effects of high Mg2+ ion concentrations while allowing RNA copying to proceed, while also protecting single-stranded RNA from Mg2+-catalyzed degradation. This combination of properties has allowed us to demonstrate the chemical copying of RNA templates inside fatty acid vesicles, which in turn allows for an increase in copying efficiency by bathing the vesicles in a continuously refreshed solution of activated nucleotides. [1]: /lookup/doi/10.1126/science.1241888
UNTIL recently, when one thought of the varied molecular processes at the origin of life, one imagined that the first self-replicating systems consisted of both RNA and protein. RNA served to hold information, whereas protein molecules provided all the enzymic activities needed to make copies of RNA and to reproduce themselves. The cycle that developed a self-replicating system out of the primitive soup of amino acids and nucleotides had two radically different components.
Learn to play the ukulele at your own pace with our step-by-step approach featuring over 500 hours of video lessons from the best teachers in the world. Head Instructor Aldrine Guerrero will help you become the musician you want to be.
We asked editors and bloggers of Black Perspectives to select the best books published in 2020 on Black History, and they delivered! Check out this extraordinary list of great books from 2020 that offer varied historical perspectives on the Black experience in the United States and across the globe.
A good looking list. I’ve already got a few in my pile for the new year.
This is in the same sort of vein of an idea I’ve had knocking around for ages…
Welsh cakes are a traditional tea-time treat that are really easy to make. Eat them warm from the stove, or store in an airtight container for up to a week.
Walking the line between pancake and biscuit, these soft, tender cakes are studded with raisins and showered with cinnamon-sugar.
Frome offers a unique perspective on your favorite movies. The whole movie is condensed into scene colors and placed on a panoramic canvas. Perfect for all movie lovers and fits any home decor perfectly!
This is a cool looking thing.
History tells us how we got here. Hard Histories show us a way forward.
snarfed (GitHub)…tuned.
sigh
Silos gonna silo…
Waiting patiently to see what Snarfed and Aaronpk come up with next. Otherwise, time to quit Instagram…
The ergodic hypothesis is a key analytical device of equilibrium statistical mechanics. It underlies the assumption that the time average and the expectation value of an observable are the same. Where it is valid, dynamical descriptions can often be replaced with much simpler probabilistic ones — time is essentially eliminated from the models. The conditions for validity are restrictive, even more so for non-equilibrium systems. Economics typically deals with systems far from equilibrium — specifically with models of growth. It may therefore come as a surprise to learn that the prevailing formulations of economic theory — expected utility theory and its descendants — make an indiscriminate assumption of ergodicity. This is largely because foundational concepts to do with risk and randomness originated in seventeenth-century economics, predating by some 200 years the concept of ergodicity, which arose in nineteenth-century physics. In this Perspective, I argue that by carefully addressing the question of ergodicity, many puzzles besetting the current economic formalism are resolved in a natural and empirically testable way.
Italic Type is the simplest way to track your books, get trusted recommendations, and share the joy of reading with friends.
An interesting new competitor to Goodreads and Library Thing on the scene. The functionality is very limited in scope at present, but it’s rather pretty looking. Not nearly as fine grained as Goodreads in terms of data, but a good start.
I’ll have to look into the ease/value of starting into yet-another book silo though. I’d only really use it if I can get it to dovetail with posting to my own website as a syndication target (POSSE), or if I can use it to syndicate to my own site (PESOS).
Yorba is encrypted, secure and the last profile and login you’ll ever need. Verify and catalog all dimensions of you—across your personal and professional life.
ᔥ in #dev 2020-12-15 ()
Most opposition to abortion relies on the premise that the fetus is a human being, a person, from the moment of conception. The premise is argued for, but, as I think, not well. Take, for example, the most common argument. We are asked to notice that the development of a human being from conception through birth into childhood is continuous; then it is said that to draw a line, to choose a point in this development and say "before this point the thing is not a person, after this point it is a person" is to make an arbitrary choice, a choice for which in the nature of things no good reason can be given. It is concluded that the fetus is, or anyway that we had better say it is, a person from the moment of conception. But this conclusion does not follow. Similar things might be said about the development of an acorn into an oak trees, and it does not follow that acorns are oak trees, or that we had better say they are. Arguments of this form are sometimes called "slippery slope arguments"—the phrase is perhaps self explanatory—and it is dismaying that opponents of abortion rely on them so heavily and uncritically.