O ajuste fino de máquinas e sistemas moleculares: mero acaso, fortuita necessidade ou design inteligente?

terça-feira, junho 23, 2020

Journal of Theoretical Biology

Volume 501, 21 September 2020, 110352

Using statistical methods to model the fine-tuning of molecular machines and systems

Authors Steinar Thorvaldsen a Ola Hössjer b

Dep. of Education, University of Tromsø, Norway

b Stockholm University, Dep. of Mathematics, Division of Mathematical Statistics, Sweden

Received 6 July 2019, Revised 26 May 2020, Accepted 27 May 2020, Available online 4 June 2020.


• Statistical methods are appropriate for modelling fine-tuning.

• Fine-tuning is detected in functional proteins, cellular networks etc.

• Constants and initial conditions of nature are deliberately tuned.

• Statistical analysis of fine-tuning model some of the categories of design.

• Fine-tuning and design deserve attention in the scientific community.


Fine-tuning has received much attention in physics, and it states that the fundamental constants of physics are finely tuned to precise values for a rich chemistry and life permittance. It has not yet been applied in a broad manner to molecular biology. However, in this paper we argue that biological systems present fine-tuning at different levels, e.g. functional proteins, complex biochemical machines in living cells, and cellular networks. This paper describes molecular fine-tuning, how it can be used in biology, and how it challenges conventional Darwinian thinking. We also discuss the statistical methods underpinning fine-tuning and present a framework for such analysis.

Um padrão irregular de ampulheta descreve o ritmo do desenvolvimento fenotípico na evolução dos mamíferos placentários

segunda-feira, junho 15, 2020

An irregular hourglass pattern describes the tempo of phenotypic development in placental mammal evolution

Gerardo A. Cordero, Marcelo R. Sánchez-Villagra and Ingmar Werneburg


Organismal development is defined by progressive transformations that ultimately give rise to distinct tissues and organs. Thus, temporal shifts in ontogeny often reflect key phenotypic differences in phylogeny. Classical theory predicts that interspecific morphological divergence originates towards the end of embryonic or fetal life stages, i.e. the early conservation model. By contrast, the hourglass model predicts interspecific variation early and late in prenatal ontogeny, though with a phylogenetically similar mid-developmental period. This phylotypic period, however, remains challenging to define within large clades such as mammals. Thus, molecular and morphological tests on a mammalian hourglass have not been entirely congruent. Here, we report an hourglass-like pattern for mammalian developmental evolution. By comparing published data on the timing of 74 homologous characters across 51 placental species, we demonstrated that variation in the timing of development decreased late in embryogenesis––when organ formation is highly active. Evolutionary rates of characters related to this timeframe were lowest, coinciding with a phylotypic period that persisted well beyond the pharyngula ‘stage’. The trajectory culminated with elevated variation in a handful of fetal and perinatal characters, yielding an irregular hourglass pattern. Our study invites further quantification of ontogeny across diverse amniotes and thus challenges current ideas on the universality of developmental patterns.

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Evidência neurocientífica: mente irredutível (Parte 1)

Mais uma hipótese sobre a origem da vida: a partir do DNA e RNA

sexta-feira, junho 12, 2020

Selective prebiotic formation of RNA pyrimidine and DNA purine nucleosides

Jianfeng Xu, Václav Chmela, Nicholas J. Green, David A. Russell, Mikołaj J. Janicki, Robert W. Góra, Rafał Szabla, Andrew D. Bond & John D. Sutherland 

Nature volume 582, pages60–66(2020)


Published: 03 June 2020

Extended Data Fig. 1

The nature of the first genetic polymer is the subject of major debate 1. Although the ‘RNA world’ theory suggests that RNA was the first replicable information carrier of the prebiotic era—that is, prior to the dawn of life 2,3—other evidence implies that life may have started with a heterogeneous nucleic acid genetic system that included both RNA and DNA 4. Such a theory streamlines the eventual ‘genetic takeover’ of homogeneous DNA from RNA as the principal information-storage molecule, but requires a selective abiotic synthesis of both RNA and DNA building blocks in the same local primordial geochemical scenario. Here we demonstrate a high-yielding, completely stereo-, regio- and furanosyl-selective prebiotic synthesis of the purine deoxyribonucleosides: deoxyadenosine and deoxyinosine. Our synthesis uses key intermediates in the prebiotic synthesis of the canonical pyrimidine ribonucleosides (cytidine and uridine), and we show that, once generated, the pyrimidines persist throughout the synthesis of the purine deoxyribonucleosides, leading to a mixture of deoxyadenosine, deoxyinosine, cytidine and uridine. These results support the notion that purine deoxyribonucleosides and pyrimidine ribonucleosides may have coexisted before the emergence of life 5.

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