Um código universal impulsiona a formação de todas as membranas celulares?

Membranes are functionalized by a proteolipid code

Troy A. Kervin & Michael Overduin

BMC Biology volume 22, Article number: 46 (2024)

 

Abstract

Membranes are protein and lipid structures that surround cells and other biological compartments. We present a conceptual model wherein all membranes are organized into structural and functional zones. The assembly of zones such as receptor clusters, protein-coated pits, lamellipodia, cell junctions, and membrane fusion sites is explained to occur through a protein-lipid code. This challenges the theory that lipids sort proteins after forming stable membrane subregions independently of proteins.

FREE PDF GRATIS: BMC Biology

Efeitos magnéticos na origem da vida?

Enantioselective Adsorption on Magnetic Surfaces

Mohammad Reza Safari, Frank Matthes, Vasile Caciuc, Nicolae Atodiresei, Claus M. Schneider, Karl-Heinz Ernst, Daniel E. Bürgler

First published: 28 December 2023
https://doi.org/10.1002/adma.202308666

 

 Credit: Advanced Materials (2023). DOI: 10.1002/adma.202308666

Abstract

From the beginning of molecular theory, the interplay of chirality and magnetism has intrigued scientists. There is still the question if enantiospecific adsorption of chiral molecules occurs on magnetic surfaces. Enantiomer discrimination was conjectured to arise from chirality-induced spin separation within the molecules and exchange interaction with the substrate's magnetization. Here, it is shown that single helical aromatic hydrocarbons undergo enantioselective adsorption on ferromagnetic cobalt surfaces. Spin and chirality sensitive scanning tunneling microscopy reveals that molecules of opposite handedness prefer adsorption onto cobalt islands with opposite out-of-plane magnetization. As mobility ceases in the final chemisorbed state, it is concluded that enantioselection must occur in a physisorbed transient precursor state. State-of-the-art spin-resolved ab initio simulations support this scenario by refuting enantio-dependent chemisorption energies. These findings demonstrate that van der Waals interaction should also include spin-fluctuations which are crucial for molecular magnetochiral processes.
 

FREE PDF GRATIS: Advanced Materials

Darwin, nós temos um problema: como causa necessária para a evolução biológica a autorreplicação fenotípica deve ser exata.

Biosystems
Volume 237, March 2024, 105154

Accurate phenotypic self-replication as a necessary cause for biological evolution.

Seymour Garte 

Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, 160 Frelinghuysen Road, Piscataway, NJ, 08854-8020, USA

Received 27 October 2023, Revised 29 January 2024, Accepted 9 February 2024, Available online 10 February 2024, Version of Record 14 February 2024.

 

Image/Imagem:
Adamski, P., Eleveld, M., Sood, A. et al. From self-replication to replicator systems en route tode novo life. Nat Rev Chem 4, 386–403 (2020). https://doi.org/10.1038/s41570-020-0196-x

Abstract

Since the Origin of Species, it has been known that evolution depends on what Darwin called the “strong principle of inheritance.” Highly accurate replication of cellular phenotype is a universal phenomenon in all of life since LUCA and is often taken for granted as a constant in evolutionary theory. It is not known how self-replication arose during the origin of life. In this report I use the simple mathematics of evolutionary theory to investigate the dynamics of self-replication accuracy and allelic selection. Results indicate that the degree of self-replication accuracy must be greater than a threshold related to the selection coefficients of the alleles in a population in order for evolution to occur. Accurate replication of cellular phenotype and of the molecules involved in genotype/phenotype linkage is necessary for the origin of evolution and may be considered the fundamental principle of life.

Payment or subscription needed/Requer assinatura ou pagamento: Biosystems

 

O Google Scholar é manipulável???

Google Scholar is manipulatable
Hazem Ibrahim, Fengyuan Liu, Yasir Zaki, Talal Rahwan

 

Image/Imagem - ThriveWorks

Citations are widely considered in scientists' evaluation. As such, scientists may be incentivized to inflate their citation counts. While previous literature has examined self-citations and citation cartels, it remains unclear whether scientists can purchase citations. Here, we compile a dataset of ~1.6 million profiles on Google Scholar to examine instances of citation fraud on the platform. We survey faculty at highly-ranked universities, and confirm that Google Scholar is widely used when evaluating scientists. Intrigued by a citation-boosting service that we unravelled during our investigation, we contacted the service while undercover as a fictional author, and managed to purchase 50 citations. These findings provide conclusive evidence that citations can be bought in bulk, and highlight the need to look beyond citation counts.

Subjects:     Computational Engineering, Finance, and Science (cs.CE); Digital Libraries (cs.DL); Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)
Cite as:     arXiv:2402.04607 [Add to Citavi project by ArXiv ID] [cs.CE]

 FREE PDF GRATIS: arXiv

Como os sistemas moleculares na origem da vida podem ter evoluído

Design and Thermodynamics Principles to Program the Cooperativity of Molecular Assemblies
 

Dominic Lauzon, Prof. Alexis Vallée-Bélisle
 

First published: 17 November 2023
https://doi.org/10.1002/anie.202313944

 

 Abstract

Most functional nanosystems in living organisms are constructed using multimeric assemblies that provide multiple advantages over their monomeric counterparts such as cooperative or anti-cooperative responses, integration of multiple signals and self-regulation. Inspired by these natural nanosystems, chemists have been synthesizing self-assembled supramolecular systems over the last 50 years with increasing complexity with applications ranging from biosensing, drug delivery, synthetic biology, and system chemistry. Although many advances have been made concerning the design principles of novel molecular architectures and chemistries, little is still known, however, about how to program their dynamic of assembly so that they can assemble at the required concentration and with the right sensitivity. Here, we used synthetic DNA assemblies and double-mutant cycle analysis to explore the thermodynamic basis to program the cooperativity of molecular assemblies. The results presented here exemplify how programmable molecular assemblies can be efficiently built by fusing interacting domains and optimizing their compaction. They may also provide the rational basis for understanding the thermodynamic and mechanistic principles driving the evolution of multimeric biological complexes.

FREE PDF GRATIS: Angewandte Chemie Intl Edition

Ciência objetiva ou consenso científico como arma contra opiniões diferentes?

Prosocial motives underlie scientific censorship by scientists: A perspective and research agenda
 

Cory J. Clark cjclark@sas.upenn.edu, Lee Jussim, Komi Frey, +35 , and William von Hippel 

Edited by Timothy Wilson, University of Virginia, Charlottesville, VA; received February 25, 2023; accepted October 6, 2023 November 20, 2023 120 (48) e2301642120
https://doi.org/10.1073/pnas.2301642120

 

Image credit: cartoonist Ramirez of the Weekly Standard, 

via http://www.ibdeditorials.com/cartoons.

Abstract
 

Science is among humanity’s greatest achievements, yet scientific censorship is rarely studied empirically. We explore the social, psychological, and institutional causes and consequences of scientific censorship (defined as actions aimed at obstructing particular scientific ideas from reaching an audience for reasons other than low scientific quality). Popular narratives suggest that scientific censorship is driven by authoritarian officials with dark motives, such as dogmatism and intolerance. Our analysis suggests that scientific censorship is often driven by scientists, who are primarily motivated by self-protection, benevolence toward peer scholars, and prosocial concerns for the well-being of human social groups. This perspective helps explain both recent findings on scientific censorship and recent changes to scientific institutions, such as the use of harm-based criteria to evaluate research. We discuss unknowns surrounding the consequences of censorship and provide recommendations for improving transparency and accountability in scientific decision-making to enable the exploration of these unknowns. The benefits of censorship may sometimes outweigh costs. However, until costs and benefits are examined empirically, scholars on opposing sides of ongoing debates are left to quarrel based on competing values, assumptions, and intuitions.

FREE PDF GRATIS: PNAS

Como surgiu a vida na Terra?

Organic hazes as a source of life's building blocks to warm little ponds on the Hadean Earth
Ben K. D. Pearce, Sarah M Hörst, Joshua A. Sebree, Chao He

 

 Image/Imagem: Smithsonian Magazine

Abstract

Over 4 billion years ago, Earth is thought to have been a hazy world akin to Saturn's moon Titan. The organic hazes in the atmosphere at this time could contain a vast inventory of life's building blocks, and thus may have seeded warm little ponds for life. In this work, we produce organic hazes in the lab in atmospheres with high (5%) and low (0.5%) CH4 abundances and analyze the solid particles for nucleobases, amino acids, and a few other organics using GC/MS/MS to obtain their concentrations. We also analyze heated (200 ∘C) samples from the high methane organic haze experiment to simulate these particles sitting on an uninhabitable surface. Finally, we use our experimental results and estimates of atmospheric haze production as inputs for a comprehensive numerical pond model to calculate the concentrations of nucleobases from organic hazes in these environments. We find that organic hazes typically provide up to 0.2-6.5 μM concentrations of nucleobases to warm little ponds for potentially habitable Hadean conditions. However, without seepage, uracil and thymine can reach ~100 μM concentrations, which is the present lower experimental limit to react these species to form nucleotides. Heating samples leads to partial or complete decay of biomolecules, suggesting that biomolecule stockpiling on the hot surface is unlikely. The ideal conditions for the delivery of life's building blocks from organic hazes would be when the Hadean atmosphere is rich in methane, but not so rich as to create an uninhabitable surface.

FREE PDF: arXiv