Marie-Christine Maurel "Life as a concept and as a material subject"
参考：彼女の講演 "Le passage du non vivant au vivant" 「無生物から生物への道」 （ビデオ1, 2）
phusis (la nature) vs nomos (the law)
The title of the symposium is in itself antinomic, because "definition" introduces a frame, a law, a convention, but "life" is full of dynamism and cannot be trapped.
In the Webster, 20 definitions:
● vital vs dead
● vitalism
●● growth, reaction to stimuli, reproduction, metabolism
questions to be asked:
● of what is composed
● from where
● how it was formed
● how it is transmitted
● what is an ancient form
● other life forms in the planets
4.5 Ga : H, C, N, O, S, P
3.6 Ga : birth of cell
topdown approach : comparative biochem
H, C, N, S, P, → CH2, CO2, CO, H2O,,, → biopolymer, peptide,, → living system → → today
bottom-up approach : evolutionary biochem
today → → → Archaea, Bacteria, Eucarya
Molecules of life
(1) synthesis of building blocks
(2) clays, metal sulfurs from hot springs may help
peptide synthesis supplied by CO underhot aqueous condition in the presence of (Fe, Ni)S
conditions for life
1) autopoiesis (Humberto Maturana and Francisco Varela in 1973)
2) self-organization / complexity
3) dorwinian evolution
# problem of complexity; physical system can be complex
Belousov-Zhabotinsky (BZ) reaction (video)
Life is characterized by a dualism (Salvador Luria)
material nature of life : historical nature of evolution
Erwin Schrödinger
laws of physics cannot be applied; must develop a new law
Systemic approach : total is more than sum of parts
autopoiesis, self organization, emergence, complexity, holism
Albert Szent-Györgyi : The living state (1972, AP)
Life has developed its process gradually, never rejecting what it has built
RNA world hypothesis and facts
early evolution; RNA replication
current RNA is fossil of ancient RNA ?
biomolecules are historical structures>
Molecular biology: evolution を in vitro で解析
RNAだけで存在したのか？
viroid = naked RNA at the boundary of life
246-574 bp
no envelop, capsids
not protein-coding
resistant to high temperature, extreme pH, high pressure
free in nature
living fossil ?
RNA viruses = continuum from RNA world to viroids, viruses, cells
prebiotic world : accumulation of materials
aa, peptides, nitrogenous bases, sugar ..., water, clays, minerals
↓
strates of life : phenotypic diversity, ecological niches
RNA world
free RNAs
pro-viroids
proto cell
↓
O2
↓
naked RNA → viroids
RNA → virus : cell (pro prokaryote?)
↓
acquisition of intercellular mode of life
DNA/RNA world
endo symbiosis → chloroplasts
prion not mentioned;
protein can transmit morphological changes upon contact (no transfer of information)
Aucun commentaire:
Enregistrer un commentaire