Light and life III

Delbrück, Max

doi:10.1007/bf02906138

Cited by 27 publications

(11 citation statements)

References 33 publications

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“…A more pertinent question, given the microbial dominance of life on earth, is not so much organ development which remarkably is regulated by genes like Pax-6 conserved from fruit flies to mammals, but on the origins of the first photosensory proteins. It is striking that only a small number of chemical chromophores participate in photosensing (Delbrück, 1976), with their binding domains derived independently in some cases like the flavins. One can hypothesize how gene fusion events brought about a photosensor if the two genes encoded a regulator and a protein that interacted with a chromophore.…”

Section: Concluding Comments On the Evolution Of Vision In Fungimentioning

confidence: 99%

A glimpse into the basis of vision in the kingdom Mycota

Idnurm

Verma

Corrochano

2010

Fungal Genetics and Biology

156

141

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Virtually all organisms exposed to light are capable of sensing this environmental signal. In recent years the photoreceptors that mediate the ability of fungi to "see" have been identified in diverse species, and increasingly characterized. The small sizes of fungal genomes and ease in genetic and molecular biology manipulations make this kingdom ideal amongst the eukaryotes for understanding photosensing. The most widespread and conserved photosensory protein in the fungi is White collar 1 (WC-1), a flavin-binding photoreceptor that functions with WC-2 as a transcription factor complex. Other photosensory proteins in fungi include opsins, phytochromes and cryptochromes whose roles in fungal photobiology are not fully resolved and their distribution in the fungi requires further taxon sampling. Additional unknown photoreceptors await discovery. This review discusses the effects of light on fungi and the evolutionary processes that may have shaped the ability of species to sense and respond to this signal.

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Section: Concluding Comments On the Evolution Of Vision In Fungimentioning

confidence: 99%

A glimpse into the basis of vision in the kingdom Mycota

Idnurm

Verma

Corrochano

2010

Fungal Genetics and Biology

156

141

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“…The chromophore is viewed here js a means of achieving charge separation photochemically while ensuring that both the forward and reverse thermal reactions are suitably slow. Delbruck (38) has recently pointed out that chlorophyll makes use of its rigidity to achieve rapid transfer of an electron and to preclude back reaction while retinal and other flexible chromophores such as phytochrome function by imposing a conformational change on the protein. We believe our model now extends these concepts by emphasizing the common goal of both types of systems, which is to generate the separation of charge.…”

Section: Discussionmentioning

confidence: 99%

Photoisomerization, energy storage, and charge separation: A model for light energy transduction in visual pigments and bacteriorhodopsin

Ebrey¹,

Callender²,

Dinur³

et al. 1979

Proc. Natl. Acad. Sci. U.S.A.

279

184

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Visual pigments are a class of proteins found in the membranes of photoreceptor cells (for reviews, see refs. 1 and 2). Their chromophoric unit is 11-cis-retinal covalently bound in the form of a Schiff base to the c-amino group of a lysine. The absorption of a photon by a visual pigment initiates a sequence of biochemical events that eventually lead to the generation of a neural signal by a photoreceptor cell. The identity of the primary photochemical event has been a subject of considerable interest and controversy. It was originally suggested that the primary event was an isomerization of the chromophore from its 1 1-cis to an all-trans conformation (3, 4). The strongest evidence favoring this mechanism was the observation (based on spectral data at low temperature) that an artificial pigment containing a 9-cis chromophore had the same photoproduct as rhodopsin itself. It was quite reasonably concluded that the most plausible common photoproduct formed from the two cis isomers is a trans isomer. A number of picosecond absorption studies of the primary event have raised widespread doubts as to the validity of the original model. It was found (5) that the primary event is complete in less than a few picoseconds at room temperature, and it was argued that this is too short a time for isomerization to occur [although other picosecond studies have reached the opposite conclusion (6)]. More recent evidence has come from the observation that at low temperature the rate of the process is significantly inhibited by deuterium replacement of the exchangeable protons on the pigment (7). Since only one proton on the chromophore is exchangeable, it is unlikely that this would have a measurable effect on the rate of isomerization. The picosecond measurements have generated numerous models (7-11) whose major feature is a photochemical proton transfer followed by a thermal cis-trans isomerization that occurs at a later stage. However, the original evidence upon which the suggestion of a cis-trans isomerization was originally based has never been discredited and, thus, it appears necessary to find a molecular model that is consistent with the entire body of available evidence. The purpose of this paper is to present such a model.There are, in fact, a fairly large number of observations that can be used in the construction and evaluation of alternative models. For example, we have shown, by using simple thermodynamic arguments, that a significant fraction of the photon's energy is "stored" in the primary photoproduct (12). Clearly a mechanism for energy storage must be an important component of any model that is proposed. Another energetic constraint may be derived from psychophysical and electrophysiological measurements of the level of thermal noise in photoreceptor cells. We show below that these observations may be interpreted directly in molecular terms and that they require an unusually high thermal activation energy for the primary event that appears to be inconsistent with many of the models that have been proposed.The ...

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“…In 1937 Delbrück migrated to the USA and also “migrated” from physics to biology (Leyla et al, 2015 , p. 243). Delbrück attended Bohr’s conference on Light and Life , and often acknowledged that Bohr played a part in his choice to devote himself to biology (Delbrück, 1949 , 1963 and, 1976 ; see also Kay, 1992 ; McKaughan, 2005 ; Leyla et al, 2015 , p. 243). Several years later, Delbrück remembered that the ultimate effect of Bohr’s lecture was to change the course of his life (Delbrück, 1976 ).…”

Section: Ageno’s Encounter With Schrödingermentioning

confidence: 99%

Mario Ageno and the status of biophysics

Cozzoli

2024

HPLS

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This essay focuses on Mario Ageno (1915–1992), initially director of the physics laboratory of the Italian National Institute of Health and later professor of biophysics at Sapienza University of Rome. A physicist by training, Ageno became interested in explaining the special characteristics of living organisms origin of life by means of quantum mechanics after reading a book by Schrödinger, who argued that quantum mechanics was consistent with life but that new physical principles must be found. Ageno turned Schrödinger’s view into a long-term research project. He aimed to translate Schrödinger’s ideas into an experimental programme by building a physical model for at least a very simple living organism. The model should explain the transition from the non-living to the living. His research, however, did not lead to the expected results, and in the 1980s and the 1990s he focused on its epistemological aspect, thinking over the tension between the lawlike structure of physics and the historical nature of biology. His reflections led him to focus on the nature of the theory of evolution and its broader scientific meaning.

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Light and life III

Cited by 27 publications

References 33 publications

A glimpse into the basis of vision in the kingdom Mycota

A glimpse into the basis of vision in the kingdom Mycota

Photoisomerization, energy storage, and charge separation: A model for light energy transduction in visual pigments and bacteriorhodopsin

Mario Ageno and the status of biophysics

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