Membrane Phase Changes in Chilling-Sensitive Vigna radiata and Their Significance to Growth

1976 ◽  
Vol 3 (3) ◽  
pp. 291 ◽  
Author(s):  
JK Raison ◽  
EA Chapman
Keyword(s):  
Membrane Lipids ◽  
Phase Changes ◽  
Resonance Spectroscopy ◽  
Functional Changes ◽  
Molecular Ordering ◽  
Spin Resonance ◽  
Bean Hypocotyl ◽  
Precise Relationship ◽  
Succinate Oxidase ◽  
Mung Bean Hypocotyl

Changes in the growth response of mung bean hypocotyl were studied as a function of temperature and related to structural and functional changes in membranes. The temperature coefficient for growth increased abruptly below 28°C and again below 15°C. The Arrhenius activation energy of mitochondrial succinate oxidase also increased below these same temperatures. Changes in molecular ordering were detected in the membrane lipids of both mitochondria and chloroplasts at about 28 and 15°C by electron spin resonance spectroscopy. The results demonstrate a precise relationship between changes in the molecular ordering of membrane lipids and the physiological response of plants to changes in temperature.

Effect of Various Sterols on the 22Na Permeability and Fluidity of Phospholipid Bilayer Membranes

1975 ◽  
Vol 53 (6) ◽  
pp. 1065-1071 ◽  
Author(s):  
M. A. Singer ◽  
J. K. S. Wan
Keyword(s):  
Spin Label ◽  
Membrane Lipids ◽  
Hydrocarbon Chain ◽  
Phospholipid Bilayer ◽  
Poor Correlation ◽  
Resonance Spectroscopy ◽  
Sodium Permeability ◽  
Spin Resonance ◽  
Multilamellar Liposomes ◽  
Series Of Experiments

Sodium-22 efflux was measured in multilamellar liposomes composed of egg lecithin, dicetylphosphate, and various sterols. In a parallel series of experiments a spin labelled fatty acid ester was incorporated into similar vesicles and the molecular motion of the spin label monitored by electron spin resonance spectroscopy. Spin label mobility was used as a measure of phospholipid hydrocarbon chain motion. There was a poor correlation between the effects of these sterols on sodium permeability and their effects on the motion of the lipid chains. It is postulated that sterols alter sodium transport not only through a reduction in the motional freedom of membrane lipids, but also through changes in the partitioning of sodium between membrane and aqueous phases.

scholarly journals Tuning flavin environment to detect and control light-induced conformational switching in Drosophila cryptochrome

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Siddarth Chandrasekaran ◽  
Connor M. Schneps ◽  
Robert Dunleavy ◽  
Changfan Lin ◽  
Cristina C. DeOliveira ◽  
...  
Keyword(s):  
Side Reactions ◽  
Resonance Spectroscopy ◽  
Conformational Switching ◽  
Spin Resonance ◽  
Degradation Activity ◽  
Recognition Motifs ◽  
Cellular Turnover ◽  
Control Light ◽  
Dynamics Simulations ◽  
And Control

AbstractLight-induction of an anionic semiquinone (SQ) flavin radical in Drosophila cryptochrome (dCRY) alters the dCRY conformation to promote binding and degradation of the circadian clock protein Timeless (TIM). Specific peptide ligation with sortase A attaches a nitroxide spin-probe to the dCRY C-terminal tail (CTT) while avoiding deleterious side reactions. Pulse dipolar electron-spin resonance spectroscopy from the CTT nitroxide to the SQ shows that flavin photoreduction shifts the CTT ~1 nm and increases its motion, without causing full displacement from the protein. dCRY engineered to form the neutral SQ serves as a dark-state proxy to reveal that the CTT remains docked when the flavin ring is reduced but uncharged. Substitutions of flavin-proximal His378 promote CTT undocking in the dark or diminish undocking in the light, consistent with molecular dynamics simulations and TIM degradation activity. The His378 variants inform on recognition motifs for dCRY cellular turnover and strategies for developing optogenetic tools.

scholarly journals Environmentally persistent free radicals are ubiquitous in wildfire charcoals and remain stable for years

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Gabriel Sigmund ◽  
Cristina Santín ◽  
Marc Pignitter ◽  
Nathalie Tepe ◽  
Stefan H. Doerr ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Free Radicals ◽  
Reactive Oxygen ◽  
Resonance Spectroscopy ◽  
Oxygen Species ◽  
Pyrogenic Carbon ◽  
Spin Resonance ◽  
Long Time ◽  
High Concentrations

AbstractGlobally landscape fires produce about 256 Tg of pyrogenic carbon or charcoal each year. The role of charcoal as a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species, is poorly constrained. Here, we analyse 60 charcoal samples collected from 10 wildfires, that include crown as well as surface fires in forest, shrubland and grassland spanning different boreal, temperate, subtropical and tropical climate. Using electron spin resonance spectroscopy, we measure high concentrations of environmentally persistent free radicals in charcoal samples, much higher than those found in soils. Concentrations increased with degree of carbonization and woody fuels favoured higher concentrations. Moreover, environmentally persistent free radicals remained stable for an unexpectedly long time of at least 5 years. We suggest that wildfire charcoal is an important global source of environmentally persistent free radicals, and therefore potentially of harmful reactive oxygen species.

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