Correlation between the coefficient of the temperature shift of the frequency of the nonplanar vibration and the length of the hydrogen bond in a crystal

Photoswitching of phytochrome photoreceptors between red-absorbing (Pr) and far-red absorbing (Pfr) states triggers light adaptation of plants, bacteria and other organisms. Using quantum chemistry, we elucidate the color-tuning mechanism of phytochromes and identify the origin of the Pfr-state red-shifted spectrum. Spectral variations are explained by resonance interactions of the protonated linear tetrapyrrole chromophore. In particular, hydrogen bonding of pyrrole ring D with the strictly conserved aspartate shifts the positive charge towards ring D thereby inducing the red spectral shift. Our MD simulations demonstrate that formation of the ring D–aspartate hydrogen bond depends on interactions between the chromophore binding domain (CBD) and phytochrome specific domain (PHY). Our study guides rational engineering of fluorescent phytochromes with a far-red shifted spectrum.

Probing the Structural Features and the Micro-heterogeneity of Various Deep Eutectic Solvents and their Water Dilutions by the Photophysical Behaviour of Two Fluorophores

10.26434/chemrxiv.13395683.v1 ◽

2020 ◽

Author(s):

Matteo Tiecco ◽

Irene Di Guida ◽

Pier Luigi Gentili ◽

Raimondo Germani ◽

Carmela Bonaccorso ◽

...

Keyword(s):

Hydrogen Bond ◽

Transient Absorption ◽

Photophysical Properties ◽

Deep Eutectic Solvents ◽

Structural Features ◽

Solvation Dynamics ◽

Structured Systems ◽

Reduced Viscosity ◽

Bond Network ◽

Fluorescent Molecules

<div><div><div><p>The structural features of a series of diverse Deep Eutectic Solvents (DESs) have been investigated and characterized by means of two fluorescent probes. The spectral and photophysical properties of the latter are strictly dependent on the experienced environment, so that they can provide insights into the polarity, viscosity, hydrogen-bond network, and micro-heterogeneity of the various DESs.</p><p>In fact, the investigated DESs exhibit a variety of properties with regards to their hydrophilicity, acidity, and hydrogen-bond ability, and these details were deeply probed by the two fluorescent molecules. The effect of the addition of water, which is a key strategy for tuning the properties of these structured systems, was also tested. In particular, the excited state dynamics of the probes, measured by femtosecond-resolved transient absorption, proved instrumental in understanding the changes in the structural properties of the DESs, namely reduced viscosity and enhanced heterogeneity, as the water percentage increases. Differences between the various DESs in terms of both local microheterogeneity and bulk viscosity also emerged from the peculiar multi-exponential solvation dynamics undergone by the excited states of the probes.</p></div></div></div>

Probing the Structural Features and the Micro-heterogeneity of Various Deep Eutectic Solvents and their Water Dilutions by the Photophysical Behaviour of Two Fluorophores

10.26434/chemrxiv.13395683 ◽

2020 ◽

Author(s):

Matteo Tiecco ◽

Irene Di Guida ◽

Pier Luigi Gentili ◽

Raimondo Germani ◽

Carmela Bonaccorso ◽

...

Keyword(s):

Hydrogen Bond ◽

Transient Absorption ◽

Photophysical Properties ◽

Deep Eutectic Solvents ◽

Structural Features ◽

Solvation Dynamics ◽

Structured Systems ◽

Reduced Viscosity ◽

Bond Network ◽

Fluorescent Molecules

<div><div><div><p>The structural features of a series of diverse Deep Eutectic Solvents (DESs) have been investigated and characterized by means of two fluorescent probes. The spectral and photophysical properties of the latter are strictly dependent on the experienced environment, so that they can provide insights into the polarity, viscosity, hydrogen-bond network, and micro-heterogeneity of the various DESs.</p><p>In fact, the investigated DESs exhibit a variety of properties with regards to their hydrophilicity, acidity, and hydrogen-bond ability, and these details were deeply probed by the two fluorescent molecules. The effect of the addition of water, which is a key strategy for tuning the properties of these structured systems, was also tested. In particular, the excited state dynamics of the probes, measured by femtosecond-resolved transient absorption, proved instrumental in understanding the changes in the structural properties of the DESs, namely reduced viscosity and enhanced heterogeneity, as the water percentage increases. Differences between the various DESs in terms of both local microheterogeneity and bulk viscosity also emerged from the peculiar multi-exponential solvation dynamics undergone by the excited states of the probes.</p></div></div></div>

Competition between the intramolecular hydrogen bond and the π-electron delocalization in some RAHB systems: A theoretical study

Журнал структурной химии ◽

10.26902/jsc_id40420 ◽

2019 ◽

Vol 60 (5) ◽

Keyword(s):

Hydrogen Bond ◽

Intramolecular Hydrogen Bond ◽

Theoretical Study ◽

Electron Delocalization ◽

Intramolecular Hydrogen

Fabrication and study the effect of the laser on the properties of the compound Tl2-xHgxBa2-ySryCa2Cu3O10+δ superconductor

Ibn AL- Haitham Journal For Pure and Applied Science ◽

10.30526/2017.ihsciconf.1789 ◽

2018 ◽

pp. 168

Author(s):

A. Kareem Dahash Ali ◽

Nihad Ali Shafeek

Keyword(s):

Transition Temperature ◽

Solid State ◽

Hydrostatic Pressure ◽

Electrical Properties ◽

Co2 Laser ◽

Temperature Shift ◽

Unit Cell ◽

X Ray Diffraction ◽

X Ray ◽

Structural And Electrical Properties

This study included the fabrication of compound (Tl2-xHgxBa2-ySryCa2Cu3O10+δ) in a manner solid state and under hydrostatic pressure ( 8 ton/cm2) and temperature annealing(850°C), and determine the effect of the laser on the structural and electrical properties elements in the compound, and various concentrations of x where (x= 0.1,0.2,0.3 ). Observed by testing the XRD The best ratio of compensation for x is 0.2 as the value of a = b = 5.3899 (A °), c = 36.21 (A °) show that the installation of four-wheel-based type and that the best temperature shift is TC= 142 K .When you shine a CO2 laser on the models in order to recognize the effect of the laser on these models showed the study of X-ray diffraction of these samples when preparing models with different concentrations of the values of x, the best ratio of compensation is 0.2 which showed an increase in the values of the dimensions of the unit cell a=b = 5.3929 (A °), c = 36.238 (A°). And the best transition temperature after shedding laser is TC=144 K.