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Publication Date

Wed Dec 01 2021

Journal Name

Open Biology

Volume

11

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Structure and in silico simulations of a cold-active esterase reveals its prime cold-adaptation mechanism

Nehad

Husam Sabah

Samuel

Harley L.

Amira M.

Hesham

Ahmed

Christopher R.

Pierre J.

Stephen A.

D. Dafydd

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Here we determined the structure of a cold active family IV esterase (EstN7) cloned from Bacillus cohnii strain N1. EstN7 is a dimer with a classical α/β hydrolase fold. It has an acidic surface that is thought to play a role in cold-adaption by retaining solvation under changed water solvent entropy at lower temperatures. The conformation of the functionally important cap region is significantly different to EstN7's closest relatives, forming a bridge-like structure with reduced helical content providing greater access to the active site through more than one substrate access tunnel. However, dynamics do not appear to play a major role in cold adaption. Molecular dynamics at different temperatures, rigidity analysis, normal mode analysis and geometric simulations of motion confirm the flexibility of the cap region but suggest that the rest of the protein is largely rigid. Rigidity analysis indicates the distribution of hydrophobic tethers is appropriate to colder conditions, where the hydrophobic effect is weaker than in mesophilic conditions due to reduced water entropy. Thus, it is likely that increased substrate accessibility and tolerance to changes in water entropy are important for of EstN7's cold adaptation rather than changes in dynamics.

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Publication Date

Tue Jan 18 2022

Journal Name

Materials Science Forum

The Effect of Gamma Radiation on the Manufactured HgBa2Ca2Cu2.4Ag0.6O8+δ Compound

Gamma doses radiation

crystal size

strain

degree of crystallinity

Scherrer

crystallinity and Williamson equations.

zainab j

Balqees A.

Mohammed A.

Kareem A.

Auday H.

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In this article four samples of HgBa₂Ca₂Cu_2.4Ag_0.6O_8+δ were prepared and irradiated with different doses of gamma radiation 6, 8 and 10 Mrad. The effects of gamma irradiation on structure of HgBa₂Ca₂Cu_2.4Ag_0.6O_8+δ samples were characterized using X-ray diffraction. It was concluded that there effect on structure by gamma irradiation. Scherrer, crystallization, and Williamson equations were applied based on the X-ray diffraction diagram and for all gamma doses, to calculate crystal size, strain, and degree of crystallinity. I

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