Direct observation of an optically-active carbonium ion and measurement of the free-energy barrier to racemisation

1973 ◽  
pp. 182 ◽  
Author(s):  
T. Derrick Turbitt ◽  
William E. Watts
Keyword(s):  
Free Energy ◽  
Direct Observation ◽  
Energy Barrier ◽  
Optically Active ◽  
Free Energy Barrier ◽  
Carbonium Ion

DFT study on the hydrolysis of metsulfuron-methyl: A sulfonylurea herbicide

2018 ◽  
Vol 17 (08) ◽  
pp. 1850050 ◽  
Author(s):  
Qiuhan Luo ◽  
Gang Li ◽  
Junping Xiao ◽  
Chunhui Yin ◽  
Yahui He ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Carbonyl Group ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Metsulfuron Methyl ◽  
Catalytic Role ◽  
Hydrolysis Of

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

COMPARING FOLDING MECHANISMS OF DIFFERENT PRION PROTEINS BY Gō MODEL

2013 ◽  
Vol 12 (08) ◽  
pp. 1341004
Author(s):  
XUE WU ◽  
TING FU ◽  
ZHI-LONG XIU ◽  
LIU YIN ◽  
JIN-GUANG WANG ◽  
...  
Keyword(s):  
Free Energy ◽  
Prion Protein ◽  
Energy Barrier ◽  
Prion Proteins ◽  
Coarse Grained ◽  
Transmissible Spongiform Encephalopathies ◽  
Free Energy Barrier ◽  
Spongiform Encephalopathies ◽  
Go Model ◽  
Folding Free Energy

Prions are associated with neurodegenerative diseases induced by transmissible spongiform encephalopathies. The infectious scrapie form is referred to as PrP Sc , which has conformational change from normal prion with predominant α-helical conformation to the abnormal PrP Sc that is rich in β-sheet content. Neurodegenerative diseases have been found from both human and bovine sources, but there are no reports about infected by transmissible spongiform encephalopathies from rabbit, canine and horse sources. Here we used coarse-grained Gō model to compare the difference among human, bovine, rabbit, canine, and horse normal (cellular) prion proteins. The denatured state of normal prion has relation with the conversion from normal to abnormal prion protein, so we used all-atom Gō model to investigate the folding pathway and energy landscape for human prion protein. Through using coarse-grained Gō model, the cooperativity of the five prion proteins was characterized in terms of calorimetric criterion, sigmoidal transition, and free-energy profile. The rabbit and horse prion proteins have higher folding free-energy barrier and cooperativity, and canine prion protein has slightly higher folding free-energy barrier comparing with human and bovine prion proteins. The results from all-atom Gō model confirmed the validity of C α-Gō model. The correlations of our results with previous experimental and theoretical researches were discussed.

Elucidating the role of solvents in acid catalyzed dehydration of biorenewable hydroxy-lactones

2020 ◽  
Vol 5 (4) ◽  
pp. 651-662 ◽  
Author(s):  
Gourav Shrivastav ◽  
Tuhin S. Khan ◽  
Manish Agarwal ◽  
M. Ali Haider
Keyword(s):  
Free Energy ◽  
Transition State ◽  
Energy Barrier ◽  
Free Energy Barrier ◽  
Activation Free Energy ◽  
Acid Catalyzed

Utilizing the differential stabilization of reactant and transition state in the polar and apolar solvents to lower the activation free energy barrier for acid-catalyzed dehydration of hydroxy lactones.

scholarly journals Free-Energy Barrier at Droplet Condensation

2010 ◽  
Vol 184 ◽  
pp. 400-414 ◽  
Author(s):  
Andreas Nußbaumer ◽  
Elmar Bittner ◽  
Wolfhard Janke
Keyword(s):  
Free Energy ◽  
Energy Barrier ◽  
Free Energy Barrier ◽  
Droplet Condensation

scholarly journals The extent of protein hydration dictates the preference for heterogeneous or homogeneous nucleation generating either parallel or antiparallel β-sheet α-synuclein aggregates

2020 ◽  
Vol 11 (43) ◽  
pp. 11902-11914 ◽  
Author(s):  
José D. Camino ◽  
Pablo Gracia ◽  
Serene W. Chen ◽  
Jesús Sot ◽  
Igor de la Arada ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Activity ◽  
Energy Barrier ◽  
Homogeneous Nucleation ◽  
Protein Hydration ◽  
Free Energy Barrier ◽  
Β Sheet

The extent of protein hydration modulates the free energy barrier of both heterogeneous and homogeneous α-synuclein nucleation, leading to the formation of distinct amyloid polymorphs depending on the water activity of the protein microenvironment.

scholarly journals A Free Energy Barrier Caused by the Refolding of an Oligomeric Intermediate Controls the Lag Time of Amyloid Formation by hIAPP

2017 ◽  
Vol 139 (46) ◽  
pp. 16748-16758 ◽  
Author(s):  
Arnaldo L. Serrano ◽  
Justin P. Lomont ◽  
Ling-Hsien Tu ◽  
Daniel P. Raleigh ◽  
Martin T. Zanni
Keyword(s):  
Free Energy ◽  
Energy Barrier ◽  
Lag Time ◽  
Amyloid Formation ◽  
Free Energy Barrier
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