Why do the Togni reagent and some of its derivatives exist in the high-energy hypervalent iodine form? New insight into the origins of their kinetic stability

2017 ◽  
Vol 19 (48) ◽  
pp. 32179-32183 ◽  
Author(s):  
Shungo Koichi ◽  
Benjamin Leuthold ◽  
Hans P. Lüthi
Keyword(s):  
Transition State ◽  
Thermodynamic Stability ◽  
High Energy ◽  
Kinetic Stability ◽  
Hypervalent Iodine ◽  
Insight Into

A scheme for the prediction of the kinetic and thermodynamic stability of Togni-type reagents is presented. The scheme is evaluated based on computations of the isomerization and transition state energies of an array of more than 600 compounds.

Structural insight into the rearrangement of the switch I region in GTP-bound G12A K-Ras

2017 ◽  
Vol 73 (12) ◽  
pp. 970-984 ◽  
Author(s):  
Shenyuan Xu ◽  
Brian N. Long ◽  
Gabriel H. Boris ◽  
Anqi Chen ◽  
Shuisong Ni ◽  
...  
Keyword(s):  
Transition State ◽  
Binding Pocket ◽  
High Energy ◽  
Side Chain ◽  
Conformation Change ◽  
Gtp Hydrolysis ◽  
Structural Insight ◽  
Hydrolysis Of ◽  
Insight Into ◽  
Intrinsic Gtpase Activity

K-Ras, a molecular switch that regulates cell growth, apoptosis and metabolism, is activated when it undergoes a conformation change upon binding GTP and is deactivated following the hydrolysis of GTP to GDP. Hydrolysis of GTP in water is accelerated by coordination to K-Ras, where GTP adopts a high-energy conformation approaching the transition state. The G12A mutation reduces intrinsic K-Ras GTP hydrolysis by an unexplained mechanism. Here, crystal structures of G12A K-Ras in complex with GDP, GTP, GTPγS and GppNHp, and of Q61A K-Ras in complex with GDP, are reported. In the G12A K-Ras–GTP complex, the switch I region undergoes a significant reorganization such that the Tyr32 side chain points towards the GTP-binding pocket and forms a hydrogen bond to the GTP γ-phosphate, effectively stabilizing GTP in its precatalytic state, increasing the activation energy required to reach the transition state and contributing to the reduced intrinsic GTPase activity of G12A K-Ras mutants.

scholarly journals Single-cell evaluation reveals shifts in the tumor-immune niches that shape and maintain aggressive lesions in the breast

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Vidya C. Sinha ◽  
Amanda L. Rinkenbaugh ◽  
Mingchu Xu ◽  
Xinhui Zhou ◽  
Xiaomei Zhang ◽  
...  
Keyword(s):  
Breast Cancer ◽  
T Cells ◽  
Mouse Model ◽  
Transition State ◽  
Tumor Cell ◽  
Single Cell ◽  
Tumor Cells ◽  
Breast Lesions ◽  
Aggressive Tumor ◽  
Insight Into

AbstractThere is an unmet clinical need for stratification of breast lesions as indolent or aggressive to tailor treatment. Here, single-cell transcriptomics and multiparametric imaging applied to a mouse model of breast cancer reveals that the aggressive tumor niche is characterized by an expanded basal-like population, specialization of tumor subpopulations, and mixed-lineage tumor cells potentially serving as a transition state between luminal and basal phenotypes. Despite vast tumor cell-intrinsic differences, aggressive and indolent tumor cells are functionally indistinguishable once isolated from their local niche, suggesting a role for non-tumor collaborators in determining aggressiveness. Aggressive lesions harbor fewer total but more suppressed-like T cells, and elevated tumor-promoting neutrophils and IL-17 signaling, disruption of which increase tumor latency and reduce the number of aggressive lesions. Our study provides insight into tumor-immune features distinguishing indolent from aggressive lesions, identifies heterogeneous populations comprising these lesions, and supports a role for IL-17 signaling in aggressive progression.

scholarly journals Exploring Flaring Behaviour on Low Mass Stars, Solar-type Stars and the Sun

2019 ◽  
Vol 15 (S354) ◽  
pp. 384-391
Author(s):  
L. Doyle ◽  
G. Ramsay ◽  
J. G. Doyle ◽  
P. F. Wyper ◽  
E. Scullion ◽  
...  
Keyword(s):  
High Energy ◽  
The Sun ◽  
Low Mass Stars ◽  
Highly Active ◽  
Rotation Phase ◽  
Solar Type ◽  
Low Mass ◽  
Insight Into ◽  
Reconnection Model ◽  
High Cadence

AbstractWe report on our project to study the activity in both the Sun and low mass stars. Utilising high cadence, Hα observations of a filament eruption made using the CRISP spectropolarimeter mounted on the Swedish Solar Telescope has allowed us to determine 3D velocity maps of the event. To gain insight into the physical mechanism which drives the event we have qualitatively compared our observation to a 3D MHD reconnection model. Solar-type and low mass stars can be highly active producing flares with energies exceeding erg. Using K2 and TESS data we find no correlation between the number of flares and the rotation phase which is surprising. Our solar flare model can be used to aid our understanding of the origin of flares in other stars. By scaling up our solar model to replicate observed stellar flare energies, we investigate the conditions needed for such high energy flares.

scholarly journals CRITICAL PHENOMENA IN DEEP INELASTIC SCATTERING

2010 ◽  
Vol 25 (31) ◽  
pp. 5667-5682 ◽  
Author(s):  
L. L. JENKOVSZKY ◽  
ANDREA NAGY ◽  
S. M. TROSHIN ◽  
JOLÁN TURÓCI ◽  
N. E. TYURIN
Keyword(s):  
Phase Transition ◽  
Inelastic Scattering ◽  
Deep Inelastic Scattering ◽  
Deeply Virtual Compton Scattering ◽  
Virtual Compton Scattering ◽  
Heavy Ion ◽  
High Energy ◽  
Ion Collisions ◽  
Bjorken X ◽  
Insight Into

Saturation in deep inelastic scattering and deeply virtual Compton scattering is associated with a phase transition between the partonic gas, typical of moderate x and Q2, and partonic fluid appearing at increasing Q2 and decreasing Bjorken x. In this paper we do not intend to propose another parametrization of the structure function; instead we suggest a new insight into the internal structure of the nucleon, as seen in deep inelastic scattering, and its connection with that revealed in high-energy nucleons and heavy-ion collisions.

Insight into the Mechanisms of the Ethylbenzene Disproportionation: Transition State Shape Selectivity on Zeolites

2008 ◽  
Vol 130 (38) ◽  
pp. 12642-12644 ◽  
Author(s):  
Jun Huang ◽  
Yijiao Jiang ◽  
V. R. Reddy Marthala ◽  
Michael Hunger
Keyword(s):  
Transition State ◽  
Shape Selectivity ◽  
Insight Into

scholarly journals First-principles insight into CO hindered agglomeration of Rh and Pt single atoms on m-ZrO2

2020 ◽  
Vol 10 (17) ◽  
pp. 5847-5855
Author(s):  
Minttu M. Kauppinen ◽  
Marko M. Melander ◽  
Karoliina Honkala
Keyword(s):  
Thermodynamic Stability ◽  
First Principles ◽  
Single Atom ◽  
Reaction Conditions ◽  
Multi Scale ◽  
Single Atoms ◽  
Thermodynamic Framework ◽  
Insight Into ◽  
Non Equilibrium

Kinetic and thermodynamic stability of single-atom and nanocluster catalysts is addressed under reaction conditions within a DFT-parametrised multi-scale thermodynamic framework combining atomistic, non-equilibrium, and nanothermodynamics.

The Structure of the Decalone Obtained From the Oxidation of Guaiol

1992 ◽  
Vol 45 (2) ◽  
pp. 327 ◽  
Author(s):  
RM Carman ◽  
AC Garner ◽  
WT Robinson
Keyword(s):  
Transition State ◽  
Crystallographic Analysis ◽  
Ring System ◽  
X Ray ◽  
Fused Ring ◽  
Fused Ring System ◽  
Insight Into

The structure of the decalone previously reported from the oxidation of guaiol has, after X-ray crystallographic analysis, been revised to structure (3c) which contains a cis -fused ring system. Deuteration studies give insight into the conformation of the transition state during the reaction.

scholarly journals Are boat transition states likely to occur in Cope rearrangements? A DFT study of the biogenesis of germacranes

2017 ◽  
Vol 13 ◽  
pp. 1969-1976 ◽  
Author(s):  
José Enrique Barquera-Lozada ◽  
Gabriel Cuevas
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Density Functional ◽  
Chair Conformation ◽  
High Energy ◽  
Functional Theory ◽  
Sigmatropic Rearrangements ◽  
The Density Functional Theory ◽  
Reaction Proceeds ◽  
Cope Rearrangements

It has been proposed that elemanes are biogenetically formed from germacranes by Cope sigmatropic rearrangements. Normally, this reaction proceeds through a transition state with a chair conformation. However, the transformation of schkuhriolide (germacrane) into elemanschkuhriolide (elemane) may occur through a boat transition state due to the final configuration of the elemanschkuhriolide, but this transition state is questionable due to its high energy. The possible mechanisms of this transformation were studied in the density functional theory frame. The mechanistic differences between the transformation of (Z,E)-germacranes and (E,E)-germacranes were also studied. We found that (Z,E)-germacranolides are significantly more stable than (E,E)-germacranolides and elemanolides. In the specific case of schkuhriolide, even when the boat transition state is not energetically favored, a previous hemiacetalization lowers enough the energetic barrier to allow the formation of a very stable elemanolide that is even more stable than its (Z,E)-germacrane.

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