A molecular mechanics study of conformational isomerism in 1- and 3-aryl hydantoins and 3-aryl-2-thiohydantoins

1991 ◽  
Vol 69 (12) ◽  
pp. 1957-1963 ◽  
Author(s):  
Lawrence D. Colebrook
Keyword(s):  
Force Field ◽  
Key Words ◽  
Molecular Mechanics ◽  
Internal Rotation ◽  
Transition States ◽  
Rotational Energy ◽  
Conformational Isomerism ◽  
Hindered Rotation ◽  
Energy Profiles ◽  
Conformational Preferences

Energy profiles for internal rotation about the C—N pivot bond in a series of 1- and 3-aryl hydantoins and 3-aryl-2-thiohydantoins have been computed using the MMX molecular mechanics force field. Rotational ground and transition states have been identified and their energies calculated. Conformational preferences of diastereomeric rotamers have been investigated. Computed rotational energy barriers generally are within ± 2 kcal/mol of the experimentally determined values. Key words: conformational isomerism, hindered rotation, hydantoins, thiohydantoins, molecular mechanics.

Synthèse, structure et études spectroscopiques RMN 1H et 13C de dérivés perhydrocyclododéca[b]furaniques

1991 ◽  
Vol 69 (3) ◽  
pp. 521-527 ◽  
Author(s):  
Michel Albrand ◽  
René Dolmazon ◽  
Patrick Pollet
Keyword(s):  
Conformational Analysis ◽  
Force Field ◽  
Key Words ◽  
Molecular Mechanics ◽  
Trans Isomer ◽  
Nmr Spectra ◽  
Synthetic Route ◽  
Force Field Calculations ◽  
Cis Isomer ◽  
C Nmr

A synthetic route to perhydrocyclododeca[b]furan-3-ols, perhydrocyclododeca[b]furan-3-ones, and perhydrocyclododeca[b]furan derivatives is described. Their configurations were determined. For the perhydrocyclododeca[b]furan-3-one and perhydrocyclododeca[b]furan pairs, the cis isomer was much less stable than the trans isomer. This agrees well with results from a conformational analysis, carried out by molecular mechanics. The 1H and l3C NMR spectra are reported. Key words: perhydrocyclododeca[b]furans, conformations, force field calculations, 1H and 13C NMR.

Rotational isomerism in fluorene derivatives. XX. Conformational equilibria of 9-substituted 9-(o-methylthiomethylphenyl)- and 9-substituted 9-(o-methylsulfinylmethylphenyl)fluorenes

1991 ◽  
Vol 69 (4) ◽  
pp. 615-619 ◽  
Author(s):  
Akiko Nishida ◽  
Yoshifumi Akagawa ◽  
Shinsuke Shirakawa ◽  
Shizuo Fujisaki ◽  
Shoji Kajigaeshi
Keyword(s):  
Low Temperature ◽  
Key Words ◽  
Equilibrium Constant ◽  
Internal Rotation ◽  
Kinetic Data ◽  
Room Temperature ◽  
Rotational Isomerism ◽  
Oxidation Products ◽  
Conformational Isomerism ◽  
Conformational Equilibria

Several 9-substituted 9-(o-methylthiomethylphenyl)fluorenes and their oxidation products, 9-substituted 9-(o-methylsulfinylmethylphenyl)fluorenes, were prepared. Each equilibrium constant at room temperature or at low temperature was investigated and the conformational equilibria [Formula: see text] of these compounds are discussed by comparing them with those of the corresponding 9-substituted 9-(o-methylthiophenyl)fluorenes and 9-substituted 9-(o-methylsulfinylphenyl)fluorenes in which the o-substituents were one CH2 unit shorter than those of the title compounds. Kinetic data for the internal rotation of several compounds are also given. Key words: conformational isomerism, restricted rotation, 9-arylfluorenes.

scholarly journals Assessment of Amyloid Forming Tendency of Peptide Sequences from Amyloid Beta and Tau Proteins Using Force-Field, Semi-Empirical, and Density Functional Theory Calculations

2021 ◽  
Vol 22 (6) ◽  
pp. 3244
Author(s):  
Charuvaka Muvva ◽  
Natarajan Arul Murugan ◽  
Venkatesan Subramanian
Keyword(s):  
Force Field ◽  
Density Functional ◽  
Amyloid Β ◽  
Density Functional Theory Calculations ◽  
Tau Proteins ◽  
Functional Theory ◽  
Energy Profiles ◽  
Α Helix ◽  
Semi Empirical ◽  
Β Sheet

A wide variety of neurodegenerative diseases are characterized by the accumulation of protein aggregates in intraneuronal or extraneuronal brain regions. In Alzheimer’s disease (AD), the extracellular aggregates originate from amyloid-β proteins, while the intracellular aggregates are formed from microtubule-binding tau proteins. The amyloid forming peptide sequences in the amyloid-β peptides and tau proteins are responsible for aggregate formation. Experimental studies have until the date reported many of such amyloid forming peptide sequences in different proteins, however, there is still limited molecular level understanding about their tendency to form aggregates. In this study, we employed umbrella sampling simulations and subsequent electronic structure theory calculations in order to estimate the energy profiles for interconversion of the helix to β-sheet like secondary structures of sequences from amyloid-β protein (KLVFFA) and tau protein (QVEVKSEKLD and VQIVYKPVD). The study also included a poly-alanine sequence as a reference system. The calculated force-field based free energy profiles predicted a flat minimum for monomers of sequences from amyloid and tau proteins corresponding to an α-helix like secondary structure. For the parallel and anti-parallel dimer of KLVFFA, double well potentials were obtained with the minima corresponding to α-helix and β-sheet like secondary structures. A similar double well-like potential has been found for dimeric forms for the sequences from tau fibril. Complementary semi-empirical and density functional theory calculations displayed similar trends, validating the force-field based free energy profiles obtained for these systems.

scholarly journals Assessing the effective factors affecting the conformational preferences and the early and late transition states of the unimolecular retro-ene decomposition reactions of ethyl cyanate, ethyl thiocyanate and ethyl selenocyanate

RSC Advances ◽  
2017 ◽  
Vol 7 (37) ◽  
pp. 22757-22770 ◽  
Author(s):  
Hooshang Atabaki ◽  
Davood Nori-Shargh ◽  
Mohamad Momen-Heravi
Keyword(s):  
Transition States ◽  
Factors Affecting ◽  
Effective Factors ◽  
Decomposition Reactions ◽  
Barrier Heights ◽  
Conformational Preferences ◽  
Late Transition

The variations of Δ[(HCGAE(X3–C4weakening) – HCGAE(X3–C4strengthening)] parameters correlate well with the variations of the retro-ene decomposition reactions barrier heights going from compound1to compound3.

Hydration of platinum(II) complexes: a molecular mechanics study using atom-based force-field parameters

2000 ◽  
Vol 104 (3-4) ◽  
pp. 247-251 ◽  
Author(s):  
Jacqueline Langlet ◽  
Jacqueline Berg�s ◽  
Jacqueline Caillet ◽  
Jiri Kozelka
Keyword(s):  
Force Field ◽  
Molecular Mechanics ◽  
Force Field Parameters

The tetracycline: Mg2+ complex: A molecular mechanics force field

2006 ◽  
Vol 27 (13) ◽  
pp. 1517-1533 ◽  
Author(s):  
Alexey Aleksandrov ◽  
Thomas Simonson
Keyword(s):  
Force Field ◽  
Molecular Mechanics

AFMM: A molecular mechanics force field vibrational parametrization program

2005 ◽  
Vol 167 (1) ◽  
pp. 34-42 ◽  
Author(s):  
A.C. Vaiana ◽  
Z. Cournia ◽  
I.B. Costescu ◽  
J.C. Smith
Keyword(s):  
Force Field ◽  
Molecular Mechanics
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