Conformational analysis of picrotoxinin by N.M.R., X-ray crystallography, and molecular orbital and classical potential-energy calculations

1983 ◽  
Vol 36 (11) ◽  
pp. 2219 ◽  
Author(s):  
PR Andrews ◽  
RTC Brownlee ◽  
MF Mackay ◽  
DB Poulton ◽  
M Sadek ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Active Form ◽  
Energy Difference ◽  
Biologically Active ◽  
Molecular Orbital Calculations ◽  
X Ray ◽  
X Ray Crystallography ◽  
Potential Energy Calculations ◽  
Classical Potential ◽  
Low Energy Conformations

The conformation of the potent convulsant drug picrotoxinin has been studied by proton n.m.r., X-ray crystallography, molecular orbital calculations and classical calculations. The calculations reveal two alternative low-energy conformations, either of which is consistent with the n.m.r. data, and one of which is also observed crystallographically. The energy difference is sufficiently small to suggest that either conformation may be the biologically active form.

Dipolar Cycloaddition Reactions of Nitrilimines

1998 ◽  
Vol 51 (6) ◽  
pp. 499 ◽  
Author(s):  
James B. F. Dunstan ◽  
Gordon M. Elsey ◽  
Richard A. Russell ◽  
G. Paul Savage ◽  
Gregory W. Simpson ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Dipolar Cycloaddition ◽  
Molecular Orbital Calculations ◽  
Cycloaddition Reactions ◽  
X Ray ◽  
X Ray Crystallography ◽  
Complex Rearrangement ◽  
Semiempirical Molecular Orbital

A series of γ-substituted α-methylidene-γ-butyrolactone derivatives underwent regiospecific 1,3-dipolar cycloaddition with N-methyl-C-phenylnitrilimine. These reactions proceeded regiospecifically and with high diastereoselectivity, generally favouring the anti diastereomer as determined by n.m.r. spectroscopy and semiempirical molecular orbital calculations. The assignment for one product was confirmed by X-ray crystallography. N-Methyl-C-phenylnitrilimine underwent regiospecific cycloaddition with a range of C=S-containing dipolarophiles. Substituted thioureas were generally unreactive as dipolarophiles, while 5-thio-substituted 1,3,4-thiadiazole-2(3H)-thiones underwent ready reaction to produce, rather than the expected cycloadducts, complex rearrangement products. The structure of one of these unusual products has been confirmed by X-ray crystallography. A series of disubstituted nitrilimines underwent regiospecific cycloaddition with thiobenzophenone; the structures of the products were confirmed by X-ray crystallography.

The crystal and molecular structure of picrotoxinin

1983 ◽  
Vol 36 (10) ◽  
pp. 2111 ◽  
Author(s):  
MF Mackay ◽  
M Sadek
Keyword(s):  
Molecular Structure ◽  
Crystal And Molecular Structure ◽  
Direct Methods ◽  
Low Energy ◽  
Monoclinic Space Group ◽  
Molecular Orbital Calculations ◽  
Asymmetric Unit ◽  
X Ray ◽  
Classical Potential ◽  
Low Energy Conformations

X-ray analysis has defined the conformational detail in crystals of picrotoxinin, C15H1606. Crystals are monoclinic: space group PZ1, a 7.719(1), b 12.004(3), c 14.693(4), Ǻ β 98.06(1)7#176; and Z 4. The structure was solved by direct methods with diffractometer data measured with Cu Kα radiation. Refinement converged at R 0.037 for the 2220 observed terms. The two molecules in the asymmetric unit have essentially identical conformations consistent with one of the two alternative low energy conformations deduced from classical potential energy and molecular orbital calculations.

scholarly journals Mechanism of IPPase shown by high resolution Neutron and X-ray crystallography

2014 ◽  
Vol 70 (a1) ◽  
pp. C1211-C1211
Author(s):  
Joseph Ng ◽  
Ronny Hughes ◽  
Michelle Morris ◽  
Leighton Coates ◽  
Matthew Blakeley ◽  
...  
Keyword(s):  
High Resolution ◽  
Active Site ◽  
Inorganic Pyrophosphatase ◽  
Inorganic Pyrophosphate ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cellular Processes ◽  
Crystallographic Structures ◽  
Hydrolysis Of ◽  
Low Energy Conformations

Soluble inorganic pyrophosphatase (IPPase) catalyzes the hydrolysis of inorganic pyrophosphate (PPi) to form orthophosphate (Pi). The action of this enzyme shifts the overall equilibrium in favor of synthesis during a number of ATP-dependent cellular processes such as in the polymerization of nucleic acids, production of coenzymes and proteins and sulfate assimilation pathways. Two Neutron crystallographic (2.10-2.50Å) and five high-resolution X-ray (0.99Å-1.92Å) structures of the archaeal IPPase from Thermococcus thioreducens have been determined under both cryo and room temperatures. The structures determined include the recombinant IPPase bound to Mg+2, Ca+2, Br-, SO2-2 or PO4-2 involving those with non-hydrolyzed and hydrolyzed pyrophosphate complexes. All the crystallographic structures provide snapshots of the active site corresponding to different stages of the hydrolysis of inorganic pyrophosphate. As a result, a structure-based model of IPPase catalysis is devised showing the enzyme's low-energy conformations, hydration states, movements and nucleophile generation within the active site.

Comparative X-ray Diffraction Studies and Molecular Orbital Calculations on Diazinium Dicyanomethylides

2001 ◽  
Vol 13 (1) ◽  
pp. 93-102 ◽  
Author(s):  
Kiyoshi Matsumoto ◽  
Takane Uchida ◽  
Mituso Toda ◽  
Naoto Hayashi ◽  
Yukio Ikemi ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
X Ray Diffraction ◽  
X Ray
Sign in / Sign up

Export Citation Format

Share Document