%0 Journal Article
%A Barnett-Norris, Judy
%A Guarnieri, Frank
%A Hurst, Dow P.
%A Reggio, Patricia H.
%D 1998
%T Exploration of Biologically Relevant Conformations of Anandamide,
2-Arachidonylglycerol, and Their Analogues Using Conformational Memories
%U https://acs.figshare.com/articles/journal_contribution/Exploration_of_Biologically_Relevant_Conformations_of_Anandamide_2-Arachidonylglycerol_and_Their_Analogues_Using_Conformational_Memories/3683916
%R 10.1021/jm9803471.s001
%2 https://ndownloader.figshare.com/files/5774271
%K ligand
%K anandamide
%K CHCl 3
%K CB 1 receptor
%K CB 2 receptor
%K arachidonic acid
%K PGB 2
%K EA
%K conformation
%K cannabinoid CB 1 receptor
%K Conformational Memories
%K CB 1 affinity
%K H 2 O
%K CM
%K FAAH
%K AG
%X The endogenous cannabinoid anandamide (N-arachidonoylethanolamide) has been shown to
possess higher affinity for the cannabinoid CB1 receptor than for the CB2 receptor. Carrier-mediated transport has been proposed to be essential for the termination of the biological effects
of anandamide, while hydrolysis of anandamide is performed by a membrane-bound amidohydrolase, fatty acid amidohydrolase (FAAH). As interaction of anandamide with each of these
targets occurs in different environments, the conformations of anandamide for interaction with
each target may differ. To ascertain what conformations of anandamide, a highly flexible
molecule, are favored in polar and nonpolar environments, the new method of Conformational
Memories (CM) was used. CM has been shown to achieve complete conformational sampling
of highly flexible ligands, to converge in a very practical number of steps, and to be capable of
overcoming energy barriers very efficiently (Guarnieri et al. J. Am. Chem. Soc. 1996, 118, 5580).
The generalized Born/surface area (GB/SA) continuum solvation models for chloroform and
for water were used in the CM calculations. As a means of validation, CM was first applied
to arachidonic acid because both experimental and theoretical conformational studies of
arachidonic acid have been reported. CM was also applied to sn-2-arachidonylglycerol (2-AG),
another endogenous CB ligand; to a 1,1-dimethylheptyl derivative of anandamide, an analogue
with higher CB1 affinity than anandamide; and to N-(2-hydroxyethyl)prostaglandin-B2-ethanolamide (PGB2-EA), a prostanoid ligand which does not bind to CB1. Consistent with
the literature, arachidonic acid was found to exist in an extended, angle-iron shape and in
back-folded conformations which were U, J, or helical in shape. The angle-iron and U-shapes
were both highly populated conformations with the angle-iron preferred in CHCl3 and the
U-shape preferred in H2O. Results for anandamide and 2-AG paralleled those for arachidonic
acid with the exception that anandamide in water does not adopt a pure extended conformation
but, rather, favors a hybrid-extended/U-shape. For the dimethyl-heptyl derivative of anandamide, the U-shape was found to be predominant in both environments (42% in CHCl3, 38%
in H2O), but the population of the angle-iron shape was still significant (25% in CHCl3, 29% in
H2O). For all of these ligands, J-shaped conformers constituted from 7% to 17% of the conformer
population, while the helical shape was less than 5%. In both CHCl3 and H2O, the presence
of the five-membered ring attenuates the ability of PGB2-EA to adopt an extended conformation.
PGB2-EA was found instead to exist predominantly in an L-shape (i.e., distorted U-shape).
The low probability of PGB2-EA adopting an extended conformation may be why PGB2-EA
shows such low affinity for the CB1 receptor. The conformational information obtained here
for anandamide and 2-AG may be useful in the design of rigid analogues which mimic the
preferred molecular conformations (shapes) of these ligands. Such rigid analogues may be
useful in deducing the bioactive conformation of these endogenous cannabinoids, not only at
the CB receptors but also at the FAAH enzyme active site and possibly at the binding site(s)
on the newly proposed anandamide transporter.
%I ACS Publications