Anionic receptor sites model

Interaction of Model Opiate Anionic Receptor Sites with Characteristic JV-Substituents of Rigid Opiates PCILO and Empirical Potential Energy Calculations... 

Figure I. Schematic structures of model anionic receptor sites, ammonium methylphosphate (AMP), ammonium methylsulphate (AMS), and the eight compounds studied...

The object of this initial study was to determine whether any net interactions could occur between typical N-substituents and the model anionic receptor site involved in H-bonding with the protonat d amine group, without the steric constraint of attachment of the substituent to the nitrogen. 

N-SUBSTITUENTS WITH MODEL ANIONIC RECEPTOR SITES ... 

Figures 2 and 3 show the optimized geometries obtained from both the PCILO and empirical energy methods for complexes of AMP and AMS with five of the eight compounds studied. The PCILO results give distinct n-ir complexes involving interaction of one oxygen lone pair of electrons with the ir-electron system of the substitutent. In all cases, the empirical energy method gives a totally optimized complex which involves mainly electrostatic and dispersion terms. As can be seen from Figures 2 and 3, the interaction of methylcyclopropane with the model anionic receptor site is the one with the greatest difference...

TABLE III. ANTAGONIST POTENCY AND BINDING AFFINITY OF BENZOMORPHANS WITH VARYING N-SUBSTITUENTS AND THEIR ENERGIES OF INTERACTION WITH MODEL ANIONIC RECEPTOR SITES. ... 

In this study both the PCILO and empirical energy methods were used to characterize intermolecular interactions of typical N-substituents of rigid opiates with model anionic receptor sites. Ammonium methylphosphate (AMP) and ammonium methylsulfate (AMS) were used as model anionic receptor sites. Interaction energies of eight compounds which, as N-substituents. modulate different antagonist/agonist potencies... 

With the exception of the cyclopropylmetbane, the main discrepancy is the relatively large energy calculated for the 2,3 - dimethylfuran. The stabilization energies of the AMS complexes calculated by the empirical method correlate more with the measured affinities and antagonist potencies than those for the AMP complexes. Additionally, more stable complexes with AMS are found by the empirical method than by the PCILO method. Taken together, the results of both methods indicate that either the phosphate or sulfate anion is a reasonable model for the anionic opiate receptor site. 

Tyr oooupies the anionic binding site of the receptor that is the common binding point of both opioid series. This model closely resembles original bimodal binding proposal. 

Kara (17) has proposed a model of the amino acid receptor site consisting of two charged subsites, one cationic and one anionic, capable of interacting with ionized -amino and primary-carboxyl groups of amino acid molecules. He assumes that the L-lsomers have more ready access to the receptor and accounts... 

A cascade receptor is a host that binds one of more metal ions which, in turn, bind anions. They are of interest in the modelling of biological metal-based active sites — metallobiosites. 

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