Ligand energies

Ligand Energy Protein Energy Interaction Energy Total Energy Normalized Energy... 

Before leaving this brief introduction to molecular orbital theory, it is worth stressing one point. This model constructs a series of new molecular orbitals by the combination of metal and ligand orbitals, and it is fundamental to the scheme that the ligand energy levels and bonding are, and must be, altered upon co-ordination. Whilst the crystal field model probably over-emphasises the ionic contribution to the metal-ligand interaction, the molecular orbital models probably over-emphasise the covalent nature. 

Interesting results were obtained on the temperature dependence of the lifetime of an Eu(III) amino-diphosphonate complex, in H2O and D2O (Holz et al., 1990b). In both solvents, the lifetime decreases as temperature increases and this was ascribed to an additional (photoin-duced) deexcitation pathway due to some ligand energy levels. 

Deoxymyoglobin Fe ligand H2O is not strong ligand energy difference between eg and t2g d orbitals is small, the 6 d electrons occupy all orbitals Paramagnetic due to unpaired electrons... 

In this model, S fit was used to calculate steric fit between ligand and receptor, Dip-mom was for dipole moment, HOMO was for HOMO ligand energy, G CDS aq was for cavity-dispersion-solvent free energy. The most important parameters in the QSAR model were steric descriptors (MW and volume) since their contribution to the regression equation was > 66% of the total. 

To speed the PLS calculations, one can drastically reduce the number of columns of fields included by rejecting all probe-ligand energies with a low standard deviation (generally 0.05-2.0 kcal/mol) among the molecules in the data set. This variable selection assumes that a property that does not vary significantly will not be statistically useful. For example, the lattice points inside the union volume of the superimposed molecules sample constant steric energies, hence cannot explain the differences in potency between different compounds. 

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