LMP2

There is also a local MP2 (LMP2) method. LMP2 calculations require less CPU time than MP2 calculations. LMP2 is also less susceptible to basis set superposition error. The price of these improvements is that about 98% of the MP2 energy correction is recovered by LMP2. 

Dovhey, S. E., Ghosh, N. S., and Wright, K. L., 2000, Loss of interferon-y inducibility of TAPI and LMP2 in a renal cell carcinoma cell line. Cancer Res. 60 5789-5796. 

In mammalian cells, previous reports proved the localization of proteasomes both in the cytoplasm and in the nucleus (Palmer et al. 1996 Peters et al. 1994). In a more recent study GFP-tagged 20 S proteasomes in fibrosarcoma cells were shown to be dispersed over the cytoplasm and nucleoplasm wherein they seem to diffuse rapidly (Reits et al. 1997). Reits et al. used a fusion protein of GFP with the proteasome subunit LMP2, ich replaces a p subimit of the proteasome upon induction with interferon y, a stimulator of... 

A number of different localized MP2 procedures ( LMP2 ) have been developed. The idea is to localize the Hartree-Fock orbitals prior to their use in the MP2 procedure. For sufficiently large molecules, this significantly reduces the number of integrals (ij ab) which need to be calculated and processed and leads to reduction in both computational effort and overall memory and disk requirements. Localized MP3 and MP4 models are not presently available. 

LMP2/6-311+G //BP/6-31G localized MP2 calculation of energy with 6-311+G basis set preceded by BP 6-3IG density functional calculation of geometry... 

Relative times for the MMFF molecular mechanics model, the AMI semi-empirical model, Hartree-Fock models with 3-2IG, 6-3IG and 6-311+G basis sets, EDFl and B3LYP density functional models and the MP2 model with 6-3IG and 6-311+G basis sets, for energy calculations, geometry optimizations and frequency evaluations, and the localized MP2 (LMP2) model with 6-3 IG and... 

MP2 calculations are much more costly than comparable (same basis set) Hartree-Fock and density functional calculations. In practice, their application is much more limited than either of these models. Localized MP2 (LMP2) energy calculations are similar in cost to MP2 calculations for small molecules, but the cost differential rapidly increases with increasing molecular size. Still they are close to an order of magnitude more costly than Hartree-Fock or density functional calculations. 

Localized MP2 (LMP2) models have already been shown to provide results which are nearly indistinguishable from MP2 models for both thermochemical calculations (see Chapter 12) and for calculation of conformational energy differences (see Chapter 14). Activation energy calculations provide an even more stringent test. Transition states necessarily involve delocalized bonding, which may in turn be problematic for localization procedures. 

Data presented in Table 15-10 compare activation energies from LMP2/6-311+G and MP2/6-311+G calculations, both sets making use of underlying Hartree-Fock 6-3IG geometries. The results are very clear localization has an insignificant effect on calculated activation energies. The procedure can be employed with confidence. 

At the LMP2/6-311+G //6-3IG level, Dewar benzene is 80 kcal/mol higher in energy than benzene, in reasonable accord with the experimental estimate of 71 kcal/molJ Interestingly, benzvalene is predicted to be slightly more stable than Dewar benzene. Both prismane and 3,3 -bis(cyclopropene) are much less stable. 

LMP2 Model. An MP2 Model in which the Hartree-Fock orbitals are first localized. 

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