Site transition

J. M. Thomas, C. R. Catlow and G. Sankar, Determining the structure of active sites, transition states and intermediates in heterogeneously catalysed reactions, Chem. Commun., 2002, 2921. 

Active Site Transition State Catalysis Lock and Key Induced Fit... 

The metal complexes in an SIB catalyst are confined to separate supercages. Consequently, the formation of inactive dimers is no longer possible. Shape-selectivity is another feature of SIB catalysts that follows from the restricted space inside the zeolite pore system. This can be simply due to discrimination in size of the reactant molecules (a large reactant molecule is excluded from the zeolite) or to a constrained orientation of the reactant at the catalytic site (transition state selectivity). 

We have listed important perovskite oxides containing B-site transition-metal atoms... 

Water binding varies with the number and type of polar groups (5 ). Other factors that affect the mechanism of protein-water interactions include protein conformation and environmental factors that affect protein polarity and/or conformation. Conformational changes in the protein molecules can affect the nature and availability of the hydration sites. Transition from globular to random coil conformation may expose previously buried amino acid side chains, thereby making them available to interact with aqueous medium. Consequently, an unfolded conformation may permit the protein to bind more water than was possible in the globular form ( ). 

The elementary reaction (3.36a) is distinguished from usual radical substitution reactions (including 3.36b) by simultaneous transfer of two hydrogen atoms from two neighboring carbon atoms (in ethylbenzene molecule) to free radical H02 via a hexa-site transition state ... 

Please note that on January 15,2008, the FDA Web site transitioned to the Federal Dockets Management System (FDMS). FDMS is a Government-wide, electronic docket management system. Electronic submissions will be accepted by the FDA through FDMS only. 

Fig. 4. Selected molecular configurations involved in (a) n-hexane and (b) n-butane and n-octane hopping on Pt(lll) along easy migration paths. The molecular motion follows the sequence 1-2-3 in (b). Filled (open) circles indicate the carbon backbone position of the molecule at the binding site (transition state), diamonds correspond to Pt surface atoms [66].

The John—Teller effect and stabilization energies in distorted coordination sites. Transition metal ions rarely occur in high-symmetry coordination sites in silicate minerals, which show various distortions from regular octahedral,... 

Miles RW, Tyler PC, Furneaux RH, Bagdassarian CK, Schramm VL (1998) One-third-the-sites transition state inhibitors for purine nucleoside phosphorylase. Biochemistry 37 8615-8621... 

Table 4. Some geometrical features of the alkane/acid site transition states for protoly tic cracking. (a) cleavage on the primary C-C bond (b) cleavage on the secondary C-C bond.

Fig. 16. FT-RAIRS of CO adsorbed at saturation coverage at 300K on Ti02(l 10) supported Pd particles [59, 77]. The bands associated with bridge bonded CO (B and B2) were used as indicators of particle morphology. Linear bands (L) were associated with edge or terrace sites. Transition bands were associated with small Pd particles, and absorption bands with larger Pd particles.

ADMET has been shown to be a step-growth polycondensation reaction [31[. The kinetics of step-growth polymerization and consequences thereof are completely different than those of chain polymerizations. Since ROMP and many other single-site transition metal-catalyzed polymerizations discussed in this book proceed... 

The availability of high-resolution structural data on various light-harvesting complexes has made it possible to relate spectroscopic observations of dynamics and their time scales to a detailed physical picture. An important link connecting the structural model to the dynamical information is the electronic Hamiltonian, containing the site transition energies for each chromophore and the electronic couplings between the chromophores. This information can be obtained from quantum chemical calculations, as has been described previously [9,11,13,29,74]. 

The above mentioned enzyme systems all contain at the catalytic site transition metal ions specifically coordinated by groups of the apoprotein either directly or indirectly via a porphyrin ring. For the activity the interaction between the c -orbitals of the transition metal ion and the tt-molecular orbitals of the substrates seems to play a central role. 

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