Transition analogs

The absorption spectra of the lanthanide +3 cations are shown in Fig. 14.7. These spectra result from f-f transitions analogous to the d-d transitions of the transition metals. In contrast to the latter, however, the broadening effect of ligand vibrations is minimized because the 4/orbitals in the lanthanides are buned deep within the atom. Absorption spectra of the lanthanide cations are thus typically steip and line-like as opposed to the broad absorptions of the transition metals. 

Polypeptides and poly(a-amino acid)s have a quite unique position amongst synthetic polymers. The reason for this is that most common synthetic polymers have very little long range order in solution and their properties are the products of statistical random coil conformations. Polypeptides, in contrast, can adopt well defined, ordered structures typical of those existing in proteins, such as a-helix and P-struc-tures. Moreover, the ordered structures can undergo conformational changes to the random coil state as cooperative transitions, analogous to the denaturation of proteins. 

Absorption Spectro The absorption spectra of the lantlenide +3 caiicms are shown in Hg. 14.7. These of the Lanthanides ctra result from /-/ transitions analogous to the d-d transitions of the transition... 

The dipole-moment components p,x, p.y, p-z transform like the corresponding coordinates x, y,z. This determines the selection mles for IR transitions. Analogously, the components of the polarizability tensor a x. transform like the... 

Schmidt and co-workers have been investigating a series of potent inhibitors of a(2,6)-sialyl-transferase (O Fig. 9). They developed the transition analog 42 [153], based on the proposed mechanism of the sialyl transfer, that involves the partial dissociation of the CMP and the formation of the planer oxocarbenium ion structure in the transition state. They also found that the planer neuraminyl moiety in 42 can be replaced by the aromatic groups, leading to the readily accessible aromatic inhibitors of a(2,6)-sialyltransferase from rat liver. Further library... 

An unusual feature of the heneicosanol measurements was a second scattering peak, which appeared to arise at high pressure at temperatures below 16°C. It was attributed to a weakly first-order phase transition analogous to the rotator Il-to-rotator I transition in lamellar crystalline n-alkanes with n = 23,25. In the rotator II phase, rapid reorientation of the chain around its axis leads to a pseudohexagonal structure. When the chains can no longer reorient, the symmetry of the structure is reduced to a uniaxially distorted hexagonal strueture. 

The characteristic spectrum depends on the metal forming the anode (Fig. 3.33 for Mo and Cu). It is due to electronic transitions analogous to the atomic spectra... 

To summarize, it appears that the magnetic properties of p-Mn02 nanoparticles vary dramatically from sample to sample. For typical particles with a size exceeding 25-50 nm, a small increase in is usually found, but no transition analogous to bulk... 

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