Deuteration, effect

Equation 13 can be solved numerically for Tc as a function of the proton-lattice coupling. The parameters are chosen so as to fit the experimental value of Tc for KDP. For C = 21 732 K/A and g2ygAyf close to those used for perovskite oxides, Tc Ikdp = 115 K. In Fig. 3 Tc is shown as a function of C with all other parameters fixed. Including the deuteration effects (Table 2), Ter = C Idkdp/C Ikdp 1 2. With this estimate TcIdkdp = 168 K. C itself depends only weakly on /, g2y g4 but a strong dependence on/ is observed, which is the coupling between the PO4 shells and the K" " ions. This, on the other hand, should not be dependent on deuteration. 

In addition, for solid samples or peptides in nonaqueous solvents, the amide II (primarily in-plane NH deformation mixed with C—N stretch, -1500-1530 cm-1) and the amide A (NH stretch, -3300 cm-1 but quite broad) bands are also useful added diagnostics of secondary structure 5,15-17 Due to their relatively broader profiles and complicated by their somewhat weaker intensities, the frequency shifts of these two bands with change in secondary structure are less dramatic than for the amide I yet for oriented samples their polarization properties remain useful 18 Additionally, the amide A and amide II bands are highly sensitive to deuteration effects. Thus, they can be diagnostic of the degree of exchange for a peptide and consequently act as a measure of protected or buried residues as compared to those fully exposed to solvent 9,19,20 Amide A measurements are not useful in aqueous solution due to overlap with very intense water transitions, but amide II measurements can usefully be measured under such conditions 5,19,20 The amide III (opposite-phase NH deformation plus C—N stretch combination) is very weak in the IR and is mixed with other local modes, but has nonetheless been the focus of a few protein-based studies 5,21-26 Finally, other amide modes (IV-VII) have been identified at lower frequencies, but have been the subject of relatively few studies in peptides 5-8,18,27,28 ... 

Radiationless transitions often show a pronounced deuteration effect. This effect should be discussed. Notice that coh — /2cod, and Sh — Sd/V2 and that the deuteration effect can be estimated by using the Frank-Condon factor for a displaced oscillator by using the energy law expression. In this case, it is found that... 

Dynamic Triplet-Excited Region in Retinal As Revealed by Deuteration Effects on the Quantum Yields of Isomerization via the T State (Okumura, Koyama, unpublished results)... 

Figure 3.9 shows the effects of double deuteration of the C7=C8 or C11=C12 double bond and that of the C14—C15 single bond on the triplet-state CTI starting from the set of four ds isomers. The results can be summarized as follows (1) The 7,8-deuteration (7,8-D2) reduces the quantum yield of isomerization from the 7-cis to the all-trans isomer that includes rotation around the particular double bond to which deuterium substitution was made, and also, the quantum yield of isomerization from the 9-cis to the all-trans isomer around the neighboring double bond on the right-hand side of the retinal molecule (see Scheme 3.1). (2) The 11,12-deu-teration (11,12-D2) reduces the quantum yields of isomerization from the 7-cis, 9-cis, and 11-cis isomers to the all-trans isomer that include rotation around the particular cis-double bond to which deuterium substitution was made, and also, that around the neighboring double bonds on the left-hand side of the molecule. (3) The 14,15-deuteration (14,15-D2) slightly reduces the quantum yield of isomerization from the 11-cis isomer. (4) Practically no deuteration effects on the quantum yields of isomerization are seen at all starting from the 13-cis isomer [13]. Table 3.1 lists the quantum yields of isomerization per triplet species generated for the undeuterated and variously deuterated retinal isomers.

Yang, H., Shibayama, H., Stern, R.S., Shimuzu, N., and Hashimoto, T. (1986) Deuteration effects on the miscibility and phase separation kinetics of polymer blends. Mttcromdta/des, 19 (6), 1667-1674. 

Table 3j. Solvent deuteration effect on inverse temperature transition. (13) ...

Pressure tends to increase the chemical reactivity of nitromethane as well as the rate of thermal decomposition. It was observed, quite accidentally, that a pressure-induced spontaneous explosion of single crystals of nitromethane at room temperature can occur. Further study revealed that single crystals grown from the liquid with the (111) and either the (001) or the (100) crystal faces perpendicular to the applied load direction in the DAG, if pressed rapidly to over 3 GPa, explode instantaneously accompanied by an audible snapping sound. The normally transparent sample becomes opaque instantly. Visual examination of the residue revealed a dark brown solid which was stable when heated to over 300 C. Subsequent x-ray analysis showed the material to be amorphous. Mass spectral analysis of the residue was inconclusive because no well defined spectra were observed. Because most of the sample is recovered as solid residue after the explosion and is stable to over 300°C, the material may be amorphous carbon. This stress-induced explosion occurs only in protonated nitromethane because similar attempts on the deuterated form did not result in explosion. Shock experiments on oriented pentaerythritol (PETN) crystals have shown similar type behavior [25]. In this case it was suggested that the sensitivity of shock pressures to crystal orientation is the result of the availability of slip planes or system of planes in the crystal to absorb the shock, thereby increasing the threshold to explosion. A similar explanation may be applicable to the nitromethane crystals as well. The deuteration effect must play a role in the initiation chemistry. An isotope effect has been observed previously in the sensitivity of HMX and RDX to shock and thermal conditions [23]. 

IC2 Ichimura, T., Okano, K., Kurita, K., and Wada, E., Deuteration effect on the coexistence curve of semidilute polymer solution, Polym. J., 19,1101,1987. 

K. Maruszewski, K. Bajdor, D. P. Strommen and J. R. Kincaid, Position-dependent deuteration effects on the nonradiative decay of the 3MLCT state of tri (bipyridine)tuthenium (II). An e/qrerimental evaluation of radiationless transition theory, / Phys. Chem. 99,6286-6293 (1995). 

A proper comparison of deuteration effects can be made thanks to the values of (T. ) which present the advantage to be independent of polymer molecular weight and molecular weight distribution. As shown... 

Sandros, K., Fluorescence and triplet yields of benzene and toluene in cyclohexane solutions temperature and deuteration effects, Acta Chem. Scand., 25, 3651,1971. 

Klughammer, C., Klughammer, B., and Pace, R., Deuteration effects on the in vivo EPR spectrum of the reduced secondary photosystem I electron acceptor A in cyanobacteria. Biochemistry, 38, 3726, 1999. 

In deaerated solution. No deuteration effect on the lifetimes is observed in aerated solution. 

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