Mechanisms of electron-transfer oxidation of NADH analogues and chemiluminescence. Detection of the keto and enol radical cations.

The radical cation of an NADH analogue (BNAH: 1-benzyl-1,4-dihydronicotinamide) has been successfully detected as the transient absorption and ESR spectra in the thermal electron transfer from BNAH to Fe(bpy)(3)(3+) (bpy = 2,2'-bipyridine) and Ru(bpy)(3)(3+). The ESR spectra of the radical cations of BNAH and the dideuterated compound (BNAH-4,4'-d(2)) indicate that the observed radical cation is the keto form rather than the enol form in the tautomerization. The deprotonation rate and the kinetic isotope effects of the keto form of BNAH(*)(+) were determined from the kinetic analysis of the electron-transfer reactions. In the case of electron transfer from BNAH to Ru(bpy)(3)(3+), the chemiluminescence due to Ru(bpy)(3)(2+) was observed in the second electron-transfer step from BNA(*), produced by the deprotonation of the keto form of BNAH(*)(+), to Ru(bpy)(3)(3+). The observation of chemiluminescence due to Ru(bpy)(3)(2+) provides compelling evidence that the Marcus inverted region is observed even for such an intermolecular electron-transfer reaction. When BNAH is replaced by 4-tert-butylated BNAH (4-t-BuBNAH), no chemiluminescence due to Ru(bpy)(3)(2+) has been observed in the electron transfer from 4-t-BuBNAH to Ru(bpy)(3)(3+). This is ascribed to the facile C-C bond cleavage in 4-t-BuBNAH(*)(+). In the laser flash photolysis of a deaerated MeCN solution of BNAH and CHBr(3), the transient absorption spectrum of the enol form of BNAH(*)(+) was detected instead of the keto form of BNAH(*)(+), and the enol form was tautomerized to the keto form. The rate of intramolecular proton transfer in the enol form to produce the keto form of BNAH(*)(+) was determined from the decay of the absorption band due to the enol form and the rise in the absorption band due to the keto form. The kinetic isotope effects were observed for the intramolecular proton-transfer process in the keto form to produce the enol form.

Direct detection of radical cations of NADH analogues.

The radical cation of an NADH analogue (BNAH: 1-benzyl-1,4-dihydronicotinamide) has been successfully detected as the transient absorption and ESR spectra in the thermal electron transfer from BNAH to Fe(bpy)33+ (bpy = 2,2'-bipyridine). The ESR spectra of the radical cations of BNAH and the dideuterated compound (BNAH-4,4'-d2) indicate that the observed radical cation is the keto form rather than the enol form in the tautomerization. The deprotonation rate and the kinetic isotope effects of the keto form of BNAH*+ were determined from the kinetic analysis of the electron-transfer reactions.

Significant enhancement of electron transfer reduction of NAD(+) analogues by complexation with scandium ion and the detection of the radical intermediate-scandium ion complex.

4-Acetyl-N,N-diisopropyl-1-benzylnicotinamidinium ion (ABNA(+)) and 1-benzyl-4-phenylnicotinamidinium ion (PhBNA(+)) were newly synthesized as NAD(+) analogues to examine the electron-transfer reactivity and the effects of metal ions on the reactivity in comparison with those of 1-benzylnicotinamidinium ion (BNA(+)) and 1-methyl-4-phenylpyridinium ion (MPP(+)) which has no amide or acetyl group. A remarkable positive shift in the one-electron reduction potential of ABNA(+) was observed in the presence of Sc(3+) which forms a 1:1 complex with ABNA(+) through both acetyl and amide groups, whereas no such shift in the presence of Sc(3+) was observed for the one-electron reduction of MPP(+) which has no acetyl or amide group. Similar but less positive shifts in the one-electron reduction potentials were observed in the presence of Sc(3+) for the one-electron reduction of BNA(+) and PhBNA(+) both of which have only one amide group. The rate of electron-transfer reduction of ABNA(+) is enhanced significantly by the complexation with Sc(3+) to produce stable ABNA(*)-Sc(3+) complex which has been successfully detected by ESR. The electron self-exchange rates of the MPP(*)/MPP(+) system have been determined from the ESR line width variation and are compared with those of the ABNA(*)/ABNA(+) system.

Interpretation of damage to houses and casualties relied on a precise evaluation of earthquake ground motions in the epicentral region : The 1945 Mikawa earthquake

Although about two thousand people were killed by the 1945 Mikawa earthquake, a clear description of the entire event has yet to be given because the earthquake took place just beford the end of World War II. In order to describe what happened in the epicentral region during this earthquake, the authors estimated the ground motion and investigated the damage done to houses the casualties caused by the earthquake. The ground motion was estimated by a non linear finite element method, in which modified joint elements were adopted to model the fault plane. The seismic intensity in the area near the fault was estimated from the calculated maximum velocity. The damage done to houses and the casualties caused were investigated by questionaire. The destruction of houses was compared in detail to the number of casualties. The type of damage is discussed in relation to the estimated ground motion