The tetrahydride-bridged complex ( C~M~~) R U (~-H )~R U ( C~M~~)(2) is synthesized by the reaction of [(C5Mes)RuCl212 (1) with LiAlH4, which is characterized as a classical hydride complex on the basis of the 2' 1 value and X-ray diffraction study. In the presence of acid, 2 decomposes to form a coordinatively unsaturated species, which is trapped by the 6-electron ligands to yield the cationic Welectron complexes. Treatment of 2 with ethylene yields (C5Me5)-Ru(CsMe5) (9), structural analogue of the intermediate 8. Thermolysis of 6 in toluene at 60 "C under 1 atm of ethylene generates a dinuclear ruthenacyclopentadiene complex ((25- M~~)R~(CHFCH~)(CM~=CHCH=CM~)R~(CSM~~)(10) as a result of the C-C coupling reaction among the coordinated ethylene and two vinyl ligands. The bis(palky1idene) complex (C6Me5)Ru(pL-CHMe) [pCMe(CH=CHCOMe)Ru(C5Me6) (13) which seems to be a model compound of the intermediate of the cyclometalation leading to 10 is obtained upon heating a divinyl complex (C~M~~)RU(CHFCHCOM~)(CH=CH~)~RU(C~M~~) (12) in refluxing toluene. The ethylene molecule coordinated in 10 inserts into the Ru-C bond of the ruthenacyclopentadiene to form (CsMes)Ru(CMe=CHCH=CMeCH=CH2)(p-H)Ru(CsMe5) (16) when 10 is heated in toluene at 110 "C. Regioselective insertion of a,P-unsaturated ketones into the Ru-C bond of the ruthenacycle giving (C5Me5)Ru(CMe=CHCH=CMeCR1=CCOR2) (p-H)Ru(C5Me5) (17, R1 = H, R2 = Me; 18, R1, R2 = (CH2)2; 19, R', R2 = (CH2)3) is demonstrated in the thermolysis of 10 in the presence of methyl vinyl ketone, cyclopentenone, and cyclohexenone. The molecular structures of several of the products are determined by single-crystal X-ray diffraction studies. Crystal data for 2: space group P 2 / a , a = 12.291(2) A, b = 8.521(1) A, c = 10.053(2) A, = 108.52(1)", V = 998.3(3) A3, and Dcdcd = 1.585 g cm3 for Z = 2. Least-squares refinement based on 2391 reflections converged to R = 0.0220 and R, = 0.0220. Crystal data for 6: space group PI, a = 11.335(2) A, b = 14.315(2) A, c = 8.401(2) A, a = 95.09(2)", p = 117,18(1)", y = 94.36(1)", v = 1197.4(6) A3, and D d c d = 1.538 g cm3 for z = 2. Least-squares refinement based on 2621 reflections converged to R = 0.0900 and R, = 0.1581. Crystal data for 9: space group Pbca, a = 17.876(2) A, b = 20.896(2) A, c = 17.690(2) A, V = 6608(1) g cm3, andDcdcd = 1.529 g cm3 for Z = 8. Least-squares refinement based on 2186 reflections converged to R = 0.057 and R, = 0.040. Crystal data for 10: space group P21/n, a = 14.882(2) A, b = 19.718(4) A, c = 8.794(1) A, = 92.30(2)", v = 2578.5(8) A3, and Dcdcd = 1.496 g ~m -~ for z = 4. Least-squares refinement based on 5731 reflections converged to R = 0.044 and R, = 0.041. Crystal data for 13: space group P21/a, a = 17.210(6) A, b = 9.693(6) A, c = 16.037(7) A, p = 100.366(3)", V = 2632(2) A3, andDdcd = 1.506 g ~m -~ for Z = 4. Least-squares refinement based on 3781 reflections converged to R = 0.037 and R, = 0.035. Crystal data for 16: space group E 1 / a , a = 18.814(2) A, b = 9.212(5) A, c = 15.068(5) A, p = 100.31(2)O, V = 2569(2)...

Real-time monitoring of the deposition processes of Aβ1-40 and Aβ1-42 peptides on various seeds has been performed using a 55 MHz wireless quartz-crystal microbalance (QCM) over long-time periods (~40 h). Dissolved peptide solutions were stirred for nucleation and growth of seeds at pH = 7.4 and 4.6, which were immobilized on the sensor chips. The isolated Aβ peptides were then flowed at the neutral pH, focusing on the interaction between the seeds and the monomers (or small multimers), excluding other interactions among seeds and other aggregates. The thioflavin-T fluorescence assay and atomic-force microscopy were used for evaluating structures of the seeds and deposited aggregates. The deposition rate, determined by the frequency decrease, is about 100 monomers/nm(2)/year in the case of fibril formation. The notable deposition behavior was observed in the deposition of Aβ1-40 peptide on Aβ1-42 seeds grown at the lower pH, which can be an important model for Alzheimer's disease.

95; H, 7.31; N, 10.15.4-Amino-5-tert -butyl-rl'-(dimethylamino)bipheny1-3-carbonitrile (8c) was prepared from 0.17 g (0.49 mmol) of 13 in 25 mL of CH3CN by addition of 1 mL of HBF, (40% in ether).After being stirred for 45 min, the solution was treated with lu until an aqueous extract was no longer acidic. The solvent was evaporated, and the residue was several times extracted with ether. The resulting colorless material was recyrstallized from methanol and yielded 70 mg (51%) of 8c: mp 137-138 "C; MS m / z 293 (100, M' ), 278 (28), 263 (10); 'H NMR (90 MHz, CCl,) 6 1.44 (9, 9 H, tert-butyl), 2.95 (s,6 H, N(CH3),), 4.49 (s,2 H, NH,), 6.5-7.6 (m, 6 H, aromatic protons); l R (KBr) 347013390 (NH), 2900 (CH), 2205 (CN). Anal. Calcd for CIOHaN3: C, 77.78; H, 7.90; N, 14.32. Found: C, 77.61; H, 7.71; N, 14.02. Diethyl 2-[3,5-Di-tert-butyl-l-[4-(dimethylamino)-phenyl]-4-imino-2,5-cyclohexadien-1-yllmalonate ( 12). A 2.55-g (16-"01) portion of diethyl malonate was treated with 0.12 g (5.2 "01) of Na dissolved in 20 mL of EtOH. The resulting solution was added to a solution of 4c (from anodic oxidation of 0.28 g (0.86 mmol) of aniline IC) in acetonitrile. After immediate decolorization, the excess of diethylmalonate was evaporated at 100 "C (0.1 Torr). The product 12 was isolated as an oil (yield, 93%): MS m/z 482 (6, M+), 426 (13), 324 (loo), 309 (44), 173 (68); 'H NMR (90 MHz, CDC13), 6 1.13 (t, 6 H, J = 7 Hz, OCH,CH,), 1.31 (8, 18 H, tert-butyl), 2.89 ( 8 , 6 H, N(CH3),), 4.02 (4, J = 7 Hz, OCHzCH3), 4.17 (8, CH(CO0Et)z; the integration of the signals at 4.02 and 4.17 corresponds to 5 H), 6.68 (8, vinylic protons), 6.84 (q, A2Bz, J = 9 Hz, aromatic protons; the integration of the signals between 6.56 and 7.11 corresponds to 6 H), a signal for the NH proton was not found, in CeDe it was detected at 9.98 (9, broad, 1H); IR (KBr) 3400 (NH), 2960 (CH), 1760/1735 (C=O), 1565 (C=N) cm-'. Anal. Calcd for C29H42N204: C, 72.17; H, 8.77; N, 5.80. Found: C, 71.95; H, 8.61; N, 5.72. 1,5-Di-tert -butyl-3-[ 44 dimet hylamino) phenyl]-6-imino-2,4-cyclohexadiene-1-carbonitrile (13) was obtained after addition of a 7% excess of NBu4CN to the electrogenerated solution of 4c (from 0.27 g (0.83 mmol) of IC). It was recrystallized from petroleum ether (30/50), giving yellow crystals (yield, 64%): mp 98 "C dec; MS m / z 349 (1, M+), 324 (2), 293 (loo), 278 (36); 'H NMR (90 MHz, CC1$ 6 1.06 (8, 9 H, tert-butyl), 1.33 (8, 9 H, tert-butyl), 2.99 (9, 6 H, N(CH3),), 5.97 (d, 1 H, J = 2 Hz), 6.60 (d, J = 2 Hz, vinylic protons), 6.91 (9, A2B2, J = 9 Hz, aromatic protons, the integration of the signals between 6.50 and 7.50 corresponds to 5 H), 10.69 (9, broad, 1 H, NH); IR (KBr) 3390 (NH), 2890 (CH), 2225 (CN), 1585/1525 (C=N) cm-' . Anal. Calcd for C23H31N3: C, 79.04; H, 8.94; N, 12.02. Found: C, 79.25; H, 9.12; N, 12.23.Reaction of 4c with Thiophenolate Ion. To a solution of cation 4c (derived from 0.28 g (0.86 mmol) of IC) in acetonitrile were added 1 g of powdered NazCOs and 1 g (9.0 mmol) of thiophenol. From the resulting colorless solution ...

We systematically study the relationship between the ultrasonically induced aggregation behavior of amyloid β 1−40 peptide and acoustic pressures to clarify the dominant mechanism of the aggregation.With ultrasonic irradiation, the thioflavin-T (ThT) level of the Aβ solution rises after a lag time, takes a maximum at ∼5 h, and remains unchanged or decreases. Thus, we monitor the ThT level at 5 h to evaluate the progress of the β-sheet structure and investigate its correlation with the acoustic pressures of fundamental and harmonics waves. The second-harmonics-wave amplitude shows the highest correlation with the ThT level, indicating the dominant contribution of cavitation bubbles to the fibrillation phenomenon. The influence of solution pH and Ar gas are investigated to identify the aggregation mechanism. As a result, local condensation of the peptide due to the high affinity of hydrophobic residues to the bubble-solution interface causes a highly supersaturated solution, leading to precipitation of β-sheet-rich nuclei.

High-frequency (~ 55 MHz) wireless quartz-crystal microbalance biosensor was used for studying heterogeneous deposition behavior of Aβ(1-40) peptide on Aβ(1-42) nuclei, which were grown under the stirring agitation and 200-kHz ultrasonication at pH 2.2, 4.6, and 7.4. The deposition reaction was monitored over 40 h, and the deposition rate was deduced. Among the agitation nuclei, the maximum deposition rate was observed on the nucleus grown at pH 4.6. However, ultrasonication nucleus grown at pH 7.4 produced much larger deposition rate, despite the same β-sheet concentration. This result indicates that local structural modulation is caused in the nucleus by ultrasonication, which adsorbs the Aβ peptide more actively than other nuclei. The resultant deposits clearly show oligomeric structure.