Using the nonequilibrium Green's function approach and taking into account contributions of both electron and hole, we investigate the spin-dependent carrier transport in a magnetic tunnel junction consisting of a molecular quantum dot coupled to two ferromagnetic leads and to a local vibrational mode. The calculated results show a remarkable influence of electron-phonon interaction and electron-electron interaction on spindependent density of states, charge current, and tunneling magnetoresistance ͑TMR͒. The oscillating TMR is attributed to the phonon-assisted resonant tunneling rather than the well-known charging effect. The behavior of the zero-bias TMR dip or peak depends to a great degree on whether the quantum dot is in the Kondo or non-Kondo regime.

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Serpins form enzymatically inactive covalent complexes (designated E*I*) with their target proteinases, corresponding most likely to the acyl enzyme that resembles the normal intermediate in substrate turnover. Formation of E*I* involves large changes in the conformation of the reactive center loop (residues P17 to P9) and of the serpin molecule in general. The "hinge" region of the reactive center loop, including residues P10 -P14, shows facile movement in and out of ␤-sheet A, and this movement appears to be crucial in determining whether E*I* is formed (the inhibitor pathway) or whether I is rapidly hydrolyzed to I* (the substrate pathway). Here, we report stopped-flow and rapid quench studies investigating the pH dependence of the conversion of the ␣ 1 -antichymotrypsin⅐␣-chymotrypsin encounter complex, E⅐I, to E*I*. These studies utilize fluorescent derivatives of cysteine variants of ␣ 1 -antichymotrypsin at the P11 and P13 residues. Our results demonstrate three identifiable intermediates,

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