Photodissociation of HI and DI: testing models for electronic structure via polarization of atomic photofragments

The photodissociation dynamics of HI and DI are examined using time-dependent wave-packet techniques. The orientation and alignment parameters aQ(K) (p) are determined as a function of photolysis energy for the resulting ground-state I(2P(3/2)) and excited-state I(2P(1/2)) atoms. The aQ(K) (p) parameters describe the coherent and incoherent contributions to the angular momentum distributions from the A 1pi(1), a 3pi(1), and t 3sigma(1) electronic states accessed by perpendicular excitation and the a 3pi(0+) state accessed by a parallel transition. The outcomes of the dynamics based on both shifted ab initio results and three empirical models for the potential-energy curves and transition dipole moments are compared and contrasted. It is demonstrated that experimental measurement of the aQ(K) (p) parameters for the excitation from the vibrational ground state (upsilon=0) would be able to distinguish between the available models for the HI potential-energy curves and transition dipole moments. The differences between the aQ(K) (p) parameters for the excitation from upsilon=0 stand in sharp contrast to the scalar properties, i.e., total cross section and I* branching fraction, which require experimental measurement of photodissociation from excited vibrational states (upsilon>0) to distinguish between the models.     

A secretory phospholipase A2-mediated neuroprotection and anti-apoptosis

Background  

Phospholipase A₂ liberates free fatty acids and lysophospholipids upon hydrolysis of phospholipids and these products are often associated with detrimental effects such as inflammation and cerebral ischemia. The neuroprotective effect of neutral phospholipase from snake venom has been investigated.     

A xylobiose-derived isofagomine lactam glycosidase inhibitor binds as its amide tautomer

The atomic-resolution structure of a xylobiose-derived isofagomine lactam in complex with the xylanase Xyn10A from Streptomyces lividans reveals that the lactam is bound to the enzyme as the amide tautomer, with "reversed" protonation-states for nucleophile and acid-base.     

Optimum conditions for superradiant damping

The conditions are investigated under which cooperative or superradiant effects are greatest in an inhomogeneously broadened atomic system that is excited by a coherent light pulse. The coupled non-linear atomic equations of motion are solved numerically for excitation pulses of various areas. It is shown that the absolute intensity of the response decreases strongly with decreasing pulse are below π, but that the relative superradiant contribution increases with decreasing pulse area. The reasons for this are discussed, and it is suggested that excitation by a pulse in the neighborhood of π/2 may represent an optimum compromise for the observation of superradiance.