Articles you may be interested inSix-dimensional quantum dynamics of ( v = 0 , j = 0 ) D 2 and of ( v = 1 , j = 0 ) H 2 scattering from Cu (111) We have measured state-to-state scattering in the H 2 -Cu(100) and H 2 -Cu(110) systems for H 2 initially prepared in the vϭ1,Jϭ1 state, for several final (v,J) states. We observe survival in the initial state (vϭ1,Jϭ1), rotational excitation within vϭ1 ͑into vϭ1,Jϭ3), and rotational excitation plus vibrational relaxation into final states (vϭ0,Jϭ5) and (vϭ0,Jϭ7). For each of these final states, we measure the branching fraction ͑relative to the incident vϭ1,Jϭ1 flux͒ and the mean final translational energy. In addition, for rotational excitation from Jϭ1 to 3, the dependence on initial translational energy and surface temperature is measured within vϭ1 and compared with results within vϭ0. Our results are compared with published state-resolved associative desorption results, similar scattering experiments, and recent theoretical calculations.

No abstract

Ultraviolet photodissociation (UVPD) produces rich and informative fragmentation of intact protein ions, but in the case of high mass proteins (>30 kDa) the spectra are congested with overlapping isotope patterns of highly charged fragment ions. In the most congested regions, many fragments cannot be confidently identified even when high-resolution mass analyzers and modern deconvolution algorithms are used. Gas-phase ion–ion proton transfer reactions (PTR), which reduce the charge states of highly charged ions, can be used to alleviate this congestion and facilitate the identification of additional fragment ions when performed following UVPD. We have developed protocols for sequentially performing PTR on multiple populations of ions generated by UVPD in a way that can be tailored to balance the depth of characterization with speed and throughput. The improvements in sequence coverage and fragment identifications are demonstrated for four proteins ranging in size from 29 to 56 kDa. Sequence coverages up to 80% were achieved for carbonic anhydrase (29 kDa), 50% for aldolase (39 kDa), 46% for enolase (46 kDa), and 27% for glutamate dehydrogenase (56 kDa), and up to 74% sequence coverage was obtained for 25 kDa antibody drug conjugate subunits in online LC–MS experiments.

Articles you may be interested inReactive scattering of H2 from Cu(100): Comparison of dynamics calculations based on the specific reaction parameter approach to density functional theory with experiment J. Chem. Phys. 138, 044708 (2013); 10.1063/1.4776224Theoretical evidence for nonadiabatic vibrational deexcitation in H 2 ( D 2 ) state-to-state scattering from Cu ( 100 ) A comparison between experiment and theory is performed for the scattering of (vϭ1, jϭ1) H 2 from Cu͑100͒ at normal incidence. Experimentally, this system was studied using molecular beam techniques, with stimulated Raman pumping employed to overpopulate (vϭ1, jϭ1) in the incident beam, and resonance enhanced multi-photon ionization used to detect the H 2 scattered in two (vϭ1, j) states, and two (vϭ0, j) states. Theoretically, six-dimensional wave packet calculations were performed, employing a new, extended potential energy surface that was computed with density functional theory, using the generalized gradient approximation and a slab representation of the metal surface. Theory and experiment are in good agreement for the survival probability, i.e., the probability for rovibrationally elastic scattering. However, the theory overestimates the probabilities for rotationally inelastic scattering ͑to vϭ1, jϭ3) and for rovibrationally inelastic scattering ͑to vϭ0, jϭ5 and 7͒ for channels that could be determined experimentally. The cause of these discrepancies is discussed, as are possibilities for future improvements in the theory as well as the experiment.

Triblock copolymer brushes were functionalized with nucleic acid sequences, which allowed the polymers to connect head-to-tail and form supramolecular nanostructures. Two approaches were designed and implemented, using either a palindromic DNA attached to both ends of the polymer or two different DNA sequences attached regiospecifically. Given appropriate conditions, the DNA-brush conjugates self-assembled to form either nanoworms with length up to several microns or cross-linked networks. This process is analogous to the step-growth polymerization of small molecule monomers.