Ultraviolet‐laser induced dissociation and desorption of water adsorbed on Pd(111)

Ultraviolet‐laser irradiation (6.4 eV and 5.0 eV) of the first layer of water adsorbed on a Pd(111) surface at 90 K leads to desorption of H2O and to conversion of the adsorbed state as manifested in the thermal desorption spectra. The latter effect is attributed to photodissociation of water on the surface. Time‐of‐flight measurements show that water molecules desorb with the same translational energy of about 600 K for both photon energies. While desorption is suppressed with adsorbed multilayers, conversion within the first layer still proceeds

Cross sections and NO product state distributions resulting from substrate mediated photodissociation of NO₂ adsorbed on Pd(111)

Ultraviolet irradiation of NO2 adsorbed on top of a NO saturated Pd(111) surface causes the photodissociation of NO2/N2O4 and results in the desorption of NO molecules. This process has been studied using excitation energies between 3.5 and 6.4 eV. At a photon energy of 6.4 eV, a cross section of 3×10−18 cm2 is found. Using laser‐induced fluorescence to detect the desorbed NO molecules, fully state‐resolved data detailing the energy channeling into different degrees of freedom has been obtained. Two desorption channels are found, one characterized by nonthermal state populations, and one showing accommodation to the surface. The yield of the fast channel shows a marked increase above 4 eV photon energy. The slow channel is interpreted as being due to NO molecules which, after formation, undergo a trapping–desorption process. A polarization experiment indicates that the photodissociation is initiated by excitation of metal electrons rather than direct absorption by the adsorbate

Statistics and Nos\'e formalism for Ehrenfest dynamics

Quantum dynamics (i.e., the Schr\"odinger equation) and classical dynamics (i.e., Hamilton equations) can both be formulated in equal geometric terms: a Poisson bracket defined on a manifold. In this paper we first show that the hybrid quantum-classical dynamics prescribed by the Ehrenfest equations can also be formulated within this general framework, what has been used in the literature to construct propagation schemes for Ehrenfest dynamics. Then, the existence of a well defined Poisson bracket allows to arrive to a Liouville equation for a statistical ensemble of Ehrenfest systems. The study of a generic toy model shows that the evolution produced by Ehrenfest dynamics is ergodic and therefore the only constants of motion are functions of the Hamiltonian. The emergence of the canonical ensemble characterized by the Boltzmann distribution follows after an appropriate application of the principle of equal a priori probabilities to this case. Once we know the canonical distribution of a Ehrenfest system, it is straightforward to extend the formalism of Nos\'e (invented to do constant temperature Molecular Dynamics by a non-stochastic method) to our Ehrenfest formalism. This work also provides the basis for extending stochastic methods to Ehrenfest dynamics.Comment: 28 pages, 1 figure. Published version. arXiv admin note: substantial text overlap with arXiv:1010.149

Clara cell adhesion and migration to extracellular matrix

<p>Abstract</p> <p>Background</p> <p>Clara cells are the epithelial progenitor cell of the small airways, a location known to be important in many lung disorders. Although migration of alveolar type II and bronchiolar ciliated epithelial cells has been examined, the migratory response of Clara cells has received little attention.</p> <p>Methods</p> <p>Using a modification of existing procedures for Clara cell isolation, we examined mouse Clara cells and a mouse Clara-like cell line (C22) for adhesion to and migration toward matrix substrate gradients, to establish the nature and integrin dependence of migration in Clara cells.</p> <p>Results</p> <p>We observed that Clara cells adhere preferentially to fibronectin (Fn) and type I collagen (Col I) similar to previous reports. Migration of Clara cells can be directed by a fixed gradient of matrix substrates (haptotaxis). Migration of the C22 cell line was similar to the Clara cells so integrin dependence of migration was evaluated with this cell line. As determined by competition with an RGD containing-peptide, migration of C22 cells toward Fn and laminin (Lm) 511 (formerly laminin 10) was significantly RGD integrin dependent, but migration toward Col I was RGD integrin independent, suggesting that Clara cells utilize different receptors for these different matrices.</p> <p>Conclusion</p> <p>Thus, Clara cells resemble alveolar type II and bronchiolar ciliated epithelial cells by showing integrin mediated pro-migratory changes to extracellular matrix components that are present in tissues after injury.</p

Novel Pandemic Influenza A(H1N1) Viruses Are Potently Inhibited by DAS181, a Sialidase Fusion Protein

Background: The recent emergence of a novel pandemic influenza A(H1N1) strain in humans exemplifies the rapid and unpredictable nature of influenza virus evolution and the need for effective therapeutics and vaccines to control such outbreaks. However, resistance to antivirals can be a formidable problem as evidenced by the currently widespread oseltamivir- and adamantane-resistant seasonal influenza A viruses (IFV). Additional antiviral approaches with novel mechanisms of action are needed to combat novel and resistant influenza strains. DAS181 (Fludase)™) is a sialidase fusion protein in early clinical development with in vitro and in vivo preclinical activity against a variety of seasonal influenza strains and highly pathogenic avian influenza strains (A/H5N1). Here, we use in vitro, ex vivo, and in vivo models to evaluate the activity of DAS181 against several pandemic influenza A(H1N1) viruses. Methods and Findings: The activity of DAS181 against several pandemic influenza A(H1N1) virus isolates was examined in MDCK cells, differentiated primary human respiratory tract culture, ex-vivo human bronchi tissue and mice. DAS181 efficiently inhibited viral replication in each of these models and against all tested pandemic influenza A(H1N1) strains. DAS181 treatment also protected mice from pandemic influenza A(H1N1)-induced pathogenesis. Furthermore, DAS181 antiviral activity against pandemic influenza A(H1N1) strains was comparable to that observed against seasonal influenza virus including the H274Y oseltamivir-resistant influenza virus. Conclusions: The sialidase fusion protein DAS181 exhibits potent inhibitory activity against pandemic influenza A(H1N1) viruses. As inhibition was also observed with oseltamivir-resistant IFV (H274Y), DAS181 may be active against the antigenically novel pandemic influenza A(H1N1) virus should it acquire the H274Y mutation. Based on these and previous results demonstrating DAS181 broad-spectrum anti-IFV activity, DAS181 represents a potential therapeutic agent for prevention and treatment of infections by both emerging and seasonal strains of IFV.published_or_final_versio

Modern NMR spectroscopy of proteins and peptides in solution and its relevance to drug design

The knowledge of the three-dimensional (3D) structures and conformational dynamics of proteins and peptides is important for the understanding of biochemical and genetic data derived for these molecules. This understanding can ultimately be of help in drug design. We describe here the role of Nuclear Magnetic Resonance (NMR) spectroscopy in this process for three distinct situations: for small proteins, where relatively simple NMR methods can be used for full 3D structure determination; for larger proteins that require multinuclear multidimensional NMR but for which full 3D structures can still be obtained; and for small peptides that are studied in interaction with macromolecules (receptors) using specialized NMR techniques. A fourth situation, pertaining to large systems where only partial structural information can be obtained from NMR data, is briefly discussed. Molecules of interest to the biomedical field (C5a and stromelysin) are discussed as examples.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43356/1/11091_2005_Article_BF02174537.pd