由混合激发钠分子—原子系统产生的强度振荡变化的红外受激喇曼散射

本文报道以等频二步激发钠分子-原子系统,观测到强度随泵浦光的调谐而呈振荡变化的3P—4P受激喇曼散射,以及对应4D—4P和4F—3D跃迁的红外受激辐射和由四波混频产生的816.8～822.1nm区内可调谐相干辐射。文中对这些过程进行了分析讨论。     

Electronic surface structure of <Emphasis Type="Italic">n</Emphasis>-ML Ag/Cu(111) and Cs/<Emphasis Type="Italic">n</Emphasis>-ML Ag/Cu(111) as investigated by 2PPE and STS

We investigated the electronic structure of epitaxially grown silver films on Cu(111) with and without adsorption of cesium by means of scanning tunneling spectroscopy and two-photon photoemission. This system has been chosen as a model system to engineer and measure the dynamics of charge-transfer processes between an adsorbate and a heterogeneous substrate. Special emphasis has been laid on the investigation of the energy shift of the Shockley-type surface state and an excited cesium resonance as a function of Ag film thickness. For the cesium resonance we observe an increase in line width with increasing layer thickness. PACS 68.37.Ef; 68.43.-h; 68.55.Jk; 73.20.-r     

A Study of the Oxidation Pathway of Adrenaline by Cyclic Voltammetry: An Undergraduate Analytical Chemistry Laboratory Exercise

An undergraduate laboratory exercise to be used in an undergraduate instrumental methods course is presented for the electrochemical characterization of oxidation products of adrenaline. An objective of this experiment is to use information obtained through cyclic voltammetry and simulation software to develop a qualitative understanding of the oxidation mechanism of adrenaline.     

Magnetic hyperfine fields in Heusler alloys Co YZ (Y=Ti,Zr; Z=Al,Ga,Sn)

Magnetic hyperfine fields (mhf) acting on Ta at the Ti and Zr sites have been measured in Heusler alloys Co₂TiAl(Ga,Sn) and Co₂ZrAl(Sn) by the TDPAC technique utilizing the 133–482 keV gamma cascade in¹⁸¹Hf. Curie temperatures of all the alloys have also been measured using a vibrating sample magnetometer. Present data together with the existing results on the Co₂HfAl(Ga,Sn) are discussed and compared with the mhf systematics in Heusler alloys.work partially supported by CNEN and CNPq     

On Some Properties of the Hoede-Bakker Index

In this article, we analyze the decisional power index, the so called Hoede-Bakker index. This index takes the preferences of the players into account, as well as the social structure in which players may influence each other. We investigate the properties of the Hoede-Bakker index. We adapt some postulates for power indices and voting power paradoxes for the Hoede-Bakker set up. We investigate whether this decisional power index displays the adapted voting power paradoxes and whether it satisfies the adapted postulates for power indices.     

Characterization of rhodosaminyl transfer by the AknS/AknT glycosylation complex and its use in reconstituting the biosynthetic pathway of aclacinomycin A

The tetracyclic core of anthracycline natural products with antitumor activity such as aclacinomycin A are tailored during biosynthesis by regioselective glycosylation. We report the first synthesis of TDP-L-rhodosamine and demonstrate that the glycosyltransferase AknS transfers L-rhodosamine to the aglycone to initiate construction of the side-chain trisaccharide. The partner protein AknT accelerates AknS turnover rate for L-rhodosamine transfer by 200-fold. AknT does not affect the Km but rather affects the kcat. Using these data, we propose that AknT causes a conformational change in AknS that stabilizes the transition state and ultimately enhances transfer. When the subsequent glycosyltransferase AknK and its substrate TDP-L-fucose are also added to the aglycone, the disaccharide and low levels of a fully reconstituted trisaccharide form of aclacinomycin are observed.     

Haloduracin α binds the peptidoglycan precursor lipid II with 2:1 stoichiometry

The two-peptide lantibiotic haloduracin is composed of two post-translationally modified polycyclic peptides that synergistically act on gram-positive bacteria. We show here that Halα inhibits the transglycosylation reaction catalyzed by PBP1b by binding in a 2:1 stoichiometry to its substrate lipid II. Halβ and the mutant Halα-E22Q were not able to inhibit this step in peptidoglycan biosynthesis, but Halα with its leader peptide still attached was a potent inhibitor. Combined with previous findings, the data support a model in which a 1:2:2 lipid II:Halα:Halβ complex inhibits cell wall biosynthesis and mediates pore formation, resulting in loss of membrane potential and potassium efflux.