A search for deeply bound kaonic nuclear states

We have measured proton and neutron energy spectra by stopping negative kaons on liquid helium4. Two distinct peak structures were found on both spectra, which were assigned to the formation of new kinds of strange stribaryons. In this paper, we summarize both results.Comment: 7 pages, 3 figures, HYP2003 conference proceeding

Evolution of eukaryal tRNA-guanine transglycosylase: insight gained from the heterocyclic substrate recognition by the wild-type and mutant human and Escherichia coli tRNA-guanine transglycosylases

The enzyme tRNA-guanine transglycosylase (TGT) is involved in the queuosine modification of tRNAs in eukarya and eubacteria and in the archaeosine modification of tRNAs in archaea. However, the different classes of TGTs utilize different heterocyclic substrates (and tRNA in the case of archaea). Based on the X-ray structural analyses, an earlier study [Stengl et al. (2005) Mechanism and substrate specificity of tRNA-guanine transglycosylases (TGTs): tRNA-modifying enzymes from the three different kingdoms of life share a common catalytic mechanism. Chembiochem, 6, 1926–1939] has made a compelling case for the divergent evolution of the eubacterial and archaeal TGTs. The X-ray structure of the eukaryal class of TGTs is not known. We performed sequence homology and phylogenetic analyses, and carried out enzyme kinetics studies with the wild-type and mutant TGTs from Escherichia coli and human using various heterocyclic substrates that we synthesized. Observations with the Cys145Val (E. coli) and the corresponding Val161Cys (human) TGTs are consistent with the idea that the Cys145 evolved in eubacterial TGTs to recognize preQ1 but not queuine, whereas the eukaryal equivalent, Val161, evolved for increased recognition of queuine and a concomitantly decreased recognition of preQ1. Both the phylogenetic and kinetic analyses support the conclusion that all TGTs have divergently evolved to specifically recognize their cognate heterocyclic substrates

Doppler Effect in Resonant Photoemission from SF6 : Correlation between Doppler Profile and Auger Emission Anisotropy

Fragmentation of the SF6 molecule upon F 1s excitation has been studied by resonant photoemission. The F atomiclike Auger line exhibits the characteristic Doppler profile that depends on the direction of the photoelectron momentum relative to the polarization vector of the radiation as well as on the photon energy. The measured Doppler profiles are analyzed by the model simulation that takes account of the anisotropy of the Auger emission in the molecular frame. The Auger anisotropy extracted from the data decreases with an increase in the F–SF5 internuclear distance

Interference effects in Auger resonant Raman spectra of CO via selective vibrational excitations across the O 1s-->2pi resonance

The Auger resonant Raman spectra of CO, arising from the transitions to the X and A final electronic states of CO+, have been recorded at photon energies corresponding to the vibrational excitations v[prime]=3,5, and 8 in the O 1s-->2pi resonance. The spectra are simulated within the model that takes into account both the lifetime-vibrational interference (LVI) and interference with the nonresonant photoemission. The spectroscopic parameters, omegae, omegaexe, Gamma and re, of the O 1s–12pi core-excited state, necessary for the simulation, have been derived by fitting the Franck-Condon simulation to the total ion yield spectrum, assuming a Morse potential for the O 1s–12pi state. Not only the LVI but also the interference with the nonresonant photoemission turn out to be significant

Probing doubly excited ionic states of N2+ via a triple excitation above the N 1s threshold in the N2 molecule

Angle-resolved resonant Auger-electron spectroscopy has been carried out on the nitrogen molecule at selected photon energies around 419 eV, where a 1s core electron and two valence electrons are promoted into the lowest unoccupied molecular orbital 1πg. Significant enhancement of a specific band, which cannot be disentangled in direct photoionization, is observed at a binding energy of 37.6 eV, with a value of the anisotropy parameter β much smaller than 2. We assign this new band to the transition to a doubly excited cationic state of N2, in which two of the excited valence electrons remain in the 1πg orbital, proposing a "double spectator" type decay mechanism. This observation shows how to preferentially probe multiply excited configurations of cations using multiple resonant excitation

ADAMTS and ADAM metalloproteinases in osteoarthritis - looking beyond the 'usual suspects'

INTRODUCTION: Matrix metalloproteinases (MMPs) and 'aggrecanase' a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs) are well established to play key roles in osteoarthritis (OA) through degradation of extracellular matrix (ECM) type II collagen and aggrecan, and are thus potential targets for development of OA therapies. OBJECTIVE: This paper aims to provide a comprehensive review of the expression and potential roles of other, lesser-known ADAMTSs and related adamalysins (or a disintegrin and metalloproteinases (ADAMs)) in cartilage, with a view to identifying potentially protective or homeostatic metalloproteinases in the joint and informing consequent selective inhibitor design. DESIGN: A comprehensive literature search was performed using PubMed terms 'osteoarthritis' and 'ADAMTS' or 'ADAM'. RESULTS: Several ADAMTSs and ADAMs were identified as having reportedly increased expression in OA. These include enzymes likely to play roles in cartilage matrix anabolism (e.g., the procollagen N-proteinases ADAMTS-2, ADAMTS-3 and ADAMTS-14), chondrocyte differentiation and proliferation (e.g., ADAM9, ADAM10, ADAM12), as well as enzymes contributing to cartilage catabolism (e.g., Cartilage oligomeric protein (COMP)-degrading ADAMTS-7 and ADAMTS-12). CONCLUSIONS: In addition to the well-characterised MMPs, ADAMTS-4 and ADAMTS-5, many other ADAMTSs and ADAMs are expressed in cartilage and several show significantly altered expression in OA. Studies aimed at elucidating the pathophysiological roles of these enzymes in cartilage will contribute to our understanding of OA pathogenesis and enable design of targeted inhibitors that effectively target metalloproteinase-mediated cartilage degradation while sparing cartilage repair pathways

Dynamics of adherens junctions in epithelial establishment, maintenance, and remodeling

The epithelial cadherin (E-cadherin)–catenin complex binds to cytoskeletal components and regulatory and signaling molecules to form a mature adherens junction (AJ). This dynamic structure physically connects neighboring epithelial cells, couples intercellular adhesive contacts to the cytoskeleton, and helps define each cell’s apical–basal axis. Together these activities coordinate the form, polarity, and function of all cells in an epithelium. Several molecules regulate AJ formation and integrity, including Rho family GTPases and Par polarity proteins. However, only recently, with the development of live-cell imaging, has the extent to which E-cadherin is actively turned over at junctions begun to be appreciated. This turnover contributes to junction formation and to the maintenance of epithelial integrity during tissue homeostasis and remodeling