Diversity and function of phage encoded depolymerases

Bacteriophages of the Podoviridae family often exhibit so-called depolymerases as structural components of the virion. These enzymes appear as tail spike proteins (TSPs). After specific binding to capsular polysaccharides (CPS), exopolysaccharides (EPS) or lipopolysaccharide (LPS) of the host bacteria, polysaccharide-repeating units are specifically cleaved. Finally, the phage reaches the last barrier, the cell wall, injects its DNA, and infects the cell. Recently, similar enzymes from bacteriophages of the Ackermannviridae, Myoviridae, and Siphoviridae families were also described. In this mini-review the diversity and function of phage encoded CPS-, EPS-, and LPSdegrading depolymerases is summarized. The function of the enzymes is described in terms of substrate specificity and applications in biotechnology

On the holomorphic factorization for superconformal fields

For a generic value of the central charge, we prove the holomorphic factorization of partition functions for free superconformal fields which are defined on a compact Riemann surface without boundary. The partition functions are viewed as functionals of the Beltrami coefficients and their fermionic partners which variables parametrize superconformal classes of metrics.Comment: 5 pages, LATEX, MPI-Ph/92-7

An example of resonance saturation at one loop

We argue that the large-Nc expansion of QCD can be used to treat a Lagrangian of resonances in a perturbative way. As an illustration of this we compute the L_10 coupling of the Chiral Lagrangian by integrating out resonance fields at one loop. Given a Lagrangian and a renormalization scheme, this is how in principle one can answer in a concrete and unambiguous manner questions such as at what scale resonance saturation takes place.Comment: 9 pages, 5 figures. Enlarged discussion, results unchanged. To be published in Phys. Rev.

Decay of pseudoscalars into lepton pairs and large-Nc QCD

The counterterm combination that describes the decay of pseudoscalar mesons into charged lepton pairs at lowest order in chiral perturbation theory is considered within the framework of QCD in the limit of a large number of colours Nc. When further restricted to the lowest meson dominance approximation to large-Nc QCD, our results agree well with the available experimental data.Comment: 5 pages, 2 figure

Patterns of Spontaneous Chiral Symmetry Breaking in the Large-Nc Limit of QCD-Like Theories

It is shown that in vector-like gauge theories, such as QCD, and in the limit of a large number of colours Nc, the ordering pattern of narrow vector and axial-vector states at low energies is correlated with the size of the possible local order parameters of chiral symmetry breaking. This has implications on the underlying dynamics of spontaneous chiral symmetry breaking in QCD, and also on possible values of the parameter S for oblique electroweak corrections, the analogue of the QCD low energy constant L10.Comment: 12 pages, 2 figures, plain Late

Geometric approach to condensates in holographic QCD

An SU(Nf)xSU(Nf) Yang-Mills theory on an extra-dimensional interval is considered, with appropriate symmetry-breaking boundary conditions on the IR brane. UV-brane to UV-brane correlators at high energies are compared with the OPE of two-point functions of QCD quark currents. Condensates correspond to departure from AdS of the (different) metrics felt by vector and axial combinations, away from the UV brane. Their effect on hadronic observables is studied: the extracted condensates agree with the signs and orders of magnitude expected from QCD.Comment: References added: published version plus misprints correction

pi-N charge exchange and pi(+)-pi(0) scattering at low energies

pi-N and pi-pi interactions near threshold are uniquely sensitive to the chiral symmetry breaking part of the strong interaction. The pi-N sigma-term value with its implications for nucleon quark structure and the recent controversy concerning the size of the scalar quark condensate have renewed the experimental interest in these two fundamental systems. We report new differential cross sections for the reaction $pi^-p \to \pi^0n$ at 27.5 MeV pion incident kinetic energy, measured between $\theta_{CM} = 0^\circ$ and $55^\circ$. Our results are in excellent agreement with the existing comprehensive pi-N phase shift analysis. We also report on a Chew-Low analysis of exclusive $\pi^+ p \to \pi^+\pi^0p$ data at 260 MeV pion incident energy.Comment: Talk given by D. Pocanic at QULEN97, Osaka, 20-23 May 1997; 4 pages, 2 PostScript figures, writen in LaTeX 2e, uses packages "epsfig" and "espcrc1