Z Anomalous Couplings and the Polarization Asymmetry in γe→Ze\gamma e \to Ze

We extend our previous analysis of the sensitivity of the energy dependence of the polarization asymmetry in $\gamma e \to W\nu$ to the possible existence of anomalous trilinear gauge couplings to the $\gamma e \to Ze$ case. We find that by combining the constraints imposed by both the energy dependence of the total cross section and polarization asymmetry, strong limits on the anomalous $\gamma ZZ$ couplings are obtainable at the Next Linear Collider. Further constraints obtained from a consideration of the angular distribution are briefly discussed.Comment: 24 pages, 8 figures, uuencoded gz-compressed postscript file. To obtain a copy of this paper send e-mail to [email protected]

Distinct Type of Transmission Barrier Revealed by Study of Multiple Prion Determinants of Rnq1

Prions are self-propagating protein conformations. Transmission of the prion state between non-identical proteins, e.g. between homologous proteins from different species, is frequently inefficient. Transmission barriers are attributed to sequence differences in prion proteins, but their underlying mechanisms are not clear. Here we use a yeast Rnq1/[PIN+]-based experimental system to explore the nature of transmission barriers. [PIN+], the prion form of Rnq1, is common in wild and laboratory yeast strains, where it facilitates the appearance of other prions. Rnq1's prion domain carries four discrete QN-rich regions. We start by showing that Rnq1 encompasses multiple prion determinants that can independently drive amyloid formation in vitro and transmit the [PIN+] prion state in vivo. Subsequent analysis of [PIN+] transmission between Rnq1 fragments with different sets of prion determinants established that (i) one common QN-rich region is required and usually sufficient for the transmission; (ii) despite identical sequences of the common QNs, such transmissions are impeded by barriers of different strength. Existence of transmission barriers in the absence of amino acid mismatches in transmitting regions indicates that in complex prion domains multiple prion determinants act cooperatively to attain the final prion conformation, and reveals transmission barriers determined by this cooperative fold