TALEs from a spring -- superelasticity of Tal effector protein structures

A simple force-probe setup is employed to study the mechanical properties of transcription activator-like effector (TALE) proteins in computer experiments. It is shown that their spring-like arrangement benefits superelastic behaviour which is manifested by large-scale global conformational changes along the helical axis, thus linking structure and dynamics in TALE proteins. As evidenced from the measured force-extension curves the dHax3 and PthXo1 TALEs behave like linear springs, obeying Hooke's law, for moderate global structural changes. For larger deformations, however, the proteins exhibit nonlinearities and the structures become stiffer the more they are stretched. Flexibility is not homogeneously distributed over TALE structure, but instead soft spots which correspond to the RVD loop residues and present key agents in the transmission of conformational motions are identified.Comment: 6 pages, 4 figure

Magnetic screening in the hot gluon system

The gluon transverse self-energy of the pure Yang-Mills system at high-temperature is analysed in the static limit and at fourth order in the coupling. Possible contributions to this function are collected, seen to be gauge-fixing independent subsets and shown to vanish all, except those which are either regulators or constituents of the self-energy of Euklidean 3D Yang-Mills theory at zero temperature. The latter self-energy, in turn, is known from the non-perturbative analysis by Karabali and Nair.Comment: 11 pages, latex, correction of prefactor in (24

On the Gluon Plasmon Self-Energy at O(g)

The next-to-leading order contribution \d\P\omn (\o ,\vc q ) to the polarization function of the hot gluon system is analysed at non-zero wave vectors \vc q \,. Using Braaten-Pisarski resummation and general covariant gauges, \d\P\omn is found to be gauge-fixing independent and transverse on the longitudinal mass-shell. The real part of the longitudinal component \d\P_\ell is UV and IR stable (for real $q$). At imaginary $q$ it is IR singular, and at the point \o=0, $q^2=-3m^2$ it coincides with the result of Rebhan for next-to-leading order Debye screening. When $q$ approaches the lightcone, \d\P_\ell diverges like 1 / \wu {\o^2 - q^2} , reflecting the breakdown of the Braaten-Pisarski decomposition scheme in this limit.Comment: 14 pages, LaTe

Improved hard-thermal-loop effective action for hot QED and QCD

The conventional results for hard thermal loops, which are the building blocks of resummed perturbation theory in thermal field theories, have collinear singularities when external momenta are light-like. It is shown that by taking into account asymptotic thermal masses these singularities are removed. The thus improved hard thermal loops can be summarized by compact gauge-invariant effective actions, generalizing the ones found by Taylor and Wong, and by Braaten and Pisarski.Comment: 21 pages, LaTeX, requires elsart.sty and epsf.sty, 1 postscript figure, compressed and uuencoded, (new reference [9] added

Propagation of Coherent Light Pulses with PHASE

The current status of the software package PHASE for the propagation of coherent light pulses along a synchrotron radiation beamline is presented. PHASE is based on an asymptotic expansion of the Fresnel Kirchhoff integral stationary phase approximation which is usually truncated at the 2nd order. The limits of this approximation as well as possible extensions to higher orders are discussed. The accuracy is benchmarked against a direct integration of the Fresnel Kirchhoff integral. Long range slope errors of optical elements can be included by means of 8th order polynomials in the optical element coordinates w and l. Only recently, a method for the description of short range slope errors has been implemented. The accuracy of this method is evaluated and examples for realistic slope errors are given. PHASE can be run either from a built in graphical user interface or from any script language. The latter method provides substantial flexibility. Optical elements including apertures can be combined. Complete wave packages can be propagated, as well. Fourier propagators are included in the package, thus, the user may choose between a variety of propagators. Several means to speed up the computation time were tested among them are the parallelization in a multi core environment and the parallelization on a cluste

Proof of a mass singularity free property in high temperature QCD

It is shown that three series of diagrams entering the calculation of some hot $QCD$ process, are mass (or collinear) singularity free, indeed. This generalizes a result which was recently established up to the third non trivial order of (thermal) Perturbation Theory.Comment: 40 pages, 3 figures. to be published in J. Math. Phys. no. 44, 200

Structure of the Gluon Propagator at Finite Temperature

The thermal self-energy of gluons generally depends on four Lorentz-invariant functions. Only two of these occur in the hard thermal loop approximation of Braaten and Pisarski because of the abelian Ward identity $K_{\mu}\Pi^{\mu\nu}_{\rm htl}=0$. However, for the exact self-energy $K_{\mu}\Pi^{\mu\nu}\neq 0$. In linear gauges the Slavnov-Taylor identity is shown to require a non-linear relation among three of the Lorentz-invariant self-energy function: $(\Pi_{C})^{2}=(K^{2}-\Pi_{L})\Pi_{D}$. This reduces the exact gluon propagator to a simple form containing only two types of poles: one that determines the behavior of transverse electric and magnetic gluons and one that controls the longitudinally polarized electric gluons.Comment: 21 pages, latex, no figure

Ammonia coordination introducing a magnetic moment in an on-surface low-spin porphyrin

Amazing ammonia: The molecular spin state of Ni(II) porphyrin, supported on a ferromagnetic Co surface, can be reversibly switched between spin-off (S = 0) and spin-on (S = 1) states upon coordination and decoordination of the gaseous ligand NH3, respectively (see picture). This finding clearly indicates the possible use of the system as a single-molecule-based magnetochemical sensor and in spintronics