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ABSTRACT JKCS041 ($z=1.8$) is one of the most distant galaxy cluster systems known, seen when the Universe was less than 4 billion years old. Recent Sunyaev–Zeldovich (SZ) observations show a temperature decrement that is less than expected based on mass estimates of the system from X-ray, weak gravitational lensing, and galaxy richness measurements. In this paper, we seek to explain the observables – in particular the low SZ decrement and single SZ peak, the projected offset between the X-ray and SZ peaks of $$\approx$$220 kpc, the gas mass measurements and the lensing mass estimate. We use the gamer-2 hydrodynamic code to carry out idealized numerical simulations of cluster mergers and compare resulting synthetic maps with the observational data. Generically, a merger process is necessary to reproduce the observed offset between the SZ and X-ray peaks. From our exploration of parameter space, seen a few tenths of a Gyr after first core passage, two components with total mass of $$\approx 2\times 10^{14} \,\text{M}_\odot$$, mass ratio of $$\approx$$2:3, gas fraction of $0.05-0.1$, and Navarro, Frenk and White mass density profile concentrations c$$\approx$$ 5 are scenarios that are consistent with the observational data. For consistency with the SZ and X-ray measurements, our simulations exclude total mass in excess of $$\approx 3\times 10^{14} {\rm M}_{\odot }$$, primarily based on the SZ signal. The mass ratio is constrained by the SZ–X-ray offset and magnitude of the SZ signal, ruling out systems with equal and vastly different masses. 

Abstract DNA helicase activity is essential for the vital DNA metabolic processes of recombination, replication, transcription, translation, and repair. Recently, an unexpected, rapid exponential ATP‐stimulated DNA unwinding rate was observed from anArchaeoglobus fulgidushelicase (AfXPB) as compared to the slower conventional helicases fromSulfolobus tokodaii, StXPB1 and StXPB2. This unusual rapid activity suggests a “molecular wrench” mechanism arising from the torque applied by AfXPB on the duplex structure in transitioning from open to closed conformations. However, much remains to be understood. Here, we investigate the concentration dependence of DNA helicase binding and ATP‐stimulated kinetics of StXPB2 and AfXPB, as well as their binding and activity in Bax1 complexes, via an electrochemical assay with redox‐active DNA monolayers. StXPB2 ATP‐stimulated activity is concentration‐independent from 8 to 200 nM. Unexpectedly, AfXPB activity is concentration‐dependent in this range, with exponential rate constants varying from seconds at concentrations greater than 20 nM to thousands of seconds at lower concentrations. At 20 nM, rapid exponential signal decay ensues, linearly reverses, and resumes with a slower exponential decay. This change in AfXPB activity as a function of its concentration is rationalized as the crossover between the fast molecular wrench and slower conventional helicase modes. AfXPB‐Bax1 inhibits rapid activity, whereas the StXPB2‐Bax1 complex induces rapid kinetics at higher concentrations. This activity is rationalized with the crystal structures of these complexes. These findings illuminate the different physical models governing molecular wrench activity for improved biological insight into a key factor in DNA repair.