Computer controlled antenna system

Digital techniques are discussed for application to the servo and control systems of large antennas. The tracking loop for an antenna at a STADAN tracking site is illustrated. The augmentation mode is also considered

Physical Constraints and Functional Characteristics of Transcription Factor-DNA Interaction

We study theoretical ``design principles'' for transcription factor-DNA interaction in bacteria, focusing particularly on the statistical interaction of the transcription factors (TF's) with the genomic background (i.e., the genome without the target sites). We introduce and motivate the concept of `programmability', i.e. the ability to set the threshold concentration for TF binding over a wide range merely by mutating the binding sequence of a target site. This functional demand, together with physical constraints arising from the thermodynamics and kinetics of TF-DNA interaction, leads us to a narrow range of ``optimal'' interaction parameters. We find that this parameter set agrees well with experimental data for the interaction parameters of a few exemplary prokaryotic TF's. This indicates that TF-DNA interaction is indeed programmable. We suggest further experiments to test whether this is a general feature for a large class of TF's.Comment: 9 pages, 4 figures; revised version as published in PNA

Agri-Horti-PV Research System in North Rhine-Westphalia Including PV Trackers and Integrated Rainwater Harvesting

We present a new Agri-Horti-PV system installed at the end of 2021 in the brown coal area of North Rhine-Westphalia near Jülich, Germany. The system contains different PV installations: Standard south oriented PV modules with a rainwater harvesting set up and east-west tracker modules, of which one is equipped with a rainwater harvesting setup. For the investigation of plant growth under the PV panels and on the reference areas without PV installations a novel rail system allowing for automatic camera movement is integrated in the Agri-Horti-PV park. Using the camera setup plant growth measurements with high spatio-temporal resolution will be possible. The scientific investigations of crop growth and the influence of variable shading conditions controlled by the tracking system started in the growth season of 2022. Here we present the technical details of the system as well as first results of an experiment carried out with faba beans, assessing impact of the Horti-PV system on growth dynamics and leaf morphology

Repressor CopG prevents access of RNA polymerase to promoter and actively dissociates open complexes

Replication of the promiscuous plasmid pMV158 requires expression of the initiator repB gene, which is controlled by the repressor CopG. Genes repB and copG are co-transcribed from promoter Pcr. We have studied the interactions between RNA polymerase, CopG and the promoter to elucidate the mechanism of repression by CopG. Complexes formed at 0°C and at 37°C between RNA polymerase and Pcr differed from each other in stability and in the extent of the DNA contacted. The 37°C complex was very stable (half-life of about 3 h), and shared features with typical open complexes generated at a variety of promoters. CopG protein repressed transcription from Pcr at two different stages in the process leading to the initiation complex. First, CopG hindered binding of RNA polymerase to the promoter. Second, CopG was able to displace RNA polymerase once the enzyme has formed a stable complex with Pcr. A model for the CopG-mediated disassembly of the stable RNA polymerase–Pcr promoter complex is presented

Crystal structure and centromere binding of the plasmid segregation protein ParB from pCXC100

Plasmid pCXC100 from the Gram-positive bacterium Leifsonia xyli subsp. cynodontis uses a type Ib partition system that includes a centromere region, a Walker-type ATPase ParA and a centromere-binding protein ParB for stable segregation. However, ParB shows no detectable sequence homology to any DNA-binding motif. Here, we study the ParB centromere interaction by structural and biochemical approaches. The crystal structure of the C-terminal DNA-binding domain of ParB at 1.4 Å resolution reveals a dimeric ribbon–helix–helix (RHH) motif, supporting the prevalence of RHH motif in centromere binding. Using hydroxyl radical footprinting and quantitative binding assays, we show that the centromere core comprises nine uninterrupted 9-nt direct repeats that can be successively bound by ParB dimers in a cooperative manner. However, the interaction of ParB with a single subsite requires 18 base pairs covering one immediate repeat as well as two halves of flanking repeats. Through mutagenesis, sequence specificity was determined for each position of an 18-bp subsite. These data suggest an unique centromere recognition mechanism by which the repeat sequence is jointly specified by adjacent ParB dimers bound to an overlapped region

Structural determinants of specific DNA-recognition by the THAP zinc finger

Human THAP1 is the prototype of a large family of cellular factors sharing an original THAP zinc-finger motif responsible for DNA binding. Human THAP1 regulates endothelial cell proliferation and G1/S cell-cycle progression, through modulation of pRb/E2F cell-cycle target genes including rrm1. Recently, mutations in THAP1 have been found to cause DYT6 primary torsion dystonia, a human neurological disease. We report here the first 3D structure of the complex formed by the DNA-binding domain of THAP1 and its specific DNA target (THABS) found within the rrm1 target gene. The THAP zinc finger uses its double-stranded β-sheet to fill the DNA major groove and provides a unique combination of contacts from the β-sheet, the N-terminal tail and surrounding loops toward the five invariant base pairs of the THABS sequence. Our studies reveal unprecedented insights into the specific DNA recognition mechanisms within this large family of proteins controlling cell proliferation, cell cycle and pluripotency