Although nature's design of the DNA double helix is ingenious for the storage of information, this design creates topological problems for the processes that occur on the DNA. Cellular processes, such as transcription, replication, chromosomal segregation, and chromosomal condensation, are all complicated by the double helix. The problem is compounded in cells since the DNA is in chromatin. Topoisomerases relax positive and negative superhelical turns in DNA, and thereby topoisomerases have long been recognized as key components of the DNA replication and chromosome segregation and condensation machinery. A role for topoisomerases in the transcription process has also been noted in living cells, but only recently has such a role been recapitulated in the test tube for transcription reactions. New data are discussed that demonstrate that for in vitro transcription reactions, topoisomerases are dispensable when the template is naked DNA, but when the template is reconstituted into chromatin, topoisomerases are required for transcription to proceed efficiently.
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http://dx.doi.org/10.1615/critreveukaryotgeneexpr.v13.i1.10 | DOI Listing |
Food Chem
January 2025
College of Food Science and Engineering, Jilin Agricultural University, Changchun, Jilin, 130118, China; National Engineering Research Center for Wheat and Corn Deep Processing, Changchun, Jilin, 130118, China. Electronic address:
This work revealed the effects of endogenous proteins on the structural, physicochemical, and digestive properties of starch in corn before and after ripening and explored the binding mechanism of proteins with starch. The microstructure showed that the postharvest ripening process resulted in a thinning of the protein layer on the surface of starch particle. After the removal of protein, the uniformity of the sample surface increased, with tiny pores.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Tel Aviv University, University of Pennsylvania, Department of Chemistry, Philadelphia, Pennsylvania 19104, USA and School of Chemistry, Tel Aviv 69978, Israel.
Chiral phonons have been proposed to be involved in various physical phenomena, yet the chirality of molecular normal modes has not been well defined mathematically. Here we examine two approaches for assigning and quantifying the chirality of molecular normal modes in double-helical molecular wires with various levels of twist. First, associating with each normal mode a structure obtained by imposing the corresponding motion on a common origin, we apply the continuous chirality measure (CCM) to quantitatively assess the relationship between the chirality-weighted normal mode spectrum and the chirality of the underlying molecular structure.
View Article and Find Full Text PDFNat Commun
January 2025
Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, USA.
Discharge of wastewater containing nitrate (NO) disrupts aquatic ecosystems even at low concentrations. However, selective and rapid reduction of NO at low concentration to dinitrogen (N) is technically challenging. Here, we present an electrified membrane (EM) loaded with Sn pair-atom catalysts for highly efficient NO reduction to N in a single-pass electrofiltration.
View Article and Find Full Text PDFJ Phys Chem B
January 2025
Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, India.
The microbial aminotransferase enzyme DapC is vital for lysine biosynthesis in various Gram-positive bacteria, including . Characterization of the enzyme's conformational dynamics and identifying the key residues for ligand binding are crucial for the development of effective antimicrobials. This study employs atomistic simulations to explore and categorize the dynamics of DapC in comparison to other classes of aminotransferase.
View Article and Find Full Text PDFDNA double strand breaks (DSBs) are widely considered the most cytotoxic DNA lesions occurring in cells because they physically disrupt the connectivity of the DNA double helix. Homologous recombination (HR) is a high-fidelity DSB repair pathway that copies the sequence spanning the DNA break from a homologous template, most commonly the sister chromatid. How both DNA ends, and the sister chromatid are held in close proximity during HR is unknown.
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