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DNA intermediate structures are formed in all major pathways of DNA metabolism. Transmission electron microscopy (TEM) is a tool of choice to study their choreography and has led to major advances in the understanding of these mechanisms, particularly those of homologous recombination (HR) and replication. In this article, we describe specific TEM procedures dedicated to the structural characterization of DNA intermediates formed during these processes. These particular DNA species contain single-stranded DNA regions and/or branched structures, which require controlling both the DNA molecules spreading and their staining for subsequent visualization using dark-field imaging mode. Combining BAC (benzyl dimethyl alkyl ammonium chloride) film hyperphase with positive staining and dark-field TEM allows characterizing synthetic DNA substrates, joint molecules formed during not only assays mimicking HR, but also DNA intermediates.
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http://dx.doi.org/10.1093/biomethods/bpaa012 | DOI Listing |
Neuro Oncol
September 2025
Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA, USA.
Background: Preoperative embolization is hypothesized to reduce blood loss and operative time for meningioma resection, but the impact of preoperative embolization on long-term oncological outcomes and molecular features of meningiomas is incompletely understood. Here we investigate how preoperative embolization influences perioperative and long-term outcomes and molecular features of atypical WHO grade 2 meningiomas.
Methods: Patients who underwent resection of WHO grade 2 meningiomas from 1997 to 2021 were retrospectively identified from an institutional database.
DNA demethylation is essential for gene activation and is primarily mediated by the Ten-Eleven-Translocation (TET) dioxygenase family. TET initiates the demethylation by oxidizing 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), a chemically stable derivative that is not only an intermediate in demethylation but also an epigenetic mark. 5hmC is enriched at active gene bodies, promoters, and enhancers that exist at accessible chromatin.
View Article and Find Full Text PDFJ Am Chem Soc
September 2025
School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
Nitrogen heterocycles are indispensable structural motifs in pharmaceuticals, agrochemicals, and materials science. However, the development of new synthetic methods to access these frameworks remains a significant challenge. Here, we describe a switchable radical approach for the synthesis of 1-azabicyclo[2.
View Article and Find Full Text PDFJ Biol Chem
September 2025
Department of Biochemistry and Molecular Biology, Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA. Electronic address:
Apurinic/Apyrimidinic (AP)-sites are common and highly mutagenic DNA lesions that can arise spontaneously or as intermediates during Base Excision Repair (BER). The enzyme apurinic/apyrimidinic endonuclease 1 (APE1) initiates repair of AP-sites by cleaving the DNA backbone at the AP-site via its endonuclease activity. Here, we investigated the functional role of the APE1 active site residue N174 that contacts the AP-site during catalysis.
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