PubMed · 4525499
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R Bence. Simplified endodontics: chloropercha technique.. https://pubmed.ncbi.nlm.nih.gov/4525499/
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UNLABELLED: Genomic analysis of mycobacteria has become increasingly crucial for understanding drug-resistance mechanisms, molecular epidemiology, and pathogenesis. However, efficient extraction of high-molecular-weight genomic DNA from these organisms remains challenging because of their thick mycolic acid-rich cell walls. In this study, we report the chloroform-bead method, a universal DNA extraction protocol that combines chemical and mechanical disruptions to overcome these challenges. Multi-laboratory evaluation (16 sites) demonstrated the chloroform-bead method's superiority over conventional methods for Mycobacterium tuberculosis (DNA yield: 17.9 vs 1.9 µg, purity A260/A230: 1.86 vs 1.22, both P < 0.001). Single-facility assessment extended these findings to >32 nontuberculous mycobacterial species (n = 1,058), showing performance comparable to M. tuberculosis (n = 1,000), with both achieving median yields of 22.2 µg DNA and consistent quality metrics. The chloroform-bead method significantly reduced the processing time from 2 to 3 days to 2 h while ensuring complete sample sterilization, eliminating the need for species-specific optimization. This streamlined and universally applicable protocol represents a practical advancement in mycobacterial DNA extraction methodology, ideal for high-throughput genomic studies and routine clinical diagnostics. IMPORTANCE: Mycobacterial genomics is crucial for understanding pathogenesis and drug resistance; however, DNA extraction remains a significant challenge because of its unique cell wall. Traditional methods rely on enzymatic treatments, resulting in complex and time-consuming protocols with variable results. The chloroform-bead method introduces a paradigm shift by chemically and mechanically disrupting the mycolic acid layer and eliminating the need for enzymatic treatment. This standardized approach ensures consistent, high-quality DNA extraction across diverse mycobacterial species, thereby enhancing research capabilities and clinical applications.
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We report on the synthesis and self-assembly of a guanosine derivative bearing an alkyloxy side group under different environmental conditions. This derivative was found to spontaneously form ordered supramolecular nanoribbons in which the individual nucleobases are interacting through H-bonds. In toluene and chloroform solutions the formation of gel-like liquid-crystalline phases was observed. Sub-molecularly resolved scanning tunneling microscopic imaging of monolayers physisorbed at the graphite-solution interface revealed highly ordered two-dimensional networks. The recorded intramolecular contrast can be ascribed to the electronic properties of the different moieties composing the molecule, as proven by quantum-chemical calculations. This self-assembly behavior is in excellent agreement with that of 5'-O-acylated guanosines, which are also characterized by a self-assembled motif of guanosines that resembles parallel ribbons. Therefore, for guanosine derivatives (without sterically demanding groups on the guanine base) the formation of supramolecular nanoribbons in solution, in the solid state, and on flat surfaces is universal. This result is truly important in view of the electronic properties of these supramolecular anisotropic architectures and thus for potential applications in the fields of nano- and opto-electronics.