Journal articles: 'DNA toroids'

1

Golan, Roxana, Lía I. Pietrasanta, Wan Hsieh, and Helen G. Hansma. "DNA Toroids: Stages in Condensation†." Biochemistry 38, no. 42 (October 1999): 14069–76. http://dx.doi.org/10.1021/bi990901o.

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2

Brewer, Laurence R. "Deciphering the structure of DNA toroids." Integrative Biology 3, no. 5 (2011): 540. http://dx.doi.org/10.1039/c0ib00128g.

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3

Chan, Philip J., Eliza M. Orzylowska, Johannah U. Corselli, John D. Jacobson, and Albert K. Wei. "A Simple Sperm DNA Toroid Integrity Test and Risk of Miscarriage." BioMed Research International 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/780983.

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Current methods of analyzing sperm chromatin competency overlook the inner sperm compartment which is inaccessible to probes and reagents. By breaking the molecular protamine disulfide bridges, the DNA toroids are exposed to integrity analysis. The aim was to develop a simple nuclear toroid test and determine its association with fertilization, pregnancy, and miscarriage. The approach involved treating washed sperm remaining after ICSI procedures (N=35cases) with acidified Triton X-100 and dithiothreitol (DTT) before Diff-Quik staining. Percentages of sperm with normal chromatin indicated by light-colored nuclei were assessed. The toroid integrity test showed more sperm with normal chromatin in the pregnant group (73.6 ± 1.7%, mean ± SEM) when compared with the miscarriage (51.2 ± 6.6%) or nonpregnant groups (60.9 ± 4.8%). Furthermore, the toroid results were correlated with ICSI fertilization (R=0.32,P=0.04) and pregnancy outcome (pregnant cases 73.6 ± 1.7% versus nonpregnant 58.0 ± 3.9%,P=0.001). ROC calculated cut-off was >70.0% for normal toroid integrity (sensitivity 0.98, specificity 0.33, and diagnostic accuracy 78.3%). An association between normal sperm toroid integrity and miscarriage was evident when the staining procedure included acidified detergent DTT pretreatment.

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4

McMillan, Ryan B., Hilary Bediako, Luka Matej Devenica, Yuxing E. Ma, Donna M. Roscoe, and Ashley R. Carter. "DNA Toroids form via a Flower Intermediate." Biophysical Journal 120, no. 3 (February 2021): 34a. http://dx.doi.org/10.1016/j.bpj.2020.11.459.

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5

Hingorani, Manju M., and Mike O'Donnell. "A tale of toroids in DNA metabolism." Nature Reviews Molecular Cell Biology 1, no. 1 (October 2000): 22–30. http://dx.doi.org/10.1038/35036044.

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6

Cherstvy, A. G. "Structure of DNA toroids and electrostatic attraction of DNA duplexes." Journal of Physics: Condensed Matter 17, no. 8 (February 12, 2005): 1363–74. http://dx.doi.org/10.1088/0953-8984/17/8/015.

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7

Wang, Yanwei, Xu Zhang, and Guangcan Yang. "Single molecular analysis of the interaction between DNA and chitosan." RSC Advances 5, no. 37 (2015): 29594–600. http://dx.doi.org/10.1039/c4ra15612a.

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8

Guo, Cunlan, Zhelin Liu, Fugang Xu, Lanlan Sun, Yujing Sun, Tao Yang, and Zhuang Li. "Surface-Relevant Regulable DNA Toroids Induced by Dopamine." Journal of Physical Chemistry B 113, no. 17 (April 30, 2009): 6068–73. http://dx.doi.org/10.1021/jp810126f.

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9

Ubbink, J., and T. Odijk. "Polymer- and salt-induced toroids of hexagonal DNA." Biophysical Journal 68, no. 1 (January 1995): 54–61. http://dx.doi.org/10.1016/s0006-3495(95)80158-x.

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10

Brewer, Laurence R., Laura Cree, Michele Corzett, and Rod Balhorn. "DNA-Protamine Toroids Pull on their Attachment Points." Biophysical Journal 98, no. 3 (January 2010): 477a. http://dx.doi.org/10.1016/j.bpj.2009.12.2600.

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11

van den Broek, Bram, Maarten C. Noom, Joost van Mameren, Christopher Battle, Fred C. MacKintosh, and Gijs J. L. Wuite. "Visualizing the Formation and Collapse of DNA Toroids." Biophysical Journal 98, no. 9 (May 2010): 1902–10. http://dx.doi.org/10.1016/j.bpj.2009.12.4334.

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12

Barberi, Luca, Françoise Livolant, Amélie Leforestier, and Martin Lenz. "Local structure of DNA toroids reveals curvature-dependent intermolecular forces." Nucleic Acids Research 49, no. 7 (March 30, 2021): 3709–18. http://dx.doi.org/10.1093/nar/gkab197.

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Abstract In viruses and cells, DNA is closely packed and tightly curved thanks to polyvalent cations inducing an effective attraction between its negatively charged filaments. Our understanding of this effective attraction remains very incomplete, partly because experimental data is limited to bulk measurements on large samples of mostly uncurved DNA helices. Here we use cryo electron microscopy to shed light on the interaction between highly curved helices. We find that the spacing between DNA helices in spermine-induced DNA toroidal condensates depends on their location within the torus, consistent with a mathematical model based on the competition between electrostatic interactions and the bending rigidity of DNA. We use our model to infer the characteristics of the interaction potential, and find that its equilibrium spacing strongly depends on the curvature of the filaments. In addition, the interaction is much softer than previously reported in bulk samples using different salt conditions. Beyond viruses and cells, our characterization of the interactions governing DNA-based dense structures could help develop robust designs in DNA nanotechnologies.

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13

Leforestier, Amélie, Antonio Šiber, Françoise Livolant, and Rudolf Podgornik. "Protein-DNA Interactions Determine the Shapes of DNA Toroids Condensed in Virus Capsids." Biophysical Journal 100, no. 9 (May 2011): 2209–16. http://dx.doi.org/10.1016/j.bpj.2011.03.012.

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14

Argudo, David, and Prashant K. Purohit. "Competition between Supercoils and Toroids in Single Molecule DNA Condensation." Biophysical Journal 103, no. 1 (July 2012): 118–28. http://dx.doi.org/10.1016/j.bpj.2012.05.033.

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15

McMillan, Ryan B., Hilary A. Bediako, Luka Matej Devenica, Yuxing E. Ma, and Ashley R. Carter. "Protamine Folds DNA into a Flower Shape before Forming Toroids." Biophysical Journal 118, no. 3 (February 2020): 226a. http://dx.doi.org/10.1016/j.bpj.2019.11.1338.

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16

Englander, Joseph, Eugenia Klein, Vlad Brumfeld, Ajay K. Sharma, Aidan J. Doherty, and Abraham Minsky. "DNA Toroids: Framework for DNA Repair in Deinococcus radiodurans and in Germinating Bacterial Spores." Journal of Bacteriology 186, no. 18 (September 15, 2004): 5973–77. http://dx.doi.org/10.1128/jb.186.18.5973-5977.2004.

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17

Shen, M. Richard, Kenneth H. Downing, Rod Balhorn, and Nicholas V. Hud. "Nucleation of DNA Condensation by Static Loops: Formation of DNA Toroids with Reduced Dimensions." Journal of the American Chemical Society 122, no. 19 (May 2000): 4833–34. http://dx.doi.org/10.1021/ja000200a.

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18

Hud, N. V., and K. H. Downing. "Cryoelectron microscopy of phage DNA condensates in vitreous ice: The fine structure of DNA toroids." Proceedings of the National Academy of Sciences 98, no. 26 (December 4, 2001): 14925–30. http://dx.doi.org/10.1073/pnas.261560398.

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19

Li, Yi, Umit Hakan Yildiz, Klaus Müllen, and Franziska Gröhn. "Association of DNA with Multivalent Organic Counterions: From Flowers to Rods and Toroids." Biomacromolecules 10, no. 3 (March 9, 2009): 530–40. http://dx.doi.org/10.1021/bm8011852.

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20

Das, Prolay, and Gary B. Schuster. "One-Electron Oxidation of Condensed DNA Toroids: Injection-Site Dependent Charge (Radical Cation) Mobility." Bioconjugate Chemistry 19, no. 6 (June 2008): 1235–40. http://dx.doi.org/10.1021/bc8000358.

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21

Böttcher, Christoph, Claus Endisch, Jürgen-Hinrich Fuhrhop, Catherine Catterall, and Michael Eaton. "High-Yield Preparation of Oligomeric C-Type DNA Toroids and Their Characterization by Cryoelectron Microscopy." Journal of the American Chemical Society 120, no. 1 (January 1998): 12–17. http://dx.doi.org/10.1021/ja971047w.

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22

Hansma, Helen G., Christine Chen, Roxana Golan, Lia Pietrasanta, Cody Sorenson, Ilene Auerbach, and Patricia Holden. "Probing Biomaterials with the Atomic Force Microscope." Microscopy and Microanalysis 5, S2 (August 1999): 1012–13. http://dx.doi.org/10.1017/s1431927600018389.

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Recent AFM research in our laboratory has covered such diverse biomaterials as laminin and other macromolecules from basement membranes (Fig. 1) (1), DNA condensed for gene therapy (Fig. 2) (2), DNA-protein complexes in the yeast kinetochore (Fig. 3) (3), and biofilms of the bacterium Pseudomonas putida (Fig. 4) (4).Laminin is a major protein of basement membranes. When analyzed by AFM in air, it shows a variety of conformations of its cruciform structure (Fig. 1A). Time-lapse images of a single laminin molecule in aqueous solution show the flexibility of the laminin arms as they move and bend (Fig. 1B)(1).AFM analysis of DNA condensed for receptor-mediated gene therapy poses a puzzle (Fig. 2)(2). Polylysine condenses DNA poorly (Fig. 2A), while AsOR-polylysine condenses DNA into compact toroids and short rods (Fig. 2B). AsOR (asialoorosomucoid) is a 38-kDa glycoprotein with a net negative charge of 5 carboxylic acid groups per molecule. The puzzle is why this negative glycoprotein, covalently attached to polylysine, can enhance the condensation of DNA so much over the condensation caused by the polycation, polylysine, alone.

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23

Mack, A. H., D. J. Schlingman, R. D. Salinas, L. Regan, and S. G. J. Mochrie. "Condensation transition and forced unravelling of DNA-histone H1 toroids: a multi-state free energy landscape." Journal of Physics: Condensed Matter 27, no. 6 (January 7, 2015): 064106. http://dx.doi.org/10.1088/0953-8984/27/6/064106.

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24

Vilfan, Igor D., Christine C. Conwell, Tumpa Sarkar, and Nicholas V. Hud. "Time Study of DNA Condensate Morphology: Implications Regarding the Nucleation, Growth, and Equilibrium Populations of Toroids and Rods†." Biochemistry 45, no. 26 (July 2006): 8174–83. http://dx.doi.org/10.1021/bi060396c.

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25

Thordarson, Pall, Roeland J. M. Nolte, and Alan E. Rowan. "Mimicking the Motion of Life: Catalytically Active Rotaxanes as Processive Enzyme Mimics." Australian Journal of Chemistry 57, no. 4 (2004): 323. http://dx.doi.org/10.1071/ch03302.

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An often overlooked but essential architectural motif found in all living organisms is that of the toroid. Through evolution, nature has used the threading of biopolymers through toroidal assemblies, forming pseudo-rotaxanes, to impart a processive character on the synthesis, replication, repair, and even recombination of DNA. In spite of the fact that numerous processive enzymes have been reported and that life would not exist without such natural rotaxanes, there are virtually no examples of synthetic processive catalysts let alone biomimetic models of these essential and potentially useful systems. To rectify this omission we describe below our recent construction and study of the first catalytic rotaxane molecular machine, which can run along a polymer thread and carry out processive oxidative reactions.

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26

Silva Filho, Claudio Duarte, Edry Antonio Garcia Cisneros, Ingrid Mayumi Fonseca Ono, Raimundo Cláudio Souza Gomes, Angilberto Muniz Ferreira Sobrinho, Fábio de Sousa Cardoso, Fábio Arozo de Albuquerque Júnior, and Israel Gondres Torné. "Análise prática de hélices toroidais prototipadas em manufatura aditiva por estereolitografia." Revista de Gestão e Secretariado 15, no. 7 (July 23, 2024): e3961. http://dx.doi.org/10.7769/gesec.v15i7.3961.

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Hélices são partes comuns em diversos dispositivos do dia a dia, como aviões, ventiladores e drones. Mediante o movimento de rotação, esses equipamentos são capazes de deslocar uma quantidade de ar significativa tornando possível operações como voo de aeronaves e refrigeração de ambientes, no entanto, as suas características de funcionamento ne, sempre estão acorde as regulamentações brasileiras sobre tudo os referentes ao nível de ruido. Nesse contexto varios autores (Zakaria et al, 2020); (Jiang et al, 2022); (Chien et al, 2022) e (Gabriel & Simion, 2023) coincidem em tar estudos analisando a incidência de vários fatores como potência, geometrias das hélices assim como o uso da hélice de tipo toroidal em drones. Neste artigo é apresentada resultados que investigan a eficácia das hélices toroidais, comparando-as com hélices comerciais em "cooler fans" de computadores, focando especialmente na redução de ruido. O objetivo é atender às normas regulamentadoras de níveis de ruído em ambientes laborais e habitados. Utilizando uma impressora 3D do tipo SLA, foram fabricadas hélices toroidais com perfil aerodinâmico NACA 4412, testadas em diferentes rotações para medir vazão e ruído. Os resultados salientam a necessidade de aprimorar a modelagem e simulação dessas hélices utilizando ferramentas de fluidodinâmica computacional para otimizar parâmetros como área de superfície e comprimento da corda do perfil aerodinâmico; o que ajuda a entender que apesar do potencial das hélices toroidais para a redução de ruído, estudos futuros devem focar em modelagem e simulação avançadas para alcançar um desempenho significativo.

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27

SADOC, JEAN-FRANÇOIS. "TOROIDAL DNA: TOPOLOGY, GEOMETRY AND ELECTROSTATICS." International Journal of Modern Physics B 14, no. 07 (March 20, 2000): 737–49. http://dx.doi.org/10.1142/s0217979200000625.

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Toroidal DNA condensates have received considerable attention as a model of ordered DNA condensation. Geometry and topology of fibre bundles can be efficient tools in order to study these structures. Such methods have given fruitful results when considering toroidal vesicles made of amphiphile films and blue phases structures observed in liquid crystals made of long chiral molecules. We give, in this paper, the geometrical arguments supporting this description. Then, we show how electrostatic interactions could be studied using curved spaces. We show that it is possible to have conditions resulting in attractive interaction between DNA molecules in the presence of positive charges.

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28

Kuntz, Victoria D., Alejandra Velasquez, Ryan B. McMillan, and Ashley R. Carter. "Indications of a more complex DNA toroid formation." Biophysical Journal 122, no. 3 (February 2023): 214a. http://dx.doi.org/10.1016/j.bpj.2022.11.1280.

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29

Hingorani, Manju M., and Mike O'Donnell. "Toroidal proteins: Running rings around DNA." Current Biology 8, no. 3 (January 1998): R83—R86. http://dx.doi.org/10.1016/s0960-9822(98)70052-1.

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30

Yoshikawa, Yuko, Kenichi Yoshikawa, and Toshio Kanbe. "Formation of a Giant Toroid from Long Duplex DNA†." Langmuir 15, no. 12 (June 1999): 4085–88. http://dx.doi.org/10.1021/la981159g.

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31

Urban, Maximilian J., Palash K. Dutta, Pengfei Wang, Xiaoyang Duan, Xibo Shen, Baoquan Ding, Yonggang Ke, and Na Liu. "Plasmonic Toroidal Metamolecules Assembled by DNA Origami." Journal of the American Chemical Society 138, no. 17 (April 19, 2016): 5495–98. http://dx.doi.org/10.1021/jacs.6b00958.

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32

Kulić, I. M., D. Andrienko, and M. Deserno. "Twist-bend instability for toroidal DNA condensates." Europhysics Letters (EPL) 67, no. 3 (August 2004): 418–24. http://dx.doi.org/10.1209/epl/i2004-10076-x.

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33

NOGUCHI, HIROSHI. "FOLDING DYNAMICS IN A SEMIFLEXIBLE POLYMER AS A MODEL OF DNA." International Journal of Bifurcation and Chaos 12, no. 09 (September 2002): 2003–8. http://dx.doi.org/10.1142/s0218127402005650.

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We studied the folding transition of a semiflexible homopolymer chain using a Brownian dynamics simulation. A duplex DNA chain exhibits a discrete transition between an elongated coil state and a folded state with toroidal morphology. We show that these folding properties are understood with the stiffness of DNA chains. Semiflexible chains fold through various paths into collapsed toroidal states stochastically. Some chains fold directly by winding around a ring along a chain. Others fold through rod states, which are kinetically trapped metastable states.

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34

Nazif, Hazlif. "PENYEARAH 1 FASA DENGAN FAKTOR DAYA MENDEKATI 1 DAN THD MINIMUM PADA SISTEM TENAGA LISTRIK DENGAN KONTROL ARUS RAMP COMPARISON CURRENT CONTROL." Jurnal Edukasi Elektro 6, no. 1 (May 31, 2022): 42–48. http://dx.doi.org/10.21831/jee.v6i1.44452.

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ABSTRACT:The use of electronic equipment used is increasing in the world of industry, offices, households and transportation. However, this electronic equipment produces a low power factor value and high Total Harmonic Distortion (THD) because in electronic equipment, there are electronic components that are non-linear (diodes, capacitors, transformers and toroids). Therefore, a ramp comparison current control is needed for the boost converter in the electric power system to improve the low power factor and reduce the high THD in the electric power system. The comparison results show that the rectifier without a boost converter produces a power factor value of 0.2252 and THD 268%. This means that the input current waveform is not nearly sinusoidal. Meanwhile, the rectifier with a boost converter using ramp comparison current control produces a power factor value of 0.9207 and a THD of 4%. This means that the input current waveform is nearly sinusoidal. Rectifier with boost converter controlled ramp comparison current control which is better than rectifier without boost converter.ABSTRAK:Pemanfaatan peralatan elektronik yang dipergunakan semakin meningkat dalam dunia industri, perkantoran, rumah tangga dan transportasi. Namun peralatan elektronik ini menghasilkan nilai faktor daya yang rendah dan Total Harmonic Distortion (THD) tinggi karena di dalam peralatan elektronik, terdapat komponen-komponen elektronik yang bersifat non linear (dioda, kapasitor, trafo dan toroida). Oleh karena itu diperlukan kontrol arus ramp comparison current control sebagai konverter boost pada sistem tenaga listrik untuk memperbaiki faktor daya yang rendah dan menurunkan THD yang tinggi pada sistem tenaga listrik. Hasil perbandingan menunjukkan bahwa penyearah tanpa konverter boost menghasilkan nilai faktor daya 0.2252 dan THD 268 %. Hal ini berarti bentuk gelombang arus input tidak mendekati sinusiodal. Sedangkan penyearah dengan konverter boost menggunakan kontrol arus ramp comparison current control menghasilkan nilai faktor daya 0.9207 dan THD 4 %. Hal ini berarti bentuk gelombang arus input mendekati sinusiodal. Penyearah dengan konverter boost yang dikendalikan kontrol arus ramp comparison current control lebih baik daripada penyearah tanpa konverter boost.

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35

Ubbink, J., and T. Odijk. "Deformation of toroidal DNA condensates under surface stress." Europhysics Letters (EPL) 33, no. 5 (February 10, 1996): 353–58. http://dx.doi.org/10.1209/epl/i1996-00346-7.

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36

Sarapat, Pakhapoom, Duangkamon Baowan, and James M. Hill. "Equilibrium location for spherical DNA and toroidal cyclodextrin." Applied Nanoscience 8, no. 3 (March 2018): 537–44. http://dx.doi.org/10.1007/s13204-018-0799-4.

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37

Balhorn, Rod, Laurence Brewer, and Michele Corzett. "DNA condensation by protamine and arginine-rich peptides: Analysis of toroid stability using single DNA molecules." Molecular Reproduction and Development 56, S2 (June 2000): 230–34. http://dx.doi.org/10.1002/(sici)1098-2795(200006)56:2+<230::aid-mrd3>3.0.co;2-v.

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38

Lane, Christopher 1966. "The Testament of the other: Abraham and Torok's failed expiation of ghosts." diacritics 27, no. 4 (1997): 3–29. http://dx.doi.org/10.1353/dia.1997.0031.

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39

Zhang, Min, Lingyun Gu, Yangtao Fan, Yanhui Liu, and Xun Zhou. "Effect of temperature on DNA condensation at single molecule level." Modern Physics Letters B 31, no. 13 (May 10, 2017): 1750147. http://dx.doi.org/10.1142/s0217984917501470.

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DNA condensation by multivalent cations has been extensively studied using single molecule experiment methods. To detect temperature effect on DNA condensation at the single molecule level, a strong correlation model was developed to investigate the behavior of DNA with self-interactions under constant tension. The simulation results are in line with the single molecule experiment that the kinetics of DNA condensation take on discontinuous and stepwise manner regardless of the toroid or rod-like conformation. By incorporating the temperature dependence of DNA persistence length into the strong correlation model, the temperature effect on DNA condensation is identified. The results indicate that condensed DNA conformations at single molecule level become more compact with increasing temperature.

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40

Leforestier, A., and F. Livolant. "Structure of toroidal DNA collapsed inside the phage capsid." Proceedings of the National Academy of Sciences 106, no. 23 (May 22, 2009): 9157–62. http://dx.doi.org/10.1073/pnas.0901240106.

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41

Grosberg, A. Yu, and A. V. Zhestkov. "On the Toroidal Condensed State of Closed Circular DNA." Journal of Biomolecular Structure and Dynamics 3, no. 3 (December 1985): 515–20. http://dx.doi.org/10.1080/07391102.1985.10508438.

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42

Golo, V. L., E. I. Kats, and Yu M. Yevdokimov. "Toroidal Structures Due to Anisotropy of DNA-like Molecules." Journal of Biomolecular Structure and Dynamics 15, no. 4 (February 1998): 757–64. http://dx.doi.org/10.1080/07391102.1998.10508990.

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43

Hud, N. V. "Double-stranded DNA organization in bacteriophage heads: an alternative toroid-based model." Biophysical Journal 69, no. 4 (October 1995): 1355–62. http://dx.doi.org/10.1016/s0006-3495(95)80002-0.

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44

Hirsh, Andrew D., Maryna Taranova, Todd D. Lillian, Troy A. Lionberger, Ioan Andricioaei, and Noel C. Perkins. "Investigating a Novel Toroid-Shaped DNA Structure Found in Mature Bacteriophage φ29." Biophysical Journal 100, no. 3 (February 2011): 401a. http://dx.doi.org/10.1016/j.bpj.2010.12.2384.

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45

Mellies, Jay L., Gregory Benison, William McNitt, David Mavor, Chris Boniface, and Frederick J. Larabee. "Ler of pathogenic Escherichia coli forms toroidal protein–DNA complexes." Microbiology 157, no. 4 (April 1, 2011): 1123–33. http://dx.doi.org/10.1099/mic.0.046094-0.

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Enteropathogenic and enterohaemorrhagic Escherichia coli are related pathotypes of bacteria that cause acute watery diarrhoea and haemorrhagic colitis, respectively, and enterohaemorrhagic E. coli can lead to a serious complication known as haemolytic uraemic syndrome. In both bacteria the global regulatory protein Ler controls virulence. The ler gene is found within the locus of enterocyte effacement, or LEE, encoding a type III secretion system necessary for injecting effector proteins into intestinal epithelial cells and causing net secretory diarrhoea. The nucleoid-associated protein H-NS silences, whereas Ler serves as an anti-silencer of, multiple LEE operons. Although Ler has a higher affinity for DNA than does H-NS, the precise molecular mechanism by which Ler increases LEE transcription remains to be determined. In this report we investigate the oligomerization activity of Ler. In solution, Ler forms dimers and soluble aggregates of up to 5000 kDa molecular mass, and appears to oligomerize more readily than the related protein H-NS. An insertional mutation into the Ler linker region diminished oligomerization activity. Despite being proteins of similar mass and having homologous DNA-binding domains, Ler and H-NS complexed to DNA migrated to distinct locations, as determined by an electrophoretic mobility shift assay, implying that the related proteins form different 3D shapes in the presence of DNA. Lastly, we present electron microscopy images of toroidal Ler–DNA structures that are predicted to be involved in stimulating gene expression.

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46

Eltsov, Mikhail, and Jacques Dubochet. "Fine Structure of the Deinococcus radiodurans Nucleoid Revealed by Cryoelectron Microscopy of Vitreous Sections." Journal of Bacteriology 187, no. 23 (December 1, 2005): 8047–54. http://dx.doi.org/10.1128/jb.187.23.8047-8054.2005.

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ABSTRACT Transmission electron microscopy revealed that the nucleoid of the extremely radioresistant bacteria Deinococcus radiodurans may adopt an unusual ring shape. This led to the hypothesis that the tight toroidal package of the D. radiodurans genome might contribute to radioresistance by preventing diffusion of ends of double-stranded DNA breaks. The molecular arrangement of DNA in the nucleoid, which must be determined to test this hypothesis, is not discernible by conventional methods of electron microscopy. We have applied cryoelectron microscopy of vitreous sections and found that the DNA arrangement in D. radiodurans differs from toroidal spooling. Diffuse coralline nucleoids of exponentially growing D. radiodurans do not reveal any particular molecular order. Electron-dense granules are generally observed in the centers of nucleoids. In stationary-phase cells, the nucleoid segregates from cytoplasm and DNA filaments show locally parallel arrangements, with increasing aspects of cholesteric liquid crystalline phase upon prolonged starvation. The relevance of the observed nucleoid organization to the radiation resistance of D. radiodurans is discussed.

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47

Nurhana, Titik, Guido Dias Kalandro, and Bambang Sri Kaloko. "ANALISIS EFISIENSI TRAFO TOROID STEP DOWN DENGAN MENGGUNAKAN MATERIAL INTI BESI SILICON STEEL DAN GALVALUM." JE-UNISLA 7, no. 2 (September 15, 2022): 77. http://dx.doi.org/10.30736/je-unisla.v7i2.844.

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Trafo toroid merupakan salah satu jenis trafo yang memiliki bentuk inti bulat seperti donat. Prinsip kerjanya sama dengan trafo pada umumnya yaitu dengan menggunakan prinsip induksi elektromagnetik. Dalam bidang industri, trafo biasa digunakan untuk menaikkan tegangan (Step Up) dan menurunkan tegangan (Step Down). Trafo jenis toroid memiliki efisiensi yang lebih baik dibanding dengan trafo jenis lainnya karena bentuk inti yang bulat sehingga tidak ada kebocoran fluks magnetik. Efisiensi trafo dipengaruhi oleh lilitan dan material inti besinya. Penelitian mengenai pengaruh lilitan terhadap kinerja trafo telah banyak dilakukan, sehingga penelitian ini membahas tentang pengaruh material inti besi terhadap efisiensi. Material yang digunakan adalah Grain Oriented Silicon Steel dan seng talang galvalum. Dari kedua material tersebut, diambil nilai daya yang digunakan untuk membandingkan besar efisiensi yang dihasilkan dengan beberapa variasi beban dari tanpa beban, hingga beban lampu pijar 500 watt.

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48

Nirwal, Shivlee, Dhananjaya S. Kulkarni, Amit Sharma, Desirazu N. Rao, and Deepak T. Nair. "Mechanism of formation of a toroid around DNA by the mismatch sensor protein." Nucleic Acids Research 46, no. 1 (November 22, 2017): 256–66. http://dx.doi.org/10.1093/nar/gkx1149.

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Yang, Zhaoqi, Dawei Li, and Tianhu Li. "Design and synthesis of catenated rings based on toroidal DNA structures." Chemical Communications 47, no. 43 (2011): 11930. http://dx.doi.org/10.1039/c1cc14957a.

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Takenaka, Y. "2P105 Self-Organized Ordered Structure of a Single DNA Chain : What does Decide the Morphology of Toroid?" Seibutsu Butsuri 44, supplement (2004): S136. http://dx.doi.org/10.2142/biophys.44.s136_1.

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Journal articles on the topic 'DNA toroids'

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