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Bolton Gate Company - Smoke control system - Supercoil rolling smoke curtains Supercoil rolling smoke curtains are designed to restrict the lateral spread of smoke and hot gases along the underside of a roof, ceiling or balcony within a building in the event of fire. They are used as part of a smoke control system to create smoke reservoirs from which smoke and hot gases can be extracted or to stop the spread of smoke allowing valuable time for occupants to escape. Supercoil curtains offer many advantages over other systems on the market, in particular the fact that they can be supplied in large spans in one section with only one drive motor. www.boltongate.co.uk /supercoil.htm   (527 words)

Supercoil The simple figure eight and its topological equivalents is the simplest supercoil, and is the shape a circular DNA assumes to accommodate one too many or one too few helical twists. In fact the noun form "supercoil" is rarely used in the context of DNA topology. "Supercoiling" is an abstract mathematical property, and represents the sum of twist and writhe. www.ebroadcast.com.au /lookup/encyclopedia/su/Supercoil.html   (324 words)

BioMed Central | Full text | The dynamic behavior of bacterial macrofibers growing with one end prevented from ...   (Site not responding. Last check: ) On a solid surface the supercoils moved toward the end permanently blocked from rotating as a result of supercoil rolling over the surface and the formation of new supercoils that reduced fiber length between the initial supercoil and the wire tether. Supercoils that arose in hanging fibers formed short plectonemes that were used to determine the rates at which the fiber shaft rotated during growth. The formation of new supercoils in the region between the tether and the plectoneme was responsible for retraction. www.biomedcentral.com /1471-2180/3/18   (4975 words)

In the Classroom Remove the supercoiling by breaking one strand at the connector and rolling one end of the tubing between your fingers while preventing the other free end from rolling. Supercoil the model into a simple figure eight, so that the double strands cross each other just once, in left-handed fashion (make a 180-degree supercoil, donít make a full turn-remember that the definitions of twist and writhe for this model are based on numbers of crossings). For example, it is common to refer to the enzymes as ìintroducing negative supercoilsî to aid in untwisting DNA for replication or transcription. www.usm.maine.edu /~rhodes/Goodies/text/DNADemo.html   (2564 words)

Supercoiling   (Site not responding. Last check: ) If DNA is in the form of a circular molecule, or if the ends are rigidly held so that it forms a loop, then overtwisting or undertwisting leads to the supercoiled state. Supercoiling occurs when the molecule relieves the helical stress by twisting around itself. Although supercoiling relieves some stress in the molecule, when there is negative supercoiling, further stress can be relieved by partial strand separation. tandem.bu.edu /knex/supercoil.knex.html   (328 words)

DNA supercoil - Wikipedia, the free encyclopedia The simple figure eight is the simplest supercoil, and is the shape a circular DNA assumes to accommodate one too many or one too few helical twists. The noun form "supercoil" is rarely used in the context of DNA topology. The negative supercoiling implies that the DNA is underwound. en.wikipedia.org /wiki/Supercoil   (675 words)

Steve's place - Genomes To add a single negative supercoil to a DNA molecule requires energy of the same magnitude required to separate one base pair. Supercoiling can be used to part ('melt') the DNA double helix. Supercoiling may be involved in initiation of replication. www.steve.gb.com /science/genomes.html   (2543 words)

Preferential relaxation of positively supercoiled DNA by E. coli topoisomerase IV in single-molecule and ensemble ... As the magnets are rotated clockwise, (+) supercoils are removed and the extension of the DNA increases. When the magnets were rotated counterclockwise (0 to ~70 sec) to introduce (+) supercoils, the extension of the molecule did not change, indicating that topo IV was relaxing the supercoils as fast as the magnets could add them. The number of supercoils in the molecule is known precisely from the extension of the DNA. www.genesdev.org /cgi/content/full/14/22/2881   (7492 words)

BCH5425 Molecular Biology and Biotechnology   (Site not responding. Last check: ) This supercoiling increases with the progression of the replication fork. Note that the "duplex" when held between thumb and forefinger and allowed to hang, prefers a "supercoiled" topology, as opposed to "relaxed" [Note: this is usually seen with very skinny tubing, larger diameter tubing may not readily adopt this topology]. In this case, the DNA adopts a negative 0.6 supercoil (about 108° of a right-handed supercoil) which will increase the apparent linkage number from 490 to 490.6 (and achieve 10.6 basepairs per turn in the duplex). wine1.sb.fsu.edu /bch5425/lect07/lect07.htm   (1005 words)

Growth Rate Toxicity Phenotypes and Homeostatic Supercoil Control Differentiate Escherichia coli from Salmonella ... Plasmid DNA was purified, and topoisomers were resolved in a 25-cm 1.0% agarose gel containing 2 µM chloroquine for 46 h at 2.0 V/cm in the first dimension and for 46 h in 20 µM chloroquine for the second dimension. Supercoiling and integration host factor change the DNA conformation and alter the flow of convergent transcription in phage Mu. DNA supercoiling in Escherichia coli is under tight and subtle homeostatic control, involving gene-expression and metabolic regulation of both topoisomerase I and DNA gyrase. jb.asm.org /cgi/content/full/189/16/5839   (6799 words)

[7D] Topoisomerases During replication, the unwinding of DNA may cause the formation of tangling structures, such as supercoils or catenanes. The bacterial topo II is also called the gyrase, which has two functions: (a) to remove the positive supercoils during DNA replication, (2) to introduce negative supercoils (one supercoil for 15-20 turns of the DNA helix) so that the DNA molecule can be packed into the cell. During replication, these negative supercoils are removed by topo I. The bacterial topo IV belongs to the type II topoisomerase. www.web-books.com /moBio/Free/Ch7D.htm   (350 words)

Supercoil smoke curtains Incorporating the Supercoil smoke curtain into your project can reduce the requirements for exhaust and air intake openings due to increased efficiency of smoke channelling. The Supercoil smoke curtain material can be fixed in place to create static smoke baffles. Incorporating Supercoil reservoirs into the smoke venting system in factories and warehouses increases system efficiency and provides cost savings by minimising the requirements for exhaust and air intake openings. www.smokecontrol.com.au /smokecontrol/smokecurtains.htm   (354 words)

Camptothecin-sensitive Relaxation of Supercoiled DNA by the Topoisomerase I-like Activity Associated with ... Camptothecin-sensitive Relaxation of Supercoiled DNA by the Topoisomerase I-like Activity Associated with Poly(ADP-ribose) Polymerase-1 -- Yung et al. B, relaxation of negatively supercoiled DNA was analyzed by using fractions collected from the Ni -nitrilotriacetic acid-agarose column. These fractions were used for silver staining (2 µl) and relaxation assay of DNA supercoils (1 µl). www.jbc.org /cgi/content/full/279/12/11992   (5111 words)

BCH 5425 Molecular Biology and Biotechnology Section 2 Confirm that the "supercoil" twists are actually "left handed" as you look down the supercoil twists (regardless of direction down the twists). Thus, if no supercoiling is introduced, the DNA must adopt a Twist of 9.01 base pairs/turn of the helix within the region ahead of the replication fork. Type II topoisomerases are involved in both decatenation of daughter chromosomes, and relieving the positive supercoiling ahead of the replication fork. www.ufrgs.br /depbiot/blaber/section2/section2.htm   (4579 words)

Supercoiling - definition from Biology-Online.org   (Site not responding. Last check: ) If twisting is in the same direction as the helix, clockwise, which winds the dNA up more tightly, positive supercoiling is generated. Supercoiling in circular DNA can be detected by electrophoresis because supercoiled dNA migrates faster than relaxed DNA. Circular DNA is commonly negatively supercoiled and the DNA of eukaryotes largely exists as supercoils associated with protein in the nucleosome. www.biology-online.org /dictionary/Supercoiling   (222 words)

BioTechniques® Molecular Biology Techniques Forums :: View topic - clone selection Supercoil circular usually gives a smaller size band, plus some fainter bands usually for a fraction of the plasmids being nicked relaxed circles, or linear. Sometimes the end(s) of the DNA insert and vector can be damaged, and the DNA might clone in blunt, with the overhangs knocked off, or in some other odd way. If you confirm inserts, or even if you don't, to be sure what you have you could send some to sequence with primers set in 100 bp, or so, into the vector. molecularbiology.forums.biotechniques.com /forums/viewtopic.php?p=48845   (2209 words)

Supercoil-It - Bayou Biolabs Because this technology is based on enzymatic conversion, and not separation of open circular plasmid from supercoiled plasmid, there is no loss of plasmid in the Supercoil-It purification reaction. Supercoil-It is NOT for use in purifying plasmid for human therapeutic use. Supercoil-It HS does not contain topoisomerase I. Supercoil-It HS produces highly supercoiled plasmid which is supercoiled by DNA gyrase to its thermodynamic limit. www.bayoubiolabs.com /supercoil-It   (262 words)

Vaccinia DNA Topoisomerase I: Evidence Supporting a Free Rotation Mechanism for DNA Supercoil Relaxation To determine the mechanism, single-turnover experiments were done with supercoiled plasmid DNA under conditions in which the topoisomerase cleaves predominantly at a single site per DNA molecule. The concentrations of supercoiled substrate, intermediate topoisomers, and relaxed product vs time were measured by fluorescence imaging, and the rate constants for their interconversion were determined by kinetic simulation. C are in reasonable agreement with those obtained with small oligonucleotide substrates, while the rotation rate of the cleaved DNA strand is fast (~20 rotations/s). pubs.acs.org /cgi-bin/abstract.cgi/bichaw/1997/36/i17/abs/bi962880t.html   (287 words)

A new twist in the collagen story[mdash]the type VI segmented supercoil The two repeats mean that the only way to simultaneously maximize both the hydrophobic and polar interactions during dimer formation is with the molecules antiparallel, overlapped by 75 nm as observed, and supercoiled. We have termed this structure the collagen segmented supercoil. The segmented supercoil and variants may be common aggregation motifs for the non-fibrillar collagens. www.nature.com /emboj/journal/v20/n3/abs/7593544a.html   (256 words)

Investigations of the supercoil-selective DNA binding of wild type p53 suggest a novel mechanism for controlling p53 ...   (Site not responding. Last check: ) Mazur, S.J., Sakaguchi, K., Appella, E., Wang, X.W., Harris, C.C. and Bohr, V.A. (1999) Preferential binding of tumor suppressor p53 to positively or negatively supercoiled DNA involves the C-terminal domain. Brazda, V., Palecek, J., Pospisilova, S., Vojtesek, B. and Palecek, E. (2000) Specific modulation of p53 binding to consensus sequence within supercoiled DNA by monoclonal antibodies. Palecek, E., Brazdova, M., Cernocka, H., Vlk, D., Brazda, V. and Vojtesek, B. (1999) Effect of transition metals on binding of p53 protein to supercoiled DNA and to consensus sequence in DNA fragments. content.febsjournal.org /cgi/content/full/271/19/3865   (6655 words)

Electrostatic-Undulatory Theory of Plectonemically Supercoiled DNA -- Ubbink and Odijk 76 (5): 2502 -- Biophysical ... Electrostatic-Undulatory Theory of Plectonemically Supercoiled DNA -- Ubbink and Odijk 76 (5): 2502 -- Biophysical Journal We present an analytical calculation of the electrostatic interaction in a plectonemic supercoil within the Poisson-Boltzmann supercoil may be split into an elastic contribution containing www.biophysj.org /cgi/content/abstract/76/5/2502   (327 words)

PNAS — Transcription-induced barriers to supercoil diffusion in the Salmonella typhimurium chromosome PNAS — Transcription-induced barriers to supercoil diffusion in the Salmonella typhimurium chromosome Transcription-induced barriers to supercoil diffusion in the Salmonella typhimurium chromosome Explaining how supercoil movement is channeled in living chromosomes has been a major problem for 30 years. www.pnas.org /cgi/content/abstract/101/10/3398   (408 words)

DNA Replication Describe the tertiary (supercoiled) structure of DNA and compare the enzymes that create it. Supercoil is the coiling that results from over-twisting the double helix An ATP-dependent, unwinding protein that induces positive supercoil to double helix; "unwinds" double helix student.ttuhsc.edu /medscbu/MyRock/dna.htm   (1114 words)

Oxford University Press | Online Resource Centre | Chapter 2 It is known as the 'leucine zipper' because of the leucine repeats every 7 residues (shown in ball-and-stick representation). Fig 2-7: The structure of collagen, a three-stranded supercoil formed by braiding together three polypeptide chains. The repeat distance of the supercoil is approximately 1 nm static, rotating www.oup.com /uk/orc/bin/9780199265114/resources/anim/ch02   (1411 words)

Citebase - Axial distortion as a sensor of supercoil changes: a molecular model for the homeostatic regulation of DNA ...   (Site not responding. Last check: ) Axial distortion as a sensor of supercoil changes: a molecular model for the homeostatic regulation of DNA gyrase In contrast, transcription of the genes coding for DNA gyrase is subject to a novel mechanism of autoregulation, wherein relaxation of the template DNA stimulates their transcription. Since DNA gyrase is the sole supercoiling activity in the eubacterial cell, relaxation-stimulated transcription (RST) could reflect an autoregulatory mechanism to maintain supercoil levels within the cell. citebase.eprints.org /cgi-bin/citations?id=oai:iiscePrints.OAI2:2031   (257 words)

hyper supercoid band some time when I separate cut and uncut vector with one site only, I can see that the supercoil and relaxed form are now all liniar at the right size, but there is a weak band which is smaller than the supercoil. Perhaps your cells have two populations of plasmids, one of which is either a completely different plasmid or one of them has a mutation at the cut site. You do get different levels of supercoiling of plasmids within bacteria so it may be that the most supercoiled ones can't be cut. www.biology-online.org /biology-forum/about7031.html   (452 words)

Archaeal Histone Tetramerization Determines DNA Affinity and the Direction of DNA Supercoiling -- Marc et al. 277 (34): ... In all cases, the resulting tetramer wraps the DNA molecule in a positive supercoil, whereas the further polymerization of wild type HMfBA molecules under physiologically relevant high salt conditions (41) results in negative supercoiling (Fig. Histone Fold Tetramerization and the Direction of DNA Supercoiling-- The DNA appears sharply kinked in complexes formed at low archaeal histone to DNA ratios (Ref. 36 and Fig. or positive supercoil, and it was argued that the bulky chemical www.jbc.org /cgi/content/full/277/34/30879   (4965 words)

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