Artykuły w czasopismach: „12-helix”

1

Henderson, Peter J. F. "The 12-transmembrane helix transporters". Current Opinion in Cell Biology 5, nr 4 (sierpień 1993): 708–21. http://dx.doi.org/10.1016/0955-0674(93)90144-f.

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Fratev, Filip. "PPARγ helix 12 exhibits an antagonist conformation". Physical Chemistry Chemical Physics 18, nr 13 (2016): 9272–80. http://dx.doi.org/10.1039/c5cp06729d.

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Thodupunuri, Prashanth, Sirisha Katukuri, Kallaganti V. S. Ramakrishna, Gangavaram V. M. Sharma, Ajit C. Kunwar, Akella V. S. Sarma i Hans-Jörg Hofmann. "Solvent-Directed Switch of a Left-Handed 10/12-Helix into a Right-Handed 12/10-Helix in Mixed β-Peptides". Journal of Organic Chemistry 82, nr 4 (luty 2017): 2018–31. http://dx.doi.org/10.1021/acs.joc.6b02856.

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Fratev, Filip. "Activation helix orientation of the estrogen receptor is mediated by receptor dimerization: evidence from molecular dynamics simulations". Physical Chemistry Chemical Physics 17, nr 20 (2015): 13403–20. http://dx.doi.org/10.1039/c5cp00327j.

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Fernandes, Carlos, Sophie Faure, Elisabeth Pereira, Vincent Théry, Valérie Declerck, Régis Guillot i David J. Aitken. "12-Helix Folding of Cyclobutane β-Amino Acid Oligomers". Organic Letters 12, nr 16 (20.08.2010): 3606–9. http://dx.doi.org/10.1021/ol101267u.

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Misra, Rajkumar, K. Muruga Poopathi Raja, Hans-Jörg Hofmann i Hosahudya N. Gopi. "Modulating the Structural Properties of α,γ-Hybrid Peptides by α-Amino Acid Residues: Uniform 12-Helix Versus “Mixed” 12/10-Helix". Chemistry - A European Journal 23, nr 65 (3.11.2017): 16644–52. http://dx.doi.org/10.1002/chem.201703871.

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Sölter, Marion, Manfred Köster, Thomas Hollemann, Andreas Brey, Tomas Pieler i Walter Knöchel. "Characterization of a subfamily of related winged helix genes, XFD-12/12′/12″ (XFLIP), during Xenopus embryogenesis". Mechanisms of Development 89, nr 1-2 (grudzień 1999): 161–65. http://dx.doi.org/10.1016/s0925-4773(99)00195-1.

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Hamad, Mohamad A., i Matthew L. Nilles. "Structure-Function Analysis of the C-Terminal Domain of LcrV from Yersinia pestis". Journal of Bacteriology 189, nr 18 (20.07.2007): 6734–39. http://dx.doi.org/10.1128/jb.00539-07.

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ABSTRACT LcrV, a multifunctional protein, acts as a positive regulator of effector protein secretion for the type III secretion system (T3SS) in Yersinia pestis by interaction with the negative regulator LcrG. In this study, LcrV was analyzed to identify regions required for LcrG interaction. Random-linker insertion mutagenesis, deletion analysis, and site-directed mutagenesis of hydrophobic amino acids between residues 290 and 311 allowed the isolation of an LcrV mutant (LcrV L291R F308R) defective for LcrG interaction. The new residues identified in LcrG interaction lie in helix 12 of LcrV; residues in helix 7 of LcrV are known to be involved in LcrG interaction. Helix 7 and helix 12 of LcrV interact to form an intramolecular coiled coil; these new results suggest that the intramolecular coiled coil in LcrV is required for LcrG interaction and activation of the T3SS.

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Shizu, Ryota, Hikaru Nishiguchi, Sarii Tashiro, Takumi Sato, Ayaka Sugawara, Yuichiro Kanno, Takuomi Hosaka, Takamitsu Sasaki i Kouichi Yoshinari. "Helix 12 stabilization contributes to basal transcriptional activity of PXR". Journal of Biological Chemistry 297, nr 3 (wrzesień 2021): 100978. http://dx.doi.org/10.1016/j.jbc.2021.100978.

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Baker, J. E. "Mounting Bennett's double helix on his skew 12-bar linkage". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 222, nr 8 (1.08.2008): 1575–82. http://dx.doi.org/10.1243/09544062jmes875.

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The many facets of Bennett's investigation into his skew four-bar linkage and its several extensions have given rise to an abundance of studies by other workers. Among his imaginative endeavours was the deployment of a double helix to convert his planar 12-bar network into a spatial counterpart. A geometrically attractive idea, its algebraic equivalent had been difficult to realize because of a lack of underlying analytical relationships. As well, recent papers have revealed apparent shortcomings in Bennett's representation. The present work is an attempt to provide a complete algebraic treatment of Bennett's novel device.

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Munch, A. S., G. H. Kedar, J. R. T. van Weering, S. Vazquez-Sanchez, E. He, T. Andre, T. Braun, T. H. Sollner, M. Verhage i J. B. Sorensen. "Extension of Helix 12 in Munc18-1 Induces Vesicle Priming". Journal of Neuroscience 36, nr 26 (29.06.2016): 6881–91. http://dx.doi.org/10.1523/jneurosci.0007-16.2016.

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Bruning, John B., Michael J. Chalmers, Swati Prasad, Scott A. Busby, Theodore M. Kamenecka, Yuanjun He, Kendall W. Nettles i Patrick R. Griffin. "Partial Agonists Activate PPARγ Using a Helix 12 Independent Mechanism". Structure 15, nr 10 (październik 2007): 1258–71. http://dx.doi.org/10.1016/j.str.2007.07.014.

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Wu, Yun-Dong, i De-Ping Wang. "Theoretical Study on Side-Chain Control of the 14-Helix and the 10/12-Helix of β-Peptides". Journal of the American Chemical Society 121, nr 40 (październik 1999): 9352–62. http://dx.doi.org/10.1021/ja990955l.

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Setiawan, Muchammad Rofiq Fajar, i Aryo Baskoro Utomo. "The Effect of Parasitic Rings and Ground Plane on Helix Strip Antenna". IJITEE (International Journal of Information Technology and Electrical Engineering) 4, nr 2 (16.09.2020): 47. http://dx.doi.org/10.22146/ijitee.55807.

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Strip helix antennas offer better performance at wide bandwidth and more compact in size than conventional helix antennas. However, strip helix antennas have a relatively low gain compared to conventional helix antennas. In this paper, a strip helix antenna with 2.4 GHz frequency was designed, simulated, fabricated, and measured. This strip helix antenna was added with several parasitic rings, and its ground plane size was reduced to increase the gain value and its performance. The best simulation results according to the desired parameters were with return loss < -10 dB of -10.366 dB, VSWR < 2 of 1.8702, and directional radiation pattern of 66.5° beamwidth angle. However, the gain did not match with the desired parameters > 12 dB with the result of 8.9612 dB. Measured results showed that the helix strip antenna has a return loss of -10.37 dB and VSWR of 1.870. The parasitic rings addition can increase the strip helix antenna gain of 0.0201 dB and improves performances of return loss, VSWR, and bandwidth. Despite that, the ground plane size reduction actually decreases the gain value.

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Fithriyah, Rhabiah El. "Kombinasi penggunaan quadhelix dan tanggul gigitan posterior pada perawatan crossbite anterior". Majalah Kedokteran Gigi Indonesia 2, nr 1 (3.01.2017): 47. http://dx.doi.org/10.22146/majkedgiind.12316.

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Combination quad helix and bite riser posterior for anterior crossbite treatment. Anterior crossbite treatment can be done with the appliances either by removable appliances or fixed appliances. One fixed appliance that can be used in the treatment of anterior crossbite is a quad helix with a combination of bite raiser posterior. It is the preferred appliance for correction of maxillary dental constriction in a preadolescent child. Quad helix is activated by widening the anterior or posterior helices. An 11-year-old female patient referred to the clinic with a problem of crowding teeth that affected her appearance. The diagnosis for her case was malocclusions dentoalveolar class I angle along with anterior crossbite 12 and 21, anterior crowding maxilla with convex face profile, shifted median line, and no TMJ disorder. The treatment plan used a quad helix and bite riser posterior followed by a fixed orthodontic treatment. The aim of this study was to correct the anterior crossbite using a combination of a quad helix and bite raiser posterior. The patient was treated using composite bite raiser posterior on the occlusal surface of 16.26, and quad helix soldered to bands and cemented on 16 and 26. The patient was instructed to get her teeth controlled every two week to activate quad helix. After 3 months of active treatment, anterior crossbite was corrected. The appliance was left passively in place for 3 months as retention. The study concluded that crossbite treatment with a combination of a quad helix and bite riser was effective in correcting anterior crossbite in adolescents.ABSTRAKPerawatan crossbite anterior dapat dilakukan dengan beberapa macam alat baik dengan alat lepasan ataupun alat cekat. Salah satu alat semi cekat yang dapat digunakan pada perawatan crossbite anterior adalah quad helix dengan kombinasi tanggul gigitan posterior. Quad helix merupakan alat yang dapat digunakan untuk konstriksi dental di maksila pada masa remaja. Seorang pasien anak perempuan berusia 11 tahun mengeluhkan keadaan giginya yang berjejal dan menganggu penampilannya. Diagnosis kasus adalah maloklusi dentoalveolar kelas I angle disertai crossbite gigi 12 dan 21, crowding anterior rahang atas dengan profil muka cembung, garis median tidak sesuai dan tidak disertai gangguan TMJ. Rencana perawatan menggunakan quad helix dan tanggul gigitan posterior kemudian dilanjutkan dengan perawatan ortodontik cekat. Tujuan artikel ini adalah menyajikan perawatan crossbite anterior dengan menggunakan kombinasi quad helix dan tanggul gigitan posterior. Pasien dirawat menggunakan tanggul gigitan komposit posterior pada permukaan oklusal gigi 16, 26 dan quad helix yang disolder pada molar band dan disementasi di molar band pada gigi 16 dan 26 kemudian pasien diinstruksikan untuk kontrol setiap dua minggu satu kali kunjungan untuk aktivasi quad helix. Setelah perawatan aktif 3 bulan crossbite anterior telah terkoreksi. Alat ditinggalkan di dalam mulut dalam keadaan pasif selama 3 bulan sebagai retensi. Dapat ditarik kesimpulan bahwa perawatan crossbite dengan kombinasi quad helix dan tanggul gigitan posterior efektif dalam mengoreksi crossbite anterior pada remaja.

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Wigle, Dennis, Warren Ho, Dorothy Lo, Joseph Francis, James H. Eubanks i M. Christopher Wallace. "Altered Expression Levels of SEF-2 and p112 in the Rat Hippocampus after Transient Cerebral Ischemia: Identification by mRNA Differential Display". Journal of Cerebral Blood Flow & Metabolism 19, nr 4 (kwiecień 1999): 435–42. http://dx.doi.org/10.1097/00004647-199904000-00009.

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The authors used mRNA differential display to identify genes whose expression levels are altered in the adult rat hippocampus 24 hours after global ischemia. At this time after challenge, the basic helix-loop-helix transcription factor, SEF-2, and the 26S proteasome complex subunit, p112, were identified as genes whose expression levels are decreased and increased, respectively, in the hippocampus. To determine the spatial and temporal patterns of expression change for each gene, the authors antisense in situ hybridization to paired brain sections of sham-operated and global ischemia-challenged rats at 6, 12, and 24 hours after reperfusion SEF-2 expression was not significantly altered from that of sham-operated controls in any hippocampal subfield at or before 12 hours after challenge. At 24 hours after ischemia, however, SEF-2 expression levels were significantly diminished in the vulnerable CA1 subfield, but not in the less vulnerable CA3 or dentate granule cell subfields. The proteasome p112 subunit gene displayed no change in expression levels at 6 hours after insult; however, an elevated expression was observed at 12 hours after challenge in the dentate granule cell subfield. By 24 hours after challenge, p112 expression was significantly elevated in both the CA1 and dentate granule cell subfields. These results demonstrate that a member of the basic helix-loop-helix family of transcription factors, SEF-2, and the major subunit of the 26S proteasome complex, p112, display altered gene expression in the hippocampus after transient cerebral ischemia.

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Ruszkowska, Agnieszka, Milosz Ruszkowski, Jacob P. Hulewicz, Zbigniew Dauter i Jessica A. Brown. "Molecular structure of a U•A-U-rich RNA triple helix with 11 consecutive base triples". Nucleic Acids Research 48, nr 6 (13.01.2020): 3304–14. http://dx.doi.org/10.1093/nar/gkz1222.

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Abstract Three-dimensional structures have been solved for several naturally occurring RNA triple helices, although all are limited to six or fewer consecutive base triples, hindering accurate estimation of global and local structural parameters. We present an X-ray crystal structure of a right-handed, U•A-U-rich RNA triple helix with 11 continuous base triples. Due to helical unwinding, the RNA triple helix spans an average of 12 base triples per turn. The double helix portion of the RNA triple helix is more similar to both the helical and base step structural parameters of A′-RNA rather than A-RNA. Its most striking features are its wide and deep major groove, a smaller inclination angle and all three strands favoring a C3′-endo sugar pucker. Despite the presence of a third strand, the diameter of an RNA triple helix remains nearly identical to those of DNA and RNA double helices. Contrary to our previous modeling predictions, this structure demonstrates that an RNA triple helix is not limited in length to six consecutive base triples and that longer RNA triple helices may exist in nature. Our structure provides a starting point to establish structural parameters of the so-called ‘ideal’ RNA triple helix, analogous to A-RNA and B-DNA double helices.

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Fillingame, R. H., W. Jiang i O. Y. Dmitriev. "Coupling H(+) transport to rotary catalysis in F-type ATP synthases: structure and organization of the transmembrane rotary motor". Journal of Experimental Biology 203, nr 1 (1.01.2000): 9–17. http://dx.doi.org/10.1242/jeb.203.1.9.

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H(+)-transporting F(1)F(o)-type ATP synthases utilize a transmembrane H(+) potential to drive ATP formation by a rotary catalytic mechanism. ATP is formed in alternating beta subunits of the extramembranous F(1) sector of the enzyme, synthesis being driven by rotation of the gamma subunit in the center of the F(1) molecule between the alternating catalytic sites. The H(+) electrochemical potential is thought to drive gamma subunit rotation by first coupling H(+) transport to rotation of an oligomeric rotor of c subunits within the transmembrane F(o) sector. The gamma subunit is forced to turn with the c(12) oligomeric rotor as a result of connections between subunit c and the gamma and epsilon subunits of F(1). In this essay, we will review recent studies on the Escherichia coli F(o) sector. The monomeric structure of subunit c, determined by nuclear magnetic resonance (NMR), is discussed first and used as a basis for the rest of the review. A model for the structural organization of the c(12) oligomer in F(o), deduced from extensive cross-linking studies and by molecular modeling, is then described. The interactions between the the a(1)b(2) ‘stator’ subcomplex of F(o) and the c(12) oligomer are then considered. A functional interaction between transmembrane helix 4 of subunit a (aTMH-4) and transmembrane helix 2 of subunit c (cTMH-2) during the proton-release step from Asp61 on cTMH-2 is suggested. Current a-c cross-linking data can only be explained by helix-helix swiveling or rotation during the proton transfer steps. A model that mechanically links helix rotation within a single subunit c to the incremental 30 degrees rotation of the c(12) oligomer is proposed. In the final section, the structural interactions between the surface residues of the c(12) oligomer and subunits epsilon and gamma are considered. A molecular model for the binding of subunit epsilon between the exposed, polar surfaces of two subunits c in the oligomer is proposed on the basis of cross-linking data and the NMR structures of the individual subunits.

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Jennings, Barbara H., David M. Tyler i Sarah J. Bray. "Target Specificities of DrosophilaEnhancer of split Basic Helix-Loop-Helix Proteins". Molecular and Cellular Biology 19, nr 7 (1.07.1999): 4600–4610. http://dx.doi.org/10.1128/mcb.19.7.4600.

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ABSTRACT Seven Enhancer of split genes in Drosophila melanogaster encode basic-helix-loop-helix transcription factors which are components of the Notch signalling pathway. They are expressed in response to Notch activation and mediate some effects of the pathway by regulating the expression of target genes. Here we have determined that the optimal DNA binding site for the Enhancer of split proteins is a palindromic 12-bp sequence, 5′-TGGCACGTG(C/T)(C/T)A-3′, which contains an E-box core (CACGTG). This site is recognized by all of the individual Enhancer of split basic helix-loop-helix proteins, consistent with their ability to regulate similar target genes in vivo. We demonstrate that the 3 bp flanking the E-box core are intrinsic to DNA recognition by these proteins and that the Enhancer of split and proneural proteins can compete for binding on specific DNA sequences. Furthermore, the regulation conferred on a reporter gene in Drosophila by three closely related sequences demonstrates that even subtle sequence changes within an E box or flanking bases have dramatic consequences on the overall repertoire of proteins that can bind in vivo.

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Kaduim, Doaa, Zaid Mahmoud i Falah Mousa. "Green Biosynthesis of Iron Oxide Nanoparticles and Testing Their Inhibitory Efficacy Against Some Pathogens". Asian Journal of Water, Environment and Pollution 18, nr 4 (18.11.2021): 119–23. http://dx.doi.org/10.3233/ajw210051.

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The biosynthesis of iron oxide (Fe2O3, also known as haematite) nano particles (NPs) using Hydra helix and Beta vulgaris aqueous extracts were adduced, respectively, where the extracts act as a stabiliser and reductant reagent. The crystal structure and size of particles were investigated using X-ray diffraction (XRD), while the morphology was examined using field emission scanning electron microscopy (FESEM), XRD patterns showed the synthesised nanoparticles with well-crystallised structure from Beta vulgaris extract with size 12 nm, while the results by using Hydra helix showed many peaks back to Goethite phase with 16 nm. The antibacterial and antifungal activity were examined using Staphylococcus (showed inhibition zone diameter 23 mm, 16 mm using Hydra helix and Beta vulgaris, respectively), E. coli (showed no inhibition) and Candida fungi (showed inhibition zone 16 mm, 11 mm using Hydra helix and Beta vulgaris, respectively).

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Henttu, P. M., E. Kalkhoven i M. G. Parker. "AF-2 activity and recruitment of steroid receptor coactivator 1 to the estrogen receptor depend on a lysine residue conserved in nuclear receptors." Molecular and Cellular Biology 17, nr 4 (kwiecień 1997): 1832–39. http://dx.doi.org/10.1128/mcb.17.4.1832.

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Hormone-dependent transcriptional activation by nuclear receptors depends on the presence of a conserved C-terminal amphipathic alpha-helix (helix 12) in the ligand-binding domain. Here we show that a lysine residue, which is conserved in most nuclear receptors in the predicted helix 3, is also required for estrogen-dependent transactivation. The replacement of lysine 366 with alanine appreciably reduced activation function 2 (AF-2) activity without affecting steroid- or DNA-binding activity in the mouse estrogen receptor. The mutation dramatically reduced the ability of the receptor to bind steroid receptor coactivator 1 (SRC-1) but had no effect on receptor-interacting protein 140 (RIP-140) binding, indicating that while their sites of interaction overlap, they are not entirely consistent and in keeping with the proposal that the recruitment of coactivators, such as SRC-1, is required for AF-2 activity. Although the function of RIP-140 remains to be established, RIP-140 appears to be capable of recruiting the basal transcription machinery, since overexpression of the protein markedly increased the transcriptional activity of the mutant receptor. Since the lysine residue is conserved, we propose that it is required, together with residues in helix 12, to form the surface by which members of the nuclear receptor family interact with coactivators.

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Hirai, Teruhisa, Jürgen A. W. Heymann, Peter C. Maloney i Sriram Subramaniam. "Structural Model for 12-Helix Transporters Belonging to the Major Facilitator Superfamily". Journal of Bacteriology 185, nr 5 (1.03.2003): 1712–18. http://dx.doi.org/10.1128/jb.185.5.1712-1718.2003.

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ABSTRACT The major facilitator superfamily includes a large collection of evolutionarily related proteins that have been implicated in the transport of a variety of solutes and metabolites across the membranes of organisms ranging from bacteria to humans. We have recently reported the three-dimensional structure, at 6.5 Å resolution, of the oxalate transporter, OxlT, a representative member of this superfamily. In the oxalate-bound state, 12 helices surround a central cavity to form a remarkably symmetrical structure that displays a well-defined pseudo twofold axis perpendicular to the plane of the membrane as well as two less pronounced, mutually perpendicular pseudo twofold axes in the plane of the membrane. Here, we combined this structural information with sequence information from other members of this protein family to arrive at models for the arrangement of helices in this superfamily of transport proteins. Our analysis narrows down the number of helix arrangements from about a billion starting possibilities to a single probable model for the relative spatial arrangement for the 12 helices, consistent both with our structural findings and with the majority of previous biochemical studies on members of this superfamily.

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Crowley, Emily, Megan L. O’Mara, Catherine Reynolds, D. Peter Tieleman, Janet Storm, Ian D. Kerr i Richard Callaghan. "Transmembrane Helix 12 Modulates Progression of the ATP Catalytic Cycle in ABCB1". Biochemistry 48, nr 26 (7.07.2009): 6249–58. http://dx.doi.org/10.1021/bi900373x.

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Tremmel, Ch, A. Azoitei, M. Schaefer, H. Hollmann i M. Spindler-Barth. "Influence of helix 12 of Ultraspiracle on Drosophila melanogaster ecdysone receptor function". Insect Molecular Biology 20, nr 4 (18.05.2011): 417–28. http://dx.doi.org/10.1111/j.1365-2583.2011.01077.x.

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Sharma, Gangavaram V. M., Thota Anupama Yadav, Kanakaraju Marumudi, Prashanth Thodupunuri, Pothula Purushotham Reddy i Ajit C. Kunwar. "Three-Residue Turn in β-Peptides Nucleated by a 12/10 Helix". Chemistry - An Asian Journal 9, nr 11 (1.09.2014): 3153–62. http://dx.doi.org/10.1002/asia.201402465.

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Shoemaker, Kevin R., Robert Fairman, David A. Schultz, Andrew D. Robertson, Eunice J. York, John M. Stewart i Robert L. Baldwin. "Side-chain interactions in the C-peptide helix: Phe 8 ? His 12+". Biopolymers 29, nr 1 (styczeń 1990): 1–11. http://dx.doi.org/10.1002/bip.360290104.

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Carrillo-Tripp, Mauricio, Yair Reyes, Blanca Delgado-Coello, Jaime Mas-Oliva i Roxana Gutiérrez-Vidal. "Peptide Helix-Y12 as Potential Effector for Peroxisome Proliferator-Activated Receptors". PPAR Research 2023 (15.04.2023): 1–15. http://dx.doi.org/10.1155/2023/8047378.

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Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors involved in the regulation of lipids and glucose metabolism, and immune response. Therefore, they have been considered pharmacological targets for treating metabolic diseases, such as dyslipidemia, atherosclerosis, and non-alcoholic fatty liver disease. However, the available synthetic ligands of PPARs have mild to significant side effects, generating the necessity to identify new molecules that are selective PPAR ligands with specific biological responses. This study aimed to evaluate some components of the atheroprotective and hepatoprotective HB-ATV-8 nanoparticles [the amphipathic peptide Helix-Y12, thermozeaxanthin, thermozeaxanthin-13, thermozeaxanthin-15, and a set of glycolipids], as possible ligands of PPARs through blind molecular docking. According to the change in free energy upon protein–ligand binding, ∆Gb, thermozeaxanthins show a more favorable interaction with PPARs, followed by Helix-Y12. Moreover, Helix-Y12 interacts with most parts of the Y-shaped ligand-binding domain (LBD), surrounding helix 3 of PPARs, and reaching helix 12 of PPARα and PPARγ. As previously reported for other ligands, Tyr314 and Tyr464 of PPARα interact with Helix-Y12 through hydrogen bonds. Several PPARα’s amino acids are involved in the ligand binding by hydrophobic interactions. Furthermore, we identified additional PPARs’ amino acids interacting with Helix-Y12 through hydrogen bonds still not reported for known ligands. Our results show that, from the studied ligand set, the Helix-Y12 peptide and Tzeaxs have the most significant probability of binding to the PPARs’ LBD, suggesting novel ligands for PPARs.

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Buranský, Ivan, Matej Bračík i Vladimír Šimna. "Influence of End Mill Helix Angle on Surface Quality of Aluminium Thin-Walled Parts". Research Papers Faculty of Materials Science and Technology Slovak University of Technology 26, nr 42 (1.06.2018): 177–88. http://dx.doi.org/10.2478/rput-2018-0022.

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Abstract This paper deals with the influence of the end mill helix angle on the flatness and surface quality of aluminium (EN AW 6082) thin-walled parts. The three teeth solid end mills of 12 mm diameter with same and different helix angle of third tooth were designed. The tests were performed using the HSC 105 linear CNC machine and following cutting parameters: cutting speeds (800, 100 and 1200 m.min−1), feed per tooth (0.12 mm), cutting depth (for roughing 10 mm and for finishing 5 mm). Evaluation of surface quality of the processed thin-walled parts shows that the helix angle of the end mills has a significant influence on the surface quality of the thin-walled parts. The best results were obtained in the case of end mill with different 35° helix angle of third tooth and cutting speed 1000 m.min−1.

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Pokhrel, Ranju, Tang Tang i Justin M. Holub. "Monitoring ligand-mediated helix 12 transitions within the human estrogen receptor α using bipartite tetracysteine display". Organic & Biomolecular Chemistry 18, nr 31 (2020): 6063–71. http://dx.doi.org/10.1039/d0ob01234c.

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Espinoza-Sánchez, Rodrigo, Carlos Salvador Peña-Casillas i José Luis Cornejo-Ortega. "Impact of the 4 Helix Model on the Sustainability of Tourism Social Entrepreneurships in Jalisco and Nayarit, Mexico". Sustainability 14, nr 2 (7.01.2022): 636. http://dx.doi.org/10.3390/su14020636.

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Given the uncertain outlook caused by COVID-19, it is important to carry out a review of the conditions in which the collective enterprises are influenced by the four helix model, specifically those dedicated to the sector most affected by the pandemic, tourism, for which raises the question: What have been the results of the four helix model in the social tourism entrepreneurships (STE) of Jalisco and Nayarit? In addition to: the participation of the actors of the four helix model has contributed to face the repercussions of COVID-19? The objective is to identify stakeholder input from the core elements of the four helix model and sustainability to the STEs during COVID-19. The methodology used was qualitative and involved the comparison of information from 12 key stakeholders from the government, social, academic and private sectors through Atlas.ti-8. Some results indicate that from the perception of the participants interviewed, the COVID-19 crisis has promoted innovation, support, and incentives among the four helixes, in which the STEs have benefited. As conclusions, the four helix model is functional to face the adversities of COVID-19 as long as there is planning within the entrepreneurships and the link with said model helix participants.

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Manoj Kumar, A. S., i A. I. Aronson. "Analysis of Mutations in the Pore-Forming Region Essential for Insecticidal Activity of a Bacillus thuringiensis δ-Endotoxin". Journal of Bacteriology 181, nr 19 (1.10.1999): 6103–7. http://dx.doi.org/10.1128/jb.181.19.6103-6107.1999.

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ABSTRACT The Bacillus thuringiensis insecticidal δ-endotoxins have a three-domain structure, with the seven amphipathic helices which comprise domain I being essential for toxicity. To better define the function of these helices in membrane insertion and toxicity, either site-directed or random mutagenesis of two regions was performed. Thirty-nucleotide segments in the B. thuringiensis cry1Ac1gene, encoding parts of helix α4 and the loop connecting helices α4 and α5, were randomly mutagenized. This hydrophobic region of the toxin probably inserts into the membrane as a hairpin. Site-directed mutations were also created in specific surface residues of helix α3 in order to increase its hydrophobicity. Among 12 random mutations in helix α4, 5 resulted in the total loss of toxicity for Manduca sexta and Heliothis virescens, another caused a significant increase in toxicity, and one resulted in decreased toxicity. None of the nontoxic mutants was altered in toxin stability, binding of toxin to a membrane protein, or the ability of the toxin to aggregate in the membrane. Mutations in the loop connecting helices α4 and α5 did not affect toxicity, nor did mutations in α3, which should have enhanced the hydrophobic properties of this helix. In contrast to mutations in helix α5, those in helix α4 which inactivated the toxin did not affect its capacity to oligomerize in the membrane. Despite the formation of oligomers, there was no ion flow as measured by light scattering. Helix α5 is important for oligomerization and perhaps has other functions, whereas helix α4 must have a more direct role in establishing the properties of the channel.

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32

Farboud, Behnom, Herborg Hauksdottir, Yun Wu i Martin L. Privalsky. "Isotype-Restricted Corepressor Recruitment: a Constitutively Closed Helix 12 Conformation in Retinoic Acid Receptors β and γ Interferes with Corepressor Recruitment and Prevents Transcriptional Repression". Molecular and Cellular Biology 23, nr 8 (15.04.2003): 2844–58. http://dx.doi.org/10.1128/mcb.23.8.2844-2858.2003.

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ABSTRACT Retinoic acid receptors (RARs) are ligand-regulated transcription factors that play multiple roles in vertebrate development and differentiation. RARs as a class are capable of both repressing and activating target gene expression. Transcriptional repression is mediated through the recruitment of corepressor proteins such as SMRT. Notably, vertebrates encode three major forms of RARs, α, β, and γ, and these distinct RAR isotypes differ in the ability to recruit a corepressor. RARα strongly interacts with SMRT and can repress target gene transcription, whereas RARβ and -γ interact with SMRT only weakly and fail to repress. We report here the use of a genetic suppressor approach, based on a yeast two-hybrid interaction assay using Saccharomyces cerevisiae, for the isolation of RARβ mutants that have gained the RARα-like corepressor phenotype, i.e., a strong interaction with SMRT and the ability to repress gene expression in vertebrate cells. Analysis of these gain-of-function mutants indicates that the different corepressor interaction properties of RARα, -β and -γ are determined by a gating mechanism through which amino acid differences in the helix 3 region of these receptors influence the position of the receptor C-terminal helix 12 domain. As a consequence, the RARβ and RARγ receptors appear to adopt a constitutively closed helix 12 conformation in the absence of hormone that may approximate the conformation of RARα when bound to hormone agonist. This closed helix 12 conformation in RARβ and RARγ blocks corepressor binding, prevents repression, and permits significant levels of target gene activation even in the absence of hormone. We refer to this phenomenon as a “gate-latch” model of corepressor regulation.

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Przibilla, S., W. W. Hitchcock, M. Szécsi, M. Grebe, J. Beatty, V. C. Henrich i M. Spindler-Barth. "Functional studies on the ligand-binding domain of Ultraspiracle from Drosophila melanogaster". Biological Chemistry 385, nr 1 (5.01.2004): 21–30. http://dx.doi.org/10.1515/bc.2004.004.

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AbstractThe functional insect ecdysteroid receptor is comprised of the ecdysone receptor (EcR) and Ultraspiracle (USP). The ligand-binding domain (LBD) of USP was fused to the GAL4 DNA-binding domain (GAL4-DBD) and characterized by analyzing the effect of site-directed mutations in the LBD. Normal and mutant proteins were tested for ligand and DNA binding, dimerization, and their ability to induce gene expression. The presence of helix 12 proved to be essential for DNA binding and was necessary to confer efficient ecdysteroid binding to the heterodimer with the EcR (LBD), but did not influence dimerization. The antagonistic position of helix 12 is indispensible for interaction between the fusion protein and DNA, whereas hormone binding to the EcR (LBD) was only partially reduced if fixation of helix 12 was disturbed. The mutation of amino acids, which presumably bind to a fatty acid evoked a profound negative influence on transactivation ability, although enhanced transactivation potency and ligand binding to the ecdysteroid receptor was impaired to varying degrees by mutation of these residues. Mutations of one fatty acidbinding residue within the ligand-binding pocket, I323, however, evoked enhanced transactivation. The results confirmed that the LBD of Ultraspiracle modifies ecdysteroid receptor function through intermolecular interactions and demonstrated that the ligand-binding pocket of USP modifies the DNA-binding and transactivation abilities of the fusion protein.

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Cohen, Marshall. "Addendum: Cohen, M.H. OJ 287 as a Rotating Helix. Galaxies 2017, 5, 12". Galaxies 6, nr 2 (28.05.2018): 59. http://dx.doi.org/10.3390/galaxies6020059.

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Zhang, Jinsong, Xiao Hu i Mitchell A. Lazar. "A Novel Role for Helix 12 of Retinoid X Receptor in Regulating Repression". Molecular and Cellular Biology 19, nr 9 (1.09.1999): 6448–57. http://dx.doi.org/10.1128/mcb.19.9.6448.

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ABSTRACT Nutrients, drugs, and hormones influence transcription during differentiation and metabolism by binding to high-affinity nuclear receptors. In the absence of ligand, some but not all nuclear receptors repress transcription as a heterodimer with retinoid X receptor (RXR). Here we define a novel role for helix 12 (H12) in sterically masking the corepressor (CoR) binding site in apo-RXR. Removing H12 converts RXR to a potent transcriptional repressor. The length but not the specific sequence of H12 is critical for masking RXR’s intrinsic repression function. This contrasts with the amphipathic character required for mediating ligand-dependent activation and coactivator recruitment. Physiologically, we show that heterodimerization of RXR with apo-thyroid hormone receptor (TR) unmasks the CoR binding site in RXR and allows the TR-RXR heterodimer to repress. A molecular mechanism that involves sequence-specific interaction between RXR H12 and the coactivator-binding surface of the nuclear receptor is proposed for this heterodimerization-mediated unmasking. Peroxisome proliferator-activated receptor γ does not interact as well with RXR H12, thus explaining its inability to repress transcription as an RXR heterodimer. The requirement to unmask RXR’s latent repression function explains why only certain RXR partners repress transcription.

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36

Fadiel, A., J. Song, D. Tivon, A. Hamza, T. Cardozo i Frederick Naftolin. "Phenytoin Is an Estrogen Receptor α-Selective Modulator That Interacts With Helix 12". Reproductive Sciences 22, nr 2 (25.09.2014): 146–55. http://dx.doi.org/10.1177/1933719114549853.

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Eelen, Guy, Noelia Valle, Yoshiteru Sato, Natacha Rochel, Lieve Verlinden, Pierre De Clercq, Dino Moras, Roger Bouillon, Alberto Muñoz i Annemieke Verstuyf. "Superagonistic Fluorinated Vitamin D3 Analogs Stabilize Helix 12 of the Vitamin D Receptor". Chemistry & Biology 15, nr 10 (październik 2008): 1029–34. http://dx.doi.org/10.1016/j.chembiol.2008.08.008.

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Wang, H., E. Hartswood i D. J. Finnegan. "Pogo transposase contains a putative helix-turn-helix DNA binding domain that recognises a 12 bp sequence within the terminal inverted repeats". Nucleic Acids Research 27, nr 2 (1.01.1999): 455–61. http://dx.doi.org/10.1093/nar/27.2.455.

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Altmayer-Henzien, Amandine, Valérie Declerck, Jonathan Farjon, Denis Merlet, Régis Guillot i David J. Aitken. "Fine Tuning of β-Peptide Foldamers: a Single Atom Replacement Holds Back the Switch from an 8-Helix to a 12-Helix". Angewandte Chemie International Edition 54, nr 37 (23.07.2015): 10807–10. http://dx.doi.org/10.1002/anie.201504126.

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40

Altmayer-Henzien, Amandine, Valérie Declerck, Jonathan Farjon, Denis Merlet, Régis Guillot i David J. Aitken. "Fine Tuning of β-Peptide Foldamers: a Single Atom Replacement Holds Back the Switch from an 8-Helix to a 12-Helix". Angewandte Chemie 127, nr 37 (23.07.2015): 10957–60. http://dx.doi.org/10.1002/ange.201504126.

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41

Hu, Yangyang, Xiaodong Xu, Yingjie Jiang, Guiling Zhang, Weiqi Li, Xiudong Sun, Wei Quan Tian i Yunan Feng. "Double-helix PnLin chains: novel potential nonlinear optical materials". Physical Chemistry Chemical Physics 20, nr 18 (2018): 12618–23. http://dx.doi.org/10.1039/c8cp01116h.

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The structures, circular dichroism (CD) spectra and nonlinear optical (NLO) responses of a series of inorganic double-helix chains, P_nLi_n (n = 6–12), have been investigated using the quantum chemistry method.

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42

Presnell, S. R., i F. E. Cohen. "Topological distribution of four-alpha-helix bundles". Proceedings of the National Academy of Sciences 86, nr 17 (wrzesień 1989): 6592–96. http://dx.doi.org/10.1073/pnas.86.17.6592.

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The four-alpha-helix bundle, a common structural motif in globular proteins, provides an excellent forum for the examination of predictive constraints for protein backbone topology. An exhaustive examination of the Brookhaven Crystallographic Protein Data Bank and other literature sources has lead to the discovery of 20 putative four-alpha-helix bundles. Application of an analytical method that examines the difference between solvent-accessible surface areas in packed and partially unpacked bundles reduced the number of structures to 16. Angular requirements further reduced the list of bundles to 13. In 12 of these bundles, all pairs of neighboring helices were oriented in an anti-parallel fashion. This distribution is in accordance with structure types expected if the helix macro dipole effect makes a substantial contribution to the stability of the native structure. The characterizations and classifications made in this study prompt a reevaluation of constraints used in structure prediction efforts.

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43

Kim, Jeong Hoon, Mee Hyun Lee, Byoung Jin Kim, Jun Hyun Kim, Seong Jun Han, Hak Yeop Kim i Michael R. Stallcup. "Role of aspartate 351 in transactivation and active conformation of estrogen receptor α". Journal of Molecular Endocrinology 35, nr 3 (grudzień 2005): 449–64. http://dx.doi.org/10.1677/jme.1.01846.

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Estrogen-dependent transcriptional activation by estrogen receptor α (ERα) depends on the conformation of helices 3 and 12 in the ligand-binding domain. To better understand the function of helix 3 in ERα, we examined the role of charged residues, which are conserved in most steroid receptors in helix 3, in estrogen-dependent transactivation. The replacement of Asp-351 with lysine (D351K) or leucine (D351 L) completely abolished estrogen-dependent transactivation without affecting estrogen-binding, DNA-binding and homodimerization activities in ERα. The mutations dramatically reduced the ligand-dependent activation function 2 activity and impaired the ability of ERα to bind p160 coactivators. In addition, the D351K mutant effectively inhibited the transcriptional activation activity of wild-type ERα. Furthermore Asp-351 was required not only for the estrogen-dependent conformational change of wild-type ERα but also for the constitutive transcriptional activity and ligand-independent active conformation of ERα mutant Y537N. Similarly, in the orphan nuclear receptor called estrogen-related receptor 3 (ERR3), the replacement of Asp-273 (the corresponding amino acid to Asp-351 in ERα) with lysine abolished constitutive transcriptional activity of ERR3 without affecting DNA-binding activity and impaired the ability of the receptor to interact with p160 coactivators. These data suggest a role of Asp-351 in inducing and stabilizing the active conformation of ERα, and our results experimentally confirm the concept that Asp-351 in helix 3 interacts with the amide hydrogen of L540 in helix 12 to form a transcriptionally competent surface for binding p160 coactivators.

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Marsden, Brian J., Gary S. Shaw i Brian D. Sykes. "Calcium binding proteins. Elucidating the contributions to calcium affinity from an analysis of species variants and peptide fragments". Biochemistry and Cell Biology 68, nr 3 (1.03.1990): 587–601. http://dx.doi.org/10.1139/o90-084.

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This paper describes the sequence homology of calcium-binding proteins belonging to the troponin C superfamily. Specifically, this similarity has been examined for 276 twelve-residue calcium-binding loops. It has been found that, in the calcium-binding loop, several residues appear invariant, regardless of the species of origin or the affinity of the protein. These residues are Asp at position 1 (+ X of the coordinating position of the calcium), Asp or Asn at position 3 (+ Y), Gly at position 6, Ile at position 8, and Glu at position 12 (− Z). It has also been found that conservation of certain residues can vary in similar sites in similar proteins. For example, position 3 (+ Y) in site 3 of troponin C is always an Asn, whereas in calmodulin the residue is always Asp. This study also examined the calcium-binding affinities of peptide fragments comprising the loop, helix–loop, loop–helix, and helix–loop–helix. These were compared with larger enzymatic or chemically generated protein fragments in an effort to understand the various contributions to the calcium-binding affinity of a single-site versus a two-site domain as found in troponin C and calmodulin. Based on free energy differences, it was found that a 34-residue helix–loop–helix peptide represents about 60% of the binding affinity found in the intact protein. Cooperativity with a second calcium binding site accounted for the remaining 40% of the affinity.Key words: calcium-binding proteins, sequence homology, peptide fragments, species variants, calcium affinity.

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Boscá, L., i F. Morán. "Circular dichroism analysis of ligand-induced conformational changes in protein kinase C. Mechanism of translocation of the enzyme from the cytosol to the membranes and its implications". Biochemical Journal 290, nr 3 (15.03.1993): 827–32. http://dx.doi.org/10.1042/bj2900827.

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The structural changes following the binding to protein kinase C (PKC) of activators that promote its translocation to lipid environments were studied by far-u.v. c.d. and intrinsic fluorescence measurements of the protein. In the absence of activators, PKC contained 40% alpha-helix, with an average size of 13 amino acids per alpha-helix segment, and 12% beta-structure as deduced from c.d. spectral analysis while fitting a set of model proteins of known structure. Ligands that promote translocation and activation of the enzyme, such as Ca2+ ions and phorbol esters, produced drastic changes in the c.d. spectra which may be interpreted as a reduction in the average number of consecutive amino acids in the alpha-helix. Most of the total alpha-helix structure was conserved and an increase in beta-structure was produced by active phorbol esters. These activators differentially affected the fluorescence of PKC: phorbol esters shifted the emission maximum to the red, whereas Ca2+ produced a marked decrease in the intensity of the fluorescence emission, suggesting in both cases that tryptophan residues were exposed to increased polar environments after binding of the ligands.

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Wang, Xifang, Juan F. Espinosa i Samuel H. Gellman. "12-Helix Formation in Aqueous Solution with Short β-Peptides Containing Pyrrolidine-Based Residues". Journal of the American Chemical Society 122, nr 19 (maj 2000): 4821–22. http://dx.doi.org/10.1021/ja000093k.

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Kim, Ji Young, You Lee Son i Young Chul Lee. "A role of helix 12 of the vitamin D receptor in SMRT corepressor interaction". Biochemical and Biophysical Research Communications 379, nr 3 (luty 2009): 780–84. http://dx.doi.org/10.1016/j.bbrc.2008.12.156.

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Milbeo, Pierre, Matthieu Simon, Claude Didierjean, Emmanuel Wenger, Emmanuel Aubert, Jean Martinez, Muriel Amblard, Monique Calmès i Baptiste Legrand. "A bicyclic unit reversal to stabilize the 12/14-helix in mixed homochiral oligoureas". Chemical Communications 56, nr 57 (2020): 7921–24. http://dx.doi.org/10.1039/d0cc02902e.

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Karthik, Selvam, Arunachalam Thirugnanasambandam, Pradeep Kumar Mandal i Namasivayam Gautham. "Crystal structure of d(CCGGGGTACCCCGG)2at 1.4 Å resolution". Acta Crystallographica Section F Structural Biology Communications 73, nr 5 (26.04.2017): 259–65. http://dx.doi.org/10.1107/s2053230x17004770.

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The X-ray crystal structure of the DNA tetradecamer sequence d(CCGGGGTACCCCGG)2is reported at 1.4 Å resolution in the tetragonal space groupP41212. The sequence was designed to fold as a four-way junction. However, it forms an A-type double helix in the presence of barium chloride. The metal ion could not be identified in the electron-density map. The crystallographic asymmetric unit consists of one A-type double helix with 12 base pairs per turn, in contrast to 11 base pairs per turn for canonical A-DNA. A large number of solvent molecules have been identified in both the grooves of the duplex and around the backbone phosphate groups.

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Simon, Matthieu, Pierre Milbeo, Hongtao Liu, Christophe André, Emmanuel Wenger, Jean Martinez, Muriel Amblard, Emmanuel Aubert, Baptiste Legrand i Monique Calmès. "12/10‐Helix in Mixed β‐Peptides Alternating Bicyclic and Acyclic β‐Amino Acids: Probing the Relationship between Bicyclic Side Chain and Helix Stability". Chemistry – A European Journal 24, nr 70 (15.11.2018): 18795–800. http://dx.doi.org/10.1002/chem.201804404.

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