Dissertations / Theses: 'Helix'

1

Cabeza, Joaquin ZacariÌas. "Molecular mechanisms of helix-loop-helix proteins." Thesis, University of Essex, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442527.

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2

Sieber, Martin Sieber Martin. "DNA binding reaction of basic-helix-loop-helix proteins /." [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13578.

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3

Down, G. "Analysis of helix-loop-helix factors in the skin." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598622.

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There is little data regarding the action of HLH proteins in the skin. I have used RT-PCR Northern blotting analysis, immunocytochemistry (ICC) and in situ hybridisation (ISH) to determine the expression profiles of Id1, Id2, Id3 and Id4 and the Class A factors E2A, E2-2 and HEB mRNAs and proteins during human keratinocyte differentiation both in vivo and in monolayer and organotype in vitro differentiation culture models, and in the human anagen hair follicle, the rat hair follicle growth cycle, and the human sebaceous gland and eccrine sweat gland. Preliminary RT-PCR analysis determined that the Class A factors, E2A, E2-2 and HEB and Id1, Id2 and Id3, and to a very limited extent Id4 mRNAs, were expressed by the epidermis and skin appendages. Northern blotting analysis demonstrated that Ca²⁺ induced cell cycle withdrawal and differentiation of primary human keratinocytes, determined by an up regulation of p21^cip1 and involucrin mRNA expression, was inversely correlated with Id1, Id2 and Id3 mRNA expression. ICC and ISH analysis of human and rat epidermis confirmed Id protein and mRNA expression in the most proliferative layers of the epidermis. The sub-cellular localisation of Id1 protein was predominantly cytoplasmic, whereas that of Id2 and Id3 proteins was predominantly nuclear. Interestingly, a sub-population of supra-basal, post-mitotic keratinocytes also expressed Id1, Id2 and Id3 proteins in which the sub-cellular localisation of each was predominantly nuclear. Supra-basal Id expressing keratinocytes were often seen arranged in stacks extending from the basal layer to the confirmed layers and these cells may be post-mitotic keratinocytes with maintained capacity to re-enter the cell cycle, and may delineate epidermal proliferative units.

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4

Fuchs, Angelika Johanna Maria. "Helix-helix interactions in membrane proteins : analysis, prediction and applications." kostenfrei, 2010. https://mediatum2.ub.tum.de/node?id=820985.

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5

Nilsson, Jonas. "Cooperative reactive sites in designed helix-loop-helix polypeptide catalysts /." Linköping : Univ, 2002. http://www.bibl.liu.se/liupubl/disp/disp2002/tek759s.pdf.

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6

Bloor, A. J. C. "Proteins for the basic helix-loop-helix transcription factor SCL." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596727.

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Members of the basic Helix-Loop-Helix (bHLH) family of transcription factors play critical roles in the control of development processes in species ranging from yeast to humans. The product of the SCL (Stem Cell Leukaemia) gene is a bHLH protein that was first identified by its ectopic expression in a case of childhood acute leukaemia and it has subsequently been characterised as a key player in the regulation of the development of blood and endothelium. The mechanism by which SCL functions are unclear, however it is likely that it regulates target genes by the formation of cell specific multiprotein complexes. A number of such complexes have been identified, however only in a small number of cell types. The aim of this project was to identify novel SCL partner proteins in order to better understand how it functions both normally and as an oncogene. Over 300 potential SCL interaction partners were identified in a yeast 2-hybrid screen of an embryonic cDNA library. Of these, the interaction between SCL and RFP (Ret Finger Protein) was characterised in the greatest detail. RFP is a ubiquitously expressed TRIM (Tripartite Motif) protein and little was previously known about its cellular function. RFP interacts with SCL in vitro and a stable complex of the two proteins was isolated in both COS cells and the haemopoietic progenitor cell line of 416B. RFP also interacts with a subset of other bHLH proteins via the bHLH domain but not with other classes of transcription factors and functions to repress their ability to transactivate reporter genes. The expression pattern of RFP was studied in a panel of haemopoietic cell lines. The subcellular location of RFP correlates with the lineage and development stage of the cell and also appears to be cell cycle regulated which suggests a number of novel mechanisms by which it could regulate SCL or other bHLH factors. Moreover, RFP is able to inhibit the ability of myogenic bHLH factors to convert multipotent fibroblasts into muscle indicating that its interaction with bHLH proteins is biologically significant.

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7

Imabayashi, Takeshi. "Expression of basic helix-loop-helix proteins in the glomeruli." Kyoto University, 2001. http://hdl.handle.net/2433/150563.

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8

Saarikettu, Juha. "Calcium regulation and functions of basic Helix-Loop-Helix transcription factors." Doctoral thesis, Umeå : Department of Molecular Biology, Umeå University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-537.

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9

King, Gavin W. "Investigating helix-helix interactions in the transmembrane domains of membrane proteins." Thesis, University of Warwick, 2009. http://wrap.warwick.ac.uk/3157/.

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Helix-helix interactions between membrane-spanning transmembrane (TM) domains have been shown to drive the assembly of α-helical membrane proteins within biological membranes. However, the rules that determine these interactions are not yet fully understood, despite such interactions being found in an increasing number of proteins. Recent work has implicated TM domain interactions in the formation of the protein complex Ii-MHC, formed from the association of Major Histocompatibility Complex Class II (MHC) and the MHC-associated-Invariant Chain (Ii) proteins. Following biosynthesis, three MHC α/βheterodimers bind to the Ii homotrimer to form a nonameric Ii-MHC complex within the endoplasmic reticulum. This is a critical step in the export of MHC molecules to the antigen presentation system and hence the activation of an immune response to a pathogen. In this study we have explored the TM domain interactions within the Ii-MHC complex. Results from in vivo and in vitro experiments revealed the TM domains of the α- and β-chains of MHC have a propensity to self-associate into homo-dimers and to associate with one another to form hetero-dimers. Highly conserved GxxxG motifs (known to drive dimerization) were implicated in these interactions. The TM domain of Ii was confirmed to self-associate to form trimers by in vivo and in vitro methods, but surprisingly also displayed additional oligomeric states suggesting the interaction is not as specific as was previously thought. Furthermore, we show that in vivo, the TM domain of Ii can associate with those of the α- and β-chains of MHC, whilst in vitro methods suggested Ii preferentially binds to α-chains. Collectively, these findings strongly suggest that the TM domains of Ii and MHC have a role to play in the assembly of the Ii-MHC complex, and hence the very important process of antigen presentation. Additionally, in this study we have undertaken development of NMR spectroscopy methods that have the potential to increase our understanding of not only the Ii-MHC complex, but protein-protein interactions in general.

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10

Ma, Philip Chun-Ming. "Structural studies on the basic-helix-loop-helix region from MyoD." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28070.

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11

Massari, Mark Eben. "Transcriptional regulatory properties of the class I helix-loop-helix proteins /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9814549.

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12

Gutmann, Anja Franziska [Verfasser], and Ralph [Akademischer Betreuer] Wäsch. "Identifikation neuer Zielgene der Helix-Loop-Helix-Proteine der ID-Familie." Freiburg : Universität, 2011. http://d-nb.info/1123457867/34.

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13

Yang, Jing. "Investigation of the role of Id Helix-loop-helix proteins in neurogenesis." Thesis, University of Essex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517299.

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14

Dai, Nan. "I. Collagen-like polypeptides. II. Helix-turn-helix peptides and turn mimetics." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28411.

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Collagen is one of the most important and abundant proteins in mammals. It consists of three left-handed PPII helixes coiled along a common axis to form a very compact right-handed super helix. The primary structure is shown to be (Gly-Xaa-Yaa)n repeats with high content of prolyl residues at both Xaa and Yaa positions. Cis-trans isomerization of the prolyl amide bonds is one of the rate-limiting steps during collagen triple helix folding. The conformationally locked alkene isosteres Fmoc-Gly-Ψ[(E)CH=C]-Pro-Hyp(tBu)-OH and Fmoc-Pro-Ψ[(E)CH=C]-Pro-OH were designed and synthesized. The synthesis of the Gly-Pro isostere had no stereo-control, and the two diastereomers of the tripeptide isostere Fmoc-Gly-Ψ[(E)CH=C]-Pro-Hyp(tBu)-OBn were separated by normal phase HPLC. Although the stereoselectivity of the asymmetric reduction was not good for the Pro-Pro isostere, the resulting diastereomers was separable by flash chromatography, and the absolute stereochemistry of the two diastereomers was determined by Mosher's method. The Gly-Pro alkenyl peptides, and their control peptide Ac-(Gly-Pro-Hyp)8-Gly-Gly-Tyr-NH2 were synthesized and purified. All three peptides showed a maximum around 225 nm and a minimum close to 200 nm in the CD spectra, which indicated the formation of PPII helixes. The Tm value of the control peptide was determined to be 50.0 °C. The peptide with Gly-Ψ[(E)CH=C]-L-Pro-Hyp as the guest triplet formed a stable triple helix with a Tm value of 28.3 °C. The peptide with Gly-Ψ[(E)CH=C]-D-Pro-Hyp as the guest triplet showed a linear decrease in the ellipticity with increasing temperature, which indicated that no triple helix was formed. The Pro-Pro alkenyl peptide and its control peptide H-(Pro-Pro-Gly)₁₀-OH were synthesized and purified. The T_m value of control peptide was determined to be 31.6 °C by extrapolation to 0 M TMAO in PBS buffer, which was very close to the measured value of 31.5 °C. The Pro-Pro alkenyl peptide began to show a maximum around 225 nm in the CD spectra when the concentration of TMAO was higher than 2.5 M. After extrapolation to 0 M TMAO, the T_m value was determined to be –22.0 °C. These results indicate that the backbone inter-chain hydrogen bond is one of the major forces in stabilizing the collagen triple helix, while cis-trans isomerization has limited contribution. The intrinsic properties of the amide bond may have huge influence on the stability of the collagen triple helix. The helix-turn-helix motif is an important tertiary structure in DNA-binding proteins. Stepwise modifications of the Antennapedia HTH peptide (27-55) were performed to improve the helicity and stability. The peptide with more side-chain ion-pairs was over 4 times more helical than the native Antp peptide, while the Ala-based peptide was over 9 times more helical than the native peptide. A 12-membered ring, Fmoc-protected HTH-turn mimic was designed and synthesized, and was ready for solid phase peptide synthesis. The solubility of the cyclic peptide was very poor, and the purification of the final product was very difficult. The solubility problem might also affect solid phase peptide synthesis in the future.
Ph. D.

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15

Sato, Tetsu. "The Basic Helix-Loop-Helix Gene hesr2 promotes gliogenesis in mouse retina." Kyoto University, 2004. http://hdl.handle.net/2433/148268.

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16

Schramm, Manuel. "Doppelhelix und triple helix." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-139021.

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17

Johnson, Benjamin C. F. (Benjamin Cedar Fruehauf). "Bio-inspired swimming helix." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77023.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 59-60).
This thesis investigated a bio-inspired swimming chain (BISH), inspired by Weelia cylindrica. After developing a model, it was used to investigate conditions under which helical motion would emerge. The properties of this chain as the number of nodes changes was also investigated, to see if the helical motion or other properties of its motion were emergent behaviors. Other modes of motion were also observed. Optimization of the angle of propulsion of each was performed, and other optimizations attempted, although practical difficulties prevented useful results. A ten node chain was constructed to empirically verify the helical mode of motion.
by Benjamin C. F. Johnson.
M.Eng.

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18

Hayward, Penelope Caroline. "The basic helix-loop-helix protein SCL and its role in haematopoietic development." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603895.

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The SCL gene encodes a basic helix-loop-helix protein that has a critical role in the normal development of all haematopoietic lineages, as well as an oncogenic role in T cell leukaemogenesis. SCL is suspected to function as a tissue specific transcription factor, but the mechanisms by which SCL mediates its functions are unclear. Identification and characterisation of protein-protein interactions SCL should begin to unravel the roles of this protein. As SCL is expressed in committed erythroid, mast and megakaryocytic cells as well as early haematopoietic progenitor cells, yeast-two-hybrid screens of haematopoietic cell line cDNA libraries were conducted to identify potential SCL interaction partner proteins. cDNA libraries were generated from an early haematopoietic progenitor cell line and a megakaryocytic cell line. These screens using both these libraries and a mouse E10.5 embryo cDNA library identified a range of potential interaction partners for the SCL protein. PolyA⁺ RNA was isolated from a wide range of haematopoietic cell lines, and embryonic tissues and Northern blot analysis was then used to investigate the expression patterns of these potential interaction partners. The combination of this expression data and data gathered from sequence analysis using bioinformatics programs was used to assess which of the proteins identified was the most promising candidate SCL interaction partner. The association between SCL and the IFNα inducible protein IFI60 was investigated.

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19

Hufnagel, Robert B. "The Role of Basic Helix-Loop-Helix Transcription Factors in Early Retinal Neurogenesis." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282932913.

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20

Van, Osselaer Christian. "Différenciation morphométrique et génétique de Helix pomatia L. 1758 et Helix lucorum L. 1758." Doctoral thesis, Universite Libre de Bruxelles, 2001. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211571.

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21

Bloor, Adrian John Clifton. "Identification of novel partner proteins for the basic helix-loop-helix transcription factor SCL." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619716.

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22

Zhang, Fan. "Cloning and characterization of genes encoding basic helix loop helix (bHLH) proteins in Arabidopsis /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992950.

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23

Antonsson, Camilla. "Inducible and constitutive modes of gene regulation by the dioxin receptor and Arnt /." Stockholm, 1999. http://diss.kib.ki.se/1999/91-628-3438-X/.

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24

Braun, Marvin Herbert. "Anoxic survival in Helix aspersa." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596873.

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The pulmonate snail, Helix aspersa, has the ability to survive long bouts of anoxia by depressing its metabolism. Direct calorimetry was used to measure the metabolic heat production of the snails in this state. During 24-48 hrs of anoxia, heat production varied with the oxygen levels and fell as low as 2% of that during normoxia. The Helix central nervosa system also depressed its metabolism during anoxia. Electrophysiological recordings revealed decreases in both action potential firing (spike arrest) and membrane conductance (channel arrest). These processes allow the maintenance of ionic gradients during a period when ion pumping has presumably been down-regulated to conserve ATP. These abilities to respond to anoxia were found in both whole brains and isolated neurons. The mitochondrial inhibitor antimycin resulted in responses very similar to those seen in anoxia. This may be due to the fact that mitochondrial blockade with antimycin results in an increased production of reactive oxygen species, intracellular messengers which have been implicated in the anoxia responses of several cell types. The similar responses of anoxia and antimycin suggest that a high concentration of oxygen radicals triggers entry into metabolic depression. Support for this hypothesis came from neurons incubated in ascorbate (an antioxidant). With the amount of reactive oxygen species diminished, these neurons no longer responded to an anoxic challenge, evidence for the importance of reactive oxygen species in the anoxia response of snails. During anoxia, intracellular calcium levels are protected by an upregulated Ca²⁺ pump, resulting in the rapid clearance of any calcium transients and a decreased basal calcium level. These experiments have revealed the potential for the snail to become a model organism in the study of oxygen sensing and metabolic depression.

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25

Cardew, Antonia. "Specificity of triple helix formation." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/183845/.

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Triplex-forming oligonucleotides (TFOs) have been the subject of extensive research in recent years. They have potential applications in many areas; such as gene-based therapies, site-directed mutation and as biochemical tools. However, triplex technology has been hampered by several problems, including low stability due to electrostatic repulsion between strands. This thesis has investigated combinations of four methods for stabilising triplex DNA; these include incorporation of the positively charged thymine analogues bis-amino-U and propargylamino-dU in TFOs. Also modified TFO’s containing anthraquinone derivatives have been tested. Further, the free-intercalating agent naphthylquinoline has been used to modulate TFO binding. A TFO containing six consecutive BAU molecules has previously been shown to interact with non-target sites. The pH dependence of this TFO was investigated. These experiments showed that considerably higher TFO concentrations were needed to generate a footprint as the pH was increased. The TFO had a high affinity for the exact template (tyrT) at pH 5.0 and 6.0 and showed some evidence of binding even at 30 μM at pH 7.0. These gels also showed evidence of the secondary binding seen in previous studies; this was considerably more evident at pH 5.0, however, suggesting that the secondary binding may be more sensitive to pH than the primary binding. Secondary binding sites for TFOs were examined by ‘Restriction Endonuclease Protection, Selection and Amplification’ or REPSA. REPSA has been used to select for DNA templates that are bound by the 9mer TFO containing six bis-amino-U residues. Fourteen of the sequences which emerged from REPSA were chosen for footprinting with TFOs containing BAU, propargylaminodU or T. The BAU-TFO produced clear footprints on all but one of the REPSA templates tested, indicating that the REPSA process was successful in selecting for sequences which are bound by the TFO. Significantly higher concentrations of the P-TFO were required, and magnesium chloride and / or the triplex binding ligand naphthylquinoline were needed to promote binding. Despite the differences in template sequence there does not appear to be a strong pattern in the binding intensities of the TFOs on the different templates. However, all templates do contain a run of four to eight A’s. Surprisingly it appears from these data that the BAU TFO discriminates better than the P-TFO against non-exact binding sites The selectivity of TFOs containing anthraquinone modifications was also investigated. Anthraquinone intercalates between DNA bases in duplex DNA and can be tethered to the end of a TFO to increase stability. The specificity of five TFOs with different anthraquinone modifications was examined by footprinting against fragments containing mismatches. A doubly modified TFO bound with the highest affinity and was most tolerant of mismatches. Mismatches at the centre of the template had a lesser effect on binding affinity than mismatches at the 3’ end. The effect of a 3’ mismatch was also greater if the anthraquinone was at this end. The presence of an S-base at the 3’ end allowing intercalation of the anthraquinone at a YpR step increased the binding affinity on the exact template in comparison to TFO 3 which did not contain the S-base. The TFO containing the S base did not bind quite as well as the doubly modified TFO however.

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26

Jhas, Sumitpal. "Regulation of cortical neuron and astrocyte differentiation by the basic helix loop helix protein Hes6." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18671.

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During development of the mammalian cerebral cortex, pluripotent neural progenitor cells located in the ventricular zone lining the lateral ventricles give rise to neurons, astrocytes, and oligodendrocytes. Neurogenesis precedes astrocyte differentiation, followed by oligodendrocyte differentiation. The mechanisms regulating the transition of undifferentiated progenitor cells into the differentiated state are regulated in part by basic-helix-loop-helix (bHLH) transcription factors of the Hairy/Enhancer of split (Hes) family. A number of Hes proteins are induced in response to the activation of the Notch signaling pathway. Notch-activated Hes proteins, like Hes1 or Hes5, are transcriptional repressors that inhibit cortical neurogenesis and promote astrocyte differentiation. Another Hes family member, termed Hes6, is not activated in response to Notch signaling and promotes neurogenesis, in contrast to Notch-activated Hes1 and Hes5. The objectives of the present studies were a) to elucidate the molecular mechanisms underlying the pro-neuronal activity of Hes6, and b) to determine whether or not Hes6 is also involved in glial cell differentiation. To pursue these goals, a structure function analysis was performed in which mutated forms of Hes6 were examined for their ability to promote neurogenesis using primary cultures of cortical neural progenitor cells. Moreover, Hes6 and mutated forms thereof were tested to determine whether they would inhibit astrocyte differentiation. It is shown here that Hes6 inhibits astrogenesis in addition to inducing neuronal differentiation. These two activities require separate structural domains, suggesting that that they are mediated by different molecular mechanisms.
Durant le développement du cortex cérébral mammifère, des cellules souches neuronales situées dans la zone ventriculaire se différencient en neurones, astrocites, et oligodendrocites. Durant ce développement la neurogenèse prend place en premier, suivi par la différenciation des astrocites et celle des oligodendrocites. Les mécanismes régulateurs de la différenciation sont en parti sous le control des facteurs de transcriptions « basic-helix-loop-helix » (bHLH) appartenant au groupe « Hairy/Enhancer of split » (Hes). Plusieures protéines Hes sont activées par la signalisation de Notch. Ces protéines, tel Hes1 et Hes5, sont des inhibiteurs de transcription durant la neurogenèse corticale et promeuvent la différentiation des astrocites. Par contre Hes6, insensible aux signaux de Notch, promeut la neurogenèse. Les objectifs de cette étude consistent à: 1) mieux comprendre les mécanismes moléculaires de l'activité de Hes6 ; 2) étudier le rôle potentiel de Hes6 dans la différenciation des cellules glies. Nous avons analysé l'habileté de différents mutants de Hes6 à promouvoir la neurogenèse en employant un système de culture cellulaire primaire de cellules souches neuronales. De plus, ces différentes formes de Hes6 ont été testées pour leur effet sur l'inhibition de la différenciation des astrocites. Nous démontrons que Hes6 inhibe l'astrogenèse et promeut la différenciation neuronale. Ces deux activités requèrent différentes domaines structurelles, laissant présager différents mécanismes moléculaires.

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Lara-Ramirez, Ricardo. "Lamprey neural Helix-Loop-Helix (HLH) genes and the evolution of the vertebrate nervous system." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:107e31ad-9183-4b07-842b-d01e27a4c9e6.

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Transcription factors of the helix-loop-helix (HLH) gene family are widespread in the animal kingdom. Among them, members of HLH subfamilies such as ASCL, Neurogenin, NeuroD, COE, Atonal, Oligo, NSCL, Hairy/E(spl) and Hey (here referred to as neural HLH genes) have been shown to be fundamental for the development of the nervous system. They are expressed at different time periods of neuronal differentiation, from the specification of ectoderm towards a neural lineage, to the ultimate differentiation of neurons. Few HLH genes have been identified in the lamprey; however, considering the wide diversity of HLH gene subfamilies in metazoans, including vertebrates, it is very likely that lampreys possess a large repertoire of HLH genes in their genome. In the present study, the identification of several HLH genes in the lamprey genome, as well as the isolation and expression of different lamprey neural HLH genes is reported. As expected, a wide repertoire of HLH genes was identified in the sea lamprey (Petromyzon marinus) genome. On the other hand, the identification and expression analysis of different neural HLH genes of the ASCL, Neurogenin, COE and Hairy/E(spl) in the brook lamprey Lampetra planeri showed an overall conservation with other vertebrates, both at the sequence and expression pattern levels. In addition, novel features of the lamprey nervous system are revealed, such as the identification of possible new sensory cranial placodes in pharyngeal arches. Furthermore, these genes can serve as molecular markers for different cranial placodes and dorsal root ganglia (DRG), and their expression also highlights the presence of a ventricular zone in the brain and spinal cord, along with a complementary marginal zone. Finally, with the use of a Notch pathway inhibitor in developing L. planeri embryos, the regulation of expression of the isolated genes by the Notch signaling pathway was shown to be generally conserved between lampreys and gnathostomes in the spinal cord. This functional study also revealed that the lamprey spinal cord likely presents an independent developmental programme from the brain. All together, the present study shows that the analysis of neural HLH genes represents an excellent tool to understand the lamprey nervous system.

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28

Narumi, Osamu. "OUT, a Novel Basic Helix-Loop-Helix Transcription Factor with an Id-like Inhibitory Activity." Kyoto University, 2000. http://hdl.handle.net/2433/180866.

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29

Walter, Monika. "Die parallele [beta]-Helix [Beta-Helix] der Pektat-Lyase aus Bacillus subtilis Stabilität, Faltungsmechanismus und Faltungsmutanten /." [S.l. : s.n.], 2002. http://pub.ub.uni-potsdam.de/2002/0027/walter.pdf.

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30

Yeung, Sze-chun, and 楊思俊. "Expression of regulatory Helix-loop-helix factor Id2 protein in the developing and adult mouse retina." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29976649.

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31

Rivera, Richard Ramon. "The dominant negative helix-loop-helix proteins Id2 and Id3 are essential for proper lymphocyte development /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9907777.

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32

Olofsson, Susanne. "Design, synthesis, structure, and dynamics of a polypeptide with supersecondary structure a helix-loop-helix dimer /." Göteborg : Dept. of Organic Chemistry, University of Göteborg, 1994. http://books.google.com/books?id=6AdrAAAAMAAJ.

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33

McGee, Christopher J. "DNA helix imperfections Structure and flexibility /." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2006. http://proquest.umi.com/login?COPT=REJTPTU0NWQmSU5UPTAmVkVSPTI=&clientId=3739.

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34

Janahmadi, Mahyar. "Ionic currents in Helix aspersa neurones." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318259.

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35

Ungless, M. A. "Conditioning in the snail, Helix aspersa." Thesis, University of York, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242162.

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36

Washbrook, Elinor. "Alternate strand DNA triple helix formation." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242223.

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37

Azzarito, Valeria. "Versatile oligoamide α-helix mimetic scaffolds." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/6888/.

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Protein-protein interactions (PPIs) play a pivotal role in mediating a number of biological processes involved in the development of infected or diseased states. Since α-helices constitute the most abundant motif at characterised protein interfaces, α-helix mediated PPIs represent an attractive target for therapeutic intervention and their inhibition with α-helix mimetics has emerged as a powerful strategy. Encouraging results have been obtained through the design of foldamers and proteomimetics and the current state-of-the-art is described in Chapter 1. The Wilson group is interested in the development of aromatic oligoamide α-helix mimetics. The work presented in this thesis was therefore aimed at developing a better understanding of the conformational properties of this family of proteomimetics through screening against two key oncogenic targets, p53/hDM2 and Mcl-1/NOXA B, in order to identify key features required to reproduce the functional role of α-helices and achieve effective inhibition. A 2-O-alkylated oligobenzamide scaffold was designed to determine the effect of non-covalent interactions on the conformational preference and molecular recognition properties of these oligomers. The conformational studies performed on regioisomeric 2-O and 3-O-alkylated dimers are described in Chapter 2, whilst the biophysical assessment of trimers of both series for p53/hDM2 inhibition is reported in Chapter 3. These studies pointed to a complex interplay of interactions influencing the conformational and protein recognition properties of these mimetics and led to design of a new hybrid -helix mimetic scaffold. Chapter 4 describes the conformational studies and structure-activity relationship data obtained from biological assays of a 35-membered library built using a robust solid-phase strategy. This scaffold allowed the identification of the first examples of enantioselective recognition of type III mimetics by different proteins and enantiodependent differentiation of mimetics by a protein partner, and represents a potential starting point to elaborate rule based approaches for the design of proteomimetics aimed at effective PPI inhibition.

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Gornall, Joanne Louise. "The helix-coil transition in gelatin." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612077.

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Jenkins, Richard Owen. "High linearity broad-band helix TWTs." Thesis, Lancaster University, 2003. http://eprints.lancs.ac.uk/76591/.

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Helix travelling-wave tubes (TWTs) are extensively employed as final power amplifiers in satellites. These applications demand low spectral noise and high efficiency across a broad band. Research has been carried out to achieve these criteria in a helix TWT design. A deeper understanding has been gained on how the basic parameters of a TWT affect its non-linear performance. By selecting and controlling the parameters that are critical to the amplifier’s nonlinear performance the designs corresponding to the important and desired conditions have been identified. The main simulation tool for modelling the interaction processes in a generic helix TWT was a large-signal model (LSM). A helix slow-wave structure is normally tapered to maintain its phase relationship with the electron beam and to maximise its output RF power. By determining the sensitivity of the helix dimensions on the nonlinear performance at different regions along the tube, a non-uniform slow-wave structure design has been developed for a more linear performance. Since the conditions of high linearity and efficiency could not be achieved simultaneously, the best trade-off was attained. The performance across the frequency band of 10.7 to 12.75GHz was computed for the uniform and tapered helix designs. With the use of a simulated multi-stage collector with optimised electrodes, the overall TWT performance was determined. Further understanding has been gained on the fundamental processes in the tube that cause the generation of nonlinear transfer curves and spectral distortion. The modelling of RF beam current and helix voltage waveforms and their characteristics provided a unique insight. In addition, the formation and deceleration of the electron beam bunches have been shown for the various important conditions; revealing the desirable physical conditions within the beam.

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Wilman, Henry R. "Computational studies of protein helix kinks." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:21225f0e-efed-49c6-af27-5d3fe78fa731.

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Kinks are functionally important structural features found in the alpha-helices of many proteins, particularly membrane proteins. Structurally, they are points at which a helix abruptly changes direction. Previous kink definition and identification methods often disagree with one another. Here I describe three novel methods to characterise kinks, which improve on existing approaches. First, Kink Finder, a computational method that consistently locates kinks and estimates the error in the kink angle. Second the B statistic, a statistically robust method for identifying kinks. Third, Alpha Helices Assessed by Humans, a crowdsourcing approach that provided a gold-standard data set on which to train and compare existing kink identification methods. In this thesis, I show that kinks are a feature of long -helices in both soluble and membrane proteins, rather than just transmembrane -helices. Characteristics of kinks in the two types of proteins are similar, with Proline being the dominant feature in both types of protein. In soluble proteins, kinked helices also have a clear structural preference in that they typically point into the solvent. I also explored the conservation of kinks in homologous proteins. I found examples of conserved and non-conserved kinks in both the helix pairs and the helix families. Helix pairs with non-conserved kinks generally have less similar sequences than helix pairs with conserved kinks. I identified helix families that show highly conserved kinks, and families that contain non-conserved kinks, suggesting that some kinks may be flexible points in protein structures.

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White, Barbara Anne Lindsay Carleton University Dissertation Sociology and Anthropology. "Bioculturalism revisited, the neurognostic helix uncoiled." Ottawa, 1995.

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42

Kwok, Wai-kei. "Oncogenic function of TWIST in the development and progression of prostate cancer." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B3893825X.

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Therien, James Patrick Daniel. "The Role of Transmembrane Domain Helix-Helix Interactions in the Function of Pentameric Ligand-Gated Ion Channels." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35643.

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The pentameric ligand gated ion channel super family plays a central role in fast synaptic communication between neurons and at the neuromuscular junction. Extensive studies on the prototypic pLGIC, the Torpedo nicotinic acetylcholine receptor (nAChR) have revealed an exquisite lipid sensitivity, with the nAChR adopting a novel uncoupled conformation in membranes lacking activating anionic and neutral lipids. The lipid-exposed transmembrane alpha-helix, M4, in each homologous subunit likely acts as a lipid sensor. One model proposes that activating lipids promote M4 “binding” to the adjacent alpha-helices, M1 and M3, to enhance interactions between the M4 C-terminus and the Cys-loop of the agonist-binding domain, with such interactions promoting coupling between the agonist site and channel gate. The first part of my thesis indirectly tests this hypothesis by exploring the effects of membrane hydrophobic thickness on nAChR function. Specifically, I tested the hypothesis that thicker membranes, which should promote alignment of M4 parallel to M1/M3 and thus helix-helix interactions, favor a coupled conformation. Although I found that the nAChR is uncoupled in all membranes tested, regardless of hydrophobic thickness, thicker membranes promote transitions from uncoupled to ultimately the desensitized state over the minutes to hours time frame. In contrast to anionic lipids, which influence function primarily via a conformational selection mechanism, membrane hydrophobic thickness influences function via a kinetic mechanism - thick membranes lower the activation energy between uncoupled and coupled conformations to promote conformational transitions. In the second part of my thesis, I used the two prokaryotic homologs, GLIC and ELIC, to explore how amino acid interactions at the interface between M4 and M1/M3 influence channel activity. Alanine scanning mutagenesis of this interface shows that disruption of almost any interaction in GLIC leads to a loss of folding and/or function, while analogous mutations in ELIC typically lead to no change or produce gains in function. Sequence comparisons with other members of the pLGIC superfamily suggest that the transmembrane domains of GLIC and ELIC represent two distinct archetypes. Each archetype may strike a different balance between the need for strong M4 binding to M1/M3 to promote folding and pentamer assembly, and the need for weaker interactions that allow for greater conformational flexibility during function.

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Wright, Lilyan Yi Tian. "The activity of the helix-loop-helix protein, E47, is regulated by the PI3K/Akt signaling pathway." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3258711.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed June 4, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

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Altwaijry, N. A. S. "A novel coarse-grained molecular dynamics method for the accurate prediction of helix-helix interactions in GPCRs." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10044556/.

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This thesis describes a novel computational method developed to identify and characterise points of protein-protein interaction between two G protein-coupled receptors (GPCRs). An ensemble-based coarse-grained molecular dynamics (eCG-MD) approach was applied to GPCR oligomers with experimentally-determined contact interfaces (adenosine A2A receptor, rhodopsin, CXCR4 and β1AR). Error analysis was used to determine 1) the number of replicas in an ensemble and 2) the simulation time for each replica that were needed to obtain convergence with experimental results. Error analysis also enabled identification of non-interacting regions. This novel method yielded calculations of distance between rhodopsin, CXCR4 and β1AR transmembrane domains reported to form contact points in homodimers that correlated well with the corresponding measurements obtained from the structural data, demonstrating an ability to predict contact interfaces computationally. The method gave distance measurements between residues shown to be involved in oligomerisation of the fifth transmembrane domain from the adenosine A2A receptor that were in very good agreement with the existing biophysical data. Further, the method provided information about the nature of the contact interface that could not be determined experimentally. This CG-MD method was then used as a high-throughput screen to identify novel sites of interaction in the adenosine A2A receptor, informing the design of future experimental work. Experimental methods to investigate interactions are also described in this thesis. These were less successful in identifying contact points, however, the present computational method will enable novel interaction points between GPCRs to be predicted and tested experimentally using assays of ligand binding and receptor signaling. In conclusion, this work provides an accurate, reproducible and reliable method for determining the specific points of interaction between GPCR dimers. The eCG-MD method discriminates between residues in TM helices that form specific interactions and residues that are in close proximity but do not interact.

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46

Hörzer, Jan Ruben. "Glycosylierte beta-Peptide als Oligosaccharidmimetika." [S.l. : s.n.], 2007.

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47

Liu, Tao. "Part 1 Synthesis of a potent histone deacetylase inhibitor; Part 2 Studies towards a stabilized helix-turn-helix peptide." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/26019.

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The first part of this work describes the synthesis of a new histone deacetylase (HDAC) inhibitor (HDI). HDAC enzymes modify core histones, influence nucleosome structure and change gene transcription by removing the acetyl groups from lysine residues on proteins. HDIs are showing exciting potential as a new class of drugs for cancer and a variety of other diseases. A new HDAC inhibitor based on the hydroxamic acid motif has been synthesized. Two characteristic structural features were incorporated into the design of the novel inhibitor. A cyclic peptide mimetic of known structure was fused to a hydroxamic acid moiety through an aliphatic chain. The HDAC inhibitor provided significant inhibitory activity against HDACs with an IC50 value of 46 Â± 15 nM, and against HDAC8 with an IC50 value of 208 Â± 20 nM. The potent HDAC inhibitory activity of the HDAC inhibitor demonstrates the importance of the rim recognition region in the design of HDIs. The hydrophobic cyclic turn mimic allows the formation of a tight complex between HDI and HDAC enzymes. The second part of this work is to synthesize secondary structure mimics and incorporate them into the helix-turn-helix (HTH) motif. One of the important methods to study the conformation of the biologically active peptides is to incorporate the rigid peptidomimetics into the relevant peptides. Important information can be obtained from the study of conformationally constrained peptides. HTH proteins are well characterized and found in many organisms from prokaryotes to eukaryotes. The relatively small size, simple structure, and significance in stabilizing tertiary structures make the HTH peptide an attractive target to mimic. Both a Gly HTH turn mimic and a Ser HTH turn mimic were synthesized using stereoselective hydrogenation and macrocyclization starting from unnatural amino acids in a yield of 33% and 14%, respectively. The synthesis of Fmoc protected HTH turn mimics allowed incorporation into HTH peptides using Fmoc chemistry on solid phase. The incorporation of the HTH turn mimics into the peptides proved to be challenging, either by sequential elongation or by segment condensation. Alternative peptide synthesis strategies were employed in attempts to solve the problems.
Ph. D.

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MacAlister, Cora Ann. "The role of the basic helix loop helix transcription factor speechless in the initiation of the stomatal lineage /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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Qureshi, Tabussom. "Studying Transmembrane Helix Interactions in SDS micelles." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34417.

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The importance of interactions between transmembrane domains of integral membrane proteins has been well-established in a range of essential cellular functions. Most integral membrane proteins also possess regions that lie on the exterior of the membrane that may influence the ability of these transmembrane domains to interact. We sought to test this hypothesis by quantifying the energetics of transmembrane helix self-association in the absence and presence of an amphipathic helix that can bind to the membrane surface. The model chosen for this study was the major coat protein (MCP) of M13 bacteriophage, which has an N-terminal amphipathic helix linked to its single transmembrane segment via a flexible linker. Dimerization of both full-length MCP and a peptide containing only the transmembrane domain (MCPTM) was studied by solution NMR in SDS micelles. We found that there was an increase in the apparent dimerization affinity in the absence of the N-terminal helix. However, this increase in apparent affinity could be attributed to differences in detergent-binding properties of the two polypeptides in monomeric versus dimeric states when the empty micelle was considered to be a participant in the dimer dissociation. Preliminary results from the integral membrane protein, p7 of the hepatitis C virus are also presented in this thesis. It has been demonstrated that p7 enhances viral infectivity and accumulation, and that this function may require oligomerization in the membrane. While we encountered limitations due to challenges in the generation of sufficient quantities of pure p7 samples, we were able to perform circular dichroism spectroscopy under conditions that may favor different oligomeric states. These studies suggest that there is a change in the degree of helicity upon oligomerization, and suggest that SDS could be a suitable system to characterize the interactions of the p7 oligomer in the future.

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Mansor, Mohd Fais Bin. "MIMO application for the quadrifilar helix antenna." Thesis, University of Surrey, 2012. http://epubs.surrey.ac.uk/770238/.

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Capacity increase of the current land mobile satellite (LMS) communication systems is highly desirable to cater for more data-centric applications such as broadcasting. Since the Multiple-input Multiple-output (MIMO) offers high spectral efficiency without additional bandwidth and transmit power, its implementation in the LMS system has been widely investigated in terms of channel characterisation, channel modelling and coding algorithms. However, the aspect of receive antenna design and its performance evaluation has not yet been considered even though it has enormous impacts on the system performance. This thesis presents a study on designing a novel dual circularly polarised receive antenna system for the LMS MIMO system that utilises the printed quadrifilar helix antenna (PQHA) and also the required performance evaluation methods. The PQHA was miniaturised using two new methods, which are the element folding and combination of element folding and meandering where more than 50% size reduction can be achieved. These miniaturised PQHAs were combined to create a variety of dual circularly polarised arrays such as the dual circularly polarised single folded PQHA (SFPQHA) horizontal array and folded meandered PQHA (FMPQHA) vertical array. For evaluating the branch power ratio of these arrays, a newly derived formulation of the mean effective gain (MEG) in a Ricean fading channel that incorporates the polarisation of the line-of-sight (LoS) component and the corresponding antenna gain has been proposed. Further evaluation of these arrays as the receive antenna in this system was carried out using measurement campaigns. Results show that both arrays provide substantial capacity increase when compared to a single link system in both LoS and NLoS channels. A more comprehensive study on the effect of antenna properties was conducted using a newly, developed channel model that integrates the array characteristics with the propagation channel. This modelling approach allows for a performance comparison between the designed SFPQHA array and other antennas to be easily implemented, which is very useful in the process of designing MIMO antennas.

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Dissertations / Theses on the topic 'Helix'

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