Littérature scientifique sur le sujet « I-Motifs »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les listes thématiques d’articles de revues, de livres, de thèses, de rapports de conférences et d’autres sources académiques sur le sujet « I-Motifs ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Articles de revues sur le sujet "I-Motifs"
1
Shamim, Amen, Maria Razzaq et Kyeong Kyu Kim. « MD-TSPC4 : Computational Method for Predicting the Thermal Stability of I-Motif ». International Journal of Molecular Sciences 22, no 1 (23 décembre 2020) : 61. http://dx.doi.org/10.3390/ijms22010061.
Texte intégralRésumé :
I-Motif is a tetrameric cytosine-rich DNA structure with hemi-protonated cytosine: cytosine base pairs. Recent evidence showed that i-motif structures in human cells play regulatory roles in the genome. Therefore, characterization of novel i-motifs and investigation of their functional implication are urgently needed for comprehensive understanding of their roles in gene regulation. However, considering the complications of experimental investigation of i-motifs and the large number of putative i-motifs in the genome, development of an in silico tool for the characterization of i-motifs in the high throughput scale is necessary. We developed a novel computation method, MD-TSPC4, to predict the thermal stability of i-motifs based on molecular modeling and molecular dynamic simulation. By assuming that the flexibility of loops in i-motifs correlated with thermal stability within certain temperature ranges, we evaluated the correlation between the root mean square deviations (RMSDs) of model structures and the thermal stability as the experimentally obtained melting temperature (Tm). Based on this correlation, we propose an equation for Tm prediction from RMSD. We expect this method can be useful for estimating the overall structure and stability of putative i-motifs in the genome, which can be a starting point of further structural and functional studies of i-motifs.
2
Jiang, Guimei, Lijun Xu, Kewei Wang, Xing Chen, Jine Wang, Weiguo Cao et Renjun Pei. « Quinaldine red as a fluorescent light-up probe for i-motif structures ». Analytical Methods 9, no 10 (2017) : 1585–88. http://dx.doi.org/10.1039/c7ay00301c.
Texte intégralRésumé :
We report a new fluorescent probe for i-motif structures. When binding to i-motifs, quinaldine red exhibits a remarkable increase in its fluorescence, which benefits i-motif-involved label-free systems.
3
Ruggiero, Emanuela, Sara Lago, Primož Šket, Matteo Nadai, Ilaria Frasson, Janez Plavec et Sara N. Richter. « A dynamic i-motif with a duplex stem-loop in the long terminal repeat promoter of the HIV-1 proviral genome modulates viral transcription ». Nucleic Acids Research 47, no 21 (29 octobre 2019) : 11057–68. http://dx.doi.org/10.1093/nar/gkz937.
Texte intégralRésumé :
Abstract I-motifs are non-canonical nucleic acids structures characterized by intercalated H-bonds between hemi-protonated cytosines. Evidence on the involvement of i-motif structures in the regulation of cellular processes in human cells has been consistently growing in the recent years. However, i-motifs within non-human genomes have never been investigated. Here, we report the characterization of i-motifs within the long terminal repeat (LTR) promoter of the HIV-1 proviral genome. Biophysical and biochemical analysis revealed formation of a predominant i-motif with an unprecedented loop composition. One-dimensional nuclear magnetic resonance investigation demonstrated formation of three G-C H-bonds in the long loop, which likely improve the structure overall stability. Pull-down experiments combined with mass spectrometry and protein crosslinking analysis showed that the LTR i-motif is recognized by the cellular protein hnRNP K, which induced folding at physiological conditions. In addition, hnRNP K silencing resulted in an increased LTR promoter activity, confirming the ability of the protein to stabilize the i-motif-forming sequence, which in turn regulates the LTR-mediated HIV-1 transcription. These findings provide new insights into the complexity of the HIV-1 virus and lay the basis for innovative antiviral drug design, based on the possibility to selectively recognize and target the HIV-1 LTR i-motif.
4
Martins, Alexandra, Christian H. Gross et Stewart Shuman. « Mutational Analysis of Vaccinia Virus Nucleoside Triphosphate Phosphohydrolase I, a DNA-Dependent ATPase of the DExH Box Family ». Journal of Virology 73, no 2 (1 février 1999) : 1302–8. http://dx.doi.org/10.1128/jvi.73.2.1302-1308.1999.
Texte intégralRésumé :
ABSTRACT Vaccinia virus nucleoside triphosphate phosphohydrolase I (NPH-I) is a DNA-dependent ATPase that serves as a transcription termination factor during viral mRNA synthesis. NPH-I is a member of the DExH box family of nucleic acid-dependent nucleoside triphosphatases (NTPases), which is defined by the presence of several conserved sequence motifs. We have assessed the contributions of individual amino acids (underlined) in motifs I (GxGKT), II (DExHN), III (SAT), and VI (QxxGRxxR) to ATP hydrolysis by performing alanine scanning mutagenesis. Significant decrements in ATPase activity resulted from mutations at nine positions: Lys-61 and Thr-62 (motif I); Asp-141, Glu-142, His-144, and Asn-145 (motif II); and Gln-472, Arg-476, and Arg-479 (motif VI). Structure-function relationships at each of these positions were clarified by introducing conservative substitutions and by steady-state kinetic analysis of the mutant enzymes. Comparison of our findings for NPH-I with those of mutational studies of other DExH and DEAD box proteins underscores similarities as well as numerous disparities in structure-activity relationships. We conclude that the functions of the conserved amino acids of the NTPase motifs are context dependent.
5
Nufer, Oliver, Svend Guldbrandsen, Martin Degen, Felix Kappeler, Jean-Pierre Paccaud, Katsuko Tani et Hans-Peter Hauri. « Role of cytoplasmic C-terminal amino acids of membrane proteins in ER export ». Journal of Cell Science 115, no 3 (1 février 2002) : 619–28. http://dx.doi.org/10.1242/jcs.115.3.619.
Texte intégralRésumé :
Export of membrane proteins from the ER is believed to be selective and require transport signals, but the identity of such signals has remained elusive. The recycling type I membrane protein ERGIC-53 carries a C-terminal diphenylalanine motif that is required for efficient ER export. Here we show that this motif can be functionally substituted by a single phenylalanine or tyrosine at position -2, two leucines or isoleucines at position -1 and -2 or a single valine at position -1. These motifs are common among mammalian type I membrane proteins. A single C-terminal valine, but none of the other motifs,accelerates transport of inefficiently exported reporter constructs and hence operates as an export signal. The valine signal is position, but not context,dependent. All transport motifs mediate COPII binding in vitro with distinct preferences for the COPII subunits Sec23p, Sec24Bp, Sec24Cp and p125. These results suggest that cytoplasmic C-terminal amino-acid motifs, either alone or in conjunction with other transport determinants, accelerate ER export of numerous type I and probably polytopic membrane proteins by mediating interaction with COPII coat components.
6
Saha, Puja, Deepanjan Panda, Diana Müller, Arunabha Maity, Harald Schwalbe et Jyotirmayee Dash. « In situ formation of transcriptional modulators using non-canonical DNA i-motifs ». Chemical Science 11, no 8 (2020) : 2058–67. http://dx.doi.org/10.1039/d0sc00514b.
Texte intégral
7
Grote, Johanna, Beate Neumann, Hans-Georg Stammler et Norbert W. Mitzel. « Diversity of aggregation motifs in gold(i) dithiocarboxylate complexes ». Dalton Transactions 47, no 13 (2018) : 4701–6. http://dx.doi.org/10.1039/c8dt00342d.
Texte intégralRésumé :
Molecular structures and aggregation motifs of different substituted gold(i) dithiocarboxylate complexes are presented and a correlation between the substituent and the aggregation motif is discussed.
8
Grote, Johanna, Beate Neumann, Hans-Georg Stammler et Norbert W. Mitzel. « Silver(i) dithiocarboxylate complexes – clustering and aggregation ». Dalton Transactions 47, no 17 (2018) : 6036–40. http://dx.doi.org/10.1039/c8dt00279g.
Texte intégralRésumé :
Molecular structures and aggregation motifs of a series of neutral homoleptic silver(i) dithiocarboxylate are presented and a correlation between the substituent and aggregation motif as well as the differences from the (almost) analogous gold(i) complexes are discussed.
9
Yanti Pantur, Mariani Irma, et Ika Ismurdiyahwati. « Songke Fabric in Libo, Wela Kaweng and Su'i Motif from Perak Village, Manggarai Regency, East Nusa Tenggara, in Study of Visual Aesthetics of Meaning and Function ». IMAGIONARY 1, no 2 (30 avril 2023) : 76–82. http://dx.doi.org/10.51353/jim.v1i2.753.
Texte intégralRésumé :
Songke fabrics with libo, wela kaweng and su'I motifs are a type of Indonesian textile work. Songke cloth with libo, wela kaweng and su'I motifs is a textile work from Perak village, Manggarai Regency, East Nusa Tenggara. This research takes the topic of the libo, wela kaweng and su’I motifs on songke cloth in Perak village, Manggarai Regency, because these motifs are superior motifs that are often produced and a cultural heritage that has its own meaning and function. Therefore, this study aims to determine the visual aesthetic meaning and function of songke cloth in libo, wela kaweng and su'I motifs on songke cloth. The data sources in this study are the figures of songke cloth craftsmen, the village head, and cultural observers. This type of research uses descriptive qualitative with an explanation through the data obtained from data collection using the method of observation, documentation, and direct interviews. The results of this study show that the libo motif means the relationship between humans and the natural surroundings where in everyday life humans always need water to sustain life. The wela kaweng motif means a plant that can be used as medicine to heal and treat livestock wounds in ancient times and the su’I motifs means as a bridge that separates the customs between the tribes in the Silver Village. Songke fabrics with libo, wela kaweng and su'I motifs are used by the Manggarai community in attending traditional ceremonies such as engagements, weddings, penti (year-end thanks giving or every harvest) and funerals.
10
Leporcq, Clémentine, Yannick Spill, Delphine Balaramane, Christophe Toussaint, Michaël Weber et Anaïs Flore Bardet. « TFmotifView : a webserver for the visualization of transcription factor motifs in genomic regions ». Nucleic Acids Research 48, W1 (23 avril 2020) : W208—W217. http://dx.doi.org/10.1093/nar/gkaa252.
Texte intégralRésumé :
Abstract Transcription factors (TFs) regulate the expression of gene expression. The binding specificities of many TFs have been deciphered and summarized as position-weight matrices, also called TF motifs. Despite the availability of hundreds of known TF motifs in databases, it remains non-trivial to quickly query and visualize the enrichment of known TF motifs in genomic regions of interest. Towards this goal, we developed TFmotifView, a web server that allows to study the distribution of known TF motifs in genomic regions. Based on input genomic regions and selected TF motifs, TFmotifView performs an overlap of the genomic regions with TF motif occurrences identified using a dynamic P-value threshold. TFmotifView generates three different outputs: (i) an enrichment table and scatterplot calculating the significance of TF motif occurrences in genomic regions compared to control regions, (ii) a genomic view of the organisation of TF motifs in each genomic region and (iii) a metaplot summarizing the position of TF motifs relative to the center of the regions. TFmotifView will contribute to the integration of TF motif information with a wide range of genomic datasets towards the goal to better understand the regulation of gene expression by transcription factors. TFmotifView is freely available at http://bardet.u-strasbg.fr/tfmotifview/.
Thèses sur le sujet "I-Motifs"
1
Gurung, Sarah Prava. « Biophysical & ; crystallographic studies of DNA i-motifs ». Thesis, University of Reading, 2018. http://centaur.reading.ac.uk/77642/.
Texte intégralRésumé :
Intramolecular i-motifs of the form C3L3-8C3L3-8C3L3-8C3, where C3 denotes the cytosine stretch and L3-8 are “loop” regions containing any DNA base (L) including cytosine, were studied to understand the effects of loop length on i-motif stability. It contrast to the previously held notion that long-looped i-motifs are more stable, it was found that i-motif structures with short loops exhibit higher thermal stabilities and transitional pH values. The stability of long-looped i-motifs are then shown to increase with the addition of [Ru(phen)2dppz]2+ (phen = 1,10-phenanthroline, dppz = dipyrido [3,2-a:2',3'-c] phenazine); a polypyridyl complex that has a potential for photodynamic therapy. Addition of the complex enhances the stability of d(C3T838)3C3 but not that of d(C3T383)3C3, implying that loop lengths are important in defining i-motif-ligand interactions. The effects of loop base composition on the stability of i-motifs have also been presented. It is shown that when d(C3XYZ)3C3 sequences are used (where X and Z are adenine, thymine and guanine, and Y is any of the four DNA bases), pyrimidine-rich sequences form more stable i-motif structures. However, when guanine is X, only two out of 12 d(C3XYG)3C3 sequences were able to form i-motifs. Change in sequence direction also resulted in different thermal and pH stabilities; emphasising the role of loop base composition on not only the i-motif’s stability but also in its formation. X-ray crystallography was used to further understand the effects of loop bases on i-motif structures. The study focuses on four tetramolecular i-motifs; two of which were solved in the mid1990’s; (d(C4)4 and d(C3T)4 but have now been re-examined using improved experimental approaches. Two novel i-motif structures of d(C3A)4 and [d(C3A) + d(C3T)] are presented. Following the X-ray diffraction of d(C3T)4 crystals to 0.68 Å resolution (previously reported at 1.4 Å) at beamline I02 (Diamond Light Source Ltd.), a novel neutron diffraction study on the particular i-motif was conducted. Single crystal neutron diffraction was carried out at MaNDi beamline (Spallation Neutron Source) to find the distribution of the proton between the hemiprotonated cytosine+·cytosine base pairs and to understand the role that H-bonded water can play in stabilising the i-motif structure.
2
Mir, Morro Bartomeu. « Studies on the formation of i-motif structures at neutral pH. Use of cytidine analogues and importance of minor groove tetrads on mini i-motifs stabilization ». Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668126.
Texte intégralRésumé :
Given the increasing interest in i-motif structures, obtaining such structures as well as detailed structural information under physiological conditions have become hot topics in the structural biology field. In this context, the main objectives of this thesis are focused on the design and detailed characterization of several oligonucleotide sequences that may form stable i-motif structures at neutral pH. The starting point is the mini i-motif structure, extensively studied in the research group that exhibits unusual high pH and thermal stability. These are dimeric structures stabilized by the formation of two hemiprotonated C:C+ base pairs capped at both ends by minor groove G:T:G:T tetrads. With the aim of getting deeper insights in this type of structures and enhance their stability at physiological conditions, different approaches were followed.
A first strategy consisted in the incorporation of a neutral analogue of protonated cytidine (pseudoisocytidine, psC) occupying specific positions of the motif. The 3H-tautomer of psC, thanks to the extra hydrogen-bond donor, can form neutral base pairs completely isomorphic to hemiprotonated C:C+ pairs. psC was incorporated in different positions of dimeric mini i-motifs and in the telomeric sequence (HT0). The effect of the incorporation of psC depends on its position in the structure, being in most cases destabilizing. Neutral psC:C base pairs stabilize i-motifs at neutral pH, but the stabilization only occurs when psC:C base pairs are located at the ends of intercalated C:C+ stacks. Structural and stability data on the incorporation of pseudocytidine in i-motifs suggest that positively charged base pairs in the core of the structure are necessary to stabilize this non-canonical DNA structure.
A second approach focused on exploring the compatibility of i-motif structures with other reported minor groove tetrads. The effect of different minor groove tetrads in i-motifs was studied in the context of short linear and cyclic oligonucleotides, affording dimeric mini i-motifs, but also in longer sequences that may form monomeric mini i-motif structures. The results show that the mini i-motif is compatible with different type of minor groove tetrads and a stability ranking could be established: G:C:G:T ≥ G:C:G:C >> G:T:G:T, exhibiting monomeric structures enhanced stability. Interestingly, a consensus sequence was outlined based on the results obtained for the set of mini i-motif-forming sequences. The mapping of this sequence throughout the human genome by bioinformatics analysis revealed a statistical prevalence. The distribution found for these sequences is not random, being much more frequent in regulatory regions
Finally, a fluorescent cytidine analogue (1,3-diaza-2-oxophenoxazine, tCo), capable to hybridize as a cytosine and maintaining the ability to form Watson-Crick as well as hemiprotonated base pairs, was tested as an internal probe for the characterization of local environments within i-motif structures. NMR spectroscopy indicated both types of hybridization (tCo:C+ and G:tCo) are compatible with the mini i-motif structure at neutral pH. Interestingly, the fluorescence signal of tCo suffers a sever quenching when forming an hemiprotonated base pair, compared to the very little quenching that shows upon WC hybridization. Hence, tCo was successfully used as fluorescent probe for monitoring conformational transitions between different species of tCo-containing sequences. Moreover, when replacing a cytosine residue involved in a C:C+ pair, the favorable stacking between tCo and G:C base pairs from the capping minor groove assemblies provokes enhanced stability of the structure against both pH and temperature. Very remarkably, the visualization of mini i-motif structures in cellular media was accomplished by confocal fluorescence microscopy after the successful transfection of HeLa cells with tCo-containing oligonucleotides.En el marc de les estructures no canòniques dels àcids nucleics i les seves possibles implicacions biològiques, aquesta tesi te com a objectiu principal l’obtenció i caracterització estructural d’estructures i- motif que siguin estables a pH neutre. El punt de partida és l’estructura mini i-motif, un tipus de motiu que presenta una inusual elevada estabilitat front pH i temperatura. Es tracta d’una estructura dimèrica estabilitzada per la formació de dos parells hemiprotonats C:C+ que interaccionen per apilament amb dues tètrades G:T:G:T de solc menor que actuen de tapa de l’estructura. Per a aprofundir en l’estudi d’aquest tipus de motius i augmentar-ne la seva estabilitat a pH fisiològic, diferents aproximacions s’han dut a terme. En la primera aproximació, s’ha explorat la incorporació d’un anàleg neutre de citidina protonada (pseudoisocitidina, psC), capaç de formar parells neutres isomòrfics als parells hemiprotonats C:C+. Els estudis realitzats demostren que l’efecte de la psC en depèn fortament de la posició dins l’estructura. La formació de parells hemiprotonats al centre de l’estructura és fonamental i la formació de parells neutres només és tolerada pels parells terminals, produint-se en aquest cas una certa estabilització. Una segona línia de treball s’ha centrat en explorar la compatibilitat d’estructures i-motif amb altres tètrades de solc menor. S’han estudiat diferents seqüències, lineals i cícliques, que donarien lloc a estructures mini i-motif amb diferents associacions de nucleobases a les tètrades. Els estudis demostren que el mini i-motif és compatible amb diferents tètrades de solc menor i s’ha pogut establir el següent rànquing d’estabilitat G:C:G:T ≥ G:C:G:C >> G:T:G:T. Cal destacar que, la seqüència consens per aquest tipus d’estructures s’ha determinat que és prevalent al genoma humà. Finalment, s’ha incorporat un anàleg de citidina fluorescent (1,3-diaza-2-oxofenoxazina, tCo), substituint citosines en posicions especifiques de l’estructura. Els resultats demostren que tCo actua de forma eficient com a sonda local per a monitoritzar transicions conformacionals i que, en posicions específiques te un efecte força positiu en l’estabilitat tèrmica del motiu. Aquest fet ha permès utilitzat un d’aquests derivats per a visualitzar el plegament de l’estructura en medi cel·lular.
3
Boissieras, Joseph. « Étude des interactions de ligands et d'anticorps avec les i-motifs de l'ADN ». Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF080.
Texte intégralRésumé :
Les i-motifs sont des structures tétramériques d'ADN constituées de paires de bases CH+:C intercalées et qui peuvent se former dans des séquences d'ADN riches en cytosine, notamment dans les conditions légèrement acides (pH≈6,0) où certaines cytosines seront protonées. Bien qu'elles soient connues depuis plus de 30 ans, du fait de leur forte dépendance au pH ces structures ont longuement été considérées comme uniquement présentes in vitro. Plus récemment, en 2018, un anticorps iMab a été développé pour cibler les i-motifs et les études ont suggéré leur présence au niveau cellulaire. De nombreuses séquences pouvant former des i-motifs ont été identifiées dans des zones actives du génome, au niveau de télomères ou de promoteurs d'oncogènes, suggérant alors de potentiels rôles biologiques de cette structure. Afin de déterminer ces effets, des outils complémentaires à l'anticorps doivent être développés afin de pouvoir contrôler la formation et la stabilité du i-motif. Ces composés chimiques, capables de stabiliser la structure et ainsi de contrôler sa formation, sont appelés ligands. De nombreux composés ont été décrits au fil des années mais aucun composé n'a aujourd'hui été unanimement admis comme ligand de i-motif de l'ADN. Cette absence de ligand de référence s'explique notamment par les méthodes utilisées jusqu'à présent pour observer les interactions des molécules avec la structure du i-motif. En effet, les techniques employées ont été héritées des études d'autres structures d'ADN et de nombreux biais introduits par celles-ci ont été identifiés, remettant en question les effets précédemment observés. Afin d'éclaircir le sujet et de conclure sur les différents effets de composés, nous avons alors proposé une méthode d'étude spécifique aux i-motifs permettant d'évaluer les effets de ligands sur la structure. Pour cela, une méthode dite de titration potentiométrique, basée sur des études de dichroïsme circulaire à différents pH à température constante, a été développée et validée sur le i-motif. Cette technique permet d'observer sans marquage de l'ADN l'état de ce dernier à différents pH, et ainsi de détecter une stabilisation causée par un ligand. Cette méthode a ensuite été couplée à des études thermiques et les deux ont alors été utilisées pour tester différents composés issus de la littérature et observer leurs effets sur la stabilité du i-motif vis-à-vis du pH. Nos résultats montrent que parmi tous les composés testés, aucune des petites molécules testées n'est capable de stabiliser un i-motif natif. Si trois composés (TMPyP4, BRACO-19 et Mitoxantrone) ont montré un effet déstabilisant sur la structure, seul le complexe [Ru(phen)2dppz]2+ a montré une certaine capacité de stabilisation. Néanmoins, cette stabilisation n'a été observée que sur une séquence spécifique à longues boucles, suggérant que cette interaction ne se fait que par des interactions avec des boucles d'ADN. Les effets des autres composés ont également été étudiées sur ces boucles, suggérant que les effets précédemment observés dans la littérature ne résultent que d'interactions à longues boucles, non spécifiques au i-motif. Dans la seconde partie, la spécificité de l'anticorps iMab a également été testée et les résultats démontrent que cet anticorps cible des séquences d'ADN riches en cytosines et non spécifiquement le i-motif. D'autres résultats indiquent même que cet anticorps est capable de déplier le i-motif suggérant là encore que cet anticorps se lie aux séquences C-riches dépliées. Dans l'ensemble, les résultats présentés dans cette thèse ne montrent qu'aucun des composés testés n'est capable de stabiliser le i-motif en interagissant directement avec le i-motif, mettant en lumière les difficultés de cibler la structure. De plus, les résultats concernant l'anticorps remettent en question l'interprétation des foyers nucléaires observés dans d'autres études et qui représentent aujourd'hui les seules observations de i-motifs natifs au niveau cellulaireI-Motifs are tetrameric DNA structures constituted by mutually intercalated CH+:C base pairs that can form in cytosine-rich DNA sequences under slightly acidic conditions (pH ≈ 6.0) where some of cytosines are protonated. They have been known for over thirty years, but due to their strong pH dependence, these structures were long considered to exist only in vitro. Quite recently, in 2018, studies renewed interest in the i-motif suggesting its presence at the cellular level, especially due to the development of the iMab antibody, raised against i-motifs. Numerous sequences capable of forming i-motifs have been identified in active regions of the genome, such as at telomeres or oncogene promoters, suggesting potentially important biological roles for this structure. To determine these effects, tools complementary to antibodies need to be developed to control i-motif formation and stability. These chemical compounds capable of stabilizing the structure and thus controlling its formation are called ligands. Many compounds have been described over the years, but none has yet been unanimously accepted as a ligand for DNA motifs. This absence of a reference ligand is partly explained by the methods used so far to observe small-molecule interactions with the i-motif structure. Indeed, the techniques employed were inherited from studies of other DNA structures, and many biases introduced by them have been identified, calling previous observations into question. To clarify the subject and conclude on the various effects of compounds, we proposed a specific method for studying i-motifs that allows the evaluation of ligands' effects on these structures. Toward this end, a potentiometric titration method, based on circular dichroism studies at different pH, was developed and validated for the i-motif. This technique allows the observation of DNA conformation without labelling at different pH, thereby detecting stabilization caused by a ligand by measuring the transition pH between folded and unfolded DNA, in isothermal conditions. This method was then coupled with thermal studies, and both were used to test different compounds previously described in the literature and observe their effects on the i-motif's stability in relation to pH. The results show that among all the tested compounds, none were capable of stabilizing native i-motifs. While three compounds (TMPyP4, BRACO-19, and Mitoxantrone) did indeed show a destabilizing effect on the structure, only the complex [Ru(phen)2dppz]2+ demonstrated some stabilizing capacity. However, this stabilization was only observed with a specific sequence with long loops, suggesting that this interaction occurs through interactions with DNA loops. The effects of other compounds on these loops were also studied, suggesting that the effects previously observed in the literature resulted from secondary, non-specific interactions with the i-motif loops. In the second part of this thesis, the selectivity of the iMab antibody was also assessed, and the results show that this antibody targets cytosine-rich DNA sequences rather than the i-motif specifically. Other results even indicate that this antibody can unfold the i-motif, further suggesting that it binds to unfolded C-rich sequences rather than to i-motifs. Overall, the results presented in this study show that none of the tested compounds could stabilize the i-motif by directly interacting with it, highlighting the difficulties of targeting this DNA structure. Additionally, the results concerning the iMab antibody call into question the interpretation of nuclear foci observed in other studies, which currently represent the only evidence of native i-motifs at the cellular level
4
Sharma, Amit. « The In Vitro Interactions Between Tubulin and HIV-1 Rev Require Rev’s Multimerization and Arginine-Rich Motifs ». Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1261408567.
Texte intégral
5
Collin, Delphine. « Etudes par methodes spectroscopiques de complexes d'oligonucleotides (motifs-i et interaction boucle-boucle) (doctorat : pharmacochimie) ». Paris 11, 1999. http://www.theses.fr/1999PA114835.
Texte intégral
6
Salisbury, Richard L. Jr. « TCDD represses 3'IghRR activation through an AhR-dependent shift in the NF-κB/Rel protein complexes binding to κB motifs within the hs1,2 and hs4 enhancers ». Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1401136335.
Texte intégral
7
Rais, Nabila. « Représentation de la pensée politique italienne à la croisée du dix-neuvième et vingtième siècle : Lire "I Viceré" de De Roberto et "I vecchi e i giovani" de Pirandello à la lumière du "Prince" de Machiavel ». Grenoble 3, 2007. http://www.theses.fr/2007GRE39012.
Texte intégralRésumé :
Cette thèse a pour thème la représentation de la pensée politique italienne à travers la lecture de deux romans situés à la croisée du 19e et 20e siècle. L'objectif de notre recherche est de lire ces deux romans historiques à la lumière d'une pensée politique révolutionnaire celle de Nicolas Machiavel. Après avoir tenté de cerner les particularités du secrétaire florentin, exposé ses idées révolutionnaires et la spécificité de sa pensée, cette étude se poursuit avec un double objectif. Le premier est l'élaboration d'une approche analytique des deux romans : "I Viceré" de Federico De Roberto et "I vecchi e i giovani" de Luigi Pirandello, de même qu'un essai critique, basé sur la consultation de la spécificité et de la tendance narrative de chaque auteur, pour enfin venir à l'étude approfondie des différentes galeries des personnages. En effet, cette thèse propose une étude des personnages qui nous renvoie sans cesse aux sentences de Machiavel et souligne la présence irrévocable de l'esprit de ce dernier dans les deux romans respectifs. L'étude se précise par son aspect comparatif, l'objectif principal étant d'établir une correspondance entre d'une part, ces deux romans du 19e et 20e siècle et d'autre part, les préceptes politiques de Machiavel, principalement contenu dans son opuscule "Le Prince". Cette seconde démarche précise l'authenticité et la véracité de la théorie de Machiavel en corrélation avec une certaine réalité politique italienne qui malgré une constante évolution, reste soumise aux mêmes et éternelles lois du champ politique tel que l'aperçoit MachiavelThis thesis has for subject the representation of the Italian political through the reading of two novels situated between the 19th and 20th century. The Objective of our research is to read these historical novels in the light of a revolutionary political thought that of Nicola Machiavelli. Having tried to encircle the characteristics of the Florentine secretary, and so explain its revolutionary ideas and the specificity of its thought, this study continues with a double objective. The first one is the elaboration of an analytical approach of both novels : "I Viceré" Federico of De Roberto and "I vecchi e I giovani" o Luigi Pirandello, as well as a critical essay based on the consultation of the specificity and the narrative tendency of every author, to come finally to the detailed study of the various galleries of characters of both respective novels. Indeed, this thesis proposes a study of the characters which always sends us back to Macchiavelli's judgments and underlines the irrevocable presence of the spirit of this last one. The study becomes clearer by its comparative aspect, the main objective being to establish a correspondence between on one hand these two novels of the 19th and 20th century and on the other hand Machiavelli's political rules, mainly contained in his opuscule "The Prince". This second step clarifies the authenticity and the truthfulness of Machiavelli's theory in correlation with a certain Italian political reality which in spite of a constant evolution, remains subjected to the same and the eternal laws of the political arena such as Machiavelli perceives it
8
Sanchez, David Raul Yusef. « Identification of the viral RNA ligands and host protein partners of the Rig-I Like Receptors in an active infection by viruses of positive and negative polarity ». Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCC262.
Texte intégralRésumé :
Les infections virales peuvent avoir des conséquences dévastatrices pour l'hôte et doivent donc être contrôlés rapidement et efficacement par l'immunité innée antivirale. Les récepteurs de type Rig-I-like (RLR: Rig-I, MDA5 et LGP2) sont en première ligne de la course de l'évolution entre les virus et le système immunitaire de l'hôte. Ils jouent un rôle majeur dans la détection des infections par les virus à ARN pour initier et moduler l'immunité antivirale. Lors de la liaison de l'ARN, les RLR déclenchent une cascade de signalisation en aval résultant dans l'expression des interférons de type I, de cytokines pro-inflammatoires et d'un ensemble diversifié de gènes antiviraux. Une décennie après leur découverte, la cascade de signalisation impliquée dans la réponse RLR est bien connue, cependant, les mécanismes moléculaires qui conduisent à leur activation ont encore besoin d'être éclaircis. En effet, à l'intérieur d'une cellule infectée, les RLR interagissent avec des ARNs viraux, mais aussi avec des partenaires protéiques cellulaires. La plupart d'entre eux sont encore méconnus. Ainsi des stratégies novatrices sont nécessaires pour identifier les réseaux spatio-temporels d'interactions moléculaires des RLR à l'intérieur des cellules infectées. Afin d'éclaircir la nature des agonistes et des partenaires protéiques des RLR lors d'une infection virale, nous avons généré un ensemble de lignées cellulaires stables exprimant Rig-I, MDA5 et LGP2 marqués. Des approches biochimiques modernes basées sur la purification par chromatographie d'affinité des RLR suivie du séquençage à haut débit des ARNs co-purifiés, et l'analyse par spectrométrie de masse des complexes protéiques co-précipités, ont été utilisées. Comme une preuve de concept, un virus à ARN de polarité négative (virus de la rougeole, MV) et un virus de polarité positive (virus du chikungunya, CHIKV) ont été choisis. Nous avons obtenu une liste exhaustive d'interactions spécifiques virus-hôte des RLRs. Les analyses de séquençage ont révélé que des régions distinctes des génomes de MV et CHIKV sont spécifiquement reconnues. Nos résultats suggèrent que lors de l'infection MV, Rig-I reconnaît les génomes défectifs lorsque la souche virale utilisée en produit. Par contre, MDA5 et LGP2 s'associent spécifiquement avec des ARN provenant de la région codant le gène de la nucléoprotéine. Lors de l'infection CHIKV, seulement Rig-I s'associe spécifiquement à la région 3 'du génome viral. Par notre approche protéomique, nous avons établi trois listes abondantes de protéines cellulaires interagissant directement ou indirectement avec chacun des trois RLRs. Ces interactions protéine-protéine sont hautement spécifiques à la fois des RLR et des conditions. En outre plusieurs partenaires des RLR décrits précédemment ont été retrouvés dans nos listes de protéines. À notre connaissance, cette étude fournit la première visualisation simultanée des agonistes ARN et des partenaires protéiques des trois RLRs dans des cellules vivantes et en présence d'infection par différents virus à ARNVirus infections can have deVastating consequences for the host and must therefore be controlled rapidly and effectively by antiviral innate immunity. The Rig-I-like receptors (RLRs: Rig-I, MDA5 and LGP2) are at the frontline of the evolutionary race between viruses and the host immune system. They play a major role in sensing RNA virus infection to initiate and modulate antiviral immunity. Upon RNA binding, RLRs trigger a downstream signalling cascade resulting in the expression of type-I interferons, proinflammatory cytokines and a diverse set of antiviral genes. One decade after RLRs discovery, much is known on the signalling cascade involved in their response, however molecular mechanisms that lead to RLRs activation still need further elucidation. Indeed, inside an infected tell RLRs interact with particular signatures of viral RNA but also with cellular protein partners, most of them being still unknown. Thus, innovative strategies are needed to obtain spatiotemporal networks of macromolecular interactions involving RLRs inside infected tells. In order to shed light on RNA and protein partners of RLRs in physiological conditions during an active viral infection, we generated a set of stable tell fines expressing tagged Rig-I, MDA5 and LGP2 proteins. Modern biochemical approaches based on affinity purification of tagged proteins, next-generation sequencing (NGS) of RNA molecules and mass spectrometry analysis (LC-MS/MS) of protein complexes were applied. As a proof of principle one negative-sense (measles virus, MV) and one positive-sense (chikungunya virus, CHIKV) viruses were chosen. We obtained an extensive list of specific virus-host interactions between RLRs and both protein and RNA molecules. NGS analysis fi revealed that distinct regions of the MV and CHIKV genomes were specifically recognized in an RLR-dependent manner. Our findings suggests that during MV infection, Rig-I recognizes defective interfering genomes only if the viral strain produces them, whereas MDA5 and LGP2 specifically associate with RNA species originating from the MV nucleoprotein coding region. During CHIKV infection, only Rig-I was found to bind specifically the 3' untranslated region of the viral genome. Using our proteomic approach we established three prosperous lists of cellular proteins interacting either directly or indirectly with each of the three RLRs. These protein-protein interactions were highly specific because they were RLR-specific and conditions-dependent. Additionally, several previously described specific RLR partners were present in our protein lists. To our knowledge this study provides the first simultaneous visualisation of specific RNA and protein partners for Rig-I, MDA5 and LGP2 in living tells in the presence of different RNA viruses
9
D'Amours, Benoît. « Retourner la bêche : les fonctions de l'autobiographie dans l'œuvre de Stanley Cavell ». Doctoral thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/69493.
Texte intégralRésumé :
Mon objectif ici sera de montrer que Cavell fait de l’autobiographie un exercice d’investigation philosophique. Afin d’atteindre ce but, j’emprunte une approche chronologique. Analysant une par une ses publications les plus importantes, je démontre que l’autobiographie remplit cinq fonctions distinctes dans son œuvre à savoir, une fonction descriptive, une fonction anthropologique, une fonction révisionniste, une fonction morale et une fonction perfectionniste. Ensuite, j’analyse le rapport entre le perfectionnisme moral et le récit autobiographie de Cavell intitulé Si j’avais su. Ma thèse trouve son originalité dans le fait que les commentateurs accordent généralement une faible attention au rôle de l’autobiographie dans l’œuvre de ce penseur. D’ailleurs, ce n’est que tardivement que celui-ci indique que l’autobiographie a toujours joué un rôle important dans ses écrits. Mon intention était donc de relire l’œuvre de Cavell afin de mettre en évidence l’importance de l’autobiographie dans sa pensée.
10
Bergmann, Tobias [Verfasser]. « Determination of quantitative peptide-binding motifs of four common equine MHC class I alleles, and identification of an equine herpesvirus type 1-derived cytotoxic T lymphocyte epitope / Tobias Bergmann ». Berlin : Freie Universität Berlin, 2017. http://d-nb.info/1126505285/34.
Texte intégralLivres sur le sujet "I-Motifs"
1
Martin, Jean-Pierre. Les Motifs dans la chanson de geste : Définition et utilisation (discours de l'épopée médiévale,I). Lille : Centre d'études médiévales et dialectales, Université de Lille III, 1992.
Trouver le texte intégral
2
Slade, Iris. Između srca i želuca : Neki primjeri animalistike u splitskoj likovnoj umjetnosti = Between heart and stomach : animalistic motifs in Split's visual arts. Split : Galerija umjetnina, 2020.
Trouver le texte intégral
3
Karlsson, Olof. Transcriptional regulation of the rat insulin I gene : Identification of Cis-acting motifs and cloning of an islet-specific homeobox-containing gene. Umeaa : University of Umeaa, 1990.
Trouver le texte intégral
4
Peshekhonova, Larisa. Suprematicheskoe predvidenie : Kosmos v ukrashenii︠a︡kh i grafike Nadi Lezhe = Suprematism vision : Space Motifs in the Graphic Works and Jewelry Designs of Nadia Léger. Moskva : Gosudarstvennyĭ istoriko-kulʹturnyĭ muzeĭ zapovednik "Moskovskiĭ Kremlʹ", 2021.
Trouver le texte intégral
5
Krajewska, Monika. W papierze i kamieniu : Motywy symboliki żydowskiej w wycinankach i rysunkach Moniki Krajewskiej : luty-marzec 2000, Państwowe Muzeum Etnograficzne w Warszawie = In paper and in stone : Jewish symbolic motifs in papercuts and tombstone rubbings / by Monika Krajewska. Warszawa : Państwowe Muzeum Etnograficzne w Warszawie, 2000.
Trouver le texte intégral
6
Lavlinskiĭ, S. P., et Viktorii︠a︡ Malkina. Grotesknoe i fantasticheskoe v kulʹture : Vizualʹnye aspekty : sbornik stateĭ. B. m : Izdatelʹskie reshenii︠a︡, 2017.
Trouver le texte intégral
7
Peer-Brie, Jérémie, et Martin Voyer. Utopies, fictions et satires politiques I : Cycle de conférences 2017. Québec, Québec] : Presses de l'Université Laval, 2018.
Trouver le texte intégral
8
Viktor, Bondarenko, Malʹt︠s︡eva Evgenii︠a︡, Popov Sergeĭ et Galerei︠a︡ Gelʹmana, dir. Dukhovnai︠a︡ branʹ : Proekt Viktora Bondarenko i Evgenii Malʹt︠s︡evoĭ : borʹba za novui︠u︡ zhiznʹ v iskusstve sakralʹnykh obrazov khristianstva : rasshirennyĭ katalog proekta, predstavlennogo v Galeree Marata Gelʹmana v T︠S︡entre sovremennogo iskusstva "Vinzavod". Moskva : Rossii︠a︡ dli︠a︡ vsekh, 2012.
Trouver le texte intégral
9
ʻAlī, Maḥmūdiyān, et Gūshah Fāṭimah, dir. Yak khānah dar naqsh : Pizhūhishī dar ārāyahʹhā-yi miʻmārī-i Qalʻah-i Chālishtar, mutiʻalliq bih dawrah-i Qājār (ḥajjārrīʹhā-yi naqshpardāzānah va naqqāshīʹhā-yi dīvarī-i khānahʹhā-yi Aḥmad Khān va Maḥmūd Khān) bā taʼkīd bar gūnahʹshināsī-i nuqūsh, mustanadʹsāzī, tadvīn-i sābiqah va shināsnāmah-i naqshʹhā = House in motif. Iṣfahān : Guldastah, 2014.
Trouver le texte intégral
10
Pool, Daniel. What Jane Austen ate and Charles Dickens knew : Fascinating facts of daily life in the nineteenth century. London : Robinson, 1998.
Trouver le texte intégralChapitres de livres sur le sujet "I-Motifs"
1
Trautwein, Nico, et Stefan Stevanović. « Establishing MHC Class I Peptide Motifs ». Dans Antigen Processing, 159–68. Totowa, NJ : Humana Press, 2012. http://dx.doi.org/10.1007/978-1-62703-218-6_13.
Texte intégral
2
Naegeli, Hanspeter. « Molecular Recognition Strategies I : One Enzyme-One Substrate Motifs ». Dans Mechanisms of DNA Damage Recognition in Mammalian Cells, 71–92. Boston, MA : Springer US, 1997. http://dx.doi.org/10.1007/978-1-4684-6468-9_4.
Texte intégral
3
Bhavsar-Jog, Yogini P., Samantha M. Reilly et Randy M. Wadkins. « DNA G-Quadruplexes and I-Motifs in Therapeutics and Diagnostics ». Dans Chemical Biology of Nucleic Acids, 441–58. Berlin, Heidelberg : Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-54452-1_24.
Texte intégral
4
Ghosh, Michael, Moreno Di Marco et Stefan Stevanović. « Identification of MHC Ligands and Establishing MHC Class I Peptide Motifs ». Dans Antigen Processing, 137–47. New York, NY : Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9450-2_11.
Texte intégral
5
Stead, Evanghelia. « 2. A Foetal Laboratory and Its Influence ». Dans Grotesque and Performance in the Art of Aubrey Beardsley, 57–106. Cambridge, UK : Open Book Publishers, 2024. http://dx.doi.org/10.11647/obp.0413.02.
Texte intégralRésumé :
Chapter 2, A Foetal Laboratory and Its Influence, studies the foetus motif in Beardsley’s oeuvre from its earliest provocative advent in Incipit Vita Nova (1892) and among the Bon-Mots vignettes up to the untimely end of his career. I grant primacy not to biographical detail (as usual in prior scholarship) but to the motif’s creative and cultural bearings, and its challenging manifesto-like value as portrait of a generation. The chapter shows the foetus’s symbolic meaning for the decadent post-Darwinian zeitgeist and stresses its role as a plastic and morphing stimulus with immediate effect on fin-de-siècle graphic design. It analyses the motif's influence and spread in the work of German artist Marcus Behmer (foetal variations), Dutchman Karel de Nérée tot Babberich (mises en abyme), and French anarchist Jossot (defending caricature as a superior form of deforming art).
6
Jacob Ramalho, Joana. « Conclusion : Routes of Re-membering ». Dans Palgrave Gothic, 265–75. Cham : Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-73628-5_9.
Texte intégralRésumé :
AbstractThe cinematic gothic aesthetic, as I have described it in these pages, is an aesthetics of memory, accented in its transcultural authorial roots and displaced characters. The accented style of the films responds to the directors’ socio-cultural condition of displacement, inscribing into the mise-en-scène, atmosphere, and plotlines experiences of dislocation, trespassing, claustrophobia, unbelonging, loss, change, and motifs of itinerancy. In their paralleling of life and art, the films become visual archives of mourning: cinematic representations of personal memory sifted through the realisation that the past is forever lost, memory is always reconstructed and contaminated by the imagination, identity is porous, and happiness is either unattainable or resides in death. Driven by an overpowering and often maddening impetus to re-collect, the characters attempt to ground their lives in something tangible, something that can be held, preserved, and revisited to counteract the prevailing instability of their existence. Amid the ruptures and fissures of memory, objects represent fixity and continuity; yet, the characters’ affective, haptic encounters with memory-objects merely feed their obsession with re-membering and thus ultimately constitute a further motif of exile. Haunted, incomplete, often divorced or estranged from a sense of identity, the gothic subject that emerges from these films stands as an avatar of a fractured, postmodern selfhood, with its multiple, disjointed voices and fragmented personae.
7
Wegener, Anne-Marie K., et Bernard Malissen. « Analysis of the (YXXL/I)2 Signalling Motifs Found in the Cytoplasmic Segment of the Mouse CD3-ζ Chain ». Dans Advances in Experimental Medicine and Biology, 45–51. Boston, MA : Springer US, 1994. http://dx.doi.org/10.1007/978-1-4899-0987-9_5.
Texte intégral
8
Ashwin-Siejkowski, Piotr. « Reception of the Johannine Motifs in Heracleon's Commentary on the Gospel of John and the Tripartite Tractate, NHC, I, 5 ». Dans Valentinus' Legacy and Polyphony of Voices, 117–40. London : Routledge, 2021. http://dx.doi.org/10.4324/9781003181095-7.
Texte intégral
9
Waller, Zoë A. E. « i-Motif Nucleic Acids ». Dans Handbook of Chemical Biology of Nucleic Acids, 139–66. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-9776-1_97.
Texte intégral
10
Waller, Zoë A. E. « i-Motif Nucleic Acids ». Dans Handbook of Chemical Biology of Nucleic Acids, 1–28. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-16-1313-5_97-1.
Texte intégralActes de conférences sur le sujet "I-Motifs"
1
Zhao, Jingjing, Jianfang Zhu, Zhengfang Qian et Shuting Fan. « Application of DNA i-Motifs based Nanobiotechnology for THz biosensing and imaging ». Dans 2024 49th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 1–2. IEEE, 2024. http://dx.doi.org/10.1109/irmmw-thz60956.2024.10697542.
Texte intégral
2
Udovičić, Bojana B. « MOTIV PRIJATELjSTVA U ROMANIMA „MALI PRINC“ ANTOANA DE SENT-EGZIPERIJA I „AGI I EMA“ IGORA KOLAROVA ». Dans KNjIŽEVNOST ZA DECU U NAUCI I NASTAVI. University of Kragujevac, Faculty of Education in Jagodina, 2022. http://dx.doi.org/10.46793/kdnn21.127u.
Texte intégralRésumé :
By using a comparative analysis, the paper discusses the similarity of motifs in two novels – a classic of children’s literature, Exypery’s The Little Prince, and Agi i Ema, a contemporary Serbian novel for children. In both novels, extraordinary friendship between characters develops as a result of children’s loneliness and detachment. The characters and the adventures belong both to the real and the unreal world, which is the essence of fiction.
3
SAVOIE, C. J., N. KAMIKAWAJI, T. SASAZUKI et S. KUHARA. « Use of BONSAI decision trees for the identification of potential MHC Class I peptide epitope motifs ». Dans Proceedings of the Pacific Symposium. WORLD SCIENTIFIC, 1998. http://dx.doi.org/10.1142/9789814447300_0018.
Texte intégral
4
Hu, Weipeng, Si Qiu, Youping Li, Geng Liu, Xiuqing Zhang et Leo J. Lee. « Abstract 3383 : EPIC : MHC-I epitope prediction integrating mass spectrometry derived motifs and tissue-specific expression profiles ». Dans Proceedings : AACR Annual Meeting 2019 ; March 29-April 3, 2019 ; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.am2019-3383.
Texte intégral
5
Hu, Weipeng, Si Qiu, Youping Li, Geng Liu, Xiuqing Zhang et Leo J. Lee. « Abstract 3383 : EPIC : MHC-I epitope prediction integrating mass spectrometry derived motifs and tissue-specific expression profiles ». Dans Proceedings : AACR Annual Meeting 2019 ; March 29-April 3, 2019 ; Atlanta, GA. American Association for Cancer Research, 2019. http://dx.doi.org/10.1158/1538-7445.sabcs18-3383.
Texte intégral
6
Yeh, Chin-Chia Michael, Yan Zhu, Liudmila Ulanova, Nurjahan Begum, Yifei Ding, Hoang Anh Dau, Diego Furtado Silva, Abdullah Mueen et Eamonn Keogh. « Matrix Profile I : All Pairs Similarity Joins for Time Series : A Unifying View That Includes Motifs, Discords and Shapelets ». Dans 2016 IEEE 16th International Conference on Data Mining (ICDM). IEEE, 2016. http://dx.doi.org/10.1109/icdm.2016.0179.
Texte intégral
7
Riley, Graham. « MMP and Matrix Degradation in Tendon ». Dans ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53233.
Texte intégralRésumé :
Tendons are often affected by chronic pain and rupture, particularly in the middle-aged and elderly, but also in the sporting and physically active younger population. Although not life threatening, these conditions (‘tendinopathy’) are major causes of morbidity, and estimated to cost tens of millions of pounds every year in lost productivity. I have previously shown that the organisation and composition of the tendon extracellular matrix (ECM) are substantially altered in tendinopathy, and that these changes may predispose to tendon pain and rupture. I have also shown that most tendinopathy is degenerative, with changes in fibroblast activity and increased ECM turnover. ECM degradation, in both normal physiology and pathology, is largely mediated by metalloproteinase enzymes: the matrix metalloproteinases (MMP) and the ‘A Disintegrin And Metalloproteinase with ThromboSpondin motifs’ (ADAMTS). I have previously shown that there are differences in MMP activity in chronic tendinopathy compared to acute tendon injuries, as well as differences in collagen turnover between tendons. Thus, although it is not known which enzymes are implicated, perturbation of the balance of metalloproteinase activities is a potential cause of tendinopathy.
8
Chensheng, Ma, Chan Ruth Chau-Ting et Kwok Wai-Ming. « Ultrafast time-resolved fluorescence study on formation and excitation dynamics of human telomeric and homo-oligomeric i-motifs at neutral pH ». Dans Asian Spectroscopy Conference 2020. Institute of Advanced Studies, Nanyang Technological University, 2020. http://dx.doi.org/10.32655/asc_8-10_dec2020.73.
Texte intégral
9
Arroita Azkarate, Izaro. « Conflicting Memories and Families in Conflict : Identity and Otherness in Contemporary Basque Literature ». Dans XII Congress of the ICLA. Georgian Comparative Literature Association, 2024. https://doi.org/10.62119/icla.2.8454.
Texte intégralRésumé :
Contemporary Basque literature shows a clear interest in our conflictive past. A growing number of works deal with the Spanish Civil War, Franco's dictatorship, or all that we commonly call the ‘Basque conflict’. Although there is a variety of literary perspectives and approaches, we can observe some recurring motifs that may be especially significant for understanding the negotiations on memory and identity in the Basque Country. Specifically, I will analyze some narratives in which that Other who can be represented as a perpetrator or as a political opponent (a Falangist, a terrorist), also appears as a relative, as a member who destabilizes the family genealogy, and provokes an identity crisis, both individual and collective. From this perspective, I will analyze novels such as Atertu arte itxaron (Agirre, 2015, translated into Spanish as Los turistas desganados) or Soinujo-learen semea (Atxaga, 2003, translated into English as The Accordionist's son, 2008), but also chronicles such as Gurea falangista zen (Barandiaran, 2021, ['Ours was Falangist']). This analysis will lead us to reflect on the problematic (de)construction of Basque identity in the present, and on the main role played by our conflicting memories in this process.
10
Kukovec, Rok, Špela Pečnik, Iztok Fister Jr. et Sašo Karakatič. « Adversarial Image Perturbation with a Genetic Algorithm ». Dans 7th Student Computer Science Research Conference. University of Maribor Press, 2021. http://dx.doi.org/10.18690/978-961-286-516-0.6.
Texte intégralRésumé :
The quality of image recognition with neural network models relies heavily on filters and parameters optimized through the training process. These filters are di˙erent compared to how humans see and recognize objects around them. The di˙erence in machine and human recognition yields a noticeable gap, which is prone to exploitation. The workings of these algorithms can be compromised with adversarial perturbations of images. This is where images are seemingly modified imperceptibly, such that humans see little to no di˙erence, but the neural network classifies t he m otif i ncorrectly. This paper explores the adversarial image modifica-tion with an evolutionary algorithm, so that the AlexNet convolutional neural network cannot recognize previously clear motifs while preserving the human perceptibility of the image. The ex-periment was implemented in Python and tested on the ILSVRC dataset. Original images and their recreated counterparts were compared and contrasted using visual assessment and statistical metrics. The findings s uggest t hat t he human eye, without prior knowledge, will hardly spot the di˙erence compared to the original images.
Rapports d'organisations sur le sujet "I-Motifs"
1
Whitham, Steven A., Amit Gal-On et Victor Gaba. Post-transcriptional Regulation of Host Genes Involved with Symptom Expression in Potyviral Infections. United States Department of Agriculture, juin 2012. http://dx.doi.org/10.32747/2012.7593391.bard.
Texte intégralRésumé :
Understanding how RNA viruses cause disease symptoms in their hosts is expected to provide information that can be exploited to enhance modern agriculture. The helper component-proteinase (HC-Pro) protein of potyviruses has been implicated in symptom development. Previously, we demonstrated that symptom expression is associated with binding of duplex small-interfering-RNA (duplex-siRNA) to a highly conserved FRNK amino acid motif in the HC-Pro of Zucchini yellow mosaic virus (ZYMV). This binding activity also alters host microRNA (miRNA) profiles. In Turnip mosaic virus (TuMV), which infects the model plant Arabidopsis, mutation of the FRNK motif to FINK was lethal providing further indication of the importance of this motif to HC-Pro function. In this continuation project, our goal was to further investigate how ZYMV and TuMV cause the mis-expression of genes in cucurbits and Arabidopsis, respectively, and to correlate altered gene expression with disease symptoms. Objective 1 was to examine the roles of aromatic and positively charged residues F164RNH and K215RLF adjacent to FR180NK in small RNA binding. Objective 2 was to determine the target genes of the miRNAs which change during HC-Pro expression in infected tissues and transgenic cucumber. Objective 3 was to characterize RNA silencing mechanisms underlying differential expression of host genes. Objective 4 was to analyze the function of miRNA target genes and differentially expressed genes in potyvirus-infected tissues. We found that the charged K/R amino acid residues in the FKNH and KRLF motifs are essential for virus viability. Replacement of K to I in FKNH disrupted duplex-siRNA binding and virus infectivity, while in KRLF mutants duplex-siRNA binding was maintained and virus infectivity was limited: symptomless following a recovery phenomenon. These findings expanded the duplex-siRNA binding activity of HC-Pro to include the adjacent FRNK and FRNH sites. ZYMV causes many squash miRNAs to hyper-accumulate such as miR166, miR390, mir168, and many others. Screening of mir target genes showed that only INCURVATA-4 and PHAVOLUTA were significantly upregulated following ZYMVFRNK infection. Supporting this finding, we found similar developmental symptoms in transgenic Arabidopsis overexpressing P1-HC-Pro of a range of potyviruses to those observed in miR166 mutants. We characterized increased transcription of AGO1 in response to infection with both ZYMV strains. Differences in viral siRNA profiles and accumulation between mild and severe virus infections were characterized by Illumina sequencing, probably due to the differences in HC-Pro binding activity. We determined that the TuMV FINK mutant could accumulate and cause symptoms in dcl2 dcl4 or dcl2 dcl3 dcl4 mutants similar to TuMV FRNK in wild type Arabidopsis plants. These dcl mutant plants are defective in antiviral defenses, and the results show that factors other than HC-ProFRNK motif can induce symptoms in virus-infected plants. As a result of this work, we have a better understanding of the FRNK and FKNH amino acid motifs of HC-Pro and their contributions to the duplex-siRNA binding functions. We have identified plant genes that potentially contribute to infectivity and symptoms of virus infected plants when they are mis-expressed during potyviral infections. The results establish that there are multiple underlying molecular mechanisms that lead viral pathogenicity, some dependent on HC-Pro. The potential benefits include the development of novel strategies for controlling diseases caused by viruses, methods to ensure stable expression of transgenes in genetically improved crops, and improved potyvirus vectors for expression of proteins or peptides in plants.
2
Baszler, Timothy, Igor Savitsky, Christopher Davies, Lauren Staska et Varda Shkap. Identification of bovine Neospora caninum cytotoxic T-lymphocyte epitopes for development of peptide-based vaccine. United States Department of Agriculture, mars 2006. http://dx.doi.org/10.32747/2006.7695592.bard.
Texte intégralRésumé :
The goal of the one-year feasibility study was to identify specific cytotoxic T-lymphocyte (CTL) epitopes to Neosporacaninum in the natural bovine host in order to make progress toward developing an effective peptide-based vaccine against bovine neosporosis. We tested the hypothesis that: N. caninum SRS2 peptides contain immunogenicCTLepitope clusters cross-presented by multiple bovine MHC-I and MHC-IIhaplotypes. The specific objectives were: (1) Map bovine CTLepitopes of N. caninum NcSRS-2 and identify consensus MHC-I and class-II binding motifs; and (2) Determine if subunit immunization with peptides containing N. caninum-specificCTLepitopes cross-reactive to multiple bovine MHChaplotypes induces a CTL response in cattle with disparate MHChaplotypes. Neosporosis is a major cause of infectious abortion and congenital disease in cattle, persisting in cattle herds via vertical transmission.5 N. caninum abortions are reported in Israel; a serological survey of 52 Israeli dairy herds with reported abortions indicated a 31% infection rate in cows and 16% infection rate in aborted fetuses.9,14 Broad economic loss due to bovine neosporosis is estimated at $35,000,000 per year in California, USA, and $100,000,000 (Australian) per year in Australia and New Zealand.13 Per herd losses in a Canadian herd of 50 cattle are estimated more conservatively at $2,305 (Canadian) annually.4 Up to date practical measures to reduce losses from neosporosis in cattle have not been achieved. There is no chemotherapy available and, although progress has been made toward understanding immunity to Neospora infections, no efficacious vaccine is available to limit outbreaks or prevent abortions. Vaccine development to prevent N. caninum abortion and congenital infection remains a high research priority. To this end, our research group has over the past decade: 1) Identified the importance of T-lymphocyte-mediated immunity, particularly IFN-γ responses, as necessary for immune protection to congenital neosporosis in mice,1,2,10,11 and 2) Identified MHC class II restricted CD4+ CTL in Neosporainfected Holstein cattle,16 and 3) Identified NcSRS2 as a highly conserved surface protein associated with immunity to Neospora infections in mice and cattle.7,8,15 In this BARD-funded 12 month feasibility study, we continued our study of Neospora immunity in cattle and successfully completed T-lymphocyte epitope mapping of NcSRS2 surface protein with peptides and bovine immune cells,15 fulfilling objective 1. We also documented the importance of immune responses NcSRS2 by showing that immunization with native NcSRS2 reduces congenital Neospora transmission in mice,7 and that antibodies to NcSRS2 specifically inhibition invasion of placental trophoblasts.8 Most importantly we showed that T-lymphocyte responses similar to parasite infection, namely induction of activated IFN-γ secreting Tlymphocytes, could be induced by subunit immunization with NcSRS2 peptides containing the Neospora-specificCTLepitopes (Baszler et al, In preparation) fulfilling objective 2. Both DNA and peptide-based subunit approaches were tested. Only lipopeptide-based NcSRS2 subunits, modified with N-terminal linked palmitic acid to enhance Toll-like receptors 2 and 1 (TLR2-TLR1), stimulated robust antigen-specific T-lymphocyte proliferation, IFN-γ secretion, and serum antibody production across different MHC-IIhaplotypes. The discovery of MHC-II cross-reactive T-cellinducing parasite peptides capable of inducing a potentially protective immune response following subunit immunization in cattle is of significant practical importance to vaccine development to bovine neosporosis. In addition, our findings are more widely applicable in future investigations of protective T-cell, subunit-based immunity against other infectious diseases in outbred cattle populations.
3
Weiss, David, et Neil Olszewski. Manipulation of GA Levels and GA Signal Transduction in Anthers to Generate Male Sterility. United States Department of Agriculture, 2000. http://dx.doi.org/10.32747/2000.7580678.bard.
Texte intégralRésumé :
The original objectives of the research were: i. To study the role of GA in anther development, ii. To manipulate GA and/or GA signal transduction levels in the anthers in order to generate male sterility. iii. To characterize the GA signal transduction repressor, SPY. Previous studies have suggested that gibberellins (GAs) are required for normal anther development. In this work, we studied the role of GA in the regulation of anther development in petunia. When plants were treated with the GA-biosynthesis inhibitor paclobutrazol, anther development was arrested. Microscopic analysis of these anthers revealed that paclobutrazol inhibits post-meiotic developmental processes. The treated anthers contained pollen grains but the connective tissue and tapetum cells were degenerated. The expression of the GA-induced gene, GIP, can be used in petunia as a molecular marker to: study GA responses. Analyses of GIP expression during anther development revealed that the gene is induced only after microsporogenesis. This observation further suggests a role for GA in the regulation of post-meiotic processes during petunia anther development. Spy acts as a negative regulator of gibberellin (GA) action in Arabidopsis. We cloned the petunia Spy homologue, PhSPY, and showed that it can complement the spy-3 mutation in Arabidopsis. Overexpression of Spy in transgenic petunia plants affected various GA-regulated processes, including seed germination, shoot elongation, flower initiation, flower development and the expression of a GA- induced gene, GIP. In addition, anther development was inhibited in the transgenic plants following microsporogenesis. The N-terminus of Spy contains tetratricopeptide repeats (TPR). TPR motifs participate in protein-protein interactions, suggesting that Spy is part of a multiprotein complex. To test this hypothesis, we over-expressed the SPY's TPR region without the catalytic domain in transgenic petunia and generated a dominant- negative Spy mutant. The transgenic seeds were able to germinate on paclobutrazol, suggesting an enhanced GA signal. Overexpression of PhSPY in wild type Arabidopsis did not affect plant stature, morphology or flowering time. Consistent with Spy being an O-GlcNAc transferase (OGT), Spy expressed in insect cells was shown to O-GlcNAc modify itself. Consistent with O-GlcNAc modification playing a role in GA signaling, spy mutants had a reduction in the GlcNAc modification of several proteins. After treatment of the GA deficient, gal mutant, with GA3 the GlcNAc modification of proteins of the same size as those affected in spy mutants exhibited a reduction in GlcNAcylation. GA-induced GlcNAcase may be responsible for this de-GlcNAcylation because, treatment of gal with GA rapidly induced an increase in GlcNAcase activity. Several Arabidopsis proteins that interact with the TPR domain of Spy were identified using yeast two-hybrids screens. One of these proteins was GIGANTEA (GI). Consistent with GI and Spy functioning as a complex in the plant the spy-4 was epistatic to gi. These experiments also demonstrated that, in addition to its role in GA signaling, Spy functions in the light signaling pathways controlling hypocotyl elongation and photoperiodic induction of flowering. A second Arabidopsis OGT, SECRET AGENT (SCA), was discovered. Like SPY, SCA O-GlcNAc modifies itself. Although sca mutants do not exhibit dramatic phenotypes, spy/sca double mutants exhibit male and female gamete and embryo lethality, indicating that Spy and SCA have overlapping functions. These results suggest that O-GlcNAc modification is an essential modification in plants that has a role in multiple signaling pathways.
4
Palmer, Guy, Varda Shkap, Wendy Brown et Thea Molad. Control of bovine anaplasmosis : cytokine enhancement of vaccine efficacy. United States Department of Agriculture, mars 2007. http://dx.doi.org/10.32747/2007.7695879.bard.
Texte intégralRésumé :
Anaplasmosis an arthropod-born disease of cattle caused by the rickettsia Anaplasma marginale and is an impediment to efficient production of healthy livestock in both Israel and the United States. Currently the only effective vaccines are derived from the blood of infected cattle. The risk of widespread transmission of both known and newly emergent pathogens has prevented licensure of live blood-based vaccines in the U.S. and is a major concern for their continued use in Israel. Consequently development of a safe, effective vaccine is a high priority. In this collaborative project we focused on two approaches to vaccine development. The first focused o n improving antigen delivery to livestock and specifically examined how DNA vaccines could be improved to enhance priming and expansion of the immune response. This research resulted in development and testing of two novel vaccine delivery systems--one that targeted antigen spread among dendritic cells (the key cell in priming immune responses and a follow-on construct that also specifically targeted antigen to the endosomal-lysosomal compartment the processing organelle within the dendritic cell that directs vaccine antigen to the MHC class ll-CD4* T cell priming pathway). The optimized construct targeting vaccine antigen to the dendritic cell MHC class II pathway was tested for ability to prime A. marginale specific immune responses in outbred cattle. The results demonstrated both statistically significant effects of priming with a single immunization, continued expansion of the primary immune response including development of high affinity lgG antibodies and rapid recall of the memory response following antigen challenge. This portion of the study represented a significant advance in vaccine delivery for livestock. Importantly the impact of these studies is not limited to A. marginale a s the targeting motifs are optimized for cattle and can be adapted to other cattle vaccinations by inserting a relevant pathogen-specific antigen. The second approach (which represented an addition to the project for which approval was requested as part of the first annual report) was a comparative approach between A . marginale and the Israel A . centrale vaccines train. This addition was requested as studies on Major Surface Protein( MSP)- 2 have shown that this antigen is highly antigenically variable and presented solely as a "static vaccine" antigen does not give cross-strain immunity. In contrast A. . centrale is an effective vaccine which Kimron Veterinary institute has used in the field in Israel for over 50 years. Taking advantage of this expertise, a broad comparison of wild type A. marginale and vaccine strain was initiated. These studies revealed three primary findings: i) use of the vaccine is associated with superinfection, but absence of clinical disease upon superinfection with A. marginale; ii) the A. centrale vaccine strain is not only less virulent but transmission in competent in Dermacentor spp. ticks; and iii) some but not all MSPs are conserved in basic orthologous structure but there are significant polymorphisms among the strains. These studies clearly indicated that there are statistically significant differences in biology (virulence and transmission) and provide a clear path for mapping of biology with the genomes. Based on these findings, we initiated complete genome sequencing of the Israel vaccine strain (although not currently funded by BARD) and plant to proceed with a comparative genomics approach using already sequenced wild-type A. marginale. These findings and ongoing collaborative research tie together filed vaccine experience with new genomic data, providing a new approach to vaccine development against a complex pathogen.
5
Yalovsky, Shaul, et Julian Schroeder. The function of protein farnesylation in early events of ABA signal transduction in stomatal guard cells of Arabidopsis. United States Department of Agriculture, janvier 2002. http://dx.doi.org/10.32747/2002.7695873.bard.
Texte intégralRésumé :
Loss of function mutations in the farnesyltransferase β subunit gene ERA1 (enhanced response to abscisic acid), cause abscisic acid hypersensitivity in seedlings and in guard cells. This results in slowed water loss of plants in response to drought. Farnesyltransferase (PFT) catalyses the attachment of the 15-carbon isoprenoid farnesyl to conserved cysteine residues located in a conserved C-terminal domain designated CaaX box. PFT is a heterodimeric protein comprised of an a and b sununits. The a subunit is shared between PFT and geranylgeranyltransferase-I (PGGTI) which catalyses the attachemt of the 20-carbon isoprenoid geranylgeranyl to CaaX box proteins in which the last amino acid is almost always leucine and in addition have a polybasic domain proximal to the CaaL box. Preliminary data presented in the proposal showed that increased cytoplasmic Ca2+ concentration in stomal guard cells in response to non-inductive ABA treatements. The goals set in the proposal were to characterize better how PFT (ERA1) affects ABA induced Ca2+ concentrations in guard cells and to identify putative CaaX box proteins which function as negative regulators of ABA signaling and which function is compromised in era1 mutant plants. To achieve these goals we proposed to use camelion Ca2+ sensor protein, high throughput genomic to identify the guard cell transcriptome and test prenylation of candidate proteins. We also proposed to focus our efforts of RAC small GTPases which are prenylated proteins which function in signaling. Our results show that farnesyltransferaseprenylates protein/s that act between the points of ABA perception and the activation of plasma membrane calcium influx channels. A RAC protein designated AtRAC8/AtRop10 also acts in negative regulation of ABA signaling. However, we discovered that this protein is palmitoylated and not prenylated although it contains a C-terminal CXXX motif. We further discovered a unique C-terminal sequence motif required for membrane targeting of palmitoylatedRACs and showed that their function is prenylation independent. A GC/MS based method for expression in plants, purification and analysis of prenyl group was developed. This method would allow highly reliable identification of prenylated protein. Mutants in the shared α subunit of PFT and PGGT-I was identified and characterized and was shown to be ABA hypersensitive but less than era1. This suggested that PFT and PGGT-I have opposing functions in ABA signaling. Our results enhanced the understanding of the role of protein prenylation in ABA signaling and drought resistance in plants with the implications of developing drought resistant plants. The results of our studies were published 4 papers which acknowledge support from BARD.
6
Altstein, Miriam, et Ronald Nachman. Rationally designed insect neuropeptide agonists and antagonists : application for the characterization of the pyrokinin/Pban mechanisms of action in insects. United States Department of Agriculture, octobre 2006. http://dx.doi.org/10.32747/2006.7587235.bard.
Texte intégralRésumé :
The general objective of this BARD project focused on rationally designed insect neuropeptide (NP) agonists and antagonists, their application for the characterization of the mechanisms of action of the pyrokinin/PBAN (PK-PBAN) family and the development of biostable, bioavailable versions that can provide the basis for development of novel, environmentally-friendly pest insect control agents. The specific objectives of the study, as originally proposed, were to: (i) Test stimulatory potencies of rationally designed backbone cyclic (BBC) peptides on pheromonotropic, melanotropic, myotropic and pupariation activities; (ii) Test the inhibitory potencies of the BBC compounds on the above activities evoked either by synthetic peptides (PBAN, LPK, myotropin and pheromonotropin) or by the natural endogenous mechanism; (iii) Determine the bioavailability of the most potent BBC compounds that will be found in (ii); (iv) Design, synthesize and examine novel PK/PBAN analogs with enhanced bioavailability and receptor binding; (v) Design and synthesize ‘magic bullet’ analogs and examine their ability to selectively kill cells expressing the PK/PBAN receptor. To achieve these goals the agonistic and antagonistic activities/properties of rationally designed linear and BBC neuropeptide (NP) were thoroughly studied and the information obtained was further used for the design and synthesis of improved compounds toward the design of an insecticide prototype. The study revealed important information on the structure activity relationship (SAR) of agonistic/antagonistic peptides, including definitive identification of the orientation of the Pro residue as trans for agonist activity in 4 PK/PBANbioassays (pheromonotropic, pupariation, melanotropic, & hindgut contractile) and a PK-related CAP₂b bioassay (diuretic); indications that led to the identification of a novel scaffold to develop biostbiostable, bioavailable peptidomimetic PK/PBANagonists/antagonists. The work led to the development of an arsenal of PK/PBAN antagonists with a variety of selectivity profiles; whether between different PKbioassays, or within the same bioassay between different natural elicitors. Examples include selective and non-selective BBC and novel amphiphilic PK pheromonotropic and melanotropic antagonists some of which are capable of penetrating the moth cuticle in efficacious quantities. One of the latter analog group demonstrated unprecedented versatility in its ability to antagonize a broad spectrum of pheromonotropic elicitors. A novel, transPro mimetic motif was proposed & used to develop a strong, selective PK agonist of the melanotropic bioassay in moths. The first antagonist (pure) of PK-related CAP₂b diuresis in flies was developed using a cisPro mimetic motif; an indication that while a transPro orientation is associated with receptor agonism, a cisPro orientation is linked with an antagonist interaction. A novel, biostablePK analog, incorporating β-amino acids at key peptidase-susceptible sites, exhibited in vivo pheromonotropic activity that by far exceeded that of PBAN when applied topically. Direct analysis of neural tissue by state-of-the-art MALDI-TOF/TOF mass spectrometry was used to identify specific PK/PK-related peptides native to eight arthropod pest species [house (M. domestica), stable (S. calcitrans), horn (H. irritans) & flesh (N. bullata) flies; Southern cattle fever tick (B. microplus), European tick (I. ricinus), yellow fever mosquito (A. aegypti), & Southern Green Stink Bug (N. viridula)]; including the unprecedented identification of mass-identical Leu/Ile residues and the first identification of NPs from a tick or the CNS of Hemiptera. Evidence was obtained for the selection of Neb-PK-2 as the primary pupariation factor of the flesh fly (N. bullata) among native PK/PK-related candidates. The peptidomic techniques were also used to map the location of PK/PK-related NP in the nervous system of the model fly D. melanogaster. Knowledge of specific PK sequences can aid in the future design of species specific (or non-specific) NP agonists/antagonists. In addition, the study led to the first cloning of a PK/PBAN receptor from insect larvae (S. littoralis), providing the basis for SAR analysis for the future design of 2ⁿᵈgeneration selective and/or nonselective agonists/antagonists. Development of a microplate ligand binding assay using the PK/PBAN pheromone gland receptor was also carried out. The assay will enable screening, including high throughput, of various libraries (chemical, molecular & natural product) for the discovery of receptor specific agonists/antagonists. In summary, the body of work achieves several key milestones and brings us significantly closer to the development of novel, environmentally friendly pest insect management agents based on insect PK/PBANNPs capable of disrupting critical NP-regulated functions.
7
Altstein, Miriam, et Ronald J. Nachman. Rational Design of Insect Control Agent Prototypes Based on Pyrokinin/PBAN Neuropeptide Antagonists. United States Department of Agriculture, août 2013. http://dx.doi.org/10.32747/2013.7593398.bard.
Texte intégralRésumé :
The general objective of this study was to develop rationally designed mimetic antagonists (and agonists) of the PK/PBAN Np class with enhanced bio-stability and bioavailability as prototypes for effective and environmentally friendly pest insect management agents. The PK/PBAN family is a multifunctional group of Nps that mediates key functions in insects (sex pheromone biosynthesis, cuticular melanization, myotropic activity, diapause and pupal development) and is, therefore, of high scientific and applied interest. The objectives of the current study were: (i) to identify an antagonist biophores (ii) to develop an arsenal of amphiphilic topically active PK/PBAN antagonists with an array of different time-release profiles based on the previously developed prototype analog; (iii) to develop rationally designed non-peptide SMLs based on the antagonist biophore determined in (i) and evaluate them in cloned receptor microplate binding assays and by pheromonotropic, melanotropic and pupariation in vivo assays. (iv) to clone PK/PBAN receptors (PK/PBAN-Rs) for further understanding of receptor-ligand interactions; (v) to develop microplate binding assays for screening the above SMLs. In the course of the granting period A series of amphiphilic PK/PBAN analogs based on a linear lead antagonist from the previous BARD grant was synthesized that incorporated a diverse array of hydrophobic groups (HR-Suc-A[dF]PRLa). Others were synthesized via the attachment of polyethylene glycol (PEG) polymers. A hydrophobic, biostablePK/PBAN/DH analog DH-2Abf-K prevented the onset of the protective state of diapause in H. zea pupae [EC50=7 pmol/larva] following injection into the preceding larval stage. It effectively induces the crop pest to commit a form of ‘ecological suicide’. Evaluation of a set of amphiphilic PK analogs with a diverse array of hydrophobic groups of the formula HR-Suc-FTPRLa led to the identification of analog T-63 (HR=Decyl) that increased the extent of diapause termination by a factor of 70% when applied topically to newly emerged pupae. Another biostablePK analog PK-Oic-1 featured anti-feedant and aphicidal properties that matched the potency of some commercial aphicides. Native PK showed no significant activity. The aphicidal effects were blocked by a new PEGylated PK antagonist analog PK-dF-PEG4, suggesting that the activity is mediated by a PK/PBAN receptor and therefore indicative of a novel and selective mode-of-action. Using a novel transPro mimetic motif (dihydroimidazole; ‘Jones’) developed in previous BARD-sponsored work, the first antagonist for the diapause hormone (DH), DH-Jo, was developed and shown to block over 50% of H. zea pupal diapause termination activity of native DH. This novel antagonist development strategy may be applicable to other invertebrate and vertebrate hormones that feature a transPro in the active core. The research identifies a critical component of the antagonist biophore for this PK/PBAN receptor subtype, i.e. a trans-oriented Pro. Additional work led to the molecular cloning and functional characterization of the DH receptor from H. zea, allowing for the discovery of three other DH antagonist analogs: Drosophila ETH, a β-AA analog, and a dF analog. The receptor experiments identified an agonist (DH-2Abf-dA) with a maximal response greater than native DH. ‘Deconvolution’ of a rationally-designed nonpeptide heterocyclic combinatorial library with a cyclic bis-guanidino (BG) scaffold led to discovery of several members that elicited activity in a pupariation acceleration assay, and one that also showed activity in an H. zea diapause termination assay, eliciting a maximal response of 90%. Molecular cloning and functional characterization of a CAP2b antidiuretic receptor from the kissing bug (R. prolixus) as well as the first CAP2b and PK receptors from a tick was also achieved. Notably, the PK/PBAN-like receptor from the cattle fever tick is unique among known PK/PBAN and CAP2b receptors in that it can interact with both ligand types, providing further evidence for an evolutionary relationship between these two NP families. In the course of the granting period we also managed to clone the PK/PBAN-R of H. peltigera, to express it and the S. littoralis-R Sf-9 cells and to evaluate their interaction with a variety of PK/PBAN ligands. In addition, three functional microplate assays in a HTS format have been developed: a cell-membrane competitive ligand binding assay; a Ca flux assay and a whole cell cAMP ELISA. The Ca flux assay has been used for receptor characterization due to its extremely high sensitivity. Computer homology studies were carried out to predict both receptor’s SAR and based on this analysis 8 mutants have been generated. The bioavailability of small linear antagonistic peptides has been evaluated and was found to be highly effective as sex pheromone biosynthesis inhibitors. The activity of 11 new amphiphilic analogs has also been evaluated. Unfortunately, due to a problem with the Heliothis moth colony we were unable to select those with pheromonotropic antagonistic activity and further check their bioavailability. Six peptides exhibited some melanotropic antagonistic activity but due to the low inhibitory effect the peptides were not further tested for bioavailability in S. littoralis larvae. Despite the fact that no new antagonistic peptides were discovered in the course of this granting period the results contribute to a better understanding of the interaction of the PK/PBAN family of Nps with their receptors, provided several HT assays for screening of libraries of various origin for presence of PK/PBAN-Ragonists and antagonists and provided important practical information for the further design of new, peptide-based insecticide prototypes aimed at the disruption of key neuroendocrine physiological functions in pest insects.