| 词汇 | example_english_helix |
| 释义 | Examples of helixThese examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. Effect of a triplex-binding ligand on parallel and antiparallel triple helices using short unmodified and arcidine-linked oligonucleotides. The component helices might be held together only by the continuity of the strands, or they might undergo pairwise coaxial stacking. The outer surface is formed by a -hairpin and two helices. The catalytic subunit has an overall -helical structure containing five helices. At # low salt concentration the junction is extended, with no stacking of helices. As with the other structures, the junction is a right-handed antiparallel cross of pairwise, coaxially stacked helices. The dynamic programming methods predict a larger proportion of long range helices than actually occur. Isolated base pairs are usually unstable ; hence, helices usually consist of at least two pairs. In this model, the amphipathic peptide helices associate to form a bundle, which resembles a barrel composed of helices as staves. Sensor domains were identified as the segment between predicted transmembrane helices associated with histidine kinase domains. Thus, fusion between double helices can occur between strands of the same polarity or of opposite polarity. The inner wall of the complex is formed by the 9 a-apoprotein helices. The peptides are 20 and 23 residues long respectively and are predicted to form amphipathic helices. In the latter cases, the coupling efficiency will depend on the nature of the interactions between helices. A mean of 81 % of the welldetermined helices are present in the comparative structure. The chain encodes the two helices that form the sides and floor of the peptidebinding groove. As judged from dichroic measurements, the helices appeared to be oriented more perpendicular than parallel to the plane of the lipid bilayer. Conformational transitions of duplex and triplex nucleic acid helices : thermodynamic analysis of effects of salt concentration on stability using preferential interaction coefficients. The outer wall is formed by the nine b-apoprotein helices. Perhaps for this reason, isolated transmembrane helices have not been much studied for their own sake. Identifying nonpolar transbilayer helices in amino acid sequences of membrane proteins. At room temperatures most sequences fold to a structure with several helices. Therefore, if the required functional structure uses long-range helices, evolution selects a sequence with unusually stable stacking energy for these helices. The procedure is repeated many times and the structure predicted is composed of the helices that appear most frequently in the set of structures generated. The enzyme core corresponds to an ()8-barrel, with eight parallel strands of sheet and eight return helices forming a ring towards the outside. The structure is an open-twisted five-stranded parallel -sheet with two helices on each side of the sheet. Structures which rely on sequence local interactions, such as helices, are preferentially stabilized. The structure revealed a four stranded -sheet packed against two helices. Coaxial stacking of the helices is a key feature of junction loops as observed in these and many other examples. The positions of the 11 transmembrane helices are shown in blue and white. However, this would still only produce a racemic mixture of equally many right- and left-handed helices. Helical structures make up some 30 % of structural elements in proteins, but peptaibols tend to form tighter 3/10 helices. Stacked bilayer helices : a new structural organization of amphiphilic molecules. Known tertiary structures are mostly for small motifs involving a small number of helices. They have shown that well-determined helices are more accurately predicted than average. Firstly, over 75 % of helices in the comparative structures have ranges of under 100. The location of helices are shown by cylinders on top of the alignment. The heart of the mechanism is thought to involve only six of the 12 helices in the permease. The second domain forms the core of the molecule and contains five helices. Consistently, interacting helices do not exhibit excimers in detergent, but only after reconstitution into membranes. The interaction energies arise from the free energy of burying hydrophobic surface area, and hydrogen bonding between side-chains (and backbone in the case of helices). Requirement of rigid-body motion of transmembrane helices for light activation of rhodopsin. Optimal bundling of transmembrane helices sparse distance constraints. Large (potentially chaotropic) ions of positive/mixed charge also cause collapse by simultaneously neutralizing surface phosphates while, at the same time, permitting interactions between adjacent helixes. Molecular dynamics simulations of isolated transmembrane helices of potassium channels. However, simple model building indicates that it should not be possible to construct a perfect three-way junction with a pair of coaxially stacked helices without breaking one or more basepairs. Elekes was actually interested in a similar problem formulated in complex space, whose interpretation in the reals involves incidences between points and helices of a certain kind in three dimensions. The helices are realistically rendered; some figurines have circular depressions in the lobes of both ears that may represent either the concha opening or the location of an ear ornament. Two of the transmembrane -helices in each monomer are nearly in axial alignment with two -helices in the apposing hemichannel - but the helices are contributed by two different monomers. The wild-type peptides formed amphipathic helices that were preferentially oriented parallel to the membrane surface, whereas the mutant peptides, although helical, were more randomly or more obliquely inserted. The simplest kinetic algorithms consist of the sequential addition of helices to structures in such a way that the free energy is lowered at each step. After secretion into the extracellular space, these helices self-assemble into fibrils of 10-300 nm in diameter, which then aggregate into fibres ranging 0.5-3 m in diameter. When starting from the 4-fold axis of the tetramer the helices in the two repeats are arranged as 2-1-3 (first repeat) and 5-4-6 (second repeat). Turns in transmembrane helices : determination of the minimal length of a ' helical hairpin ' and derivation of a fine-grained turn propensity scale. The argument is that short-range helices can form relatively easily, whereas longer-range ones form with difficulty because of the kinetic problems associated with bringing the ends into proximity. Although in principle this might occur by plugging of the pore at this point, it seems more likely that the inner helices twist, tilt, or scissor to tighten the constriction. Eight -pleated sheets formed by the aminoterminal segment of the 1 and 2 domains form a platform bound by two helices that create the sides of a cleft. However, one can imagine rotating one of the two pairs of stacked helices by 180m, such that the continuous strands now run in opposite directions to generate the antiparallel structures. Cold denaturation of monomeric peptide helices. Energetics, stability, and prediction of transmembrane helices. A turn propensity scale for transmembrane helices. Thermodynamics of oligonucleotide triple helices. Proline-induced distortions of transmembrane helices. A single helix does not provide a conduit for transmitting change ; two may work, more are better. The influence of single base triplet changes on the stability of a pur ; pur ; pyr triple helix determined by affinity cleaving. Only the longer helix gives a calculated spectrum with the ' typical ' main band near 1650 cmx1. The non-exchanging fraction presumably represents the membrane-embedded helix of this protein. Calculation of helix packing angles in protein structures. The protein belongs to the alpha-beta class, with a central beta-sheet of 5 parallel strands covered by 5 helices on either side of the sheet. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Unified nomenclature for the winged helix/forkhead transcription factors. The major and minor helices, which spiral in opposite directions, have an overall diameter of 10.8 m and 9.4 m respectively, about 3-storeys high. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. They cross laterally relative to the direction of the coiled coil to interact with the adjacent helix, and also form contacts with one another. Both domains contain the repeating structural motif of beta sheets surrounded by alpha helices. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The theory is used to examine the motion of a partial torus and a helix of finite length. The helix thus formed has a unit height of 47 nm, a unit twist of 49n1m and a pitch length of 344n7 nm. Long stretches of hydrophobic residues may indicate transmembrane helices. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The train then runs back parallel with the lift hill before entering two separate helices and entering the brake run. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The structure of polyhedrin comprises multiple beta strands, three alpha helices, and two pi helices. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. An average armadillo repeat is composed of three alpha helices. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The strength of this approach is that it also takes into account the cost of dehydrating the helix backbone and the energy for salt-bridge formation. Coaxial helices form when nucleobases from two separate helices stack, forming a pseudocontinuous helix. The intact enzyme was found to contain 38 % helix and 26 % -sheet. The first helices (in the flow direction) are small-diameter tubes, wrapped in large diameter turns. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Such long, isolated helices can also be detected by other methods, such as dielectric relaxation, flow birefringence, and measurements of the diffusion constant. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Long homopolymers of amino acids often form helices if soluble. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. The trench and the space immediately around it was peppered with obstacles of various shapes and sizes, including helixes and narrow gates. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. They showed that the complex is composed of 18 proteins having altogether 46 transmembrane helices. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Individual side-chains from these helices participate either in core packing within individual domains, or in contacts across the interdomain interface. The number of helices is expressed as a fraction of the total number of helices to make the bars comparable between different organisms. The existence of a pseudo-fivefold symmetry within the resulting bundle of 20 transmembrane helices also helped interpretation in terms of the amino-acid sequence. The helices in the present comparative structure model are shown above this line. The remaining base pairs form tertiary interactions that either span two sets of nested helices, forming a pseudoknot, or are involved in base triple interactions. However, the measured dichroism was not large, indicating that some of the helices may be oriented at different angles. Different conductance levels correspond to different numbers of helices in the bundle. All of this indicates that the perfect three-way junction does not generally fold by pairwise coaxial stacking of helices. The positioning of the different helices on the page is adjusted for artistic convenience, and is arranged so that the chain does not cross itself. The folding of helices 4-15 should be regarded as provisional. One interesting facet is that each of these three genes or pseudogenes contains three hydrophobic regions that could form transmembrane helices. Local secondary structures can form in microseconds while long-range helices or loop-loop interactions may require an extensive conformational search and are likely to be slower. These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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