No abstract

The left-handed Z-DNA conformation has been observed in crystals made from the self-complementary DNA hexamer d(CACGTG). This is the first time that a non disordered Z form is found in the crystal structure of an alternating sequence containing AT base pairs without methylated or brominated cytosines. The structure has been determined and refined to an agreement factor R = 22.9% using 746 reflections in the resolution in the resolution shell 7 to 2.5 A. The overall shape of the molecule is very similar to the Z-structure of the related hexamer d(CG)3 confirming the rigidity of the Z form. No solvent molecules were detected in the minor groove of the helix near the A bases. The disruption of the spine of hydration in the AT step appears to be a general fact in the Z form in contrast with the B form. The biological relevance of the structure in relation to the CA genome repeats is discussed.

Abstract[AQ2]The aim of this article is to determine whether the process of memorizing a tactile map key, or legend, can be improved by including three-dimensional (3D) symbols produced by means of 3D Printing. The method used in this study involved asking a group of 20 volunteers with different profiles to memorize eight tactile symbols from two keys, each of which had different characteristics: Key 2 included 3D tactile symbols and Key 1 had only two-dimensional (2D) tactile symbols. Results show statistically significant differences between the two keys. Use of Key 2 yielded a 48.72% reduction in the number of errors compared to Key 1 (N = 20, pvalue = .014). These data show that combining 3D with flat relief symbols (2D) improves the process of memorizing a tactile key because the 3D attributes can be distinguished from the 2D features by touch. For practitioners, this article provides data about the possibilities of 3D Printing applied to tactile maps, keys, and symbols. KeywordsTactile key, tactile map, tactile symbol, visual impairment ObjectiveThe aim of this article is to analyse whether including three-dimensional (3D) symbols in the key of a tactile map enables users to improve their ability to memorize it. With this objective in mind, the researchers compared two different legends: one in which the symbols were arranged in a

We synthesized and solved the crystalline structure of the oligopeptide acetyl-(glycyl-beta-alanyl)2-NH propyl. The crystal is formed by layers of helical molecules with the same chirality; however, right-handed layers alternate with left-handed ones. Inside every layer, the packing of helices is pseudohexagonal with hydrogen bonds between neighbor molecules. The structure found affords direct support for the model proposed by Crick and Rich for polyglycine II and also provides an interpretation for the structure of a newly found family of polyamides that do not form sheets as observed in most nylon structures.

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