| triple vision | Visual defect in which three images of the same object are seen. Synonym: triple vision. Origin: G. Triploos, triple, + opsis, sight (05 Mar 2000) |
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| triple X syndrome | <syndrome> In principle, the phenotypic features characteristic of trisomy of the X chromosome. Original observations (made in mental institutions) were seriously biased and the phenotypic changes spurious; now, even the remaining claim, that there is mild mental retardation, is suspect. The outstanding feature of the syndrome is the occurence of twin Barr bodies in a typical cell. (05 Mar 2000) |
| Flemming's triple stain | <technique> A stain comprised of safranin, methyl violet, and orange G. (05 Mar 2000) |
| a helix | The helical (commonly right-handed) form present in many proteins, deduced by Pauling and Corey from X-ray diffraction studies of proteins such as alpha-keratin; the helix is stabilised by hydrogen bonds between, e.g., ==C==O and HN== groups (symbolised by the centre dot in ==CO-HN==) of different eupeptide bonds. In a true a helix, there are 3.6 amino acid residues per turn of the helix. Synonym: 3.613 helix, Pauling-Corey helix. Collagen helix, an extended left-handed helix resulting from the high levels of glycine, l-proline, and l-hydroxyproline present in the collagens. There are 3.3 amino acids per turn of the helix. Three of those left-handed helices form a triple superhelix that is right-handed. (05 Mar 2000) |
| alpha helix | <molecular biology> A particular helical folding of the polypeptide backbone in protein molecules (both fibrous and globular), in which the carbonyl oxygens are all hydrogen bonded to amide nitrogen atoms three residues along the chain. The translation of amino acid residues along the long axis is 0.15 nm and the rotation per residue, 100 |
| Pauling-Corey helix | The helical (commonly right-handed) form present in many proteins, deduced by Pauling and Corey from X-ray diffraction studies of proteins such as alpha-keratin; the helix is stabilised by hydrogen bonds between, e.g., ==C==O and HN== groups (symbolised by the centre dot in ==CO-HN==) of different eupeptide bonds. In a true a helix, there are 3.6 amino acid residues per turn of the helix. Synonym: 3.613 helix, Pauling-Corey helix. Collagen helix, an extended left-handed helix resulting from the high levels of glycine, l-proline, and l-hydroxyproline present in the collagens. There are 3.3 amino acids per turn of the helix. Three of those left-handed helices form a triple superhelix that is right-handed. (05 Mar 2000) |
| groove of crus of the helix | A transverse fissure on the cranial surface of the auricle corresponding to the crus of the helix. Synonym: sulcus cruris helicis. (05 Mar 2000) |
| pi helix | A rare right-handed helix found only in small portions of certain proteins. Stabilised by similar hydrogen bonds as in an a helix; there are 4.3 amino acid residues per turn of the helix. (05 Mar 2000) |
| Watson-Crick helix | The helical structure assumed by two strands of deoxyribonucleic acid, held together throughout their length by hydrogen bonds between bases on opposite strands, referred to as Watson-Crick base pairing. See: base pair. Synonym: DNA helix, double helix, twin helix. (05 Mar 2000) |
| muscle of notch of helix | An occasional muscle on the cranial surface of the auricle spanning the antitragohelicine fissure. Synonym: musculus incisurae helicis, musculus intertragicus. (05 Mar 2000) |
| crus of helix | A transverse ridge continuing backward from the helix of the auricle, dividing the concha into an upper portion (cymba) and a lower portion (cavity of concha). Synonym: crus helicis, crista helicis, limb of helix. (05 Mar 2000) |
| helix | <chemistry, molecular biology> A spiral structure in a macromolecule that contains a repeating pattern. (09 Oct 1997) |
| helix-coil transition | <molecular biology> A change in the structure of a nucleic acid or protein molecule from a highly ordered, complex structure to a random, chaotic structure. Also means that the protein or nucleic acid becomes denatured. (09 Oct 1997) |
| helix destabilising protein | <molecular biology, protein> Proteins involved in DNA replication. They bind cooperatively to single stranded areas of a DNA molecule in a double helix, causing the helix to unwind and preventing the reformation of the duplex and extending the DNA backbone, thus making the exposed bases more accessible for base pairing. (10 Oct 1997) |
| helix (snails) | A genus of chiefly eurasian and african land snails including the principal edible snails as well as several pests of cultivated plants. (12 Dec 1998) |