| secondary structure | <molecular biology> Structures produced in polypeptide chains involving interactions between amino acids within the chain. Especially _ helical and _ pleated sheet structures. Also applies to the complex folding of nucleic acids as, for example: the clover leaf structure of tRNA. (18 Nov 1997) |
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| Holliday structure | <molecular biology> A structure which occurs during homologous recombination between homologous chromosomes. While the two chromosomes are side by side, one strand of DNA on each chromosome is broken and then attached to the broken strand of DNA on the other chromosome. The crossover point, which is called the Holliday junction, is able to slide up and down between the two chromosomes, so that a little or a lot of DNA can ultimately be switched between them. (09 Oct 1997) |
| soil structure | The combination or arrangement of primary soil particles into secondary particles, units or peds. (09 Oct 1997) |
| stem and loop structure | <molecular biology> The structure of tRNAs is so termed because it has four base paired stems and three loops (not base paired), one of which contains the anticodon. (18 Nov 1997) |
| structure | <microscopy> The mode of construction of an animate or inanimate body or system from units such as atoms, ions, molecules, cells, crystals in a fluid, plastic, or solid state. Cf. Morphology. (05 Aug 1998) |
| structure activity analysis | Study in which systematic variation in the structure of a compound is correlated with its activity, in an attempt to determine the characteristics of the (receptor) site at which it acts. (18 Nov 1997) |
| structure-activity relationship | The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups. Other factors contributing to structure-activity relationship include chemical reactivity, electronic effects, resonance, and inductive effects. (12 Dec 1998) |
| structure-functionalism | The scientific tradition that stresses the relationship between aphysical structure and its function, for example: the related disciplinesof anatomy and physiology. (09 Oct 1997) |
| structure proteins | Proteins whose role is for structure and support in tissue and within the cell; e.g., the collagens. (05 Mar 2000) |
| quarternary structure | The three-dimensional structure of a complex protein, this especially refers to the way the subunits fit together. (09 Oct 1997) |
| quaternary structure | The three-dimensional structure of a complex protein, this especially refers to the way the polypeptide subunits fit together. (09 Oct 1997) |
| tertiary structure | <biochemistry, chemistry> The third level of structural organisation in a macromolecule. The primary structure of a protein (for example) is the amino acid sequence, the secondary structure is the folding of the peptide chain (alpha helical or beta pleated), the tertiary structure is the way in which the helices or sheets are folded or arranged to give the three dimensional structure of the protein. Quaternary structure refers to the arrangement of protomers in a multimeric protein. (13 Jan 1998) |
| ecosystem structure | The physical and spatial aspects of an ecosystem that are contributed by the biotic composition. Biotic composition is generally determined by the collective physiognomy of the dominant plants, including life forms, vertical stratification, and size. (09 Oct 1997) |
| tuboreticular structure | Tubules 20-30 nm in length that lie within cisterns of smooth endoplasmic reticulum; observed in connective tissue diseases such as SLE, and in various cancers and virus infections. (05 Mar 2000) |
| fine structure | <pathology> General term to describe the level of organisation that is below the level of resolution of the light microscope. In practice, a shorthand term for structure observed using the electron microscope, although other techniques could give information about structure in the sub micrometre range. (18 Nov 1997) |