| isoelectric zone | The range of H-ion concentration (pH) over which isoelectric precipitation occurs. (05 Mar 2000) |
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| isoelectric | Of equal electrical potential. Compare: isoelectric point. Synonym: isopotential. Isoelectric focusing, electrophoresis of small molecules or macromolecules in a pH gradient. (05 Mar 2000) |
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| isoelectric focusing | <technique> Electrophoresis in a stabilised pH gradient. High resolution method for separating molecules, especially proteins, that carry both positive and negative charges. Molecules migrate to the pH corresponding to their isoelectric point. The gradient is produced by electrophoresis of amphiphiles, heterogenous molecules giving a continuum of isoelectric points. Resolution is determined by the number of amphiphile species and the evenness of distribution of their isoelectric points. (18 Nov 1997) |
| isoelectric line | The baseline of the electrocardiogram. (05 Mar 2000) |
| isoelectric period | The period occurring in the electrocardiogram between the end of the S wave and the beginning of the T wave during which electrical forces are acting in directions such as to neutralise each other so that there is no difference in potential under the two electrodes. (05 Mar 2000) |
| isoelectric point | <biochemistry> The pH at which a protein carries no net charge. Below the isoelectric point proteins carry a net positive charge, above it a net negative charge. Due to a preponderance of weakly acid residues in almost all proteins, they are nearly all negatively charged at neutral pH. The isoelectric point is of significance in protein purification because it is the pH at which solubility is often minimal and at which mobility in an electrofocusing system is zero (and therefore the point at which the protein will accumulate). (18 Nov 1997) |
| androgenic zone | A transient adrenocortical zone present in some rodents at birth, most notably in mice, situated between the zona reticularis and the adrenal medulla; it degenerates in males with the secretion at puberty and in females during their first pregnancy; it slowly enlarges in unmated females after puberty and does not degenerate until middle age; the X zone appears to secrete no hormone. Synonym: androgenic zone. Misnomer for the foetal adrenal cortex of primates. Synonym: foetal reticularis. (05 Mar 2000) |
| arcuate zone | The inner third of the basilar membrane of the cochlear duct extending from the tympanic lip of the osseous spiral lamina to the outer pillar cell of the spiral organ (of Corti). Synonym: zona arcuata, zona tecta. (05 Mar 2000) |
| Barnes' zone | The lower fourth of the pregnant uterus, attachment of the placenta to any part of which may cause dangerous haemorrhage. Synonym: cervical zone. (05 Mar 2000) |
| buffer zone | <ecology> An area of land separating two distinct land uses that acts to soften or mitigate the effects of one land use on the other. (09 Oct 1997) |
| capillary zone electrophoresis | A method for separating molecules extremely rapidly based on their electrophoretic mobility. (05 Mar 2000) |
| vascular zone | An area in the external acoustic meatus where a number of minute blood vessels enter from the mastoid bone. Synonym: spongy spot, zona vasculosa. (05 Mar 2000) |
| mantle zone | A layer of small B lymphocytes surrounding the paler-staining germinal centres of lymphoid follicles. (05 Mar 2000) |
| Marchant's zone | The area on the sphenoid and occipital bones at the base of the skull from which the dura mater is readily detached. (05 Mar 2000) |
| marginal zone | The outer, nonnuclear layer of the embryonic neural tube; into its fibrous network grow the longitudinal nerve fibres which eventually become the white matter of the cord and brain stem. Synonym: marginal zone. (05 Mar 2000) |
| vermilion zone | The red margin of the upper and lower lip that commences at the exterior edge of the intraoral labial mucosa ("moist line") and extends outward, terminating at the extraoral labial cutaneous junction; a thinly keratinised type of stratified squamous epithelium deeply penetrated by well-vascularised dermal papillae which show through the translucent epidermis to impart the typical red appearance of the lips. Synonym: vermilion zone, vermilion transitional zone. (05 Mar 2000) |