| incisal point | The point located between the incisal edges of the lower central incisors; the graphic projection of the excursions of the incisal point in certain planes is generally used to illustrate the envelope of motion of mandibular movement. (05 Mar 2000) |
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| 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) |
| isoionic point | The pH at which a zwitterion has an equal number of positive and negative charges; in water and in the absence of other solutes, this is the isoelectric point. (05 Mar 2000) |
| isosbestic point | <physics> In applied spectroscopy, a wavelength at which absorbance of two substances, one of which can be converted into the other, is the same. (05 Mar 2000) |
| occipital point | The most prominent posterior point on the occipital bone above the inion. (05 Mar 2000) |
| o-point | <physics> Place where the poloidal magnetic field vanishes in such a way that the nearby flux surfaces are elliptical, for example on the magnetic axis or at the centre of a magnetic island. (See also X-Point.) (09 Oct 1997) |
| end point | <chemistry> It is the completion point during a titration reaction where there are equal amounts of titrant and whatever is being titrated. It is usually evident by the first perceptible alteration of the colour of an added indicator. <immunology> It is the most dilute an antibody or antiserum solution can be while still detectably reacting with the antigen. <statistics> A category of data used to compare the outcome in different arms of a clinical trial. Common endpoints are severe toxicity, disease progression or fall in such surrogate markers as CD4 count, but sometimes death is used as an endpoint. (08 Mar 2000) |
| end-point measurement | Analytical measurement at the end of a chemical reaction, as opposed to making the measurement while the reaction proceeds. (05 Mar 2000) |
| end-point nystagmus | A jerky, physiologic nystagmus occurring in a normal individual when attempts are made to fixate a point at the limits of the field of fixation. Synonym: deviational nystagmus. (05 Mar 2000) |
| trigger point | A specific point or area where, if stimulated by touch, pain, or pressure, a painful response will be induced. Synonym: dolorogenic zone, trigger area, trigger zone. (05 Mar 2000) |
| triple point | The temperature at which all three phases (i.e., solid, liquid, and gas) are in equilibrium; the triple point of water (273.16 K) is a fundamental fixed point in temperature scales. (05 Mar 2000) |
| equivalence point | In a precipitin reaction, the zone in which neither antibody nor antigen is in excess. See: precipitation. Synonym: equivalence point. (05 Mar 2000) |
| Trousseau's point | A painful point, in neuralgia, at the spinous process of the vertebra below which arises the offending nerve. Synonym: apophysary point, apophysial point. (05 Mar 2000) |
| exclamation point hair | <clinical sign> The type of dystrophic anagen hair found at margins of patches of alopecia areata. The bulb is absent. (21 Jun 2000) |
| J point | The point marking the end of the QRS complex and the beginning of the S or T wave in the electrocardiogram. Synonym: ST junction. (05 Mar 2000) |