| 释义 |
isoelectric, a.|aɪsəʊɪˈlɛktrɪk|
[f. iso- + electric a.]
1. Equal in electrical potential; containing or indicating no potential difference.
1877Rosenthal Muscles & Nerves 179 On the outside of the cylinder these iso-electric surfaces are exposed. 1901J. H. Raymond Human Physiol. (ed. 2) 445 A normal muscle in a condition of rest is iso-electric—i.e., it is ‘equally electric throughout, and hence has no electric current’; the same is true of dead muscle. 1940Scherf & Boyd Clin. Electrocardiogr. 2 The two waves are separated from each other by a short isoelectric line. 1972T. P. Forde in R. G. Sanderson Cardiac Patient iv. 149 The electrocardiographic tracing is flat or isoelectric during this event.
2. (Composed of particles) having no net electric charge; equal as regards electric charge; chiefly in isoelectric point, the point (usually pH value) at which an amphoteric molecule or a colloidal particle is electrically neutral in a solution.
1900W. B. Hardy in Proc. R. Soc. LXVI. 112 It is clear that there exists some point at which the particles and the fluid in which they are immersed are iso-electric. This iso-electric point is found to be one of great importance. As it is neared, the stability of the hydrosol diminishes until, at the iso-electric point, it vanishes, and coagulation or precipitation occurs. 1922J. Loeb Proteins & Theory Colloidal Behavior i. 6 The conception of the ‘isoelectric point’ of proteins was introduced before its chemical meaning was recognized and it attracted attention because it was connected with the precipitation of colloids. Ibid. iv. 42 When an acid, e.g., HCl, is added to isoelectric gelatin (or any other isoelectric protein), an equilibrium is established between free HCl, protein chloride, and non-ionogenic (or isoelectric) protein. 1946P. H. Mitchell Textbk. Biochem. iv. 107 Crystallization of a protein is usually carried out at its isoelectric point. 1958Packer & Vaughan Mod. Approach Org. Chem. xiii. 433 In a solution at the isoelectric point, amino acid molecules will not migrate in the electric field created by the introduction of a cathode and an anode. 1966Acta Chem. Scand. XX. 821 The peptides isoelectric between pH 5·0 and 6·5 proved to possess poor carrier ampholyte properties.
b. Carried out or occurring at the isoelectric point.
1961Acta Chem. Scand. XV. 326 Isoelectric analysis and fractionation by electric transport is based on sending a direct current through a system of electrolytes such that the pH increases gradually from anode to cathode... Proteins and other ampholytes will..collect in a region where the local pH is identical with the isoelectric point of the ampholyte. 1971European Jrnl. Biochem. XXI. 110/1 One might expect the ‘isoelectric coagulation’..to represent a polymerization reaction based on unaltered native molecules.
Hence isoeˈlectrically adv. Biochem., by making use of the different isoelectric points of the components of a mixture (in order to separate them).
1966Acta Chem. Scand. XX. 834 Viruses with an average molecular weight of 20 × 106 can be expected to be isoelectrically resolvable only about three times more effectively than myoglobins. 1970Zeitschr. Klin. Chem. Klin. Biochem. VIII. 383 Iron-free transferrin was separated isoelectrically into 2 components with isoelectric points at pH 5·8 and 5·4.
Add:[2.] [b.] isoelectric focusing, electrophoresis in which the resolving power is increased by maintaining a pH gradient between the electrodes.
1966Acta Chem. Scand. XX. 823 Two very similar proteins can be completely resolved by isoelectric focusing. 1982R. M. Schultz in T. M. Devlin Textbk. Biochem. ii. 46 (caption) Isoelectric focusing on polyacrylamide slab gels with ampholyte gradient between pH 6.0–8.0 of normal..and abnormal human hemoglobins. |