Cloud Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Cloud and links to relevant pages within the course.
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| Rate of Migration The net charge of a molecule is the most important factor affecting the mobility of that molecule. The greater the net charge, the greater the mobility or the more quickly the molecule migrates. The net charge of a particular compound depends upon the buffer and the resultant pH set by that buffer. The size and shape of a molecule also influence the rate of migration in that the larger the size, the slower the molecule will move in electrophoresis.The viscosity and the pore size in the support media or gels used for electrophoresis influence the rate of migration. Increased viscosity slows the migration and increasing pore size speeds up the migration.Increased heat increases the rate of migration. Increasing the strength of the electrical field by increasing voltage and increasing the temperature used for the electrophoresis both increase the mobility and rate of migration. When increasing these factors that affect mobility, caution is necessary. Each will lead to an increase in temperature that can possibly denature the sample and alter the characteristics of the support medium. The ionic strength of the buffer and its effect on mobility are more complicated. The ionic strength of the buffer affects the thickness of the ionic cloud, the rate of migration, and the sharpness of the separated solutes. In electrophoresis, a cloud of ions forms over the medium and is composed of buffer ions, sample ions and other nonbuffer ions. Increasing the buffer ionic strength increases the buffer ions in the cloud and slows the movement of solutes and creates sharper bands. However, this also increases heat production. | View Page |
| Which one of the following will slow down the migration of solutes in electrophoresis? | View Page |
| In isoelectric focusing, the basis of separation of solutes is different than the other types of electrophoresis. Which statement below correctly describes this feature of isoelectric focusing? | View Page |
| Electroendosmosis With a pH 8.0-9.0 used for protein electrophoresis, proteins take on a negative charge, that is a negative ion cloud forms. As the negative ion cloud migrates to the anode, the proteins are pulled to the anode. Several gels used routinely for protein electrophoresis attract positive ions from the buffer and form a positive ion cloud. This ion cloud moves in the opposite direction to the cathode. This phenomenon is called electroendosmosis or endosmosis.The tension created by these oppositely moving ion clouds can affect the movement of sample macromolecules. The migration of some proteins can be slowed, some proteins can become immobile, and other proteins are pushed toward the cathode. Many protein electrophoresis methods take advantage of this tension and use it to achieve better separation of protein bands. The gamma globulin band in serum, urine, and other body fluids will separate more sharply by being pushed to the cathode and will appear behind the point of sample application. | View Page |
| Which statements below are associated with electroendosmosis? | View Page |
| Wick flow is caused by movement of the buffer ions into the medium when there has been a loss of moisture in the medium due to heat generation. | View Page |