Sulfate Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Sulfate and links to relevant pages within the course.
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| False Negative Results False negative bilirubin dipstick results are often due to testing a specimen that is not fresh. Bilirubin breaks down when exposed to light. Indoxyl sulfate (Indican) can produce a yellow orange-to-red color response which may interfere with the interpretation of a positive or negative reaction. Positive nitrites due to a urinary tract infection may also cause a false negative result. | View Page |
| Sulfosalicylic Acid Test (Exton's Modification) There are several acids which can be used to precipitate proteins - sulfosalicylic, trichloroacetic, nitric, and acetic acids. Sulfosalicylic acid (SSA) is the most frequently used acid test because it does not require the use of heat. Exton’s reagent is 5% sulfosalicylic acid in a solution of sodium sulfate. Exton (1925) found that adding sodium sulfate to the SSA causes a more uniform precipitate to be formed. To perform the SSA procedure mix equal parts of patient urine and the reagent. Rate the amount of turbidity according to the following scale: | View Page |
| Alternate Tests for Sugars There are two basic types of tests that are used to screen or monitor glycosuria -- copper reduction tests and enzyme tests. Most enzyme tests use the enzyme glucose oxidase impregnated on a dipstick along with a chromagen, and are specific for detecting only glucose. The copper reduction tests, however, detect any reducing substance. Clinitest® uses the classic Benedict’s copper reduction reaction. Any reducing substances present in the urine will react with the copper sulfate reagent, and the blue cupric sulfate is subsequently reduced to cuprous oxide. The resultant color change from blue through green to orange is proportional to the amount of reducing substance in the urine sample. | View Page |
| Denaturing Polyacrylamide Gels Denaturing chemicals can be added to the acrylamides during formation of polyacrylamide gels. These additives keep the solutes or molecules in a denatured state during separation. Urea denatures double-stranded DNA to single-stranded DNA. A detergent, sodium dodecyl sulfate (SDS), denatures proteins. Adding SDS with heat denatures proteins to small, similar shaped particles and coats each so that protein structures are not reformed. SDS is usually added to the gel and the protein sample. Then the mixture of protein coated fragments moves through polyacrylamide gel pores with speed similar to a mixture of DNA fragments. | 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 |
| Sodium dodecyl sulfate is added to polyacrylamide gels to denature the proteins in the sample and enhance their separation. | View Page |