Abstract: The closed-chamber device used in the preparation of exponential gradients may also be used for the exponential dilution of samples prior to chemical or biological assay. We have prepared special sample chambers to hold 0.2 to 1 ml, and volumes of 5 to 20 ml. Our use of the method is the dilution of transforming DNA to the end point of faint positive test in bioassay. The calculated dilutions of unknown and standard provide a ratio of relative activity of the unknown. The range of dilutions obtained is described by ln CmCf = VfVm, where Cm is the concentration of solute in the closed mixing chamber, Vm is the volume contained, and Cf is the concentration of solute at the particular volume, Vf, appearing at the exit tip from the mixer. The dilutions beyond the second decade require monitoring by acid dilution or other method. For infinitesmal fraction size, a 10-fold dilution is found at 2.303 ml/ml, a 100-fold dilution at 4.606, etc. The actual dilutions are a function of sample size. If 0.10-ml samples are taken from a mixer sample of 1 ml, the calculations show a dilution of 9.8 in sample 24, and of 10.1 in sample 25. The exponential nature of the dilution has been verified by dilution of a dye or radioactive phosphate, or the dilution of an acid. The greatest use of the method is seen to be in the calibration of automation assemblies, or in bioassays, including immunoassays.
Publication Year: 1965
Publication Date: 1965-05-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 5
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