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Related Concept Videos

Washing, Drying, and Ignition of Precipitates00:52

Washing, Drying, and Ignition of Precipitates

After filtration, the precipitate is washed to remove coprecipitated impurities and any remaining mother liquor. Colloidal precipitates, such as silver chloride, are washed with an electrolyte (such as dilute nitric acid) to prevent the peptization of the precipitate. In the case of slightly soluble precipitates, the wash solution contains a common ion to reduce solubility. Lead sulfate, which is slightly soluble in water, is washed with dilute sulfuric acid. Similarly, wash solutions may be...
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Downstream processing begins once fermentation is complete and involves a series of steps to recover and purify products such as acids, vitamins, antibiotics, or proteins.Cell HarvestingFor example, for intracellular protein-based products, the first step is harvesting the cells. This is typically achieved using centrifugation or filtration to separate the cells from the liquid phase.Cell Disruption for Intracellular ProductsIf the target product is intracellular, the harvested cells must be...
Precipitation Processes01:12

Precipitation Processes

The experimental conditions in a gravimetric analysis should be optimized to maximize the particle size and purity of the obtained precipitate. Ideally, the concentration of the precipitating reagent should be low with effective stirring to maintain low relative supersaturation for the growth of large crystals. In homogeneous precipitation, the precipitant is slowly generated by a chemical reaction in the solution to avoid local reagent excesses. For example, urea decomposes gradually to...
Precipitation Gravimetry01:03

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Precipitation gravimetry is based on converting an analyte into a sparingly soluble precipitate, which is separated by filtration and weighed. An ideal precipitate should be pure, insoluble, of known composition, and easily filtered from the reaction mixture.
In determining nickel by gravimetric analysis, a precipitant of ethanolic dimethylglyoxime is added to a hot nickel salt solution. This is quickly followed by the dropwise addition of dilute ammonia solution until precipitation occurs. A...
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Polymer samples typically consist of macromolecular chains with a distribution of lengths, resulting in a range of molar masses rather than a single discrete value. Conventional descriptors such as the number-average molar mass and weight-average molar mass quantify this distribution but do not fully capture polymer behavior in solution..The viscosity-average molar mass provides a more realistic description of polymer behavior in solution because it accounts for the enhanced contribution of...
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Polymerization produces macromolecules with a range of chain lengths due to the random nature of molecular growth processes. As chains form and terminate at different stages, a single polymer sample contains molecules of varying sizes rather than a uniform structure. This variability is described using average molar masses and distribution-related parameters, which together provide a comprehensive understanding of polymer characteristics.The distribution of molar masses plays a critical role in...

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Production of E. coli-expressed Self-Assembling Protein Nanoparticles for Vaccines Requiring Trimeric Epitope Presentation
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Determination of purity and yield.

S B Mohan1

  • 1Department of Chemical Engineering, Birmingham University, Birmingham, West Midlands, UK.

Methods in Molecular Biology (Clifton, N.J.)
|March 25, 2011
PubMed
Summary

Defining protein purity and yield is complex. While absolute purity is unattainable, detecting a single band on SDS-PAGE is a common, practical criterion for assessing protein purity.

Area of Science:

  • Biochemistry
  • Protein Chemistry

Background:

  • Protein purity and yield are fundamental concepts in protein chemistry.
  • Absolute definition of these parameters is challenging due to inherent complexities.

Purpose of the Study:

  • To explore the challenges in defining absolute protein purity.
  • To highlight the practical criteria used for assessing protein purity in research.

Main Methods:

  • Discussion of various analytical techniques used to assess protein purity, including electrophoresis (SDS-PAGE), chromatography (gel filtration, HPLC, ion exchange), and spectroscopy (mass spectrometry, NMR).
  • Focus on Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) as a routine method for purity assessment.

Main Results:

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  • Absolute protein purity cannot be definitively established; rather, tests demonstrate the absence of detectable contaminants.
  • The presence of a single band on SDS-PAGE is a widely accepted practical criterion for protein purity.

    • Conclusions:

    • While absolute purity remains an ideal, practical methods like SDS-PAGE provide reliable indicators.
    • The limitations in defining absolute purity necessitate the use of established, albeit imperfect, assessment techniques.