manually extracting the bradford assay data recorded with a smartphone

Smartphone como dispositivo analítico para cuantificar proteínas mediante el ensayo de Bradford

Regardless of the downstream use (e.g., ELISA, enzyme kinetics, western blotting, protein purification, and mass spectrometry), protein quantification is crucial for accurate analysis in life sciences laboratories. In addition to their use as secondary readouts (i.e., to calculate relative levels of analytes per mass of protein), protein levels in a sample can also be the desired output itself. For example, one can be interested in protein levels in food resources1 or in urine2. There are many methods available to measure protein concentration in samples3, including direct UV absorbance readings4, protein-copper chelation5,6, protein-dye binding colorimetric assays7, and protein-dye binding fluorescent assays8. The relevance of protein quantitation is evidenced by the presence of two papers describing protein measurement methods5,7 in the top-3 of the most cited literature9,10. Despite the fact that many authors neglect their actual citation by citing non-primary references or not citing anything at all, the original papers describing the Lowry protein assay and the Bradford protein assay amount &#62;200,000 citations each10.
The popularity of the Bradford assay stems from its affordability, simplicity, speed, and sensitivity. The assay is based on the interaction between proteins and the dye Coomassie Brilliant Blue G under acidic conditions. Under the conditions of the assay (i.e., low pH), the dye exists in three forms: a red cationic form with &#955;max at 470 nm; a green neutral form with &#955;max at 650 nm; and a blue anionic form with &#955;max at 590 nm11,12 (Figure 1). The cationic form predominates in the absence of proteins. As proteins interact with the dye, they stabilize the blue anionic form, causing a noticeable change in the color of the solution, from brownish to blue. Usually, the change in the concentration of the blue form of the dye is quantified spectrophotometrically, whose absorbance at 590-595 nm is proportional to the quantity of protein in the assay.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65547/65547fig01v2.jpg" /> 
Figure 1: Coomassie brilliant blue G absorption spectra under the conditions of the Bradford assay. The three main peaks are marked with arrows indicating the &#955;max of the red (470 nm), green (650 nm), and blue (590 nm) forms of the dye. Spectra were recorded in the absence of protein (yellow line) and in the presence of 3 &#181;g (gray line) and 10 &#181;g (blue line) of bovine serum albumin. <a href="https://www.jove.com/files/ftp_upload/65547/65547fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The widespread use of the Bradford assay has led to the identification of several limitations (e.g., variable responses to different proteins11, and interference by lipids13 and detergents7) and the development of modifications to improve its performance (e.g., the addition of detergents14,15, alkalinization14,16 and use of the ratio of absorbances17). In addition to modifications in the assay itself, the use of alternative devices, such as smartphones or cameras, to capture analytical signals have also been described18,19,20. Indeed, the development of methods that make use of smartphones as portable chemical analyzers has been an active area of research. The motivation for the use of smartphones stems from the affordability, portability, ease of use, and widespread availability of these devices.
This paper provides a protocol for protein quantification using the RGBradford assay20, which uses a smartphone as an analytical device. In contrast to the original RGBradford publication20, here, a procedure that streamlines the color extraction process has been introduced. It involves the utilization of a freely available software application to extract color information from each well of a microplate picture automatically, saving significant time and effort. This is an alternative to the previous method of manually acquiring color data from each well one by one using a graphics editor software application20. Ultimately, protein levels in samples can be quantified using color data extracted from a picture of a microplate taken with a smartphone.

Autor destacado: Un enfoque alternativo a la cuantificación de proteínas mediante el ensayo Bradford utilizando un teléfono inteligente 

RGBradford: Cuantificación de proteínas con la cámara de un teléfono inteligente

Watch this Scientific Journal Video about Manually Extracting the Bradford Assay Data Recorded with a Smartphone at JoVE.com

Manually Extracting the Bradford Assay Data Recorded with a Smartphone  

Extracción manual de los datos del ensayo Bradford registrados con un teléfono inteligente

Para extraer manualmente los datos del ensayo Bradford de las imágenes de la microplaca grabadas con la cámara del smartphone, descargue Inkscape, un editor gráfico gratuito y de código abierto. Abra Inkscape, vaya a archivo y haga clic en "abrir" para seleccionar la imagen de la microplaca tomada con el teléfono inteligente. Elija la herramienta S de selección y transformación de objetos, que se representa como una flecha en la parte superior izquierda, y haga clic en la imagen.Un borde de línea discontinua indicará la selección. A continuación, seleccione los colores de selección de la herramienta Imagen D, que se representa como un cuentagotas en el lado izquierdo. A continuación, haga clic en el centro de un pozo.El color del panel inferior, relleno, cambiará en consecuencia. Haz clic en el color y aparecerá una pestaña de relleno y trazo en el lado derecho. Cambia el menú desplegable de color plano a RGB.Registre los valores mostrados para los canales azul y verde de cada pocillo. Calcule la relación entre el azul y el verde utilizando los valores registrados.

manually-extracting-the-bradford-assay-data-recorded-with-a-smartphone

Research

JoVE Journal

Biochemistry

Manually Extracting the Bradford Assay Data Recorded with a Smartphone

161 vistas. Para extraer manualmente los datos del ensayo Bradford de las imágenes de la microplaca grabadas con la cámara del smartphone, descargue Inkscape, un editor gráfico gratuito y de código abierto. Abra Inkscape, vaya a archivo y haga clic en "abrir" para seleccionar la imagen de la microplaca tomada con el teléfono inteligente. Elija la herramienta S de selección y transformación de objetos, que se representa como una flecha en la parte superior izquierda, y haga clic en la imagen.

Video: Manually Extracting the Bradford Assay Data Recorded with a Smartphone  

RGBradford: Protein Quantitation with a Smartphone Camera

Protein quantitation is an essential procedure in life sciences research. Amongst several other methods, the Bradford assay is one of the most used. Because of its widespread, the limitations and advantages of the Bradford assay have been exhaustively reported, including several modifications of the original method to improve its performance. One of the alterations of the original method is the use of a smartphone camera as an analytical instrument. Taking advantage of the three forms of the Coomassie Brilliant Blue dye that exist in the conditions of the Bradford assay, this paper describes how to accurately quantify protein in samples using color data extracted from a single picture of a microplate. After performing the assay in a microplate, a picture is taken using a smartphone camera, and RGB color data is extracted from the picture using a free and open-source image analysis software application. Then, the ratio of blue to green intensity (in the RGB scale) of samples with unknown concentrations of protein is used to calculate the protein content based on a standard curve. No significant difference is observed between values calculated using RGB color data and those calculated using conventional absorbance data.

This paper provides a protocol for protein quantification using the Bradford assay and a smartphone as an analytical device. Protein levels in samples can be quantified using color data extracted from a picture of a microplate taken with a smartphone.

Protein quantitation is an essential procedure in life sciences research. Amongst several other methods, the Bradford assay is one of the most used. ...