When preparing gels or Western blot images for scientific publication, which adjustments to the image are considered appropriate? In this article we outline the image processing best practices for presenting images with integrity and how to avoid accidental image manipulation. What will you achieve?
You should know that “editing” your gel or Western blot images in our image analysis software will never alter the data retrieved by the scanner or CCD camera system.
All material in this document has been written by collating information from various sources including scientific publication websites. We have assembled a bibliography of further reading and where possible sources have been cited. Always research specific journal guidelines prior to data submission.
Adjusting contrast and brightness of an image is usually acceptable if it is done to the entire image and in moderation. Over-adjusting the contrast to an image could mean the removal of the entire background or could mean the removal of faint bands and spots. This may raise suspicions from readers and editors. A gray background in an image is a desired feature (1) as this is usually considered an authentic image.
Data should be clearly presented and concise, but not at the expense of important information. Let’s celebrate real data — wrinkles, warts and all.” (2)
Deleting bands, adding a band, deleting background artefacts, splicing lanes together are all considered a form of misrepresentation. You should avoid this. Even if the intention was to focus the attention of the reader on “important” data, this can unintentionally mislead the reader.
Adjusting the size of your images to greater than it was captured at can cause the software program to perform interpolation (to guess what the pixels contain) and may add artefacts that weren’t present in the original data. Enlarging an image size in pixels does not increase the spatial resolution.
Decreasing an image size reduces the spatial resolution, however this should only be done by the power of two. Changing the image size should only be considered once, any more than that can introduce artefacts.
When cropping an image you should make an effort to avoid observer bias. It is usually acceptable to crop an image for the reasons below:
A non-exhaustive list of image submission guidelines for journals. Always check the instructions of the scientific journal guidelines prior to data submission.
Images (gels, micrograph photographs, etc.) should be scanned or captured at the highest resolution possible and saved in TIFF format. Always check default settings on imagers, scanners, and cameras; 300 dpi at print size is the lowest acceptable resolution for original images. Screenshots should never be used to capture images. If image file size is a concern, use only lossless image compression such as LZW; do not save images as JPEGs.
Molecular weights and fragment sizes: Protein molecular weights or DNA marker sizes must be indicated in all figure panels showing gel electrophoresis.
Full Text: http://jcb.rupress.org/fig-vid-guidelines
(Obtained September 2018)
All photographic images must be supplied at a minimum of 300 dpi at the maximum size they can be used.
Positive and negative controls, as well as molecular size markers, should be included on each gel and blot—either in the main figure or an expanded data supplementary figure.
Full Text Here: https://www.nature.com/aj/artworkguidelines.pdf
TIFF (or JPG): Colour or grayscale photographs (halftones): always use a minimum of 300 dpi.
(Obtained September 2018)
(2) Nature Cell Biology Editorial. (2006a). Appreciating data: warts, wrinkles and all. Nature Cell Biology, 8(3), 203–203. doi:10.1038/ncb0306-203a.