Fluorescence technology is widely used to detect proteins. However, many common visible fluorophores often result in considerable background fluorescence in the visible range. Visible fluorophores are rarely used for membrane-based protein detection because of this high background. IRDye™800, IRDye™700DX, Alexa Fluor® 680 and Cy5.5™ antibody and reagent conjugates are specifically designed for protein detection methods that use longer-wavelength, near-infrared (IR) fluorophores to visualize proteins in western blotting and other applications. IRDye™800 and IRDye™700DX fluoresce outside the range of most autofluorescence and therefore specific signal is sharply evident from any background giving the best possible signal-to-noise ratio. Detection levels in the picogram range on Western blots rival the sensitivity of chemiluminescence on film. IRDye™800 conjugates are also suitable for immunofluorescence microscopy using commercially available excitation/emission filters in the 780nm/820nm range. Dual simultaneous labeling in western blots or microscopy is achieved when IRDye™800 conjugates are used in conjunction with IRDye™700 or Cy5.5™ conjugates. IRDye™800 and IRDye™700DX conjugates provide an ultra-sensitive and convenient alternative to standard chemiluminescent protein detection methods, as well as a valuable tool for multicolor imaging. Once reacted with the membrane and dried, IRDye™800 and IRDye™700DX conjugated antibody-protein complexes are very stable, and membranes can be stored protected from light, re-washed and/or rescanned. This blocking buffer is specifically formulated to achieve superior reproducible western blotting images using this system.