What is the reason that the protein added to the buffer cooks without precipitation, but the next day when the sample is removed and spiked, precipitation appears? What should be done?

The precipitation in the denatured protein buffer may be related to the ion concentration in the protein sample. If the precipitation occurs during the temperature change, it can be dissolved by incubation in a water bath at 37℃ or below. If there is still a small amount of precipitate that cannot be dissolved the supernatant can be centrifuged and used.