Sample concentration is a process used when protein concentration is low. Buffer solution is removed via ultrafiltration, precipitation and other methods to raise protein content and ensure sufficient loading volume. Protein denaturation refers to boiling samples at high temperature after adding Loading Buffer, which disrupts the secondary and tertiary structures of proteins, unfolds polypeptide chains and binds SDS to them. This renders all proteins negatively charged, allowing them to separate by molecular weight during electrophoresis. Both steps are critical for WB sample preparation.