Abstract: Provided herein are methods of preparing a protein sample for proteomic analysis. In exemplary embodiments, the method comprises (a) contacting a blood sample comprising proteins with a protective agent comprising an anticoagulant (AC) and an aldehyde releaser (AR), to obtain a mixture, optionally, wherein the blood sample is added to a blood collection tube (BCT) comprising the protective agent, and (b) isolating a fraction comprising proteins or a source of proteins from the mixture to yield a protein sample or a source of a protein sample, wherein steps of the method are carried out in the absence of exogenous proteolytic enzyme inhibitors, wherein the protein sample is suitable for proteomic and peptidomic analysis.

Abstract: A composition and method of use thereof wherein the composition comprises one or more components capable of releasing an aldehyde, one or more anticoagulants or chelating agents, and one or more polysaccharides. The composition has a pH of from about 4 to about 6.