TABLE 7

Sample Processing and Storage Tips for Protein and Lipids

ParameterProteinsLipids
Source of material• Proteins should be extracted from fresh or snap frozen material at –70°C or below184,210,234• Lipids should be extracted from fresh or snap frozen material at –20°C108 or –80°C223,287
Time to freeze• Freeze immediately after isolation. Samples derived postmortem should be frozen (at –80°C) short after death (maximum 2 h) for optimal results in protein studies and to avoid protein degradation210,234• Freeze immediately after isolation. Samples derived postmortem should be frozen (at –20°C to –80°C) shortly after death (maximum 6–8 h) for optimal results in lipids studies108
Extraction protocol• General buffer for protein extraction and/or homogenization can be used with fresh or frozen samples233,234,265,267• Lipids can be extracted with the method of Folch et al108,223,288
• Lipid extracts are dried in a vacuum evaporator at ≤40°C and dissolved in solvent for later analysis or storage108
Tissue fixation and preservation• For optimal preservation, formalin-fixed, paraffin-embedded tissue should be stored as a block24• After extraction, lipids extracts are dissolved in solvent for storage108
Storage• Protein can be preserved for several years for proteomics if samples are stored at –80°C or below24,184• Lipids can be successfully preserved for several years if stored at –80°C or below24,184,287
• Paraffin blocks should be stored at temperatures below 27°C in an area with pest and humidity controls24
Freeze/thaw steps• Unnecessary thawing/refreezing of solid tissues or isolated biomolecules should be avoided24• Unnecessary thawing and refreezing of frozen biospecimens or frozen samples of biomolecules extracted from the biospecimens should be avoided24
Detection technique• When IHC is used to detect proteins in solid tissues, antigen retrieval may be required to unveil proteins225• TLC and a specific solvent system are used to separate individual lipid classes222
• Phosphorous assay is used to measure concentrations of phospholipids223
  • IHC, immunohistochemistry; TLC, thin-layer chromatography.