Proteinfraktioner

Proteinfraktioner, or protein fractions, are groups of proteins that share common physicochemical properties or physiological roles. In biochemistry, fractionation refers to separating a heterogeneous protein mixture into distinct fractions enriched for specific proteins or sets of proteins. The aim is to simplify analysis, purification, or functional study of individual components.

Classification of proteinfraktioner can be based on solubility, charge, size, hydrophobicity, or binding properties. Solubility-based fractionation uses salts to precipitate different proteins (salting out). Ion-exchange chromatography separates proteins by charge, while size exclusion (gel filtration) sorts them by size. Hydrophobic interaction chromatography uses changes in salt concentration to separate proteins by surface hydrophobicity, and affinity chromatography exploits specific binding interactions to capture target proteins. Functionally, fractions may be grouped by structural roles, enzymatic activity, transport capabilities, storage, or defense functions. In clinical settings, serum protein fractions—albumin and various globulin fractions (alpha, beta, gamma)—are often analyzed by electrophoresis to provide diagnostic information.

Techniques commonly used to obtain proteinfraktioner include differential and density-gradient centrifugation for cellular or subcellular fractions, precipitation methods such as ammonium sulfate for crude enrichment, and chromatographic methods (ion-exchange, size-exclusion, hydrophobic interaction, affinity). Electrophoresis and subsequent staining or mass spectrometry are used to analyze the composition, while proteomic approaches identify the proteins present in each fraction.

Applications span basic research, proteomics and functional studies, clinical diagnostics, and food science, where fractions such as milk caseins and whey proteins or plant seed storage proteins may be analyzed. Limitations include potential denaturation, partial loss of activity, co-fractionation of unrelated proteins, and the need for careful optimization to achieve desired purity and yield.