427kilodalton

427 kilodalton (kDa) is a unit of molecular mass used in biochemistry and molecular biology to describe the size of proteins and other macromolecules. A dalton (Da) is defined as one twelfth of the mass of a carbon-12 atom, and one kilodalton equals 1,000 Da. Thus, 427 kDa corresponds to 427,000 daltons.

In terms of protein size, a 427 kDa molecule could be a large single polypeptide or a multimeric complex. Roughly, if a protein consisted of amino acids with an average mass of about 110 Da, a 427 kDa mass would correspond to around 3,800 residues; however, actual sequence composition, folding, and post-translational modifications can significantly alter the actual number of residues. Large protein complexes or assemblies can also have masses in this range, formed from multiple subunits.

Mass determination methods include mass spectrometry (electrospray or MALDI), analytical ultracentrifugation, and light scattering coupled with size-exclusion chromatography. SDS-PAGE provides rough estimates but has limited resolving power above several hundred kilodaltons, and glycosylation or other modifications can shift measured mass away from theoretical values calculated from sequence alone.

In practice, the figure 427 kDa is used to express the approximate size of sizeable proteins, enzymes, or assemblies in scientific reporting. The exact measured mass depends on oligomeric state, phosphorylation, glycosylation, and other post-translational modifications, as well as the conditions under which the measurement is made.