65kDa

65kDa denotes a molecular mass of approximately 65,000 daltons and is commonly used to describe the size of proteins or protein complexes. The label is a practical convention in biochemistry and molecular biology, helping researchers communicate about the approximate heft of a polypeptide rather than its exact mass.

Molecular weight in this range is typically estimated from electrophoretic mobility in SDS-PAGE or gel filtration and can be refined by mass spectrometry. While SDS-PAGE provides a useful size estimate, it is not exact because proteins migrate based on shape and charge as well as mass. Mass spectrometry or precise analytical methods give more accurate molecular weights. Post-translational modifications, processing, cleavage, or signal peptides can alter the actual mass, so a protein may be observed near 65 kDa but differ by several kilodaltons.

The 65 kDa figure also relates to the typical number of amino acids in a protein. With an average residue mass of about 110 Da, a 65 kDa protein roughly contains around 590 amino acids, though the exact length depends on composition. Variations due to sequence, domains, or processing can shift the true size.

In naming and literature, “65 kDa” often appears as a descriptor in place of a precise mass, and proteins with this approximate size may be referred to by a nominal 65 kDa designation. An example is the 65 kDa heat shock protein (Hsp65) found in certain bacteria, used in research and diagnostics. Overall, 65 kDa serves as a convenient, approximate size label rather than a strict, universal measure.