1Kd

1Kd is most commonly used as an abbreviated form of 1 kDa, where kDa stands for kilodalton, a unit of molecular mass used in biochemistry and molecular biology. A dalton is defined as one twelfth the mass of a carbon-12 atom, and 1 kDa equals 1000 daltons, about 1.6605 x 10^-24 kilograms. The kilodalton scale is employed to describe the sizes of proteins, peptides, and other macromolecules, providing a convenient reference point for molecular weight.

In practical terms, 1 kDa roughly corresponds to a small peptide. Since the average mass of an amino acid residue is about 110 Da, a protein of 1 kDa would be expected to contain around 9 amino acids, though actual numbers vary with amino acid composition and structure. Because experimental techniques such as SDS-PAGE, gel filtration, and mass spectrometry rely on mass, 1 kDa is a useful benchmark, even though migration in gels is influenced by shape and charge in addition to mass.

If encountered as a label "1Kd" in literature or databases, it is often a typographical variant for 1 kDa rather than a distinct protein or gene. There is no widely recognized human gene, enzyme, or protein officially named “1Kd.” When precision is required, it is best to specify the exact molecular weight in kilodaltons and, if possible, reference the corresponding sequence or accession number.