The molecular weight of a protein varies immensely depending on its specific amino acid sequence, length, and structural complexity, typically measured in Daltons or kilodaltons. Small peptides or individual protein domains might weigh only a few thousand Daltons (a few kilodaltons), whereas massive multi-subunit protein complexes, such as ribosomes or giant structural proteins like titin, can reach hundreds of thousands or even millions of Daltons. Scientists determine these values precisely using analytical techniques like mass spectrometry, size-exclusion chromatography, or by calculating the sum of the atomic masses of all constituent atoms encoded by the messenger RNA sequence.