mYFP

mYFP, also known as monomeric Yellow Fluorescent Protein, is a genetically encoded fluorescent marker derived from the native yellow fluorescent protein (YFP). It was engineered to be monomeric, a modification that prevents aggregation when fused to other proteins and thereby preserves native cellular functions. The monomeric form was achieved through targeted mutagenesis at key residues that promote dimerization, resulting in a single polypeptide chain that retains the chromophore architecture necessary for fluorescence.

The spectrum of mYFP peaks around 514 nm with an excitation maximum near 514 nm and an emission maximum close to 527 nm. Its quantum yield is approximately 0.40, and it can be excited by the same lasers used for green fluorescent protein, which facilitates multimodal imaging. mYFP has a pKa of about 6.5, making it relatively stable across physiological pH ranges. Photostability assays have shown that mYFP withstands prolonged illumination with minimal photobleaching, a feature that is advantageous for long-term live-cell imaging.

Applications of mYFP span cellular biology, molecular imaging, and developmental studies. Fusion constructs with mYFP enable visualization of protein localization, dynamics, and interaction partners in living cells. It is also employed as a reporter in transcriptional activity assays and as a component in Förster resonance energy transfer (FRET) pairs with cyan or green fluorescent proteins. Several commercial vendors now supply plasmids encoding mYFP or its derivatives, allowing rapid incorporation into research workflows.

While mYFP is widely used, it can exhibit degree of self-quenching at high expression levels and may be less bright than newer bright monomeric variants that incorporate additional rational mutations. Nonetheless, its robust monomeric character and compatibility with standard fluorescence microscopy make it a popular choice for many experimental protocols.