Teal fluorescent protein 1

A bright cyan-green fluorescent protein was isolated from Clavu-laria coral [86]. Since one of the intermediates displayed fast bleaching, a screen for more photostable variants was performed. The optimized monomeric variant was named teal fluorescent protein 1 (mTFPl). It has an excitation and emission maximum at 462 and 492 nm, respectively, so this protein is spectrally located in between CFP and GFP. With an extinction coefficient of 64,000 M 1 cm-1 and a quantum yield of 0.85 mTFPl is a very bright fluorescent protein. 

Teale, F.W.J. (1960). The ultraviolet fluorescence of proteins in neutral solution. The Biochemical Journal, 76, 381-388. 

It is the aromatic amino acid side-chains that give proteins their fluorescent characteristics. If these aromatic groups are damaged, the fluorescence is modified. However, phenylalanine fluorescence is not observed in the presence of other aromatic groups and tyrosine fluorescence is detected only in the absence of tryptophan (Teale, 1960). Even in proteins containing high relative proportions of tyrosine to tryptophan, the fluorescence of the former is masked. 

Model compound and difference spectral studies have been carried out on tyrosine and related compounds by Wetlaufer (1956), Laskowski (1957), Edelhoch (1958), Chervenka (1959), Bigelow and Geschwind (1960), Yanari and Bovey (1960), and Foss (1961) (see also Section VI,Z)). Studies of the fluorescence of tyrosine—activation spectrum, fluorescence emission spectrum, and quantum yield—have been reported by Teale and Weber (1957). The pH-dependence of the fluorescence of tyrosine and related compounds was studied by White (1959) fluorescence-polarization studies from the same laboratory were reported by Weber (1960a) for simple compounds, and for proteins (Weber, 1960b). Teale (1960) has carried out extensive studies on the fluorescence characteristics of a score of proteins. 

Because the 2570 A band of phenylalanine is weak, it is often obscured in proteins by the much stronger tyrosine and tryptophan absorptions. It is occasionally visualized in protein spectra as ripples (fine structure) in the spectral region 2500-2700 A. These ripples can be amplified by the difference spectral technique, as is shown in Fig. 13. A typical phenylalanine difference spectrum, obtained in a comparison of the isoelectric amino acid with a solution of the same concentration at pH 1 is shown in Fig. 12. Difference spectra for phenylalanine in various solvents have been measured by Bigelow and Geschwind (1960), Yanari and Bovey (1960), and Donovan et al. (1961). Fluorescence activation and emission spectra for phenylalanine were measured by Teale and Weber (1957). 

Teale FWJ, Weber G. Ultraviolet fluorescence of proteins. Bio-chem. J. 1959 72 15. 

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