Nanoscale integration of sensitizing chromophores and porphyrins with bacteriophage MS2 - PubMed (original) (raw)

Nanoscale integration of sensitizing chromophores and porphyrins with bacteriophage MS2

Nicholas Stephanopoulos et al. Angew Chem Int Ed Engl. 2009.

No abstract available

Figures

Figure 1

Modification of N87C T19_p_AF MS2. a) Two mutations (N87C and T19_p_AF) were introduced into MS2 coat protein subunits. After capsid formation in E. coli, the interior and exterior surfaces were differentially modified using a multistep sequence. b) The interior of the capsid was modified at C87 (red) using either AlexaFluor 350 (1) or Oregon Green 488 (2) maleimide dyes. Up to 180 copies of each chromophore were installed. c) The exterior of the capsid was modified first via an oxidative coupling reaction to attach aldehyde 3 to the pAF19 groups (blue), and subsequently with aminooxy-containing porphyrin 4 to form stable oxime linkages. This design allows for energy transfer from the dye inside the capsid to the porphyrin on the outside via FRET.

Figure 2

Comparison of the excitation and emission spectra for the chromophores used in this study. The Alexa Fluor 350 emission overlaps with the porphyrin Soret band, while the Oregon Green 488 emission overlaps with the first porphyrin Q band, allowing for FRET.

Figure 3

UV-vis spectra of the MS2-AF-porphyrin (a) and MS2-OG-porphyrin (b) systems. The spectra are normalized at the absorbance maximum of the donor dye. c) The ratio of donors to porphyrins was calculated by comparing the absorbance ratios and using the extinction coefficients listed in Figure 2. The number of porphyrins per capsid was calculated by assuming complete dye conversion and dividing the total number of monomers (180) by the number of dyes per porphyrin.

Figure 4

Excitation spectra of the MS2-1-4 (a) and MS2-2-4 (b) conjugates. The insets show expansions of the areas of maximum donor excitation. The MS2-1-4 spectra were normalized at the porphyrin Soret band and excitation was monitored at the first porphyrin emission band at 602 nm. The MS2-2-4 spectra were normalized at the first porphyrin Q band and excitation was monitored at the second porphyrin emission band at 655 nm to minimize any residual fluorescence emission from the Oregon Green. The colors correspond to the chromophore ratios listed in Figure 3c. The slight red-shift seen at lower modification levels is possibly due to coordination of the two surface-accessible exterior lysines to the zinc center.

Figure 5

Emission spectra upon donor excitation for the MS2-1-4 (a) and the MS2-2-4 (b) systems, with emission normalized by the donor absorbance. Increased amounts of porphyrin result in greater dye quenching due to energy transfer. The insets show the emission of the porphyrin in the MS2-1-4 (c) and MS2-2-4 (d) systems, normalized at the donor emission maximum to demonstrate the relationship between donor quenching and acceptor emission. The two porphyrin emission bands at 602 and 655 nm are clearly visible.

Figure 6

Photoreduction of methyl viologen (a) by a sensitized porphyrin system with 15 min illumination at 505 nm (b) and 0.5 min illumination at 415 nm (c). The different time values were required due to the extinction coefficient differences between 2 and 4. Values represent the average and standard deviations of n = 3 measurements.

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Nanoscale integration of sensitizing chromophores and porphyrins with bacteriophage MS2 - PubMed (original) (raw)