Extended Stokes shift in fluorescent proteins: chromophore-protein interactions in a near-infrared TagRFP675 variant.

Most GFP-like fluorescent proteins exhibit small Stokes shifts (10-45 nm) due to rigidity of the chromophore environment that excludes non-fluorescent relaxation to a ground state. An unusual near-infrared derivative of the red fluorescent protein mKate, named TagRFP675, exhibits the Stokes shift, which is 30 nm extended comparing to that of the parental protein. In physiological conditions, TagRFP675 absorbs at 598 nm and emits at 675 nm that makes it the most red-shifted protein of the GFP-like protein family. In addition, its emission maximum strongly depends on the excitation wavelength. Structures of TagRFP675 revealed the common DsRed-like chromophore, which, however, interacts with the protein matrix via an extensive network of hydrogen bonds capable of large flexibility. Based on the spectroscopic, biochemical, and structural analysis we suggest that the rearrangement of the hydrogen bond interactions between the chromophore and the protein matrix is responsible for the TagRFP675 spectral properties.

Synthesis and molecular properties of donor-pi-spacer-acceptor ynamides with up to four conjugated alkyne units.

A set of push-pull ynamides with up to four conjugated triple bonds has been synthesized and the molecular properties of these new carbon rods have been characterised showing effective intramolecular charge transfers and high values for the change of the electrical dipole moment after transition from the ground to the Franck-Condon excited state.

The feasibility of prostate cancer detection by triple spectroscopy.

OBJECTIVES: To determine the feasibility of ex situ prostate cancer detection by triple spectroscopy. A positive surgical margin following radical prostatectomy is an adverse factor for recurrence-free survival. Detection of residual cancer cells in vivo would be the most useful, allowing the resection of such tissue during the procedure. Aside from the use of frozen sections, the ability to detect positive surgical margins is limited. Laser-induced autofluorescence, white-light remission, and high-frequency impedance spectroscopy are methods that allow discrimination of tissues of different dignities based on their specific signature. We tested whether the combination of these techniques can differentiate malignant and benign prostate tissue ex vivo. MATERIALS AND METHODS: In preparation for future in vivo measurements, an ex vivo study was performed to detect characteristics of prostate tissue. Ninety-five tissue samples from 32 patients undergoing radical prostatectomy for clinically localized prostate cancer were taken immediately after removal of the prostate and stored in liquid nitrogen. Tissue samples were thawed for laser-induced autofluorescence, white-light remission, and high-frequency impedance spectroscopy. Based on these results, a computerized algorithm was developed for tissue differentiation. RESULTS: The statistical analysis of laser-induced autofluorescence and white-light remission data demonstrated a differentiation of benign and malignant prostate tissue with a sensitivity of 87.5% and a specificity of 87.3%. By adding the acquired high-frequency impedance data to the statistical analysis, sensitivity and specificity were increased to 93.8% and 92.4%. CONCLUSION: A highly accurate differentiation of prostate tissue was achieved in an ex vivo model. In vivo studies need to be performed to evaluate whether this technique can be successful in an intraoperative setting to detect positive surgical margins.