IMAGE CONVERSION OF ϭ- AND π-COMPONENTS OF RADIATION OF RELATIVISTIC ELECTRON AND METROLOGICAL CHARACTERISTICS OF THE PHOTON FLUX IN THE SYNCHROTRON RADIATION OUTLET

The paper deals with the efficiency of the capture of a photon flux of the synchrotron radiation (SR) σ- and π-components by the optical window in the SR quantum extraction channel of the NESTOR generator. It also anal-yses the dependence between the capture quality and different radiation wavelengths. Consideration has been giv-en to the beam size effect on the shape and dimensions of the angular distribution of the photon flux. A model has been constructed to describe the optical imaging in the registration plane. Expressions are given for estimating the efficiency of the capture of SR quanta into the optical window of the extraction channel. The factors that exert influence on the efficiency of capturing through the window are analyzed. Examples of numerical calculations are provided for formation of the final SR spectral density of the 225 MeV relativistic electrons at the output of the optical channel. The dimensions of the optical window have been determined, which ensure the reliable registration of the total flux of SR quanta for the chosen spectral range of SR quanta wavelengths.

Circularly Permuted Far-Red Fluorescent Proteins

The color palette of genetically encoded fluorescent protein indicators (GEFPIs) has expanded rapidly in recent years. GEFPIs with excitation and emission within the “optical window” above 600 nm are expected to be superior in many aspects, such as enhanced tissue penetration, reduced autofluorescence and scattering, and lower phototoxicity. Circular permutation of fluorescent proteins (FPs) is often the first step in the process of developing single-FP-based GEFPIs. This study explored the tolerance of two far-red FPs, mMaroon1 and mCarmine, towards circular permutation. Several initial constructs were built according to previously reported circularly permuted topologies for other FP analogs. Mutagenesis was then performed on these constructs and screened for fluorescent variants. As a result, five circularly permuted far-red FPs (cpFrFPs) with excitation and emission maxima longer than 600 nm were identified. Some displayed appreciable brightness and efficient chromophore maturation. These cpFrFPs variants could be intriguing starting points to further engineer far-red GEFPIs for in vivo tissue imaging.