Journal: bioRxiv

Article Title: Serpin-Driven Green Camouflage and NIR Fluorescence in Frogs

doi: 10.64898/2026.02.11.704363

Figure Lengend Snippet: Fluorescence emission can be observed in various body regions, including the dorsum (A) and the ventral side of the body (B–C) , in both sleeping and active frogs (see also Supp. Video 1 ), and in purified BBS samples. Near-infrared images can be visualized either using pseudocolor palettes (A–B) or grayscale (C). BBS are concentrated in subcutaneous lymph, blood plasma, bones, and ova. NIR can be detected from inside the body using band-pass (FWHM=10 nm) and long-pass filters, revealing the distribution of BBS within the organism, and it can be observed at wavelengths as high as 1200 nm. Excitation=635 nm for (A) and 660 nm for (B–C). ab. v. = abdominal vein, en. v. = enteric vein, f. = femur, ova. = ovaries, pu. v.= pulmonary veins , sc. l. = subcutaneous lymph. (D) The NIR emission peak is modulated in vivo due to fluorescence reabsorption. Monte Carlo simulations of varying BBS concentrations in skin and lymph show that higher concentrations produce a red-shifted emission spectrum compared to pure TpBBS. This trend matches empirical results from multiple individuals, in which the emission peak shifts from 697 nm to approximately 710 nm (arrow). *- Raman peak

Article Snippet: Excitation was provided by an LED source with a 660 nm peak wavelength and a 20 nm full-width-at-half-maximum (FWHM) (Thorlabs, M660L4).

Techniques: Fluorescence, Purification, Clinical Proteomics, In Vivo