Photophysical Properties of Indotricarbocianine Dyes when Complexed with the Lipid Transfer Protein Ns-LTP1

Abstract

The paper presents the results of studies of the interaction of indotricarbocyanine dyes with the lipid transfer protein Ns-LTP1 in Dulbecco’s phosphate-buffered saline (PBS). It has been shown that the orthophenylene bridge with chlorine in the meso position of the dye is not effective as a linker for protein macromolecules that do not have a free cysteine residue. To obtain a complex of indotricarbocyanine dye with the Ns-LTP1 protein, the indotricarbocyanine dye has been modified into N-hydroxysuccinimide ester. As a result of mixing in a two-phase system – the protein in PBS and the activated dye ester in 1,2-dichloroethane – a complex of dye molecules with the Ns-LTP1 protein has been obtained. Upon formation of the complex, an increase in the half-width of the absorption spectrum from 56 to 61 nm, an increase in fluorescence decay time from 0.3 to 0.5 ns, and an increase in its degree of polarization from 27 to 31% are observed. It has been established that hydrochloric acid at concentrations being equivalent to its content in gastric juice (0.1–0.5%) leads to irreversible destruction of the dye. When treating erosive and ulcerative lesions with oral administration of the complex, capsules that can withstand stomach acid and dissolve in the intestines can be used.