CC BY
5B-O-2
BIOMEDICAL PHOTONICS
Analytical capabilities of the intrinsic fluorescence of blood plasma proteins
for biomedical diagnostics
A. Gayer12, B. Yakimov12, E. Shirshin12
1- Faculty of Physics, M.V. LomonosovMoscow State University, 1-2Leninskie Gory, Moscow, Russia, 119991 2- World-Class Research Center "Digital Biodesign and Personalized Healthcare", Sechenov First Moscow State
Medical University, Trubetskaya 8, Moscow, Russia, 119048 Main author email address: shirshin@lid.phys.msu.ru
Since early 1960s, intrinsic fluorescence of proteins has attracted attention of researchers as a versatile diagnostic modality. It was discovered that fluorescence of tryptophan residues (Trp), the main contributor to proteins' emission, is highly sensitive to the parameters of its microenvironment. However, in general, Trp fluorescence of blood plasma exhibits low variability independent on the disease, e.g., cancer or diabetes, and its capabilities in detection of pathologies are limited. Moreover, a detailed analysis of Trp fluorescence variability in blood plasma on a large (>100 samples) dataset is lacking in the literature.
Another important phenomenon in the proteins photophysics is the influence of post-translational modifications, namely, oxidation processes, on the optical properties of the system. Having a low ionization potential, Trp can be easily oxidized, resulting in a decrease of its fluorescence and in the formation of novel fluorescent products. Trp oxidation results in the formation of fluorescence in the visible spectral range, untypical for globular proteins, as well as in an apparent "yellowing" of the sample. Oxidative modifications are accumulated through the whole protein's life span, and their fluorescence may potentially serve as a diagnostic parameter for detection of pathologies.
This work aims at the analysis of variability and analytical capabilities of proteins' intrinsic fluorescence based on the open dataset of excitation-emission matrices (EEMs) measured for 300 patients with suspected colorectal cancer described in and supporting model experiments. For the first time, we demonstrate the dominant role of HSA in the formation of blood plasma fluorescence in the visible range. Using size-exclusion chromatography of blood plasma, fluorescence properties of protein fractions are analysed in detail. We quantify "classical" descriptors such as Trp fluorescence intensity and band shape, Tyr fluorescence and the impact of fluorescent oxidation products, and then use these parameters as features to build a classification model for distinguishing between the control group and cancer patients. The obtained results provide novel information on conformational changes of blood plasma proteins as revealed by fluorescence spectroscopy as well as extend current approaches used for the analysis of blood plasma fluorescence.
ALT'22
