Fluorescence signatures of SARS-CoV-2 spike S1 proteins and a human ACE-2: excitation-emission maps and fluorescence lifetimes

Abstract

Fast and reliable detection of infectious virus loads of the SARS CoV-2 virus is still an important issue even after more than one year of the pandemic's outbreak. The spike protein's S1 subunit (including its receptor-binding domain) and human angiotensin-converting enzyme 2 (hACE2) are known as key players in the reproduction mechanism of the SARS CoV-2 virus. Because of its high sensitivity and simple application, fluorescence spectroscopy is promising to meet the sensitivity requirements for a virus detection in a clean environment. In such highly complex protein systems, a comprehensive knowledge of fluorescence data is presumed in order to evaluate the specificity of the spectra with respect to a possible detection. This includes full featured information on the fluorescence process, i. e. wavelength and time-dependent data. In this work, fluorescence spectral excitation-emission maps of the involved proteins are presented, namely the S1 part of the spike protein and its receptor-binding domain as well as the hACE2 enzyme. In addition, measurements of fluorescence lifetimes of the proteins are presented and analyzed by a bi-exponential kinetic approach.