Vibrational circular dichroism of adenosine crystals

Vibrational circular dichroism (VCD) spectra of adenosine crystals exhibit few-orders-of-magnitude signal enhancement originating from long-range coupling of vibrations due to highly ordered supramolecular arrangement of the molecules in crystals. In contrast, infrared absorption (IR) spectra of adenosine crystals demonstrate unusually low intensity of the signal. An atypical negative feature in the IR spectrum denoted by an asterisk is connected with sample scattering and unique combination of sample and solvent refractive properties. [Display omitted] •The first VCD study of adenosine microcrystals is presented.•Regular packing of adenosine in crystals leads to enhanced supramolecular VCD signal.•VCD spectra with high signal-to-noise ratio can be recorded within minutes.•Unusually weak IR absorption of adenosine crystals is observed.•Adenosine microcrystals do not imbibe atmospheric water for at least two months. Adenosine is one of the building blocks of nucleic acids and other biologically important molecules. Spectroscopic methods have been among the most utilized techniques to study adenosine and its derivatives. However, most of them deal with adenosine in solution. Here, we present the first vibrational circular dichroism (VCD) spectroscopic study of adenosine crystals in solid state. Highly regular arrangement of adenosine molecules in a crystal resulted in a strongly enhanced supramolecular VCD signal originating from long-range coupling of vibrations. The data suggested that adenosine crystals, in contrast to guanosine ones, do not imbibe atmospheric water. Relatively large dimensions of the adenosine crystals resulted in scattering and substantial orientational artifacts affecting the spectra. Several strategies for tackling the artifacts have been proposed and tested. Atypical features in IR absorption spectra of crystalline adenosine (e.g., extremely low absorption in mid-IR spectral range) were observed and attributed to refractive properties of adenosine crystals.