Characterisation of FXTAS related isolated intranuclear protein inclusions using laser tweezers raman spectroscopy

We report the analysis of the vibrational modes of intranuclear protein inclusions isolated from the brain of human subjects with the Fragile X-associated tremor/ataxia syndrome (FXTAS). In this preliminary study, Raman spectra of optically trapped inclusions were measured and analysed to determine protein composition and structure. Our main findings are as follows:(1) ThespectraofproteininclusionsarecharacteristicofH2AandH2Bhistones, whichcorrelatewithpreviousmassspectrometry (MS) studies; (2) Tyrosine is present in its OH form and exposed at the protein surface; (3) Zn and to a lesser extent Cu bound to histidine side chains are detected in the inclusions; (4) The tryptophan side-chain torsion angle is calculated to be 102° (5) Several potential spectroscopic markers for the inclusions of FXTAS are identified. Theseresults show the capability of using laser tweezers Raman spectroscopy to identify protein inclusions in a non-perturbative way and to gain further insight into the pathogenesis and progression of FXTAS in human subjects and in experimental models of this disorder.