Mtp 384 target polished steel tf

To prepare the samples for mass determination, samples which were prior desalted using C₁₈ Zip Tips (Millipore, USA) were spotted onto a MALDI target (MTP 384 target polished steel TF, Bruker Daltonics, Bremen, Germany) along with 2 μl of α-cyano-4-hydroxycinnamic acid (α-CHCA) solution (10 mg/ml) in acetonitile/water/trifluoroacetic acid (50:50:0.1). We note that the singly charged protein species is not the dominant signal, and we believe this is due to the use of CHCA matrix. MALDI measurements were performed on an ultrafleXtreme MALDI-TOF/TOF mass spectrometer equipped with a smartbeam laser (Bruker Daltonics). FlexControl (Version 3.4) was used with the following programmed measurement parameters: laser frequency of 1,000 Hz in the positive-ion linear mode with acquisition ranging from 500 to 30,000 Da as well as in positive-ion reflector mode with acquisition ranging from 400 to 6,000 Da. Final spectra consisted of 1,000-3,000 shots per analysis.

The samples of mature rigid fibril and worm‐like fibril were purified by MWCO 100 kDa cut‐off. The samples were analyzed by MALDI‐MS. 1 µL of the sample was spotted onto the MALDI target (MTP 384 target polished steel TF, Bruker Daltonics, Bremen, Germany) with 2 µL of α‐cyano‐4‐hydroxycinnamic acid (α‐CHCA) solution in acetonitrile/water/trifluoroacetic acid (50:50:0.1) for subsequent MALDI‐TOF measurements. The concentration of α‐CHCA was 10 mg mL⁻¹. MALDI measurements were performed on an ultra fleXtreme MALDI‐TOF/TOF mass spectrometer equipped with a smart beam laser (Bruker Daltonics). The measurement parameters were programmed in flexControl (Version 3.4): laser frequency of 1000 Hz in the positive linear mode with acquisition ranging from 1000 to 70 000 Da. Final spectra consisted of 1000–3000 shots per analysis. The samples were also desalted using C18Zip Tips (Millipore, USA) and analyzed as above.