Direct proteome profiling of human blood serum in an experiment with five-day immersion

In this study we examined alterations in proteome of blood plasma of healthy persons induced by dry immersion. We studied blood plasma from 14 19- to 26-year-old healthy men sampled 7 and 2 days prior to the start, days 2, 3, and 5 of, and 1, 3, 7, and 15 days after the end of the experiment. Prior to direct MALDI-TOF spectrometric profiling, serum samples were fractionated and enriched using the MB WCX magnetic beads with a WCX low kationic exchanger performed using a ClinProt robot (Bruker Daltonics). In each spectrum, we detected 175 MS peaks on average in a weight range of 1000–17000 Da with a signal-to-noise ratio of 5. We found significant differences in 48 peaks, i.e. 27.4% of all peaks of the proteome profile, between the immersion conditions and baseline according to Student’s t test ( p < 0.05). On days 2 and 3 of the experiment, we revealed increased areas of the peaks of several proteins, including complements C3 and C4 systems, high-molecular-weight kininogen, and fibrinogen, which may be explained by adaptation of the body to the experimental conditions. On day 1 of the recovery period, significant increases in the peak areas of apolipoprotein CI, a truncated form without threonine and proline, fragments of complement C4 system, and fibrinogen were observed, which was probably related to the changes in motor activity of the subjects.