**3.8 Identification of thymosin** β**<sup>4</sup>**

*Mass Spectrometry in Life Sciences and Clinical Laboratory*

Double-injection capillary electrophoresis has also been applied for the identifi-

*MALDI analysis of insulin aspart; analysis of reduced B-chain (A), MALDI-PSD analysis of tryptic B-chain* 

The nonapeptide delta DSIP was first isolated from the cerebral venous blood of rabbits in an induced state of sleep during the mid-70s [82]. It was primarily believed to be involved in sleep regulation due to its apparent ability to induce slowwave sleep in rabbits. However, it has been demonstrated that short-term treatment of chronic insomnia with DSIP is not likely to be of major therapeutic benefit [83]. The peptide is marketed illegally presumably for the treatment of insomnia. The peptide was directly exposed to the PSD analysis in order to confirm its molecular

**38**

**Figure 8.**

*(B), see Table 3.*

cation of insulin molecules [81].

**3.7 Identification of delta sleep-inducing peptide (DSIP)**

mass and amino acid sequence (**Figure 4** and **Table 1**).

Synthetic thymosin is a peptide consisting of 43 amino acids with artificial acetylation of the N-terminus (see **Figure 4** and **Table 1**). Thymosin has the potential of playing a significant role in tissue development, maintenance, repair, pathology and other important biological activities [84]. Some important biological activities of thymosin are related to the peptide sequence L17KKTET22 [85]. Illegally distributed thymosin products are claimed to promote a variety of beneficial biological functions, such as muscle building. The peptide was identified through PMF and de-novo sequencing of the tryptic peptides (**Table 4**).
