# Proteomics in Forensic Analysis: Applications for Human Samples
## 3 Applications of Forensic Proteomics for Human Samples
### Hair Proteome
The authors demonstrated that this optimized strategy increased the total identified genetically variant peptides from 45 to 127, and the sensitivity of the analysis 3-fold from 11% to 34%. The optimal condition contributed to increase LRs (AFR/EUR) for African samples about \(10^{3.9}\) times. Another study showed the feasibility of extracting and determining proteins from a single hair with a length of approximately 1 mm [137]. Using the proteomic approach, 63 proteins were identified, of which 60% were keratin and keratin-associated proteins. However, no data have been presented regarding genetically variant peptides. A later study by [PERSON] et al. developed a new proteomic sample preparation procedure for a single hair (length, 25 mm),which combined heat, ultrasonication, and surfactants [38]. A total of 6519 unique peptides and 57 GVPs were identified, demonstrating the forensic application of this approach to distinguish individuals. Figure 2: Applications of human hair proteomic analysis in forensic sciences. (**a**) Weighted spectral counts for six differentially expressed proteins that were in hair samples of subjects of different ethnic origin. The ethnicities are Caucasian (CA), African–American (AA), Kenyan (KE), and Korean (KO). Figure reprinted from [36] under the terms of the Creative Commons Attribution  
License (CC BY 4.0) [[https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)]([https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)) (accessed on 3 March 2021). (**b**) Identification of individuals and differentiated biogeographic backgrounds using non-synonymous single nucleotide polymorphism (nsSNP) imputed from single amino acid polymorphisms (SAPs) in human hair proteomes. The probability of overall imputed nsSNP profiles occurring in the European or African population (Pr(profile! EUR population)) or Pr(profile! AFR population)) was calculated using imputed nsSNP alleles from individuals and multiplied together. Confidence intervals (90% CI) are estimated using parametric bootstrapping. European and African populations were differentiated by their probability of overall imputed nsSNP profiles using parametric bootstrapping. Figure reprinted from [18] under the terms of the Creative Commons Attribution License (CC BY 4.0) [[https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)]([https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)) (accessed on 3 March 2021). (**c**) The likelihood of hair samples coming from a European relative to African genetic background. The colors are for European-American subjects (red), African-American subjects (green), and Kenyan subjects (blue). Figure reprinted from [18] under the terms of the Creative Commons Attribution License (CC BY 4.0) [[https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)]([https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)) (accessed on 3 March 2021). (**d**) Hierarchical clustering dendrogram of identified genetically variant peptides (GVPs), which indicated that GVPs of hair shaft were more related to individual differences than the body site origin. Subjects are shown in different colors. Sample labels indicate hair body site origin: S = Scalp, B = Beard, P = Public, A = Axillary. Figure reprinted from [39], Copyright (2019), with permission from Elsevier. (**e**) GVP profiles of 36 samples at SNP loci using observed phenotype. Sample code: the first number was for 3 subjects, the second letter was for hair body site origin (H: head, A: arm, and P: public), and the third number was for 4 samples originated from a hair.