Table 2 SERS peak positions and the tentative vibrational assignments of the penguin brain tissue specimens under NIR (785 nm) excitation wavelength^{16,17,44,45,46,47,51,52,53,54,55,56}.

547

Amino acids (tryptophan) combined with nucleobases DNA and RNA (cytosine and guanine)

623

C–C twisting mode of phenylalanine

642

C–C twisting mode of tyrosine

661

C–S stretching mode of cystine

704

CH₂ rocking coupled with symmetric breathing of l-tyrosine

719

Symmetric choline C–N stretch (membrane phospholipid head) coupled with ring breathing mode of DNA/RNA nucleobases adenine

744

CH₂ rocking coupled with symmetric breathing of tryptophan, mitochondria, and cytochrome c

880

Secondary amino acid proline

964

Hydroxyapatite (PO₄³⁻ symmetric stretching)/carotenoid/cholesterol

978

C-H out-of-plane deformation coupled with C–C asymmetric stretching of Deoxygenated cells, cytochrome c, and porphyrin

1003

Symmetric C–C aromatic ring breathing mode of phenylalanine and collagen IV, and I

1067

C–C stretching coupled with C–C skeletal stretching, PO₂ symmetric stretching of nucleic acid, protein, phospholipid, glycogen, and collagen IV

1088

1131

C–N stretching in proteins

1158

C–C stretching of carotenoids coupled with C–N stretching of proteins

1179

C-H in-plane bending of hemoglobin, tyrosine, and flavin

1273

In-plane deformation of N–H, C–N stretching

1305

CH₃ in-plane deformation of amide III

1351

CH₃₋ (C=O) tryptophan, mitochondria, cytochrome c

1384

CH₃ in-phase deformation, methyl symmetric bending of thymine, adenine, and guanine of DNA

1399

CH₃ bending due to methyl bond in the membrane

1448

δ(CN) bending, δ(CH)₃ out-of-phase deformation of lipid and protein

1556

C=C tryptophan, porphyrin

1622

C=C stretching mode of tyrosine and tryptophan

1661

Amide I (proteins with b-sheet conformational structures), ν(C=O), and collagen I, IV