Detection of enzyme‐triggered peptide self‐assembly via laser confocal Raman microscopy and circular dichroism spectroscopy in cellular environment

Abstract

Vibrational spectroscopy of peptides and peptide‐based self‐assembled macromolecules plays key role in early stage detection of cancerous and viral diseases. We provide here a rapid and accurate trace detection system for enzyme‐triggered peptide self‐assembly by taking a snapshot of peptide nanostructures to identify specific domains based on amino acid vibrational bands. The enzyme‐triggered peptides present in both aqueous solution and human umbilical vein endothelial cells along with controlled cell lines were excited by a laser line of 543 nm, and intensities of Raman bands were recorded from 500 to 1,800 cm−1. The spectra consisted of several well‐resolved peaks located at 655, 1,081, and 1670 cm−1 for peptide and at 834, 851, 896, and 915 cm−1 for enzyme, indicating vibrational bands of their functional groups. Raman signatures at 768, 1,144, 1,297, 1,305, and 1,571 cm−1 appeared in case of self‐assembled peptides at new positions, indicating the presence of highly stable secondary structure of beta sheets. We studied here the 0.78 μg/ml limit of detection of peptide self‐assembly with this technique in aqueous solution. These self‐assembled nanomachines in cellular environment can be used to monitor and regulate the cellular processes for the diagnosis of biological diseases incorporated with our label‐free laser confocal Raman microscopy methodology.

Self-Assembled Nanostructures of Homo-Oligopeptide as a Potent Ice Growth Inhibitor

“…Furthermore, the Raman analysis provides detailed information regarding the self-assembled structures (Figure c and Table S2). Amide I (1580–1700 cm –1 ) and III (1200–1300 cm –1 ) are frequently used to determine the secondary structure of peptides . The Raman shift at 1660–1667 cm –1 (CO stretching vibration) of the amide I band and the shift for antiparallel β-sheet structure were observed in all self-assembled nanostructures (Ala-5 [1660 cm –1 ], Thr-5 [1662 cm –1 ], Val-5 [1662 cm –1 ], and Tyr-5 [1667 cm –1 ]) .…”