Introduction: Fourier transform infrared spectroscopy (FTIR) is a rapid vibrational method used in research peptide laboratories to characterize solid samples and solutions. Absorbance bands from peptide bonds provide a fingerprint of composition and conformation with minimal sample preparation.
Principles: FTIR measures infrared absorbance across a wavenumber range. The amide I band, arising mainly from carbonyl stretching, is sensitive to secondary structure, while the amide II band reflects N-H bending and C-N stretching. Deconvolution of the amide I envelope can estimate contributions from helix, sheet, turn, and disordered conformations in a sample.
Laboratory Applications:
- Comparing lyophilized batches for consistent solid-state characteristics
- Assessing secondary structure alongside circular dichroism and Raman spectroscopy
- Detecting changes after accelerated stability storage
- Confirming identity as part of a multi-technique characterization panel with HPLC and mass spectrometry
Advantages and Limitations: FTIR is fast, works on solids via ATR sampling, and needs little material. Limitations include water interference in aqueous samples, overlapping bands that require careful deconvolution, and the fact that results are comparative rather than absolute — they are interpreted alongside orthogonal methods.
References: Standard infrared spectroscopy literature; analytical reviews on FTIR methods in peptide and protein characterization; USP general chapters on spectroscopy.
Disclaimer: This article is for laboratory research education only. All products referenced are not for human consumption / research use only. No medical, therapeutic, dosing, or efficacy information is provided or implied.