Near-Infrared Multispectral Imaging Technique for Visualizing Sequences of Di- and Tripeptides Synthesized by Solid Phase Combinatorial Method

Abstract

A new method based on the near-infrared (NIR) multispectral imaging technique has been developed for the noninvasive and nondestructive determination of the identity and sequences of amino acid residues in di- and tripeptides. The di- and tripeptides were synthesized on polymer beads (i.e., Rink) using the solid phase peptide synthetic method. The developed method is capable of determining the identity of sequences of the peptides (with and without the Fmoc protecting group) directly on the polymer beads. It can distinguish not only dipeptides from tri-peptides but also peptides with very similar structures (e.g., Rink-Gly-Ala-Ala, Rink-Gly-Ala-Phe, Rink-Gly-Ala-Leu, Rink-Gly-Ala-Val, and Rink-Gly-Ala-Met). More importantly, it is capable of distinguishing peptides with the same amino acid residues but different sequences (e.g., Rink-Gly-Leu-Val from Rink-Gly-Val-Leu).

Visualizing Chemical Compositions and Kinetics of Sol−Gel by Near-Infrared Multispectral Imaging Technique

“…Instrumentation. The NIR multispectral imaging instrument used in this study is similar to the imaging spectrometer used in our previous studies. − , Essentially, in this instrument, a 250-W, 12-V halogen−tungsten lamp was used as the light source. A 2.5-cm-focal length ZnSe lens was used to collimate the incident white light from the lamp into a noncollinear AOTF (Crystal Technologies).…”

“…In these instruments, the spatial distribution of the sample is obtained by a camera, and the spectral information is gained by scanning a dispersive element. − To be used for kinetic determination, the instrument must be able to sensitively and rapidly record spectral images of a sample. These requirements can be satisfactorily met with the instrument recently developed in our laboratory. − In this instrument, an acoustooptic tunable filter (AOTF) is used for spectral scanning and an InGaAs area camera is for recording NIR images. − AOTF is a electronic tunable filter based on the diffraction of light by an acoustic wave in an anisotropic medium. It has rapid scanning ability (μs), high diffraction efficiency (>90%), wide spectral tuning range (from UV to NIR), and high resolution. − Because of these advantages, the multispectral imaging instrument based on an AOTF has high sensitivity and can rapidly record spectral images of a sample.…”

“…This imaging spectrometer makes it possible for us to perform studies that to date were not possible using existing techniques. These include the authentication of documents, the determination of chemical inhomogeneity of ethylene/vinyl acetate copolymers and kinetic inhomogeneity of curing of epoxy by amine, and the determination of identity and sequences of peptides synthesized by combinatorial solid-phase method. − …”