Sensitive Carbohydrate Detection Using Surface Enhanced Raman Tagging

摘要

Glycomic analysis is an increasingly important field innbiological and biomedical research as glycosylation is onenof the most important protein post-translational modifications.nWe have developed a new technique to detectncarbohydrates using surface enhanced Raman spectroscopyn(SERS) by designing and applying a Rhodamine Bnderivative as the SERS tag. Using a reductive aminationnreaction, the Rhodamine-based tag (RT) was successfullynconjugated to three model carbohydrates (glucose, lactose,nand glucuronic acid). SERS detection limits obtainednwith a 633 nm HeNe laser were ∼1 nM in concentrationnfor all the RT-carbohydrate conjugates and ∼10 fmol inntotal sample consumption. The dynamic range of the SERSnmethod is about 4 orders of magnitude, spanning from 1nnM to 5 μM. Ratiometric SERS quantification usingnisotope-substituted SERS internal references allows comparativenquantifications of carbohydrates labeled with RTnand deuterium/hydrogen substituted RT tags, respectively.nIn addition to enhancing the SERS detection of thentagged carbohydrates, the Rhodamine tagging facilitatesnfluorescence and mass spectrometric detection of carbohydrates.nCurrent fluorescence sensitivity of RT-carbohydratesnis ∼3 nM in concentration while the massnspectrometry (MS) sensitivity is about 1 fmol, achievednwith a linear ion trap electrospray ionization (ESI)-MSninstrument. Potential applications that take advantage ofnthe high SERS, fluorescence, and MS sensitivity of thisnSERS tagging strategy are discussed for practical glycomicnanalysis where carbohydrates may be quantified with anfluorescence and SERS technique and then identified withnESI-MS techniques.