title: 2D IR spectroscopy using four-wave mixing, pulse shaping, and IR upconversion: a quantitative comparison.
abstract: Recent technological advances have led to major changes in the apparatuses used to collect 2D IR spectra. Pulse shaping offers several advantages including rapid data collection, inherent phase stability, and phase-cycling capabilities. Visible array detection via upconversion allows the use of visible detectors that are cheaper, faster, more sensitive, and less noisy than IR detectors. However, despite these advantages, many researchers are reluctant to implement these technologies. Here we present a quantitative study of the S/N of 2D IR spectra collected with a traditional four-wave mixing (FWM) apparatus, with a pulse shaping apparatus, and with visible detection via upconversion to address the question of whether weak chromophores at low concentrations are still accessible with such an apparatus. We find that the enhanced averaging capability of the pulse shaping apparatus enables the detection of small signals that would be challenging to measure even with the traditional FWM apparatus, and we demonstrate this ability on a sample of cyanylated dihydrofolate reductase.
authors.affiliation: Department of Chemistry and Optical Science and Technology Center, University of Iowa, Iowa City, Iowa 52242, USA.
authors.forename: William
authors.initials: W
authors.lastname: Rock
authors.forename: Yun-Liang
authors.initials: YL
authors.lastname: Li
authors.forename: Philip
authors.initials: P
authors.lastname: Pagano
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Cheatum
mesh_terms: D000042:Absorption; D003485:Cyanates / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry; D004126:Dimethylformamide / Q000737:chemistry; D059629:Signal-To-Noise Ratio; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013762:Tetrahydrofolate Dehydrogenase / Q000737:chemistry
chemical_list: D003485:Cyanates; D004126:Dimethylformamide; D013762:Tetrahydrofolate Dehydrogenase; D003545:Cysteine