A new method of phase sensitive detection in modulation spectroscopy applied to temperature induced folding and unfolding of RNase A

Baurecht, Dieter; Porth, Ilga; Fringeli, U. P.

doi:10.1016/s0924-2031(02)00042-5

Cited by 41 publications

(43 citation statements)

References 13 publications

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“…[8][9][10] Yet, most of the available methods are still in vitro ones. Generally, a given control parameter is suddenly modified and the relaxation of the chemical system towards its new equilibrium state is monitored in time using spectroscopic acquisition (e.g., fluorescence emission, 2, 11-13 circular dichroism, 2, 11-13 nuclear magnetic resonance (NMR), 2,14 and Fourier transform infrared (FTIR) absorption 15,16 ). Concerning the applied perturbation, the concentration in reagents or the nature of the buffer can be changed by molecular advection coupled to diffusion, as in stopped-flow devices, 2,[11][12][13]17 microfluidic mixers, 18,19 and surface plasmon resonance (SPR) biosensors.…”

Section: Introductionmentioning

confidence: 99%

Identification of two-step chemical mechanisms and determination of thermokinetic parameters using frequency responses to small temperature oscillations

Closa

Gosse

Jullien

et al. 2013

The Journal of Chemical Physics

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Increased focus on kinetic signatures in biology, coupled with the lack of simple tools for chemical dynamics characterization, lead us to develop an efficient method for mechanism identification. A small thermal modulation is used to reveal chemical dynamics, which makes the technique compatible with in cellulo imaging. Then, the detection of concentration oscillations in an appropriate frequency range followed by a judicious analytical treatment of the data is sufficient to determine the number of chemical characteristic times, the reaction mechanism, and the full set of associated rate constants and enthalpies of reaction. To illustrate the scope of the method, dimeric protein folding is chosen as a biologically relevant example of nonlinear mechanism with one or two characteristic times.

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Section: Introductionmentioning

confidence: 99%

Identification of two-step chemical mechanisms and determination of thermokinetic parameters using frequency responses to small temperature oscillations

Closa

Gosse

Jullien

et al. 2013

The Journal of Chemical Physics

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“…If a catalytic system is perturbed by a periodic stimulation, all the parameters in the system, which are affected by this perturbation, will also change periodically at the same frequency as the stimulation or their harmonics, but with a phase delay (u) [2,11,12].…”

Section: Modulation Excitation Spectroscopy With Phasementioning

confidence: 99%

ATR-FTIR Study of the Decomposition of Acetic Anhydride on Fosfotungstic Wells–Dawson Heteropoly Acid Using Concentration-Modulation Excitation Spectroscopy

et al. 2011

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The decomposition of acetic anhydride in liquid phase on a fosfotungstic Wells-Dawson heteropoly acid (HPA) was investigated by in situ ATR-FTIR spectroscopy. Transient and concentration-modulation excitation spectroscopy (MES) experiments in combination with phase-sensitive detection (PSD) were used to monitor the solid-liquid interface. The MES method is based on the periodic variation of a parameter of the reaction media such as, the reactant concentration. That periodic alteration causes varying infrared signals of the surface adsorbed species that are subsequently demodulated with the PSD methodology. Thus, the separation of the static signals from the changing ones is achieved, and species with different response can be observed in the spectra. Using MES-PSD coupled with ATR-FTIR, acetic anhydride was observed to decompose to acetic acid, acetate and acyl [CH 3 C(O) ? ] species, involving Brønsted acid sites of the HPA catalyst. The CH 3 C(O) ? is a very unstable intermediate species and it is the key intermediate in the FriedelCrafts acylation reactions. Moreover, the acetate groups are spectator species since remain strongly adsorbed on the catalyst surface and do not further react.

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“…15,16 PSD acts as a software lock-in amplifier and can be used in modulated excitation FT-IR spectroscopy without the need of any additional expensive hardware. 3,5 It can be applied offline after that the spectra have been obtained, thereby avoiding complicated phase corrections and shortening the measuring time during data acquisition. Application of PSD converts the recorded time-resolved absorbance spectra into phase-resolved spectra and thereby (i) suppresses almost all frequency components of the noise and any constant background absorption, and (ii) permits the selective detection of signals that show the same frequency as the stimulation.…”

Section: Introductionmentioning

confidence: 99%

“…Due to this inherent validation, spectra evaluation by PSD is considered to be more confident than evaluation by first-order derivatives or Fourier self-deconvolution (FSD) that significantly depends on the operator choice of two parameters. 5 …”

Section: Introductionmentioning

confidence: 99%

Phase-Sensitive Detection in Modulation Excitation Spectroscopy Applied to Potential Induced Electron Transfer in Cytochrome c Oxidase

et al. 2014

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Cytochrome c oxidase (CcO) from Rhodobacter sphaeroides was investigated by modulated excitation surface-enhanced infrared-absorption spectroscopy (SEIRAS). Sequential electron transfer (ET) within CcO was initiated by electrochemical excitation. During modulated excitation by periodic potential pulses with frequencies between 20 and 500 Hz, time-resolved infrared spectra were measured by the step-scan technique, with time resolution in the millisecond range. Conformational changes of the protein structure as a result of ET lead to rather complex SEIRA spectra with many overlapping bands embedded in a broad background signal. Phase-sensitive detection (PSD) was used to separate single components within the broad band of overlapping structural bands in the amide I region. PSD is able to extract the periodic response of single components with the same frequency as the excitation from noise or from static background and therefore enhances the signal-to-noise ratio. Moreover, PSD enables validation of the fit model used for the deconvolution of overlapping bands by analyzing phase lags of single components acquired at different stimulation frequencies. Phase lags between the evaluated vibrational components and the modulated excitation increase with increasing excitation frequencies, an inherent prerequisite of this evaluation method.

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A new method of phase sensitive detection in modulation spectroscopy applied to temperature induced folding and unfolding of RNase A

Cited by 41 publications

References 13 publications

Identification of two-step chemical mechanisms and determination of thermokinetic parameters using frequency responses to small temperature oscillations

Identification of two-step chemical mechanisms and determination of thermokinetic parameters using frequency responses to small temperature oscillations

ATR-FTIR Study of the Decomposition of Acetic Anhydride on Fosfotungstic Wells–Dawson Heteropoly Acid Using Concentration-Modulation Excitation Spectroscopy

Phase-Sensitive Detection in Modulation Excitation Spectroscopy Applied to Potential Induced Electron Transfer in Cytochrome c Oxidase

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