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Related Concept Videos

IR Spectroscopy: Molecular Vibration Overview01:24

IR Spectroscopy: Molecular Vibration Overview

5.6K
When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
5.6K
Infrared (IR) Spectroscopy: Overview01:09

Infrared (IR) Spectroscopy: Overview

6.3K
When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation corresponding to the energy difference between the two states. The absorption of infrared (IR) radiation causes transitions between vibrational energy levels in a molecule. Therefore, IR spectroscopy is a useful analytical tool for determining the molecular structure of molecules.
Different compounds display unique properties due to their...
6.3K
IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations01:08

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

2.0K
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single...
2.0K
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

1.7K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.7K
IR Spectrum Peak Broadening: Hydrogen Bonding01:23

IR Spectrum Peak Broadening: Hydrogen Bonding

2.0K
The vibrational frequency of a bond is directly proportional to its bond strength. As a result, stronger bonds vibrate at higher frequencies, while weaker bonds vibrate at lower frequencies. The stretching vibration of the strong O–H bond in alcohols and phenols (very dilute solution or gas phase) appears as a sharp peak at 3600–3650 cm−1.
However, the extent of hydrogen bonding influences the observed stretching frequency and band broadening. Intermolecular or intramolecular...
2.0K
IR Frequency Region: Fingerprint Region01:03

IR Frequency Region: Fingerprint Region

2.1K
IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the...
2.1K

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Related Experiment Video

Updated: Mar 8, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
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The Grateful Infrared: Sequential Protein Structural Changes Resolved by Infrared Difference Spectroscopy.

Tilman Kottke1, Víctor A Lórenz-Fonfría, Joachim Heberle2

  • 1Department of Chemistry, Physical and Biophysical Chemistry, Bielefeld University , Universitätsstraße 25, 33615 Bielefeld, Germany.

The Journal of Physical Chemistry. B
|January 20, 2017
PubMed
Summary

Time-resolved IR spectroscopy reveals subtle structural changes in light-activated proteins like channelrhodopsin (ChR), light-oxygen-voltage (LOV) proteins, and cryptochrome (CRY). This technique tracks hierarchical reactions, offering insights into protein function and optogenetics.

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Area of Science:

  • Biophysics
  • Spectroscopy
  • Protein Dynamics

Background:

  • Protein catalytic activity is intrinsically linked to structural dynamics, including protonation and hydrogen bonding changes.
  • Understanding these minute structural shifts is crucial for elucidating protein function and biological roles.
  • Channelrhodopsin (ChR), light-oxygen-voltage (LOV) proteins, and cryptochromes (CRY) are key blue-light photoreceptors with diverse functions.

Purpose of the Study:

  • To showcase the application of time-resolved IR spectroscopy for resolving structural changes in photoreceptor proteins.
  • To demonstrate the capability of IR difference absorption spectroscopy in tracking hierarchical reaction sequences.
  • To highlight the utility of these techniques in understanding the molecular mechanisms of ChR, LOV, and CRY proteins.

Main Methods:

  • Utilizing time-resolved infrared (IR) spectroscopy to monitor protein structural changes.
  • Employing IR difference absorption spectroscopy to detect subtle molecular alterations post-photonic activation.
  • Applying techniques covering a time range from nanoseconds to minutes.

Main Results:

  • IR difference absorption successfully resolved critical structural changes in ChR, LOV, and CRY proteins following chromophore activation.
  • The study traced the sequence of hierarchical reactions occurring within these proteins.
  • Key structural dynamics related to protein function and optogenetic applications were elucidated.

Conclusions:

  • Time-resolved IR spectroscopy is a powerful methodology for achieving molecular sensitivity and tracking reaction sequences in proteins.
  • This technique provides crucial insights into the structure-function relationships of blue-light photoreceptors.
  • Future experimental approaches hold promise for advancing our understanding of protein dynamics and novel scientific discoveries.