Nmr Spectrometer Operation
Nmr Spectrometer Operation - Related Videos
01:20
NMR Spectrometers: Overview
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2024
NMR spectrometers consist of a strong magnet, a radiofrequency transmitter, and a detector attached to a computer console for recording spectra of samples containing NMR-active nuclei. In first-generation NMR instruments called continuous-wave spectrometers, the resonance frequencies of the nuclei are determined by frequency-sweep or field-sweep methods. The magnetic field strength is fixed and the rf signal is swept in the former, while the radiofrequency signal is fixed and the magnetic field...
01:14
NMR Spectrometers: Resolution and Error Correction
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2024
When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction decay. Fourier transform of an exponential decay yields a Lorentzian peak in the frequency domain. Lorentzian peaks in an NMR spectrum are defined by their amplitude, full width at half maximum, and position, where the peak width is governed by the spin-spin relaxation time alone. In real experiments, however, the applied magnetic field is rendered...
01:17
NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences
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2024
A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
16:20
Hyperpolarized Xenon for NMR and MRI Applications
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Cited by 28 •
2012
The production of hyperpolarized xenon by means of spin exchange optical pumping (SEOP) is described. This method yields a ~10000-fold enhancement of the nuclear spin polarization of Xe-129 and has applications in nuclear magnetic resonance spectroscopy and imaging. Examples of gas phase and solution state experiments are given.
01:25
IR Spectrometers
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2024
There are two main infrared (IR) spectrophotometers: dispersive IR spectrometers and Fourier transform infrared (FTIR) spectrometers. In a dispersive IR spectrometer, a beam of infrared radiation produced by a hot wire is divided into two parallel equal-intensity beams using mirrors. One beam passes through the sample, while another is a reference beam. The beams then move through the monochromator, which separates the radiations into a continuous spectrum of different frequencies. The...
FAQs
Different nuclei, including 1H, 13C, and 15N, provide information about different parts of a biological molecule and their chemical environments. Their responses depend on how they align with the magnetic field and interact with the applied radiofrequency energy. Selecting among these nuclei therefore helps focus measurements on proteins, metabolites, nucleic acids, or other molecular components.
The instrument applies radiofrequency energy tuned to the nuclei being examined, temporarily changing their state relative to the magnetic field. As the nuclei return toward equilibrium, they emit signals that contain information about their chemical environment. The timing and characteristics of this return provide the measured response used to distinguish molecular features in the resulting spectrum.
The instrument first records signals as time-domain data, meaning the response is tracked as it changes over time. Fourier transformation mathematically converts those data into a spectrum, where molecular signals can be examined according to their spectral positions and patterns. This conversion makes the recorded response useful for assessing structure and chemical composition.
Spectral signals can reflect differences in molecular structure and chemical environment, allowing investigators to examine more than simple sample composition. In biological research, the same measurement can contribute to studies of molecular structure, dynamics, and interactions. The resulting information helps connect observed signals with the behavior or organization of proteins, metabolites, and nucleic acids.
A typical measurement places the biological sample in the strong magnetic field, applies radiofrequency pulses selected for the nuclei of interest, and records the emitted response as the nuclei return toward equilibrium. The recorded time-domain signal is then Fourier transformed into a spectrum. This sequence produces the data used for molecular interpretation without destroying the sample.
Biologists use the approach to characterize proteins, metabolites, and nucleic acids, as well as to investigate biomolecular interactions. It can support questions about molecular structure, dynamics, composition, and function. Because the measurement is non-destructive, it is also suited to examining biological material in solution or in complex samples while preserving the material for related analyses.
Changes in the signals emitted by selected nuclei can reveal altered chemical environments when molecules interact. Examining those spectral responses provides a way to study interactions alongside molecular structure and dynamics. In biology, this makes the method relevant for connecting molecular association with broader questions about composition and function in solution or complex samples.