Multi-dimensional NMR Method for Coupling Constant Measurement
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Solution Overview
Problem
Current NMR spectroscopy methods are inefficient in measuring 1H—1H coupling constants across multiple coupling networks due to small chemical-shift dispersion and complex splitting patterns, requiring multiple experiments to analyze each network separately.
Innovation Solution
A multi-dimensional NMR method involving a conventional 1D spectrum acquisition, selective pulses, spatial frequency encoding gradients, and a PSYCHE element with chirp pulses and spoiling gradients, allowing simultaneous measurement of coupling constants within multiple networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional NMR method is used to measure 1H—1H coupling constants, then the measurement can be performed, but multiple separate experiments are required for each coupling network, reducing efficiency
Solution Approach 1:
The patent combines multiple separate NMR experiments into a single multi-dimensional experiment that can simultaneously measure coupling constants for multiple coupling networks. The PSYCHE element and EPSI readout are integrated into one pulse sequence, allowing parallel acquisition of data for different proton coupling networks that previously required separate experiments.
Solution Approach 2:
The patent transitions from one-dimensional NMR spectra to multi-dimensional NMR spectroscopy to resolve overlapping signals and complex splitting patterns. By adding temporal and spatial dimensions through the PSYCHE element and EPSI readout, the method can distinguish and measure multiple coupling networks simultaneously without signal overlap interference.
2Measurement precision
If conventional NMR spectroscopy is used, then coupling constants can be measured, but small chemical-shift dispersion and complex splitting patterns hamper the measurement accuracy
Solution Approach 1:
The patent uses multi-dimensional NMR spectroscopy with the PSYCHE element to disperse signals in additional spectral dimensions, separating overlapping resonances and simplifying complex splitting patterns. This allows accurate measurement of coupling constants even when chemical-shift dispersion is small in the conventional one-dimensional spectrum.
3Productivity
If the PSYCHEDELIC method is used to reveal scalar coupling networks, then coupling constants can be extracted, but only one coupling network can be analyzed at a time
Solution Approach 1:
The patent merges the PSYCHE element with EPSI (echo-planar spectroscopic imaging) readout to create a unified pulse sequence that can simultaneously analyze multiple coupling networks. This integration allows the method to process multiple proton networks in a single experiment rather than requiring separate PSYCHE experiments for each network.
Solution Approach 2:
The patent creates a universal NMR method that can handle multiple coupling networks simultaneously through the multi-dimensional PSYCHE-EPSI approach. The pulse sequence is designed to be versatile, capable of extracting coupling constants for various proton networks within a single experimental framework, eliminating the need for network-specific experiments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the simultaneous revelation of several scalar coupling networks and extraction of all coupling constants, improving efficiency and reducing the need for multiple experiments, with applications in molecular structure elucidation.
Implementation Method 1
Spin-spin coupling, an important parameter in NMR spectroscopy, plays an important role in molecular structure analysis.
Implementation Method 2
two chirp pulses with low flip angle and opposite sweeping direction is implemented at the presence of another gradient
Implementation Method 3
The PSYCHE element is flanked by two spoiling gradients Gs
Implementation Method 4
the EPSI readout is used to record NMR signals. The EPSI readout mentioned above includes oscillating gradients Ga and −Ga, and simultaneous samplings
Data Source
AI summary
This invention provides a NMR multi-dimensional method for measuring coupling constants within several coupling networks. At first, a 90° hard pulse was performed to flip the magnetization from the Z axis to the XY plane. After t1/2, a selective 180° pulse is implemented with a simultaneous Z-direction gradient, thus reversing different protons at different slices. Then the PSYCHE element is implemented. After another t1/2, the gradient G1 and Gp are implemented. At last, the EPSI readout is used to simultaneously record both the chemical-shift and the spatial information. As a result, from different specific slices, we can extract the scalar couplings between the proton reversed at this slice and other protons. These couplings lead to splittings in the indirect dimension, from which relevant coupling constants can be measured.