## 2 Evolution of NMR Methodologies
### Solid-State NMR for Polysaccharides
#### 2.2.1 Crystalline and Non-Crystalline Polysaccharides  
Solid-state NMR is a crucial technique for distinguishing the difference between the crystalline and amorphous regions of polysaccharides, offering detailed information about their molecular structure. This distinction is particularly important in plant cell walls, where the mechanical properties depend on the balance between crystalline and amorphous regions. For example, [PERSON] et al. used CP/MAS NMR to compare the polysaccharide structures in the thick-walled corneum tissue and the thinner-walled celery cell walls. Their study revealed structural differences that were linked to the mechanical functions of these tissues [2]. [PERSON] et al. used \({}^{13}\)C CP/MAS NMR spectroscopy to study the molecular composition of organic matter in many biological kingdoms. These kingdoms, including bacteria, fungi, algae, and higher plants, are illustrated in Figure 3[35]. The key point is that the largest publicly available library containing 108 unique NMR \({}^{13}\)C spectra has been created. These spectra can clearly indicate the difference between carbon types. They can also show how carbon is distributed among different species and functional groups. This method can show the different chemical properties of organisms from different kingdoms. It also points out the functional differences in plant tissues like leaves, roots, and wood. The analysis yields critical insights into the carbon cycle and decomposition processes in the ecosystem.  
[PERSON] et al. used magic-angle spinning NMR to study the spectra of polysaccharides in whole cells, improving the clarity of the cell wall's structure and understanding of its functions [36]. These examples show that solid-state NMR has made an important contribution to elucidating the complex structural organization of polysaccharides in different biological systems. By combining structural details with functional insights, ssNMR continues to enhance our understanding of the relationship between molecular architecture and biological properties.  
The innovation of DNP-enhanced NMR has greatly improved the sensitivity of ssNMR technology. This improvement allows researchers to study the structure of low-abundance polysaccharides. [PERSON] et al. used this method to study wood polysaccharides during termite fermentation. Through this study, they obtained important insights into the enzymatic degradation mechanisms related to biofuel production [10].  
In food science, [PERSON] et al. used ssNMR technology to study how the crystallinity and amorphous regions of apple polysaccharides work. They showed how these differences in structure impact the texture and ripening processes of apples [37]. [PERSON] and his group also found that the crystal cellulose structure reorganized after the extraction of polysaccharides. These findings demonstrate an idea of how processing affects the composition of plant cell walls [38]. [PERSON] et al. utilized ssNMR technology to investigate the molecular structure of fungal cell walls, revealing the complex structures of chitin and chitosan. They also discovered the interactions between rigid and mobile domains. The technique provides insights into the organization of cell walls at the atomic level and helps to solve the problems of understanding the complex structure and dynamics of cell walls [39]. [PERSON] et al. completed structural elucidation of capsular polysaccharides from _Klebsiella_ I-714 with advanced NMR technology in industrial applications [40]. These studies together show the versatility of ssNMR in unraveling the complex relationships between structure and function in polysaccharides, enabling applications across agriculture, food science, and renewable energy research.  
Figure 3: Solid-state \({}^{13}\)C CP/MAS NMR spectroscopy to characterize the molecular composition of organic matter across multiple biological kingdoms, including bacteria, fungi, algae, and higher plants. Copyright (2024) Elsevier.