A comparative structural study of nitrogen-rich fulvic acids from various Antarctic lakes

2017 ◽  
Vol 14 (8) ◽  
pp. 502 ◽  
Author(s):  
Sahar Farzadnia ◽  
Rama D. Nimmagadda ◽  
Christopher McRae
Keyword(s):  
Fulvic Acid ◽  
13C Nmr ◽  
Photoelectron Spectroscopy ◽  
Fulvic Acids ◽  
Magic Angle Spinning ◽  
Gas Chromatography Mass Spectrometry ◽  
Magic Angle ◽  
Similarities And Differences ◽  
Vestfold Hills ◽  
Cp Mas 13C Nmr

Environmental contextFulvic acids are important naturally occurring organic materials, but unravelling their complex structures remains challenging. This paper suggests chemical analyses to facilitate structural studies of fulvic acids, and to investigate the similarities and differences of fulvic acids from various natural sources. AbstractWe comprehensively examined fulvic acids isolated from three lakes in Vestfold Hills, eastern Antarctica and microbial reference fulvic acid from Pony Lake located in western Antarctica. These fulvic acids were compared in terms of their structural similarities and differences by means of elemental analysis, cross polarisation magic-angle spinning (CP-MAS) 13C NMR spectroscopy, X-ray photoelectron spectroscopy (XPS) and tetramethylammonium hydroxide (TMAH) thermochemolysis coupled to gas chromatography–mass spectrometry (GC-MS). The results indicate that these Antarctic fulvic acids show notable differences in chemical composition and structure; in particular XPS demonstrates that the distribution of nitrogen-containing compounds in the nitrogen-rich Antarctic fulvic acids differ significantly from each other. The dissimilarities are also highlighted in terms of quantity and quality of their nitrogenous constituents. For instance, Organic Lake Fulvic Acid (OLFA) contains around 10 times lower amide groups (pyrimidine–peptide N) than Pendant Lake Fulvic Acid (PNFA). It also shows 1.5 times less quaternary amine than Mossel Lake Fulvic Acid (MLFA) and PNFA. According to CP-MAS 13C NMR experiments the carbohydrate content in Vestfold Hills fulvic acid is higher than that of Pony Lake Fulvic Acid (PLFA), suggesting that dissolved organic matter (DOM) from Vestfold Hills Lakes is immature. TMAH–GC-MS demonstrated that Antarctic fulvic acids are enriched in heterocyclic non-aromatic nitrogen-containing components such as pyrimidine structures, with the exception of OLFA. Furthermore, tricyclic terpenoids (dehydroabietic acid) were detected in two out of four fulvic acids tabulated using TMAH–GC-MS. Although diterpenes are commonly associated with plants and fungi, their occurrence in Antarctic fulvic acids could be justified due to their diverse origins from cyanobacteria to aerosols.

scholarly journals Structural Studies of the Cutin from Two Apple Varieties: Golden Delicious and Red Delicious (Malus domestica)

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5955
Author(s):  
Daniel Arrieta-Baez ◽  
María de Jesús Perea Flores ◽  
Juan Vicente Méndez-Méndez ◽  
Héctor Francisco Mendoza León ◽  
Mayra Beatriz Gómez-Patiño
Keyword(s):  
Mass Spectrometry ◽  
13C Nmr ◽  
Octadecenoic Acid ◽  
Magic Angle Spinning ◽  
Laser Scanning Microscopy ◽  
Elastic Behavior ◽  
Magic Angle ◽  
Apple Varieties ◽  
Golden Delicious ◽  
Cp Mas 13C Nmr

The cuticle, a protective cuticular barrier present in almost all primary aerial plant organs, has a composition that varies between plant species. As a part of the apple peel, cuticle and epicuticular waxes have an important role in the skin appearance and quality characteristic in fresh fruits destined for human consumption. The specific composition and structural characteristics of cutin from two apple varieties, “golden delicious” and “red delicious”, were obtained by enzymatic protocols and studied by means of cross polarization magic angle spinning nuclear magnetic resonance (CP-MAS 13C NMR), attenuated total reflection infrared spectroscopy (ATR-FTIR), and mass spectrometry, and were morphologically characterized by specialized microscopy techniques (atomic force microscopy (AFM), confocal laser scanning microscopy (CLMS), and scanning electron microscopy (SEM)). According to CP-MAS 13C NMR and ATR-FTIR analysis, cutins from both varieties are mainly composed of aliphatics and a small difference is shown between them. This was corroborated from the hydrolyzed cutins analysis by mass spectrometry, where 9,10,18-trihydroxy-octadecanoic acid; 10,20-Dihydroxy-icosanoic acid; 10,16-dihydroxy hexadecenoic acid (10,16-DHPA); 9,10-epoxy-12-octadecenoic acid; and 9,10-epoxy-18-hydroxy-12-octadecenoic acid were the main monomers isolated. The low presence of polysaccharides and phenolics in the cutins obtained could be related to the low elastic behavior of this biocomposite and the presence of cracks in the apple cutin’s surface. These cracks have an average depth of 1.57 µm ± 0.57 in the golden apple, and 1.77 µm ± 0.64 in those found in the red apple. The results obtained in this work may facilitate a better understanding that mechanical properties of the apple fruit skin are mainly related to the specific aliphatic composition of cutin and help to much better investigate the formation of microcracks, an important symptom of russet formation.

scholarly journals The existence of cellulose and lignin chemical connections in ginkgo traced by 2H-13C dual isotopes

BioResources ◽  
2020 ◽  
Vol 15 (4) ◽  
pp. 9028-9044
Author(s):  
Yimin Xie ◽  
Yanchao Liu ◽  
Chen Jiang ◽  
Hongfei Wu ◽  
Shuying Bi
Keyword(s):  
13C Nmr ◽  
Magic Angle Spinning ◽  
Hydroxyl Group ◽  
Magic Angle ◽  
Ester Bond ◽  
Cross Polarization ◽  
Coa Ligase ◽  
Angle Spinning ◽  
A Minor ◽  
Cp Mas 13C Nmr

To elucidate the covalent association between the celluloses and lignins found in gymnosperms, they were labeled with stable isotopes (deuterium and carbon-13) at specific positions and traced via mass spectroscopy and nuclear magnetic resonance (NMR). Both the 2H-labeled cellulose precursor (UDP-glucose-[6-2H2]) and the 13C-labeled lignin precursor (coniferin-[α-13C]) were added to a growing ginkgo plant, in combination with a 4-coumarate-CoA ligase inhibitor. The detection of abundance of 13C and 2H revealed that the lignin precursor and cellulose precursor deposited more actively in 300 to 1300 μm and 100 to 900 μm distance from cambium, respectively. The lignin-carbohydrate complexes (LCCs) were isolated from the newly-formed ginkgo shoot xylem and further degraded with cellulase and hemicellulase to obtain enzymatically degraded lignin-carbohydrate complexes (EDLCCs). Analysis of the solid-state cross polarization / magic angle spinning (CP/MAS) 13C-NMR of the newly-formed xylem, liquid-state 13C-NMR, and 1H-NMR of the EDLCCs confirmed that the major connection between celluloses and lignins was a benzyl ether bond (between cellulose C6 and lignin Cα). A minor ester bond was also found between the hydroxyl group (at the 6-position of cellulose) and ferulic acid (at the γ position in lignins).

scholarly journals Heat-Induced Discoloration of Chromophore Structures in Eucalyptus Lignin

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1686 ◽  
Author(s):  
Peng Zhang ◽  
Yanxia Wei ◽  
Yang Liu ◽  
Jianmin Gao ◽  
Yao Chen ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Photoelectron Spectroscopy ◽  
Eucalyptus Grandis ◽  
Gel Permeation Chromatography ◽  
Magic Angle Spinning ◽  
Saturated Steam ◽  
Magic Angle ◽  
13C Cpmas Nmr ◽  
Eucalyptus Wood ◽  
Dehydration Reactions

The color changes corresponding to chromophore structures in lignin caused by exposure of Eucalyptus (Eucalyptus grandis and E. urophylla) to heat were investigated. Eucalyptus wood powders were heat treated under saturated steam atmospheres for 10 h at 110 °C, 130 °C and 150 °C. The lignin was isolated before and after heat treatment. The physicochemical properties of the lignin and changes in chromophore structures during heat treatment was evaluated through wet chemical analysis, Fourier transform infrared spectroscopy (FTIR), diffuse reflectance ultraviolet-visible spectroscopy (DRUV-Vis), gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and 13C Cross polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR). Wood color darkened and reddened with the increase in pressure and temperature. Depolymerization and dehydration reactions occurred via demethoxylation with heat treatment in saturated steam at 110 °C or 130 °C. Lignin condensed to form insoluble compounds after heat treatment in saturated steam at 150 °C. G units increased and S units decreased through demethylation during heat treatment, as revealed by FTIR and 13C-NMR analysis.

Solid State 13C NMR Applied to Styrene-Butadiene Rubbers Study of the Rubber Vulcanized Network Structures

2002 ◽  
Vol 75 (1) ◽  
pp. 65-76 ◽  
Author(s):  
L. Pellicioli ◽  
S. K. Mowdood ◽  
F. Negroni ◽  
D. D. Parker ◽  
J. L. Koenig
Keyword(s):  
13C Nmr ◽  
Structural Changes ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Nmr Spectrum ◽  
Polymer Microstructure ◽  
Polybutadiene Rubber ◽  
Angle Spinning ◽  
Styrene Butadiene

Abstract This paper discusses the structural changes that occur during the accelerated sulfur vulcanization of styrene-butadiene rubbers (SBR) through characterization of the network sulfide structures influenced by the curing agent concentration, the polymer microstructure, and the nature of the filler. Magic angle spinning (MAS) 13C FT - NMR spectroscopy was used to investigate the chemical crosslink properties of unfilled vulcanized SBR in addition to carbon black and silica filled polybutadiene rubber (BR), SBR, and 1:1 BR / SBR blends. New resonances in the 13C NMR spectrum are assigned to the various sulfide crosslink structures in SBR. Structural changes during vulcanization are also discussed.

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