| 1. |
- Koso, Tetyana, et al.
(author)
-
2D Assignment and quantitative analysis of cellulose and oxidized celluloses using solution-state NMR spectroscopy
- 2020
-
In: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 27:14, s. 7929-7953
-
Journal article (peer-reviewed)abstract
- The limited access to fast and facile general analytical methods for cellulosic and/or biocomposite materials currently stands as one of the main barriers for the progress of these disciplines. To that end, a diverse set of narrow analytical techniques are typically employed that often are time-consuming, costly, and/or not necessarily available on a daily basis for practitioners. Herein, we rigorously demonstrate a general quantitative NMR spectroscopic method for structural determination of crystalline cellulose samples. Our method relies on the use of a readily accessible ionic liquid electrolyte, tetrabutylphosphonium acetate ([P-4444][OAc]):DMSO-d(6), for the direct dissolution of biopolymeric samples. We utilize a series of model compounds and apply now classical (nitroxyl-radical and periodate) oxidation reactions to cellulose samples, to allow for accurate resonance assignment, using 2D NMR. Quantitative heteronuclear single quantum correlation (HSQC) was applied in the analysis of key samples to assess its applicability as a high-resolution technique for following cellulose surface modification. Quantitation using HSQC was possible, but only after applying T(2)correction to integral values. The comprehensive signal assignment of the diverse set of cellulosic species in this study constitutes a blueprint for the direct quantitative structural elucidation of crystalline lignocellulosic, in general, readily available solution-state NMR spectroscopy. [GRAPHICS] .
|
|
| 2. |
- Mai-Gisondi, Galina, et al.
(author)
-
Functional comparison of versatile carbohydrate esterases from families CE1, CE6 and CE16 on acetyl-4-O-methylglucuronoxylan and acetyl-galactoglucomannan
- 2017
-
In: Biochimica et Biophysica Acta - General Subjects. - : Elsevier BV. - 1872-8006 .- 0304-4165. ; 1861:9, s. 2398-2405
-
Journal article (peer-reviewed)abstract
- Background The backbone structure of many hemicelluloses is acetylated, which presents a challenge when the objective is to convert corresponding polysaccharides to fermentable sugars or else recover hemicelluloses for biomaterial applications. Carbohydrate esterases (CE) can be harnessed to overcome these challenges. Methods Enzymes from different CE families, AnAcXE (CE1), OsAcXE (CE6), and MtAcE (CE16) were compared based on action and position preference towards acetyl-4-O-methylglucuronoxylan (MGX) and acetyl-galactoglucomannan (GGM). To determine corresponding positional preferences, the relative rate of acetyl group released by each enzyme was analyzed by real time 1H NMR. Results AnAcXE (CE1) showed lowest specific activity towards MGX, where OsAcXE (CE6) and MtAcE were approximately four times more active than AnAcXE (CE1). MtAcE (CE16) was further distinguished by demonstrating 100 times higher activity on GGM compared to AnAcXE (CE1) and OsAcXE (CE6), and five times higher activity on GGM than MGX. Following 24 h incubation, all enzymes removed between 78 and 93% of total acetyl content from MGX and GGM, where MtAcE performed best on both substrates. Major conclusions Considering action on MGX, all esterases showed preference for doubly substituted xylopyranosyl residues (2,3-O-acetyl-Xylp). Considering action on GGM, OsAcXE (CE6) preferentially targeted 2-O-acetyl-mannopyranosyl residues (2-O-acetyl-Manp) whereas AnAcXE (CE1) demonstrated highest activity towards 3-O-acetyl-Manp positions; regiopreference of MtAcE (CE16) on GGM was less clear. General significance The current comparative analysis identifies options to control the position of acetyl group release at initial stages of reaction, and enzyme combinations likely to accelerate deacetylation of major hemicellulose sources.
|
|
