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Biopolymers
Published in Mihai V. Putz, New Frontiers in Nanochemistry, 2020
Lorentz Jäntschi, Sorana D. Bolboacă
With few exceptions (such as is deoxyribose, H-(C=O)-(CH2)-(CHOH)3-H, C3O4H10) monosaccharides have the molecular formula (CH2O)n, where n ranges from 2 (only one with n = 2, diose, H-(C=O)-(CH2)-OH, C2O2H4) to usually 7 (n = 3 triose, n = 4 tetrose, n = 5 pentose, n = 6 hexose, n = 7 heptose). The molecular structure of a monosaccharide can be written as H(CHOH)x(C=O)(CHOH)yH, where x + y + 1 = n to have (CH2O)n as the molecular formula. The most important monosaccharide, glucose (depicted as a monomeric unit in Figure 2.8), is a hexose. Examples of heptoses include the ketoses mannoheptulose and sedoheptulose. Monosaccharides with eight or more carbons are rarely observed as they are quite unstable. In the next table are given the monosaccharides for n from 3 to 6 (see Table 2.3). From n = 5, the monosaccharides are stable also in their cyclic tautomeric form (see Figure 2.9), the lactol being prevalent in nature against aldose, while smaller ones (e.g., n = 3 and n = 4) may cyclize by dimerization (when resulted cyclic monosaccharides have n = 6, and n = 8, respectively, see Figure 2.10).
Biomolecules and Tissue Properties
Published in Joseph W. Freeman, Debabrata Banerjee, Building Tissues, 2018
Joseph W. Freeman, Debabrata Banerjee
Proteoglycans have a protein core connected to multiple glycosaminoglycan (GAG) chains that are covalently bonded to the protein core, Figure 3.15c. GAGs are long, unbranched polysaccharides consisting of a repeating disaccharide unit. The disaccharide unit consists of an N-acetyl-hexosamine and a hexose or hexuronic acid, either or both of which may be sulfated; hexoses include glucose, fructose, and galactose. Using a link protein several proteoglycans can bind together into larger structures (Figures 3.15a and b). The combination of the sulfate group and the carboxylate groups of the uronic acid residues gives them a very high density of negative charge. This helps them bring water to tissues. In cartilage, the large aggregating proteoglycans aggrecan and versican contribute 50% to 85% of the proteoglycans in the tissue. Small proteoglycans like biglycan and decorin contribute less than 10% of total proteoglycans.
Carbohydrates and Nucleic Acids
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
An aldose is a polyhydroxy aldehyde and a ketose is a polyhydroxy ketone. A hexose is a six-carbon sugar and a pentose is a five-carbon sugar. A pyranose is the cyclic hemiacetal or hemiketal form of the sugar that exists in a six-membered pyran ring. Therefore, an aldopyranose is a polyhydroxy aldehyde in pyranose form. A furanose is the cyclic hemiacetal or hemiketal form of the sugar that exists in a five-membered tetrahydrofuran ring. Therefore, a ketofuranose is a polyhydroxy ketone in furanose form. What is an example of an aldohexose, a ketohexose, an aldopyranose, and a ketofuranose?
Valorization of hexoses into 5-hydroxymethylfurfural and levulinic acid in acidic seawater under microwave hydrothermal conditions
Published in Environmental Technology, 2022
Yuchao Shao, Jiansong Chen, Xiaodong Ding, Wenjing Lu, Dongsheng Shen, Yuyang Long
The conversion of hexoses (fructose and glucose) in acidic seawater under MHT conditions was explored. The differences between fructose and glucose conversion were ascribed to the different activation energies (56.721 and 88.594 kJ mol−1 for fructose and glucose, respectively). Less value-added products (HMF and/or LA) were obtained from glucose compared with fructose due to the discrepancy in activation energy and undesirable humins formation. Furthermore, the MHT conditions affected the HMF and LA yields. A possible hexose conversion mechanism was proposed, showing that up to 60% of fructose carbon could be converted into HMF and/or LA, while 47% of glucose carbon achieved the same conversion under the optimal MHT conditions in acidic seawater. These results provide a reference for the biorefinery industry.
A Review on the Application of Starch as Depressant in Iron Ore Flotation
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Swagat S. Rath, Hrushikesh Sahoo
Starch is an energetic vegetative reserve photosynthesized by plants and stored in the cereals, fruits, roots tubers, and legumes in the range of 25–90% (De Ojogbo, Blanchard and Mekonnen 2018; Sousa et al. 2017). It is a natural semicrystalline polymer under the class of homopolysaccharides. Its simple chemical representation is (C6H10O5)n, where “n” represents the units of aldo-hexose, a monosaccharide. Starch is composed of two types of α-D-glucan chains, namely amylose and amylopectin. The other minor components are proteins, fatty acids, phosphorus, and some inorganic contaminants. Amylose is a linear glucose chain attached by α-1,4 glucosidase bond, whereas amylopectin is a branched glucose chain with branching at α-1,6 position (De Sousa et al. 2017). The polymerization index “n,” and hence, the molecular weight of starch and the ratio between the number of amylopectin and amylose species vary in a wide range. Figure 1 presents the structures of amylopectin and amylose chains.
Modeling of growth kinetics for an isolated marine bacterium, Oceanimonas sp. BPMS22 during the production of a trypsin inhibitor
Published in Preparative Biochemistry and Biotechnology, 2018
B. S. Harish, Kiran Babu Uppuluri
Effects of various carbon sources on the growth and protease inhibitor production were evaluated (Figure 2B). Glucose was selected as the best carbon source for the growth and production of PI. The bacterium was unable to grow when pentose sugar xylose was used as sole carbon source. This may be due to the absence of specific transporter in the cells, or the bacterium was unable to produce xylose utilizing enzymes.[34] The growth of Oceanimonas sp. BPMS22 was less in galactose-containing medium with good protease inhibitor activity. Krispin et al. observed Bacillus subtilis growth in neither xylose nor galactose as sole carbon source initially. This is due to the lack of an arabinose transporter, AraE which is responsible for the transportation of both xylose and galactose. But the same strain was easily mutated and quickly adapted to galactose.[35] Similarly, Oceanimonas BPMS22 may also lack xylose transporters. Protease inhibitor production was more when hexose sugars were used such as glucose and galactose. But the use of the disaccharide, lactose showed very less protease inhibitor activity. This may be due to the induction of protease production instead of protease inhibitor. Several reports confirmed the enhanced production of protease when lactose was used.[36,37]