Complex carbohydrates, structure

S. Ravaud, X. Robert, H. Watzlawick, R. Haser, R. Mattes, and N. Aghajari, Trehalulose synthase native and carbohydrate complexed structures provide insights into sucrose isomerization, /. Biol. Chem., 282 (2007) 28126-28136. 

MEMBRANES ARE COMPLEX STRUCTURES COMPOSED OF LIPIDS, PROTEINS, CARBOHYDRATES... 

Sweetness is a quality that defies definition, but whose complexity can be appreciated merely by examining the molecular structures of those compounds that elicit the sensation. They come in all molecular shapes and sizes, and they belong to such seemingly unrelated classes of compounds as aliphatic and aromatic organic compounds, amino acids, peptides and proteins, carbohydrates, complex glycosides, and even certain inorganic salts. 

CORNU A, BESLE J M, MOSONi p, GRENET E (1994) Lignin-carbohydrate complexes in forages structure and consequences in the ruminal degradation of cell-wall carbohydrates. Reprod Nutr Dev. 34 385-98. 

Phenazines — These are dibenzopyrazine derivatives with fnnctional groups (hydroxy-, carboxy-) at C, and Cg and an oxygen or methyl gronp at Nj and N,o. There are also more complex structures, substituted phenazines, terpenoidal, and carbohydrate-containing phenazines and phenazines derived from saphenic acid. ... 

Fraction Fla was chosen for structural purposes due to its better solubility in water and the absence of Xyl. In order to remove noncovalently associated protein, fraction Flap was submitted to sequential shaking cycles with a mixture of chloroform-buthanol, as indicated by Sevag and described by Staub [17]. The fraction was also treated with trichloroacetic acid. In both procedures, coprecipitation of carbohydrate and protein was observed, suggesting strong linkages and a more complex structure. Fla as was submitted to mild acid hydrolysis yielding Flas and Flap (Table VI). 

All compounds have a precise and often highly specific function to fulfil, and in animals many of them are concerned also with the protection of the body against agents of disease. The problems of immunity and of enzyme systems involve the consideration of protein-carbohydrate complexes so that structural studies in the group now need to be undertaken seriously. 

Simultaneous to the understanding of some basics of hydrothermal carbonization using pure carbohydrate models, the synthesis of hydrothermal carbon materials using raw biomass was continued. It has been analyzed whether complex biomass - hy-drothermally carbonized - can also be directed to complex structural motifs with distinct surface polarities. Ideally, for this purpose one can use the structures and functionalization components already included in the biomass. We specifically selected waste biomass for material synthesis, starting products which are known to be hard to use otherwise, rich in ternary components, and applied different HTC conditions [29]. That way, one can avoid the food-raw materials competition, a prerequisite we regard as crucial for the development of a fully sustainable chemistry. 

In the PPA-a-AI 1 complex, a flexible loop of the enzyme, which would normally contact the substrate, is pushed outward to allow entry of the inhibitor, and one of the key aspartate residues is held in a conformation similar to that observed in the free enzyme. Therefore, some changes relative to the carbohydrate complex are required in order to accommodate the inhibitor. The structurally mimetic interactions within the catalytic site are supplemented by other specific protein-protein interactions, with a substantial buried surface area at the interface, involving 50 residues of the enzyme [171]. 

Many proteins have nonprotein components these may be metal ions, carbohydrates, lipids, or complex structures such as heme. 

The basic units of carbohydrates are the monosaccharides or simple sugars. These may be assembled into more complex structures such as disaccharides, polysaccharides, glycoproteins, and glycolipids. Carbohydrates serve as energy sources, energy reservoirs, structural components, and for cellular communication. 

Structure and Properties of the Lignin—Carbohydrate Complex Polymer as an Amphipathic Substance... 

Occurrence in nature of branched-chain carbohydrates has prompted interest in the syntheses of these complex structures and stimulated the preparation of analogues for biological evaluation. Consequently, new methods for the construction of these particular skeletons have been devised [1]. The use of carbohydrates as a cheap source of chiral starting materials [2-4] for the synthesis of complex, nonsugar molecules has prompted the emergence of new imaginative methods for formation of carbon-carbon bonds adapted to the particular reactivity of sugar moieties. 

The chemistry of enolates has provided excellent routes to highly complex structures, in particular in the total synthesis of natural products. Because of the highly oxygenated structures of carbohydrates, enolate formation could easily result in p-elimination of a suitably located oxygenated group (ethers, esters, and such) to provide enone. For these reasons, the chemistry of carbohydrate enolates has been poorly documented. 

The first theme of the book is biomolecular structure. We ll look carefully at the complex structures of proteins, carbohydrates, RNA, DNA, and many other substances. We ll not only examine in-depth their molecular architecture but also study the chemical properties that make life possible. 

Other bacterial coats. Archaebacteria not only have unusual plasma membranes that contain phytanyl and diphytanyl groups (Section A,3)608 but also have special surface layers (S-Iayers) that may consist of many copies of a single protein that is anchored in the cell membrane.609 The surface protein of the hypothermic Staphylothermus marius consists of a complex structure formed from a tetramer of 92-kDa rods with an equal number of 85-kDa "arms."610 611 S-layers are often formed not only by archaebacteria but also by eubacteria of several types and with quite varied structures.612 14 While many bacteria carry adhesins on pili, in others these adhesive proteins are also components of surface layers.615 Additional sheaths, capsules, or slime layers, often composed of dextrans (Chapter 4) and other carbohydrates, surround some bacteria. 

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