Main structure

Cellulose (-C,H,0-) Framework of all plant life, as the main structural... 

Polypeptide chains are folded into one or several discrete units, domains, which are the fundamental functional and three-dimensional structural units. The cores of domains are built up from combinations of small motifs of secondary structure, such as a-loop-a, P-loop-p, or p-a-p motifs. Domains are classified into three main structural groups a structures, where the core is built up exclusively from a helices p structures, which comprise antiparallel p sheets and a/p structures, where combinations of p-a-P motifs form a predominantly parallel p sheet surrounded by a helices. 

The phase relations, stoichiometry and structural chemistry of the metal borates have been extensively studied because of their geochemical implications and technological importance. Borates are known in which the structural unit is mononuclear (1 B atom), bi-, tri-, tetra- or penta-nuclear, or in which there are polydimensional networks including glasses. The main structural principles underlying the bonding in crystalline metal borates are as follows " ... 

Table 2 depicts an approach to the modification of biomass with a view to effecting necessary changes, structural or otherwise, in natural polymers. Conventionally, modifications [54-63] are effected mainly by two ways (1) mechanical and/or chemical modifications without destroying the main structural backbone, and (2) cleav-... 

In the Forth, Severn and many other suspension bridges, zinc coatings have an important function. The whole main structure is of steel and has been zinc-sprayed on the external surfaces, while the main cable and hanger ropes have been coated by continuous hot-dip galvanising. Case histories of galvanised multi-truss bridges cover more than 30 years. 

Most of the M3MeOF6 type compounds belong to the highest symmetry class, except for Na3NbOF6. The main structural characteristics of the M3MeOF6 type compounds are collected in Table 20. 

Among the different families of tantalum and niobium complex fluorides and oxyfluorides, the family of compounds with an X Me ratio equal to 6 is the largest. Table 22 presents the main structural characteristics of hexafluoroniobates and hexafluorotantalates. All known cases of niobium- and tantalum-containing formulary analogs have the same crystal structure type, at least at ambient temperature. 

Like the examples above, dihydroxyacetanilide epoxidase (DHAE) uses an olefin as the substrate for epoxidation. Its mechanism, however, is fundamentally different from those of cytochrome P450 or flavin-dependent enzymes. Dihydroxyacetanilide is an intermediate in the biosynthesis of the epoxyquinones LL-C10037a, an antitumor agent produced by the actinomycete Streptomyces LL-C10037 [75, 76], and MM14201, an antibiotic produced by Streptomyces MPP 3051 (Scheme 10.20) [77]. The main structural difference between the two antibiotics lies in the opposite stereochemistry of the oxirane ring. 

The frontal cortex consists of three main structures (i) motoric regions (including the Broca area and ocular areas), (ii) the prefrontal cortex, and (iii) the orbital cortex. The prefrontal cortex is associated with attention, arousal, and expectation, the orbital cortex with motivation. 

In summary, main structures involved in the action of psychostimulants can be divided into cortical (mainly prefrontal cortex) and subcortical (basal ganglia and related structures, LC and cerebellum) ones. Figure 1 gives a schematic overview of the connections between these structures, omitting the cerebellum due to lack of precise information. 

Lipoprotein fraction containing triglycerides and to a lesser degree cholesterol. VLDL is produced by the liver. The main structural protein connected to this lipoprotein class is apolipoprotein B. 

Figure 11 shows that the molecular weight distribution in the melt (presence of short chains) can account for the coexistence of two types of crystals in the absence of molecular orientation or at a slight stretching of the melt. However, there is a purely thermodynamic reason for the appearance of this main structural feature of samples crystallized under conditions of molecular orientation, even at high degrees of orientation, when virtually the whole distribution function is displaced into the region of /S > /3cr. 

Batsanov et al. 23) reacted sulfur with PtCU and PtBr2 by heating mixtures of the reactants in evacuated, sealed ampoules. At 100 -200°C after 12-24 h, sulfide chlorides PtCljS (1.70 < x < 2 0.6 s y < 3.35) and sulfide bromides PtBr S (1.87 < x 2.06 0.84 y s 1.80) were formed. The compositions depended on the initial PtX2 S ratio, and the temperature. At 320-350°C, loss of chlorine led to the compounds PtClS (1.7 y 1.9). According to their X-ray powder patterns, all of these products retained the main structural features of the original platinum halides. From considerations of molar volumes, the authors deduced the presence of polysulfide anions. 

Chitosan is the main structural component of crab and shrimp shells. Chitosan contains both reactive amino and hydroxyl groups, which can be used to chemically alter its properties under mild reaction conditions. Al-acyl chitosans were already reported as blood-compatible materials. UV irradiation grafting technique was utilized to introduce obutyrylchitosan (OBCS) onto the grafted SR film in the presence of the photosensitive heterobifunctional cross-linking agent. The platelet adhesion test revealed that films grafted on OBCS show excellent antiplatelet adhesion. 

The BaBPOs compound was first prepared and structurally characterized by Bauer [12]. Figure 21.2 shows the crystal structure of BaBPOs. Its structure is similar to all stillwellite-like compounds with the space group P322. Its main structural elements are spiral tetrahedral chains [001] built of three-membered rings. The contact between the BO4 tetrahedra that form the central part of these chains are reinforced by PO4 tetrahedra and thus [BPO5] heterotetrahedral chain complexes are produced. 

Carrageenan has long been considered to be a simple polymer of D-galacto-4-sulfate joined at carbons 1 and 3. While this unit is part of the main structural feature, recent work has disclosed additional fine points. Thus, carrageenan is known to be a mixture of components of varying viscosities and varying sensitivities to potassium. 

Hyaluronic acid and collagen are the two main structural components. The collagen is similar to that found in cartilage, consisting of three alpha-chains and known as type II collagen, although subtle differences are now recognized (Swann and Constable, 1972 Swann, 1980). 

This chapter focuses on the effects of humic substances present at the rhizo-sphere on plant growth and nutrient uptake. The main structural features of humic substances, their nutritional function, and the capacity to interact with plant metabolism are also presented. 

Pure aluminium lacks mechanical strength but has higher resistance to corrosion than its alloys. The main structural alloys used are the Duralumin (Dural) range of aluminium-copper... 

Because the only general review13 on these compounds in this Series dates back to 1946, it seems pertinent to recall the main structural features of these polysaccharides. (For extensive discussions on the structure and the physicochemical and biological properties of GAG, see Refs. 8,10, and 13-18.)... 

Phospholipids, which are one of the main structural components of the membrane, are present primarily as bilayers, as shown by molecular spectroscopy, electron microscopy and membrane transport studies (see Section 6.4.4). Phospholipid mobility in the membrane is limited. Rotational and vibrational motion is very rapid (the amplitude of the vibration of the alkyl chains increases with increasing distance from the polar head). Lateral diffusion is also fast (in the direction parallel to the membrane surface). In contrast, transport of the phospholipid from one side of the membrane to the other (flip-flop) is very slow. These properties are typical for the liquid-crystal type of membranes, characterized chiefly by ordering along a single coordinate. When decreasing the temperature (passing the transition or Kraft point, characteristic for various phospholipids), the liquid-crystalline bilayer is converted into the crystalline (gel) structure, where movement in the plane is impossible. 

---