Structure ringlike

Centrosomes, also called the microtubule organizing centre, are protein complexes that contain two cen-trioles (ringlike structures) and y- tubulin. They serve as nucleation points for microtubular polymerization and constrain the lattice structure of a microtubule to 13 protofilaments. They are responsible for organizing the mitotic spindle during mitosis. 

Berendschot TTJM and van Norren D (2006), Macular pigment shows ringlike structures, Invest. Ophthalmol. Visual Sci. 47 709-714. 

To the west of this ring-like structure, on the boundary of the area, there are several enrichment local anomalies of Ti around enrichment zones of Zn and Pb. In the Zyryanovsk region all the main deposits, are surrounded by a ring-shaped zone of Ti enrichment of 5-10 km in width The internal part of the area of the ringlike anomaly mainly comprises a depletion zone of about 150 km. ... 

When mother liquor from an enzyme recrystallization was stained with sodium silicotungstate at pH 7, most of the forms were indistinguishable from the 65-A structures of Fig. 2. However, there were also a few round objects 130-140 A in diameter, most of which appeared to have a central cavity (Fig. 3a). When the pH was lowered to 6, many more of the larger objects, both solid and with cavities, were observed (Fig. 3b), and at pH 5 nearly all of the forms were of this larger type (Fig. 3c). Uranyl acetate stained preparations at pH 4 also showed the 130-140-A objects almost exclusively, both with and without the ringlike appearance (Fig. 3d). These large forms may represent a specific molecular intermediate with which single enzyme particles and the crystals are in equilibrium. As the pH is lowered, the equilibrium between the 65-A and the 130-140-A structures is shifted in favor of the latter 13). 

Figure 30 Symmetrical concentric-ring barrel structure (left) confined in the ringlike surface and a unit cell with one lamellar period L (right).

P. S. Shenkin, D. L. Yarmush, R. M. Fine, H. Wang, and C. Levinthal, Biopolymers, 26, 2053 (1987). Predicting Antibody Hypervariable Loop Conformation. I. Ensembles of Random Conformations for Ringlike Structures. 

The oxalate anion, OOC—COO", provides two coordinating groups for bonding with metals, and the resulting complex is termed a chelate because of the ringlike structure that is formed ... 

C. Levinthal. Predicting antibody hypervariable loop conformation. I. Ensembles of random conformations for ringlike structures. Biopolymers. 1987, 26, 2053-2085. 

Various pathogenic bacteria inject proteins into host cells via a complicated syringe-like machine composed of more than 20 different proteins. This type III secretion apparatus, shown in Figure 16-24, has ringlike components embedded in both the inner and outer membranes of the bacterial cell wall and a hollow needlelike structure (pilus) that projects... 

DNA polymerase III is an asymmetric dimer. It contains two copies of the core polymerase, snbnnits a, e, and 0. The a subunit has polymerase activity while e is a 3 — 5 proofreading exonuclease. A 2 subunit is associated with one arm and a (55 i/)2 subunit with the other. These serve as the clamp-loading complex. The P2 subunits form ringlike structures that serve as sliding DNA clamps. 

But with polymers, other types of bonding can occur. In certain solvents, and at higher concentrations, poly(7-benzyl-L-glutamates) do not form end-group associated ringlike entities but form laterally arranged bundlelike structures. Mesomorphous structures such as formed by certain stiff low-molar-mass molecules are produced (see also Section 5.5). 

Fig. 2 Transmission electron micrograph of karyoskeletal protein-enriched fraction prepared from Drosophila embryos. The main panel shows a nucleuslike structure, bounded by a peripheral lamina (L) Inset Higher magnification showing tangential section through the periphery of karyoskeletal protein structure as shown in the main panel. Nuclear pore complex remnants can be readily appreciated as small ringlike structures.

Fig. 5. Schematic representation of the doubling in the amount of DNA in a replication unit according to a model of circular replicons. The model assumes that the replicon is a ringlike structure (a). Replication will result In the production of two rings (b), which would normally separate with the separation of chromatids during division. However, because of the close association of the rings, mistakes in the replication process could allow the end-to-end attachment of two identical rings resulting in the tandem Incorporation of a duplicated gene (c). (From Keyl. 1965. Experientia, 21 191-193.)...

Saccharides appear in the form of ringlike structure. For example, the ringlike structure of glucose is as follows ... 

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