Three-armed structure

Figure 15.17 The three-dimensional structure of an intact IgG. Hinge regions connecting the Fab arms with the Fc stem are relatively flexible, despite the presence of disulfide bonds in this region linking the heavy and light chains. Carbohydrate residues that bridge the two Ch2 domains are not shown. (Courtesy of A. McPherson and L. Harris, Nature 360 369-372, 1992, by copyright permission of Macmillan Magazines Limited.)...

IgG antibody molecules are composed of two light chains and two heavy chains joined together by disulfide bonds. Each light chain has one variable domain and one constant domain, while each heavy chain has one variable and three constant domains. All of the domains have a similar three-dimensional structure known as the immunoglobulin fold. The Fc stem of the molecule is formed by constant domains from each of the heavy chains, while two Fab arms are formed by constant and variable domains from both heavy and light chains. The hinge region between the stem and the arms is flexible and allows the arms to move relative to each other and to the stem. 

It was an interesting idea to create the giant tube-like structures 46 capped with a Lewis acid center by the homologation reaction of 42 with dimethylsulfoxonium methylide and their deboronation to the three-armed star polymethylene polymers 47 incorporating a m, r-l,3,5-trisubstituted cyclohexane core (Scheme 12) <2003JA12179, 20010L3063>. 

Lang M, Wong RP, Chu C-C (2002) Synthesis and structural analysis of functionalized poly (s-caprolactone)-based three arm star polymers. J Polym Sci A Polym Chem 40 1127-1141... 

FIGURE 27-13 Three-dimensional structure of yeast tRNAphe deduced from x-ray diffraction analysis. The shape resembles a twisted L. (a) Schematic diagram with the various arms identified in Figure... 

The synthesis and phase structure of a three-arms—nine-chain liquid crystal (17) based on pyrogallol and phloroglucinol has been reported (61), as has a complexing agent for amino acids in water (18) (62) (Fig. 1). 

Much larger planar periodic structures have been obtained by symmetrised interactions of DX-type sticky DNA stars. Figure 16a, d shows three-arm [72] and four-arm [73] DNA stars constructed by paired double helices both with N = 22 long arms and N = 4 long sticky terminals. These structures are symmetric for, respectively, threefold and fourfold rotations but they are not mirror-symmetric. The lack of mirror symmetry favors deviations of the constructs from perfect flatness the center of the star may not be in the same plane as the arm tips. For this reason, in both cases the DNA constructs have been designed so that their arms stick end-to-end in such a way that each star interacts only with stars turned upside... 

Each tRNA has a cloverleaf secondary structure containing an anticodon arm, a D (or DHU) arm, a T or TTC arm, and an amino acid acceptor stem to which the relevant amino acid becomes covalently bound, at the 3 OH group. Some tRNAs also have a variable (or optional) arm. The three-dimensional structure is more complex because of additional interactions between the nucleotides. 

FIG. 4.1. Molecular structure of (a) 8-tris-hydroxyquinoline A1 ("Alqj ), (b) three-armed star (3-AS) 4.4 .4 -tris[N-(3-methoxyphenyl)-N-phenylamine-triphenylamine], and (c) N,N -diphenyl-N,N -bis(3-methylphenyl)-l,r-biphenyl-4,4 diamine (TPD) [68]. 

Fig. 20.8. Three-dimensional structure of phenylalanine specific tRNA from yeast. Watson-Crick type base pairs indicated by slabs, nonstandard base-base interactions that stabilize the tertiary structure are denoted a to h. Invariant and semi-invariant nucleotides are shaded, the four double helical regions are indicated by a a-(amino add) arm, Tarm, D arm, a.c. (anticodon arm [696]...

The structure of the FA eicosapentaenoic acid (EPA) bound to PPAR-d has been determined (PDB entry 3GWX) [35]. The ligand-binding pocket of PPAR-d assumes roughly a Y shape with each of the three arms approximately 12 A in length. One arm of the Y is composed of a mix of hydrophobic residues and polar residues and is capped by two residues from helix-12. This is the only arm of the Y that is substantially polar in character. Another arm of the Y is composed of hydrophobic residues and is sealed by the last residue of helix-1, and the loop between helices-1 and -2. The third arm of the Y-shaped pocket is composed mainly of hydrophobic residues with a few polar residues. The interior of the ligand-binding pocket is accessible via a channel that is exposed to solvent [35]... 

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