Joining secondary

As noted above, the two lobes have very similar folding. This is only to be expected given their high (—40%) sequence identity. The differences, at the level of polypeptide folding, are confined primarily to small insertions and deletions in the loops that join secondary structure elements. These are almost all located on the molecular surface and do not disturb the basic structure—indeed 90% of the main chain atoms of the N-lobe of human lactoferrin can be superimposed on equivalent atoms in the C-lobe with a root-mean-square deviation of only —1.2 A. The agreement would be even closer were it not for the small difference in the closure of the two domains, described above. 

Another interesting variation in the clustering of apical dendrites occurs in the cat sensorimotor cortex. There it has been shown by Fleischhauer (1974) that in the posterior sigmoid gyrus the apical dendrites of the layer 5 pyramidal cells frequently bifurcate soon after they emerge from the large cell bodies. The secondary dendritic branches then run obliquely for a short distance and at the level of layer 3 they join secondary branches from other apical dendrites to form dendritic clusters... 

Many aromatic aldehydes (having the -CHO group joined directly to the benzene ring) undergo polymerisation when heated with a solution of potassium cyanide in aqueous ethanol. Thus benzaldehyde gives benzoin, a compound of double function, since it contains both a secondary alcoholic and a ketonic... 

Figure 2.8 Adjacent antiparallel P strands are joined by hairpin loops. Such loops are frequently short and do not have regular secondary structure. Nevertheless, many loop regions in different proteins have similar structures, (a) Histogram showing the frequency of hairpin loops of different lengths in 62 different proteins, (b) The two most frequently occurring two-residue hairpin loops Type I turn to the left and Type II turn to the right. Bonds within the hairpin loop are green, [(a) Adapted from B.L. Sibanda and J.M. Thornton, Nature 316 170-174, 1985.]...

Alfred Werner. His theory of coordination chemistry was published in 1893 when Werner was 26 years old. In his paper Werner made the revolutionary suggestion that metal ions such as Co3+ could show two different kinds of valences. For the compound Co(NH3)eCI3, Werner postulated a central Co3+ ion joined by "primary valences" (ionic bonds) to three Cl- ions and by "secondary valences"... 

Overmolding is the process by which two different materials are joined into one assembly without using secondary operations like gluing or welding. In case the materials are chemically compatible, chemical bonds may form between them and so mechanical interlocks are not required. There are two common techniques of overmolding—insert molding and multiple-shot injection molding. 

The Si04 tetrahedra can be arranged into several silicate units, e.g. squares, six-or eight-membered rings, called secondary building blocks. Zeolite structures are then built up by joining a selection of building blocks into periodic structures. 

The essential distinction between the approaches used to formulate and evaluate proteins, compared with conventional low molecular weight drugs, lies in the need to maintain several levels of protein structure and the unique chemical and physical properties that these higher-order structures convey. Proteins are condensation polymers of amino acids, joined by peptide bonds. The levels of protein architecture are typically described in terms of the four orders of structure [23,24] depicted in Fig. 2. The primary structure refers to the sequence of amino acids and the location of any disulfide bonds. Secondary structure is derived from the steric relations of amino acid residues that are close to one another. The alpha-helix and beta-pleated sheet are examples of periodic secondary structure. Tertiary... 

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