Linear sequence

Most reactions in cells are carried out by enzymes [1], In many instances the rates of enzyme-catalysed reactions are enhanced by a factor of a million. A significantly large fraction of all known enzymes are proteins which are made from twenty naturally occurring amino acids. The amino acids are linked by peptide bonds to fonn polypeptide chains. The primary sequence of a protein specifies the linear order in which the amino acids are linked. To carry out the catalytic activity the linear sequence has to fold to a well defined tliree-dimensional (3D) stmcture. In cells only a relatively small fraction of proteins require assistance from chaperones (helper proteins) [2]. Even in the complicated cellular environment most proteins fold spontaneously upon synthesis. The detennination of the 3D folded stmcture from the one-dimensional primary sequence is the most popular protein folding problem. 

Figure C2.5.1. The 3D native stmcture of haemoglobin visualized using RasMol 2.6 [8], The linear sequence of amino acids of haemoglobin is given below tire figure.

Line notations represent the structure of chemical compounds as a linear sequence of letters and numbers. The lUPAC nomenclature represents such a kind of line notation. However, the lUPAC nomenclature [6] makes it difficult to obtain additional information on the structure of a compound directly from its name (see Section 2.2). 

The primary stmcture of prolactin consists of 199 amino acids in a linear sequence (see Hormones, ANTERIORPITUITARY-LIKE HORMONES). Similar to growth hormone (16), the tertiary stmcture of prolactin is thought to be arranged in a bundle of four a-heHces (17). Detailed reviews of the... 

In the second general method, the amine (16), known as Grewe diamine, is the paradigm intermediate onto which the thia2o1ium ring is constmcted. Differences occur only in the raw materials and methods used for the manufacture of the diamine. The same end of the linear sequence is universally practiced by all large manufacturers. 

The DNA molecules in each cell of an organism contain all the genetic information necessary to ensure the normal development and function of that organism. This genetic information is encoded in the precise linear sequence of the nucleotide bases from which the DNA is built. DNA is a linear molecule while its diameter is only about 20 A, if stretched out its length can reach many millimeters. This means that concentrated solutions of DNA can be pulled into fibers in which the long thin DNA molecules are oriented with their long axes parallel. 

The structure of any molecule is a unique and specific aspect of its identity. Molecular structure reaches its pinnacle in the intricate complexity of biological macromolecules, particularly the proteins. Although proteins are linear sequences of covalently linked amino acids, the course of the protein chain can turn, fold, and coil in the three dimensions of space to establish a specific, highly ordered architecture that is an identifying characteristic of the given protein molecule (Figure 1.11). 

Although electrons move from more negative to more positive reduction potentials in the electron transport chain, it should be emphasized that the electron carriers do not operate in a simple linear sequence. This will become evident when the individual components of the electron transport chain are discussed in the following paragraphs. 

The backbone of polypeptides and, more generally, proteins is made up of a linear sequence of amino acids. 

The structural units may be connected together in any conceivable pattern. In the simplest of all polymers, the linear polymers, the structural units are connected one to another in linear sequence. Such a polymer may be represented by the type formula... 

The term branched refers to the over-all pattern of the polymer molecule as depicted schematically above, rather than to the nature of the structural unit. The 1,2 unit of butadiene, for example, may be regarded as branched inasmuch as it possesses a pendant vinyl group, but the polymer should be considered linear nevertheless, provided that these units are connected in a single linear sequence. 

In the usual chemical formulas written for chain polymers the sue-cessive units are projected as a co-linear sequence on the surface of the sheet of paper. This form of representation fails to convey what is perhaps the most significant structural characteristic of a long polymer chain, namely, its capacity to assume an enormous array of configurations. This configurational versatility is a consequence of the considerable degree of rotational freedom about single bonds of the chain. In the simple polymethylene chain, for example, the conventional formula... 

It is appropriate to consider first a hypothetical chain consisting of linkages of length I joined in linear sequence without any restrictions whatever on the angles between successive bonds. Thus, for the case to be discussed d may assume all values from 0 to tt with equal probability and 0 is likewise unrestricted. Only the bond length is fixed. Of... 

This result is the analog of the swelling equation (XIII-39) for a network. It rests principally on the assumption that the intramolecular interactions of the segments with one another are the same as would obtain for a cloud of particles, not connected to each other, but having the same radial distribution as the average radial density distribution occurring for the molecule made up of a linear sequence of particles. 

Minimize overall number of steps and stages preferably using nested MCRs as far as possible as the main strategy in a synthetic plan to a complex target. Overall convergence is maximized dramatically if a plan contains a late-stage MCR that involves components that are themselves terminal products of independent parallel linear sequences. 

This system displays a two-enzyme kinetic model in which bioconversion is controlled by the interaction between the two reactions and the mass transfer. This situation offers a more realistic model for the conditions occurring in vivo, in which some pathways of intermediary metabolism consist of linear sequences of reactions. These pathways take place in highly organized compartments. 

The overall yield was about 12% over a longest linear sequence of 23 steps and about 40 steps total. The major disconnections are illustrated below. 

The overall yield of 1 was improved to 10% in 16 chemical steps with the longest linear sequence as ten steps. 

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