Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

A -terminus

The groups at the termini of the 1,4-pentadiene system also affect the efficiency and direction of the the di-7c-methane reaction. The general trend is that cyclization oceurs at the diene terminus that best stabilizes radical character. Thus, a terminus substituted with aryl groups will cyclize in preference to an unsubstituted or alkyl-substituted terminus ... [Pg.778]

It would be complicating if not impossible having to obtain sequence information from such a spectrum without rules to follow. [138-141,146,147] The most abundant ions obtained from the fragmenting peptide ion usually belong to six series named a, b, and c if the proton (charge) is kept in the A-terminus or x, y, and z, respectively, where the proton is located in the C-terminal part. Within each se-... [Pg.399]

A frequently encountered modification is the conversion of the C-terminal carboxyl into an amide. This is represented as Phe-NH2, for example, which must be considered carefully, and not be interpreted as an indication of the A-terminus (see Section 13.2). [Pg.503]

By convention, the left-hand amino acid in this sequence is the one with a free amino group, the A-terminus, and the right-hand amino acid has the free carboxyl, the C-terminus. Thus, Ser-Phe-Ala is different from Ala-Phe-Ser, and represents a quite different molecule. Sometimes, the termini identities are emphasized by showing H- and -OH H- represents the amino group and -OH the carboxyl group. Some peptides are cyclic, and this convention can have no significance, so arrows are incorporated into the sequence to indicate peptide bonds in the direction CO— NH. As sequences become longer, one-letter abbreviations for amino... [Pg.504]

Termination Eventually, the two replication forks of the circular E. coli chromosome meet at a terminus region containing multiple copies of a 20 bp sequence called Ter (for terminus) (Fig. 25-17a). The Ter sequences are arranged on the chromosome to create a sort of trap that a replication fork can enter but cannot leave. The Ter sequences function as binding sites for a protein called Tus (terminus utilization substance). The Tus-Ter complex can arrest a replication fork from only one direction. Only one Tus-Ter complex functions per replication cycle—the complex first encountered by either... [Pg.962]

Suppose that we have a point in the xy plane with coordinates x, and y, as shown in the diagram. This point defines a vector, r, between itself and the origin. Now suppose that this vector is rotated through an angle 0 so that a new vector, r2, is produced with a terminus at the point x2 and y2. We now inquire about how the final coordinates, x2 and y2, are related to the original coordinates, X and yu and the angle 9. The relationship is not difficult to work out. When the x component of rh xh is rotated Dy 0, it becomes a vector x which has an x component of x cos 6 and a y component of X sin 9. [Pg.71]

The electrophilic one-carbon species can be an aldehyde, ketone, carboxylic acid, phosgene, thiophosgene, carbonyl diimidazole (CDI), etc., and the reaction essentially involves condensation with a 1,5-dinucleophile. The 1,5-dinucleophile invariably contains at least one heteroatom at a terminus, and more often than not two, so that the cyclization always involves the formation of at least one bond between carbon and a heteroatom. [Pg.1073]

Exercise 25-25 Indicate the steps that would be necessary to attach each of the amino acids listed to the A/-terminus of a peptide chain. Assume that any side-chain functions in the peptide are suitably protected, but do not assume that the amino acids will couple with the peptide without suitable protection of their functional groups, a. lysine b. aspartic acid c. cystine d. serine... [Pg.1247]

This finding indirectly supports Bjork s hypothesis regarding the existence of multiple sites of attachment of substrate to enzyme. The absence of the 5 -monophosphoryl group is felt by the enzyme even though the hydrolytic site is removed from the a terminus by several monomers. [Pg.322]

Venom exonuclease has been widely used for the determination of the a terminus in oligonucleotides. The normal procedure was to divide the dephosphorylated sample into two parts and digest one part with venom exonuclease. The a terminus appeared as a nucleoside the rest of the chain was degraded to 5 -mononucleotides. The other part of the dephosphorylated chain was degraded with spleen a-exonuclease. In this case the w terminus appeared as a nucleoside, the rest of the chain as 3 -mononucleotides. [Pg.326]

As the quality of venom exonuclease improved, more difficult tasks were tackled. The a terminus was identified in tobacco mosaic virus (72). It required finding one nucleoside among 6400 nucleotides. Venom exonuclease was also used for identification of both terminals in chains bearing 3 -monophosphate (IS, 73). The a terminus appears as a nucleoside, the wide application because it required large amounts of highly purified enzyme. The recent finding that 3 -monophosphates are better substrates at pH 6 than 9 (29) is likely to increase the use of this method. [Pg.326]

Roblin (74) used venom exonuclease to identify the a terminus in RNA isolated from bacteriophage R-17. The RNA was degraded with alkali and the mixture chromatographed according to Tomlinson and Tener (69). The terminal appeared at the place in the pattern that corre-... [Pg.326]

Ribosomes contain a channel in which a strand of mRNA binds. During translation, a ribosome slides along a strand of mRNA from the 5 end to the 3 end (Scheme 6.5). As the mRNA code is read, the ribosome synthesizes a new protein from the A-terminus to the C-terminus. The protein is prepared from amino acids that are delivered by another form of RNA called tRNA, which is described in the next subsection. Multiple ribosomes can simultaneously translate a single mRNA strand. [Pg.128]

In another way, that from which a predicate is taken, though outside the subject, is nevertheless from a certain point of view in the subject of which it is predicated. And if it is from the viewpoint of the principle, then it is predicated as an action for the principle of action is in the subject. But if it is from the viewpoint of a terminus, then it will be predicated as a passion for a passion is terminated in the subject which is being acted upon...16... [Pg.8]


See other pages where A -terminus is mentioned: [Pg.419]    [Pg.3]    [Pg.609]    [Pg.623]    [Pg.623]    [Pg.7]    [Pg.283]    [Pg.289]    [Pg.57]    [Pg.154]    [Pg.155]    [Pg.219]    [Pg.63]    [Pg.504]    [Pg.504]    [Pg.511]    [Pg.514]    [Pg.558]    [Pg.56]    [Pg.113]    [Pg.253]    [Pg.232]    [Pg.880]    [Pg.327]    [Pg.679]    [Pg.565]    [Pg.512]    [Pg.512]    [Pg.8]    [Pg.9]    [Pg.407]    [Pg.407]    [Pg.407]    [Pg.27]   


SEARCH



Terminus

© 2024 chempedia.info