Single-stranded

Figure C2.14.1. Diagram of a fragment of a folded RNA polymer, the QP replicase MDV-1 [176]. Note the various stmctural features stems closed with a loop ( hairjDins ), bows, and single strands.

In addition to conventional applications in conducting polymers and electrooptical devices, a number of recent novel applications have emerged. Switching of DNA electron transfer upon single-strand/double-strand hybridization fonns the basis for a new medical biosensor teclmology. Since the number of base pairs of length 20... 

Not all DNAs are double helices duplex DNA) Some types of viral DNA are single stranded and even a few DNA triple and quadruple helices are known... 

Transfer RNA (tRNA) Transfer RNAs are relatively small nucleic acids containing only about 70 nucleotides They get their name because they transfer ammo acids to the ribosome for incorporation into a polypeptide Although 20 ammo acids need to be transferred there are 50-60 tRNAs some of which transfer the same ammo acids Figure 28 11 shows the structure of phenylalanine tRNA (tRNA ) Like all tRNAs it IS composed of a single strand with a characteristic shape that results from the presence of paired bases m some regions and their absence m others... 

Section 28 14 The nucleotide sequence of DNA can be determined by a technique m which a short section of single stranded DNA is allowed to produce its complement m the presence of dideoxy analogs of ATP TTP GTP and CTP DNA formation terminates when a dideoxy analog is incorporated into the growing polynucleotide chain A mixture of polynucleotides dif fermg from one another by an incremental nucleoside is produced and analyzed by electrophoresis From the observed sequence of the comple mentary chain the sequence of the original DNA is deduced... 

Polymers that soften or melt and then solidify and regain their original properties on cooling are called thermoplastic. A thermoplastic polymer is usually a single strand of linear polymer with few if any cross-links. 

Pig. 7. The PGR reaction, showiag amplification of a sequence located between two primers where ( ) represents a primer, (—) a single strand of DNA,... 

Fig. 9. Mutagenesis by a synthetic oligonucleotide of a cloned sequence available in single-stranded form (a) single-stranded M13 template containing uracil (U) residues (b) double-stranded product, uracil residues are not mutagenic (c) strong selection for M13 phages containing mutation of interest (23).

The oligonucleotide population is then hybridized to single-stranded DNA and primed synthesis is carried out as described above. 

A Macromolecular Division of lUPAC was created in 1967, and it created a permanent Commission on Macromolecular Nomenclature, parallel to the other nomenclature commissions. The Commission over the years has issued recommendations on basic definitions, stereochemical definitions and notations, stmcture-based nomenclature for regular single-strand organic polymers and regular single-strand and quasisingle-strand inorganic and coordination polymers, source-based nomenclature for copolymers, and abbreviations for polymers. AH of these are coUected in a compendium referred to as the lUPAC Purple Book (99). 

Recommendations on additional aspects of macromolecular nomenclature such as that of regular double-strand (ladder and spiro) and irregular single-strand organic polymers continue to be pubHshed in I ure and Applied Chemistty (100,101). Recommendations on naming nonlinear polymers and polymer assembHes (networks, blends, complexes, etc) are expected to be issued in the near future. 

More recendy, analogues having peptide-based linkers have been explored. A thymidine glycine copolymer (28) has been synthesized in high yield and forms a stable duplex with its cognate single-stranded partner (46). 

Definitions of the commonly measured tensile properties are as follows Unear density (tex) is the weight in grams of 1000 m of yam. Tenacity is the tensile stress at break and is expressed in force-per-unit linear density of unstrained specimen, N /tex. Knot tenacity is the tensile stress required to mpture a single strand of yam with an overhand knot tied in the segment of sample between the testing clamps. It is expressed as force-per-unit linear density and is an approximate measure of the britdeness of the yam. Toop tenacity is the tensile stress required to mpture yam when one strand of yam is looped through... 

Cellular protein biosynthesis involves the following steps. One strand of double-stranded DNA serves as a template strand for the synthesis of a complementary single-stranded messenger ribonucleic acid (mRNA) in a process called transcription. This mRNA in turn serves as a template to direct the synthesis of the protein in a process called translation. The codons of the mRNA are read sequentially by transfer RNA (tRNA) molecules, which bind specifically to the mRNA via triplets of nucleotides that are complementary to the particular codon, called an anticodon. Protein synthesis occurs on a ribosome, a complex consisting of more than 50 different proteins and several stmctural RNA molecules, which moves along the mRNA and mediates the binding of the tRNA molecules and the formation of the nascent peptide chain. The tRNA molecule carries an activated form of the specific amino acid to the ribosome where it is added to the end of the growing peptide chain. There is at least one tRNA for each amino acid. 

Fig. 5. Generation of mutants using single-stranded DNA. After cloning the target gene into M13, the phage is propagated in the E. coll dut, ung strain of E.

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