Messenger

In RNA the sugar is ribose and uracil replaces thymine. Different varieties of RNA exist with widely different molecular weights. Messenger RNA conveys information in the form of the sequence of bases from DNA to RNA on the ribosomes, where proteins are... 

Much of the communication between insects involves chemical messengers called pheromones A species of cockroach secretes a substance from its mandibular glands that alerts other cockroaches to its presence and causes them to congregate One of the principal components of this aggregation pheromone is the alkane shown in the bond line formula that follows Give the molecular formula of this substance and represent it by a condensed formula... 

Nitrogen monoxide ( nitnc oxide ) is another stable free radical Although known for hundreds of years NO has only recently been discovered to be an extremely important biochemical messenger and moderator of so many biological processes that it might be better to ask Which ones is it not involved m ... 

Ethylene occurs naturally in small amounts as a plant hormone Hormones are substances that act as messengers to regulate biological processes Ethylene IS involved in the ripening of many fruits in which it IS formed in a complex series of steps from a com pound containing a cyclopropane ring... 

Earl Sutherland of Vanderbilt University won the 1971 Nobel Prize in physiology or medicine for uncovering the role of cAMP as a second messenger in connection with his studies of the fight or flight hormone epineph rine (Section 27 6)... 

In the example shown the 5 OH group is phosphorylated Nucleotides are also possible in which some other OH group bears the phosphate ester function Cyclic phosphates are common and important as biochemical messengers... 

Section 28 11 Three RNAs are involved m gene expression In the transcription phase a strand of messenger RNA (mRNA) is synthesized from a DNA tern plate The four bases A G C and U taken three at a time generate 64 possible combinations called codons These 64 codons comprise the genetic code and code for the 20 ammo acids found m proteins plus start and stop signals The mRNA sequence is translated into a prescribed protein sequence at the ribosomes There small polynucleotides called... 

Messenger RNA (mRNA) (Section 28 11) A polynucleotide of nbosethat reads the sequence of bases in DNA and inter acts with tRNAs in the nbosomes to promote protein biosynthesis... 

When the cell requires instructions for protein production, part of the code on DNA, starting at an initiator and ending at a stop codon, is converted into a more mobile form by transferring the DNA code into a matching RNA code on a messenger ribonucleic acid (mRNA), a process known as transcription. The decoding, or translation, of mRNA then takes place by special transfer ribonucleic acids (tRNA), which recognize individual codons as amino acids. The sequence of amino acids is assembled into a protein (see Proteins section). In summary, the codes on DNA... 

For example, a polypeptide is synthesized as a linear polymer derived from the 20 natural amino acids by translation of a nucleotide sequence present in a messenger RNA (mRNA). The mature protein exists as a weU-defined three-dimensional stmcture. The information necessary to specify the final (tertiary) stmcture of the protein is present in the molecule itself, in the form of the specific sequence of amino acids that form the protein (57). This information is used in the form of myriad noncovalent interactions (such as those in Table 1) that first form relatively simple local stmctural motifs (helix... 

Each component of blood has a function ia the body. Red cells transport oxygen and carbon dioxide between the lungs and cells ia the tissues. White cells function as defense of the body. Platelets are important for hemostasis, ie, the maintenance of vascular iategrity. Plasma, an aqueous solution containing various proteias and fatty acids, transports cells, food, and hormones throughout the body. Some proteias ia plasma play a role ia clotting, others are messengers between cells. 

If an antibody to the protein of interest is available, it is sometimes possible to use vector sequences, eg, the beta-galactosidase promoter sequence, to direct the transcription of the passenger DNA into messenger RNA and the translation of that mRNA into protein which can be recognized by the antibody. Although this method is somewhat less reHable than the use of nucleic acid probes, specialized vectors are available for this purpose. 

Oxytocin and Vasopressin Receptors. The actions of oxytocin and vasopressin are mediated through their interactions with receptors. Different receptor types as well as different second messenger responses help explain their diverse activities in spite of the hormones stmctural similarities. Thus oxytocin has at least one separate receptor and vasopressin has been shown to have two principal receptor types, and V2. Subclasses of these receptors have been demonstrated, and species differences further compHcate experimental analysis. It is apparent that both oxytocin and receptors function through the GP/1 phosphoHpase C complex (75), while the V2 receptors activate cycHc AMP (76). 

KhGH A natural, stmctural variant of hGH called 20-K hGH has been reported to occur in the pituitary as well as in the bloodstream (12,13). This variant, which lacks the 15 amino acid residues from Glu-32 to Gln-46, arises from an alternative splicing of the messenger ribonucleic acid (mRNA) (14). This variant shares many but not all of the biological properties of hGH. 

Stmcture searching and display software are host-specific. The Softon Substmcture Search System (S4) was developed by the Beilstein Institute and Softon of Graefelfing Germany (50). It is a full stmcture and substmcture searching module. The S4 is used in-house by the Beilstein Institute and is operated by DIALOG. STN uses CAS ONLINE s messenger software for on-line stmcture searching of the Beilstein on-line database (51). 

A number of files under the generic tide CAS ONLINE are available on-line on STN International. The system software, MESSENGER, includes chemical substmcture, text, and numeric data searching facHities. Chemical stmctures and Registry Numbers are contained in the CA Registry file. The four ways to search the stmctures are EXA, EAM, SSS, and CSS. 

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