Nucleotides dinucleotide synthesis

Pyridine dinucleotide, synthesis of analogs, 252, 253 Pyridine nucleotide analogs, 260 spin-labeled, 260... 

Selected entries from Methods in Enzymology [vol, page(s)] Determination of FMN and FAD by fluorescence titration with apoflavodoxin, 66, 217 purification of flavin-adenine dinucleotide and coenzyme A on p-acetoxymercurianiline-agarose, 66, 221 a convenient biosynthetic method for the preparation of radioactive flavin nucleotides using Clostridium kluyveri, 66, 227 isolation, chemical synthesis, and properties of roseoflavin, 66, 235 isolation, synthesis, and properties of 8-hydroxyflavins, 66, 241 structure, properties and determination of covalently bound flavins, 66, 253 a two-step chemical synthesis of lumiflavin, 66, 265 syntheses of 5-deazaflavins, 66, 267 preparation, characterization, and coenzymic properties of 5-carba-5-deaza and 1-... 

Several nucleotides have been detected in milk (see Table 1.9). The list includes the common mono-and dinucleotides, 3, 5 cyclic AMP, and adenosine triphosphate (ATP). The ATP is located entirely in the casein micelles (Richardson et al. 1980). Several nucleotide sugars, undoubtedly excess intermediates left over from mammary synthesis of glycoproteins, are present. Both DNA and RNA have been detected in milk (Swope and Brunner 1965 Swope et al. 1965 Langen 1967) they are probably found primarily in milk leukocytes. 

Fig. 2. Masking strategy for the combinatorial synthesis of all possible polynucleotide tetra-mers. In round 1, a mask is used to add all four nucleotides, to four separate regions of the substrate, as the first base in the array. An orthogonal mask is used in round 2 to subdivide each mononucleotide cell into quarters for the addition of the four nucleotides as the second base. This generates a 4 x 4 array of all possible dinucleotides. The mask used in round 3 further subdivides the dinucleotide cells into quarters for the addition of the third base. After 4 rounds, an array of all 256 dinucleotides is obtained. This process can be continued, using masks which subdivide cells into increasingly smaller regions, to obtain complete arrays of longer polynucleotide sequences...

It is not strictly correct to regard niacin as a vitamin. Its metabolic role is as the precursor of the nicotinamide moiety of the nicotinamide nucleotide coenzymes, nicotinamide adenine dinucleotide (NAD) and NADP, and this can also be synthesized in vivo from the essential amino acid tryptophan. At least in developed countries, average intakes of protein provide more than enough tryptophan to meet requirements for NAD synthesis without any need for preformed niacin. It is only when tryptophan metabolism is disturbed, or intake of the amino acid is inadequate, that niacin becomes a dietary essential. 

Nucleotides are important constituents not only of RNA and DNA, but also of a number of key biomolecules considered many times in our study of biochemistry. NAD+ andNADP+, coenzymes that function in oxidation-reduction reactions, are metabolites of ATP. The first step in the synthesis of nicotinamide adenine dinucleotide (NAD+) is the formation of... 

The pentose phosphate pathway (PPP) is the major pathway for recycling nicotinamide adenine dinucleotide (NAD) to nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) and for the production of ribose-5-phosphate that is needed for the synthesis of nucleotides. The function of the PPP depends on the synthesis of nicotinamide-adenine dinucleotide phosphate (NADP) and thiamin pyrophosphate, a coenzyme... 

The alkaloids interfere with a number of enzyme systems. In vitro, lasiocarpine and heliotrine inhibit enzyme systems that need pju idine nucleotides for electron transfer (45). The nicotinamide-adenine dinucleotide pyrophosphorylase activity of nuclei from rat liver that has been treated with heliotrine is reduced significantly below that of controls (46). It has recently been shown that in rats lasiocarpine inhibits RNA synthesis, causes a substantial reduction in tryptophan pyrrolase activity, and decreases the activity of RNA polymerase (47). 

Transitions that underlie promoter clearance may be rationalized with the Pol II structures. At the very beginning of transcription, contacts of Pol II with nascent RNA are crucial. To allow for the synthesis of the first phosphodiester bond, nucleoside triphosphates must be held by the protein. The resulting dinucleotide RNA must still be held by protein— RNA contacts, as observed in the core elongation complex structure (Gnatt et al., 2001), as the energy of base-pairing alone is insufficient for its retention. Equally, RNA is still bound by Pol II at the position of the third nucleotide. Despite the observed RNA-Pol II contacts, short RNA... 

Instead of the conventional method of synthesizing individual trinucleotides for codon analysis, it is possible to couple a mixture of all 4 nucleotides to another mixture of 4 nucletotides to produce 16 dinucleotides. If these newly formed 16 dinucleotides are reacted with a mixture of 4 additional nucleotides, 64 trinucleotides that correspond to aU possible codons are obtained. The mixture of 64 trinucleotides is called a combinatorial library (nucleotide library). In this combinatorial synthesis, the number of products (P) increases exponentially according to... 

Mosbach K, Guilford H, Ohlsson R et al. (1972) General Ugands in affinity chromatography. Cofactor-substrate elution of enzymes bound to the immobilized nucleotides adenosine 5 -monophosphate and nicotinamide-adenine dinucleotide. Biochem J 127(4) 625-631 Moses V, Prevost C (1966) Catabolite repression of P-galactosidase synthesis in Escherichia coli. Biochem J 100(2) 336-353... 

The first step in de novo pyrimidine biosynthesis is the synthesis of carbamoyl phosphate from bicarbonate and ammonia in a multistep process, requiring the cleavage of two molecules of ATP. This reaction is catalyzed by carbamoyl phosphate synthetase (CPS), and the bicarbonate is phosphorylated by ATP to form carboxyphosphate and ADP (adenine dinucleotide phosphate). Ammonia then reacts with carboxyphosphate to form carbamic acid. The latter is phosphorylated by another molecule of ATP with the mediation of CPS to form carbamoyl phosphate, which reacts with aspartate by aspartate transcarbamoy-lase to form A-carbamoylaspartate. The latter cyclizes to form dihydroorotate, which is then oxidized by NAD-1- to generate orotate. Reaction of orotate with 5-phosphoribosyl-l-pyrophosphate (PRPP), catalyzed by pyrimidine PT, forms the pyrimidine nucleotide orotidylate. This reaction is driven by the hydrolysis of pyrophosphate. Decarboxylatin of orotidylate, catalyzed by orotidylate decarboxylase, forms uridylate (uridine-5 -monophosphate, UMP), a major pyrimidine nucleotide that is a precursor of RNA (Figure 6.53). 

Nucleotide bases (Fig. 7.16) have been derivatized by use of electrophilic organoiron complexes. The carbonyliron adducts 37 and 38 are typical examples [98]. A recent development in this field has led to the synthesis [99] of an extensive set of stmctures, including 39 which more closely resembles a nucleoside. The thymidine derivative 40 is an inhibitor of human thymidine kinase [100]. In the case of 41, the carbonylmetal component is attached at the heterocyclic base [101]. The carbonylmetal component can also be attached to dinucleotides by coordination at a phosphite, placed (as in 42) where the phosphate link would normally join the ribose rings [102]. The attachment of carbonylmetal labels to oligonucleotides for analysis by FTIR has also been described. The succini-midyl-based delivery strategy is the same as that used with proteins, as a... 

The other biologically important flavin is a dinucleotide, made from FMN and ATP in a reaction analogous to the synthesis of DPN, to form flavin adenine dinucleotide (FAD), in which the two nucleotides are joined by a pyrophosphate bond (I). 

Synthesis by Transfer. Ribonuclease catalyzes transfer reactions in addition to hydrolyses. Both cyclic nucleotides and diesters of 3 -nucleo-tides serve as substrates for the transfer. Acceptors for the phosphate include the primary alcohol groups of nucleosides, nucleoside cyclic phosphates, and simple alcohols. Simple nucleotides do not serve as acceptors. The products of transfer reactions, including dinucleoside monophosphates and the so-called cyclic dinucleotides, can also serve as acceptors, and by repeated transfer reactions of cyclic nucleotides small polymers have been built up (IV). It has been suggested that this reaction may play a role in nucleic acid biosynthesis. ... 

---