Adenosine complexes, temperature

Miles (1968) has presented data for the interaction between 5 -GMP and poly-cytidylic acid, and has discussed the use of 5 -GMP-6- 0 to assign a band at 1685 cm to a guanine carbonyl in 5 -GMP-6- 0, since the 1685 cm band was the only one to decrease in frequency upon 6- 0 substitution of GMP. He also discussed the melting curves of a poly U-6-methylamino-9-methylpurine complex, and a poly UC (30/70)-adenosine complex. In this paper he has described cells, temperature controls, spectroscopic instrumentation and conditions, and experimental procedures used throughout most of the work discussed in this section on Aqueous Solutions. 

NMR spectroscopy indicates a dynamic equilibrium of rotamers of the thiourea in complex ions such as [PtCl(diamine)(monofunctional thiourea)] Dynamic processes in platinum(II)-adenosine complexes have been investigated and the Pt NMR spectra recorded.Variable temperature NMR spectroscopy shows restricted rotation of the NO group in [PtCl3(4-X-C6H4NO)] . The intramolecular conformational exchange thermodynamics of a5 -[PtCl2 l,T-(CiiH23SeC5H4-ri )2Fe ] have been determined. 

Table XIX contains stability constants for complexes of Ca2+ and of several other M2+ ions with a selection of phosphonate and nucleotide ligands (681,687-695). There is considerably more published information, especially on ATP (and, to a lesser extent, ADP and AMP) complexes at various pHs, ionic strengths, and temperatures (229,696,697), and on phosphonates (688) and bisphosphonates (688,698). The metal-ion binding properties of cytidine have been considered in detail in relation to stability constant determinations for its Ca2+ complex and complexes of seven other M2+ cations (232), and for ternary M21 -cytidine-amino acid and -oxalate complexes (699). Stability constant data for Ca2+ complexes of the nucleosides cytidine and uridine, the nucleoside bases adenine, cytosine, uracil, and thymine, and the 5 -monophosphates of adenosine, cytidine, thymidine, and uridine, have been listed along with values for analogous complexes of a wide range of other metal ions (700). Unfortunately comparisons are sometimes precluded by significant differences in experimental conditions.

The dissociation of the proflavine poly(dA-dT) complex can be followed by monitoring the temperature dependent chemical shift or the line width as demonstrated by shift data on the thymidine CH3-5 resonance (Figure 18A) and width data on the adenosine H-8 resonance (Figure 18B). The proton resonances shift as average peaks during the dissociation of the complex, indicative of fast exchange ( dissociation 10 sec l at the transition midpoint) between the complex and its dissociated components on the NMR time scale. 

Nucleic Acid Base Resonances The chemical shifts of the nonexchangeable protons in poly(dA-dT), the Nuc/D = 24 complex and the Nuc/D = 8 complex in 1 M NaCl solution are plotted as a function of temperature in Figure 19. The nucleic acid nonexchangeable proton chemical shifts in the duplex state are either unperturbed (adenosine H-8, H-2, and thymidine CH3-5) or shift slightly upfield (thymidine H-6) on complex formation (Figure 19). By contrast, the thymidine H-3 exchangeable proton located in the center of the duplex resonates 0.35 ppm to higher field in the Nuc/D = 8 proflavine complex compared to its position in the... 

Figure 18. The temperature dependence of (A) the thymidine CH.,-5 chemical shift and (B) the adenosine H-8 linewidth in poly(dA-dT) (O), the proflavine polv(dA-dT) complex, Nuc/D 24 (A) and Nuc/D = 8(9) in 1M NaCl, lOmM cacodylate, lOmM EDTA, sH.O, pH 7...

The melting transition of the daunomycin poly(dA-dT) complex can also be monitored at the nucleic acid resonance line widths and the data for the adenosine H-8 resonance are plotted in Figure 28. The resonance is very broad at temperatures below the melting transition of the complexes (dashed curves in Figure 28) indicative of stiffening of the synthetic DNA by the bound anthracycline ring. 

Figure 27. The temperature dependence of the adenosine H-2 resonance (7.1 to 8.1 ppm) for poly(dA-dT) ( ) and the daunomycin poly(dA-dT) complexes, Nuc/D = 50 (A), 25 (O), 9 ( ), and 5 (A.) in IM NaCl, lOrnM cacodylate, 7mM EDTA, HjO solution. The poly(dA-dT) concentration was fixed at I9.3mM in phosphates and the daunomycin concentration was varied to make the different...

Note that the muscular motive power of the human body (see the introduction to this book) comes from the isothermal hydrolysis of adenosine tri-phosphate to di-phosphate (Atkins, 1995), a wet reaction in which little power is associated with reactant and product handling. Nature has evolved to a position of elegant fuel economy. Nature also has to undertake a complex chemical manufacturing task to provide automated selfmaintenance of the body. Chemical reactions are isothermal at blood temperature, along the same lines as the Regenesys system of Chapter 2. 

There has also been interest in restricted rotations in adenosine Pt complexes in which lower temperatures reveal the effects of rotation in complexes such as (51). Marziltf has been particularly active in the analysis of dynamics of N-donor bioligands, but they have also emphasized studies of octahedral ruthenium complexes. More complicated N-donor hgands can produce multiple processes which can be observed by DNMR and in some cases hindered rotation in pendant rings can be observed. " There has been a recent review of DNMR methods applied to supramolecular systems. ... 

With one equivalent of [(trpn) Co (H20)2] +, a complex is formed with AMP in which both emionic oxygens are coordinated to cobalt addition of the second equivalent is thought to form (234) transiently, with subsequent expulsion of adenosine affording the observed products. By heating at neutral pH in the presence of Mn2+ ions at temperatures above 50° C, ATP can be used to phosphorylate the hydroxy groups of serine and tyrosine non-enzymatically. Calcium ions can substitute for Mn + ions, albeit less effectively, but Mg + ions are ineffective. The reaction can be used to prepare radiolabelled phosphoserine - or phosphotyrosine-containing peptides. 

Cayley and Hague [70a] have employed the temperature-jump relaxation method to measure the rate of formation and dissociation of the 1 1 complex of magnesium(II) and 5-nitrosalicyclic acid (NSA) and also of the ternary complexes formed between this ligand and Mg(II) nitrilotriacetate (NTA), adenosine triphosphate (ATP) and polytriphosphate (TP) complexes, the last in an effort to gather information about the effect of bound ligands on the rate of substitution of a metal ion by a second type of group. It is expected that the presence of a bound ligand should... 

Figure 8.6.11 Temperature-dependent plot of the shift of N3-labeled adenosine in the DNA duplex d(CGCAATTCGCG)2 after addition of distamycin and netropsin. (A) Average N3 shifts in absence of drug (°) A6N3 shift in netropsin complex shows no effect, except for exclusion of water ( ) A6N3 shift in distamycin complex—shows large effect (E,A) A18N3 shifts are the same in distamycin and netropsin complexes. These results led to hydrogen bonds sketched bold in Figure 8.6.10. (From Rhee et al., 1993.)...

Stoichiometric mixtures of polyuridylic acid with either adenosine or 2-aminoadenosine have spectra (Howard et ai, 1966b) at low temperatures which closely resemble that of the three-stranded complex (A -I- 2U) (Figs. 12.19 and 12.20). With heating, the solutions show progressive spectral changes until a temperature is... 

Respiration is a process in which chemical reactions oxidize lipids and carbohydrates to carbon dioxide and water to produce energy, while the organelle responsible for aerobic respiration known as mitochondria. Part of the released energy is stored as chemical energy adenosine triphosphate (ATP) and part is lost as heat. This complex process can be influenced by several intrinsic factors such as product size, variety, maturity, type of tissue and extrinsic factors such as temperature, concentration of O2 and CO2 and mechanical damage (Day, 1993). 

Phase trtmsition is shifted to lower temperatures upon addition of urea or adenosine (complementary nucleic add base to uradl) preventing the complex formation in cold water... 

The complexation reaction between Rh2(0Ac)4 2H20 and 5 -AMP (adenosine monophosphate) has been investigated using temperature jump.< " It provides an interesting example of relaxation kinetics because two equilibria are maintained. Denoting the dirhodium complex as M and the 5 -AMP as L, the important equilibria are... 

Nucleic acid-directed synthesis may have also been important in early peptide formation. Weber and Orgel showed that when the amino acid glycine is esterified to derivatives of adenosine (in the same manner that amino acids are bonded to tRNA in extant protein synthesis), the amino acids will form peptide bonds, resulting in cyclic Gly-Gly dipeptides [29]. Further, when poly-uracil (poly(U)) is added to the mixture, the amount of cyclic Gly-Gly formed increases about 3 times [30]. The temperature and concentration effects of the reactions suggested dependence on formation of a poly(U) hehx specifically, a triple helix of two strands of poly(U) complexed with the glycine-esterified adenosine derivatives. While the exact mechanism of peptide bond formation in this case has not been established, the increased yield of dipeptide could be due to increased local concentration/ optimal orientation of the glycine derivatives based on specific interactions between poly(U) and adenosine. 

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