6- Aminopurine

In a combined experimental/computational study, the vibrational spectra of the N9H and N7H tautomers of the parent purine have been investigated [99SA(A) 2329]. Solvent effects were estimated by SCRF calculations. Vertical transitions, transition dipole moments, and permanent dipole moments of several low-lying valence states of 2-aminopurine 146 were computed using the CIS and CASSCF methods [98JPC(A)526, 00JPC(A)1930]. While the first excited state of adenine is characterized by an n n transition, it is the transition for 146. The... 

Therapeutic Function Cancer chemotherapy Chemical Name 2-aminopurine-6-thiol Common Name -Structural Formula SH... 

The photophysical properties of adenine have intrigued chemists from early on. Broo studied adenine and 2-aminopurine (2AP) in order to understand their differences in photophysical properties. Adenine like all natural nucleobases has very short excited state lifetimes and low quantum yields of fluorescence, while 2AP, which differs from adenine in the position of the amino group, has long lifetimes and strong fluorescence, making it a very useful fluorescent probe. In Broo s work it was observed that the first excited state is a nn at vertical excitation but crosses with an nn state which becomes the Si state adiabatically at the minimum. The large out-of-plane distortion on the nn state opens up a deactivation channel in adenine compared to 2AP. In 2AP, on the other hand, the Si state always has a 7T7r character. 

Three fluorescent purine analogs will be described here 2-aminopurine (2AP) [183] and 8-vinyladenine (8VAD), both of which mimic adenine, and N1,N6-ethenoadenine (e-AD). Their structures are shown in Figure 11-15. 2AP is probably the most widely used fluorescent DNA base analog, being utilized as a probe for DNA conformational dynamics [184, 185], due to the environmental specificity of... 

Serrano-Andres L, Merchan M, Borin AC (2006) Adenine and 2-aminopurine paradigms of modem theoretical photochemistry. Proc Natl Acad Sci USA 103 8691-8696... 

Hardman SJO, Thompson KC (2006) Influence of base stacking and hydrogen bonding on the fluorescence of 2-aminopurine and pyrrolocytosine in nucleic acids. Biochem 45 9145-9155... 

Jean JM, Hall KB (2002) 2-aminopurine electronic structure and fluorescence properties in DNA. Biochem 41 13152-13161... 

Sowers LC, Fazakerley GV, Eritja R, Kaplan BE (1986) Base pairing and mutagenesis observation of a protonated base pair between 2-aminopurine and cytosine in an oligonucleotide by proton NMR. Proc Natl Acad Sci USA 83 5434-5438... 

Rachofsky EL, Osman R, Ross JBA (2001) Probing structure and dynamics of DNA with 2-aminopurine effects of local environment on fluorescence. Biochem 40 946-956... 

Wang Q, Raytchev M, Fiebig T (2007) Ultrafast energy delocalization and electron transfer dynamics in 2-aminopurine-containing trinucleotides. Photochem Photobiol 83 637-641... 

Tautomers and electronic states of jet-cooled 2-aminopurine investigated by double resonance spectroscopy and theory. Phys Chem Chem Phys 7 3021-3026... 

Kodali G, Kistler KA, Matsika S, Stanley RJ (2007) 2-aminopurine excited state electronic structure measured by stark spectroscopy. J Phys Chem B 111 10615-10625... 

Rachofsky EL, Ross JBA, Krauss M, Osman R (1998) Spectroscopy of 2-aminopurine an MCSCF study. Acta Phys Polon A 94 735-748... 

Borin AC, Serrano-Andres L, Ludwig V, Coutinho K, Canuto S (2006) Theoretical electronic spectra of 2-aminopurine in vapor and in water. Int J Quant Chem 106 2564—2577... 

Broo A (1998) A theoretical investigation of the physical reason for the very diffferent luminescence properties of the two isomers adenine and 2-aminopurine. J Phys Chem A 102 526... 

Perun S, Sobolewski AL, Domke W (2006) Ab initio studies of the photophysics of 2-aminopurine. Mol Phys 104 1113-1121... 

Gaied NB, Glasser N, Ramalanjaona N, Beltz H, Wolff P, Marquet R, Burger A, Mly Y (2005) 8-vinyl-deoxyadenosine, an alternative fluorescent nucleoside analog to 2 -deoxyribosyl-2-aminopurine with improved properties. Nucl Acids Res 33 1031-1039... 

Mishra SK, Shukla MK, Mishra PC (2000) Electronic spectra of adenine and 2-aminopurine an ab initio study of energy level diagrams of different tautomers in gas phase and aqueous solution. Spectrochim Acta A 56 1355... 

Mennucci B, Toniolo A, Tomasi J (2001) Theoretical study of the photophysics of adenine in solution tautomerism, deactivation mechanisms, and comparison with the 2-aminopurine fluorescent isomer. J Phys Chem A 105 4749... 

Jean JM, Hall KB (2001) 2-aminopurine fluorescence quenching and lifetimes role of base stacking. Proc Natl Acad Sci USA 98 37-41... 

Herschlag s group continued its study of structure-function relationships in the hammerhead ribozyme using a base-rescue biochemical method. This method substitutes other atoms or molecules for bases at critical catalytic or structural positions and tests whether catalytic activity is lost. If so, the RNA bases (U, A, G, C) or a modified base (for instance, deazaguanine or 2-aminopurine substituted for guanine) is added to the solution to ascertain... 

Guanine (2-aminopurine-6-one, [95]), in which N-1 already carries a proton, is protonated at the N-3 position (p/iTi, = 2 95), since the ultraviolet spectrum of the cation [96] is closely similar to that of... 

The results indicate that C-6 in purine and 2-aminopurine (17) is more reactive than C-8 or C-2, while the primary attack at C-8 in adenine and 6-ethoxypurine (18) indicates that C-8 is more reactive than C-2. The order of reactivity toward a-hydroxyalkyl radicals in the purine system is therefore C-6 > C-8 > C-2. 

To further evaluate the binding of aminoglycosides to the RRE, Marino and co-workers have developed truncated RRE constructs (RRE IIB) where 2-aminopurine (2-AP), a fluorescent A isoster, replaces A at position 68 or U at position 72 (Figure 10.8). The fluorescent constructs retain their ability to bind Rev and can be used to monitor ligand binding. By measuring fluorescence... 

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