The crystal structure of guanine monohydrate

Thewalt, Ulf; Bugg, Charles E.; Marsh, Richard E.

doi:10.1107/s0567740871005880

Cited by 153 publications

(130 citation statements)

References 3 publications

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“…Base overlap is usually minimal and is accomplished by positioning carbon-hetero-atom bonds of one base over the ring system of another (Bugg, Thomas, Sundaralingam & Rao, 1971). The same hydrogen-bonded assembly of bases has now been found in the crystal structures of deoxythioguanosine, thioguanosine, guanosine (Thewalt, Bugg & Marsh, 1970), and guanine (Thewalt, Bugg & Marsh, 1971). These results imply that the thio-analogs have hydrogen-bonding capabilities similar to those of the natural bases.…”

Section: Introductionsupporting

confidence: 55%

The crystal structure of 2'-deoxy-6-thioguanosine monohydrate

Gartland¹,

Bugg²

1977

Acta Crystallogr Sect B

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Section: Introductionsupporting

confidence: 55%

The crystal structure of 2'-deoxy-6-thioguanosine monohydrate

Gartland¹,

Bugg²

1977

Acta Crystallogr Sect B

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“…The two carbonnitrogen bonds C(6)-N (1) and C(2)-N(1 ) lying between the two C-NHz bonds have the same lengths within experimental error, but the C-NH2 bonds probably have significantly different lengths, C(2)-N(2) being slightly longer (0.013 A) than C(6)-N(6). This difference in the two exocyclic C-NH2 bonds should be even more pronounced in the neutral molecule of 8-aza-2,6-diaminopurine, since as observed by Sundaralingam & Carrabine (1971) guanine monohydrate (Thewalt, Bugg & Marsh, 1971), which is not protonated at N(3). It has been noted (Singh, 1965;Ringertz, 1972) that the internal angles in purines and substituted purines are very sensitive to extraannular substitution, and Ringertz (1972) has predicted the values of these angles for the various modes of substitution.…”

Section: Bond Lengths and Bond Angles In The Cationsmentioning

confidence: 99%

The crystal structure of 8-aza-2,6-diaminopurine sulfate monohydrate

Singh¹,

Hodgson²

1975

Acta Crystallogr Sect B

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The crystal and molecular structure of 8-aza-2,6-diaminopurine sulfate monohydrate, (CaN7H6)2SOa.H20, has been determined from three-dimensional diffractometer X-ray data. The material crystallizes in space group P1 of the triclinic system with two formula units in a cell of dimensions a=6.813 (5), b=15-117 (11), c=8.182 (5)/~, e=91.71 (1), fl= 106.21 (1), and y=93.57 (1) °. The observed and calculated densities are 1"71 and 1.72 gcm -a, respectively. The structure has been refined by full-matrix least-squares techniques to a final value of the conventional R value (on F) of 0.039 for 2706 independent intensities. The two independent 8-aza-2,6-diaminopurine cations (ADPH) are very similar, and the sites of protonation are at N(3) and N(8); this result is similar to that observed in the 8-azaguaninium cation (AGH) but different from that found in the protonated form of natural purines. The hydrogen bonding in the crystal is extremely complicated, with all hydrogen atoms and all acceptor atoms except N(1) of one ADPH cation participating. The bond lengths and angles in the cations are normal, showing the anticipated effects of the protonation at N(3) and N(8).

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“…Heterocyclic aromatic compounds like purines and pteridines (the latter are left out from the present consideration) are known, by both experiment and numerical simulations, [62,63,64] to exist in multiple proto-tautomeric forms which easily exchange under the effects of immediate environment. If the x-ray evidence for the two proto-tautomers of dry and wet guanine, respectively, [65,66] is any guidance I conclude that the transition state depicted in Figure 4b forms as a result of the anti-TS coordination requirement accommodated with a specific hypoxanthine proto-tautomeric form selected by the reaction conditions within the XO active site.…”

Section: Resultsmentioning

confidence: 99%

Xanthine Dehydrogenase Active Site: Chiral Switching and Substrate Coordination

Ilich¹

2016

Croat. Chem. Acta

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Analysis of electronic, structural and mechanistic parameters of the enzyme-substrate reaction of xanthine oxidase, a member of the xanthine dehydrogenase class of mono-molybdopterin oxidoreductive enzymes, shows that the molybdenum center in the enzyme active site acts as a reversible chiral switch. The metal center cycles from the (S)-absolute configuration, SPY-5-42-A, in the fully oxidized state, Mo(VI), to the (R)-absolute configuration, SPY-5-43-C, for the fully reduced metal center, Mo(IV). This process is complemented by induction of chirality at the substrate carbon center (pro-SC → SC) and is involved in the control of coordination and, likely, protonation of imino-centers of conjugated heterocyclic substrates in the enzyme active site.

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The crystal structure of guanine monohydrate

Cited by 153 publications

References 3 publications

The crystal structure of 2'-deoxy-6-thioguanosine monohydrate

The crystal structure of 2'-deoxy-6-thioguanosine monohydrate

The crystal structure of 8-aza-2,6-diaminopurine sulfate monohydrate

Xanthine Dehydrogenase Active Site: Chiral Switching and Substrate Coordination

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