Anhydrous guanine: a synchrotron study

Guille, Kathy; Clegg, William

doi:10.1107/s0108270106026011

Cited by 79 publications

(120 citation statements)

References 8 publications

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“…The pattern fits that of the crystal structure determined for the anhydrous guanine. 10 Note that in contrast to the biogenic crystals, in the X-ray diffraction spectra of the in vitro grown crystals the intensities of the peaks corresponding to the (012), (020), (013), and (021) planes are enhanced relative to the (102) peak. This indicates a different preferred orientation of these crystals relative to the biogenic crystals.…”

Section: Resultsmentioning

confidence: 97%

“…The X-ray powder diffraction pattern calculated from the published anhydrous guanine crystal structure (measured at a temperature of 120 K) 10 is shown in Figure 2C. All the peaks are slightly shifted relative to those of the biogenic crystals.…”

Section: Resultsmentioning

confidence: 99%

“…4,6,7,[20][21][22] Here we show that the guanine crystals found in the skin of many fish is in the form of anhydrous guanine and that their crystal structure is identical to the recently published structure. 10 We determined the morphology of anhydrous guanine crystals formed in vitro and biogenic anhydrous guanine crystals and show that the morphology differs from the theoretical form calculated from the known crystal structure. We suggest that control of crystal morphology is part of the strategy evolved by fish to produce more efficient photonic crystals.…”

Section: Introductionmentioning

confidence: 97%

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Biogenic Guanine Crystals from the Skin of Fish May Be Designed to Enhance Light Reflectance

Levy-Lior

Pokroy

Levavi‐Sivan

et al. 2008

Crystal Growth & Design

120

169

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ABSTRACT:The metallic luster from the skin of fish is due to a photonic crystal system composed of multilayer stacks of cytoplasm and crystals. The crystals are described as thin (50-100 nm) plates of guanine, with no reference to their hydration state. We established through X-ray diffraction that their crystal structure is that of anhydrous guanine. We noted that their crystal structurefunction relationship is exceptional compared to other purines with similar molecular stacking of the crystal structure. These elongate in the direction of molecular stacking, in contrast to the biogenic anhydrous guanine crystals whose smallest dimension is in the stacking direction. On the basis of the known crystal structure of anhydrous guanine, theoretical growth morphology was calculated. These calculations predict crystals elongated in the direction of the molecular stacking. The exposed molecular plane of the biogenic crystals is the (102) plane, which is composed of densely packed H-bonded guanine molecules. It is known that the in-plane polarizability of guanine molecules is significantly higher than the direction perpendicular to the molecular plane, most likely causing anisotropy of the crystals refractive index. It is therefore conceivable that the unique morphology observed in crystals from the skin of fish is designed to enhance their light reflective properties.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Biogenic Guanine Crystals from the Skin of Fish May Be Designed to Enhance Light Reflectance

Levy-Lior

Pokroy

Levavi‐Sivan

et al. 2008

Crystal Growth & Design

120

169

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“…55 The atomic coordinates were fully optimized using the published crystal structures of anhydrous guanine and adenine as a starting point. 56,57 PW calculations performed for the cDDP-G 2 adduct were accomplished using the crystal structure of cis-[Pt(NH 3 ) 2 EG 2 ]SO 4 Á4H 2 O (EG = ethylguanine). 40 Unit cell parameters were kept at their experimental values.…”

Section: Theoretical Calculationsmentioning

confidence: 99%

A molecular view of cisplatin's mode of action: interplay with DNA bases and acquired resistance

Marques

Gianolio

Cibin

et al. 2015

Phys. Chem. Chem. Phys.

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The interaction of the widely used anticancer drug cisplatin with DNA bases was studied by EXAFS and vibrational spectroscopy (FTIR, Raman and INS), coupled with DFT/plane-wave calculations. Detailed information was obtained on the local atomic structure around the Pt(II) centre, both in the cisplatinpurine (adenine and guanine) and cisplatin-glutathione adducts. Simultaneous neutron and Raman scattering experiments allowed us to obtain a reliable and definite picture of this cisplatin interplay with its main pharmacological target (DNA), at the molecular level. The vibrational experimental spectra were fully assigned in the light of the calculated pattern for the most favoured geometry of each drug-purine adduct, and cisplatin's preference for guanine (G) relative to adenine (A) within the DNA double helix was experimentally verified: a complete N by S substitution in the metal coordination sphere was only observed for [cDDP-A 2 ], reflecting a somewhat weaker Pt-A binding relative to Pt-G. The role of glutathione on the drug's pharmacokinetics, as well as on the stability of platinated DNA adducts, was evaluated as this is the basis for glutathione-mediated intracellular drug scavenging and in vivo resistance to Pt-based anticancer drugs. Spectroscopic evidence of the metal's preference for glutathione's sulfur over purine's nitrogen binding sites was gathered, at least two sulfur atoms being detected in platinum's first coordination sphere.

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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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Anhydrous guanine: a synchrotron study

Cited by 79 publications

References 8 publications

Biogenic Guanine Crystals from the Skin of Fish May Be Designed to Enhance Light Reflectance

Biogenic Guanine Crystals from the Skin of Fish May Be Designed to Enhance Light Reflectance

A molecular view of cisplatin's mode of action: interplay with DNA bases and acquired resistance

Xanthine Dehydrogenase Active Site: Chiral Switching and Substrate Coordination

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