The crystal structure of the 1:1 molecular complex between lumiflavinium chloride and hydroquinone

Karlsson, Rolf

doi:10.1107/s0567740872006120

Cited by 8 publications

(3 citation statements)

References 4 publications

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“…In lumiflavin-2-aminobenzoic acid, the donor and acceptor ring systems are rotated by an angle of approximately 15°. A similar angle has been found in lumiflavinium bromide-sesqui(naphthalene-2,7-diol) monohydrate (Langhoff & Fritchie, 1970), lumiflavinium chloride-hydroquinone (Karlsson, 1972), and lumiflavinium bromide-hydroquinone (Tillberg & Norrestam, 1972). On the other hand, isoalloxazine and ligand nets are almost exactly parallel in lumiflavin-diaminopurine (Scarbrough et al, 1976) and 10-propylisoalloxazine-bis(naphthalene-2,3-diol) (Kuo et al, 1974).…”

Section: Discussionsupporting

confidence: 75%

“…The central aminobenzoic acid is drawn with filled bonds; the lumiflavin at the rear is related to that in front by a unit cell translation in c; atoms of the rear molecule can thus be identified by comparison with the frontmost molecule. (Karlsson, 1972). Although it has seemed reasonable to assume that these low frequency bands arise from charge transfer in the stacking direction, all the complexes involving aromatic ligands display in-plane as well as stacking interactions.…”

Section: Discussionmentioning

confidence: 99%

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Molecular complex of lumiflavin and 2-aminobenzoic acid: crystal structure, crystal spectra, and solution properties

Shieh¹,

Ghisla²,

Hanson³

et al. 1981

Biochemistry

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ABSTRACT:The molecular complex lumiflavin-2-aminobenzoic acid monohydrate (C,3H,2N402C7H7N02-HZO) crystallizes from aqueous solution as red triclinic prisms. The space group is Pi with cell dimensions a = 9.660 A, b = 14.866 A, c = 7.045 A, a = 95-44', B = 95.86', and y = 105.66'. The crystal structure was solved by direct methods and refined by block-diagonal least-squares procedures to an R value of 0.050 on the basis of 1338 observed reflections. The structure is composed of stacks of alternating lumiflavin and un-ionized (neutral) 2-aminobenzoic acid molecules. Two different modes of stacking interaction are observed. In one, 2-aminobenzoic acid overlaps all three of the isoalloxazine rings, at a mean distance of 3.36 A; in the other, 2-aminobenzoic acid interacts with the pyrazine and dimethylbenzene moieties, at a distance (3) to two symmetrically related aminobenzoates; the water of crystallization forms three hydrogen bonds, bridging two flavins, via O(4) and N(5), and one aminobenzoic acid. The red color of the crystals results from a charge-transfer transition involving stacked flavin and 2-aminobenzoic acid molecules. Measurements of the polarized optical absorption spectra of crystals show that the transition moment direction for the long wavelength absorbance (beyond 530 nm) contains an out-of-plane component which can only arise from a charge-transfer interaction. Since the amino N does not make exceptionally close interactions with isoalloxazine atoms in either stacking mode (minimum interatomic distance 3.52 A), the charge transfer is presumed to involve T orbitals of the 2-aminobenzoic acid donor.

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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Molecular complex of lumiflavin and 2-aminobenzoic acid: crystal structure, crystal spectra, and solution properties

Shieh¹,

Ghisla²,

Hanson³

et al. 1981

Biochemistry

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“…Somewhat less symmetrical associations are seen in the similar charge-transfer complexes lumiflavinium bromide-hydroquinone (29) and lumiflavinium chloride-hydroquinone (30). The interplanar spacings in all of these highly colored donor-acceptor complexes are less than the 3.4 A distance expected for normal stacking interactions.…”

Section: Description Of the Structurementioning

confidence: 88%

Crystal structure of a complex between lumiflavin and 2,6-diamino-9-ethylpurine: a flavin adenine dinucleotide model exhibiting charge-transfer interactions.

Scarbrough¹,

Shieh²,

Voet³

1976

Proc. Natl. Acad. Sci. U.S.A.

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The x-ray structure of the deep red crystalline complex lumiflavin*2,6-diamino-9-ethylpurine has been determined. The flavin and adenine derivatives form hydrogenbonded base pairs of the Watson-Crick type. The molecules in the crystal also associate via extensively overlapped flavin/ adenine and flavin/flavin stacking interactions in which there are several contacts that are closer than van der Waals distances. This, together with the red color of the crystals, is indicative of the formation of a charge-transfer complex.An intriguing problem of flavin biochemistry is the function of the adenine moiety of FAD. A study of the activity of the flavoenzyme D-amino acid oxidase upon binding adenosylmodified FAD analogues has shown that this enzyme exhibits considerable specificity with regard to the adenine portion of FAD (1). Yet it is clear that the adenine residue in FAD does not directly affect the oxidation potential of the flavin moiety. It has therefore been suggested that the role of the adenine group in FAD may involve its participation in an intramolecular complex with the flavin moiety (2). This report is concerned with the elucidation of a structural model for such a complex.The component molecules of Watson-Crick base pairs exhibit a selective affinity in hydrogen bonding that has been observed using infrared studies (3). Thus, uracil derivatives have a higher association constant for binding adenine derivatives than for derivatives of guanine or cytosine (4). The close resemblance of the pyrimidinoid ring of isoalloxazine to uracil suggests that FAD may form a strongly hydrogen-bonded intramolecular complex. This has been confirmed in nonaqueous solutions by infrared studies (5) and in aqueous solutions by nuclear magnetic resonance studies (6). In the solid state, flavin-adenine base pairing of the Hoogsteen variety has been directly observed by x-ray studies of the crystalline complexes of riboflavin with 5'-bromo-5'-deoxyadenosine (2, 7) and with adenine (8).In aqueous solutions the majority of FAD molecules assume a folded, internally stacked conformation in much the same manner as do oligonucleotides (9). This has been shown by a variety of techniques including fluorescence measurements, both at normal (10) and elevated pressures (11), and by nuclear magnetic resonance measurements (12). The adenine and isoalloxazine derivatives in the above-mentioned structural studies associate by normal stacking interactions (2, 7, 8). There have been occasional reports of charge-transfer bands in the spectra of flavin-purine complexes in solution but it appears that donor-acceptor interactions are unimportant in the stabilization of such complexes (13). Slifkin (14) has reported that evaporating aqueous solutions of purines and riboflavin to dryness yields strongly colored residues that are apparently composed of charge-transfer complexes.The complexing properties of reduced flavins are less familiar than those of oxidized flavins. Hence in an effort to elucidate the manner in which reduced flavins assoc...

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Electronic properties of flavins: Implications on the reactivity and absorption properties of flavoproteins

Wouters

Durant

Champagne

et al. 1997

Int. J. Quant. Chem.

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supports the classification of the flavoenzymes into two classes. Moreover, the -U transition has been correctly placed as the lowest energy transition for the neutral oxidized lumiflavin and predicts a blue shift of the low-lying electronic transition upon monoprotonation. Finally, from the analysis of the molecular complex between oxidized Ž . lumiflavin HFl and hydroquinone, we have rationalized the complex formation in ox terms of the complementarity between the molecular electrostatic potentials as well as in terms of the overlap between the frontier orbitals involved in these charge transfer process.

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The crystal structure of the 1:1 molecular complex between lumiflavinium chloride and hydroquinone

Cited by 8 publications

References 4 publications

Molecular complex of lumiflavin and 2-aminobenzoic acid: crystal structure, crystal spectra, and solution properties

Molecular complex of lumiflavin and 2-aminobenzoic acid: crystal structure, crystal spectra, and solution properties

Crystal structure of a complex between lumiflavin and 2,6-diamino-9-ethylpurine: a flavin adenine dinucleotide model exhibiting charge-transfer interactions.

Electronic properties of flavins: Implications on the reactivity and absorption properties of flavoproteins

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