A carbon‐13 magnetic resonance study of the helix–coil transition in polyuridylic acid

Govil, Girjesh; Smith, Ian C. P.

doi:10.1002/bip.1973.360121111

Cited by 41 publications

(10 citation statements)

References 35 publications

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“…The 13C chemical shifts are listed in Table I, along with values for poly(U) reported earlier. 44 The three-bond 13C-13P coupling constants obtained from each spectrum are included in Table 11.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic studies on the structure of poly(8‐bromoadenylic acid): Effect of glycosidic torsion angle on the conformation and flexibility in polyribonucleotides

Govil¹,

Fisk²,

Howard³

et al. 1981

Biopolymers

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SynopsisThe helix-coil transition and conformational structure of poly(8-bromoadenylic acid) (poly(8BrA)J have been investigated using 'H-and 13C-nmr, CD, and ir spectroscopy. The results have been compared with the structure of the related 5'-mono-and polynucleotides. The chemical shifts of H(2'), H(3'), C(2'), and C(3') nmr signals show an interesting correlation with both the puckering of ribose ring and glycosidic bond torsion angle. Poly(8BrA) shows an upfield shift of the C(3') signal and a downfield shift of the H(3') signal compared to the chemical shifts in poly(A). These shifts are consistent with a C(3') endo-syn conformation for poly(8BrA). A similar effect has been reported previously and is also observed here on the C(2') and H(2') signals when the preferred conformation is C(2')endo-syn (e.g., in 5'-8BrAMP). The chemical-shift parameters thus act as a probe for studying s y n -t anti and N -t S equilibria in solutions. The three-bond lH-I3C coupling constants between H(1') and C(8) and C(4) have been measured in poly(8BrA) and 5'-8BrAMP and their structural implications have been discussed. The observed preference of a C(3')endo-syn conformation for poly(8BrA), coupled with other evidence, throws doubt on the validity of a correlation previously reported whereby a syn conformation is associated with a C(2')endo ribose pucker. The backbone conformation of randomly coiled poly(8BrA) is very similar to the structures found in polyribonucleotides: poly(A) and poly(U). All three polymers show strong preferences for the backbone angles found in RNA helices. The CD spectrum of poly(8BrA) has a striking relationship to that of poly(A). The signs of all extrema are inverted, and the magnitudes are related by a constant factor. We suggest that these differences result from a change in the angle between coupled transition moment vectors in the two polymers. Infrared spectra of poly(8BrA) in HzO and DzO solution are reported for the frequency range below 1400 cm-l. The antisymmetric >PO; stretching vibration is observed at an unusually low frequency in the helix (1214 cm-l). The symmetric >PO; stretch occurs at -1095 cm-I but is not resolved from a ring vibration near this frequency. A conformationally sensitive band, characteristic of helical RNA structures, is observed at 817 cm-' and disappears when the helix is melted. This observation confirms the conclusion that ordered poly(8BrA) has a regular helical structure with an RNA backbone conformation. A stereochemical explanation is provided for the failure of poly(8BrA) (or other syn polymers) to form double helices with anti-polyribonucleotides.

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Section: Resultsmentioning

confidence: 99%

Spectroscopic studies on the structure of poly(8‐bromoadenylic acid): Effect of glycosidic torsion angle on the conformation and flexibility in polyribonucleotides

Govil¹,

Fisk²,

Howard³

et al. 1981

Biopolymers

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“…The eclipsed rotamer is excluded on steric grounds. The trans or extended rotamer has also been found to be preferred for the exocyclic phosphate groups of nucleotides (25,27,29), polynucleotides (25,27,29,30), hexose 6-phosphates (31,32), and polysaccharides (33). The small variation of the 31POC13C couplings with p H is similar to that found for nucleotides (29); it is due to effects of ionization of the phosphate group on the coupling constants and/or small changes in equilibrium conformation.…”

Section: Resultsmentioning

confidence: 99%

Carbon-13 Nuclear Magnetic Resonance Studies of Compounds of the Vitamin B6 Group and Related Pyridine Derivatives

Lapper¹,

Mantsch²,

Smith³

1975

Can. J. Chem.

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SMITH. Can. J. Chem. 53,2406 (1975. The 13C chemical shifts and 13C-31P spin-spin couplings (where applicable) are reported for pyridoxine, pyridoxamine, pyridoxal, pyridoxamine phosphate, and pyridoxal phosphate. Resonance assignments are made by consideration of substituent chemical shift effects, as tested on an analogous series of pyridine derivatives. Increased shielding of the C4' and C5' methylene groups of the vitamin B6 compounds and the methyl groups of 3,4-dimethylpyridine relative to the predicted values are attributed to steric compression. In aqueous solution pyridoxal exists as the hemiacetal form, although at high p H it is in rapid equilibrium with a significant amount of the aldehyde form. Pyridoxal phosphate exists as the aldehyde at high pH, as the hydrated aldehyde at low pH, and in a slow equilibrium between detectable amounts of both species at p H 4. The 13C-31P couplings through two bonds lie in the range 4.5 f 0.5 Hz found for a variety of other organic phosphates. The couplings through three bonds indicate a preference for a trans arrangement of the phosphorus and ring carbon-5. ROY D. LAPPER, HENRY H. MANTSCH et IAN C. P. SMITH. Can. J. Chem. 53,2406Chem. 53, (1975. On a mesurC les dkplacements chimiques du 13C et les constantes de couplage spin-spin entre13C et 31P (dans les phosphates) pour la pyridoxine, pyridoxamine, pyridoxal, phosphate de pyridoxamine et phosphate de pyridoxal. Les attributions sont faites en considCrant les effets des substituants sur le dkplacement chimique dans une skrie analogue des pyridines substitukes. L'accroissement du blindage des carbones mkthylCniques 4' et 5' des composCs de la vitamine B6 et des groupes mCthyles du dirnkthyl-3,4 pyridine par rapport aux valeurs calculks, est attribuC a une compression stkrique. En solution aqueuse le pyridoxal existe sous la forme hemiacktale bien qu'a p H ClevC I'hCmiacktale soit en Cquilibre rapide avec une quantitC importante d'aldehyde. A p H ClevC, le phosphate de pyridoxal existe sous la forme aldkhyde, a p H faible sous forme aldehyde hydratk, et a p H 4 on a un Cquilibre lent entre des quantitts dicelables des deux espkes. Les constantes de couplage de 13C-31P a travers deux liaisons, se situent aux alentours de 4.5 + 0.5 Hz. Cette valeur correspond aux valeurs trouvCes pour divers phosphates organiques. Les couplages a travers trois liaisons suggtrent une forte prefkrence pour un arrangement trans du phosphore par rapport au carbone-5 du cycle.[Traduit par le journal] Introduction The vitamin B, group of compounds consists of pyridoxine, pyridoxamine, and pyridoxa 1 and their phosphates.5 Of these various forms the most active and effective over a large range of organisms appears to be pyridoxal 5'-phosphate, also known as codecarboxylase or cotransaminase. This compound represents the co-

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“…Here we have taken 3J(~c c = 10.1 Hz, 3J(~c c = 2.08 Hz [26] and 3J~t)oc.=28.2 Hz, 3J~,~CH= 1.5 Hz [27].…”

Section: Coupling Constants With the Sip Nucleusmentioning

confidence: 99%

NMR investigation of the micellar properties of monoalkylphoshpates

Chevalier

Chachaty

1984

Colloid & Polymer Sci

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Abstract:The micellization of several monoalkylphoshpates with chain lenghts from 6 to 10 carbons have been investigated by 31p and "C NMR spectroscopy with some additional electrical conductivity, density and small angle neutron scattering measurements.The major part of this study was performed on sodium monooctylphosphate. The critical concentration of micellization is 0.14 M, the partial molar volume is 170 cm3/mole in the micellar state. Small angle neutron scattering measurements on a 0.5 molar solution lead to an aggregation number of 43. NMR studies over the whole concentration range show that the pseudophase model holds. The geometry around the polar head is found almost unchanged upon micellization. The frequency denpendence of the 31p longitudinal relaxation is interpreted by an isotropic fas motion (rR = 6.5 x 10 -11 s for the free monomers and by a strongly anisotropic motion with D II/D• ~ 10 and ro = (6 D) -1=1.25 x 10-9s in the micellar state.

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A carbon‐13 magnetic resonance study of the helix–coil transition in polyuridylic acid

Cited by 41 publications

References 35 publications

Spectroscopic studies on the structure of poly(8‐bromoadenylic acid): Effect of glycosidic torsion angle on the conformation and flexibility in polyribonucleotides

Spectroscopic studies on the structure of poly(8‐bromoadenylic acid): Effect of glycosidic torsion angle on the conformation and flexibility in polyribonucleotides

Carbon-13 Nuclear Magnetic Resonance Studies of Compounds of the Vitamin B6 Group and Related Pyridine Derivatives

NMR investigation of the micellar properties of monoalkylphoshpates

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