Nuclear magnetic resonance relaxation in symmetrical cobalt(III) complexes

Rose, Kenneth D.; Bryant, R. G.

doi:10.1021/ic50195a034

Cited by 23 publications

(6 citation statements)

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“…59Co(en)33+ NMR in Simple Salt Solution Shows a Dominance of the Quadrupolar Relaxation Mechanism. The relaxation behavior of 59Co(en)33+ in simple salt solution differs qualitatively from that of 59Co(NH3)63+ (Craighead et al, 1975;Rose & Bryant, 1979). For the latter, the transverse relaxation behavior is dominated by scalar coupling to the 14N nuclei, with a minor contribution from the quadrupolar mechanism.…”

Section: Resultsmentioning

confidence: 90%

Chiral Recognition of Deoxyoligonucleotides by .DELTA.- and .LAMBDA.-Tris(ethylenediamine)cobalt(III)

Xu¹,

Jampani²,

Deng³

et al. 1995

Biochemistry

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59Co NMR and CD measurements show for both stereoisomers of Co(en)3(3+) a similar trend in the sequence dependence of DNA recognition, as was reported previously for Co(NH3)6(3+). In particular, specific binding is evident to DNA molecules possessing runs of two or more same-strand guanine residues. The binding of either isomer to such sequences induces structural transitions toward A-DNA characteristics. Such measurements also show significant differences between the two stereoisomers in terms of how they recognize specific duplex DNA sequences. delta-Co(en)3(3+) binds more tightly than lambda-Co(en)3(3+) to right-handed, guanine-rich DNA, whereas lambda-Co(en)3(3+) binds more tightly than delta-Co(en)3(3+) to left-handed DNA. The two stereoisomers bind in an indistinguishable manner to AT-rich DNA.

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Section: Resultsmentioning

confidence: 90%

Chiral Recognition of Deoxyoligonucleotides by .DELTA.- and .LAMBDA.-Tris(ethylenediamine)cobalt(III)

Xu¹,

Jampani²,

Deng³

et al. 1995

Biochemistry

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“…In the absence of oligomer, 59Co(NH3)3+ longitudinal relaxation is completely controlled by the quadrupolar relaxation mechanism, which results in a characteristic decrease in R1 with increasing temperature. In contrast, the 59Co transverse relaxation (R2 = 7-T*Avi2) is determined primarily by a scalar interaction with the 14N nucleus, with a minor contribution from the quadrupolar mechanism (Rose and Bryant, 1978). The relevant correlation time for the scalar interaction is the 14N T1, and hence an inverse quadrupolar temperature dependence is observed, i.e., in Co(NH3)6C13 solution, the 59Co linewidth increases with increasing temperature.…”

Section: Results and Discussion CD Spectramentioning

confidence: 99%

Induction of B-A transitions of deoxyoligonucleotides by multivalent cations in dilute aqueous solution

Xu¹,

Shoemaker²,

Braunlin³

1993

Biophysical Journal

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Circular dichroism (CD) spectra of d(CCCCGGGG) in the presence of Co(NH3)6(3+) are very similar to spectra of r(CCCCGGGG). In contrast, B-form characteristics are observed for d(CCCCGGGG) in the presence of Na+ and Mg2+, even at high salt concentrations. Spermidine induces modest changes of the CD of d(CCCCGGGG). The NMR chemical shifts of the nonexchangeable protons of d(CCCCGGGG) in the absence and presence of Co(NH3)6(3+) were assigned by proton two-dimensional (2D) NOESY and COSY measurements. The chemical shifts of the GH8 protons of d(CCCCGGGG) move upfield upon titration with Co(NH3)6Cl3. The sums of the sugar H1' coupling constants decrease with added Co(NH3)6Cl3. Cross peak intensities in the 2D proton NOESY spectra show a transformation from B-DNA to A-DNA characteristics upon the addition of Co(NH3)6Cl3. The temperature-dependent 59Co transverse and longitudinal relaxation rates demonstrate that Co(NH3)6(3+) is site-bound to the oligomer. Such localization is not a general feature of Co(NH3)6(3+) binding to oligonucleotides. 59Co NMR relaxation and CD measurements demonstrate chiral discrimination by d(CCCCGGGG) for the two stereoisomers of Co(en)3(3+). Both stereoisomers bind tightly as judged by 59Co NMR, and both cause large (but nonequivalent) changes in the CD of this oligomer.

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“…The agreement in both cases is well within the possible errors. (1 7) and 50 Hz (19) obtained by other methods. The cobaltinitrite value of 58.9 Hz does not agree with that reported in the literature (20) (46 Hz) but the latter value was based on an incorrect 14N assignment (21).…”

Section: ~O Measurementsmentioning

confidence: 87%

Rotating frame nuclear magnetic resonance experiments on metal complexes

Buist¹,

Eaton²

1987

Can. J. Chem.

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. Can. J. Chem. 65, 1653 (1987). Measurements of the rate of nuclear magnetic relaxation in the rotating frame (TI,) have the potential to provide significant information not readily available by other nmr methods. Some applications to metal complex chemistry are described. The method has been applied to 5 9~o nmr and used to obtain 5 9~o -' 4~ spin-spin coupling constants for the tris(ethy1ene-diamine)cobalt(III) and hexanitrocobaltate(III) ions. The larger coupling constant in the latter compound is related to the different hybridization of the nitrogen atom. Proton T I , measurements on thiourea and its zinc complex have demonstrated that at room temperature broadening of the 'H resonance is very largely ascribable to scalar relaxation rather than to chemical exchange processes. RICHARD J. BUIST et DONALD R. EATON. Can. J. Chem. 65, 1653 (1987. Les mesures de taux de relaxation magnitique nucliaire dans le refirentiel tournant (T,,) peuvent iventuellement fournir des informations importantes qui ne sont pas facilement accessibles par d'autres mtthodes rmn. On dtcrit quelques applications a la chimie des complexes mitalliques. On a appliquk la mkthode a la rmn du 59Co et on l'a utilisie pour ditenniner les constantes de couplage spin-spin 5 9~o -' 4~ des ions tris(Cthyl~nediamine)cobalt(III) et hexanitrocobaltate(II1). On relie la constante de coupIage qui est plus grande dans le dernier compost avec une hybridation diffirente de I'atome d'azote. Des mesures de TI, sur la thiourie et son complexe de zinc ont dkmoGri que, a la temptrature ambiante, l'ilargissement de la risonance du 'H est principalement dii a une relaxation scalaire plutdt qu'i des processus d'ichanges chimiques.[Traduit par la revue] Introduction Most nrnr relaxation studies have involved measurement of either the spin-lattice relaxation time, T I , or the spin-spin relaxation time T 2 . There is, however, a third relaxation time which can be rather easily obtained using a pulsed nrnr instrument. This is the relaxation time in the rotating frame, commonly designated T I P .Measurements of this parameter can yield chemically significant information not easily obtained by other methods. The present paper describes some applications of T I P measurements to metal complex chemistry.T i p is the relaxation time of transverse magnetization measured in the presence of a strong radiofrequency field which is known as the spin-locking field ( B l ) . The basic experiment used to measure T I P is quite straightforward (1). A 90" pulse along the x axis in the rotating frame rotates the magnetization to the y axis. As soon as this pulse is completed, the phase of the radio frequency is changed by 90" so that B1 also lies along the y axis also. Since the magnetization is now in the same direction as the rf field, no torque is exerted and it remains in that direction. The spins are said to be "locked" along the y axis. This magnetization will, however, still decay and the rate at which this occurs is a measure of T I P . Since it is difficult to measure th...

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Nuclear magnetic resonance relaxation in symmetrical cobalt(III) complexes

Cited by 23 publications

References 9 publications

Chiral Recognition of Deoxyoligonucleotides by .DELTA.- and .LAMBDA.-Tris(ethylenediamine)cobalt(III)

Chiral Recognition of Deoxyoligonucleotides by .DELTA.- and .LAMBDA.-Tris(ethylenediamine)cobalt(III)

Induction of B-A transitions of deoxyoligonucleotides by multivalent cations in dilute aqueous solution

Rotating frame nuclear magnetic resonance experiments on metal complexes

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