23Na NMR Relaxation Studies of the Na-DNA/Drug Interaction

Metal Binding to Sodium Heparin Monitored by Quadrupolar NMR

“…When increases due to an increase in ω 0 and/or τ c , the two T 1 relaxation times decrease until they reach their minimum values and then monotonously increase afterward. The T 2 relaxation time of the central transition follows a similar trend; however, the satellite transition exhibits a monotonous decrease with [ 17 , 25 , 26 , 27 ]. With further increase in τ c when (ω Q is the quadrupolar coupling constant in angular frequency units), the system enters the so-called “ultraslow regime,” and its relaxation deviates from Redfield’s theory, which is outside the scope of the current study (see Methods for further description) [ 26 , 28 ].…”

“…When τ c and/or ω 0 increase and the system enters the so-called “slow regime” where or larger, the T 1 and T 2 times corresponding to the CT and ST components become distinct. In the case of spin-3/2 nuclei such as 23 Na, the two relaxation times are given by Equations (4)–(7) [ 17 , 23 , 25 , 26 ]: …”

Metal Binding to Sodium Heparin Monitored by Quadrupolar NMR

“…When increases due to an increase in ω 0 and/or τ c , the two T 1 relaxation times decrease until they reach their minimum values and then monotonously increase afterward. The T 2 relaxation time of the central transition follows a similar trend; however, the satellite transition exhibits a monotonous decrease with [ 17 , 25 , 26 , 27 ]. With further increase in τ c when (ω Q is the quadrupolar coupling constant in angular frequency units), the system enters the so-called “ultraslow regime,” and its relaxation deviates from Redfield’s theory, which is outside the scope of the current study (see Methods for further description) [ 26 , 28 ].…”

“…When τ c and/or ω 0 increase and the system enters the so-called “slow regime” where or larger, the T 1 and T 2 times corresponding to the CT and ST components become distinct. In the case of spin-3/2 nuclei such as 23 Na, the two relaxation times are given by Equations (4)–(7) [ 17 , 23 , 25 , 26 ]: …”

Experimental Evidence of Counterion Affinity in Alginates: The Case of Nongelling Ion Mg2+

“…Although outside the extreme narrowing conditions the relaxation of 23 Na is biexponential, − in the present case the spin−lattice relaxation curve is fitted very well using an averaged relaxation time value ( T 1 ). According to the “two-state, all-or-none” model, the sodium ions exchange between a free ( X f ) and a bound ( X b ) situation and, when the exchange between the sites is fast on the NMR time scale, eq holds: ,− R 1 obs = R 1 f X f + R 1 b X b = R 1 f ( 1 − X b ) + R 1 b X b where R 1obs (= 1/ T 1 ) is the experimentally observed relaxation rate and R 1f and R 1b are the relaxation rates of “free” and “bound” sodium ions, respectively. The former represents the sodium ions in a free state (i.e., in the bulk) where the electric field gradient experienced by the nucleus is supposed not to be affected by the presence of the polyelectrolyte.…”

The EB-DNA Liquid Crystalline Complex with High Concentration of Mg2+

“…The NMR spectrum of 23 Na nucleus exhibits a multiple of 2I ¼ 3 equally spaced peaks. 34 The separation between adjacent lines, the quadrupolar splitting (Á), depends on several factors, such as the quadrupolar interaction strength and the alignments of the DNA chains, etc. In the solutions, the splitting of 23 Na nucleus in different sites is different and the 23 Na nuclei are rapidly exchanged in different anisotropic magnetic environments.…”

“…The analysis of the observed 23 Na NMR splitting is commonly done by means of a two-site model according to that the counter ions are exchanged between a ''bound'' state in the immediate vicinity of DNA chains and a ''free'' state where the electric field gradient at the sodium nucleus is essentially unaffected. 34 In the ''free'' state, the splitting Á averages to zero due to the fast reorientation of molecules. When the exchange of the 23 Na nuclei is fast on the NMR time scale, the observed splitting Á is the number averages of the splitting in the two states, as is given 20…”

Metal Binding to Sodium Heparin Monitored by Quadrupolar NMR

“…When increases due to an increase in ω 0 and/or τ c , the two T 1 relaxation times decrease until they reach their minimum values and then monotonously increase afterward. The T 2 relaxation time of the central transition follows a similar trend; however, the satellite transition exhibits a monotonous decrease with [ 17 , 25 , 26 , 27 ]. With further increase in τ c when (ω Q is the quadrupolar coupling constant in angular frequency units), the system enters the so-called “ultraslow regime,” and its relaxation deviates from Redfield’s theory, which is outside the scope of the current study (see Methods for further description) [ 26 , 28 ].…”

“…When τ c and/or ω 0 increase and the system enters the so-called “slow regime” where or larger, the T 1 and T 2 times corresponding to the CT and ST components become distinct. In the case of spin-3/2 nuclei such as 23 Na, the two relaxation times are given by Equations (4)–(7) [ 17 , 23 , 25 , 26 ]: …”

Experimental Evidence of Counterion Affinity in Alginates: The Case of Nongelling Ion Mg2+

“…Although outside the extreme narrowing conditions the relaxation of 23 Na is biexponential, − in the present case the spin−lattice relaxation curve is fitted very well using an averaged relaxation time value ( T 1 ). According to the “two-state, all-or-none” model, the sodium ions exchange between a free ( X f ) and a bound ( X b ) situation and, when the exchange between the sites is fast on the NMR time scale, eq holds: ,− R 1 obs = R 1 f X f + R 1 b X b = R 1 f ( 1 − X b ) + R 1 b X b where R 1obs (= 1/ T 1 ) is the experimentally observed relaxation rate and R 1f and R 1b are the relaxation rates of “free” and “bound” sodium ions, respectively. The former represents the sodium ions in a free state (i.e., in the bulk) where the electric field gradient experienced by the nucleus is supposed not to be affected by the presence of the polyelectrolyte.…”

The EB-DNA Liquid Crystalline Complex with High Concentration of Mg2+

“…The NMR spectrum of 23 Na nucleus exhibits a multiple of 2I ¼ 3 equally spaced peaks. 34 The separation between adjacent lines, the quadrupolar splitting (Á), depends on several factors, such as the quadrupolar interaction strength and the alignments of the DNA chains, etc. In the solutions, the splitting of 23 Na nucleus in different sites is different and the 23 Na nuclei are rapidly exchanged in different anisotropic magnetic environments.…”

“…The analysis of the observed 23 Na NMR splitting is commonly done by means of a two-site model according to that the counter ions are exchanged between a ''bound'' state in the immediate vicinity of DNA chains and a ''free'' state where the electric field gradient at the sodium nucleus is essentially unaffected. 34 In the ''free'' state, the splitting Á averages to zero due to the fast reorientation of molecules. When the exchange of the 23 Na nuclei is fast on the NMR time scale, the observed splitting Á is the number averages of the splitting in the two states, as is given 20…”

Metal Binding to Sodium Heparin Monitored by Quadrupolar NMR

“…When increases due to an increase in ω 0 and/or τ c , the two T 1 relaxation times decrease until they reach their minimum values and then monotonously increase afterward. The T 2 relaxation time of the central transition follows a similar trend; however, the satellite transition exhibits a monotonous decrease with [ 17 , 25 , 26 , 27 ]. With further increase in τ c when (ω Q is the quadrupolar coupling constant in angular frequency units), the system enters the so-called “ultraslow regime,” and its relaxation deviates from Redfield’s theory, which is outside the scope of the current study (see Methods for further description) [ 26 , 28 ].…”

“…When τ c and/or ω 0 increase and the system enters the so-called “slow regime” where or larger, the T 1 and T 2 times corresponding to the CT and ST components become distinct. In the case of spin-3/2 nuclei such as 23 Na, the two relaxation times are given by Equations (4)–(7) [ 17 , 23 , 25 , 26 ]: …”

Experimental Evidence of Counterion Affinity in Alginates: The Case of Nongelling Ion Mg2+

“…Although outside the extreme narrowing conditions the relaxation of 23 Na is biexponential, − in the present case the spin−lattice relaxation curve is fitted very well using an averaged relaxation time value ( T 1 ). According to the “two-state, all-or-none” model, the sodium ions exchange between a free ( X f ) and a bound ( X b ) situation and, when the exchange between the sites is fast on the NMR time scale, eq holds: ,− R 1 obs = R 1 f X f + R 1 b X b = R 1 f ( 1 − X b ) + R 1 b X b where R 1obs (= 1/ T 1 ) is the experimentally observed relaxation rate and R 1f and R 1b are the relaxation rates of “free” and “bound” sodium ions, respectively. The former represents the sodium ions in a free state (i.e., in the bulk) where the electric field gradient experienced by the nucleus is supposed not to be affected by the presence of the polyelectrolyte.…”

The EB-DNA Liquid Crystalline Complex with High Concentration of Mg2+

“…The NMR spectrum of 23 Na nucleus exhibits a multiple of 2I ¼ 3 equally spaced peaks. 34 The separation between adjacent lines, the quadrupolar splitting (Á), depends on several factors, such as the quadrupolar interaction strength and the alignments of the DNA chains, etc. In the solutions, the splitting of 23 Na nucleus in different sites is different and the 23 Na nuclei are rapidly exchanged in different anisotropic magnetic environments.…”

“…The analysis of the observed 23 Na NMR splitting is commonly done by means of a two-site model according to that the counter ions are exchanged between a ''bound'' state in the immediate vicinity of DNA chains and a ''free'' state where the electric field gradient at the sodium nucleus is essentially unaffected. 34 In the ''free'' state, the splitting Á averages to zero due to the fast reorientation of molecules. When the exchange of the 23 Na nuclei is fast on the NMR time scale, the observed splitting Á is the number averages of the splitting in the two states, as is given 20…”