- Novel antiarrythmic peptides
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Disclosed are novel peptides including antiarrhythmic peptides that have improved stability. Further disclosed are compositions that include such peptides and methods of using the compositions particularly as medicaments.
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- Effect of hydroxide ion on the kinetics of triethylenetetramine displacement of tripeptides from copper(II) complexes
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Triethylenetetramine (trien) reacts rapidly with doubly deprotonated (tripeptido)cuprate(II) complexes, Cu(H-2L)-, to give Cu(trien)2+ and the free tripeptide, where L = GAG, GGA, GAibG, and Aib3 (G, glycyl; A, L-alanyl; Aib, α-aminoisobutyryl). The reactions are first order in each reactant, and the second-order rate constants (M-1 s-1, 25.0°C, μ = 1.0 M) decrease greatly with the number of methyl groups in the second and third residues: 8.4 × 104 (GAG), 7.9 × 104 (GGA), 43 (GAibG), and 0.13 (Aib3). When L is GAG, GGA, and GAibG, the values of the second-order rate constants (for [trien]T and [Cu(H-2L)-]T) increase above p[H+] 9 and reach maximum values at p[H+] 10.7 ± 0.7. The increase occurs because trien and Htrien+ are more reactive than H2trien2+. The rate constants decrease in higher base due to the formation of Cu(H-2L)(OH)2-, which is less reactive than Cu(H-2L)- with trien. Values for the stability constants of the hydroxide adduct, KOH (M-1, 25.0°C, μ = 1.0 M), are 41, 10, and 4 for L = GAG, GAibG, and GGA, respectively. A hydroxide adduct is not observed for the Aib3 complex (KOH -1). The Cu(H-2Aib3)- complex behaves differently because the reaction with trien is more sterically hindered. An acid-assisted H2trien2+ path contributes to the observed rate below p[H+] 10, and the rate begins to increase below p[H+] 9.5. However, a proton-transfer step between H3O+ and Cu(H-2Aib3)- (kH = 2.5 × 106 M-1 s-1) can limit the reaction so that it no longer depends on the [trien]T concentration. Above p[H+] 10, the reaction is first order in both [trien]T and [Cu(H-2Aib3)-], and the rate increases to a plateau at p[H+] 12. At higher p[H+] levels the rate is assisted by OH-, in contrast to the inhibition found for the other tripeptides. A third-order rate constant (0.41 M-2 s-1) is found for the path due to [trien][OH-][Cu(H-2Aib3)-].
- Schwederski, Brigitte E.,Margerum, Dale W.
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p. 3472 - 3476
(2008/10/08)
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- Thermodynamic properties of peptide solutions 3. Partial molar volumes and partial molar heat capacities of some tripeptides in aqueous solution
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Partial molar volumes, V2o, and partial molar heat capacities, Cp,2o, of the tripeptides glycylglycylglycine, glycylglycylalanine, glycylalanylglycine and alanylglycylglycine have been determined in aqueous solution at 25°C. For the three alanyl-containing tripeptides, the data indicate that the tripeptide-water interaction is influenced by the side chain position within the molecule. The results have been rationalized in terms of likely solutesolvent interactions. The V2o and Cp.2o data have also been used to calculate the contribution to these properties of a-CH3 side chain.
- Hedwig, Gavin R.
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p. 383 - 397
(2007/10/02)
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