Self-association and solubility of peptides. An infrared absorption method for quantitative titration of the extent of self-association in poly(ethylene glycol)-bound peptides
Abstract:The disruption of the sparingly soluble, self-associated species (p-structure) of the polymer-bound, N-protected peptides Boc-~-Ala-Gly-~-lle-( L -A I ~) ~-N HPEG and Boc-(~-Ala),-Gly-~-lle-(L-AI~),-N H PEG [PEG = poly(ethy1ene glycol)] in methylene chloride by increasing amounts of N,N-dimethylformamide or dimethyl sulphoxide has been monitored by following the disappearance of the intense amide I or A i.r. bands of the strongly intermolecularly hydrogen-bonded molecules; this suggests the use of this method … Show more
“…The large increase in the solution viscosity of the PDLLA(A−T)33.3K complex relative to the PDLLA−A and PDLLA−T solutions was attributed to the formation of a supramolecular structure of CMHB-terminated star polymers in solution. The slightly higher η o of the PDLLA−T solution relative to the PDLLA−A solution was consistent with the more favorable self-association of thymine ( K a(T - T ) = 3.5 M -1 , K a(A - A) = 2.4 M -1 ). , It is well-known that N , N -dimethylformamide (DMF) disrupts hydrogen bonding. , We observed a significant decrease in the solution viscosity of the PDLLA(A−T)33.3K 1:1 complex in a 1:1 (v/v) mixture of CHCl 3 and DMF, and this was attributed to a disruption of the hydrogen-bonding interactions between complementary PDLLA−A and PDLLA−T. 6 Solution viscosities of PDLLA−A, PDLLA−T, and PDLLA(A−T)33.3K ( M n = 33300 g/mol) in CHCl 3 and CHCl 3 /DMF (50:50) at 25 °C and 10 wt % concentration.…”
Section: Resultssupporting
confidence: 81%
“…52,53 It is wellknown that N,N-dimethylformamide (DMF) disrupts hydrogen bonding. 54,55 We observed a significant decrease in the solution viscosity of the PDLLA(A-T)33.3K 1:1 complex in a 1:1 (v/ v) mixture of CHCl 3 and DMF, and this was attributed to a disruption of the hydrogen-bonding interactions between complementary PDLLA-A and PDLLA-T.…”
A new family of associating polymers based on four-arm, star-shaped poly(D,L-lactide) (PDLLA) containing peripheral complementary hydrogen-bonding sites is described. Hydroxy-terminated, four-arm, star-shaped PDLLAs of controlled molar mass were functionalized with complementary DNA base pairs, adenine (A) and thymine (T), to obtain PDLLA-A and PDLLA-T, respectively. 1H NMR spectroscopy confirmed quantitative functionalization and the subsequent formation of PDLLA-A and PDLLA-T hydrogen-bonded complexes. Job's analysis revealed a 1:1 optimal stoichiometry for the hydrogen-bonded complexes, and the association constant (Ka) that was determined using the 1H NMR-based Benesi-Hildebrand treatment was 84 M(-1) for the low molar mass complementary polymers. Furthermore, the PDLLA-based hydrogen-bonded complexes exhibited higher solution viscosities compared to the corresponding non-hydrogen-bonded precursors, which further confirmed strong complementary multiple-hydrogen-bonding associations between the star-shaped polymers with terminal adenine and thymine groups. Moreover, variable-temperature 1H NMR studies demonstrated the thermoreversibility of the hydrogen-bonded PDLLA-based complexes in solution.
“…The large increase in the solution viscosity of the PDLLA(A−T)33.3K complex relative to the PDLLA−A and PDLLA−T solutions was attributed to the formation of a supramolecular structure of CMHB-terminated star polymers in solution. The slightly higher η o of the PDLLA−T solution relative to the PDLLA−A solution was consistent with the more favorable self-association of thymine ( K a(T - T ) = 3.5 M -1 , K a(A - A) = 2.4 M -1 ). , It is well-known that N , N -dimethylformamide (DMF) disrupts hydrogen bonding. , We observed a significant decrease in the solution viscosity of the PDLLA(A−T)33.3K 1:1 complex in a 1:1 (v/v) mixture of CHCl 3 and DMF, and this was attributed to a disruption of the hydrogen-bonding interactions between complementary PDLLA−A and PDLLA−T. 6 Solution viscosities of PDLLA−A, PDLLA−T, and PDLLA(A−T)33.3K ( M n = 33300 g/mol) in CHCl 3 and CHCl 3 /DMF (50:50) at 25 °C and 10 wt % concentration.…”
Section: Resultssupporting
confidence: 81%
“…52,53 It is wellknown that N,N-dimethylformamide (DMF) disrupts hydrogen bonding. 54,55 We observed a significant decrease in the solution viscosity of the PDLLA(A-T)33.3K 1:1 complex in a 1:1 (v/ v) mixture of CHCl 3 and DMF, and this was attributed to a disruption of the hydrogen-bonding interactions between complementary PDLLA-A and PDLLA-T.…”
A new family of associating polymers based on four-arm, star-shaped poly(D,L-lactide) (PDLLA) containing peripheral complementary hydrogen-bonding sites is described. Hydroxy-terminated, four-arm, star-shaped PDLLAs of controlled molar mass were functionalized with complementary DNA base pairs, adenine (A) and thymine (T), to obtain PDLLA-A and PDLLA-T, respectively. 1H NMR spectroscopy confirmed quantitative functionalization and the subsequent formation of PDLLA-A and PDLLA-T hydrogen-bonded complexes. Job's analysis revealed a 1:1 optimal stoichiometry for the hydrogen-bonded complexes, and the association constant (Ka) that was determined using the 1H NMR-based Benesi-Hildebrand treatment was 84 M(-1) for the low molar mass complementary polymers. Furthermore, the PDLLA-based hydrogen-bonded complexes exhibited higher solution viscosities compared to the corresponding non-hydrogen-bonded precursors, which further confirmed strong complementary multiple-hydrogen-bonding associations between the star-shaped polymers with terminal adenine and thymine groups. Moreover, variable-temperature 1H NMR studies demonstrated the thermoreversibility of the hydrogen-bonded PDLLA-based complexes in solution.
SynopsisA newly designed host-guest approach is introduced as a experimental tool to explore the relationship between the sequence of peptides and their secondary structure. From the CD spectra of the host-guest peptides studied, a tentative scale for the a-helix potential in 2,Z.Z-trifluoroethanol of guest amino acids is delineated. The conformational preferences are also examined in &structure supporting media (solid state, CH,Cl,, CH,OH, H20) using ir-absorption and CD techniques. Scales for the &forming tendency of guest amino acid residues in the different media are delineated. It is shown that the preferred conformation of the host-guest peptides is a function of the medium, the chain length, and the protecting groups. Given the fact that conformational effects are important in peptide synthesis, the tentative scales may serve as a guideline to predict secondary structures of side-chain-protected or -deprotected peptides in a given solvent, complementing the well-known empirical conformational prediction parameters.
SynopsisSelf-association of Na-protected peptides related to Cterminal sequences of substance P in methylene chloride was disrupted by adding increasing amounts of various polar organic solvents. This process was monitored by the disappearance of the amide I C=O stretching band (1630 cm-I ) of strongly intermolecularly H-bonded molecules in the irabsorption spectra. The effects induced by mainchain length, incorporation at position 9 of a residue promoting folding (a-aminoisobutyric acid), the nature of solvent, and peptide concentration were established. A corollary IH-nmr investigation provided detailed information on the NH protons involved in the self-association process as Hbonding donors. The increasing propensity to aggregate exhibited by these peptides is paralleled by a decrease in their solubility. The impact of these results on the synthesis of substance P short sequences is briefly outlined.'This is part 136 of the Linear Oligopeptides series. For part 135, see Bismara,
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