Alternating poly(Arg-Leu) and copolypeptides with Arg-Leu and His-Leu sequences were prepared by condensation of the corresponding p-nitrophenyl dipeptide esters in the presence of 1-hydroxybenzotriazole. Arginine was used without any protection and histidine side chains were protected using r-benzy
Sequential polypeptides containing arginine as histone models: Synthesis and conformational studies
✍ Scribed by Eugenia Panoy-Pomonis; Constantinos Sakarellos; Maria Sakarellos-Daitsiotis
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1986
- Tongue
- English
- Weight
- 896 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The sequential polypeptides (L-Arg-X-Gly),, where X represents amino acid residues Ala, Val, and Leu, were prepared as models of argininerich histones to be used in studying their structure and their interactions with DNA. The polymerization was carried out on the pentachlorophenyl active esters of the appropriate tripeptides, while the toluend-sulfonyl group was used for protecting the arginine guanido group. CD was employed to investigate the conformation of (L-Arg-XGly), polymers in aqueous solutions, at different pH, as well as in trifluoroenthanol and hexafluoroisopropyl alcohol solutions. In aqueous solutions (at pH 7 and 12) the prepared sequential polymers behaved as a random coil. The CD spectra in various trifluoroethanol-water or hexafluoroisopropyl alcohol-water mixtures indicated that the degree of helical conformation of the studied polytripeptides increased in the order of Ala + Val -Leu. The opposite was true for the b-structure. Characteristics of b-turn are excluded from the poly(L-Arg-L-Leu-Gly), which assumed the most pronounced helical conformation. The poly(L-Arg-L-Val-Gly) exerts a significant preference to the p-turn structure compared to that of poly(L-Arg-L-Ala-Gly). Thus the probability for helical, b-structure or p-turn conformations of the polymers was analyzed in relation to the bulkiness and length, and to the special features of the X-residue side chain @-branching). We concluded that the prepared sequential arginine-containing polypeptides are plausible models for histone fractions, f 3 and f+
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Sequential polypeptides (L-Arg-X-Gly), were prepared as synthetic models of arginine-rich histones t o study their structure and their stereospecific interactions with DNA. In our previous work the conformational characteristics of poly(L-Arg-L-Ala-Gly), poly(L-Arg-L-Val-Gly), and poly( L-Arg-L-Leu-