Polysaccharide–polynucleotide complexes (15): thermal stability of schizophyllan (SPG)/poly(C) triple strands is controllable by α-amino acid modification
✍ Scribed by Munenori Numata; Takahiro Matsumoto; Mariko Umeda; Kazuya Koumoto; Kazuo Sakurai; Seiji Shinkai
- Publisher
- Elsevier Science
- Year
- 2003
- Tongue
- English
- Weight
- 131 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0045-2068
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✦ Synopsis
Schizophyllan (SPG), a beta-1,3-glucan polysaccharide which is known to form macromolecular complexes with certain polynucleotides, was modified by a reductive amination method with alpha-amino acids (Arg, Lys, and Ser). The thermal stability of the complexes as estimated by T(m) was enhanced in SPG-Arg and SPG-Lys conjugates which have pI values higher than the pH of the medium (8.0). The T(m) shift increased with the increase in the percentage of alpha-amino acid introduced and the highest T(m) values attained were 64 degrees C for SPG-Arg conjugate and 62 degrees C for SPG-Lys conjugate, which are higher by 13 and 11 degrees C, respectively, than those of the unmodified SPG+poly(C) complex. In the SPG-Ser conjugate with a pI lower than the medium pH (8.0), the T(m) values decreased with an increase in the percentage of Ser. Formation of the macromolecular complex was no longer detected above 13.2% Ser. The findings indicate that the T(m) values are easily controllable by the type and percentage of the introduced alpha-amino acids. We believe, therefore, that the present conjugates, consisting of naturally originated SPG and alpha-amino acids, provide an important lead for developing nontoxic artificial vectors and to control the affinity with polynucleotides in response to medium pH and temperature.