Polysaccharide - Polynucleotide complexes. Part 32. Structural analysis of the Curdlan/poly(cytidylic acid) complex with semiempirical molecular orbital calculations

Kentaro Miyoshi, Kazuya Uezu, Kazuo Sakurai, Seiji Shinkai

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Natural Curdlan adopts a right-handed 61 triple helix, in which the constituting glucan chains are underpinned with each other by the intermolecular hydrogen bonds. Curdlan can form a stoichiometric complex with polynucleotides [e.g., poly(cytidylic acid), poly(C)]. In this paper, we carried out the MOPAC (semiempirical molecular-orbital package) calculation to examine the molecular structure of the Curdlan/poly(C) complex. The calculation exhibited that two types of hydrogen bonds are formed between the Curdlan and the poly-(C); the third nitrogen (N3) in cytosine forms a hydrogen bond with the second OH of one Curdlan chain, and the proton of N4 is interacting with the O2 of another Curdlan chain. In our model, the helix diameter of poly(C) is expanded from 11.0 to 15.3 Å upon complexation. Despite such large conformational changes, the 61 helix structure of poly(C) was maintained even after the complexation. This fact is complementary to the experimental fact that the complexation does not change the band shape of the circular dichroism of poly(C). The chain length dependence of the reaction enthalpy indicated that the complexation becomes thermodynamically more favorable with the chain length increasing. This feature is also consistent with the experimental data.

Original languageEnglish
Pages (from-to)1540-1546
Number of pages7
JournalBiomacromolecules
Volume6
Issue number3
DOIs
Publication statusPublished - May 1 2005

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Biomaterials
  • Polymers and Plastics
  • Materials Chemistry

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