| Popis: |
In order to obtain information about the interaction between base pairs of DNA and amino acid residues containing histone H1, the heats of mixing (Δmix, H) of (adenosine 5'-monophosphate)-(uridine 5'-monophosphate), i.e. AMP-UMP duplex (duplex I), and/or (guanosine 5'-monophosphate)-(cytidine 5'-monophosphate), i.e. GMP-CMP duplex (duplex II), and L-lysine (Lys) and/or L-glutamic acid (Glu) monomer systems were measured at 298.15 ± 0.005 K by means of an automatic compensated flow microcalorimeter equipped with a computer. The heats of interaction (ΔH) for these systems were estimated to be about −58 kJ for duplex I-Lys, −56 kJ for duplex II-Lys, −42 kJ for duplex I-Glu and −29 kJ for duplex II-Glu systems, per mole of amino acid. Furthermore, in order to confirm the Δ H estimated from ΔmixH, abinitio molecular orbital calculation for these systems was carried out using the IMSPACK and GAUSSIAN 80 programs with the STO-3G minimal basis set. The interaction energies (ΔE) obtained were estimated to be about −15.7 kJ mol−1 for duplex I-Lys, −23.7 kJ mol−1 for duplex II-Lys, −8.8 kJ mol−1 for duplex I-Glu and −13.2 kJ mol−1 for duplex II-Glu systems. The signs of ΔH obtained for all systems were in good agreement with those of ΔE, suggesting that amino acid molecules interact with the bases of DNA. However, the absolute values of ΔH and ΔE for each system do not agree. It is suggested that for duplex I and/or II and Lys systems, an electrostatic interaction between the negative charge of the nucleotide phosphate and the positive charge of Lys, and the interaction between the base of the nucleotide and the amino add play an important role in forming duplex-amino acid complex systems. |
