No abstract

We relate the condition for the elliptic shape of the phase diagram of proteins to the degree of correlation in the fluctuations of the changes of enthalpy and volume at the denaturing-refolding transition. Since this degree cannot be larger than 1, hyperbolically shaped diagrams are not likely to exist. Experiments show that the correlation factor is actually quite low for proteins implying that one-order parameter is not enough to describe the folding-denaturing transition. These findings seem to be the thermodynamic manifestation of the glasslike properties of proteins despite the fact that the transition itself is of first order.

We have investigated thionin in a glycerol/water glass bound to DNA quadruplexes and DNA duplexes with pressure-tuning hole-burning spectroscopy at 2 K. For free thionin as a reference we could identify the two tautomeric structures (imino and amino form) in the inhomogeneous absorption bands. The measurement of local compressibilities from the spectral hole shifts under pressure allowed the assignment of binding modes of thionin to the DNA strands. Thionin binds via external stacking to the dimeric hairpin quadruplex and binds to the monomeric quadruplex only by Coulombic interaction, whereas it intercalates into a linear GCduplex structure. However, differences in the local compressibilities revealed that only the amino form is able to intercalate into the DNA duplex.

No abstract

We demonstrate hole burning on a protein by using an intrinsic aromatic amino acid as a probe. The protein is bovine pancreatic trypsin inhibitor (BPTI), the labeled amino acid is tyrosine. Only one of the four tyrosines could be burned. As an application we present pressure tuning experiments from which the local compressibility around the burned tyrosine probe is determined.