Yukinao Noda

Effect of hydration on the thermal denaturation of lysozyme as measured by differential scanning calorimetry.

The thermal denaturation of lysozymc in aqueous alcohol solution has been investigated by differential scanning calorimetry. The alcohols employed were methanol, ethanol, isomeric propyl alcohols and butyl alcohols as monohydric alcohols, and ethylene glycol and glycerol as polyhydric alcohols. In monohydric alcohols, the temperature of denaturation, Td, of lysozyme decreased linearly with increasing alcohol concentration, which became pronounced with an increasing in the hydrophobic character. The enthalpy of denaturation, ΔHd, of lysozyme showed a complex dependence on the solvent composition; the ΔHd first increased with increasing alcohol concentration and then started decreasing at different concentrations for each alcohol. The branching of the alkyl chain decreased the destabilizing effect of the alcohol on the native conformation of the protein. In polyhydric alcohols, both Td and ΔHd increased with increasing alcohol concentration. The polyhydric alcohols stabilized the native conformation of the ...

A simple procedure for the extraction of the native chromophore of visual pigments : The formaldehyde method

The chromophore of visual pigments was efficiently extracted in its original isomeric conformation by dichloromethane/hexane in the presence of excess formaldehyde. This new method of extraction (the formaldehyde method) in combination with HPLC is useful for the determination of the chromophore composition of visual pigments. The chromophore isolated by this method is biologically active and can be used for regeneration experiments.

Thermal stability of alkylated and hydroxyalkylated lysozymes

Abstract Five derivatives of lysozyme which were modified in four of the original six lysine residues were prepared by reductive alkylation with three aliphatic aldehydes of different chain lengths and two hydroxyaldehydes of different hydroxyl-group contents. The thermal stability of these derivatives was investigated by DSC. The alkylated derivatives were less stable than unmodified lysozyme, depending on the size of the introduced alkyl groups. However, there was no significant difference in the thermal stability among unmodified and two hydroxylated lysozymes. The change in the thermal stability upon lysine modification of lysozyme is remarkably dependent on the qualitative factors of the entering substituents, and on other factors such as steric hindrance.