Time resolved calorimetry of photo-induced folding in horse heart cytochrome c at high pH.

The research study seeks to investigate the molar volume and enthalpy changes connected to the early stages of folding in a protein, Ferrocytochrome c (Cc), at high pH values, utilizing a method referred to as time-resolved photoacoustic calorimetry.

Objective and Approach

• This paper centers around the biophysical attributes of protein folding, specifically ferrocytochrome c, a protein prevalent in heart cells. Researchers utilized photoacoustic calorimetry to examine the changes that happen during the initial phases of the folding process.
• The folding process is inspected under high pH conditions, as pH can notably impact the stability of proteins and their folding patterns.

Key Findings

• From the data collected, an overall volume change of 1.3 ± 0.3 mL mol and an enthalpy change of 13 ± 7 kcal mol were found to be occurring after the photodissociation of the unfolded CO bound Cc species in less than about 20 ns.
• The research also noted two additional kinetic phases associated with specific binding events – non-native Histidine (His) binding and Methionine (Met) binding. Specific volume and enthalpy changes were noted for each.

Implication

• The overall findings suggest that the binding of non-native ligands likely occurs from an already collapsed conformation of the protein structure.
• This research could enhance understanding of protein folding processes and their complex thermodynamics, potentially informing the design of medicinal agents as many diseases are associated with protein misfolding or disordered protein conformations.