Effects of protein and phosphate buffer concentrations on thermal denaturation of lysozyme analyzed by isoconversional method

Abstract

Thermal denaturation of lysozymes was studied as a function of protein concentration, phosphate buffer concentration, and scan rate using differential scanning calorimetry (DSC), which was then analyzed by the isoconversional method. The results showed that lysozyme thermal denaturation was only slightly affected by the protein concentration and scan rate. When the protein concentration and scan rate increased, the denaturation temperature (Tm) also increased accordingly. On the contrary, the Tm decreased with the increase of phosphate buffer concentration. The denaturation process of lysozymes was accelatated and the thermal stability was reduced with the increase of phosphate concentration. One part of degeneration process was not reversible where the aggregation occurred. The other part was reversible. The apparent activation energy (Ea) was computed by the isoconversional method. It decreased with the increase of the conversion ratio (α). The observed denaturation process could not be described by a simple reaction mechanism. It was not a process involving 2 standard reversible states, but a multi-step process. The new opportunities for investigating the kinetics process of protein denaturation can be supplied by this novel isoconversional method.

Physical Processes

“…None of these dependencies has shown a tendency to plateau at small values of α. On the other hand, decreasing E α dependencies with a well-defined plateau at small α values has been reported [197,198] for the thermal denaturation of the globular protein lysozyme. Also, a plateau in E α followed by a decreasing dependence has been found [199] for thermal denaturation of keratin.…”

Next generation strategy for tuning the thermoresponsive properties of micellar and hydrogel drug delivery vehicles using ionic liquids

“…Typically, tailored formulations using different traditional excipients, including sugars, amino acids, polyols and aqueous buffers such as citrate or PBS are developed to tune the properties and enhance the stability of active ingredients and polymeric delivery vehicles in solution. 16,17 However, these excipients can alter the structural stability of biomolecules, leading to irreversible aggregation and degradation. 17,18 As well, the interactions between the polymer and aqueous solvent may change, influencing the hydrophilic/ hydrophobic balance of the polymer molecules and hence the thermoresponsive properties.…”

“…2,[17][18][19] Furthermore, there remains the hurdle of designing stable drug formulations of extended shelf-life and sustained release. 2,4,[15][16][17][18] Thus, controlling the thermoresponsive properties of delivery vehicles, whilst maintaining solubility and stability in solution, hinders advancements in drug delivery applications. These challenges are largely due to the lack of delivery vehicles developed, few excipients available, and appropriate matrices established to date for injectable and controlled drug delivery.…”

Engineered Design of the E-Helix Structure on Ferritin Nanoparticles

“…DSC was used to characterize protein thermal stability by determining the midpoint temperature of the transition ( T m ) and calorimetric enthalpy (Δ H ). , T m is also known as protein denaturation temperature . Protein with multiple subunits, such as engineered ferritins (F1L3E1, C1, C2, and C5), may experience more than one unfolding event, resulting in multiple T m values, , which is caused by the multiple intermediates formed during the thermal denaturation process.…”