title: A central composite design to investigate the thermal stabilization of lysozyme.
abstract: OBJECTIVE
  The formulation and processing of protein drugs requires the stabilization of the native, biologically active structure. Our aim was to investigate the thermal stability of a model protein, lysozyme, in the presence of two model excipients, sucrose and hydroxypropyl-beta-cyclodextrin (HP-beta-CD).
  
  
  METHODS
  We used high sensitivity differential scanning calorimetry (HSDSC) in combination with a central composite design (CCD). As indicators of protein thermal stability, the measured responses were the unfolding transition temperature (Tm), the onset temperature of the denaturation (To), and the extrapolated onset temperature (To,e).
  
  
  RESULTS
  A highly significant (F probability <0.001) statistical model resulted from analysis of the data The largest effect was due to pH (over the range 3.2-7.2), and the pH value that maximized Tm was 4.8. Several minor but significant effects were detected that were useful for mechanistic understanding. In particular, the effects of protein concentration and cyclodextrin concentration on Tm and To,e were found to be pH-dependent This was indicative of the partially hydrophilic nature of protein-protein interactions and protein-cyclodextrin interactions, respectively.
  
  
  CONCLUSIONS
  Response surface methodology (RSM) proved efficient for the modeling and optimization of lysozyme thermal stability as well as for the physical understanding of the protein-sugar-cyclodextrin system in aqueous solution.
authors.affiliation: Postgraduate Studies in Pharmaceutical Technology, The School of Pharmacy, University of Bradford, West Yorkshire, UK.
authors.forename: S
authors.initials: S
authors.lastname: Branchu
authors.forename: R T
authors.initials: RT
authors.lastname: Forbes
authors.forename: P
authors.initials: P
authors.lastname: York
authors.forename: H
authors.initials: H
authors.lastname: Nyqvist
mesh_terms: D000073738:2-Hydroxypropyl-beta-cyclodextrin; D000704:Analysis of Variance; D000818:Animals; D002021:Buffers; D002152:Calorimetry, Differential Scanning; D003505:Cyclodextrins / Q000737:chemistry; D005079:Excipients / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009113:Muramidase / Q000032:analysis* / Q000737:chemistry*; D011489:Protein Denaturation; D013395:Sucrose / Q000737:chemistry; D013696:Temperature; D014867:Water / Q000737:chemistry; D047392:beta-Cyclodextrins
chemical_list: D002021:Buffers; D003505:Cyclodextrins; D005079:Excipients; D047392:beta-Cyclodextrins; D014867:Water; D000073738:2-Hydroxypropyl-beta-cyclodextrin; D013395:Sucrose; D009113:Muramidase