Quartz crystal microbalance, a valuable tool for elucidation of interactions between apoB-100 peptides and extracellular matrix components

Atherosclerosis has received wide attention as a primary cause of premature death in developed countries. The retention of low-density lipoprotein (LDL) particles in the intima, the inner layer of the capillaries, has been imputed as the main cause of the development of atherosclerotic plaques. The entrapment of LDL is mainly due to the specific interaction between the lysine-rich site on apolipoprotein B-100 (apoB-100), a major apolipoprotein of LDL, and extracellular matrix (ECM) components such as collagen, proteoglycans, and glycosaminoglycans (GAGs). Although valuable techniques already exist for studies on apoB-100 and ECM interactions, there is continued need for miniaturized tools that can complement the tools already available and even provide totally new data. This work explores the applicability of the quartz crystal microbalance (QCM) for interaction studies between apoB-100 peptide fragments and various components of the ECM. Two positive peptide fragments, PP and PP₂, and two components of the ECM, collagen I and a selected GAG, chondroitin 6-sulfate (C6S), were immobilized on polystyrene and carboxyl sensor chips. C6S was injected as analyte for PP- and PP₂-coated surfaces, while PP was the analyte for collagen I and C₆S surfaces. The estimated dissociation constant (K _D) indicates that the interactions occur via the positive residues, lysine and arginine, of apoB-100. The continuous-flow QCM system employed in this study is shown to be an excellent tool for the elucidation of interactions between these types of biomolecules.