SURFACES COATED WITH PROTEIN LAYERS - A SURFACE FORCE AND ESCA STUDY

In this review article we discuss the types of non-specific forces tha t are of importance for the interactions between proteins and surfaces . Some of these forces are well understood theoretically, and their pr operties investigated in detail. The origin of other types of forces i s less well understood, or even controversial, and here we will recapi tulate the main experimental findings. Most of our knowledge of interf acial forces stems from the use of various surface force techniques. T wo such techniques are described in this article. The typical experime ntal procedure is outlined and attention is drawn to the most common c omplications that we have met during our studies. In this article we h ave chosen to present data that illustrate the presence of some partic ular type of force, that illustrate a particular complication that occ urs when evaluating the experimental findings, or that illustrate the advantage of using electron spectroscopy for chemical analysis (ESCA) in combination with surface force measurements. No system is discussed in detail, and for more detailed information we will refer the reader to the original literature. However, we present an estimate of the am ount of small ions co-adsorbed with the protein calculated from a comb ination of the ESCA and surface force apparatus (SFA) results. This es timate is based on a simple charge balance which requires a knowledge of the adsorbed amount and the diffuse layer charge. The adsorbed amou nt is obtained from ESCA measurements using a quantification method th at utilizes the known chemical composition of the mica surface. The di ffuse layer charge is obtained from the magnitude of the double-layer force measured with a surface force technique. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.