ABSTRACT
Neutron reflection and X-ray reflection have been widely used for studies of adsorption at flat surfaces, both air-liquid and solid-liquid, and have proved to be valuable techniques for providing detailed information about the structure and composition of adsorbed layers (1,2). Because many biological processes occur at interfaces, the possibility of using reflection to study structural and kinetic aspects of model biological systems should be of considerable interest. However, the number of such experiments so far performed is small. The main reasons for this may be that the range of types of surface suitable for exploration is perceived to be limited, especially in relation to interfacial systems of biological interest, and also that the most effective use of neutron reflection is assumed to involve extensive deuterium substitution. Not only is a high level of deuteration not usually an available option in biological molecules but also there is always concern that deuteration may affect the behavior of the system. Although these are reasons for taking care in the choice of system for study, they do not preclude the effective use of either X-ray or neutron reflection and it would be a pity not to take advantage of their excellent sensitivity to structure and composition at interfaces. In this introduction to the two specular reflection techniques we focus particularly on situations in which neutron reflection may be sensitive to nondeuterated biological materials, how to enhance this sensitivity, and some of the possibilities for mimicking interfaces of biological interest. We illustrate these ideas with
experimental work on adsorbed proteins. Other experimental techniques for studying biological interfaces are described elsewhere in this volume and, for reasons of space, we generally avoid direct comparisons with other techniques.
