help button home button Biophys. J.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS

Biophysical Journal 63: 303-308 (1992)
© 1992 the Biophysical Society

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Lacapère, J J
Right arrow Articles by Chatenay, D
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Lacapère, J J
Right arrow Articles by Chatenay, D

Atomic force microscopy of three-dimensional membrane protein crystals. Ca-ATPase of sarcoplasmic reticulum.

J J Lacapère, D L Stokes and D Chatenay

(URA 1290 CNRS) Département de Biologie Cellulaire et Moléculaire, CEN Saclay, France.

ABSTRACT

We have observed three-dimensional crystals of the calcium pump from sarcoplasmic reticulum by atomic force microscopy (AFM). From AFM images of dried crystals, both on graphite and mica, we measured steps in the crystal thickness, corresponding to the unit cell spacing normal to the substrate. It is known from transmission electron microscopy that crystal periodicity in the plane of the substrate is destroyed by drying, and it was therefore not surprising that we were unable to observe this periodicity by AFM. Thus, we were motivated to use the AFM on hydrated crystals. In this case, crystal adsorption appeared to be a limiting factor, and our studies indicate that adsorption is controlled by the composition of the medium and by the physical-chemical properties of the substrate. We used scanning electron microscopy to determine the conditions yielding the highest adsorption of crystals, and, under these conditions, we have obtained AFM images of hydrated crystals with a resolution similar to that observed with dried samples (i.e., relatively poor). In the same preparations, we have observed lipid bilayers with a significantly better resolution, indicating that the poor quality of crystal images was not due to instrumental limitations. Rather, we attribute poor images to the intrinsic flexibility of these multilamellar crystals, which apparently allow movement of one layer relative to another in response to shear forces from the AFM tip. We therefore suggest some general guidelines for future studies of membrane proteins with AFM.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1992 by the Biophysical Society.