MOLECULAR BASIS OF RED BLOOD CELL MEMBRANE DEFORMABILITY

Abstract

Blood is one of the most important organs of the body and performs a number of vital physiological functions. The most important function of the blood is the respiratory gaseous transport, which is performed by red blood cells. It is important for medical treatment and health care to investigate the molecular basis of the properties of the red cell in circulation, which are dominantly determined by its membrane. However, because of the limitation of tools and methods, the direct molecular information of the red cell membrane has been rarely reported. The innovation of atomic force microscopy (AFM) creates the possibility to directly image the red cell membrane structure in nanometer level. In the present work, four kinds of human reel cell membranes (the original red cell membrane, the lysised red cell membrane, the red cell ghost, and the red cell membrane skeleton) were systemically studied by AFM. The reel cell membranes were imaged in molecular level from both the external surface and the cytoplasmic side and by both of the contact and non-contact mode AFM. The intact red cell membrane skeleton was also successfully imaged by non-contact AFM for the first time. The results show that in situ, the red cell membrane skeleton network is a dense, complex, three-dimensional network of filaments that is difficult to analyze in detail. Rapidly frozen reel cell ghosts in liquid nitrogen will lead to the dehydration of the red cell membrane. The membrane bilayer will sink inward at places where there is no support by the membrane skeleton and tightly attach to the skeleton. Therefore, it is possible to get the intact red cell skeleton pattern in situ from the external surface of the red cell membrane. In large scan range (larger than the diameter of the red cell), the AFM images of red cell membranes can show the overall morphology of the red cells, however the detailed structural information on the surface of the red cell membrane couldn't be observed. Only images of AFM and other sophisticated instruments obtained from the small scan range (smaller than 2.5 lm) can provide the detailed structural information of the red cell membrane surface. Although AFM is powerful in the field of material science and engineering, it is possible to produce artifacts from many resources such as probe geometry, non-ideal performance of pizeoelectric ceramics, ambient vibration and data manipulations. The present study demonstrated a general limitation of the AFM. The lower part of the specimen is broadened due to the interaction between tip and sample. Only the upper part images are authentic. Mathematica is a fully integrated environment for technical computing. The present study demonstrates that by applying its powerful graphic functions, the quality of AFM images could be sharply improved and the images could be analyzed thoroughly. Therefore, it is very useful tool in AFM image treatment.