Glycerol facilitates the disaggregation of recombinant adeno-associated virus serotype 2 on mica surface

Preparation of distributed virus on a solid substrate is a prerequisite for investigation of the properties and individualism of virus, while many previous studies showed that virus has a tendency to aggregate on solid substrates. In this communication, we report a novel approach by which well-separated recombinant adeno-associated virus serotype 2 (rAAV2) could be prepared on bare mica surface. The key technique in this approach is the addition of less than 3% (v/v) glycerol into the virus solution and subsequently deposition onto mica surface for the sample preparation. The possible mechanisms are also briefly discussed.

Nanomanipulation of extended single-DNA molecules on modified mica surfaces using the atomic force microscopy

The technique of nanometer scale manipulation is very important in constructing nano-structures and nano-devices. By using atomic force microscope, three kinds of controllable manipulation on single-DNA molecules were introduced in the paper. DNA molecules deposited and extended on modified mica surface were first imaged by tapping mode, then cutting, bending, and pushing were respectively performed on single-DNA molecules. The results of the manipulation depend on the interaction between tip and DNA as well as between substrate and DNA.

Purification of the recombinant hepatitis B virus core antigen (rHBcAg) produced in the yeast Saccharomyces cerevisiae and comparative observation of its particles by transmission electron microscopy (TEM) and atomic force microscopy (AFM)

Hepatitis B virus core antigen (HBcAg) gene (C gene) was expressed in Saccharomyces cerevisiae and the products (rHBcAg or core particles) were purified from a crude lysate of the yeast by three steps: Sephrose CL-4B chromatography, Sucrose step-gradient ultracentrifugation and CsCl-isopycnic ultracentrifugation. It has been observed that HBcAg was synthesized in yeast cells as a particle consisting of polypeptides with a molecular weight of 21.5 kDa (p21.5). Results of ELISA test and density analysis of CsCl-isopycnic ultracentrifugation indicated that the purified products (rHBcAg particles) with HBcAg antigenicity mainly located at the densities of 1.27 and 1.40 g ml(-1), respectively. Observation and analysis of the purified rHBcAg products by TEM indicated that rHBcAg peptides could mainly self-assemble into two size classes of core particles. The larger particles were approximately 30.1 nm and the smaller were approximately 21.5 nm in mean diameter. Further observation and analysis of the same rHBcAg (core) particles by AFM also indicated that rHBcAg (core) particles were similar to the native HBcAg (core) particles from infected human hepatocytes and mainly composed of two size classes of partides core. The larger particles were approximately 31.3 nm and the smaller were approximately 22.5 nm in mean diameter which was similar to the results obtained by TEM. All results from both TEM and AFM suggested that core particles (capsids) produced in S. cerevisiae possessed dimorphism.