The Drosophila circadian clock: what we know and what we don't know.

Circadian rhythms are regulated by endogenous body clocks, which are formed by rhythmic cycles of clock gene expression. Almost all reviews of the Drosophila circadian clock state that the intracellular oscillator is based on a simple negative feedback loop. However, not many 'simple' feedback loops in biology last for 24 h. Instead, the Drosophila clock is a series of precisely timed steps that are deliberately slow. In this paper, I will discuss the current model for how the Drosophila clock is regulated, and ask what questions remain to be answered.     

Biological AFM: where we come from--where we are--where we may go

Biological atomic force microscopy (AFM) is a fast growing and advancing field. This review's objective is to overview the state of the art and to retrace achievements of biological AFM as presented by past and present research, and wishes to give a (subjective) outlook where AFM may go in the upcoming years. The following areas of interest are discussed: High-resolution imaging, cell imaging, single molecule force spectroscopy, cell mechanical measurements, combined AFM instrumentation, and AFM instrumentation. Of all these topics, particular representative examples are shown, each of them standing for a variety of achievements by many research groups.